0001583648-21-000005 | 10-K | XBRL Viewer | Pieris Pharmaceuticals INC

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2020	Mar. 29, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-37471
Entity Registrant Name	PIERIS PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	30-0784346
Entity Address, Address Line One	255 State Street
Entity Address, Address Line Two	9th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Country	US
Entity Address, Postal Zip Code	2109
City Area Code	857
Local Phone Number	246-8998
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	PIRS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 117,421,871
Entity Common Stock, Shares Outstanding		59,718,989
Documents Incorporated by Reference	Certain information required in Part III of this Annual Report on Form 10-K is incorporated from the Registrant’s Proxy Statement for the 2021 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001583648

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 70,436	$ 62,260
Short term investments	0	41,894
Accounts receivable	1,706	6,787
Prepaid expenses and other current assets	3,579	4,072
Total current assets	75,721	115,013
Property and equipment, net	22,046	19,502
Operating lease right-of-use assets	3,934	3,436
Other non-current assets	3,309	3,146
Total assets	105,010	141,097
Current liabilities:
Accounts payable	1,787	5,803
Accrued expenses and other current liabilities	7,731	9,944
Deferred revenues, current portion	12,627	11,256
Total current liabilities	22,145	27,003
Deferred revenue, net of current portion	35,900	47,258
Operating lease liabilities	15,932	15,484
Other long-term liabilities	6	0
Total liabilities	73,983	89,745
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized and 14,429 and 11,429 shares issued and outstanding at December 31, 2020 and 2019, respectively	0	0
Common stock, $0.001 par value per share, 300,000,000 shares authorized and 56,002,815 and 55,212,437 issued and outstanding at December 31, 2020 and 2019, respectively	56	55
Additional paid-in capital	242,672	227,468
Accumulated other comprehensive loss	(295)	(1,995)
Accumulated deficit	(211,406)	(174,176)
Total stockholders’ equity	31,027	51,352
Total liabilities and stockholders’ equity	$ 105,010	$ 141,097

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (shares)	10,000,000	10,000,000
Preferred stock, shares issued (shares)	14,429	11,429
Preferred stock, shares outstanding (shares)	14,429	11,429
Par value of common stock (USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (shares)	300,000,000	300,000,000
Common stock, shares issued (shares)	56,002,815	55,212,437
Common stock, shares outstanding (shares)	56,002,815	55,212,437
Cash and cash equivalents	$ 70,436	$ 62,260
Accumulated deficit	$ (211,406)	$ (174,176)

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Customer revenue	$ 23,911	$ 32,065
Collaboration revenue	5,412	14,214
Total revenue	29,323	46,279
Operating expenses
Research and development	46,531	54,996
General and administrative	16,713	18,440
Total operating expenses	63,244	73,436
Loss from operations	(33,921)	(27,157)
Interest income	511	1,714
Other expense, net	(3,656)	(26)
Loss before income taxes	(37,066)	(25,469)
Income tax provision	164	0
Net loss	(37,230)	(25,469)
Other comprehensive income/(loss) components:
Foreign currency translation	1,630	973
Unrealized gain on available-for-sale securities	70	14
Comprehensive loss	(35,530)	(24,482)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(37,230)	(25,469)
Net loss attributable to common stockholders	$ (37,230)	$ (28,299)
Net loss per share:
Basic and diluted (USD per share)	$ (0.68)	$ (0.56)
Weighted average number of common shares outstanding used in net loss per share attributable to common stockholders
Basic and diluted (shares)	54,481	50,625
Series C Convertible Preferred Stock
Reconciliation of net loss to net loss attributable to common stockholders:
Accretion of Series C convertible preferred stock	$ 0	$ (2,830)

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Convertible preferred shares	Common shares	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment
Balance at beginning of period (shares) at Dec. 31, 2018			3,000	54,151,000
Balance at beginning of period at Dec. 31, 2018	$ 39,935	$ (1,641)		$ 54	$ 189,929	$ (2,982)	$ (147,066)	$ (1,641)
Increase (Decrease) in Stockholders' Equity
Net loss	(25,469)						(25,469)
Foreign currency translation adjustment	973					973
Unrealized gain (loss) on investments	14					14
Stock based compensation expense	5,374				5,374
Issuance of common stock resulting from exercise of stock options (shares)				279,000
Issuance of common stock resulting from exercise of stock options	$ 553				553
Issuance of common stock resulting from purchase of employee stock purchase plan shares (shares)	113,112			113,000
Issuance of common stock resulting from purchase of employee stock purchase plan shares	$ 369				369
Issuance of common stock resulting from exercise of warrants (shares)				176,000
Issuance of common stock resulting from exercise of warrants	246				246
Issuance of common stock (shares)			4,000	5,493,000
Issuance of common stock	30,998			$ 6	30,992
Preferred stock conversion (shares)			5,000	(5,000,000)
Preferred stock conversion (Series B)	0			$ (5)	5
Balance at end of period (shares) at Dec. 31, 2019			11,000	55,212,000
Balance at end of period at Dec. 31, 2019	51,352			$ 55	227,468	(1,995)	(174,176)
Increase (Decrease) in Stockholders' Equity
Net loss	(37,230)						(37,230)
Foreign currency translation adjustment	1,630					1,630
Unrealized gain (loss) on investments	70					70
Stock based compensation expense	5,090				5,090
Issuance of common stock resulting from exercise of stock options (shares)				149,000
Issuance of common stock resulting from exercise of stock options	$ 291				291
Issuance of common stock resulting from purchase of employee stock purchase plan shares (shares)	69,544			70,000
Issuance of common stock resulting from purchase of employee stock purchase plan shares	$ 200				200
Issuance of common stock (shares)				3,571,000
Issuance of common stock	9,624			$ 4	9,620
Preferred stock conversion (shares)			3,000	(3,000,000)
Preferred stock conversion (Series B)	0			$ (3)	3
Balance at end of period (shares) at Dec. 31, 2020			14,000	56,003,000
Balance at end of period at Dec. 31, 2020	$ 31,027			$ 56	$ 242,672	$ (295)	$ (211,406)

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Payments for stock issuance costs	$ 0.4	$ 1.0

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net loss	$ (37,230)	$ (25,469)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	2,311	632
Right-of-use asset amortization	(184)	408
Stock-based compensation	5,090	5,374
Other non-cash transactions	(133)	(69)
Realized investment gain/loss	471	(1,161)
Deferred tax liability	164	0
Foreign currency re-measurement loss	(8)	(61)
Changes in operating assets and liabilities:
Accounts receivable	5,343	(4,055)
Prepaid expenses and other assets	(500)	(679)
Deferred revenue	(14,496)	(28,524)
Accounts payable	(4,354)	1,257
Accrued expenses and other current liabilities	(1,655)	(914)
Lease liabilities	(715)	794
Net cash used in operating activities	(45,896)	(52,467)
Investing activities:
Purchase of property and equipment	(2,726)	(2,462)
Proceeds from maturities of investments	83,437	63,325
Proceeds from sale of investments	0	8,292
Purchase of investments	(41,499)	(59,317)
Net cash provided by investing activities	39,212	9,838
Financing activities:
Proceeds from exercise of options	291	553
Proceeds from employee stock purchase plan	200	369
Proceeds from exercise of warrants	0	246
Issuance of Common and Preferred Stock, net of issuance costs	9,624	30,998
Net cash provided by financing activities	10,115	32,166
Effect of exchange rate change on cash and cash equivalents	4,745	(2,144)
Net increase in cash and cash equivalents	8,176	(12,607)
Cash and cash equivalents at beginning of year	62,260	74,867
Cash and cash equivalents at end of year	70,436	62,260
Supplemental cash flow disclosures:
Accretion of Series C convertible preferred stock	0	2,830
Net unrealized gain on investments	70	0
Property and equipment included in accounts payable	$ 131	$ 1,235

Corporate Information	12 Months Ended
Corporate Information	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Corporate Information	Corporate Information Pieris Pharmaceuticals, Inc., was founded in May 2013, and acquired 100% interest in Pieris Pharmaceuticals GmbH (formerly Pieris AG, a German company which was founded in 2001) in December 2014. Pieris Pharmaceuticals, Inc. and its wholly-owned subsidiaries, hereinafter collectively Pieris, or the Company, is a clinical-stage biopharmaceutical company that discovers and develops Anticalin-based drugs to target validated disease pathways in unique and transformative ways. Pieris' corporate headquarters is located in Boston, Massachusetts and its research facility, as of December 31, 2020, was located in Freising-Weihenstephan, Germany. The Company moved its research facility to Hallbergmoos, Germany in February 2020. Pieris's clinical pipeline includes an inhaled IL-4Rα antagonist Anticalin protein to treat moderate-to-severe asthma and an immuno-oncology, or IO, bispecific targeting 4-1BB and HER2. The Company’s core Anticalin technology and platform was developed in Germany, and the Company has partnership arrangements with several major multi-national pharmaceutical companies. The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, the need for additional capital, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval and reimbursement for any drug product candidate that it may identify and develop, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development of technological innovations by competitors, reliance on third party manufacturers and the ability to transition from pilot-scale production to large-scale manufacturing of products. As of December 31, 2020, cash and cash equivalents were $70.4 million. In March 2021, the Company amended its strategic collaboration agreement with Seagen which resulted in their purchase of $13.0 million of the Company’s common stock (See Note 3). In March 2021, the Company earned a $13.0 million milestone from AstraZeneca related to the initiation of the phase 2a study for PRS-060/AZD1402 and AstraZeneca agreed to purchase $10.0 million of the Company's common stock (See Note 3). The Company’s net loss was $37.2 million and $25.5 million for the years ended December 31, 2020 and 2019, respectively. The Company has incurred net losses since inception and had an accumulated deficit of $211.4 million as of December 31, 2020. Net losses and negative cash flows have had, and will continue to have, an adverse effect on the Company’s stockholders’ equity and working capital. The Company expects to continue to incur operating losses for at least the next several years. The future success of the Company is dependent on its ability to identify and develop its product candidates, expand its corporate infrastructure and ultimately upon its ability to attain profitable operations. The Company has devoted substantially all of its financial resources and efforts to research and development and general and administrative expenses to support such research and development. The Company has several research and development programs underway in varying stages of development and it expects that these programs will continue to require increasing amounts of cash for development, conducting clinical trials, and testing and manufacturing of product material. Cash necessary to fund operations will increase significantly over the next several years as the Company continues to conduct these activities necessary to pursue governmental regulatory approval of clinical-stage programs and other product candidates. The Company plans to raise additional capital to fulfill its operating and capital requirements through public or private equity financings, utilization of its current ATM program, strategic collaborations, licensing arrangements, and/or the achievement of milestones under its collaborative agreements. The funding requirements of the Company’s operating plans, however, are based on estimates that are subject to risks and uncertainties and may change as a result of many factors currently unknown. Although management continues to pursue these funding plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. Until such time as the Company can generate substantial product revenues, if ever, the Company expects to finance its cash needs through a combination of equity offerings, debt financings, strategic partnerships and licensing arrangements. The terms of any future financing may adversely affect the holdings or the rights of the Company’s existing stockholders. The Company believes that its currently available funds will be sufficient to fund the Company’s operations through at least the next twelve months from the issuance of this Annual Report on Form 10-K. The Company's belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding. If the Company is unable to obtain additional funding on acceptable terms when needed, it may be required to defer or limit some or all of its research, development, and/or clinical projects.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation and Use of Estimates

The accompanying consolidated financial statements of Pieris Pharmaceuticals, Inc. and its wholly-owned subsidiaries were prepared in accordance with U.S. GAAP. The consolidated financial statements include the accounts of all subsidiaries. All intercompany balances and transactions have been eliminated.

The preparation of the financial statements in accordance with U.S. GAAP requires management to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and the related disclosures at the date of the financial statements and during the reporting period. Significant estimates are used for, but are not limited to, assumptions used to estimate its ability to continue as a going concern; revenue recognition; deferred tax assets, deferred tax liabilities and valuation allowances; beneficial conversion features; fair value of stock options, preferred stock, and warrants; and various accruals. Management evaluates its estimates on an ongoing basis. Actual results and outcomes could differ materially from management’s estimates, judgments, and assumptions.

Foreign Currency Translation

The financial statements of the Company’s foreign subsidiaries are translated from local currency into reporting currency, which is U.S. dollars, using the current exchange rate at the balance sheet date for assets and liabilities, and the weighted average exchange rate prevailing during the period for revenues and expenses. The functional currency for Pieris’ foreign subsidiaries is considered to be the local currency for each entity and, accordingly, translation adjustments for these subsidiaries are included in accumulated other comprehensive loss within stockholders’ equity.

Realized and unrealized gains and losses resulting from foreign currency transactions denominated in currencies other than the functional currency are reflected as other (expense) income, net in the consolidated statements of operations. Foreign currency gains and losses on available-for-sale investment transactions are recorded to other comprehensive income on the Company's balance sheet per Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 830, Foreign Currency Matters.

Cash, Cash Equivalents and Investments

The Company determines the appropriate classification of its investments at the time of purchase. All liquid investments with original maturities of 90 days or less from the purchase date and for which there is an active market are considered to be cash equivalents. The Company’s investments are comprised of money market, asset backed securities, government treasuries, and corporate bonds that are classified as available-for-sale in accordance with FASB ASC 320, Investments—Debt and Equity Securities. The Company classifies investments available to fund current operations as current assets on its balance sheets.

Available-for-sale investments are recorded at fair value, with unrealized gains or losses included in accumulated other comprehensive loss on the Company’s balance sheets. Realized gains and losses are determined using the specific identification method and are included as a component of other income.

The Company reviews investments for other-than-temporary impairment whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other-than temporary, the Company considers its intent to sell, or whether it is more likely than not that the Company will be required to sell the investment before recovery of the investment’s amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, the severity and the duration of the impairment, and changes in value subsequent to period end.

Concentration of Credit Risk and Off-Balance Sheet Risk

The Company has no financial instruments with off‑balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that subject Pieris to concentrations of credit risk include cash and cash equivalents, investments, and accounts receivable. The Company’s cash, cash equivalents, and investments are held in accounts with financial institutions that management believes are creditworthy. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company

believes minimizes the exposure to concentration of credit risk. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. Accounts receivable primarily consist of amounts due under strategic partnership and other license agreements with major multi-national pharmaceutical companies for which the Company does not obtain collateral.

Fair Value Measurement

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures, or ASC 820, established a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported or disclosed fair value of the financial instruments and is not a measure of the investment credit quality. Fair value measurements are classified and disclosed in one of the following three categories:

•Level 1 inputs are quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date.

•Level 2 utilizes quoted market prices in markets that are not active, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency.

•Level 3 inputs are unobservable inputs for the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Financial instruments measured at fair value on a recurring basis include cash equivalents and investments (Note 5).

An entity may elect to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected will be reported in net loss. The Company did not elect to measure any additional financial instruments or other items at fair value.

Fair Values of Financial Instruments

The fair value of cash, accounts receivable, and accounts payable approximates the carrying value of these financial instruments because of the short-term nature of any maturities. The Company determines the estimated fair values of other financial instruments, using available market information and valuation methodologies, primarily input from independent third party pricing sources.

Accounts Receivable

Accounts receivable are recorded net of allowances for doubtful accounts and represent amounts due from strategic partners. The Company monitors and evaluates collectability of receivables on an ongoing basis and considers whether an allowance for doubtful accounts is necessary. The Company determined that no such reserve is needed as of December 31, 2020 and 2019. Historically, Pieris has not had collectability issues.

Property and Equipment

Property and equipment are recorded at acquisition cost, less accumulated depreciation and impairment. Depreciation on property and equipment is calculated using the straight-line method over the remaining estimated useful lives of the assets. Maintenance and repairs to these assets are charged to expenses as occurred. During the year ended December 31, 2020, the Company added material assets related to the February 2020 move to a new research and development facility in Hallbergmoos, Germany. The Company expanded its presentation of property and equipment to be more descriptive and updated the useful life for one asset category on a prospective basis. The disclosures for property and equipment, net as of December 31, 2019 have

been reclassified to conform with the current period presentation. The estimated useful life of the different groups of property and equipment is as follows:


Asset Classification						Estimated useful life (in years)
Leasehold improvements						shorter of useful life or remaining life of the lease
Laboratory furniture and equipment						8 - 14
Office furniture and equipment						5 - 13
Computer and equipment						3 - 7

Impairment of Long-lived Assets

The Company reviews its long-lived assets to be held and used for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. The Company evaluates the realizability of its long-lived assets based on profitability and cash flow expectations for the related asset. Any write-downs are treated as permanent reductions in the carrying amount of the assets. The Company believes that, as of each of the balance sheets presented, none of the Company’s long-lived assets were impaired.

Revenue Recognition

Pieris has entered into several licensing agreements with collaboration partners for the development of Anticalin therapeutics against a variety of targets. The terms of these agreements provide for the transfer of multiple goods or services which may include: (i) licenses, or options to obtain licenses, to Pieris’s Anticalin technology and/or specific programs and (ii) research and development activities to be performed on behalf of or with a collaborative partner. Payments to Pieris under these agreements may include upfront fees (which include license and option fees), payments for research and development activities, payments based upon the achievement of certain milestones, and royalties on product sales. There are no performance, cancellation, termination or refund provisions in any of the arrangements that could result in material financial consequences to Pieris.

Effective January 1, 2019, the Company adopted ASC 606. The standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The Company elected the modified retrospective approach and applied it to contracts not completed at the date of adoption. Therefore, comparative prior periods have not been adjusted. The reported results for 2019 reflect the application of ASC 606 guidance while the reported results for 2018 were prepared under the guidance of FASB ASC Topic 605, Revenue Recognition, or ASC 605. Furthermore, the Company adopted the contract modification practical expedient set forth in ASC 606 and will reflect the aggregate effect of all modifications that occurred before January 1, 2019 when identifying the satisfied and unsatisfied performance obligations, determining the transaction price and allocating the transaction price to the satisfied and unsatisfied performance obligations. See Note 3 for additional details on these arrangements.

Collaborative Arrangements

The Company considers the nature and contractual terms of an arrangement and assess whether the arrangement involves a joint operating activity pursuant to which it is an active participant and exposed to significant risks and rewards with respect to the arrangement. If the Company is an active participant and exposed to the significant risks and rewards with respect to the arrangement, it accounts for these arrangements pursuant to ASC 808, Collaborative Arrangements, or ASC 808, and applies a systematic and rational approach to recognize revenue. The Company classifies payments received as revenue and payments made as a reduction of revenue in the period in which they are earned.

In November 2018, the FASB issued ASU 2018-18, which makes targeted improvements to U.S. GAAP for collaborative arrangements, including: clarification that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606, Revenue from Contracts with Customers, or ASC 606, when the collaborative arrangement participant is a customer in the context of a unit of account; adding unit-of-account guidance in ASC 808 to align with the guidance in ASC 606; and a requirement that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under ASC 606 is precluded if the collaborative arrangement participant is not a customer. The guidance per ASU 2018-18 was adopted retrospectively to the date of initial application of ASC 606. The Company adopted ASU 2018-18 in the first quarter of 2020. The adoption of this standard did not have a material impact on the Company’s condensed consolidated financial statements; however, revenue recognized under a collaborative arrangement involving a participant that is not a customer (Collaboration revenue) is now

presented separately from Customer revenue. This change has been reflected in the consolidated statement of operations and the 2019 amounts were adjusted to conform to ASC 808 as follows:


	Twelve Months Ended December 31, 2019
	As reported pre-adoption		ASC 808 Adoption Adjustment		As reported post-adoption
Customer revenue	$	43,646	$	(11,581)	$	32,065
Collaboration revenue	2,633		11,581		14,214
Total Revenue	$	46,279	$	—	$	46,279

Revenue from Contracts with Customers

In accordance with ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps: 1) identify the customer contract; 2) identify the contract’s performance obligations; 3) determine the transaction price; 4) allocate the transaction price to the performance obligations; and 5) recognize revenue when or as a performance obligation is satisfied.

The Company evaluates all promised goods and services within a customer contract and determines which of such goods and services are separate performance obligations. This evaluation includes an assessment of whether the good or service is capable of being distinct and whether the good or service is separable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property and the capabilities of the customer to develop the intellectual property on their own or whether the required expertise is readily available.

Licensing arrangements are analyzed to determine whether the promised goods or services, which often include licenses, research and development services and governance committee services, are distinct or whether they must be accounted for as part of a combined performance obligation. If the license is considered not to be distinct, the license would then be combined with other promised goods or services as a combined performance obligation. If the Company is involved in a governance committee, it assesses whether its involvement constitutes a separate performance obligation. When governance committee services are determined to be separate performance obligations, the Company determines the fair value to be allocated to this promised service.

Certain contracts contain optional and additional items, which are considered marketing offers and are accounted for as separate contracts with the customer if such option is elected by the customer, unless the option provides a material right which would not be provided without entering into the contract. An option that is considered a material right is accounted for as a separate performance obligation.

The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. A contract may contain variable consideration, including potential payments for both milestone and research and development services. For certain potential milestone payments, the Company estimates the amount of variable consideration by using the most likely amount method. In making this assessment, the Company evaluates factors such as the clinical, regulatory, commercial and other risks that must be overcome to achieve the milestone. Each reporting period the Company re-evaluates the probability of achievement of such variable consideration and any related constraints. Pieris will include variable consideration, without constraint, in the transaction price to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. For potential research and development service payments, the Company estimates the amount of variable consideration by using the expected value method, including any approved budget updates arising from additional research or development services.

If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price among the performance obligations on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct good or service that forms part of a single performance obligation.

The Company allocates the transaction price based on the estimated standalone selling price of the underlying performance obligations or in the case of certain variable consideration to one or more performance obligations. The Company must develop

assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs to complete the respective performance obligation. Certain variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated to each performance obligation are consistent with the amount the Company would expect to receive for each performance obligation.

When a performance obligation is satisfied, revenue is recognized for the amount of the transaction price, excluding estimates of variable consideration that are constrained, that is allocated to that performance obligation on a relative standalone selling price basis. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement.

For performance obligations consisting of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non- refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license.

Milestones and Royalties

The Company aggregates milestones into four categories (i) research milestones, (ii) development milestones, (iii) commercial milestones and (iv) sales milestones. Research milestones are typically achieved upon reaching certain success criteria as defined in each agreement related to developing an Anticalin protein against the specified target. Development milestones are typically reached when a compound reaches a defined phase of clinical research or passes such phase, or upon gaining regulatory approvals. Commercial milestones are typically achieved when an approved pharmaceutical product reaches the status for commercial sale, including regulatory approval. Sales milestones are certain defined levels of net sales by the licensee, such as when a product first achieves global sales or annual sales of a specified amount.

There is uncertainty that the events to obtain the research and development milestones will be achieved given the nature of clinical development and the stage of the Company’s technology. The Company has thus determined that all research and development milestones will be constrained until it is deemed probable that a significant revenue reversal will not occur. For revenues from research and development milestones, payments will be recognized consistent with the recognition pattern of the performance obligation to which they relate.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Commercial milestones and sales royalties are determined by sales or usage-based thresholds and will be accounted for under the royalty recognition constraint as constrained variable consideration.

Contract Balances

The Company recognizes a contract asset when the Company transfers goods or services to a customer before the customer pays consideration or before payment is due, excluding any amounts presented as a receivable (i.e., accounts receivable). A contract asset is an entity’s right to consideration in exchange for goods or services that the entity has transferred to a customer. The contract liabilities (i.e., deferred revenue) primarily relate to contracts where the Company has received payment but has not yet satisfied the related performance obligations.

In the event of an early termination of a collaboration agreement, any contract liabilities would be recognized in the period in which all Company obligations under the agreement have been fulfilled.

Costs to Obtain and Fulfill a Contract with a Customer

Certain costs to obtain customer contracts, including success-based fees paid to third-party service providers, and costs to fulfill customer contracts are capitalized in accordance with FASB ASC 340, Other Assets and Deferred Costs, or ASC 340. These

costs are amortized to expense on a systemic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. The Company will expense the amortization of costs to obtain customer contracts to general and administrative expense and costs to fulfill customer contracts to research and development expense.

Research and Development

Research and development expenses are charged to the statement of operations as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, facilities costs, pre-clinical and clinical costs, contract services, consulting, depreciation and amortization expense, and other related costs. Costs associated with acquired technology, in the form of upfront fees or milestone payments, are charged to research and development expense as incurred.

Income Taxes

The Company applies ASC Topic 740 Income Taxes, which established financial accounting and reporting requirements for the effects of income taxes that result from the Company’s activities during the current and preceding years. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, and operating losses and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted statutory tax rates expected to apply to taxable income in the jurisdictions and years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Where the Company determines that it is more likely than not that some portion or all of the deferred tax assets will not be realized in the future, the deferred tax assets are reduced by a valuation allowance. The Company records interest related and penalties related to uncertain tax positions as part of income tax expense.

The Tax Cuts and Jobs Act (TCJA) subjects a U.S. shareholder to tax on global-intangible low tax income (GILTI) earned by certain foreign subsidiaries. The Company has made an accounting policy election to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only.

Stock-based Compensation

The Company measures share-based payments in accordance with ASC Topic 718, Stock Compensation. Pieris records its stock-based compensation expense over the requisite service period and records forfeitures as they occur. Determining the appropriate fair value model and related assumptions requires judgment, including estimating share price volatility and expected terms of the awards. For employee options, the fair value measurement date is generally on the date of grant and the related compensation expense is recognized on a straight-line basis over the requisite period of the awards, less expense for actual forfeitures.

The Company uses the Black-Scholes option pricing model to determine the estimated fair value for stock-based awards. Option-pricing models require the input of various subjective assumptions, including the option’s expected life, expected dividend yield, price volatility, risk free interest rate and forfeitures of the underlying stock. Due to the limited operating history of the Company as a public entity and a lack of company specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry, and with historical

share price information sufficient to meet the expected term of the stock-based awards. The Company computes historical volatility data using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

Due to the lack of Company specific historical option activity, the Company has estimated the expected term of its employee stock options using the “simplified” method, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. The expected term for non-employee awards is the remaining contractual term of the option. The risk-free interest rates are based on the U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The Company has never paid, and does not expect to pay dividends in the foreseeable future.

All excess tax benefits and tax deficiencies are recorded as income tax expense or benefit in the Company's statement of operations and comprehensive loss. For the years ended December 31, 2020 and 2019, the Company did not record an income statement benefit for excess tax benefits as a valuation allowance is also required on these amounts.

Leases

In February 2016, the FASB issued ASU No. 2016-2, Leases (Topic 842), or ASC 842. Under the amendments in ASC 842, lessees will be required to recognize (i) a lease liability, which is a lessees obligation to make lease payments arising from a lease, measured on a discounted basis; and (ii) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term for all leases (with the exception of short-term leases) at the commencement date. The Company adopted ASC 842 in the fourth quarter of 2019 using the required modified retrospective approach, effective January 1, 2019.

The Company elected the package of practical expedients permitted under the transition guidance within the new standard expedients which allows the Company to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of its existing leases as of the transition date, and the treatment of initial direct costs. In addition, the Company elected the practical expedient not to apply the recognition requirements in the lease standard to short-term leases (a lease that at commencement date has a lease term of 12 months or less and does not contain a purchase option that it is reasonably certain to exercise) and the practical expedient to not separate lease and non-lease components for all asset classes. Any variable components of lease costs are excluded from lease payments and are recognized in the period incurred.

The Company determines if an arrangement is a lease at inception. The Company’s contracts are determined to contain a lease within the scope of ASC 842 when all of the following criteria based on the specific circumstances of the arrangement are met: (1) there is an identified asset for which there are no substantive substitution rights; (2) the Company has the right to obtain substantially all of the economic benefits from the identified asset; and (3) the Company has the right to direct the use of the identified asset.

At the commencement date, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of future lease payments over the expected lease term. The Company’s lease agreements do not provide an implicit rate. As a result, the Company utilizes an estimated incremental borrowing rate to discount lease payments, which is based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term and based on observable market data points. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or lease incentives received. Operating lease cost is recognized over the expected term on a straight-line basis.

The Company typically only includes an initial lease term in its assessment of a lease agreement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew. The expected lease term includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option.

Assumptions made by the Company at the commencement date are re-evaluated upon occurrence of certain events, including a lease modification. A lease modification results in a separate contract when the modification grants the lessee an additional right of use not included in the original lease and when lease payments increase commensurate with the standalone price for the additional right of use. When a lease modification results in a separate contract, it is accounted for in the same manner as a new lease.

Contingencies

Accruals are recorded for loss contingencies when it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. The Company evaluates, on a quarterly basis, developments in legal proceedings and other matters that could cause an increase or decrease in the amount of the liability that has been accrued previously. Considering facts known at the time of the assessment, the Company determines whether potential losses are considered reasonably possible or probable and whether they are estimable. Based upon this assessment, the Company carries out an evaluation of disclosure requirements and considers possible accruals in the financial statements.

Segment Reporting

Operating segments are identified as components of an enterprise where separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions on how to allocate resources and assess performance. The Company operates as a single segment dedicated to the discovery and development of biotechnological applications and the Company’s chief operating decision maker, or CODM, makes decisions based on the Company as a whole. The Company has determined that its CODM is its Chief Executive Officer.

Earnings per Share

Basic earnings per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average shares outstanding during the period, without consideration for common stock equivalents.

Diluted earnings per share attributable to common stockholders is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share attributable to common stockholders' calculation, preferred stock, stock options, unvested restricted stock, and warrants are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders, as their effect would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share were the same for all periods presented.

Recent Accounting Pronouncements Not Yet Adopted

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements, or ASU 2016-13. ASU 2016-13 significantly changes the impairment model for most financial assets and certain other instruments. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value, and requires the reversal of previously recognized credit losses if fair value increases. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial asset(s) to present the net carrying value at the amount expected to be collected on the financial asset.

Subsequently, in November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, which clarifies codification and corrects unintended application of the guidance. In November 2019, the FASB issued ASU No. 2019-11, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, which clarifies or addresses specific issues about certain aspects of ASU 2016-13. In November 2019 the FASB also issued ASU No. 2019-10, Financial Instruments-Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, which delays the effective date of ASU 2016-13 by three years for certain smaller reporting companies such as the Company. The guidance in ASU 2016-13 is effective for the Company for financial statements issued for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years, with early adoption permitted. The Company is still evaluating the impact of the adoption of this standard.

The Company has considered other recent accounting pronouncements and concluded that they are either not applicable to the business, or that the effect is not expected to be material to the unaudited consolidated financial statements as a result of future adoption.

Revenue

12 Months Ended

Dec. 31, 2020

Revenue from Contract with Customer [Abstract]

Revenue

General

The Company has not generated revenue from product sales. The Company has generated revenue from contracts with customers (option, license and collaboration agreements), which include upfront payments for licenses or options to obtain licenses, payments for research and development services and milestone payments.

During the years ended December 31, 2020 and 2019, respectively, the Company recognized revenue from the following strategic partnerships and other license agreements (in thousands):


	Years Ended December 31,
	2020		2019
AstraZeneca	$	8,308	$	25,828
Seagen	9,702		2,493
Servier	11,313		15,048
Other	—		2,910
Total Revenue	$	29,323	$	46,279

Under the Company´s existing strategic partnerships and other license agreements, the Company could receive the following potential milestone payments (in millions) as of December 31, 2020:


	Research, Development, Regulatory & Commercial Milestones		Sales Milestones
AstraZeneca	$	1,111	$	960
Servier	247		221
Seagen	764		450


Total potential milestone payments	$	2,122	$	1,631

Strategic Partnerships

Seagen

On February 8, 2018, the Company entered into a license and collaboration agreement, or the Seagen Collaboration Agreement, and a non-exclusive Anticalin platform technology license agreement, or the Seagen Platform License, and together with the Seagen Collaboration Agreement, the Seagen Agreements, with Seagen, Inc., or Seagen, pursuant to which the parties will develop multiple targeted bispecific IO treatments for solid tumors and blood cancers.

Under the terms of the Seagen Agreements, the companies will pursue multiple antibody-Anticalin fusion proteins during the research phase. The Seagen Agreements provide Seagen a base option to select up to three programs for further development. Prior to the initiation of a pivotal trial, the Company may opt into global co-development and U.S. commercialization of the second program and share in global costs and profits on an equal basis. Seagen will solely develop, fund and commercialize the other two programs. Seagen may also decide to select additional candidates from the initial research phase for further development in return for the payment to us of additional fees, milestone payments, and royalties

The Seagen Platform License grants Seagen a non-exclusive license to certain intellectual property related to the Anticalin platform technology.

Upon signing the Seagen Agreements, Seagen paid the Company a $30.0 million upfront fee and an additional $4.9 million was estimated to be paid for research and development services as reimbursement to the Company through the end of the research term. In addition, the Company may receive tiered royalties on net sales up to the low double-digits and up to $1.2 billion in total success-based research, development, commercial, and sales milestones payments across the product candidates, depending on the successful development and commercialization of those candidates. If Seagen exercises its option to select additional candidates from the initial research phase for further development, payment to Pieris of additional fees, milestone payments, and royalties would result.

The term of each of the Seagen Agreements ends upon the expiration of all of Seagen's payment obligations under each agreement. The Seagen Collaboration Agreement may be terminated by Seagen on a product-by-product basis for convenience beginning 12 months after its effective date upon 90 days' notice or, for any program where a pivotal study has been initiated, upon 180 days' notice. Any program may be terminated at Seagen's option. If any program is terminated by Seagen after a pre-defined pre-clinical stage, the Company will have full rights to continue such program. If any program is terminated by Seagen prior to such pre-defined pre-clinical stage, the Company will have the right to continue to develop such program, but will be obligated to offer a co-development option to Seagen for such program. The Seagen Collaboration Agreement may also be terminated by Seagen or the Company for an uncured material breach by the other party upon 90 days' notice, subject to extension for an additional 90 days if the material breach relates to diligence obligations and subject, in all cases, to dispute resolution procedures. The Seagen Collaboration Agreement may also be terminated due to the other party’s insolvency and may in certain instances, including for reasons of safety, be terminated on a product-by-product basis. Each party may also

terminate the Seagen Agreements if the other party challenges the validity of any patents licensed under the Seagen Agreements, subject to certain exceptions. The Seagen Platform License will terminate upon termination of the Seagen Collaboration Agreement, whether in its entirety or on a product-by-product basis.

The Company determined that the Seagen Agreements should be combined and evaluated as a single arrangement under ASC 606 as they were executed on the same date. The arrangement with Seagen provides for the transfer of the following goods or services: (i) three candidate research licenses that each consist of a non-exclusive platform technology license, a co-exclusive candidate research license, and research and development services, (ii) research, development and manufacturing services associated with each candidate research license, (iii) participation on various governance committees, and (iv) two antibody target swap options which were assessed as material rights.

Management evaluated all of the promised goods or services within the contract and determined which such goods and services were separate performance obligations. The Company determined that the licenses granted, at arrangement inception, should be combined with the research and development services to be provided for the related antibody target programs as they are not capable of being distinct. A third party would not be able to provide the research and development services due to the specific nature of the intellectual property and knowledge required to perform the services, and Seagen could not benefit from the licenses without the corresponding services. The Company determined that the participation on the various governance committees was distinct as the services could be performed by an outside party.

As a result, management concluded there are six separate performance obligations at the inception of the Seagen Agreements: (i) three combined performance obligations, each comprised of a non-exclusive platform technology license, a co-exclusive candidate research license, and research and development services for the first three approved Seagen antibody target programs, (ii) two performance obligations each comprised of a material right for an antibody target swap option for the first and the second approved Seagen antibody target for no additional consideration, and (iii) one performance obligation comprised of the participation on the various governance committees.

The Company allocated consideration to the performance obligations based on the relative proportion of their standalone selling prices. The Company developed standalone selling prices for licenses by applying a risk adjusted, net present value, estimate of future potential cash flows approach, which included the cost of obtaining research and development services at arm’s length from a third-party provider, as well as internal full-time equivalent costs to support these services. The Company developed the standalone selling price for committee participation by using management’s estimate of the anticipated participation hours multiplied by a market rate for comparable participants.

The transaction price at inception is comprised of fixed consideration of $30.0 million in upfront fees and variable consideration of $4.9 million of estimated research and development services to be reimbursed as research and development occurs through the research term. The $30.0 million upfront fee, which represents the fixed consideration in the transaction price, was allocated to each of the performance obligations based on the relative proportion of their standalone selling prices. The $4.9 million in variable consideration related to the research and development services is allocated specifically to the three target program performance obligations based upon the budgeted services for each program

The amounts allocated to the performance obligations for the three research programs will be recognized on a proportional performance basis through the completion of each respective estimated research term of the individual research programs. The amounts allocated to the material right for the antibody target swap option will be recognized either at the time the material right expires, or if exercised, on a proportional performance basis over the estimated research term for that program. The amounts allocated to the participation on each of the committees will be recognized straight-line over the anticipated research term for all research programs. As of December 31, 2020, there was $20.7 million of aggregate transaction price allocated to remaining performance obligations.

In June 2020, Seagen and the Company entered into amendments to the Seagen Agreements, or together, the First Seagen Amendment. The Seagen Amendment extended the deadline for Seagen to nominate a second and third antibody target. As a result of the Seagen Amendment, which completed the remaining performance obligations under the research term for the first antibody target, the Company recorded $4.2 million of previously deferred revenue for the year ended December 31, 2020. The Company also recorded $5.0 million of milestone revenue in June 2020.

Under the Seagen Agreements, the Company is eligible to receive various research, development, commercial and sales milestones. There is uncertainty that the events to obtain the research and development milestones will be achieved given the nature of clinical development and the stage of the Company’s technology. The Company has thus determined that all research and development milestones will be constrained until it is deemed probable that a significant revenue reversal will not occur.

As of December 31, 2020, there is $5.7 million and $11.8 million of current and non-current deferred revenue, respectively, related to the Seagen Agreements.

On March 24, 2021, the Company announced that Seagen made a strategic equity investment in Pieris, and that the companies had entered into a combination study agreement, or the Combination Study Agreement, to evaluate the safety and efficacy of combining Pieris’ cinrebafusp alfa with Seagen’s tucatinib, a small-molecule tyrosine kinase HER2 inhibitor, for the treatment of gastric cancer patients expressing lower HER2 levels (IHC2+/ISH- & IHC1+) as part of the upcoming phase 2 study to be conducted by Pieris. The companies have also entered into an Amended and Restated License and Collaboration Agreement, or the Second Seagen Amendment, in which their existing immuno-oncology collaboration agreement has been amended relating to joint development and commercial rights for the second program in the alliance.

Specifically, under the Second Seagen Amendment, Pieris’ option to co-develop and co-commercialize the second of three programs in the collaboration has been converted to a co-promotion option in the United States, with Seagen solely responsible for the development and overall commercialization of that program. Pieris will also be entitled to increased royalties from that program in the event that it chooses to exercise the co-promotion option. In connection with the agreements described above, the Company and Seagen entered into a subscription agreement, or the Seagen Subscription Agreement, pursuant to which the Company agreed to issue to Seagen, and Seagen agreed to acquire from the Company, 3,706,174 shares of the Company’s common stock for a total purchase price of $13.0 million, or $3.51 per share, in a private placement transaction pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended. The Seagen Subscription Agreement includes a requirement that the Company file a registration statement to register the resale of the shares issued to Seagen within 60 calendar days of the issuance of the shares.

AstraZeneca

On May 2, 2017, the Company entered into a license and collaboration agreement, or the AstraZeneca Collaboration Agreement, and a non-exclusive Anticalin platform technology license agreement, or AstraZeneca Platform License, and together with the AstraZeneca Collaboration Agreement, the AstraZeneca Agreements with AstraZeneca AB, or AstraZeneca, which became effective on June 10, 2017, following expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976. Under the AstraZeneca Agreements the parties will advance several novel inhaled Anticalin proteins.

In addition to the Company’s lead inhaled drug candidate, PRS-060/AZD1402, or the AstraZeneca Lead Product, the Company and AstraZeneca will also collaborate to progress four additional novel Anticalin proteins against undisclosed targets for respiratory diseases, or the AstraZeneca Collaboration Products, and together with the AstraZeneca Lead Product, the AstraZeneca Products. The Company is responsible for advancing the AstraZeneca Lead Product through its phase 1 study, with the associated costs funded by AstraZeneca. The parties will collaborate thereafter to conduct a phase 2a study in asthma patients, with AstraZeneca continuing to fund development costs. After completion of a phase 2a study, Pieris has the option to co-develop the AstraZeneca Lead Product and also has a separate option to co-commercialize the AstraZeneca Lead Product in the United States. For the AstraZeneca Collaboration Products, the Company will be responsible for the initial discovery of the novel Anticalin proteins, after which AstraZeneca will take the lead on continued development of the AstraZeneca Collaboration Products. The Company has the option to co-develop two of the four AstraZeneca Collaboration Products beginning at a pre-defined preclinical stage and would also have the option to co-commercialize these two programs in the United States, while AstraZeneca will be responsible for development and commercialization of the other programs worldwide.

The term of each of the AstraZeneca Agreements ends upon the expiration of all of AstraZeneca’s payment obligations under such agreement. The AstraZeneca Collaboration Agreement may be terminated by AstraZeneca in its entirety for convenience beginning 12 months after its effective date upon 90 days’ notice or, if the Company has obtained marketing approval for the marketing and sale of a product, upon 180 days’ notice. Each program may be terminated at AstraZeneca’s option; if any program is terminated by AstraZeneca, the Company will have full rights to such program. The AstraZeneca Collaboration Agreement may also be terminated by AstraZeneca or the Company for material breach upon 180 days’ notice of a material breach (or 30 days with respect to payment breach), provided that the applicable party has not cured such breach by the permitted cure period (including an additional 180 days if the breach is not susceptible to cure during the initial 180-day period) and dispute resolution procedures specified in the agreement have been followed. The AstraZeneca Collaboration Agreement may also be terminated due to the other party’s insolvency and may in certain instances be terminated on a product-by-product and/or country-by-country basis. Each party may also terminate an AstraZeneca Agreement if the other party challenges the validity of patents related to certain intellectual property licensed under such AstraZeneca Agreement, subject to certain exceptions for infringement suits, acquisitions and newly-acquired licenses. The AstraZeneca Platform License will terminate upon termination of the AstraZeneca Collaboration Agreement, on a product-by-product and/or country-by-country basis.

At inception, AstraZeneca is granted the following licenses: (i) research and development license for the AstraZeneca Lead Product, (ii) commercial license for the AstraZeneca Lead Product, (iii) individual research licenses for each of the four AstraZeneca Collaboration Products, (iv) individual commercial licenses for each of the four AstraZeneca Collaboration Products, and (v) individual non-exclusive platform technology licenses for the AstraZeneca Lead Product and the four AstraZeneca Collaboration Products. AstraZeneca will be granted individual development licenses for each of the four AstraZeneca Collaboration Products upon completion of the initial discovery of Anticalin proteins.

The collaboration will be managed on an overall basis by a Joint Steering Committee, or JSC, formed by an equal number of representatives from the Company and AstraZeneca. In addition to the JSC, the AstraZeneca Collaboration Agreement also requires each party to designate an alliance manager to facilitate communication and coordination of the parties' activities under the agreement, and further requires participation of both parties on a joint development committee, or JDC, and a commercialization committee. The responsibilities of these committees vary, depending on the stage of development and commercialization of each product.

Under the AstraZeneca Agreements, the Company received an upfront, non-refundable payment of $45.0 million. In addition, the Company will receive payments to conduct a phase 1 clinical study for the AstraZeneca Lead Product. The Company is also eligible to receive research, development, commercial, sales milestone payments, and royalty payments. The Company may receive tiered royalties on sales of potential products commercialized by AstraZeneca and for co-developed products, gross margin share on worldwide sales equal dependent on the Company’s level of committed investment.

Prior to the adoption of ASC 606, the budgeted research and development services for the AstraZeneca Lead Product increased and were approved by the JSC. The increases included additional phase 1 services as well as the addition of certain phase 2a services. The Company determined that these increases were contract modifications. Upon the adoption of ASC 606, the Company reflected the aggregate effects of these modifications as of the last modification date.

The Company determined that the AstraZeneca Agreements should be combined and evaluated as a single arrangement under ASC 606 as they were executed on the same date. The arrangement with AstraZeneca, including the impact of any modifications, provides for the transfer of the following goods and services: (i) five non-exclusive platform technology licenses, (ii) research and development license for the AstraZeneca Lead Product, (iii) commercial license for the AstraZeneca Lead Product, (iv) development and manufacturing services for the AstraZeneca Lead Product (or the phase 1 services), (v) technology transfer services for the AstraZeneca Lead Product, (vi) research services related to the AstraZeneca Lead Product, (vii) participation on each of the committees, (viii) four research licenses for the AstraZeneca Collaboration Products, (ix) four commercial licenses for the AstraZeneca Collaboration Products, (x) research services for the AstraZeneca Collaboration Products and (xi) certain phase 2a services for the AstraZeneca Lead Product. Additionally, as the development licenses on the four AstraZeneca Collaboration Products may be granted at a discount in the future, the Company determined such discounts should be assessed as material rights at inception.

Management evaluated all of the promised goods or services within the contract and determined which such goods and services

were separate performance obligations. The Company determined that the licenses granted for the AstraZeneca Lead Product at the inception of the arrangement should be combined with the research services related to the AstraZeneca Lead Product and the licenses granted for the AstraZeneca Collaboration Products should be combined with the research services for the AstraZeneca Collaboration Products, as the licenses are not capable of being distinct. A third party would not be able to provide the research and development services, due to the specific nature of the intellectual property and knowledge required to perform the services and AstraZeneca could not benefit from the licenses without the corresponding services. The Company also determined that each of the phase 1 services and the phase 2a services for the AstraZeneca Lead Product were distinct and that the participation on the various committees was also distinct as all of the phase 1 services, phase 2a services and the committee services could be performed by an outside party. The Company determined that the commercial licenses for the AstraZeneca Collaboration Products granted at the inception of the arrangement should be combined with the development licenses for the AstraZeneca Collaboration Products as the company would not benefit from the commercial license without the ability to develop each product.

As a result, management concluded that there were 16 performance obligations: (i) combined performance obligation comprised of a non-exclusive platform technology license, research and development license, and commercial licenses for the AstraZeneca Lead Product and research services for the AstraZeneca Lead Product, (ii) combined performance obligation comprised of development and manufacturing services, and technology transfer services for the AstraZeneca Lead Product, (iii) committee participation, (iv-vii) four combined performance obligations each comprised of a non-exclusive platform technology license, research licenses, and research services for each AstraZeneca Collaboration Product (viii-xi) four performance obligations comprised of a material right to acquire the development licenses granted for the AstraZeneca

Collaboration Products, (xii-xv) four performance obligations comprised of the commercial licenses granted for the AstraZeneca Collaboration Products and (xvi) phase 2a services.

The Company allocated consideration to the performance obligations based on the relative proportion of their standalone selling prices. The Company developed standalone selling prices for licenses and corresponding research services by applying a risk adjusted, net present value, estimate of future potential cash flow approach, which included the cost of obtaining research services at arm’s length from a third-party provider, as well as internal full-time equivalent costs to support these services. The Company developed its standalone selling price for development and manufacturing services, and technology transfer services for the AstraZeneca Lead Product using estimated internal and external costs to be incurred.

The Company developed its standalone selling price for committee participation by using management’s estimate of the anticipated participation hours multiplied by a market rate for comparable participants.

The Company developed its standalone selling price for the commercial licenses and material rights granted on the development licenses by probability weighting multiple cash flow scenarios using the income approach.

The transaction price was comprised of fixed consideration of $45.0 million in upfront fees and variable consideration of (i) $14.2 million in estimated phase 1 services, (ii) $12.5 million in milestone payments achieved upon the initiation of a phase 1 study in December 2017, and (iii) $4.7 million in estimated phase 2a services. The $45.0 million upfront fee, which represents the fixed consideration in the transaction price, was allocated to each of the performance obligations based on the relative proportion of their standalone selling prices. Variable consideration of $14.2 million is related to the phase 1 services and will be allocated entirely to the performance obligation to which they relate. Variable consideration of $12.5 million related to the phase 1 trial milestone was allocated by relative selling price to the combined performance obligation comprised of a non-exclusive platform technology license, research and development license and commercial licenses for the AstraZeneca Lead Product and research services for the AstraZeneca Lead Product, and the combined performance obligation comprised of development and manufacturing services and technology transfer services for the AstraZeneca Lead Product performance obligations. Variable consideration of $4.7 million for phase 2a services was allocated specifically to the related performance obligation.

The amounts allocated to the license performance obligation for the AstraZeneca Lead Product and the four performance obligations for the four research licenses for AstraZeneca Collaboration Products will be recognized on a proportional performance basis as the activities are conducted over the life of the arrangement. The amounts allocated to the performance obligation for phase 1 services, technology transfer services for the AstraZeneca Lead Product will be recognized on a proportional performance basis over the estimated term of development through phase 2a study. The amounts allocated to the performance obligation for phase 2a services for the AstraZeneca Lead Product will be recognized on a proportionate performance basis over an estimated term of 12 months. The amounts allocated to the performance obligation for participation on each of the committees will be recognized on a straight-line basis over the expected term of development of the AstraZeneca Lead Product and the AstraZeneca Collaboration Products. The term of performance is approximately five years. The amounts allocated to the four performance obligations for the material rights to acquire a development license and the four performance obligations for commercial licenses for the AstraZeneca Collaboration Products will be recognized upon exercise of the specific material right and delivery of each of the development licenses. As of December 31, 2020, there was $25.4 million of aggregate transaction price allocated to remaining performance obligations.

Additionally, the Company evaluated payments required to be made between both parties as a result of the shared development costs of the AstraZeneca Lead Product and the two AstraZeneca Collaboration Products for which the Company has a co-development option. The Company will classify payments made as a reduction of revenue and will classify payments received as revenue, in the period they are earned.

Under the AstraZeneca Agreements, the Company is eligible to receive various research, development, commercial and sales milestones. There is uncertainty that the events to obtain the research and development milestones will be achieved given the nature of clinical development and the stage of the Company’s technology. The Company has thus determined that all research and development milestones, other than the phase 1 initiation milestone achieved in December 2017 and included in the impact of adoption of ASC 606, will be constrained until it is deemed probable that a significant revenue reversal will not occur.

In October 2019, the JSC formally approved the termination of a certain performance obligation determined at the origination of the agreement, resulting in the acceleration of remaining revenue associated with the performance obligations. The JSC's termination of the performance obligations does not impact the remainder of the Pieris-AstraZeneca alliance and the parties continue to advance the Lead Product through Phase 2a activities.

As of December 31, 2020, there is $0.9 million and $18.6 million of current and non-current deferred revenue, respectively, related to the AstraZeneca Agreements.

The Company incurred $1.6 million of third-party success fees to obtain the contract with AstraZeneca. Upon adoption of ASC 606, the Company capitalized $1.1 million in accordance with ASC 340. As of December 31, 2020, the remaining balance of the asset recognized from transaction costs to obtain the AstraZeneca contract is $0.7 million. Amortization during the year ended December 31, 2020 was de minimis.

On March 29, 2021, the Company and AstraZeneca entered into (1) Amendment No. 1 to the Non-exclusive Anticalin® Platform License Agreement dated May 2, 2017 and (2) Amendment No. 2 to the License and Collaboration Agreement dated May 2, 2017, as previously amended by Amendment No. 1 dated September 14, 2020, collectively, the Amended Collaboration Agreement. Under the Amended Collaboration Agreement, the parties agreed to restructure certain commercial economics for the AZD1402/PRS-060 program by increasing potential sales milestones and reducing potential sales royalties, while fundamentally maintaining the overall value split between AstraZeneca and the Company.

In connection with the Amended Collaboration Agreement, the Company and AstraZeneca entered into a Subscription Agreement pursuant to which the Company agreed to issue to AstraZeneca, and AstraZeneca agreed to acquire from the Company, 3,584,230 shares of the Company’s common stock for a total purchase price of $10.0 million, or $2.79 per share, in a private placement transaction pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended. The Subscription Agreement will close on April 1, 2021 and includes a requirement that the Company file a registration statement to register the resale of the shares issued to AstraZeneca within 60 calendar days of the issuance of the shares.

Also in March 2021, the Company earned a $13.0 million milestone from AstraZeneca related to the initiation of the phase 2a study for PRS-060/AZD1402.

Servier

On January 4, 2017, the Company entered into a license and collaboration agreement, or Servier Collaboration Agreement, and a non-exclusive Anticalin platform license agreement, or Servier Platform License, and together with the Servier Collaboration Agreement, the Servier Agreements with Les Laboratoires Servier and Institut de Recherches Internationales Servier, or Servier, pursuant to which the Company and Servier agreed to initially pursue five bispecific therapeutic programs.

Five committed programs were initially defined, which may combine antibodies from the Servier portfolio with one or more Anticalin proteins based on the Company’s proprietary platform to generate innovative IO bispecific drug candidates, or the Collaboration Products. The collaboration may be expanded by up to three additional therapeutic programs. The Company had the option to co-develop and retain commercial rights in the United States for PRS-332, the initial lead program under the collaboration, or the Initial Lead, and has a similar option on up to three additional programs, or the Co-Development Collaboration Products, while Servier will be responsible for development and commercialization of the other programs worldwide, or the Servier Worldwide Collaboration Products. Each party is responsible for an agreed upon percentage of shared costs, as set forth in the budget for the collaboration plan, and as further discussed below.

The Co-Development Collaboration Products may be jointly developed, according to a collaboration plan, through marketing approval from the U.S. Food and Drug Administration or the European Medicines Agency. Servier Worldwide Collaboration Products may be jointly developed, according to a collaboration plan, through specified preclinical activities, at which point Servier becomes responsible for further development of the Collaboration Product.

At inception, Servier was granted the following licenses: (i) development license for the Initial Lead, (ii) commercial license for the Initial Lead, (iii) individual research licenses for each of the four Collaboration Products, and (iv) individual non-exclusive platform technology licenses for the Initial Lead and for each of the four Collaboration Products. Upon achievement of certain development activities, specified by the collaboration for each Servier Agreement, Servier will be granted a development license and a commercial license. For the Initial Lead and the Co-Development Collaboration Products, the licenses granted are with respect to the entire world except for the United States. For Servier Worldwide Collaboration Products, the licenses granted are with respect to the entire world.

The Servier Agreements are managed on an overall basis by a joint executive committee, or JEC, formed by an equal number of members from the Company and Servier. Decisions by the JEC will be made by consensus; however, in the event of a disagreement, each party will have final-decision making authority as it relates to the applicable territory in which such party has commercialization rights for the applicable product. In addition to the JEC, the Servier Collaboration Agreement requires the participation of both parties on: (i) a JSC, (ii) a JDC, (iii) a joint intellectual property committee, or JIPC, and (iv) a joint

research committee, or JRC. The responsibilities of these committees vary, depending on the stage of development and commercialization of the Collaboration Products.

For the Initial Lead and Co-Development Collaboration Products, the Company and Servier are responsible for an agreed upon percent of the shared costs required to develop the products through commercialization. In the event that the Company fails to exercise its option to co-develop the Co-Development Collaboration Products, Servier has the right to continue with the development and will be responsible for all costs required to develop the products through commercialization.

Under the Servier Agreements, the Company received an upfront, non-refundable payment of €30.0 million (approximately $32.0 million). In addition, the Company is eligible to receive research, development, commercial, and sales milestone payments as well as tiered royalties up to low double digits on the sales of commercialized products in the Servier territories. The Company achieved two preclinical milestones under the program, one in December 2018 for €0.5 million (approximately $0.6 million) and another in February 2019 for €1.5 million (approximately $1.7 million), both of which became billable on their respective achievement dates.

The initial research collaboration term, as it relates to the Initial Lead and Collaboration Products, shall continue for three years from the effective date of the Servier agreements, and may be mutually extended for two one-year terms consecutively applied.

The term of each Servier Agreement ends upon the expiration of all of Servier’s payment obligations under such Servier Agreement. The Servier Agreements may be terminated by Servier for convenience beginning 12 months after their effective date upon 180 days’ notice. The Servier Agreements may also be terminated by Servier or the Company for material breach upon 90 days’ or 120 days’ notice under the Servier Collaboration Agreement and the Servier Platform License, respectively, provided that the applicable party has not cured such breach by the applicable 90-day or 120-day permitted cure period, and dispute resolution procedures specified in the applicable Servier Agreement have been followed. The Servier Agreements may also be terminated due to the other party’s insolvency or for a safety issue and may in certain instances be terminated on a product-by-product and/or country-by-country basis. The Servier Platform License will terminate upon termination of the Servier Collaboration Agreement, on a product-by-product and/or country-by-country basis. In February 2020, the research term was extended for 12 months. The research term was then extended for another 12 months in February 2021.

As the Company and Servier are considered to be active participants in the Servier Agreements and are exposed to significant risks and rewards, certain units of account within the Servier Agreements are within the scope of ASC 808. The arrangement with Servier provides for the transfer of the following goods and services: (i) five non-exclusive platform technology licenses, a development license, a commercial license and research and development services for the Initial Lead, (ii) participation on each of the committees, (iii) four research licenses for Collaboration Products, and (iv) research and development services for the Collaboration Products. Additionally, as the development and commercial licenses on the four Collaboration Products may be granted at a discount in the future, the Company determined such discounts should be assessed as material rights at inception.

Management evaluated all of the promised goods or services within the contract and determined which goods and services

were separate performance obligations. The Company determined that the licenses granted at the inception of the Servier collaboration, should be combined with the research and development services to be provided for the Initial Lead and Collaboration Products, over the term of the Servier Agreements, as such licenses are not capable of being distinct. A third party would not be able to provide the research and development services, due to the specific nature of the intellectual property and knowledge required to perform the services, and Servier could not benefit from the licenses without the corresponding services. The Company determined that the participation on the various committees was distinct as the services could be performed by an outside party.

As a result, management concluded that there are 10 performance obligations at the inception of the Servier Agreements. The following performance obligations are within the scope of ASC 808: (i) combined performance obligation comprised of a non-exclusive platform technology license, commercial license, development license and research and development services for the Initial Lead, (ii) two separate performance obligations each comprised of a combined non-exclusive platform technology license, research license, and research and development services for each Co-Development Collaboration Product (iii) one performance obligation comprised of participation in the various governance committees, and (iv) two combined performance obligations comprised of the development and commercial licenses granted for the Co-Development Collaboration Products (and corresponding discounts) upon the achievement of specified preclinical activities, resulting in material rights. The following performance obligations are within the scope of ASC 606: (i) two separate performance obligations each comprised of a combined non-exclusive platform technology license, research license and research and development services for each Servier Worldwide Collaboration Product, and (ii) two combined performance obligations comprised of the development and commercial licenses granted for the Servier Worldwide Collaboration Products (and corresponding discounts) upon the achievement of specified preclinical activities, resulting in material rights.

The Company allocated consideration to the performance obligations based on the relative proportion of their standalone selling prices. The Company developed its standalone selling prices for licenses by applying a risk adjusted, net present value, estimate of future potential cash flows approach, which included the cost of obtaining research and development services at arm’s length from a third-party provider, as well as internal full-time equivalent costs to support these services.

The Company developed its estimate of standalone selling price for committee participation by using management’s estimate of the anticipated participation hours multiplied by a market rate for comparable participants.

The Company developed its estimate of standalone selling price for the material rights granted on the development and commercial licenses granted for the Collaboration Products by probability weighting multiple cash flow scenarios using the income approach.

The transaction price at inception is comprised of the fixed upfront fee of €30.0 million (approximately $32.0 million) and was allocated to the performance obligations based on the relative proportion of their standalone selling prices.

The amounts allocated to the performance obligation for the Initial Lead and the four performance obligations for the four research and development licenses for Collaboration Products will be recognized on a proportional performance basis as the activities are conducted over the life of the arrangement. The term of the performance at inception of the Servier Agreements for the Initial Lead and each of the Co-Development Collaboration Products may be through approval of certain regulatory bodies; a period which could be many years. The term of the performance for each of the other two Servier Worldwide Collaboration Products is through the initial research and collaboration term, plus potential extensions. The amounts allocated to the performance obligation for participation on each of the committees will be recognized on a straight-line basis over the anticipated performance period over the entirety of the arrangement with Servier. The amounts allocated to the four performance obligations for the material rights to acquire development and commercial licenses for the Co-Development Collaboration Products are granted in the future will be recognized over time upon delivery of each of the licenses through marketing approval. The amounts allocated to the four performance obligations for the material rights to acquire development and commercial licenses for the Servier Developed Collaboration Products are granted in the future will be recognized upon delivery of each of the licenses. As of December 31, 2020, there was $11.6 million of aggregate transaction price allocated to remaining performance obligations.

Additionally, the Company evaluated payments required to be made between both parties as a result of the shared development costs of the Initial Lead and Collaboration Products. The Company will classify payments made as a reduction of revenue and will classify payments received as revenue, in the period they are earned.

Under the Servier Agreements the Company is eligible to receive various research, development, commercial, and sales milestones. There is uncertainty that the events to obtain the research and development milestones will be achieved given the nature of clinical development and the stage of the Company’s technology. The Company has thus determined that all research and development milestones will be constrained until it is deemed probable that a significant revenue reversal will not occur.

In September 2019, Servier notified the Company of its decision to discontinue co-development of PRS-332, a PD-1-LAG-3 bispecific that served as the initial development program under the Pieris-Servier alliance, for strategic reasons. The Company does not presently intend to continue development of PRS-332 but retains full rights to advance the development and commercialization of the product on a world-wide basis in the future.

In February 2020, the research term was extended for 12 months. The Company updated the transaction price for the extension for revenue recognition purposes and allocated it ratably over all unsatisfied performance obligations. As part of the expiration of the initial research term, the option to expand the collaboration beyond the initial five committed programs also expired. In March 2020, Servier notified the Company of its decision to discontinue co-development of two earlier preclinical stage programs for strategic reasons based upon an extensive portfolio review. The notification required a 60-day period to complete remaining obligations on the programs; however, the Company determined that the material rights to acquire development and commercial licenses for one Co-Development Collaboration Product and for one Servier Developed Collaboration Products lapsed in March 2020 and recognized $7.1 million of previously deferred revenue associated with these material rights during 2020. The discontinuation of the two earlier preclinical stage programs decreased the future potential milestone payments the Company could achieve. The parties continue to advance the development of two preclinical programs: PRS-344, a 4-1BB/PD-L1 bispecific designed as a co-development program, and PRS-352, which addresses undisclosed targets and for which Servier has worldwide rights.

In February 2021, the research term was extended for another 12 months.

As of December 31, 2020, there is $6.0 million and $5.5 million of current and non-current deferred revenue, respectively, related to the Servier Agreements.

The Company incurred costs to obtain the contract with Servier. Upon adoption of ASC 606, the Company capitalized $0.5 million of third-party service fees in accordance with ASC 340. As of December 31, 2020, the remaining balance of the asset recognized from costs to obtain the Servier contract is $0.2 million. Amortization during the twelve months ended December 31, 2020 was $0.1 million.

Other License Agreements

ASKA

On February 27, 2017 the Company entered into an exclusive option agreement, or the ASKA Option Agreement with ASKA Pharmaceutical Co., Ltd., or ASKA, pursuant to which Pieris granted ASKA an option to acquire (i) a non-exclusive license to certain intellectual property rights associated with the Company’s Anticalin platform, and (ii) an exclusive license to certain intellectual property rights specifically related to the Company’s PRS-080 Anticalin protein, in order to develop, manufacture, import, sale, export, and offer for sale and export any pharmaceutical formulation containing PRS-080, the Company’s PEGylated Anticalin protein targeting hepcidin, or the Licensed Product, in Japan and certain other Asian territories.

Upon receipt, ASKA had up to 60 days to evaluate the results of the phase 2a study, or the Evaluation Period. In November 2019, the Company delivered the finals results of the study to ASKA, thus triggering the 60-day evaluation period.

The Company determined that the completed phase 2a study represents the sole good or service to be transferred, and the only performance obligation under the ASKA Option Agreement for which an upfront payment of $2.75 million was received from ASKA. With the formal delivery of the final results in November 2019, the full $2.75 million revenue that was previously constrained was recognized in connection with this arrangement for the year ended December 31, 2019. No revenue under this arrangement was recognized in 2020.

On January 20, 2020 ASKA notified the Company that it does not intend to exercise its option to obtain an exclusive license to develop and commercialize the PRS-080. The term of the ASKA Option Agreement ended as of the date of ASKA’s notification of its decision not to exercise its option rights.

In connection with obtaining the contract with ASKA, the Company additionally incurred $0.3 million in third-party service fees which were capitalized in accordance with ASC 340. These costs were fully amortized as of December 31, 2019.

Contract Balances

The Company receives payments from its collaboration partners based on payments established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until such time as the Company satisfies its performance obligations under each arrangement. A contract asset is a conditional right to consideration in exchange for goods or services that the Company has transferred to a customer. Amounts are recorded as accounts receivable when the Company’s right is unconditional.

There were $1.6 million of additions to deferred revenue during the twelve months ended December 31, 2020 and reductions to deferred revenue were $15.0 million for the twelve months ended December 31, 2020.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Collaboration agreements	12 Months Ended
Collaboration agreements	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Collaboration agreements	Collaboration agreements In August 2020, the Company entered into a Clinical Trial Collaboration and Supply Agreement, or the Lilly Agreement, with Eli Lilly and Company, or Lilly, pursuant to which the Company and Lilly will collaborate on a phase 2 clinical study, or the Study, to determine the safety and efficacy of the Company's cinrebafusp alfa in combination with the standard of care regimen for the second-line treatment of advanced or metastatic gastric cancer, ramucirumab (CYRAMZA®) and paclitaxel for the second-line treatment of HER2+ gastric cancer. Under the terms of the non-exclusive Lilly Agreement, the Company will sponsor the Study and Lilly will supply the Company with ramucirumab as well as provide input on certain clinical and regulatory aspects of the Study in exchange for jointly owning clinical data and inventions relating to the combination regimen that may arise from the Study. Any material changes to the protocol for the Study, and any changes relating to ramucirumab, will require Lilly’s prior written consent, which shall not be unreasonably withheld, conditioned or delayed. The Lilly Agreement will expire upon completion of the parties’ contractual obligations. The Lilly Agreement may also be terminated (a) by either party for an uncured material breach by the other party upon 60 days’ notice, subject to a reasonable extension if such material breach requires more than 60 days to cure; (b) by either party in the event that the Study unreasonably affects patient safety, provided that the terminating party promptly notifies the other party and the other party is given the opportunity to propose modifications to the Study to address the safety issues; (c) by either party, following 15 days’ written notice, if regulatory action is taken preventing the terminating party from providing its compound or if the terminating party decides to discontinue development of its compound; (d) by either party, immediately upon written notice to the other party for breach by the other party of its material obligations under certain sections of the Lilly Agreement, or breach of certain of the other party's representations and warranties; and (e) by Lilly in the event of certain safety concerns related to the use of ramucirumab in the Study. The Company concluded that the Lilly Agreement is within the scope of ASC 808, which defines collaborative arrangements and addresses the presentation of the transactions between the two parties in the income statement and related disclosures. However, ASC 808 does not provide guidance on the recognition of consideration exchanged or accounting for the obligations that may arise between the parties. The Company has concluded that ASC 730, Research and Development, should be applied by analogy. There is no financial statement impact for the Lilly Agreement as the value of the drug supply received from Lilly is offset against the drug supply cost.

Cash, Cash Equivalents and Investments

12 Months Ended

Dec. 31, 2020

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Investments

As of December 31, 2020 and 2019, cash, cash equivalents and investment comprised funds in depository, money market accounts, U.S. treasury securities, asset backed securities, and corporate bonds. The following table presents the cash equivalents and investments carried at fair value in accordance with the hierarchy defined in Note 2 at December 31, 2020 and 2019 (in thousands):


	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2020
Money market funds, included in cash equivalents	$	63,951	$	63,951	$	—	$	—



Total	$	63,951	$	63,951	$	—	$	—


	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2019
Money market funds, included in cash equivalents	$	47,384	$	47,384	$	—	$	—

Investments - US treasuries	5,300		5,300		—		—
Investments - Asset-backed securities	7,950		—		7,950		—
Investments - Corporate bonds	28,644		—		28,644		—
Total	$	89,278	$	52,684	$	36,594	$	—

Cash equivalents and marketable securities have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market-based approaches and observable market inputs to determine value. The Company validates the prices provided by its third-party pricing services by reviewing their pricing methods and obtaining market values from other pricing sources, as needed. After completing its validation procedures, the Company did not adjust any fair value measurements provided by the pricing services as of December 31, 2019.

Investments at December 31, 2019 consist of the following (in thousands):


	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses		Fair Value
Investments
US treasuries	46-182	$	5,293	$	25	$	(18)	$	5,300
Asset-backed securities	49-106	7,962		12		(24)		7,950
Corporate bonds	2-204	28,709		20		(85)		28,644
Total		$	41,964	$	57	$	(127)	$	41,894

There were $0.6 million of realized losses for the year ended December 31, 2020 and $0.3 million of realized gains for the year ended December 31, 2019.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment are summarized as follows (in thousands):


	Years Ended December 31,
	2020		2019
Laboratory equipment	$	11,188	$	11,635
Office furniture and equipment	2,120		479
Computer equipment	394		245
Leasehold improvements	14,159		10,710
Property and equipment at cost	27,861		23,069
Accumulated depreciation	(5,815)		(3,567)
Property and equipment, net	$	22,046	$	19,502

Depreciation expense was $2.1 million and $0.6 million for the years ended December 31, 2020 and 2019, respectively. There were no other changes in accumulated depreciation other than the foreign currency impact.

Accrued Expenses

12 Months Ended

Dec. 31, 2020

Payables and Accruals [Abstract]

Accrued Expenses

Accrued expenses and other current liabilities consisted of the following (in thousands):


	Years Ended December 31,
	2020		2019
Compensation expense	$	2,759	$	2,870
Research and development fees	2,001		1,048
Accrued accounts payable	1,220		4,251
Lease liabilities	1,030		733
Accrued license obligations	358		62
Audit and tax fees	128		522
Other current liabilities	235		458
Total	$	7,731	$	9,944

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

The Company reported a loss before income taxes consisting of the following (in thousands):


	Years Ended December 31,
	2020		2019
Domestic	$	(12,134)	$	(12,063)
Foreign	(24,932)		(13,406)
Loss before income taxes	$	(37,066)	$	(25,469)

The components of the provision for income taxes are as follows (in thousands):


	Years Ended December 31,
	2020		2019
Current:
Federal	$	—	$	—
State	—		—
Foreign	164		—
Total current	164		—
Deferred:
Federal	—		—
State	—		—
Foreign	—		—
Total deferred	—		—
Provision for income taxes	$	164	$	—

The reconciliation of the federal statutory rate to the Company’s effective tax rate is as follows:


	2020		2019
Federal income tax rate	21.0	%	21.0	%

Foreign rate differential	1.9		1.9
State tax, net of federal benefit	1.9		2.6
US tax on foreign income	—		(1.2)
Share-based awards compensation	(3.8)		(2.5)
Permanent items	(2.4)		(1.0)
Other	(0.4)		0.8
Rate change - trade tax NOL	—		(6.4)
Change in valuation allowance	(18.7)		(15.2)
Effective income tax rate	(0.5)	%	—	%

The components of deferred tax assets and liabilities related to net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income taxes purposes were as follows (in thousands):


	Years Ended December 31,
	2020		2019
Deferred tax assets:
Net operating loss carryforwards	$	39,175	$	30,455
Share-based awards compensation	2,913		2,705
Accrued expenses	230		328
Depreciation and other	297		53

Unrealized foreign currency	771		90
Lease liability	4,582		4,378
Total deferred tax assets	47,968		38,009
Deferred tax liabilities:
Right-of-use asset	(4,235)		(4,043)


Total deferred tax liabilities	(4,235)		(4,043)
Less: valuation allowance:	(43,733)		(33,966)
Net deferred tax asset	$	—	$	—

The Company operates in multiple jurisdictions. Accordingly, the Company files U.S. federal and state income tax returns as well as returns in multiple foreign jurisdictions. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable

income, and tax-planning strategies in making this assessment. Management believes it is more likely than not that the results of future operations will not generate sufficient taxable income in the United States or in its foreign jurisdictions to realize the full benefits of its deferred tax assets. As of December 31, 2020, the Company continues to maintain a full valuation allowance against all net deferred tax assets.

The cumulative amount of earnings of our foreign subsidiaries are expected to be permanently invested in the foreign subsidiaries. Deferred taxes have not been provided on the excess of book basis over tax basis, or the excess tax basis over book basis in the shares of our foreign subsidiaries because these basis differences are not expected to reverse in the foreseeable future and are essentially permanent in duration. Our intention is to reinvest the earnings of the foreign subsidiaries indefinitely.

The increase in the valuation allowance of deferred tax assets of $9.8 million was primarily a result of the operating losses generated in current tax year.

As of December 31, 2020, the Company had net operating loss carryforwards for U.S. federal income tax purposes of $27.3 million and net operating loss carryforwards for state income tax purposes of $33.2 million. Federal tax loss carryforwards that were created prior to December 31, 2017 expire through 2037 and federal losses created after that date do not expire. State loss carryforwards expire starting in 2035. In the United States, utilization of the NOL carryforwards may be subject to a substantial annual limitation under Section 382 of the Code and similar state provisions due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company has not currently completed a study to assess whether an ownership change has occurred, or whether there have been multiple ownership changes since the acquisition of the U.S. entity in 2014. Since the Company has incurred net operating losses since inception, it has never been subject to a revenue agent review. The Company is currently open to examination under the statute of limitations by the Internal Revenue Service and state jurisdictions for the tax years ended 2016 through 2019. Carryforward tax attributes generated in years past may still be adjusted upon future examination if they have or will be used in a future period. The Company is currently under examination in Germany for 2014 through 2017; however, the Company is not under examination by the Internal Revenue Service or any other jurisdictions for any tax years.

As of December 31, 2020, the Company had German corporate income tax and trade tax net operating loss carryforwards of approximately $116.6 million and $115.1 million respectively. Under current German laws, tax loss carryforwards may only be used to offset any relevant later assessment period (calendar year) of $1.2 million plus 60% of the exceeding taxable income and trade profit of such period and do not expire. In addition, certain transactions, including transfers of shares or interest in the loss holding entity, may result in the partial or total forfeiture of tax losses existing at that date. Partial or total forfeiture of tax losses may further occur in corporate reorganizations of the loss holding entity.

The Company accounts for uncertain tax positions pursuant to ASC 740, Income Taxes, which prescribes a recognition threshold and measurement process for financial statement recognition of uncertain tax positions taken or expected to be taken in a tax return. If the tax position meets this threshold, the benefit to be recognized is measured at the largest amount of benefit that is more likely than not (determined by cumulative probability) of being realized upon ultimate settlement with the taxing authority. The Company recorded an uncertain tax position related to a prior year position, that if successfully challenged by tax authorities could result in the loss of certain tax attributes. The balance of uncertain tax positions will remain until such time that settlement is reached with the relevant tax authorities or should the statute of limitations expire. The Company recognizes interest and penalties, if any, related to uncertain tax positions in income tax expense. No interest and penalties related to uncertain tax positions were accrued at December 31, 2020 and December 31, 2019.

The following table sets forth a reconciliation of the beginning and ending amounts of unrecognized tax benefits, excluding the impact of interest and penalties, for the years ended December 31, 2020 and 2019 (in thousands):


Unrecognized tax benefits at December 31, 2019	$	6,032
Currency translation adjustment	103
Unrecognized tax benefits at December 31, 2020	$	6,135

The Company does not expect unrecognized tax benefits to change significantly over the next 12 months. The full amount of unrecognized tax benefits would impact the effective rate, subject to valuation allowance considerations, if recognized.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Stockholders' equity	12 Months Ended
Stockholders' equity	Dec. 31, 2020
Equity [Abstract]
Stockholders' equity	Stockholders’ equity The Company has issued multiple tranches of preferred stock that consist of the following: •Series A Convertible, 2,907 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively. •Series B Convertible, 5,000 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively. •Series C Convertible, 3,522 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively. •Series D Convertible, 3,000 and zero shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively. Common Stock Each share of the Company’s common stock is entitled to one vote and all shares rank equally as to voting and other matters. Dividends may be declared and paid on the common stock from funds legally available therefor, if, as and when determined by the Board of Directors. Series A Preferred Stock In June 2016, the Company entered into a securities purchase agreement, or the Securities Purchase Agreement, for a private placement of the Company’s securities with a select group of institutional investors, or the 2016 PIPE. The 2016 PIPE sale transaction, by the Company, consisted of 8,188,804 units at a price of $2.015 per unit for gross proceeds, to the Company, of approximately $16.5 million. After deducting for placement agent fees and offering expenses, the aggregate net proceeds from the private placement was approximately $15.3 million. Each unit consisted of (i) one share of the Company’s common stock or non-voting series A convertible preferred stock, or the Series A Preferred Stock, which are convertible into one-thousand shares of common stock, (ii) one warrant to purchase 0.4 shares of common stock at an exercise price of $2.00 per share and (iii) one warrant to purchase 0.2 shares of common stock at an exercise price of $3.00 per share. The warrants will be exercisable for a period of 5 years from the date of issuance. Each share of Series A Preferred Stock was issued at a price of $2.015 per share, and is convertible into 1,000 shares of common stock, provided the holder and/or its affiliates do not own greater than 9.99% of the total number of Pieris common stock then outstanding. The Series A Preferred Stock has a par value of $0.001 per share, has no registration or voting rights, and holders are entitled to receive dividends on a pari passu basis with the Company´s common stock, when, and if declared. In event of a true liquidation or winding down of the business, holders of Series A Preferred Stock will be paid prior to the holders of common stock. In connection with the 2016 PIPE, the Company issued 3,225,804 shares of common stock and 4,963 shares of Series A Preferred Stock to the 2016 PIPE investors. Series B Preferred Stock On January 30, 2019, the Company and certain entities affiliated with Biotechnology Value Fund, L.P., or BVF entered into an exchange agreement pursuant to which BVF agreed to exchange an aggregate of 5,000,000 shares of the Company’s common stock owned by BVF for an aggregate of 5,000 shares of Series B Preferred Stock. On January 31, 2019, the Company designated 5,000 shares of its authorized and unissued preferred stock as Series B Preferred Stock and filed a Certificate of Designation of Series B Convertible Preferred Stock of Pieris Pharmaceuticals, Inc., or the Series B Certificate of Designation, with the Nevada Secretary of State. Each share of Series B Preferred Stock is convertible into 1,000 shares of the Company's common stock (subject to adjustment as provided in the Series B Certificate of Designation) at any time at the option of the holder, provided that the holder is prohibited from converting the Series B Preferred Stock into shares of the Company's common stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.99% of the total number of shares of Common Stock then issued and outstanding, or the Beneficial Ownership Limitation. The holder may reset the Beneficial Ownership Limitation to a higher or lower number, not to exceed 19.99% of the total number of common shares issued and outstanding immediately after giving effect to a conversion, upon providing written notice to the Company. Any such notice providing for an increase to the Beneficial Ownership Limitation will be effective 61 days after delivery to the Company. In the event of the Company’s liquidation, dissolution or winding up, subject to the rights of holders of Senior Securities (defined below), holders of Series B Preferred Stock are entitled to receive a payment equal to $0.001 per share of Series B Preferred Stock before any proceeds are distributed to the holders of common stock and Junior Securities (defined below) and pari passu with any distributions to the holders of the previously issued Series A convertible preferred stock, or the Series A Preferred Stock, plus an additional amount equal to any dividends declared but unpaid on such shares. However, if the assets of the Company are insufficient to comply with the preceding sentence, then all remaining assets of the Company shall be distributed ratably to holders of the shares of the Series B Preferred Stock and Parity Securities (defined below). Shares of Series B Preferred Stock generally have no voting rights, except as required by law and except that the consent of holders of a majority of the then outstanding Series B Preferred Stock is required to amend the terms of the Series B Certificate of Designation. Holders of Series B Preferred Stock are entitled to receive any dividends payable to holders of the Company's common stock and rank: •senior to all of the Company's common stock; •senior to any class or series of capital stock of the Company created after the designation of the Series B Preferred Stock specifically ranking by its terms junior to the Series B Preferred Stock; •on parity with all shares of Series A Preferred Stock and any class or series of capital stock of the Company created after the designation of the Series B Preferred Stock specifically ranking by its terms on parity with the Series B Preferred Stock; and •junior to any class or series of capital stock of the Company created after the designation of the Series B Preferred Stock specifically ranking by its terms senior to the Series B Preferred Stock; in each case, as to distributions of assets upon the Company’s liquidation, dissolution or winding up whether voluntarily or involuntarily and/or the right to receive dividends. 2019 Private Placement In November 2019, the Company entered into a securities purchase agreement for a private placement, or the Purchase Agreement with a select group of institutional investors, including lead investor BVF as well as existing and new investors, or Investors. At the time of entering into the Purchase Agreement, BVF was a more than 5% stockholder of the Company, holding shares of common stock, Series A Preferred Stock, Series B Preferred Stock and warrants to purchase shares of common stock. The private placement consisted of 9,014,960 units, at a price of $3.55 per unit, or the Financing, for gross proceeds of approximately $32.0 million, and net proceeds to the Company of approximately $31.0 million. Each unit consists of (i) one share of the Company’s common stock, or Common Shares, or 0.001 shares of non-voting Series C convertible preferred stock, or Series C Preferred Shares, and together with the Common Shares, or Shares, and (ii) one immediately-exercisable warrant to purchase one share of the Company’s common stock with an exercise price of $7.10, or Exercise Price. If (i) the initial public disclosure of the Phase 2a Study of PRS-060/AZD1402 that includes the “p” value achieved for the primary endpoint of such study reveals top-line data on the primary efficacy endpoint in the Phase 2a Study with a “p” value below 0.05 (i.e., p < 0.05) in at least one dose level; and (ii) the 10-day volume weighted average stock price commencing on the trading day immediately after the initial public disclosure is at least three percent more than the Exercise Price, ((i) and (ii), collectively, the “Performance Condition”), then the warrants will be exercisable for a period of 60 days from the date of the initial data disclosure and may only be exercised for cash. Otherwise, the warrants will be exercisable for a period of five years from the date of issuance, or Exercise Date. If the Performance Condition has not been met and the last reported sale price of the Company’s common stock immediately prior to the Expiration Date was greater than the Exercise Price, then the warrants shall be automatically deemed exercised on a cashless basis on the Expiration Date. Each Preferred Share is convertible into 1,000 shares of the Company’s common stock. The Company will not undertake any conversion of the Series C Preferred Shares, and a stockholder shall not have the right to convert any portion of the Series C Preferred Shares, to the extent that, after giving effect to the conversion such stockholder would beneficially own in excess of 9.99% of the number of shares of the Company’s common stock outstanding immediately after giving effect to such conversion. The holder may reset the Beneficial Ownership Limitation to a higher or lower number, not to exceed 19.99% of the total number of common shares issued and outstanding immediately after giving effect to a conversion, upon providing written notice to the Company. The Series C Preferred Shares have no voting rights, except as required by law and except that the consent of holders of a majority of the then outstanding Series C convertible preferred stock is required to amend the terms of the Series C Certificate of Designation. The Series C Preferred Shares are entitled to receive dividends on a pari passu basis with the Company’s common stock, when, and if declared. In any liquidation or dissolution of the Company, the Series C Preferred Shares rank senior to the Company’s common stock in the distribution of assets, to the extent legally available for distribution. Upon issuance, each Series C Preferred Share included an embedded beneficial conversion feature as the market price of the Company’s Common Stock on the date of issuance of the Series C convertible preferred stock was $3.43 per share. As a result, the Company recorded the intrinsic value of the beneficial conversion feature of $2.8 million as a discount on the Series C convertible preferred stock at issuance. As the Series C Preferred Shares are immediately convertible upon issuance and do not include a stated redemption date, the discount was immediately accreted as a deemed dividend. Series D Preferred Stock Conversion On March 31, 2020, the Company and certain entities affiliated with BVF entered into an exchange agreement pursuant to which, on April 1, 2020, BVF exchanged an aggregate of 3,000,000 shares of the Company’s common stock owned by BVF for an aggregate of 3,000 shares of Series D Preferred Stock. The Company designated 3,000 shares of its authorized and unissued preferred stock as Series D Preferred Stock and filed a Certificate of Designation of Series D Convertible Preferred Stock of Pieris Pharmaceuticals, Inc., or the Series D Certificate of Designation, with the Nevada Secretary of State. Each share of Series D Preferred Stock is convertible into 1,000 shares of Common Stock (subject to adjustment as provided in the Series D Certificate of Designation) at any time at the option of the holder, provided that the holder is prohibited from converting the Series D Preferred Stock into shares of Common Stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.99% of the total number of shares of Common Stock then issued and outstanding. The holder may reset the Beneficial Ownership Limitation to a higher or lower number (not to exceed 19.99% of the total number of Common Shares issued and outstanding immediately after giving effect to a conversion) upon providing written notice to the Company. Any such notice providing for an increase to the Beneficial Ownership Limitation will be effective 61 days after delivery to the Company. In the event of the Company’s liquidation, dissolution, or winding up, subject to the rights of holders of Senior Securities (defined below), holders of Series D Preferred Stock are entitled to receive a payment equal to $0.001 per share of Series D Preferred Stock before any proceeds are distributed to the holders of Common Stock and Junior Securities (defined below) and pari passu with any distributions to the holders of the Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock, plus an additional amount equal to any dividends declared but unpaid on such shares. However, if the assets of the Company are insufficient to comply with the preceding sentence, then all remaining assets of the Company shall be distributed ratably to holders of the shares of the Series D Preferred Stock and Parity Securities (defined below). Shares of Series D Preferred Stock generally have no voting rights, except as required by law and except that the consent of holders of a majority of the then outstanding Series D Preferred Stock is required to amend the terms of the Series D Certificate of Designation. Holders of Series D Preferred Stock are entitled to receive any dividends payable to holders of Common Stock, and rank: •senior to all of the Common Stock; •senior to any class or series of capital stock of the Company created after the designation of the Series D Preferred Stock specifically ranking by its terms junior to the Series D Preferred Stock; •on parity with all shares of Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and any class or series of capital stock of the Company created after the designation of the Series D Preferred Stock specifically ranking by its terms on parity with the Series D Preferred Stock; and •junior to any class or series of capital stock of the Company created after the designation of the Series D Preferred Stock specifically ranking by its terms senior to the Series D Preferred Stock, in each case, as to distributions of assets upon the Company’s liquidation, dissolution or winding up whether voluntarily or involuntarily and/or the right to receive dividends. Open Market Sale Agreement In August 2019, the Company entered into a sale agreement pursuant to which the Company may offer and sell shares of its common stock, from time to time, up to an aggregate gross sales proceeds of $50.0 million through an “at the market offering” program, the ATM Program, under a shelf registration statement on Form S-3. In the third quarter of 2020, the Company sold 3,571,428 shares at a price of $2.80 per share under the ATM Program. The transaction resulted in gross proceeds of $10.0 million, less a 3% contractual commission incurred for the sales agent, resulting in $9.7 million in net proceeds to the Company. Subsequent Event Equity Issuances Additionally, the Company completed two transactions subsequent to December 31, 2020, with two partners, Seagen and AstraZeneca, which included equity transactions as part of the agreements. Additional details regarding these transactions are included in Footnote 3.

Net Loss per Share	12 Months Ended
Net Loss per Share	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing net income (loss) by the weighted average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share calculation, preferred stock, stock options, and warrants are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share were the same for all periods presented. For the years ended December 31, 2020 and 2019, and as calculated using the treasury stock method, approximately 37.0 million and 33.4 million of weighted average shares, respectively, were excluded from the calculation of diluted weighted average shares outstanding as their effect was antidilutive.

Stock and Employee Benefit Plans

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Stock and Employee Benefit Plans

Employee, Director and Consultant Equity Incentive Plans

At the Annual Shareholder Meeting, held on June 23, 2020, the shareholders approved the 2020 Employee, Director and Consultant Equity Incentive Plan, or the 2020 Plan. The 2020 Plan permits the Company to issue up to 3,500,000 shares of common stock pursuant to awards granted under the 2020 Plan. Upon approval of the 2020 Plan, the 2019 Employee, Director and Consultant Equity Incentive Plan, or the 2019 Plan, was terminated; all unissued options were canceled and no additional awards will be made thereunder. All outstanding awards under the 2019 Plan will remain in effect and any awards forfeited from the outstanding awards will be allocated back into the 2020 Plan. The 2020 Plan, similar to the 2019 Plan, provided for the grant of stock options, restricted and unrestricted stock awards, and other stock-based awards to employees of the Company, non-employee directors of the Company, and certain other consultants performing services for the Company as designated by either the Board of Directors or the compensation committee of the Board of Directors.

There were approximately 1,579,678 shares remaining and available for grant under the 2019 Plan that terminated pursuant to the approval of the 2020 Plan. The 2020 Plan permits the Company to issue up to 3,500,000 shares reserved for issuance pursuant to the 2020 Plan and any additional shares which may be issued if awards outstanding under the Registrant’s 2014, 2016, 2018 and 2019 Plans are canceled or expire.

The Company’s stock options have a maximum term of 10 years from the date of grant. Stock options granted may be either incentive stock options or nonqualified stock options and the exercise price of stock options must be at least equal to the fair market value of the common stock on the date of grant. The Company’s general policy is to issue common shares upon the exercise of stock options.

The Company estimates the fair value of each stock award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:


	Years Ended December 31,
	2020	2019
Risk free interest rate	0.33% - 1.53%	1.41% - 2.60%
Expected term (in years)	5.00 - 5.73	5 - 5.73
Dividend yield	—	—
Expected volatility	70.0% - 75.8%	81.7% - 81.8%

The weighted-average fair value of the 2,311,481 and 2,489,269 options granted during the years ended December 31, 2020 and 2019 was $1.92 and $2.31, respectively. As of December 31, 2020, there were 3,475,104 shares available for future grant under the 2020 Plan.

The following table summarizes stock option activity for employees and non-employees:


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2019	8,259,915	$	3.60		$	7,987
Granted	2,311,481	3.15			—
Exercised	149,406	1.95			97
Canceled	830,867	4.58			101
Outstanding, December 31, 2020	9,591,123	$	3.44	6.84 years	$	2,303
Vested or expected to vest, December 31, 2020	9,591,123	$	3.44	6.84 years	$	2,303
Exercisable, December 31, 2020	6,123,532	$	3.28	5.81 years	$	2,269

Periodically, the Company grants inducement options, which are awards outside of approved stock option plans, and which are material awards to the executive officers or other personnel entering senior leadership roles with the Company. The terms of inducement option awards were substantially the same as those issued under our 2020 Plan. These awards are excluded from the table above. The following table summarizes stock option activity for these inducement options (in thousands):


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2019	1,200,000	$	4.36		$	130
Granted	—	$	—		$	—
Canceled or Expired	779,687	$	4.01		$	—
Outstanding, December 31, 2020	420,313	$	5.00	8.12 years	$	—
Vested or expected to vest	420,313	$	5.00	8.12 years	$	—
Exercisable, December 31, 2020	214,063	$	5.34	7.60 years	$	—

Employee Stock Purchase Plans

The 2018 ESPP provides eligible employees with the opportunity, through regular payroll deductions, to purchase shares of the Company’s common stock at 85% of the lower closing market price of the common stock at the beginning date or ending date of each purchase period. The plan includes two six-month purchase periods per year beginning in both June and December. The Company has reserved 500,000 shares of common stock for the administration of the 2018 ESPP. Total shares purchased under the plan were 69,544 and 113,112 for the years ended December 31, 2020 and 2019, respectively. The fair value of shares expected to be purchased under the 2018 ESPP using the Black-Scholes model with the following assumptions:


	Years Ended December 31,
	2020	2019
Risk free interest rate	0.10% - 0.18%	2.48	%
Expected term (in years)	0.5 years	0.5 years
Dividend yield	—	—
Expected volatility	74.36% - 120.89%	57.57	%

Total Stock-based Compensation Expense

Total stock-based compensation expense is recorded in operating expenses based upon the functional responsibilities of the individuals holding the respective options as follows (in thousands):


	Years Ended December 31,
	2020		2019
Research and development	$	2,394	$	2,446
General and administrative	2,696		2,928
Total stock-based compensation	$	5,090	$	5,374

As of December 31, 2020, the total unrecognized compensation cost related to all non-vested awards was $7.1 million of which $0.6 million are for inducement options. The Company expects to recognize the compensation cost over a remaining weighted-average period of 2.14 years.

License Agreement	12 Months Ended
License Agreement	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
License Agreement	License Agreement TUM License The Company and the Technical University of Munich, or TUM, initiated discussions in the second quarter of 2018 to clarify, expand and restructure the research and licensing agreement with TUM, the TUM License, including the parties’ obligations under the TUM License. The TUM License assigns or exclusively licenses to the Company certain intellectual property related to the Company's Anticalin platform technology. The parties' discussions relate to revised commercial terms and to re-initiating additional collaborations between faculty at TUM and Pieris. While an amended and restated license agreement has not yet been completed, the Company intends to enter into such an amendment. These discussions may also lead to an increase in the Company's collaborative research activities with TUM.

Leases

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Leases

The Company currently leases office space in Boston, Massachusetts. In August 2015, the Company entered into a sublease to lease approximately 3,950 square feet. The sublease expires on February 27, 2022 or such earlier date pursuant to the termination provisions of the sublease.

In October 2018, Pieris GmbH entered into a lease for office and laboratory space located in Hallbergmoos, Germany, or the Hallbergmoos Lease. Pieris GmbH moved its operations, formerly conducted in Freising, Germany, to the Hallbergmoos facility in February 2020.

Under the Hallbergmoos Lease, Pieris GmbH rents approximately 105,000 square feet, of which approximately 96,400 square feet were delivered by the lessor in February 2020 and approximately 8,600 square feet were delivered by the lessor by May 2020. An additional approximately 22,300 square feet is expected to be delivered by the lessor by October 2024. Pieris GmbH has a first right of refusal to lease an additional approximate 13,400 square feet.

The Hallbergmoos Lease provides for an initial rental term of 12.5 years which commenced in February 2020 when the leased property was delivered to Pieris GmbH. Pieris GmbH also has an option to extend the Hallbergmoos Lease for two additional 60-month periods. The Company is not reasonably certain to exercise the option to extend the lease expiration beyond its current expiration date. Pieris GmbH may sublease space within the leased property with lessor’s consent, which may not be unreasonably withheld.

Monthly base rent for the initial 105,000 square feet of the leased property, including parking spaces, will total approximately $0.2 million per month, which amount shall be adjusted starting on the second anniversary of the commencement date by an amount equal to the German consumer price index. In addition to the base rent, Pieris GmbH is also responsible for certain administrative and operational costs in accordance with the Hallbergmoos Lease. Pieris GmbH provided a security deposit of $0.8 million at upon signing the lease agreement. The Company will serve as a guarantor for the Hallbergmoos Lease.

The Hallbergmoos Lease included $11.5 million of tenant improvements allowance for normal tenant improvements, for which construction began in March 2019. The date of the construction coincided with the lease commencement date for accounting purposes under ASC 840, which did not change with the adoption off ASC 842. The Company capitalized the leasehold incentives which are included in Property and equipment, net on the Consolidated Balance Sheet and are amortized on a straight-line basis over the shorter of the useful life or the remaining lease term. The lease incentive allowance was also factored in as a reduction to the right-of-use asset upon the adoption of ASC 842.

The Company also leased approximately 19,000 square feet of office and laboratory space in Freising, Germany under four agreements, the Freising Leases, including three leases for space on three floors of the same building and a letter agreement for additional conference room space within the building. The Freising Leases all terminated on March 31, 2020.

The following table summarizes operating lease costs included in operating expenses (in thousands):


	Years Ended December 31,
	2020		2019

Operating lease costs	$	1,509	$	1,524
Variable lease costs (1)	708		293
Total lease cost	$	2,217	$	1,817
(1) Variable lease costs include certain additional charges for operating costs, including insurance, maintenance, taxes, utilities, and other costs incurred, which are billed based on both usage and as a percentage of the Company’s share of total square footage.

The following table summarizes the weighted-average remaining lease term and discount rate:


	As of December 31,
	2020		2019
Weighted-average remaining lease term (years)	11.4		12.1
Weighted-average discount rate	10.5	%	10.5	%

Cash paid for amounts included in the measurement of the lease liabilities were $2.2 million and $0.5 million for the twelve months ended December 31, 2020 and 2019, respectively.

As of December 31, 2020, the maturities of the Company’s operating lease liabilities and future minimum lease payments were as follows (in thousands):


	Total
2021	$	2,662
2022	2,458
2023	2,424
2024	2,424
2025	2,424
Thereafter	14,556
Total undiscounted lease payments	26,948
Less: present value adjustment	(9,986)
Present value of lease liabilities	16,962

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and Use of Estimates The accompanying consolidated financial statements of Pieris Pharmaceuticals, Inc. and its wholly-owned subsidiaries were prepared in accordance with U.S. GAAP. The consolidated financial statements include the accounts of all subsidiaries. All intercompany balances and transactions have been eliminated.
Use of Estimates	The preparation of the financial statements in accordance with U.S. GAAP requires management to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and the related disclosures at the date of the financial statements and during the reporting period. Significant estimates are used for, but are not limited to, assumptions used to estimate its ability to continue as a going concern; revenue recognition; deferred tax assets, deferred tax liabilities and valuation allowances; beneficial conversion features; fair value of stock options, preferred stock, and warrants; and various accruals. Management evaluates its estimates on an ongoing basis. Actual results and outcomes could differ materially from management’s estimates, judgments, and assumptions.
Foreign Currency Translation	Foreign Currency Translation The financial statements of the Company’s foreign subsidiaries are translated from local currency into reporting currency, which is U.S. dollars, using the current exchange rate at the balance sheet date for assets and liabilities, and the weighted average exchange rate prevailing during the period for revenues and expenses. The functional currency for Pieris’ foreign subsidiaries is considered to be the local currency for each entity and, accordingly, translation adjustments for these subsidiaries are included in accumulated other comprehensive loss within stockholders’ equity. Realized and unrealized gains and losses resulting from foreign currency transactions denominated in currencies other than the functional currency are reflected as other (expense) income, net in the consolidated statements of operations. Foreign currency gains and losses on available-for-sale investment transactions are recorded to other comprehensive income on the Company's balance sheet per Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 830, Foreign Currency Matters.
Cash, Cash Equivalents and Investments	Cash, Cash Equivalents and Investments The Company determines the appropriate classification of its investments at the time of purchase. All liquid investments with original maturities of 90 days or less from the purchase date and for which there is an active market are considered to be cash equivalents. The Company’s investments are comprised of money market, asset backed securities, government treasuries, and corporate bonds that are classified as available-for-sale in accordance with FASB ASC 320, Investments—Debt and Equity Securities. The Company classifies investments available to fund current operations as current assets on its balance sheets. Available-for-sale investments are recorded at fair value, with unrealized gains or losses included in accumulated other comprehensive loss on the Company’s balance sheets. Realized gains and losses are determined using the specific identification method and are included as a component of other income. The Company reviews investments for other-than-temporary impairment whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other-than temporary, the Company considers its intent to sell, or whether it is more likely than not that the Company will be required to sell the investment before recovery of the investment’s amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, the severity and the duration of the impairment, and changes in value subsequent to period end.
Concentration of Credit Risk and Off-Balance Sheet Risk	Concentration of Credit Risk and Off-Balance Sheet Risk The Company has no financial instruments with off‑balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that subject Pieris to concentrations of credit risk include cash and cash equivalents, investments, and accounts receivable. The Company’s cash, cash equivalents, and investments are held in accounts with financial institutions that management believes are creditworthy. The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. Accounts receivable primarily consist of amounts due under strategic partnership and other license agreements with major multi-national pharmaceutical companies for which the Company does not obtain collateral.
Fair Value Measurement	Fair Value Measurement The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures, or ASC 820, established a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported or disclosed fair value of the financial instruments and is not a measure of the investment credit quality. Fair value measurements are classified and disclosed in one of the following three categories: •Level 1 inputs are quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. •Level 2 utilizes quoted market prices in markets that are not active, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. •Level 3 inputs are unobservable inputs for the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Financial instruments measured at fair value on a recurring basis include cash equivalents and investments (Note 5). An entity may elect to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected will be reported in net loss. The Company did not elect to measure any additional financial instruments or other items at fair value.
Fair Values of Financial Instruments	Fair Values of Financial Instruments The fair value of cash, accounts receivable, and accounts payable approximates the carrying value of these financial instruments because of the short-term nature of any maturities. The Company determines the estimated fair values of other financial instruments, using available market information and valuation methodologies, primarily input from independent third party pricing sources.
Accounts Receivable	Accounts Receivable Accounts receivable are recorded net of allowances for doubtful accounts and represent amounts due from strategic partners. The Company monitors and evaluates collectability of receivables on an ongoing basis and considers whether an allowance for doubtful accounts is necessary. The Company determined that no such reserve is needed as of December 31, 2020 and 2019. Historically, Pieris has not had collectability issues.
Property and Equipment	Property and Equipment Property and equipment are recorded at acquisition cost, less accumulated depreciation and impairment. Depreciation on property and equipment is calculated using the straight-line method over the remaining estimated useful lives of the assets. Maintenance and repairs to these assets are charged to expenses as occurred. During the year ended December 31, 2020, the Company added material assets related to the February 2020 move to a new research and development facility in Hallbergmoos, Germany. The Company expanded its presentation of property and equipment to be more descriptive and updated the useful life for one asset category on a prospective basis. The disclosures for property and equipment, net as of December 31, 2019 have been reclassified to conform with the current period presentation.
Impairment of Long-lived Assets	Impairment of Long-lived Assets The Company reviews its long-lived assets to be held and used for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. The Company evaluates the realizability of its long-lived assets based on profitability and cash flow expectations for the related asset. Any write-downs are treated as permanent reductions in the carrying amount of the assets. The Company believes that, as of each of the balance sheets presented, none of the Company’s long-lived assets were impaired.
Revenue Recognition	Revenue Recognition Pieris has entered into several licensing agreements with collaboration partners for the development of Anticalin therapeutics against a variety of targets. The terms of these agreements provide for the transfer of multiple goods or services which may include: (i) licenses, or options to obtain licenses, to Pieris’s Anticalin technology and/or specific programs and (ii) research and development activities to be performed on behalf of or with a collaborative partner. Payments to Pieris under these agreements may include upfront fees (which include license and option fees), payments for research and development activities, payments based upon the achievement of certain milestones, and royalties on product sales. There are no performance, cancellation, termination or refund provisions in any of the arrangements that could result in material financial consequences to Pieris. Effective January 1, 2019, the Company adopted ASC 606. The standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The Company elected the modified retrospective approach and applied it to contracts not completed at the date of adoption. Therefore, comparative prior periods have not been adjusted. The reported results for 2019 reflect the application of ASC 606 guidance while the reported results for 2018 were prepared under the guidance of FASB ASC Topic 605, Revenue Recognition, or ASC 605. Furthermore, the Company adopted the contract modification practical expedient set forth in ASC 606 and will reflect the aggregate effect of all modifications that occurred before January 1, 2019 when identifying the satisfied and unsatisfied performance obligations, determining the transaction price and allocating the transaction price to the satisfied and unsatisfied performance obligations. See Note 3 for additional details on these arrangements. Collaborative Arrangements The Company considers the nature and contractual terms of an arrangement and assess whether the arrangement involves a joint operating activity pursuant to which it is an active participant and exposed to significant risks and rewards with respect to the arrangement. If the Company is an active participant and exposed to the significant risks and rewards with respect to the arrangement, it accounts for these arrangements pursuant to ASC 808, Collaborative Arrangements, or ASC 808, and applies a systematic and rational approach to recognize revenue. The Company classifies payments received as revenue and payments made as a reduction of revenue in the period in which they are earned. In November 2018, the FASB issued ASU 2018-18, which makes targeted improvements to U.S. GAAP for collaborative arrangements, including: clarification that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606, Revenue from Contracts with Customers, or ASC 606, when the collaborative arrangement participant is a customer in the context of a unit of account; adding unit-of-account guidance in ASC 808 to align with the guidance in ASC 606; and a requirement that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under ASC 606 is precluded if the collaborative arrangement participant is not a customer. The guidance per ASU 2018-18 was adopted retrospectively to the date of initial application of ASC 606. The Company adopted ASU 2018-18 in the first quarter of 2020. The adoption of this standard did not have a material impact on the Company’s condensed consolidated financial statements; however, revenue recognized under a collaborative arrangement involving a participant that is not a customer (Collaboration revenue) is now presented separately from Customer revenue. Revenue from Contracts with Customers In accordance with ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps: 1) identify the customer contract; 2) identify the contract’s performance obligations; 3) determine the transaction price; 4) allocate the transaction price to the performance obligations; and 5) recognize revenue when or as a performance obligation is satisfied. The Company evaluates all promised goods and services within a customer contract and determines which of such goods and services are separate performance obligations. This evaluation includes an assessment of whether the good or service is capable of being distinct and whether the good or service is separable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property and the capabilities of the customer to develop the intellectual property on their own or whether the required expertise is readily available. Licensing arrangements are analyzed to determine whether the promised goods or services, which often include licenses, research and development services and governance committee services, are distinct or whether they must be accounted for as part of a combined performance obligation. If the license is considered not to be distinct, the license would then be combined with other promised goods or services as a combined performance obligation. If the Company is involved in a governance committee, it assesses whether its involvement constitutes a separate performance obligation. When governance committee services are determined to be separate performance obligations, the Company determines the fair value to be allocated to this promised service. Certain contracts contain optional and additional items, which are considered marketing offers and are accounted for as separate contracts with the customer if such option is elected by the customer, unless the option provides a material right which would not be provided without entering into the contract. An option that is considered a material right is accounted for as a separate performance obligation. The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. A contract may contain variable consideration, including potential payments for both milestone and research and development services. For certain potential milestone payments, the Company estimates the amount of variable consideration by using the most likely amount method. In making this assessment, the Company evaluates factors such as the clinical, regulatory, commercial and other risks that must be overcome to achieve the milestone. Each reporting period the Company re-evaluates the probability of achievement of such variable consideration and any related constraints. Pieris will include variable consideration, without constraint, in the transaction price to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. For potential research and development service payments, the Company estimates the amount of variable consideration by using the expected value method, including any approved budget updates arising from additional research or development services. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price among the performance obligations on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct good or service that forms part of a single performance obligation. The Company allocates the transaction price based on the estimated standalone selling price of the underlying performance obligations or in the case of certain variable consideration to one or more performance obligations. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs to complete the respective performance obligation. Certain variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated to each performance obligation are consistent with the amount the Company would expect to receive for each performance obligation. When a performance obligation is satisfied, revenue is recognized for the amount of the transaction price, excluding estimates of variable consideration that are constrained, that is allocated to that performance obligation on a relative standalone selling price basis. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement. For performance obligations consisting of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non- refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. Milestones and Royalties The Company aggregates milestones into four categories (i) research milestones, (ii) development milestones, (iii) commercial milestones and (iv) sales milestones. Research milestones are typically achieved upon reaching certain success criteria as defined in each agreement related to developing an Anticalin protein against the specified target. Development milestones are typically reached when a compound reaches a defined phase of clinical research or passes such phase, or upon gaining regulatory approvals. Commercial milestones are typically achieved when an approved pharmaceutical product reaches the status for commercial sale, including regulatory approval. Sales milestones are certain defined levels of net sales by the licensee, such as when a product first achieves global sales or annual sales of a specified amount. There is uncertainty that the events to obtain the research and development milestones will be achieved given the nature of clinical development and the stage of the Company’s technology. The Company has thus determined that all research and development milestones will be constrained until it is deemed probable that a significant revenue reversal will not occur. For revenues from research and development milestones, payments will be recognized consistent with the recognition pattern of the performance obligation to which they relate. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Commercial milestones and sales royalties are determined by sales or usage-based thresholds and will be accounted for under the royalty recognition constraint as constrained variable consideration. Contract Balances The Company recognizes a contract asset when the Company transfers goods or services to a customer before the customer pays consideration or before payment is due, excluding any amounts presented as a receivable (i.e., accounts receivable). A contract asset is an entity’s right to consideration in exchange for goods or services that the entity has transferred to a customer. The contract liabilities (i.e., deferred revenue) primarily relate to contracts where the Company has received payment but has not yet satisfied the related performance obligations. In the event of an early termination of a collaboration agreement, any contract liabilities would be recognized in the period in which all Company obligations under the agreement have been fulfilled. Costs to Obtain and Fulfill a Contract with a Customer Certain costs to obtain customer contracts, including success-based fees paid to third-party service providers, and costs to fulfill customer contracts are capitalized in accordance with FASB ASC 340, Other Assets and Deferred Costs, or ASC 340. These costs are amortized to expense on a systemic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. The Company will expense the amortization of costs to obtain customer contracts to general and administrative expense and costs to fulfill customer contracts to research and development expense.
Research and Development	Research and Development Research and development expenses are charged to the statement of operations as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, facilities costs, pre-clinical and clinical costs, contract services, consulting, depreciation and amortization expense, and other related costs. Costs associated with acquired technology, in the form of upfront fees or milestone payments, are charged to research and development expense as incurred.
Income Taxes	Income Taxes The Company applies ASC Topic 740 Income Taxes, which established financial accounting and reporting requirements for the effects of income taxes that result from the Company’s activities during the current and preceding years. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, and operating losses and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted statutory tax rates expected to apply to taxable income in the jurisdictions and years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Where the Company determines that it is more likely than not that some portion or all of the deferred tax assets will not be realized in the future, the deferred tax assets are reduced by a valuation allowance. The Company records interest related and penalties related to uncertain tax positions as part of income tax expense. The Tax Cuts and Jobs Act (TCJA) subjects a U.S. shareholder to tax on global-intangible low tax income (GILTI) earned by certain foreign subsidiaries. The Company has made an accounting policy election to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only.
Stock-based Compensation	Stock-based Compensation The Company measures share-based payments in accordance with ASC Topic 718, Stock Compensation. Pieris records its stock-based compensation expense over the requisite service period and records forfeitures as they occur. Determining the appropriate fair value model and related assumptions requires judgment, including estimating share price volatility and expected terms of the awards. For employee options, the fair value measurement date is generally on the date of grant and the related compensation expense is recognized on a straight-line basis over the requisite period of the awards, less expense for actual forfeitures. The Company uses the Black-Scholes option pricing model to determine the estimated fair value for stock-based awards. Option-pricing models require the input of various subjective assumptions, including the option’s expected life, expected dividend yield, price volatility, risk free interest rate and forfeitures of the underlying stock. Due to the limited operating history of the Company as a public entity and a lack of company specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected term of the stock-based awards. The Company computes historical volatility data using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Due to the lack of Company specific historical option activity, the Company has estimated the expected term of its employee stock options using the “simplified” method, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. The expected term for non-employee awards is the remaining contractual term of the option. The risk-free interest rates are based on the U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The Company has never paid, and does not expect to pay dividends in the foreseeable future. All excess tax benefits and tax deficiencies are recorded as income tax expense or benefit in the Company's statement of operations and comprehensive loss.
Leases	Leases In February 2016, the FASB issued ASU No. 2016-2, Leases (Topic 842), or ASC 842. Under the amendments in ASC 842, lessees will be required to recognize (i) a lease liability, which is a lessees obligation to make lease payments arising from a lease, measured on a discounted basis; and (ii) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term for all leases (with the exception of short-term leases) at the commencement date. The Company adopted ASC 842 in the fourth quarter of 2019 using the required modified retrospective approach, effective January 1, 2019. The Company elected the package of practical expedients permitted under the transition guidance within the new standard expedients which allows the Company to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of its existing leases as of the transition date, and the treatment of initial direct costs. In addition, the Company elected the practical expedient not to apply the recognition requirements in the lease standard to short-term leases (a lease that at commencement date has a lease term of 12 months or less and does not contain a purchase option that it is reasonably certain to exercise) and the practical expedient to not separate lease and non-lease components for all asset classes. Any variable components of lease costs are excluded from lease payments and are recognized in the period incurred. The Company determines if an arrangement is a lease at inception. The Company’s contracts are determined to contain a lease within the scope of ASC 842 when all of the following criteria based on the specific circumstances of the arrangement are met: (1) there is an identified asset for which there are no substantive substitution rights; (2) the Company has the right to obtain substantially all of the economic benefits from the identified asset; and (3) the Company has the right to direct the use of the identified asset. At the commencement date, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of future lease payments over the expected lease term. The Company’s lease agreements do not provide an implicit rate. As a result, the Company utilizes an estimated incremental borrowing rate to discount lease payments, which is based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term and based on observable market data points. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or lease incentives received. Operating lease cost is recognized over the expected term on a straight-line basis. The Company typically only includes an initial lease term in its assessment of a lease agreement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew. The expected lease term includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option. Assumptions made by the Company at the commencement date are re-evaluated upon occurrence of certain events, including a lease modification. A lease modification results in a separate contract when the modification grants the lessee an additional right of use not included in the original lease and when lease payments increase commensurate with the standalone price for the additional right of use. When a lease modification results in a separate contract, it is accounted for in the same manner as a new lease.
Contingencies	Contingencies Accruals are recorded for loss contingencies when it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. The Company evaluates, on a quarterly basis, developments in legal proceedings and other matters that could cause an increase or decrease in the amount of the liability that has been accrued previously. Considering facts known at the time of the assessment, the Company determines whether potential losses are considered reasonably possible or probable and whether they are estimable. Based upon this assessment, the Company carries out an evaluation of disclosure requirements and considers possible accruals in the financial statements.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise where separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions on how to allocate resources and assess performance. The Company operates as a single segment dedicated to the discovery and development of biotechnological applications and the Company’s chief operating decision maker, or CODM, makes decisions based on the Company as a whole. The Company has determined that its CODM is its Chief Executive Officer.
Earnings per Share	Earnings per Share Basic earnings per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average shares outstanding during the period, without consideration for common stock equivalents. Diluted earnings per share attributable to common stockholders is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share attributable to common stockholders' calculation, preferred stock, stock options, unvested restricted stock, and warrants are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders, as their effect would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share were the same for all periods presented.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements, or ASU 2016-13. ASU 2016-13 significantly changes the impairment model for most financial assets and certain other instruments. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value, and requires the reversal of previously recognized credit losses if fair value increases. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial asset(s) to present the net carrying value at the amount expected to be collected on the financial asset. Subsequently, in November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, which clarifies codification and corrects unintended application of the guidance. In November 2019, the FASB issued ASU No. 2019-11, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, which clarifies or addresses specific issues about certain aspects of ASU 2016-13. In November 2019 the FASB also issued ASU No. 2019-10, Financial Instruments-Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, which delays the effective date of ASU 2016-13 by three years for certain smaller reporting companies such as the Company. The guidance in ASU 2016-13 is effective for the Company for financial statements issued for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years, with early adoption permitted. The Company is still evaluating the impact of the adoption of this standard. The Company has considered other recent accounting pronouncements and concluded that they are either not applicable to the business, or that the effect is not expected to be material to the unaudited consolidated financial statements as a result of future adoption.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Property and Equipment, Useful Lives

The estimated useful life of the different groups of property and equipment is as follows:


Asset Classification						Estimated useful life (in years)
Leasehold improvements						shorter of useful life or remaining life of the lease
Laboratory furniture and equipment						8 - 14
Office furniture and equipment						5 - 13
Computer and equipment						3 - 7

Property and equipment are summarized as follows (in thousands):


	Years Ended December 31,
	2020		2019
Laboratory equipment	$	11,188	$	11,635
Office furniture and equipment	2,120		479
Computer equipment	394		245
Leasehold improvements	14,159		10,710
Property and equipment at cost	27,861		23,069
Accumulated depreciation	(5,815)		(3,567)
Property and equipment, net	$	22,046	$	19,502

Schedule of Impact of Adopting ASC 808

This change has been reflected in the consolidated statement of operations and the 2019 amounts were adjusted to conform to ASC 808 as follows:


	Twelve Months Ended December 31, 2019
	As reported pre-adoption		ASC 808 Adoption Adjustment		As reported post-adoption
Customer revenue	$	43,646	$	(11,581)	$	32,065
Collaboration revenue	2,633		11,581		14,214
Total Revenue	$	46,279	$	—	$	46,279

Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Revenue from Contract with Customer [Abstract]

Schedule of Recognized Revenues

During the years ended December 31, 2020 and 2019, respectively, the Company recognized revenue from the following strategic partnerships and other license agreements (in thousands):


	Years Ended December 31,
	2020		2019
AstraZeneca	$	8,308	$	25,828
Seagen	9,702		2,493
Servier	11,313		15,048
Other	—		2,910
Total Revenue	$	29,323	$	46,279

Schedule of Potential Milestone Payments

Under the Company´s existing strategic partnerships and other license agreements, the Company could receive the following potential milestone payments (in millions) as of December 31, 2020:


	Research, Development, Regulatory & Commercial Milestones		Sales Milestones
AstraZeneca	$	1,111	$	960
Servier	247		221
Seagen	764		450


Total potential milestone payments	$	2,122	$	1,631

Cash, Cash Equivalents and Investments (Tables)

12 Months Ended

Dec. 31, 2020

Cash and Cash Equivalents [Abstract]

Schedule of Cash Equivalents and Investments Carried at Fair Value

The following table presents the cash equivalents and investments carried at fair value in accordance with the hierarchy defined in Note 2 at December 31, 2020 and 2019 (in thousands):


	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2020
Money market funds, included in cash equivalents	$	63,951	$	63,951	$	—	$	—



Total	$	63,951	$	63,951	$	—	$	—


	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2019
Money market funds, included in cash equivalents	$	47,384	$	47,384	$	—	$	—

Investments - US treasuries	5,300		5,300		—		—
Investments - Asset-backed securities	7,950		—		7,950		—
Investments - Corporate bonds	28,644		—		28,644		—
Total	$	89,278	$	52,684	$	36,594	$	—

Schedule of Cash Equivalents and Invesments

Investments at December 31, 2019 consist of the following (in thousands):


	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses		Fair Value
Investments
US treasuries	46-182	$	5,293	$	25	$	(18)	$	5,300
Asset-backed securities	49-106	7,962		12		(24)		7,950
Corporate bonds	2-204	28,709		20		(85)		28,644
Total		$	41,964	$	57	$	(127)	$	41,894

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

The estimated useful life of the different groups of property and equipment is as follows:


Asset Classification						Estimated useful life (in years)
Leasehold improvements						shorter of useful life or remaining life of the lease
Laboratory furniture and equipment						8 - 14
Office furniture and equipment						5 - 13
Computer and equipment						3 - 7

Property and equipment are summarized as follows (in thousands):


	Years Ended December 31,
	2020		2019
Laboratory equipment	$	11,188	$	11,635
Office furniture and equipment	2,120		479
Computer equipment	394		245
Leasehold improvements	14,159		10,710
Property and equipment at cost	27,861		23,069
Accumulated depreciation	(5,815)		(3,567)
Property and equipment, net	$	22,046	$	19,502

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2020

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	Years Ended December 31,
	2020		2019
Compensation expense	$	2,759	$	2,870
Research and development fees	2,001		1,048
Accrued accounts payable	1,220		4,251
Lease liabilities	1,030		733
Accrued license obligations	358		62
Audit and tax fees	128		522
Other current liabilities	235		458
Total	$	7,731	$	9,944

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Loss before Income Taxes

The Company reported a loss before income taxes consisting of the following (in thousands):


	Years Ended December 31,
	2020		2019
Domestic	$	(12,134)	$	(12,063)
Foreign	(24,932)		(13,406)
Loss before income taxes	$	(37,066)	$	(25,469)

Schedule of Components of (Benefit) Provision for Income Taxes

The components of the provision for income taxes are as follows (in thousands):


	Years Ended December 31,
	2020		2019
Current:
Federal	$	—	$	—
State	—		—
Foreign	164		—
Total current	164		—
Deferred:
Federal	—		—
State	—		—
Foreign	—		—
Total deferred	—		—
Provision for income taxes	$	164	$	—

Schedule of Reconciliation of Effective Tax Rate

The reconciliation of the federal statutory rate to the Company’s effective tax rate is as follows:


	2020		2019
Federal income tax rate	21.0	%	21.0	%

Foreign rate differential	1.9		1.9
State tax, net of federal benefit	1.9		2.6
US tax on foreign income	—		(1.2)
Share-based awards compensation	(3.8)		(2.5)
Permanent items	(2.4)		(1.0)
Other	(0.4)		0.8
Rate change - trade tax NOL	—		(6.4)
Change in valuation allowance	(18.7)		(15.2)
Effective income tax rate	(0.5)	%	—	%

Schedule of Components of Deferred Tax Assets and Liabilities


	Years Ended December 31,
	2020		2019
Deferred tax assets:
Net operating loss carryforwards	$	39,175	$	30,455
Share-based awards compensation	2,913		2,705
Accrued expenses	230		328
Depreciation and other	297		53

Unrealized foreign currency	771		90
Lease liability	4,582		4,378
Total deferred tax assets	47,968		38,009
Deferred tax liabilities:
Right-of-use asset	(4,235)		(4,043)


Total deferred tax liabilities	(4,235)		(4,043)
Less: valuation allowance:	(43,733)		(33,966)
Net deferred tax asset	$	—	$	—

Schedule of Reconciliation of Unrecognized Tax Benefits Excluding Impact of Interest and Penalties


Unrecognized tax benefits at December 31, 2019	$	6,032
Currency translation adjustment	103
Unrecognized tax benefits at December 31, 2020	$	6,135

Stock and Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Fair Value Assumptions

The Company estimates the fair value of each stock award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:


	Years Ended December 31,
	2020	2019
Risk free interest rate	0.33% - 1.53%	1.41% - 2.60%
Expected term (in years)	5.00 - 5.73	5 - 5.73
Dividend yield	—	—
Expected volatility	70.0% - 75.8%	81.7% - 81.8%

The fair value of shares expected to be purchased under the 2018 ESPP using the Black-Scholes model with the following assumptions:


	Years Ended December 31,
	2020	2019
Risk free interest rate	0.10% - 0.18%	2.48	%
Expected term (in years)	0.5 years	0.5 years
Dividend yield	—	—
Expected volatility	74.36% - 120.89%	57.57	%

Schedule of Stock Option Activity

The following table summarizes stock option activity for employees and non-employees:


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2019	8,259,915	$	3.60		$	7,987
Granted	2,311,481	3.15			—
Exercised	149,406	1.95			97
Canceled	830,867	4.58			101
Outstanding, December 31, 2020	9,591,123	$	3.44	6.84 years	$	2,303
Vested or expected to vest, December 31, 2020	9,591,123	$	3.44	6.84 years	$	2,303
Exercisable, December 31, 2020	6,123,532	$	3.28	5.81 years	$	2,269

The following table summarizes stock option activity for these inducement options (in thousands):


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2019	1,200,000	$	4.36		$	130
Granted	—	$	—		$	—
Canceled or Expired	779,687	$	4.01		$	—
Outstanding, December 31, 2020	420,313	$	5.00	8.12 years	$	—
Vested or expected to vest	420,313	$	5.00	8.12 years	$	—
Exercisable, December 31, 2020	214,063	$	5.34	7.60 years	$	—

Schedule of Stock-Based Compensation Expense

Total stock-based compensation expense is recorded in operating expenses based upon the functional responsibilities of the individuals holding the respective options as follows (in thousands):


	Years Ended December 31,
	2020		2019
Research and development	$	2,394	$	2,446
General and administrative	2,696		2,928
Total stock-based compensation	$	5,090	$	5,374

Leases (Tables)

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Lease Costs, Term and Discount Rate

The following table summarizes operating lease costs included in operating expenses (in thousands):


	Years Ended December 31,
	2020		2019

Operating lease costs	$	1,509	$	1,524
Variable lease costs (1)	708		293
Total lease cost	$	2,217	$	1,817
(1) Variable lease costs include certain additional charges for operating costs, including insurance, maintenance, taxes, utilities, and other costs incurred, which are billed based on both usage and as a percentage of the Company’s share of total square footage.

The following table summarizes the weighted-average remaining lease term and discount rate:


	As of December 31,
	2020		2019
Weighted-average remaining lease term (years)	11.4		12.1
Weighted-average discount rate	10.5	%	10.5	%

Maturities of Operating Lease Liabilities

As of December 31, 2020, the maturities of the Company’s operating lease liabilities and future minimum lease payments were as follows (in thousands):


	Total
2021	$	2,662
2022	2,458
2023	2,424
2024	2,424
2025	2,424
Thereafter	14,556
Total undiscounted lease payments	26,948
Less: present value adjustment	(9,986)
Present value of lease liabilities	16,962

Corporate Information - Narrative (Details) - USD ($) $ in Thousands			1 Months Ended		12 Months Ended
	Mar. 29, 2021	Mar. 24, 2021	Mar. 31, 2021	Nov. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2014
Subsequent Event [Line Items]
Cash and cash equivalents					$ 70,436	$ 62,260
Revenues					29,323	46,279
Net loss					(37,230)	(25,469)
Accumulated deficit					(211,406)	(174,176)
Private Placement
Subsequent Event [Line Items]
Net proceeds from underwritten public offering				$ 31,000
Seagen
Subsequent Event [Line Items]
Revenues					9,702	2,493
Seagen \| Subsequent Event \| Private Placement
Subsequent Event [Line Items]
Net proceeds from underwritten public offering		$ 13,000	$ 13,000
AstraZeneca
Subsequent Event [Line Items]
Revenues					$ 8,308	$ 25,828
AstraZeneca \| Subsequent Event
Subsequent Event [Line Items]
Revenues			13,000
AstraZeneca \| Subsequent Event \| Private Placement
Subsequent Event [Line Items]
Net proceeds from underwritten public offering	$ 10,000		$ 10,000
Pieris Pharmaceuticals GmbH
Subsequent Event [Line Items]
Ownership interest acquired (as a percent)							100.00%

Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Allowance for doubtful accounts	$ 0	$ 0

Summary of Significant Accounting Policies - Estimated Useful Life of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Laboratory furniture and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	8 years
Laboratory furniture and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	14 years
Office furniture and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Office furniture and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	13 years
Computer and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Computer and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years

Summary of Significant Accounting Policies - Impact of Adopting ASC 808 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue	$ 29,323	$ 46,279
Customer revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		32,065
Collaboration revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		14,214
As reported pre-adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		46,279
As reported pre-adoption \| Customer revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		43,646
As reported pre-adoption \| Collaboration revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		2,633
ASC 808 Adoption Adjustment \| Accounting Standards Update 2018-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		0
ASC 808 Adoption Adjustment \| Customer revenue \| Accounting Standards Update 2018-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		(11,581)
ASC 808 Adoption Adjustment \| Collaboration revenue \| Accounting Standards Update 2018-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Revenue		$ 11,581

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

+ Details

Revenue - Revenue from Strategic Partnerships and Other License Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total Revenue	$ 29,323	$ 46,279
AstraZeneca
Disaggregation of Revenue [Line Items]
Total Revenue	8,308	25,828
Seagen
Disaggregation of Revenue [Line Items]
Total Revenue	9,702	2,493
Servier
Disaggregation of Revenue [Line Items]
Total Revenue	11,313	15,048
Other
Disaggregation of Revenue [Line Items]
Total Revenue	$ 0	$ 2,910

- Definition

+ References

+ Details

Revenue - Potential Milestone Payments (Details) - Strategic Partnerships and Other License Agreements - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments	$ 2,122
Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments		$ 1,631
AstraZeneca \| Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments	1,111
AstraZeneca \| Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments		960
Servier \| Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments	247
Servier \| Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments		221
Seagen \| Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments	$ 764
Seagen \| Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Total potential milestone payments		$ 450

Revenue - Narrative (Details) $ / shares in Units, € in Millions														1 Months Ended								3 Months Ended		12 Months Ended
	Mar. 29, 2021 USD ($) $ / shares shares	Mar. 24, 2021 USD ($) $ / shares shares	Feb. 08, 2018 USD ($) researchProgram license swapOption performanceObligation program	May 02, 2017 performanceObligation	May 02, 2017 USD ($) performanceObligation	May 02, 2017 researchProgram performanceObligation	May 02, 2017 license performanceObligation	May 02, 2017 performanceObligation	May 02, 2017 performanceObligation protein	May 02, 2017 performanceObligation leaseAgreement	Feb. 27, 2017 USD ($)	Jan. 04, 2017 USD ($) license performanceObligation protein collaborationProduct bispecificTherapeuticProgram preclinicalMilestone extensionOption	Jan. 04, 2017 EUR (€) license performanceObligation protein collaborationProduct bispecificTherapeuticProgram preclinicalMilestone extensionOption	Mar. 31, 2021 USD ($)	Feb. 28, 2021	Feb. 29, 2020 program collaborationProduct	Nov. 30, 2019 USD ($) $ / shares shares	Feb. 28, 2019 USD ($)	Feb. 28, 2019 EUR (€)	Dec. 31, 2018 USD ($) preclinicalMilestone	Dec. 31, 2018 EUR (€) preclinicalMilestone	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	May 02, 2017 collaborationProduct
Disaggregation of Revenue [Line Items]
Revenue recognized from contract with customer																								$ 15,000,000.0
Revenues																								29,323,000	$ 46,279,000
Deferred revenues, current portion																								12,627,000	11,256,000
Deferred revenue, net of current portion																								35,900,000	47,258,000
Number of technology licenses (in licenses) \| leaseAgreement										5
Number of separate performance obligations (in performance obligations) \| performanceObligation												1	1
Additions to contract with customer, liability																								1,600,000
Private Placement
Disaggregation of Revenue [Line Items]
Shares of common stock issued (shares) \| shares																	9,014,960
Net proceeds from private placement																	$ 31,000,000.0
Issue price per share (USD per share) \| $ / shares																	$ 3.55
Seagen
Disaggregation of Revenue [Line Items]
Number of performance obligations (in performance obligations) \| performanceObligation			3
Remaining performance obligation																								20,700,000
Revenues																								9,702,000	2,493,000
Deferred revenues, current portion																								5,700,000
Deferred revenue, net of current portion																								11,800,000
Seagen \| Subsequent Event \| Private Placement
Disaggregation of Revenue [Line Items]
Shares of common stock issued (shares) \| shares		3,706,174
Net proceeds from private placement		$ 13,000,000.0												$ 13,000,000.0
Issue price per share (USD per share) \| $ / shares		$ 3.51
AstraZeneca
Disaggregation of Revenue [Line Items]
Remaining performance obligation																								25,400,000
Revenues																								8,308,000	25,828,000
Deferred revenues, current portion																								900,000
Deferred revenue, net of current portion																								18,600,000
Research collaboration agreement term				5 years
AstraZeneca \| Subsequent Event
Disaggregation of Revenue [Line Items]
Revenues														13,000,000.0
AstraZeneca \| Subsequent Event \| Private Placement
Disaggregation of Revenue [Line Items]
Shares of common stock issued (shares) \| shares	3,584,230
Net proceeds from private placement	$ 10,000,000.0													$ 10,000,000.0
Issue price per share (USD per share) \| $ / shares	$ 2.79
Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Number of performance obligations (in performance obligations) \| performanceObligation												10	10
Remaining performance obligation																								11,600,000
Revenue recognized from contract with customer																							$ 7,100,000
Revenues																								11,313,000	$ 15,048,000
Research term extension period																12 months
Number of preclinical stage programs (in programs) \| program																2
Period to complete remaining obligations on programs																60 days
Deferred revenues, current portion																								6,000,000.0
Deferred revenue, net of current portion																								5,500,000
Number of novel proteins (in proteins) \| protein												1	1
Number of research programs (in research programs) \| program																5
Capitalized contract cost, net																								200,000
Amortization of capitalized contract costs																								100,000
Number of research programs \| bispecificTherapeuticProgram												3	3
Number of separate performance obligations (in performance obligations) \| performanceObligation												2	2
Number of combined performance obligations (in obligations) \| performanceObligation												2	2
Les Laboratoires Servier and Institut de Recherches Internationales Servier \| Subsequent Event
Disaggregation of Revenue [Line Items]
Research term extension period															12 months
Les Laboratoires Servier and Institut de Recherches Internationales Servier \| Research and development services
Disaggregation of Revenue [Line Items]
Research collaboration agreement term												3 years	3 years
Number of preclinical milestones (in preclinical milestones) \| preclinicalMilestone												2	2							1	1
ASKA Pharmaceutical Co. Ltd.
Disaggregation of Revenue [Line Items]
Revenue recognized from contract with customer																								0
Capitalized contract cost, net											$ 300,000
Evaluation period											60 days
Upfront option payment received											$ 2,750,000
License and collaboration agreement \| Seagen
Disaggregation of Revenue [Line Items]
Number of research programs (in research programs) \| researchProgram			3
Period after effective date agreements may be terminated			12 months
Contract termination advance notice period			90 days
Agreement termination advance notice period if marketing approval obtained			180 days
Agreement termination notice period upon material breach by the Company			90 days
Contract termination due to material breach, additional notice period if the breach is not susceptible			90 days
Number of licenses (in licenses) \| license			3
Number of swap options (in swap options) \| swapOption			2
Number of performance obligations (in performance obligations) \| performanceObligation			6
License and collaboration agreement \| AstraZeneca
Disaggregation of Revenue [Line Items]
Period after effective date agreements may be terminated				12 months
Contract termination advance notice period				90 days
Agreement termination advance notice period if marketing approval obtained				180 days
Agreement termination notice period upon material breach by the Company				180 days
Contract termination due to material breach, additional notice period if the breach is not susceptible				180 days
Number of performance obligations (in performance obligations) \| performanceObligation								16
Number of novel proteins (in proteins) \| protein									4
Agreement termination notice period upon breach of payment obligations by the Company				30 days
Period of license performance obligation				12 months
License and collaboration agreement \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Number of licenses (in licenses) \| license												5	5
Number of performance obligations (in performance obligations) \| performanceObligation												4	4
Number of collaboration products (in collaboration products) \| collaborationProduct												2	2
Number of research programs (in research programs) \| bispecificTherapeuticProgram												5	5
Number of research programs \| bispecificTherapeuticProgram												5	5
Collaborative arrangement \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Period after effective date agreements may be terminated												12 months	12 months
Contract termination advance notice period												180 days	180 days
Revenue recognized from contract with customer																		$ 1,700,000	€ 1.5	$ 600,000	€ 0.5
Number of research and development licenses (in licenses) \| license												4	4
Co-development collaboration product \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Number of collaboration products (in collaboration products) \| collaborationProduct																1
Servier developed collaboration product \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Number of collaboration products (in collaboration products) \| collaborationProduct																1
Other arrangement \| Seagen
Disaggregation of Revenue [Line Items]
Number of research programs (in research programs) \| researchProgram			2
Platform technology license \| Seagen
Disaggregation of Revenue [Line Items]
Number of performance obligations (in performance obligations) \| performanceObligation			3
Number of target programs (in programs) \| program			3
Antibody target swap \| Seagen
Disaggregation of Revenue [Line Items]
Number of performance obligations (in performance obligations) \| performanceObligation			2
Governance committee participation \| Seagen
Disaggregation of Revenue [Line Items]
Number of performance obligations (in performance obligations) \| performanceObligation			1
Upfront payment \| Seagen
Disaggregation of Revenue [Line Items]
Research and development services			$ 4,900,000
Deferred revenue			1,200,000,000
Upfront payment \| Seagen \| License fees
Disaggregation of Revenue [Line Items]
Revenue			$ 30,000,000.0
Upfront payment \| AstraZeneca
Disaggregation of Revenue [Line Items]
Allocable arrangement consideration					$ 45,000,000.0
Upfront payment \| Les Laboratoires Servier and Institut de Recherches Internationales Servier \| License fees
Disaggregation of Revenue [Line Items]
Revenue												$ 32,000,000.0	€ 30.0
Additional other research services \| AstraZeneca
Disaggregation of Revenue [Line Items]
Allocable arrangement consideration					4,700,000
Estimated development and manufacturing services \| Upfront payment \| AstraZeneca
Disaggregation of Revenue [Line Items]
Allocable arrangement consideration					14,200,000
Milestone payments \| Upfront payment \| Seagen
Disaggregation of Revenue [Line Items]
Revenue recognized from contract with customer																								4,200,000
Allocable arrangement consideration																						$ 5,000,000.0
Milestone payments \| Upfront payment \| AstraZeneca
Disaggregation of Revenue [Line Items]
Allocable arrangement consideration					12,500,000
Estimated phase 2a services \| Upfront payment \| AstraZeneca
Disaggregation of Revenue [Line Items]
Allocable arrangement consideration					$ 4,700,000
Agreement extension options \| Les Laboratoires Servier and Institut de Recherches Internationales Servier \| Research and development services
Disaggregation of Revenue [Line Items]
Research collaboration agreement term												1 year	1 year
Number of agreement extension options (extension options) \| extensionOption												2	2
Minimum \| License and collaboration agreement \| AstraZeneca
Disaggregation of Revenue [Line Items]
Number of collaboration products (in collaboration products) \| collaborationProduct																											2
Minimum \| Collaborative arrangement \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Agreement termination notice period upon material breach by the Company												90 days	90 days
Maximum \| License and collaboration agreement \| AstraZeneca
Disaggregation of Revenue [Line Items]
Number of collaboration products (in collaboration products)				4	4	4	4	4	4	4																	4
Number of research programs (in research programs) \| researchProgram						2
Number of research licenses (in licenses)							4			4
Maximum \| Collaborative arrangement \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Agreement termination notice period upon material breach by the Company												120 days	120 days
Accounting Standards Update 2014-09 \| AstraZeneca
Disaggregation of Revenue [Line Items]
Capitalized contract cost, net																								$ 700,000		$ 1,600,000
Capitalized contract cost in accordance with ASC 340																										1,100,000
Accounting Standards Update 2014-09 \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Capitalized contract cost, net																										$ 500,000

Collaboration agreements (Details)	Aug. 10, 2020
Lilly \| Collaborative arrangement
Other Commitments [Line Items]
Termination notice period	60 days

Cash, Cash Equivalents and Investments - Cash Equivalents and Investments Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 63,951	$ 89,278
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	63,951	47,384
US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		5,300
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		7,950
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		28,644
Quoted prices in active markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	63,951	52,684
Quoted prices in active markets (Level 1) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	63,951	47,384
Quoted prices in active markets (Level 1) \| US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		5,300
Quoted prices in active markets (Level 1) \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Quoted prices in active markets (Level 1) \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0	36,594
Significant other observable inputs (Level 2) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	0	0
Significant other observable inputs (Level 2) \| US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Significant other observable inputs (Level 2) \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		7,950
Significant other observable inputs (Level 2) \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		28,644
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0	0
Significant unobservable inputs (Level 3) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	$ 0	0
Significant unobservable inputs (Level 3) \| US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Significant unobservable inputs (Level 3) \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Significant unobservable inputs (Level 3) \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		$ 0

Cash, Cash Equivalents and Investments - Cash Equivalents and Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 41,964
Unrealized gains	57
Unrealized losses	(127)
Fair Value	41,894
US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	5,293
Unrealized gains	25
Unrealized losses	(18)
Fair Value	5,300
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	7,962
Unrealized gains	12
Unrealized losses	(24)
Fair Value	7,950
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	28,709
Unrealized gains	20
Unrealized losses	(85)
Fair Value	$ 28,644
Minimum \| US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity (in days)	46 days
Minimum \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity (in days)	49 days
Minimum \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity (in days)	2 days
Maximum \| US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity (in days)	182 days
Maximum \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity (in days)	106 days
Maximum \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity (in days)	204 days

Cash, Cash Equivalents and Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Realized gains (losses) recognized on available-for-sale investments	$ (0.6)	$ 0.3

Property and Equipment, Net - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 27,861	$ 23,069
Accumulated depreciation	(5,815)	(3,567)
Property and equipment, net	22,046	19,502
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	11,188	11,635
Office and computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	2,120	479
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	394	245
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 14,159	$ 10,710

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 2.1	$ 0.6

Accrued Expenses - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued expenses
Accrued accounts payable	$ 1,220	$ 4,251
Compensation expense	2,759	2,870
Research and development fees	2,001	1,048
Lease liabilities	1,030	733
Audit and tax fees	128	522
Other current liabilities	235	458
Accrued license obligations	358	62
Total	$ 7,731	$ 9,944

Income Taxes - Loss Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (12,134)	$ (12,063)
Foreign	(24,932)	(13,406)
Loss before income taxes	$ (37,066)	$ (25,469)

Income Taxes - Components of the Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ 0	$ 0
State	0	0
Foreign	164	0
Total current	164	0
Deferred:
Federal	0	0
State	0	0
Foreign	0	0
Total deferred	0	0
Provision for income taxes	$ 164	$ 0

Income Taxes - Reconciliation of Federal Statutory Rate to the Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income tax rate	21.00%	21.00%
Foreign rate differential	1.90%	1.90%
State tax, net of federal benefit	1.90%	2.60%
US tax on foreign income	0.00%	(1.20%)
Share-based awards compensation	(3.80%)	(2.50%)
Permanent items	(2.40%)	(1.00%)
Other	(0.40%)	0.80%
Rate change - trade tax NOL	0.00%	(6.40%)
Change in valuation allowance	(18.70%)	(15.20%)
Effective income tax rate	(0.50%)	0.00%

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 39,175	$ 30,455
Share-based awards compensation	2,913	2,705
Accrued expenses	230	328
Depreciation and other	297	53
Unrealized foreign currency	771	90
Lease liability	4,582	4,378
Total deferred tax assets	47,968	38,009
Deferred tax liabilities:
Right-of-use asset	(4,235)	(4,043)
Total deferred tax liabilities	(4,235)	(4,043)
Less: valuation allowance:	(43,733)	(33,966)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Reconciliation of Unrecognized Tax Benefits Excluding Impact of Interest and Penalties (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 6,032
Currency translation adjustment	103
Unrecognized tax benefits, ending balance	$ 6,135

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
Income Taxes - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Increase in the valuation allowance	$ (9,800,000)
Uncertain tax positions interest and penalties accrued	0	$ 0
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	27,300,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	33,200,000
Germany
Income Taxes [Line Items]
Net operating loss carryforwards	1,200,000
Germany \| Corporate income tax carryforwards
Income Taxes [Line Items]
Net operating loss carryforwards	116,600,000
Germany \| Trade tax carryforwards
Income Taxes [Line Items]
Net operating loss carryforwards	$ 115,100,000

Stockholders' equity - Narrative (Details) $ / shares in Units, $ in Thousands				1 Months Ended			3 Months Ended		12 Months Ended
	Apr. 01, 2020 shares	Mar. 31, 2020 $ / shares shares	Jan. 30, 2019 $ / shares shares	Nov. 30, 2019 USD ($) $ / shares shares	Aug. 31, 2019 USD ($)	Jun. 30, 2016 USD ($) $ / shares shares	Mar. 30, 2021 transaction partner	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Jan. 31, 2019 shares
Class of Stock [Line Items]
Common stock, shares authorized (shares)									300,000,000	300,000,000
Common stock, shares outstanding (shares)									56,002,815	55,212,437
Common stock, shares issued (shares)									56,002,815	55,212,437
Par value of common stock (USD per share) \| $ / shares									$ 0.001	$ 0.001
Preferred stock, shares authorized (shares)									10,000,000	10,000,000
Preferred stock, shares outstanding (shares)									14,429	11,429
Preferred stock, shares issued (shares)									14,429	11,429
Preferred stock, par value (USD per share) \| $ / shares									$ 0.001	$ 0.001
Cash proceeds from option exercises \| $									$ 291	$ 553
Cash proceeds from exercise of warrants \| $									$ 0	$ 246
Number of shares per unit (shares)						1
Gross sales proceeds from common stock \| $					$ 50,000
Warrant exercise period						5 years
Subsequent Event
Class of Stock [Line Items]
Number of transactions (in transactions) \| transaction							2
Number of partners (in partners) \| partner							2
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)									2,907	2,907
Preferred stock, shares issued (shares)									2,907	2,907
Preferred stock, par value (USD per share) \| $ / shares						$ 0.001
Number of shares per unit (shares)						1
Shares issued upon conversion of convertible preferred stock (shares)						1,000
Price per unit issued (USD per share) \| $ / shares						$ 2.015
Proportion of beneficial ownership (as a percent)						9.99%
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)									5,000	5,000
Preferred stock, shares issued (shares)									5,000	5,000
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)									3,522	3,522
Preferred stock, shares issued (shares)									3,522	3,522
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)									3,000	0
Preferred stock, shares issued (shares)									3,000	0
Tranche A Warrants
Class of Stock [Line Items]
Number of shares called by warrants (shares)						0.4
Exercise price (USD per share) \| $ / shares						$ 2.00
Number of warrants						1
Tranche B Warrants
Class of Stock [Line Items]
Number of shares called by warrants (shares)						0.2
Exercise price (USD per share) \| $ / shares						$ 3.00
Number of warrants						1
Common shares
Class of Stock [Line Items]
Issuance of common stock resulting from exercise of stock options (shares)									149,000	279,000
Issuance of common stock resulting from exercise convertible securities (shares)										176,000
Convertible preferred shares \| Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (shares)											5,000
Preferred stock, par value (USD per share) \| $ / shares			$ 0.001
Shares issued upon conversion of convertible preferred stock (shares)			1,000
Effective period of change to beneficial ownership limitation			61 days
Common stock ownership limit (as a percent)			9.99%
Beneficial ownership limitation (as a percent)			19.99%
Convertible preferred shares \| Series C Convertible Preferred Stock
Class of Stock [Line Items]
Shares issued upon conversion of convertible preferred stock (shares)				1,000
Common stock ownership limit (as a percent)				9.99%
Beneficial ownership limitation (as a percent)				19.99%
Convertible preferred shares \| Series D Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (shares)	3,000
Preferred stock, par value (USD per share) \| $ / shares		$ 0.001
Shares issued upon conversion of convertible preferred stock (shares)		1,000
Effective period of change to beneficial ownership limitation		61 days
Common stock ownership limit (as a percent)		9.99%
Beneficial ownership limitation (as a percent)		19.99%
Stock Exchange, Shares from Existing Shareholders \| Common shares
Class of Stock [Line Items]
Shares of common stock issued (shares)	3,000,000		5,000,000
Preferred Share Exchange
Class of Stock [Line Items]
Issue price per share (USD per share) \| $ / shares				$ 3.43
Beneficial conversion feature \| $				$ 2,800
Preferred Share Exchange \| Convertible preferred shares
Class of Stock [Line Items]
Shares of common stock issued (shares)	3,000		5,000
Private Placement
Class of Stock [Line Items]
Shares of common stock issued (shares)				9,014,960
Issue price per share (USD per share) \| $ / shares				$ 3.55
Shares of stock sold, gross consideration \| $				$ 32,000
Net proceeds from underwritten public offering \| $				$ 31,000
Number of shares per unit (shares)				1
Shares issued upon conversion of convertible preferred stock (shares)				0.001
Number of warrants included with each unit (in shares)				1
Exercise price (USD per share) \| $ / shares				$ 7.10
Period of determining volume weighted average stock price				10 days
Weighted average stock price commencing on trading day				3.00%
Effective period of change to beneficial ownership limitation				60 days
Private Placement \| Maximum
Class of Stock [Line Items]
Warrants and rights outstanding, term				5 years
Private Placement \| Series A Convertible Preferred Stock \| Two Thousand And Sixteen Private Investment In Public Equity
Class of Stock [Line Items]
Preferred stock, shares issued (shares)						4,963
At the market offering
Class of Stock [Line Items]
Shares of common stock issued (shares)								3,571,428
Issue price per share (USD per share) \| $ / shares								$ 2.80
Net proceeds from underwritten public offering \| $								$ 10,000
Gross sales proceeds from common stock \| $								$ 9,700
Sales commissions and fees								3.00%
Securities Purchase Agreement
Class of Stock [Line Items]
Number of capital units sold in private placement transaction (units)						8,188,804
Price per unit issued (USD per share) \| $ / shares						$ 2.015
Gross proceeds from private placement units sold \| $						$ 16,500
Net proceeds from private placement units sold \| $						$ 15,300
Two Thousand And Sixteen Private Investment In Public Equity
Class of Stock [Line Items]
Shares of common stock issued (shares)						3,225,804

Net Loss per Share - Narrative (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Anti-dilutive stock excluded from calculation of weighted average shares outstanding (shares)	37.0	33.4

Stock and Employee Benefit Plans - Narrative (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Jun. 23, 2020 shares	Dec. 31, 2020 USD ($) purchasePeriod $ / shares shares	Dec. 31, 2019 $ / shares shares
Defined Benefit Plan Disclosure [Line Items]
Issuance of common stock resulting from purchase of employee stock purchase plan shares (shares)		69,544	113,112
Unrecognized compensation costs related to nonvested awards \| $		$ 7.1
Weighted-average compensation cost recognition period		2 years 1 month 20 days
2020 Plan
Defined Benefit Plan Disclosure [Line Items]
Common stock authorized for issuance (shares)	3,500,000
Maximum term of stock options		10 years
Number of options granted (shares)		2,311,481	2,489,269
Weighted-average fair value (USD per share) \| $ / shares		$ 1.92	$ 2.31
2019 Plan
Defined Benefit Plan Disclosure [Line Items]
Shares available for grant under prior plan (shares)	1,579,678
Stock available for future grant (shares)		3,475,104
Executive Officers and Senior Leadership
Defined Benefit Plan Disclosure [Line Items]
Number of options granted (shares)		0
Unrecognized compensation costs related to nonvested awards \| $		$ 0.6
Employee Stock
Defined Benefit Plan Disclosure [Line Items]
Common stock authorized for issuance (shares)		500,000
Discount from market price (as a percent)		85.00%
Number of purchase periods \| purchasePeriod		2
Term of purchase period		6 months

Stock and Employee Benefit Plans - Fair Value Assumptions (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, minimum (as a percent)	0.10%
Risk free interest rate, maximum (as a percent)	0.18%
Expected volatility, minimum (as a percent)	74.36%
Expected volatility, maximum (as a percent)	120.89%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, minimum (as a percent)	0.33%	1.41%
Risk free interest rate, maximum (as a percent)	1.53%	2.60%
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility, minimum (as a percent)	70.00%	81.70%
Expected volatility, maximum (as a percent)	75.80%	81.80%
Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years	5 years
Stock Options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 8 months 23 days	5 years 8 months 23 days
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate (as a percent)		2.48%
Expected term (in years)	6 months	6 months
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility (as a percent)		57.57%

Stock and Employee Benefit Plans - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Executive Officers and Senior Leadership
Number of Options
Outstanding (shares)	1,200,000
Granted (shares)	0
Canceled (shares)	779,687
Outstanding (shares)	420,313	1,200,000
Vested or expected to vest (shares)	420,313
Exercisable (shares)	214,063
Weighted- Average Exercise Price
Outstanding (USD per share)	$ 4.36
Granted (USD per share)	0
Canceled (USD per share)	4.01
Outstanding (USD per share)	5.00	$ 4.36
Vested or expected to vest (USD per share)	5.00
Exercisable (USD per share)	$ 5.34
Weighted- Average Remaining Contractual Life
Outstanding	8 years 1 month 13 days
Vested or expected to vest	8 years 1 month 13 days
Exercisable	7 years 7 months 6 days
Aggregate Intrinsic Value (in thousands)
Outstanding	$ 130
Granted	0
Canceled	0
Outstanding	0	$ 130
Vested or expected to vest	0
Exercisable	$ 0
2020 Plan
Number of Options
Outstanding (shares)	8,259,915
Granted (shares)	2,311,481	2,489,269
Exercised (shares)	149,406
Canceled (shares)	830,867
Outstanding (shares)	9,591,123	8,259,915
Vested or expected to vest (shares)	9,591,123
Exercisable (shares)	6,123,532
Weighted- Average Exercise Price
Outstanding (USD per share)	$ 3.60
Granted (USD per share)	3.15
Exercised (USD per share)	1.95
Canceled (USD per share)	4.58
Outstanding (USD per share)	3.44	$ 3.60
Vested or expected to vest (USD per share)	3.44
Exercisable (USD per share)	$ 3.28
Weighted- Average Remaining Contractual Life
Outstanding	6 years 10 months 2 days
Vested or expected to vest	6 years 10 months 2 days
Exercisable	5 years 9 months 21 days
Aggregate Intrinsic Value (in thousands)
Outstanding	$ 7,987
Granted	0
Exercised	97
Canceled	101
Outstanding	2,303	$ 7,987
Vested or expected to vest	2,303
Exercisable	$ 2,269

Stock and Employee Benefit Plans - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 5,090	$ 5,374
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	2,394	2,446
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,696	$ 2,928

Leases - Narrative (Details) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
Leases - Narrative (Details) $ in Millions	May 31, 2020 ft²	Feb. 29, 2020 USD ($) ft²	Aug. 31, 2015 ft²	Mar. 31, 2020 ft² leaseAgreement floor	Dec. 31, 2020 USD ($) ft² extensionOption	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Lease liabilities \| $					$ 2.2	$ 0.5
Boston, Massachusetts
Loss Contingencies [Line Items]
Area of leased property (square feet)			3,950
Freising, Germany
Loss Contingencies [Line Items]
Area of leased property (square feet)				19,000
Number of lease agreements (lease agreements) \| leaseAgreement				4
Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property (square feet)		105,000
Lease term		12 years 6 months
Number of agreement extension options (extension options) \| extensionOption					2
Lease renewal term					60 months
Rent expense \| $		$ 0.2
Security deposit \| $								$ 0.8
Tenant Improvements \| $							$ 11.5
Leases in same building \| Freising, Germany
Loss Contingencies [Line Items]
Number of lease agreements (lease agreements) \| leaseAgreement				3
Number of floors (in floors) \| floor				3
Leases expected to be delivered by February 2020 \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property (square feet)		96,400
Leases expected to be delivered by May 2020 \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property (square feet)	8,600
Leases expected to be delivered by October 2024 \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property (square feet)					22,300
Leases with first right of refusal for additional area \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property (square feet)					13,400

Leases - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
Leases - Lease Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease costs	$ 1,509	$ 1,524
Variable lease costs	708	293
Total lease cost	$ 2,217	$ 1,817

Leases - Summary of the Lease Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Weighted-average remaining lease term (years)	11 years 4 months 24 days	12 years 1 month 6 days
Weighted-average discount rate	10.50%	10.50%

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2021	$ 2,662
2022	2,458
2023	2,424
2024	2,424
2025	2,424
Thereafter	14,556
Total undiscounted lease payments	26,948
Less: present value adjustment	(9,986)
Present value of lease liabilities	$ 16,962
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndOtherAccuredLiabilitiesCurrent	us-gaap:AccountsPayableAndOtherAccuredLiabilitiesCurrent

Label	Element	Value
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2014-09 [Member]

- Definition

Indicates amendment to accounting standards.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(i)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(3)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iv)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iii)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 24: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(4)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(ii)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (d)(2)

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (d)(3)

+ Details