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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Mar. 09, 2020	Jun. 28, 2019
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	PIRS
Security Exchange Name	NASDAQ
Entity Registrant Name	PIERIS PHARMACEUTICALS, INC.
Entity Central Index Key	0001583648
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Public Float			$ 206,297,429
Entity Common Stock, Shares Outstanding		55,212,437

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 62,260	$ 74,867
Short term investments	41,894	53,240
Accounts receivable	6,787	2,701
Prepaid expenses and other current assets	4,072	4,574
Total current assets	115,013	135,382
Property and equipment, net	19,502	5,049
Operating lease right-of-use assets	3,436	0
Other non-current assets	3,146	910
Total assets	141,097	141,341
Current liabilities:
Accounts payable	5,803	3,350
Accrued expenses and other current liabilities	9,944	9,114
Deferred revenues, current portion	11,256	35,612
Total current liabilities	27,003	48,076
Deferred revenue, net of current portion	47,258	53,303
Operating lease liabilities	15,484	0
Other long-term liabilities	0	27
Total liabilities	89,745	101,406
Stockholders’ equity:
Common stock, $0.001 par value per share, 300,000,000 shares authorized and 55,212,437 and 54,151,219 issued and outstanding at December 31, 2019 and 2018, respectively	55	54
Additional paid-in capital	227,468	189,929
Accumulated other comprehensive loss	(1,995)	(2,982)
Accumulated deficit	(174,176)	(147,066)
Total stockholders’ equity	51,352	39,935
Total liabilities and stockholders’ equity	141,097	141,341
Series A Convertible Preferred Stock
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized at December 31, 2019 and 2018, respectively	0	0
Series B Convertible Preferred Stock
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized at December 31, 2019 and 2018, respectively	0	0
Series C Convertible Preferred Stock
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized at December 31, 2019 and 2018, respectively	$ 0	$ 0

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Preferred stock
Preferred stock, par value (USD per share)	$ 0.001	$ 0.001
Preferred stock authorized (shares)	10,000,000	10,000,000
Series A - Preferred stock outstanding (shares)	2,907	4,963
Common stock
Common stock, par value (USD per share)	$ 0.001	$ 0.001
Common stock authorized (shares)	300,000,000	300,000,000
Common stock issued (shares)	55,212,437	54,151,219
Common stock outstanding (shares)	55,212,437	54,151,219
Series A Convertible Preferred Stock
Preferred stock
Series A - Preferred stock issued (shares)	2,907	2,907
Series A - Preferred stock outstanding (shares)	2,907	2,907
Series B Convertible Preferred Stock
Preferred stock
Series A - Preferred stock issued (shares)	5,000	0
Series A - Preferred stock outstanding (shares)	5,000	0
Series C Convertible Preferred Stock
Preferred stock
Series A - Preferred stock issued (shares)	3,522	0
Series A - Preferred stock outstanding (shares)	3,522	0

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue	$ 46,279	$ 29,101
Operating expenses
Research and development	54,996	41,490
General and administrative	18,440	18,442
Total operating expenses	73,436	59,932
Loss from operations	(27,157)	(30,831)
Interest income	1,714	1,962
Other (expense) income, net	(26)	1,803
Loss before income taxes	(25,469)	(27,066)
Benefit for income tax	0	(312)
Net loss	(25,469)	(26,754)
Other comprehensive income/(loss) components:
Foreign currency translation	973	1,196
Unrealized gain on available-for-sale securities, net of taxes of $0 and $164, respectively	14	517
Comprehensive loss	(24,482)	(25,041)
Reconciliation of Net Loss to net Loss Attributable to Common Stockholders [Abstract]
Net loss attributable to common stockholders	$ (28,299)	$ (26,754)
Net loss per share:
Basic and diluted (USD per share)	$ (0.56)	$ (0.50)
Weighted average number of common shares outstanding used in net loss per share attributable to common stockholders
Basic and diluted (shares)	50,625	53,081
Series C Convertible Preferred Stock
Reconciliation of Net Loss to net Loss Attributable to Common Stockholders [Abstract]
Accretion of Series C convertible preferred stock	$ (2,830)	$ 0

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Tax provision on other comprehensive income	$ 0	$ 164

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Shares	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Series A Convertible Preferred Stock Preferred Shares	Series B Convertible Preferred Stock Preferred Shares	Series C Convertible Preferred Stock Preferred Shares
Balance at beginning of period (shares) at Dec. 31, 2017		45,017,000				5,000
Balance at beginning of period at Dec. 31, 2017	$ 11,522	$ 45	$ 136,484	$ (4,695)	$ (120,312)	$ 0
Increase (Decrease) in Stockholders' Equity
Net loss	(26,754)				(26,754)
Foreign currency translation adjustment	1,196			1,196
Unrealized gain on investments	517			517
Stock based compensation expense	$ 4,943		4,943
Issuance of common stock resulting from exercise of stock options (shares)	596,269	596,000
Issuance of common stock resulting from exercise of stock options	$ 986	$ 1	985
Issuance of common stock resulting from exercise of warrants (shares)		157,000
Issuance of common stock resulting from exercise of warrants	314		314
Issuance of common stock net $3,374 in offering costs (shares)		6,325,000
Issuance of common stock net $3,374 in offering costs	47,211	$ 6	47,205
Preferred stock conversion (shares)		2,056,000				(2,000)
Preferred stock conversion	0	$ 2	(2)
Balance at end of period (shares) at Dec. 31, 2018		54,151,000				3,000
Balance at end of period at Dec. 31, 2018	39,935	$ 54	189,929	(2,982)	(147,066)	$ 0
Increase (Decrease) in Stockholders' Equity
Net loss	(25,469)				(25,469)
Foreign currency translation adjustment	973			973
Unrealized gain on investments	14			14
Stock based compensation expense	$ 5,374		5,374
Issuance of common stock resulting from exercise of stock options (shares)	279,075	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 net $3,374 in offering costs (shares)		5,493,000						4,000
Issuance of common stock net $3,374 in offering costs	30,998	$ 6	30,992
Preferred stock conversion (shares)		(5,000,000)					5,000
Preferred stock conversion	0	$ (5)	5
Balance at end of period (shares) at Dec. 31, 2019		55,212,000				3,000	5,000	4,000
Balance at end of period at Dec. 31, 2019	51,352	$ 55	$ 227,468	$ (1,995)	(174,176)	$ 0
Increase (Decrease) in Stockholders' Equity
Adoption of ASC 606, Revenue from Contracts with Customers	$ (1,641)				$ (1,641)

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Offering costs	$ 1,005	$ 3,374
Tax provision on other comprehensive income	$ 0	$ 164

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net loss	$ (25,469,000)	$ (26,754,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	632,000	570,000
Right-of-use asset amortization	408,000	0
Stock-based compensation	5,374,000	4,943,000
Other non-cash transactions	(69,000)	75,000
Realized investment gains	(1,161,000)	(1,651,000)
Deferred tax benefit	0	(164,000)
Foreign currency re-measurement loss	(61,000)	22,000
Changes in operating assets and liabilities:
Accounts receivable	(4,055,000)	12,511,000
Prepaid expenses and other assets	(679,000)	(3,939,000)
Deferred revenue	(28,524,000)	9,308,000
Accounts payable	1,257,000	764,000
Accrued expenses and other current liabilities	(914,000)	3,249,000
Lease liabilities	794,000	0
Net cash (used in) operating activities	(52,467,000)	(1,066,000)
Investing activities:
Purchase of property and equipment	(2,462,000)	(1,698,000)
Proceeds from maturities of investments	63,325,000	88,358,000
Proceeds from sale of investments	8,292,000	22,047,000
Purchase of investments	(59,317,000)	(117,582,000)
Net cash provided by/(used in) investing activities	9,838,000	(8,875,000)
Financing activities:
Proceeds from exercise of options	553,000	986,000
Proceeds from employee stock purchase plan	369,000	0
Proceeds from exercise of warrants	246,000	314,000
Issuance of Common and Preferred Stock, net of issuance costs	30,998,000	47,211,000
Net cash provided by financing activities	32,166,000	48,511,000
Effect of exchange rate change on cash and cash equivalents	(2,144,000)	(1,581,000)
Net increase in cash and cash equivalents	(12,607,000)	36,989,000
Cash and cash equivalents at beginning of year	74,867,000	37,878,000
Cash and cash equivalents at end of year	62,260,000	74,867,000
Supplemental cash flow disclosures:
Accretion of Series C convertible preferred stock	2,830	0
Cash paid for income taxes	0	908,000
Net unrealized gain on investments	14,000	681,000
Property and equipment included in accounts payable	$ 1,235,000	$ 241,000

Corporate Information	12 Months Ended
Corporate Information	Dec. 31, 2019
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, 2019, 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 uncontrolled asthma and an immuno-oncology, or IO, bispecific targeting HER2 and 4-1BB. 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. As of December 31, 2019, the Company had cash, cash equivalents and investments of $104.2 million. The Company expects that its existing cash, cash equivalents, and investments, are sufficient to support operating expense and capital expenditure requirements for at least 12 months from the date of this filing.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

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, revenue recognition; deferred tax assets, deferred tax liabilities and valuation allowances; determination of the incremental borrowing rate to calculate right-of-use assets and lease liabilities; 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. As of December 31, 2019, there were no investments with a fair value that was significantly lower than the amortized cost basis or any investments that had been in an unrealized loss position for a significant period.

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 4).

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, 2019 and 2018. 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. 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 equipment		10 - 14
Office and computer equipment		3 - 13

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.

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.

Impact of Adopting ASC 606 on the Financial Statements

As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2019:



	As Reported, December 31, 2018			ASC 606 Adjustment			Adjusted, January 1, 2019
Consolidated Balance Sheet Data (in thousands):
Prepaid expenses and other current assets	$	4,574		$	716		$	5,290
Other non-current assets	910			1,120			2,030
Total Assets	$	141,341		$	1,836		$	143,177
Deferred revenue, net of current portion	53,303			3,477			56,780
Total Liabilities	101,406			3,477			104,883
Accumulated deficit	(147,066		)	(1,641		)	(148,707		)
Total stockholders' equity	39,935			(1,641		)	38,294
Total liabilities and stockholders' equity	$	141,341		$	1,836		$	143,177

These changes were primarily caused by the differences in determining and allocating transaction price under ASC 606 and costs to obtain certain contracts under ASC 340.

The adoption of ASC 606 did not impact income taxes, as the Company fully reserves its net deferred tax assets. Therefore, the change to the Company's net deferred tax asset position due to adoption was offset by a corresponding change to the valuation allowance.

The following table compares the reported consolidated balance sheet and statement of operations, as of December 31, 2019 and for the twelve months ended December 31, 2019, to the pro-forma amounts had the previous guidance been in effect:



	December 31, 2019
	As Reported, ASC 606			Adjustments			Adjusted Balance, ASC 605
Consolidated Balance Sheet Data (in thousands):
Prepaids and other current assets	$	4,072		$	(124	)	$	3,948
Other non-current assets	3,146			(815		)	2,331
Total Assets	$	141,097		$	(939	)	$	140,158
Deferred revenues, current portion	11,256			3,382			14,638
Deferred revenue, net of current portion	47,258			(9,069		)	38,189
Total Liabilities	89,745			(5,687		)	84,058
Accumulated Deficit	(174,176		)	4,748			(169,428		)
Total stockholders' equity	51,352			4,748			56,100
Total liabilities and stockholders' equity	$	141,097		$	(939	)	$	140,158



	December 31, 2019
	As Reported, ASC 606			Adjustments			Adjusted Balance, ASC 605
Consolidated Statement of Operations Data (in thousands):
Revenue	$	46,279		$	2,315		$	48,594
General and administrative expenses	18,440			(858		)	17,582
Loss from operations	(27,157		)	1,457			(25,700		)
Loss before income taxes	(25,469		)	1,457			(24,012		)
Net loss	$	(25,469	)	$	1,457		$	(24,012	)
Comprehensive loss	$	(24,482	)	$	1,457		$	(23,025	)

These changes were primarily caused by the revenue recognition and related cost amortization patterns due to differences in the determination and allocation of transaction price under ASC 606 and costs to obtain certain contracts under ASC 340. The application of ASC 606 did not have an impact on the Company’s net cash used in operating activities for the twelve months ended December 31, 2019 but did result in offsetting adjustments to net loss, change in other current and non-current assets, and the change in deferred revenue presented within the consolidated statements of cash flows for that period.

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, 2019 and 2018, 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. As a result, prior periods are presented in accordance with the previous guidance in ASC 840, Leases, or ASC 840.

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.

The adoption of the new standard resulted in recording a transition adjustment on January 1, 2019 of right-of-use assets of $0.9 million and lease liabilities of $0.9 million for operating leases and the derecognition of deferred rent originally accounted for under legacy guidance. The adoption did not have a material impact on the consolidated statement of operations. See Note 12 for additional details.

Impact of Adopting ASC 842 on the Financial Statements



	As Reported, December 31, 2018	ASC 842 Adjustment		Adjusted, January 1, 2019
Consolidated Balance Sheet Data (in thousands):
Operating lease right-of-use assets (1)	—	868		868
Deferred rent (2)	35	(35	)	—
Current operating lease liabilities (3)	—	442		442
Non-current operating lease liabilities (3)	—	461		461

(1) Represents capitalization of operating lease right-of-use assets.
(2) Represents reclassification of deferred rent to operating lease right-of-use assets.
(3) Represents recognition of operating lease liabilities.

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 November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808):Clarifying the Interaction between Topic 808 and Topic 606, or ASU 2018-18. ASU 2018-18 makes targeted improvements to generally accepted accounting principles for collaborative arrangements, including: clarification that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account; adding unit-of-account guidance in Topic 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. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. The Company is currently evaluating the impact of adoption, but this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

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, or ASU 2018-19, 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, or ASU 2019-11 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, or ASU 2019-10, 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 adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

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, 2019

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, 2019 and 2018, respectively, the Company recognized revenues as follows (in thousands):



	Years Ended December 31,
	2019		2018
Revenue from contract with customers	$	43,646	$	27,248
Collaboration revenue	2,633		1,762
Other revenues	—		91
Total Revenue	$	46,279	$	29,101

During the years ended December 31, 2019 and 2018, respectively, the Company recognized revenue from the following strategic partnerships and other license agreements (in thousands):



	Years Ended December 31,
	2019		2018
AstraZeneca	$	25,828	$	17,632
Seattle Genetics	2,493		5,413
Servier	15,048		4,508
Other	2,910		1,548
Total Revenue	$	46,279	$	29,101

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



	Research, Development, Regulatory & Commercial Milestones		Sales Milestones
AstraZeneca	$	1,111	$	960
Servier	799		707
Seattle Genetics	769		450
Total potential milestone payments	$	2,679	$	2,117

Strategic Partnerships

Seattle Genetics

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

Under the terms of the Seattle Genetics Agreements, the companies will pursue multiple antibody-Anticalin fusion proteins during the research phase. The Seattle Genetics Agreements provide Seattle Genetics 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. Seattle Genetics will solely develop, fund and commercialize the other two programs. Seattle Genetics 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 Seattle Genetics Platform License grants Seattle Genetics a non-exclusive license to certain intellectual property related to the Anticalin platform technology.

Upon signing the Seattle Genetics Agreements, Seattle Genetics 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 Seattle Genetics 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 Seattle Genetics Agreements ends upon the expiration of all of Seattle Genetics’ payment obligations under each agreement. The Seattle Genetics Collaboration Agreement may be terminated by Seattle Genetics 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 Seattle Genetics' option. If any program is terminated by Seattle Genetics after a pre-defined pre-clinical stage, the Company will have full rights to continue such program. If any program is terminated by Seattle Genetics 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 Seattle Genetics for such program. The Seattle Genetics Collaboration Agreement may also be terminated by Seattle Genetics 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 Seattle Genetics 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 Seattle Genetics Agreements if the other party challenges the validity of any patents licensed under the Seattle Genetics Agreements, subject to certain exceptions. The Seattle Genetics Platform License will terminate upon termination of the Seattle Genetics Collaboration Agreement, whether in its entirety or on a product-by-product basis.

The Company determined that the Seattle Genetics Agreements should be combined and evaluated as a single arrangement under ASC 606 as they were executed on the same date. The arrangement with Seattle Genetics 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 Seattle Genetics 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 Seattle Genetics 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 Seattle Genetics 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 Seattle Genetics 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, 2019, there was $24.7 million of aggregate transaction price allocated to remaining performance obligations.

Under the Seattle Genetics 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, 2019, there is $4.5 million and $16.0 million of current and non-current deferred revenue, respectively, related to the Seattle Genetics Agreements.

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, 2019, there was $26.0 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, 2019, there is $1.0 million and $17.5 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, 2019, 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, 2019, was $0.4 million.

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 another 12 months.

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, 2019, there was $19.4 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 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. Servier’s termination of the co-development of the PRS-332 program does not impact the remainder of the Pieris-Servier alliance and the parties continue to advance PRS-344 through IND-enabling activities. The Pieris-Servier alliance includes three additional programs beyond PRS-344, all of which are in active preclinical development.

In addition, effective in January 2020, Servier and the Company agreed to extend the research collaboration term for one year. This extension includes reimbursement for the Company's internal efforts and an extension of the research license.

As of December 31, 2019, there is $5.7 million and $13.7 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, 2019, the remaining balance of the asset recognized from costs to obtain the Servier contract is $0.3 million. Amortization during the twelve months ended December 31, 2019 was $0.2 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 2018.

On January 20, 2020 ASKA notified us 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. Amortization during the twelve months ended December 31, 2019 was $0.3 million and thus, as of December 31, 2019, there was no remaining balance of the asset recognized from costs to obtain the ASKA contract.

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 no additions to deferred revenue during the twelve months ended December 31, 2019 and reductions to deferred revenue were $32.2 million for the twelve months ended December 31, 2019.

Cash, Cash Equivalents and Investments

12 Months Ended

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Investments

As of December 31, 2019 and 2018, 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, 2019 and 2018 (in thousands):



	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	$	—



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2018
Money market funds, included in cash equivalents	$	7,791	$	7,791	$	—	$	—
Corporate bonds, included in cash equivalents	10,910		—		10,910		—
Investments - US treasuries	7,518		7,518		—		—
Investments - Asset-backed securities	5,758		—		5,758		—
Investments - Corporate bonds	39,964		—		39,964		—
Total	$	71,941	$	15,309	$	56,632	$	—

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

Investments at December 31, 2018 consist of the following (in thousands):



	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses			Fair Value
Investments
US treasuries	150-164	$	7,541	$	—	$	(23	)	$	7,518
Asset-backed securities	196-259	5,766		1		(9		)	5,758
Corporate bonds	73-252	40,072		3		(111		)	39,964
Total		$	53,379	$	4	$	(143	)	$	53,240

There were $0.3 million and $1.0 million of realized gains for the year ended December 31, 2019 and 2018, respectively.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

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



	Years Ended December 31,
	2019			2018
Laboratory equipment	$	11,635		$	7,431
Office and computer equipment	724			661
Leasehold improvements	10,710			323
Property and equipment at cost	23,069			8,415
Accumulated depreciation	(3,567		)	(3,366		)
Property and equipment, net	$	19,502		$	5,049

Depreciation expense was $0.6 million and $0.6 million for the years ended December 31, 2019 and 2018, respectively. There were no other changes in accumulated depreciation other than the foreign currency impact.

Accrued Expenses

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Accrued Expenses

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



	Years Ended December 31,
	2019		2018
Accrued accounts payable	$	4,251	$	943
Compensation expense	2,870		2,380
Research and development fees	1,048		1,945
Lease liabilities	733		—
Audit and tax fees	522		378
Other current liabilities	458		945
Accrued license obligations	62		2,523
Total	$	9,944	$	9,114

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

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



	Years Ended December 31,
	2019			2018
Domestic	$	(12,063	)	$	(10,633	)
Foreign	(13,406		)	(16,433		)
Loss before income taxes	$	(25,469	)	$	(27,066	)

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



	Years Ended December 31,
	2019		2018
Current:
Federal	$	—	$	—
State	—		—
Foreign	—		(148		)
Total current	—		(148		)
Deferred:
Federal	—		—
State	—		—
Foreign	—		(164		)
Total deferred	—		(164		)
(Benefit) provision for income taxes	$	—	$	(312	)

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



	2019		2018
Federal income tax rate	21.0	%	21.0	%
Tax Reform - Change in enacted rate	—		—
Foreign rate differential	1.9		7.4
State tax, net of federal benefit	2.6		0.7
US tax on foreign income	(1.2	)	(8.1	)
Share-based awards compensation	(2.5	)	2.0
Permanent items	(1.0	)	0.8
Other	0.8		0.5
Rate change - trade tax NOL	(6.4	)	—
Change in valuation allowance	(15.2	)	(23.1	)
Effective income tax rate	—	%	1.2	%

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,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	30,455		$	27,879
Share-based awards compensation	2,705			2,359
Accrued expenses	328			304
Depreciation and other	53			125
Deferred revenue	—			641
Unrealized foreign currency	90			—
Lease liability	4,378			—
Total deferred tax assets	38,009			31,308
Deferred tax liabilities:
Right-of-use asset	(4,043		)	—
Unrealized gain on investments	—			(394		)
Other	—			(98		)
Total deferred tax liabilities	(4,043		)	(492		)
Less: valuation allowance:	(33,966		)	(30,816		)
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, 2019, 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 $3.2 million was primarily influenced by the operating losses generated in current tax year.

As of December 31, 2019, the Company had net operating loss carryforwards for U.S. federal income tax purposes of $20.1 million and net operating loss carryforwards for state income tax purposes of $26.7 million. Federal tax loss carryforwards that were created prior to December 31, 2017 expire through 2037, U.S. federal 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 not under examination by the Internal Revenue Service or any other jurisdictions for any tax years.

As of December 31, 2019, the Company had German corporate income tax and trade tax net operating loss carryforwards of approximately $90.5 million and $89.7 million respectively. Under current German laws, tax loss carryforwards may only be used to offset any relevant later assessment period (calendar year) $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, 2019 and December 31, 2018.

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, 2019 and 2018 (in thousands):



Unrecognized tax benefits at December 31, 2018	$	6,157
Currency translation adjustment	(125		)
Unrecognized tax benefits at December 31, 2019	$	6,032

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.

Stockholders' Equity

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Stockholders' Equity

Stockholders’ equity

Common Stock

During the year ended December 31, 2019, the Company issued 279,075 shares of common stock upon exercise of stock options, resulting in cash proceeds of $0.6 million. During the year ended December 31, 2018, the Company issued 596,269 shares of common stock upon exercise of stock options, resulting in cash proceeds of $1.0 million.

During the year ended December 31, 2019, the Company issued 176,071 net shares of common stock due to warrant exercises. Net exercises of 127,065 shares of common stock underlying the warrants resulted in the issuance of 52,833 shares of common stock. Additionally, 123,238 warrants were exercised resulting in cash proceeds of $0.2 million. During the year ended December 31, 2018, the Company issued 156,888 shares of common stock due to warrant exercises, resulting in cash proceeds of $0.3 million. The Company had no such net issuances of common stock due to warrant exercises during the year ended December 31, 2018.

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 five 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, or the Junior Securities;


•	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, or the Parity Securities; 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, or the Senior Securities;

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.

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 under a shelf registration statement on Form S-3. To date, the Company has not sold any shares under this agreement.

Net Loss per Share	12 Months Ended
Net Loss per Share	Dec. 31, 2019
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, 2019 and 2018, and as calculated using the treasury stock method, approximately 33.4 million and 14.7 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, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock and Employee Benefit Plans

Employee, Director and Consultant Equity Incentive Plans

At the Annual Shareholder Meeting, held on July 31, 2019, the shareholders approved the 2019 Employee, Director and Consultant Equity Incentive Plan, or the 2019 Plan. Upon approval of the 2019 Plan, the 2018 Employee, Director and Consultant Equity Incentive Plan, or the 2018 Plan, was terminated and no additional awards will be made thereunder, however, all outstanding awards under the 2018 Plan will remain in effect. The 2019 Plan, similar to the 2018 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. Previously, upon approval of the 2018 Plan, the 2016 Employee, Director and Consultant Equity Incentive Plan, or the 2016 Plan, was terminated and no additional awards were made thereunder, however, all outstanding awards under the 2016 Plan remained and will continue to remain in effect. The 2016 Plan, similar to the 2014 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. Previously, upon approval of the 2016 Plan, the 2014 Employee, Director and Consultant Equity Incentive Plan, or the 2014 Plan, was terminated and no additional awards were made thereunder, however, all outstanding awards under the 2014 Plan remained and continue to remain in effect.

There were approximately 654,341 shares remaining and available for grant under the 2018 Plan that terminated pursuant to the approval of the 2019 Plan. The 2019 Plan permits the Company to issue up to 5,750,000 shares, including 2,750,000 shares reserved for issuance pursuant to the 2019 Plan and up to 3,000,000 additional shares which may be issued if awards outstanding under the Registrant’s 2018 Plan 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,
	2019	2018
Risk free interest rate	1.41% - 2.60%	2.40% - 3.06%
Expected term (in years)	5.00 - 5.73	4.75 - 5.73
Dividend yield	—	—
Expected volatility	81.7% - 81.8%	77.1% - 80.5%

The weighted-average fair value of the 2,489,269 and 1,881,660 options granted during the years ended December 31, 2019 and 2018 was $2.31 and $5.04, respectively. As of December 31, 2019, there were 2,912,721 shares available for future grant under the 2019 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, 2018	6,850,047		$	3.76		$	3,257
Granted	2,189,269		3.16			—
Exercised	(279,075	)	1.98			486
Canceled	(500,326	)	4.70			288
Outstanding, December 31, 2019	8,259,915		$	3.60	7.25 years	$	7,987
Vested or expected to vest, December 31, 2019	8,259,915		$	3.60	7.25 years	$	7,987
Exercisable, December 31, 2019	4,908,300		$	3.11	6.32 years	$	6,348

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 2019 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, 2018	1,125,000		$	4.41		$	—
Granted	300,000		$	4.65		$	—
Canceled	(225,000	)	$	5.00		$	—
Outstanding, December 31, 2019	1,200,000		$	4.36	5.93 years	$	130
Vested or expected to vest	1,200,000		$	4.36	5.93 years	$	130
Exercisable, December 31, 2019	812,500		$	4.08	4.35 years	$	130

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 for the year ended December 31, 2019 were 113,112. No purchases were made under the plan for the year ended December 31, 2018. 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,
	2019		2018
Risk free interest rate	1.61	%	2.48	%
Expected term (in years)	0.5 years		0.5 years
Dividend yield	—		—
Expected volatility	78.10	%	57.57	%

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,
	2019		2018
Research and development	$	2,446	$	1,984
General and administrative	2,928		2,959
Total stock-based compensation	$	5,374	$	4,943

As of December 31, 2019, the total unrecognized compensation cost related to all non-vested awards was $9.3 million of which $1.2 million are for inducement options. The Company expects to recognize the compensation cost over a remaining weighted-average period of 2.46 years.

License Agreement	12 Months Ended
License Agreement	Dec. 31, 2019
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. The Company recorded the probable expected impact of the amendment in research and development expense as of December 31, 2018, which was an increase in its financial obligations associated with the TUM License of approximately $2.3 million, for amounts that would be due in 2019 for 2018 and 2017 sub-licensing activities. This liability was paid in full during the year ended December 31, 2019.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

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.

The Company also leases 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 terminate on March 31, 2020.

In October 2018, Pieris GmbH entered into a new 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 will rent 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 is expected to be 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 as of December 31, 2018. 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 following table summarizes operating lease costs included in operating expenses for the twelve months ended December 31, 2019 (in thousands):



	Twelve Months Ended December 31, 2019

Operating lease costs	$	1,524
Variable lease costs (1)	293
Total lease cost	$	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.

During the year ended December 31, 2018, the Company recognized rent expense in an amount of $0.5 million under the previous guidance in ASC 840.

The following table summarizes the weighted-average remaining lease term and discount rate as of December 31, 2019:



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

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

As of December 31, 2019, the maturities of the Company’s operating lease liabilities and future minimum lease payments were as follows (in thousands):



	Total
2020	$	2,317
2021	2,418
2022	2,249
2023	2,214
2024	2,214
Thereafter	16,790
Total undiscounted lease payments	28,202
Less: present value adjustment	(11,985		)
Present value of lease liabilities	16,217

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Consolidation

Basis of Presentation and Use of Estimates

Use of Estimates

Foreign Currency Translation

Cash, Cash Equivalents and Investments

Concentration of Credit Risk and Off-Balance Sheet Risk

Fair Value Measurement


•	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.

Financial instruments measured at fair value on a recurring basis include cash equivalents and investments (Note 4).

Fair Values of Financial Instruments

Accounts Receivable

Property and Equipment



Asset Classification		Estimated useful life (in years)
Leasehold improvements		shorter of useful life or remaining life of the lease
Laboratory equipment		10 - 14
Office and computer equipment		3 - 13

Impairment of Long-lived Assets

Revenue Recognition

Collaborative Arrangements

Revenue from Contracts with Customers

Milestones and Royalties

Contract Balances

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

Research and Development

Income Taxes

Stock-based Compensation

Recent Accounting Pronouncements

Recent Accounting Pronouncements Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Estimated Useful Life 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 equipment		10 - 14
Office and computer equipment		3 - 13

Schedule of Impact of Adopting ASC 606 & 842 on the Financial Statements

Impact of Adopting ASC 842 on the Financial Statements



	As Reported, December 31, 2018	ASC 842 Adjustment		Adjusted, January 1, 2019
Consolidated Balance Sheet Data (in thousands):
Operating lease right-of-use assets (1)	—	868		868
Deferred rent (2)	35	(35	)	—
Current operating lease liabilities (3)	—	442		442
Non-current operating lease liabilities (3)	—	461		461

(1) Represents capitalization of operating lease right-of-use assets.
(2) Represents reclassification of deferred rent to operating lease right-of-use assets.
(3) Represents recognition of operating lease liabilities.

As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2019:



	As Reported, December 31, 2018			ASC 606 Adjustment			Adjusted, January 1, 2019
Consolidated Balance Sheet Data (in thousands):
Prepaid expenses and other current assets	$	4,574		$	716		$	5,290
Other non-current assets	910			1,120			2,030
Total Assets	$	141,341		$	1,836		$	143,177
Deferred revenue, net of current portion	53,303			3,477			56,780
Total Liabilities	101,406			3,477			104,883
Accumulated deficit	(147,066		)	(1,641		)	(148,707		)
Total stockholders' equity	39,935			(1,641		)	38,294
Total liabilities and stockholders' equity	$	141,341		$	1,836		$	143,177

These changes were primarily caused by the differences in determining and allocating transaction price under ASC 606 and costs to obtain certain contracts under ASC 340.



	December 31, 2019
	As Reported, ASC 606			Adjustments			Adjusted Balance, ASC 605
Consolidated Balance Sheet Data (in thousands):
Prepaids and other current assets	$	4,072		$	(124	)	$	3,948
Other non-current assets	3,146			(815		)	2,331
Total Assets	$	141,097		$	(939	)	$	140,158
Deferred revenues, current portion	11,256			3,382			14,638
Deferred revenue, net of current portion	47,258			(9,069		)	38,189
Total Liabilities	89,745			(5,687		)	84,058
Accumulated Deficit	(174,176		)	4,748			(169,428		)
Total stockholders' equity	51,352			4,748			56,100
Total liabilities and stockholders' equity	$	141,097		$	(939	)	$	140,158



	December 31, 2019
	As Reported, ASC 606			Adjustments			Adjusted Balance, ASC 605
Consolidated Statement of Operations Data (in thousands):
Revenue	$	46,279		$	2,315		$	48,594
General and administrative expenses	18,440			(858		)	17,582
Loss from operations	(27,157		)	1,457			(25,700		)
Loss before income taxes	(25,469		)	1,457			(24,012		)
Net loss	$	(25,469	)	$	1,457		$	(24,012	)
Comprehensive loss	$	(24,482	)	$	1,457		$	(23,025	)

Revenue (Tables)

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Schedule of Revenues

During the years ended December 31, 2019 and 2018, respectively, the Company recognized revenues as follows (in thousands):



	Years Ended December 31,
	2019		2018
Revenue from contract with customers	$	43,646	$	27,248
Collaboration revenue	2,633		1,762
Other revenues	—		91
Total Revenue	$	46,279	$	29,101

During the years ended December 31, 2019 and 2018, respectively, the Company recognized revenue from the following strategic partnerships and other license agreements (in thousands):



	Years Ended December 31,
	2019		2018
AstraZeneca	$	25,828	$	17,632
Seattle Genetics	2,493		5,413
Servier	15,048		4,508
Other	2,910		1,548
Total Revenue	$	46,279	$	29,101

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):



	Research, Development, Regulatory & Commercial Milestones		Sales Milestones
AstraZeneca	$	1,111	$	960
Servier	799		707
Seattle Genetics	769		450
Total potential milestone payments	$	2,679	$	2,117

Cash, Cash Equivalents and Investments (Tables)

12 Months Ended

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Schedule of Cash Equivalents and Investments

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, 2019 and 2018 (in thousands):



	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	$	—



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2018
Money market funds, included in cash equivalents	$	7,791	$	7,791	$	—	$	—
Corporate bonds, included in cash equivalents	10,910		—		10,910		—
Investments - US treasuries	7,518		7,518		—		—
Investments - Asset-backed securities	5,758		—		5,758		—
Investments - Corporate bonds	39,964		—		39,964		—
Total	$	71,941	$	15,309	$	56,632	$	—

nvestments 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

Investments at December 31, 2018 consist of the following (in thousands):



	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses			Fair Value
Investments
US treasuries	150-164	$	7,541	$	—	$	(23	)	$	7,518
Asset-backed securities	196-259	5,766		1		(9		)	5,758
Corporate bonds	73-252	40,072		3		(111		)	39,964
Total		$	53,379	$	4	$	(143	)	$	53,240

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

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



	Years Ended December 31,
	2019			2018
Laboratory equipment	$	11,635		$	7,431
Office and computer equipment	724			661
Leasehold improvements	10,710			323
Property and equipment at cost	23,069			8,415
Accumulated depreciation	(3,567		)	(3,366		)
Property and equipment, net	$	19,502		$	5,049

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019		2018
Accrued accounts payable	$	4,251	$	943
Compensation expense	2,870		2,380
Research and development fees	1,048		1,945
Lease liabilities	733		—
Audit and tax fees	522		378
Other current liabilities	458		945
Accrued license obligations	62		2,523
Total	$	9,944	$	9,114

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019			2018
Domestic	$	(12,063	)	$	(10,633	)
Foreign	(13,406		)	(16,433		)
Loss before income taxes	$	(25,469	)	$	(27,066	)

Schedule of Components of Provision (Benefit) for Income Taxes

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



	Years Ended December 31,
	2019		2018
Current:
Federal	$	—	$	—
State	—		—
Foreign	—		(148		)
Total current	—		(148		)
Deferred:
Federal	—		—
State	—		—
Foreign	—		(164		)
Total deferred	—		(164		)
(Benefit) provision for income taxes	$	—	$	(312	)

Schedule of Reconciliation of Effective Tax Rate

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



	2019		2018
Federal income tax rate	21.0	%	21.0	%
Tax Reform - Change in enacted rate	—		—
Foreign rate differential	1.9		7.4
State tax, net of federal benefit	2.6		0.7
US tax on foreign income	(1.2	)	(8.1	)
Share-based awards compensation	(2.5	)	2.0
Permanent items	(1.0	)	0.8
Other	0.8		0.5
Rate change - trade tax NOL	(6.4	)	—
Change in valuation allowance	(15.2	)	(23.1	)
Effective income tax rate	—	%	1.2	%

Schedule of Components of Deferred Tax Assets and Liabilities



	Years Ended December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	30,455		$	27,879
Share-based awards compensation	2,705			2,359
Accrued expenses	328			304
Depreciation and other	53			125
Deferred revenue	—			641
Unrealized foreign currency	90			—
Lease liability	4,378			—
Total deferred tax assets	38,009			31,308
Deferred tax liabilities:
Right-of-use asset	(4,043		)	—
Unrealized gain on investments	—			(394		)
Other	—			(98		)
Total deferred tax liabilities	(4,043		)	(492		)
Less: valuation allowance:	(33,966		)	(30,816		)
Net deferred tax asset	$	—		$	—

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



Unrecognized tax benefits at December 31, 2018	$	6,157
Currency translation adjustment	(125		)
Unrecognized tax benefits at December 31, 2019	$	6,032

Stock and Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock Option Activity

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, 2018	1,125,000		$	4.41		$	—
Granted	300,000		$	4.65		$	—
Canceled	(225,000	)	$	5.00		$	—
Outstanding, December 31, 2019	1,200,000		$	4.36	5.93 years	$	130
Vested or expected to vest	1,200,000		$	4.36	5.93 years	$	130
Exercisable, December 31, 2019	812,500		$	4.08	4.35 years	$	130

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, 2018	6,850,047		$	3.76		$	3,257
Granted	2,189,269		3.16			—
Exercised	(279,075	)	1.98			486
Canceled	(500,326	)	4.70			288
Outstanding, December 31, 2019	8,259,915		$	3.60	7.25 years	$	7,987
Vested or expected to vest, December 31, 2019	8,259,915		$	3.60	7.25 years	$	7,987
Exercisable, December 31, 2019	4,908,300		$	3.11	6.32 years	$	6,348

Schedule of Fair Value Assumptions

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,
	2019		2018
Risk free interest rate	1.61	%	2.48	%
Expected term (in years)	0.5 years		0.5 years
Dividend yield	—		—
Expected volatility	78.10	%	57.57	%

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,
	2019	2018
Risk free interest rate	1.41% - 2.60%	2.40% - 3.06%
Expected term (in years)	5.00 - 5.73	4.75 - 5.73
Dividend yield	—	—
Expected volatility	81.7% - 81.8%	77.1% - 80.5%

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,
	2019		2018
Research and development	$	2,446	$	1,984
General and administrative	2,928		2,959
Total stock-based compensation	$	5,374	$	4,943

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Lease, Cost

The following table summarizes operating lease costs included in operating expenses for the twelve months ended December 31, 2019 (in thousands):



	Twelve Months Ended December 31, 2019

Operating lease costs	$	1,524
Variable lease costs (1)	293
Total lease cost	$	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.

During the year ended December 31, 2018, the Company recognized rent expense in an amount of $0.5 million under the previous guidance in ASC 840.

The following table summarizes the weighted-average remaining lease term and discount rate as of December 31, 2019:



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

Finance Lease, Liability, Maturity

As of December 31, 2019, the maturities of the Company’s operating lease liabilities and future minimum lease payments were as follows (in thousands):



	Total
2020	$	2,317
2021	2,418
2022	2,249
2023	2,214
2024	2,214
Thereafter	16,790
Total undiscounted lease payments	28,202
Less: present value adjustment	(11,985		)
Present value of lease liabilities	16,217

Corporate Information - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2019	May 31, 2013
Subsequent Event [Line Items]
Cash, cash equivalents and investments	$ 104.2
Pieris Pharmaceuticals GmbH
Subsequent Event [Line Items]
Proportion of voting interests acquired (as a percent)		100.00%

Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Investments with fair value below carrying value or in an unrealized loss position	$ 0
Allowance for doubtful accounts	0		$ 0
Operating lease right-of-use assets	3,436,000	$ 868,000	$ 0
Operating lease liability	$ 16,217,000
Accounting Standards Update 2016-02 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating lease right-of-use assets		868,000
Operating lease liability		$ 900,000

Summary of Significant Accounting Policies - Estimated Useful Life of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Laboratory Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Laboratory Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	14 years
Office Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Office Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	13 years

Summary of Significant Accounting Policies - Consolidated Balance Sheet Data (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid expenses and other current assets	$ 4,072	$ 5,290	$ 4,574
Other non-current assets	3,146	2,030	910
Total Assets	141,097	143,177	141,341
Deferred revenue, net of current portion	47,258	56,780	53,303
Total Liabilities	89,745	104,883	101,406
Accumulated deficit	(174,176)	(148,707)	(147,066)
Total stockholders' equity	51,352	38,294	39,935	$ 11,522
Total liabilities and stockholders' equity	141,097	143,177	141,341
Operating lease right-of-use assets	3,436	868	0
Deferred rent		0	35
Current operating lease liabilities	733	442	0
Non-current operating lease liabilities	$ 15,484	461	$ 0
Accounting Standards Update 2016-02 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating lease right-of-use assets		868
Deferred rent		(35)
Current operating lease liabilities		442
Non-current operating lease liabilities		461
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid expenses and other current assets		716
Other non-current assets		1,120
Total Assets		1,836
Deferred revenue, net of current portion		3,477
Total Liabilities		3,477
Accumulated deficit		(1,641)
Total stockholders' equity		(1,641)
Total liabilities and stockholders' equity		$ 1,836

Summary of Significant Accounting Policies - Condensed Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019	Dec. 31, 2017
Statement of Financial Position [Abstract]
Prepaid expenses and other current assets	$ 4,072	$ 4,574	$ 5,290
Other non-current assets	3,146	910	2,030
Assets	141,097	141,341	143,177
Deferred revenues, current portion	11,256	35,612
Deferred revenue, net of current portion	47,258	53,303	56,780
Total Liabilities	89,745	101,406	104,883
Accumulated Deficit	(174,176)	(147,066)	(148,707)
Total stockholders' equity	51,352	39,935	38,294	$ 11,522
Total liabilities and stockholders' equity	141,097	141,341	143,177
Income Statement [Abstract]
Revenue	46,279	29,101
General and administrative	18,440	18,442
Loss from operations	(27,157)	(30,831)
Loss before income taxes	(25,469)	(27,066)
Net loss	(25,469)	(26,754)
Comprehensive loss	(24,482)	$ (25,041)
Calculated under Revenue Guidance in Effect before Topic 606
Statement of Financial Position [Abstract]
Prepaid expenses and other current assets	3,948
Other non-current assets	2,331
Assets	140,158
Deferred revenues, current portion	14,638
Deferred revenue, net of current portion	38,189
Total Liabilities	84,058
Accumulated Deficit	(169,428)
Total stockholders' equity	56,100
Total liabilities and stockholders' equity	140,158
Income Statement [Abstract]
Revenue	48,594
General and administrative	17,582
Loss from operations	(25,700)
Loss before income taxes	(24,012)
Net loss	(24,012)
Comprehensive loss	(23,025)
Accounting Standards Update 2014-09
Statement of Financial Position [Abstract]
Prepaid expenses and other current assets			716
Other non-current assets			1,120
Assets			1,836
Deferred revenue, net of current portion			3,477
Total Liabilities			3,477
Accumulated Deficit			(1,641)
Total stockholders' equity			(1,641)
Total liabilities and stockholders' equity			$ 1,836
Accounting Standards Update 2014-09 \| Difference between Revenue Guidance in Effect before and after Topic 606
Statement of Financial Position [Abstract]
Prepaid expenses and other current assets	(124)
Other non-current assets	(815)
Assets	(939)
Deferred revenues, current portion	3,382
Deferred revenue, net of current portion	(9,069)
Total Liabilities	(5,687)
Accumulated Deficit	4,748
Total stockholders' equity	4,748
Total liabilities and stockholders' equity	(939)
Income Statement [Abstract]
Revenue	2,315
General and administrative	(858)
Loss from operations	1,457
Loss before income taxes	1,457
Net loss	1,457
Comprehensive loss	$ 1,457

Revenue - Revenue Generated from Non-Product Sales (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue from contract with customers	$ 43,646	$ 27,248
Collaboration revenue	2,633	1,762
Other revenues	0	91
Total Revenue	$ 46,279	$ 29,101

Revenue - Revenue From Licensing Agreements and Strategic Partnerships (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total Revenue	$ 46,279	$ 29,101
AstraZeneca
Disaggregation of Revenue [Line Items]
Total Revenue	25,828	17,632
Seattle Genetics
Disaggregation of Revenue [Line Items]
Total Revenue	2,493	5,413
Servier
Disaggregation of Revenue [Line Items]
Total Revenue	15,048	4,508
Other
Disaggregation of Revenue [Line Items]
Total Revenue	$ 2,910	$ 1,548

Revenue - Potential Milestone Payments (Details) - Strategic Partnerships and Other License Agreements - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments	$ 2,679
Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments		$ 2,117
AstraZeneca \| Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments	1,111
AstraZeneca \| Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments		960
Servier \| Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments	799
Servier \| Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments		707
Seattle Genetics \| Research, Development, Regulatory & Commercial Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments	$ 769
Seattle Genetics \| Sales Milestones
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payments		$ 450

Revenue - Narrative (Details) € in Millions												1 Months Ended				12 Months Ended
Revenue - Narrative (Details) € in Millions	Feb. 08, 2018 USD ($) swap_option research_program unit_of_accounting license	May 02, 2017 USD ($) unit_of_accounting	Feb. 27, 2017 USD ($)	Jan. 04, 2017 USD ($) product	Jan. 04, 2017 EUR (€)	Jan. 04, 2017 USD ($) product	Jan. 04, 2017 USD ($) bispecific_therapeutic_program product	Jan. 04, 2017 USD ($) research_program product	Jan. 04, 2017 USD ($) extension_option product	Jan. 04, 2017 USD ($) unit_of_accounting product	Jan. 04, 2017 USD ($) product license	Feb. 28, 2019 EUR (€)	Feb. 28, 2019 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Revenue capitalized		$ 1,100,000
Capitalized transaction cost, net																$ 300,000
Revenues																46,279,000	$ 29,101,000
Additions to contract with customer, liability																0
Contract with customer, liability, revenue recognized																32,200,000
Seattle Genetics
Disaggregation of Revenue [Line Items]
Remaining performance obligation																24,700,000
Revenues																2,493,000	5,413,000
AstraZeneca
Disaggregation of Revenue [Line Items]
Remaining performance obligation																26,000,000
Capitalized contract cost, net		$ 1,600,000
Capitalized transaction cost, net																700,000
Capitalized contract cost, amortization																400,000
Research collaboration agreement term		5 years
Revenues																25,828,000	17,632,000
Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Remaining performance obligation																19,400,000
Capitalized contract cost, net				$ 0		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Capitalized contract cost, amortization																200,000
Revenues																15,048,000	4,508,000
Les Laboratoires Servier and Institut de Recherches Internationales Servier \| Research and Development Services
Disaggregation of Revenue [Line Items]
Research collaboration agreement term				3 years
ASKA Pharmaceutical Co. Ltd.
Disaggregation of Revenue [Line Items]
Capitalized contract cost, net			$ 300,000
Capitalized contract cost, amortization																300,000
Evaluation period			60 days
License and Collaboration Agreement \| Seattle Genetics
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	90 days
Contract termination due to material breach, additional notice period if the breach is not susceptible	90 days
Number of licenses \| license	3
Number of swap options \| swap_option	2
Number of performance obligations \| unit_of_accounting	6
Number of research programs \| research_program	3
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
Agreement termination notice period upon breach of payment obligations by the Company		30 days
Contract termination due to material breach, additional notice period if the breach is not susceptible		180 days
Number of performance obligations \| unit_of_accounting		16
License and Collaboration Agreement \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Number of licenses \| license											5
Number of performance obligations \| unit_of_accounting										10
Number of research programs							5	3
Sales Milestones \| Seattle Genetics
Disaggregation of Revenue [Line Items]
Current deferred revenue																4,500,000
Non-current deferred revenue																16,000,000
Sales Milestones \| AstraZeneca
Disaggregation of Revenue [Line Items]
Current deferred revenue																1,000,000
Non-current deferred revenue																17,500,000
Sales Milestones \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Deferred revenue																5,700,000
Non-current deferred revenue																$ 13,700,000
Strategic Partnerships and Other License Agreements \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Period after effective date agreements may be terminated				12 months
Contract termination advance notice period				180 days
Revenues												€ 1.5	$ 1,700,000	€ 0.5	$ 600,000
Number of collaboration products \| product				4		4	4	4	4	4	4
Strategic Partnerships and Other License Agreements \| ASKA Pharmaceutical Co. Ltd.
Disaggregation of Revenue [Line Items]
Revenues																	$ 0
Upfront Payment \| Seattle Genetics
Disaggregation of Revenue [Line Items]
Proceeds from advances for research and development services	$ 30,000,000
Collaboration revenue (ASC 808)	4,900,000
Deferred revenue	$ 1,200,000,000
Upfront Payment \| AstraZeneca
Disaggregation of Revenue [Line Items]
Allocable arrangement consideration		$ 45,000,000
Upfront Payment \| ASKA Pharmaceutical Co. Ltd.
Disaggregation of Revenue [Line Items]
Upfront option payment received			$ 2,750,000
Upfront Payment \| Strategic Partnerships and Other License Agreements \| Les Laboratoires Servier and Institut de Recherches Internationales Servier
Disaggregation of Revenue [Line Items]
Proceeds from advances for research and development services					€ 30.0	$ 32,000,000
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
Extension Term \| Les Laboratoires Servier and Institut de Recherches Internationales Servier \| Research and Development Services
Disaggregation of Revenue [Line Items]
Research collaboration agreement term				1 year
Number of agreement extension options \| extension_option									2
Sales Milestones \| 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
Minimum \| Strategic Partnerships and Other License Agreements \| 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
Maximum \| Strategic Partnerships and Other License Agreements \| 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

Cash, Cash Equivalents and Investments - Cash Equivalents and Investments Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	$ 47,384	$ 7,791
Corporate bonds, included in cash equivalents		10,910
Investments - US treasuries	5,300	7,518
Investments - Asset-backed securities	7,950	5,758
Investments - Corporate bonds	28,644	39,964
Total	89,278	71,941
Quoted prices in active markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	47,384	7,791
Corporate bonds, included in cash equivalents		0
Investments - US treasuries	5,300	7,518
Investments - Asset-backed securities	0	0
Investments - Corporate bonds	0	0
Total	52,684	15,309
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	0	0
Corporate bonds, included in cash equivalents		10,910
Investments - US treasuries	0	0
Investments - Asset-backed securities	7,950	5,758
Investments - Corporate bonds	28,644	39,964
Total	36,594	56,632
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	0	0
Corporate bonds, included in cash equivalents		0
Investments - US treasuries	0	0
Investments - Asset-backed securities	0	0
Investments - Corporate bonds	0	0
Total	$ 0	$ 0

Cash, Cash Equivalents and Investments - Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 41,964	$ 53,379
Unrealized gains	57	4
Unrealized losses	(127)	(143)
Fair Value	41,894	53,240
US treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	5,293	7,541
Unrealized gains	25	0
Unrealized losses	(18)	(23)
Fair Value	$ 5,300	$ 7,518
US treasuries \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity	46 days	150 days
US treasuries \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity	182 days	164 days
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 7,962	$ 5,766
Unrealized gains	12	1
Unrealized losses	(24)	(9)
Fair Value	$ 7,950	$ 5,758
Asset-backed securities \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity	49 days	196 days
Asset-backed securities \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity	106 days	259 days
Asset-backed securities, greater than 365 \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity		365 days
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 28,709	$ 40,072
Unrealized gains	20	3
Unrealized losses	(85)	(111)
Fair Value	$ 28,644	$ 39,964
Corporate bonds \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity	2 days	73 days
Corporate bonds \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity	204 days	252 days
Corporate bonds, greater than 365 \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity		365 days

Cash, Cash Equivalents and Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Realized gain (loss) on investments	$ 0.3	$ 1.0

Property and Equipment, Net - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 23,069	$ 8,415
Accumulated depreciation	(3,567)	(3,366)
Property and equipment, net	19,502	5,049
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	11,635	7,431
Office and computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	724	661
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 10,710	$ 323

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 632	$ 570

Accrued Expenses - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Accrued expenses
Accrued accounts payable	$ 4,251		$ 943
Compensation expense	2,870		2,380
Research and development fees	1,048		1,945
Lease liabilities	733	$ 442	0
Audit and tax fees	522		378
Other current liabilities	458		945
Accrued license obligations	62		2,523
Total	$ 9,944		$ 9,114

Income Taxes - Loss Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic	$ (12,063)	$ (10,633)
Foreign	(13,406)	(16,433)
Loss before income taxes	$ (25,469)	$ (27,066)

Income Taxes - Components of the Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 0	$ 0
State	0	0
Foreign	0	(148)
Total current	0	(148)
Deferred:
Federal	0	0
State	0	0
Foreign	0	(164)
Total deferred	0	(164)
(Benefit) provision for income taxes	$ 0	$ (312)

Income Taxes - Reconciliation of Federal Statutory Rate to the Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal income tax rate	21.00%	21.00%
Tax Reform - Change in enacted rate	0.00%	0.00%
Foreign rate differential	1.90%	7.40%
State tax, net of federal benefit	2.60%	0.70%
US tax on foreign income	(1.20%)	(8.10%)
Share-based awards compensation	(2.50%)	2.00%
Permanent items	(1.00%)	0.80%
Other	0.80%	0.50%
Rate change - trade tax NOL	(6.40%)	0.00%
Change in valuation allowance	(15.20%)	(23.10%)
Effective income tax rate	0.00%	1.20%

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 30,455	$ 27,879
Share-based awards compensation	2,705	2,359
Accrued expenses	328	304
Depreciation and other	53	125
Deferred revenue	0	641
Unrealized foreign currency	90	0
Lease liability	4,378	0
Total deferred tax assets	38,009	31,308
Deferred tax liabilities:
Right-of-use asset	(4,043)	0
Unrealized gain on investments	0	(394)
Other	0	(98)
Total deferred tax liabilities	(4,043)	(492)
Less: valuation allowance:	(33,966)	(30,816)
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, 2019 USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 6,157
Currency translation adjustment	(125)
Unrecognized tax benefits, ending balance	$ 6,032

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
Income Taxes - Narrative (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Increase in the valuation allowance	$ (3,200,000)
Uncertain tax positions interest and penalties accrued	0	$ 0
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	20,100,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	26,700,000
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	90,500,000
Germany \| Trade Tax Carryforwards
Income Taxes [Line Items]
Net operating loss carryforwards	$ 89,700,000

Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Aug. 09, 2019 USD ($)	Jan. 30, 2019 shares	Nov. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Jun. 30, 2019 $ / shares shares	Jan. 31, 2019 shares
Class of Stock [Line Items]
Issuance of common stock resulting from exercise of stock options (shares)					279,075	596,269
Cash proceeds from option exercises \| $					$ 553	$ 986
Number of shares called by warrants (shares)					123,238	156,888
Cash proceeds from exercise of warrants \| $					$ 246	$ 314
Preferred stock, shares authorized (shares)					10,000,000	10,000,000
Number of shares per unit (shares)				1
Warrant exercise period				5 years
Par value of preferred stock (USD per share) \| $ / shares					$ 0.001	$ 0.001
Par value of common stock (USD per share) \| $ / shares					$ 0.001	$ 0.001
Gross sales proceeds from common stock \| $	$ 50,000
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Price per unit issued (USD per share) \| $ / shares				$ 2.015
Number of shares per unit (shares)				1
Shares issued upon conversion of convertible preferred stock (shares)				1,000
Proportion of beneficial ownership (as a percent)				9.99%
Par value of preferred stock (USD per share) \| $ / shares				$ 0.001
Shares of preferred stock issued (shares)					2,907	2,907
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Shares of preferred stock issued (shares)					5,000	0
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Shares of preferred stock issued (shares)					3,522	0
Tranche A Warrants
Class of Stock [Line Items]
Number of shares called by warrants (shares)				0.4
Number of warrants				1
Exercise price (USD per share) \| $ / shares				$ 2.00
Tranche B Warrants
Class of Stock [Line Items]
Number of shares called by warrants (shares)				0.2
Number of warrants				1
Exercise price (USD per share) \| $ / shares				$ 3.00
Common Stock
Class of Stock [Line Items]
Issuance of common stock resulting from exercise convertible securities (shares)					52,833
Number of shares called by warrants (shares)					127,065
Warrants
Class of Stock [Line Items]
Issuance of common stock resulting from exercise convertible securities (shares)					176,071
Common Shares
Class of Stock [Line Items]
Issuance of common stock resulting from exercise of stock options (shares)					279,000	596,000
Issuance of common stock resulting from exercise convertible securities (shares)					176,000	157,000
Preferred Shares \| Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (shares)								5,000
Common stock ownership limit (as a percent)							9.99%
Beneficial ownership limitation (as a percent)							19.99%
Effective period of change to beneficial ownership limitation					61 days
Shares issued upon conversion of convertible preferred stock (shares)							1,000
Par value of preferred stock (USD per share) \| $ / shares							$ 0.001
Preferred Shares \| Series C Convertible Preferred Stock
Class of Stock [Line Items]
Common stock ownership limit (as a percent)			9.99%
Shares issued upon conversion of convertible preferred stock (shares)			1,000
Private Placement
Class of Stock [Line Items]
Shares of common stock issued (shares)			9,015,000
Issue price per share (USD per share) \| $ / shares			$ 3.55
Net proceeds from underwritten public offering \| $			$ 31,000
Number of shares per unit (shares)			1
Exercise price (USD per share) \| $ / shares			$ 7.10
Warrant exercise period			5 years
Shares of stock sold, gross consideration \| $			$ 32,000
Number of warrants included with each unit (in shares)			1
Private Placement \| Series C Convertible Preferred Stock
Class of Stock [Line Items]
Shares issued upon conversion of convertible preferred stock (shares)			0.001
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
2016 PIPE
Class of Stock [Line Items]
Shares of common stock issued (shares)				3,225,804
Stock Exchange, Shares from Existing Shareholders \| Common Shares
Class of Stock [Line Items]
Shares of common stock issued (shares)		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 \| Preferred Shares
Class of Stock [Line Items]
Shares of common stock issued (shares)		5,000
2016 PIPE \| Private Placement \| Series A Convertible Preferred Stock
Class of Stock [Line Items]
Shares of preferred stock issued (shares)				4,963

Net Loss per Share - Narrative (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Anti-dilutive stock excluded from calculation of weighted average shares outstanding (shares)	33.4	14.7

Stock and Employee Benefit Plans - Narrative (Details)	1 Months Ended	12 Months Ended
Stock and Employee Benefit Plans - Narrative (Details)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) purchase_period $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Defined Benefit Plan Disclosure [Line Items]
Issuance of common stock resulting from purchase of employee stock purchase plan shares (shares)		113,112
Stock-based compensation expense \| $		$ 5,374,000	$ 4,943,000
Unrecognized compensation costs related to nonvested awards \| $		$ 9,300,000
Weighted-average compensation cost recognition period		2 years 5 months 15 days
Purchases during period \| $		$ 369,000
Research and development
Defined Benefit Plan Disclosure [Line Items]
Stock-based compensation expense \| $		2,446,000	1,984,000
General and administrative
Defined Benefit Plan Disclosure [Line Items]
Stock-based compensation expense \| $		$ 2,928,000	$ 2,959,000
2016 Stock Plan
Defined Benefit Plan Disclosure [Line Items]
Stock available for future grant (shares)		654,000
Common stock authorized for issuance (shares)		3,000,000
Maximum term of stock options		10 years
Number of options granted (shares)		2,489,269	1,881,660
Weighted-average fair value (USD per share) \| $ / shares		$ 2.31	$ 5.04
2018 Stock Plan
Defined Benefit Plan Disclosure [Line Items]
Stock available for future grant (shares)		2,912,721
Stock issuable under plan (shares)		5,750,000
Common stock authorized for issuance (shares)		2,750,000
Executive Officers and Senior Leadership
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation costs related to nonvested awards \| $		$ 1,200,000
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 \| purchase_period		2
Term of purchase period		6 months
Purchases during period \| $	$ 0

Stock and Employee Benefit Plans - Fair Value Assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, minimum (as a percent)	1.41%	2.40%
Risk free interest rate, maximum (as a percent)	2.60%	3.06%
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility, minimum (as a percent)	81.70%	77.10%
Expected volatility, maximum (as a percent)	81.80%	80.50%
Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years	4 years 9 months
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)	1.61%	2.48%
Expected term (in years)	6 months	6 months
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility (as a percent)	78.10%	57.57%

Stock and Employee Benefit Plans - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Options
Exercised (shares)	279,075	596,269
2014 and 2016 Stock Plans
Number of Options
Outstanding (shares)	6,850,047
Granted (shares)	2,189,269
Exercised (shares)	279,075
Canceled (shares)	(500,326)
Outstanding (shares)	8,259,915	6,850,047
Vested or expected to vest (shares)	8,259,915
Exercisable (shares)	4,908,300
Weighted- Average Exercise Price
Outstanding (USD per share)	$ 3.76
Granted (USD per share)	3.16
Exercised (USD per share)	1.98
Canceled (USD per share)	4.70
Outstanding (USD per share)	3.60	$ 3.76
Vested or expected to vest (USD per share)	3.60
Exercisable (USD per share)	$ 3.11
Weighted- Average Remaining Contractual Life
Outstanding	7 years 3 months
Vested or expected to vest	7 years 3 months
Exercisable	6 years 3 months 25 days
Aggregate Intrinsic Value
Outstanding	$ 3,257
Granted	0
Exercised	486
Canceled	288
Outstanding	7,987	$ 3,257
Vested or expected to vest	7,987
Exercisable	$ 6,348
Executive Officers and Senior Leadership
Number of Options
Outstanding (shares)	1,125,000
Exercised (shares)	300,000
Canceled (shares)	(225,000)
Outstanding (shares)	1,200,000	1,125,000
Vested or expected to vest (shares)	1,200,000
Exercisable (shares)	812,500
Weighted- Average Exercise Price
Outstanding (USD per share)	$ 4.41
Exercised (USD per share)	4.65
Canceled (USD per share)	5.00
Outstanding (USD per share)	4.36	$ 4.41
Vested or expected to vest (USD per share)	4.36
Exercisable (USD per share)	$ 4.08
Weighted- Average Remaining Contractual Life
Outstanding	5 years 11 months 4 days
Vested or expected to vest	5 years 11 months 4 days
Exercisable	4 years 4 months 5 days
Aggregate Intrinsic Value
Outstanding	$ 0
Granted	0
Canceled	0
Outstanding	130	$ 0
Vested or expected to vest	130
Exercisable	$ 130

Stock and Employee Benefit Plans - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 5,374	$ 4,943
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	2,446	1,984
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,928	$ 2,959

License Agreement - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Contingencies And Commitments [Line Items]
Accrued accounts payable	$ 62	$ 2,523
TUM License
Contingencies And Commitments [Line Items]
Accrued accounts payable	$ 2,300

Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2019 USD ($) ft² extension_option lease_agreement	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Lease term			12 years 6 months
Rent expense \| $	$ 11.5			$ 0.5
Lease Liabilities \| $			$ 0.5
Freising, Germany
Loss Contingencies [Line Items]
Number of lease agreements \| lease_agreement			4
Area of leased property			19,000
Boston, Massachusetts
Loss Contingencies [Line Items]
Area of leased property			3,950
Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property		105,000
Number of agreement extension options \| extension_option			2
Lease extension term			60 months
Rent expense \| $			$ 0.2
Security deposit \| $		$ 0.8		$ 0.8
Leases in Same Building \| Freising, Germany
Loss Contingencies [Line Items]
Number of lease agreements \| lease_agreement			3
Leases Expected to be Delivered by December 2019 \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property		96,400
Leases Expected to be Delivered by May 2020 \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property		8,600
Leases Expected to be Delivered by October 2024 \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property		22,300
Leases with First Right of Refusal for Additional Area \| Hallbergmoos, Germany
Loss Contingencies [Line Items]
Area of leased property		13,400

Commitments and Contingencies - Balance Sheet Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets [Abstract]
Operating lease right-of-use assets	$ 3,436	$ 868	$ 0
Liabilities, Current [Abstract]
Operating lease liabilities	733	442	0
Liabilities, Noncurrent [Abstract]
Operating lease liabilities, net of current portion	15,484	$ 461	$ 0
Total lease liabilities	$ 16,217

Commitments and Contingencies - Lease Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 1,524
Variable lease costs	293
Total lease cost	$ 1,817

Commitments and Contingencies - Summary of the Lease Term and Discount Rate (Details)	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years)	12 years 1 month 6 days
Weighted-average discount rate	10.50%

Commitments and Contingencies - Maturities of the Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2020	$ 2,317
2021	2,418
2022	2,249
2023	2,214
2024	2,214
Thereafter	16,790
Total undiscounted lease payments	28,202
Less: present value adjustment	(11,985)
Present value of lease liabilities	$ 16,217