0001437749-24-010123 | 10-K | XBRL Viewer | Pieris Pharmaceuticals INC

Note 9 - Stockholders' Equity

12 Months Ended

Dec. 31, 2023

9.	Stockholders’ equity

The Company had 300,000,000 shares authorized and 98,935,025 and 74,519,103 shares of common stock issued and outstanding as of December 31, 2023 and December 31, 2022, respectively, with a par value of $0.001 per share.

The Company had 10,000,000 shares authorized and 15,617 shares of preferred stock issued and outstanding as of December 31, 2023 and 2022. Preferred stock has a par value of $0.001 per share, and consists of the following tranches:

•

Series A Convertible, 85 shares issued and outstanding at December 31, 2023 and 2022

•

Series B Convertible, 4,026 shares issued and outstanding at December 31, 2023 and 2022

•

Series C Convertible, 3,506 shares issued and outstanding at December 31, 2023 and 2022

•

Series D Convertible, 3,000 shares issued and outstanding at December 31, 2023 and 2022

•

Series E Convertible, 5,000 shares issued and outstanding at December 31, 2023 and 2022

Common Stock

Each share of the Company’s common stock is entitled to one vote and all shares rank equally as to voting and other matters. Dividends may be declared and paid on the common stock from funds legally available therefor, if, as and when determined by the Board of Directors.

Preferred Stock

The Company has issued multiple series (Series A through E) of preferred stock to certain entities affiliated with Biotechnology Value Fund, L.P., or BVF. In each case, each share Preferred Stock is convertible into 1,000 shares of the Company's common stock (subject to adjustment as provided in the Certificate of Designation for each series) at any time at the option of the holder, provided that the holder is prohibited from converting the 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.

Series A, Series B, Series C, Series D and Series E Preferred Stock rank senior to the Company’s common stock; senior to any class or series of capital stock of the Company created after the designation of and specifically ranking by its terms as junior to the five series of Preferred Stock; in parity with each other and with any class or series of capital stock of the Company created after the designation of and specifically ranking by its terms as in parity with the existing five series of Preferred Stock; and junior to any class or series of capital stock of the Company created after the designation of and specifically ranking by its terms as senior to the existing five series of Preferred Stock. In the event of the Company’s liquidation, dissolution or winding up, subject to the rights of holders of, holders are entitled to receive a payment equal to $0.001 per share of Preferred Stock pursuant to the rights and preferences discussed above, 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 existing five series of Preferred Stock.

For each series of Preferred Stock, the Company designated the requisite number of shares of its authorized and unissued preferred stock as a specific series of Preferred Stock and filed a Certificate of Designation with the Nevada Secretary of State.

Shares of 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 Preferred Stock is required to amend the terms of the Certificate of Designation for each respective series of Preferred Stock. Holders of Preferred Stock are entitled to receive any dividends payable to holders of the Company's common stock subject to the rights and preferences discussed above, 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.

Series A Preferred Stock

In June 2016, the Company entered into a 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. 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 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.

Series C and 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. 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 0.001 shares of non-voting 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 elarekibep 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.

Upon issuance, each Series C Preferred Share included an embedded beneficial conversion feature as the market price of the Company’s common stock on the date of issuance of the Series C convertible Preferred Stock was $3.43 per share. As a result, the Company recorded the intrinsic value of the beneficial conversion feature of $2.8 million as a discount on the Series C convertible preferred stock at issuance. As the Series C Preferred Shares are immediately convertible upon issuance and do not include a stated redemption date, the discount was immediately accreted as a deemed dividend.

Series D Preferred Stock Conversion

On March 31, 2020, the Company and certain entities affiliated with BVF entered into an exchange agreement pursuant to which, on April 1, 2020, BVF exchanged an aggregate of 3,000,000 shares of the Company’s common stock owned by BVF for an aggregate of 3,000 shares of Series D Preferred Stock.

Series E Preferred Stock Conversion

On May 20, 2021, the Company and certain entities affiliated with BVF entered into an exchange agreement pursuant to which, BVF exchanged 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 E Preferred Stock.

Open Market Sales Agreement

In August 2021, the Company established an at-the-market program, or ATM Program, under a sales agreement with Jefferies LLC, pursuant to which the Company may offer and sell shares of its common stock, par value $0.001 per share, from time to time, up to an aggregate amount of gross sales proceeds of $50.0 million. In November 2022, the sales agreement was amended to provide for an increase in the aggregate offering amount, such that under the ATM Program, as amended, the Company may offer and sell shares of its common stock, from time to time, up to an aggregate amount of gross sales proceeds of $75.0 million. The ATM Program, as amended, is offered under a shelf registration statement on Form S-3 that was filed with and declared effective by the SEC in August 2021. For the year ended December 31, 2023, the Company sold 24.3 million shares for gross proceeds of $20.3 million under the ATM Program at an average stock price of $0.84. For the year ended December 31, 2022, the Company sold 2.1 million shares for gross proceeds of $7.2 million under the ATM Programs and the predecessor ATM program at an average stock price of $3.46.

As of the filing of this Annual Report on Form 10-K, the Company will be subject to the SEC general instructions of Form S-3 known as the “baby shelf rules.” Under these instructions, the amount of funds the Company can raise through primary public offerings of securities in any 12-month period using its registration statement on Form S-3 is limited to one-third of the aggregate market value of the shares of the Company’s common stock held by non-affiliates. Therefore, the Company will be limited in the amount of proceeds it is able to raise by selling shares of its common stock using its Form S-3, including under the ATM Program, until such time as its public float exceeds $75 million.

- Definition

The entire disclosure for equity.

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+ Details

Note 1 - Corporate Information (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Mar. 27, 2024	Jul. 18, 2023	May 31, 2013
Reduction in Workforce, Percentage				70.00%
Reduction in Workforce, Cost	$ 7,500
Cash, Cash Equivalents, and Short-Term Investments	26,400
Net Income (Loss) Attributable to Parent	(24,543)	$ (33,277)
Retained Earnings (Accumulated Deficit)	$ (314,964)	$ (290,421)
Subsequent Event [Member] \| B P Assets X I I Inc [Member] \| License [Member] \| Exclusive Product License Agreement [Member] \| Phase 2 Trials [Member]
Contracts Receivable, Claims and Uncertain Amounts			$ 20,000
Subsequent Event [Member] \| B P Assets X I I Inc [Member] \| License [Member] \| Exclusive Product License Agreement [Member] \| Pivotal Clinical Trials [Member]
Contracts Receivable, Claims and Uncertain Amounts			$ 55,000
Pieris Pharmaceuticals GmbH [Member]
Business Acquisition, Percentage of Voting Interests Acquired					100.00%

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 17,396	$ 38,635
Short term investments	8,970	20,534
Accounts receivable	572	5,810
Receivable from public grants	3,141	4,771
Other receivables	2,326	462
Assets held for sale, property and equipment	2,188	0
Prepaid expenses and other current assets	4,087	3,212
Total current assets	38,680	73,424
Property and equipment, net	0	16,992
Operating lease right-of-use assets, non-current	0	3,705
Other non-current assets	0	1,369
Total assets	38,680	95,490
Current liabilities:
Accounts payable	3,372	4,154
Operating lease liabilities, current	0	859
Accrued expenses and other current liabilities	8,550	10,746
Deferred revenues, current portion	0	20,824
Total current liabilities	11,922	36,583
Deferred revenue, net of current portion	0	18,734
Operating lease liabilities, non-current	0	12,244
Total liabilities	11,922	67,561
Commitments and Contingencies
Stockholders’ equity:
Convertible preferred stock, $0.001 par value per share, 10,000,000 shares authorized and 15,617 shares issued and outstanding at December 21, 2023 and 2022	0	0
Common stock, $0.001 par value per share, 300,000,000 shares authorized and 98,935,025 and 74,519,103 shares issued and outstanding at December 21, 2023 and 2022, respectively	98	74
Additional paid-in capital	341,596	318,530
Accumulated other comprehensive income	28	(254)
Accumulated deficit	(314,964)	(290,421)
Total stockholders’ equity	26,758	27,929
Total liabilities and stockholders’ equity	$ 38,680	$ 95,490

Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
At the Market Offering [Member]
Stock issuance costs		$ 0.3
Stock issuance costs	$ 0.7

Note 8 - Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Federal	$ 0	$ 0
State	0	0
Foreign, tax expense	0	0
Total current	0	0
Federal, deferred	0	0
State, deferred	0	0
Foreign, deferred	0	0
Total deferred	0	0
Provision for income taxes	$ 0	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Note 10 - Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Earnings Per Share [Text Block]

10.

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, 2023 and 2022, and as calculated using the treasury stock method, approximately 39.4 million and 38.4 million of weighted average shares, respectively, were excluded from the calculation of diluted weighted average shares outstanding as their effect was antidilutive.

Insider Trading Arrangements

12 Months Ended

Dec. 31, 2023

Insider Trading Arr Line Items

Material Terms of Trading Arrangement [Text Block]

Item 9B.

OTHER INFORMATION

Not applicable.

Rule 10b5-1 Arrangement Adopted [Flag]

false

Non-Rule 10b5-1 Arrangement Adopted [Flag]

false

Rule 10b5-1 Arrangement Terminated [Flag]

false

Non-Rule 10b5-1 Arrangement Terminated [Flag]

false

Note 8 - Income Taxes - Summary of Income Tax Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Unrecognized tax benefits at December 31, 2022	$ 5,363
Decrease as a result of a lapse of the applicable statute of limitations	(5,363)
Unrecognized tax benefits at December 31, 2023	$ 0

Note 11 - Stock and Employee Benefit Plans - Schedule of Share-based Payment Award, Stock Options (Details) - Share-Based Payment Arrangement, Option [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Risk free interest rate, minimum	3.33%	1.43%
Risk free interest rate, maximum	4.11%	3.39%
Dividend yield	0.00%	0.00%
Expected volatility, minimum	79.50%	79.90%
Expected volatility, maximum	98.60%	81.10%
Minimum [Member]
Expected term (in years) (Year)	5 years 6 months	5 years 6 months
Maximum [Member]
Expected term (in years) (Year)	5 years 8 months 23 days	5 years 8 months 23 days

Note 3 - Revenue - Potential Milestone Payments Received (Details) - Collaborative Arrangement [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Research And Development Milestone Payments [Member]
milestone	$ 951
Research And Development Milestone Payments [Member] \| Pfizer [Member]
milestone	759
Research And Development Milestone Payments [Member] \| Servier Developed Collaboration Products [Member]
milestone	107
Research And Development Milestone Payments [Member] \| Boston Pharmaceuticals [Member]
milestone	$ 85
Sales Milestone Payments [Member]
milestone		$ 814
Sales Milestone Payments [Member] \| Pfizer [Member]
milestone		450
Sales Milestone Payments [Member] \| Servier Developed Collaboration Products [Member]
milestone		99
Sales Milestone Payments [Member] \| Boston Pharmaceuticals [Member]
milestone		$ 265

Note 6 - Assets Held for Sale, Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Disclosure of Long-Lived Assets Held-for-Sale [Table Text Block]

	*December 31,*
	*2023*
Laboratory furniture and equipment	$	1,967
Office furniture and equipment		221
Assets held for sale	$	2,188

Property, Plant and Equipment [Table Text Block]

	December 31,
	2022
Laboratory furniture and equipment	$	11,970
Office furniture and equipment		1,861
Computer equipment		364
Leasehold improvements		12,444
Property and equipment, cost		26,639
Accumulated depreciation		(9,647	)
Property and equipment, net	$	16,992

Note 6 - Assets Held for Sale, Property and Equipment - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property and equipment, cost		$ 26,639
Accumulated depreciation		(9,647)
Property and equipment, net	$ 0	16,992
Laboratory Equipment [Member]
Property and equipment, cost		11,970
Office Equipment [Member]
Property and equipment, cost		1,861
Computer Equipment [Member]
Property and equipment, cost		364
Leasehold Improvements [Member]
Property and equipment, cost		$ 12,444

Note 2 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Property, Plant and Equipment, Estimated Useful Life [Table Text Block]

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

Note 1 - Corporate Information

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]

1.	Corporate Information

Pieris Pharmaceuticals, Inc., or the Company or Pieris, 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 biopharmaceutical company that, prior to July of 2023, discovered and developed Anticalin-based drugs to target validated disease pathways in unique and transformative ways. Pieris’ clinical pipeline consists of immuno-oncology, or IO, programs partnered with several major multi-national pharmaceutical companies. Pieris' corporate headquarters is located in Boston, Massachusetts. Pieris also maintains office space in Hallbergmoos, Germany.

The Company’s core Anticalin technology and platform was developed in Germany.

On July 18, 2023, the Company announced its intention to explore engaging in one or more strategic transactions, including mergers, reverse mergers, acquisitions, other business combinations or sales of assets, or other strategic transactions. This decision was related to events that impacted the Company’s inhaled respiratory franchise, based upon AstraZeneca's discontinuation of enrollment of the Phase 2a study for elarekibep, an inhaled IL-4Rα antagonist Anticalin protein to treat uncontrolled asthma. As part of this initiative, the Company engaged Stifel, Nicolaus & Company, Incorporated to serve as its advisor in its review of strategic transactions.

Also on July 18, 2023, the Company’s board of directors approved a reduction in the Company’s workforce by approximately 70%. Since July of 2023, and through December 31, 2023, the Company took additional steps to reduce its operating footprint including terminating its remaining lease obligations in Germany and winding down its proprietary inhaled respiratory programs. The Company also has opted out and terminated programs where possible to reduce operating costs. Further reductions in the workforce have occurred based upon these actions. As a result, the Company has incurred approximately $7.5 million of severance costs and other related termination benefits in 2023 as the service period to earn such benefits is considered complete. The Company expects termination benefits to be paid through the end of 2024.

On March 27, 2024, the Company announced the implementation of a new strategy along with relevant cost-saving measures that are expected to extend its cash runway into at least 2027, while maximizing its ability to capture the potential milestones from its partnered 4-1BB bispecific Mabcalin protein IO assets. The Company may be entitled to aggregate milestones of up to $20 million upon first patient dosed in the phase 2 trials for SGN-BB228, S095012 (formerly PRS-344) and BOS-342, which are all currently in phase 1 clinical development, and up to $55 million upon first patient dosed in pivotal clinical trials for SGN-BB228, S095012 and BOS-342. To support this new strategy, the Company plans to discontinue all of its research and development efforts which it expects to complete by the middle of 2024, implement a workforce reduction that will impact additional employees and the executive leadership team which is expected to be implemented in the second quarter of 2024, and reduce the size of its Board of Directors, which is also expected to have implemented in the second quarter of 2024. In addition to the alliance management activities for its partnered programs, the Company remains committed to obtaining value for its products in prior development, including cinrebafusp alfa, as well as its proprietary platform capabilities by pursuing potential out-licensing or sales transactions. In addition to these potential transactions, the Company may also, from time-to-time, consider strategic opportunities that it believes may increase stockholder value.

As of December 31, 2023, cash, cash equivalents, and investments were $26.4 million. The Company’s net loss was $24.5 million and $33.3 million for the years ended December 31, 2023 and 2022, respectively. The Company has incurred net losses since inception and had an accumulated deficit of $315.0 million as of December 31, 2023. Net losses and negative cash flows have had, and will continue to have, an adverse effect on the Company’s stockholders’ equity and working capital. The Company expects to continue to incur operating losses for the foreseeable future.

The Company has historically devoted substantially all of its financial resources and efforts to research and development and general and administrative expenses to support the discovery and development of Anticalin-based drugs. Going forward, as part of the Company's decision to implement measures to maximize its ability to capture potential milestones from its partnered programs with Pfizer, Boston Pharmaceuticals, and Servier, the Company plans to discontinue all research and development efforts and reduce discretionary expenditures and other fixed or variable personnel costs. The Company believes that its currently available funds will be sufficient to fund its operations through at least the next twelve months from the issuance of this Annual Report on Form 10-K. The Company's belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding.

Note 5 - Cash, Cash Equivalents and Investments - Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Amortized cost	$ 8,969
Unrealized gains	1
Unrealized losses	0
Fair Value	8,970
US Treasury Securities [Member]
Amortized cost	8,969
Unrealized gains	1
Unrealized losses	0
Fair Value	$ 8,970	$ 3,573
US Treasury Securities [Member] \| Minimum [Member]
Contractual Maturity Period (Day)	4 days
US Treasury Securities [Member] \| Maximum [Member]
Contractual Maturity Period (Day)	51 days

Note 11 - Stock and Employee Benefit Plans (Details Textual) - USD ($) $ / shares in Units, $ in Millions					12 Months Ended
	Jun. 20, 2023	Jun. 22, 2022	Jun. 25, 2021	Apr. 01, 2020	Dec. 31, 2023	Dec. 31, 2022	Jun. 23, 2020
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)					3,727,942	3,075,282
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value (in dollars per share)					$ 0.85	$ 1.96
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					9,284,808
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)					154,656	181,466
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount					$ 4.3
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)					2 years 2 months 26 days
Share-Based Payment Arrangement, Option [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)					750,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent					85.00%
Employee Director And Consultant Equity Incentive Plan2020 [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	14,750,000		5,750,000				3,500,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)	6,000,000	3,000,000	2,250,000	3,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)						10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)					3,727,942

Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 11,900
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	0	$ 0
Domestic Tax Authority [Member]
Operating Loss Carryforwards	43,400
Domestic Tax Authority [Member] \| Research and Development Tax [Member
Tax Credit Carryforward, Amount	$ 500	300
Domestic Tax Authority [Member] \| Internal Revenue Service (IRS) [Member]
Open Tax Year	2019 2020 2021 2022 2023
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	$ 46,700
State and Local Jurisdiction [Member] \| Research and Development Tax [Member
Tax Credit Carryforward, Amount	100	$ 100
Foreign Tax Authority [Member] \| Corporate Income Tax [Member]
Operating Loss Carryforwards	187,600
Foreign Tax Authority [Member] \| Trade Tax [Member]
Operating Loss Carryforwards	$ 183,700

Note 10 - Net Loss Per Share (Details Textual) - shares shares in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	39.4	38.4

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Accounting, Policy [Policy Text Block]

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; fair value of held for sale assets; beneficial conversion features; fair value of stock options, preferred stock, and warrants; and prepaid and accrued clinical trial expenses. Management evaluates its estimates on an ongoing basis. Actual results and outcomes could differ materially from management’s estimates, judgments, and assumptions.

Foreign Currency Transactions and Translations Policy [Policy Text Block]

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 (loss) on the Company's balance sheet per Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 830, Foreign Currency Matters.

Cash and Cash Equivalents, Policy [Policy Text Block]

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 income (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 (expense).

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

Concentration Risk, Credit Risk, Policy [Policy Text Block]

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, Policy [Policy Text Block]

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, if any (Note 5).

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

Fair Value of Financial Instruments, Policy [Policy Text Block]

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 [Policy Text Block]

Accounts Receivable

Accounts receivable are recorded net of allowances for credit losses 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 credit losses is necessary. The Company determined that no such reserve is needed as of December 31, 2023 and 2022. Historically, the Company has not had collectability issues.

Property, Plant and Equipment, Policy [Policy Text Block]

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. Substantially all of the Company's fixed assets are located in Germany. The estimated useful life of the different groups of property and equipment is as follows:

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

If the criteria in ASC 360 Property, Plant and Equipment are met, a long-lived asset is classified as held for sale. The long-lived asset is reported at the lower of its carrying value or fair value less cost to sell beginning in the period the held for sale criteria are met. The carrying amount of the asset will be adjusted each reporting period for subsequent changes in fair value less cost to sell. A loss is recognized for any subsequent write-down to fair value less cost to sell. A gain is recognized for any subsequent increase in fair value less cost to sell, but not in excess of the cumulative loss previously recognized. Once classified as held for sale, depreciation and amortization are no longer recorded for any long-lived assets included in the disposal group.

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

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.

Revenue from Contract with Customer [Policy Text Block]

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’ 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. As the Company's intellectual property assets are considered to be located in Germany, the Company records all consolidated revenue in its subsidiary, Pieris Pharmaceuticals, GmbH.

Collaborative Arrangements

The Company considers the nature and contractual terms of an arrangement and assesses 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 recognized under a collaborative arrangement involving a participant that is not a customer is presented as Collaboration Revenue in the Statement of Operations.

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 a portion of 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.

Revenue recognized under an arrangement involving a participant that is a customer is presented as Customer Revenue.

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.

The Company calculates the maximum amount of potential milestones achievable under each collaboration agreement and discloses such potential future milestones for all current collaborations using such a maximum calculation.

Contract Balances

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

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

Costs to Obtain and Fulfill a Contract with a Customer

Certain costs to obtain customer contracts, including success-based fees paid to third-party service providers, and costs to fulfill customer contracts are capitalized in accordance with FASB ASC 340, Other Assets and Deferred Costs, or ASC 340. These costs are amortized to expense on a systemic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. The Company will expense the amortization of costs to obtain customer contracts to general and administrative expense and costs to fulfill customer contracts to research and development expense.

Research and Development Expense, Policy [Policy Text Block]

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 Tax, Policy [Policy Text Block]

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 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.

Share-Based Payment Arrangement [Policy Text Block]

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 service 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 dividends, but may elect pay out dividends to stockholders in the future if we determine that there is sufficient cash and investments to achieve our near and long-term objectives.

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, 2023 and 2022, the Company did not record an income statement benefit for excess tax benefits as a valuation allowance is also required on these amounts.

Government Assistance [Policy Text Block]

Government Grants

The Company recognizes grants from governmental agencies when there is reasonable assurance that the Company will comply with the conditions attached to the grant arrangement and the grant will be received. The Company evaluates the conditions of each grant as of each reporting period to evaluate whether the Company has reached reasonable assurance of meeting the conditions of each grant arrangement and that it is expected that the grant will be received as a result of meeting the necessary conditions. Grants are recognized in the consolidated statements of operations on a systematic basis over the periods in which the Company recognizes the related costs for which the government grant is intended to compensate. Specifically, grant income related to research and development costs is recognized as such expenses are incurred. Grant income is included as a separate caption within Other income (expense), net in the consolidated statements of operations.

Lessee, Leases [Policy Text Block]

Leases

The Company accounts for leases pursuant to ASC 842 Leases (Topic 842), or ASC 842. As a lessee, the Company is required to recognize (i) a lease liability, which is a lessee's 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 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. In addition, the Company does not 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 does 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, including increases to rent based on German Consumer Price Index, or CPI.

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.

When a lease is terminated in its entirety, the corresponding lease liability and right-of-use asset are adjusted to zero. Any difference between the carrying amounts of the right-of-use asset and lease liability as compared to the termination payment is recorded in the statement of operations as a gain or loss.

Commitments and Contingencies, Policy [Policy Text Block]

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, Policy [Policy Text Block]

Segment Reporting

Operating segments are identified as components of an enterprise where separate discrete financial information is evaluated 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, Policy [Policy Text Block]

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.

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Accounting Pronouncements Not Yet Adopted

The Company has considered 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 audited consolidated financial statements as a result of future adoption.

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating activities:
Net loss	$ (24,543)	$ (33,277)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization (accretion)	1,904	2,770
Right-of-use asset (accretion) amortization	(123)	10
Stock-based compensation	3,349	4,402
Asset impairment	13,912	0
Realized investment gains	(53)	(376)
Other non-cash transactions	(124)	(91)
Accounts receivable	5,307	(2,624)
Prepaid expenses and other assets	1,018	(1,358)
Deferred revenue	(39,967)	(20,185)
Account payable	(789)	(4,208)
Accrued expenses and other liabilities	(2,336)	(4,005)
Lease liability, prior to operating lease termination	(868)	(990)
Change in lease liability due to termination of operating lease	(10,506)	0
Net cash used in operating activities	(53,819)	(59,932)
Investing activities:
Purchases of property and equipment	(171)	(1,041)
Proceeds from maturity of investments	35,008	28,200
Purchases of investments	(22,835)	(48,395)
Net cash provided by (used in) investing activities	12,002	(21,236)
Financing activities:
Proceeds from exercise of stock options	0	95
Proceeds from employee stock purchase plan	66	197
Proceeds from issuance of common stock resulting from ATM sales, net of $0.7 million and $0.3 million in transaction costs, respectively	19,729	6,922
Net cash provided by financing activities	19,795	7,214
Effect of exchange rate change on cash and cash equivalents	783	(5,175)
Net decrease in cash and cash equivalents	(21,239)	(79,129)
Cash and cash equivalents at beginning of period	38,635	117,764
Cash and cash equivalents at end of period	17,396	38,635
Supplemental cash flow disclosures:
Net unrealized gain (loss) on investments	74	(73)
Property and equipment included in accounts payable	$ 0	$ 193

Note 7 - Accrued Expenses - Restructuring Activity (Details) - Severance and Benefits Costs [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Restructuring expenses	$ 7,523
Cash payments	(2,418)
Balance at December 31, 2023	$ 5,105

Note 13 - Leases (Details Textual) $ in Millions	12 Months Ended
Note 13 - Leases (Details Textual) $ in Millions	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Feb. 29, 2020 ft²	Aug. 31, 2015 ft²
Operating Lease, Payments	$ 2.2	$ 2.4
Sublease Office Space [Member] \| Boston Massachusetts [Member]
Area of Real Estate Property (Square Foot) \| ft²				3,950
Office and Laboratory Space [Member] \| Hallbergmoos Germany [Member]
Area of Real Estate Property (Square Foot) \| ft²			105,000
Lessee, Operating Lease, Term of Contract (Year)			12 years 6 months
Termination Fee	9.7
Tenant Improvements	$ 11.5

Note 11 - Stock and Employee Benefit Plans - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Granted, balance (in shares)	3,727,942	3,075,282
Executive Officers and Management [Member]
Outstanding, balance (in shares)	300,000
Outstanding, exercise price (in dollars per share)	$ 4.65
Outstanding, balance (in shares)	300,000	300,000
Outstanding, exercise price (in dollars per share)	$ 4.65	$ 4.65
Outstanding, contractual life (Year)	5 years 8 months 1 day
Vested or expected to vest, balance (in shares)	300,000
Vested or expected to vest, exercise price (in dollars per share)	$ 4.65
Vested or expected to vest, contractual life (Year)	5 years 8 months 1 day
Exercisable, balance (in shares)	300,000
Exercisable, exercise price (in dollars per share)	$ 4.65
Exercisable, contractual life (Year)	5 years 8 months 1 day
Exercisable, intrinsic value	$ 0
Employee Director And Consultant Equity Incentive Plan2020 [Member]
Outstanding, balance (in shares)	13,430,366
Outstanding, exercise price (in dollars per share)	$ 3.21
Outstanding, intrinsic value	$ 0
Granted, balance (in shares)	3,727,942
Granted, exercise price (in dollars per share)	$ 1.22
Granted, intrinsic value	$ 0
Canceled, balance (in shares)	2,655,237
Canceled, exercise price (in dollars per share)	$ 2.65
Canceled, intrinsic value	$ 0
Outstanding, balance (in shares)	14,503,071	13,430,366
Outstanding, exercise price (in dollars per share)	$ 2.8	$ 3.21
Outstanding, contractual life (Year)	5 years 10 months 24 days
Outstanding, intrinsic value	$ 0	$ 0
Vested or expected to vest, balance (in shares)	14,503,071
Vested or expected to vest, exercise price (in dollars per share)	$ 2.8
Vested or expected to vest, contractual life (Year)	5 years 10 months 24 days
Vested or expected to vest, intrinsic value	$ 0
Exercisable, balance (in shares)	10,292,063
Exercisable, exercise price (in dollars per share)	$ 3.21
Exercisable, contractual life (Year)	4 years 9 months
Exercisable, intrinsic value	$ 0

Note 2 - Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Significant Accounting Policies [Text Block]

2.	Summary of Significant Accounting Policies

Basis of Presentation and 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, if any (Note 5).

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 furniture and equipment		8-14
Office furniture and equipment		5-13
Computer and equipment		3 - 7

Impairment of Long-lived Assets

Revenue Recognition

Collaborative Arrangements

Revenue from Contracts with Customers

Revenue recognized under an arrangement involving a participant that is a customer is presented as Customer Revenue.

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

Government Grants

Leases

Contingencies

Segment Reporting

Earnings per Share

Recent Accounting Pronouncements Not Yet Adopted

Note 3 - Revenue (Details Textual) $ / shares in Units, $ in Thousands				1 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended
	Apr. 24, 2021 USD ($)	Mar. 24, 2021 USD ($) $ / shares shares	Jan. 01, 2019 USD ($)	Sep. 30, 2023 USD ($)	Jan. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2017	May 19, 2021 USD ($)	Feb. 08, 2018	May 02, 2017 USD ($)
Contract with Customer, Liability, Current									$ 0	$ 20,824
Increase in Contract With Customer Liability									0
Decrease in Contract with Customer, Liability									39,700
Amendment of the Second Seagen Amendment [Member]
Revenue from Contract with Customer, Excluding Assessed Tax				$ 10,100
Genentech [Member]
Number Of Initial Research Programs												2
Contract with Customer, Liability, Revenue Recognized						$ 12,500
Seattle Genetics Inc. [Member]
Amended Collaboration Agreement, Resale of Stock, Period (Day)		60 days
Seattle Genetics Inc. [Member] \| Private Placement [Member]
Contract with Customer, Liability, Total		$ 3,300
Sale of Stock, Number of Shares Issued in Transaction (in shares) \| shares		3,706,174
Sale of Stock, Consideration Received on Transaction		$ 13,000
Sale of Stock, Price Per Share (in dollars per share) \| $ / shares		$ 3.51
Sale of Stock, Fair Value, Price Per Share (in dollars per share) \| $ / shares		$ 2.61
Seattle Genetics Inc. [Member] \| License and Collaboration Agreement [Member]
Number of Research Programs		3											3
Seattle Genetics Inc. [Member] \| Other Arrangement [Member]
Number of Research Programs													2
Seattle Genetics Inc. [Member] \| Collaborative Arrangement [Member]
Revenue from Contract with Customer, Excluding Assessed Tax					$ 5,000	1,500				5,000
Astra Zeneca A B [Member]
Capitalized Contract Cost, Amortization									$ 300
Astra Zeneca A B [Member] \| Accounting Standards Update 2014-09 [Member]
Capitalized Contract Cost, Net, Total														$ 1,600
Capitalized Contract Cost, Gross			$ 1,100
Capitalized Contract Cost, Amortization			$ 300
Astra Zeneca A B [Member] \| License and Collaboration Agreement [Member]
Contract with Customer, Liability, Revenue Recognized								$ 4,000		$ 9,700
Contract with Customer, Liability, Current				$ 3,500				$ 3,500
Astra Zeneca A B [Member] \| License and Collaboration Agreement [Member] \| Maximum [Member]
Number of Collaboration Products														4
Astra Zeneca A B [Member] \| License and Collaboration Agreement [Member] \| Minimum [Member]
Number of Collaboration Products														2
Les Laboratoires Servier And Institut De Recherches Internationales Servier [Member]
Contract with Customer, Liability, Revenue Recognized							$ 4,900
Number of Programs											4
Number of Novel Proteins											1
Les Laboratoires Servier And Institut De Recherches Internationales Servier [Member] \| License and Collaboration Agreement [Member]
Contract with Customer, Liability, Current						$ 4,700
Number of Programs											5
License [Member] \| Genentech [Member]
Contract with Customer, Liability, Total												$ 20,000
License [Member] \| B P Assets X I I Inc [Member] \| Exclusive Product License Agreement [Member]
Contract with Customer, Liability, Total	$ 10,000
Revenue from Contract with Customer, Contribution Towards Manufacturing Activities	$ 4,000

Note 13 - Leases (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Lease, Cost [Table Text Block]

	*Year Ended December 31,*
	*2023*		*2022*
Operating lease costs	$	1,169	$	1,356
Variable lease costs (1)		679		737
Total lease cost	$	1,848	$	2,093

Note 8 - Income Taxes - Schedule of Income Before Income Tax Domestic and Foreign (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Domestic	$ (9,818)	$ (11,765)
Foreign	(14,726)	(21,512)
Loss before income taxes	$ (24,544)	$ (33,277)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
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-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
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-Topic 942
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-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Note 2 - Summary of Significant Accounting Policies - Schedule of Property, Plant and Equipment, Useful Lives (Details)	Dec. 31, 2023
Laboratory Equipment [Member] \| Minimum [Member]
Property and equipment, useful life (Year)	8 years
Laboratory Equipment [Member] \| Maximum [Member]
Property and equipment, useful life (Year)	14 years
Office Equipment [Member] \| Minimum [Member]
Property and equipment, useful life (Year)	5 years
Office Equipment [Member] \| Maximum [Member]
Property and equipment, useful life (Year)	13 years
Computer Equipment [Member] \| Minimum [Member]
Property and equipment, useful life (Year)	3 years
Computer Equipment [Member] \| Maximum [Member]
Property and equipment, useful life (Year)	7 years

Note 8 - Income Taxes

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Income Tax Disclosure [Text Block]

8.	Income Taxes

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

	*Years Ended December 31,*
	*2023*			*2022*
Domestic	$	(9,818	)	$	(11,765	)
Foreign		(14,726	)		(21,512	)
Loss before income taxes	$	(24,544	)	$	(33,277	)

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

	*Years Ended December 31,*
	*2023*		*2022*
Current:
Federal	$	—	$	—
State		—		—
Foreign		—		—
Total current		—		—
Deferred:
Federal		—		—
State		—		—
Foreign		—		—
Total deferred		—		—
Provision for income taxes	$	—	$	—

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

	*2023*			*2022*
Federal income tax rate		21.0	%		21.0	%
Foreign rate differential		0.7	%		5.0	%
State tax, net of federal benefit		3.8	%		2.0	%
Share-based awards compensation		(2.1	)%		(2.2	)%
Permanent items		(2.1	)%		0.3	%
Other		(1.0	)%		1.0	%
Release of uncertain tax position		22.7	%		—	%
Credits		0.8	%		1.2	%
Change in valuation allowance		(43.8	)%		(28.3	)%
Effective income tax rate		—	%		—	%

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,*
	*2023*			*2022*
Deferred tax assets:
Net operating loss carryforwards	$	67,496		$	54,845
Share-based awards compensation		2,624			3,112
Accrued expenses		461			216
R&D Credits		644			413
Depreciation and other		479			384
Unrealized foreign currency		(377	)		359
Capitalized R&D		1,165			952
Lease liability		—			3,541
Total deferred tax assets		72,492			63,822
Deferred tax liabilities:
Right-of-use asset		—			(3,270	)
Accrued expenses		—			—
Total deferred tax liabilities		—			(3,270	)
Less: valuation allowance:		(72,492	)		(60,552	)
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, 2023, 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 $11.9 million for the year ended December 31, 2023 was primarily a result of the operating losses generated in current tax year.

As of December 31, 2023, the Company had net operating loss carryforwards for U.S. federal income tax purposes of $43.4 million and net operating loss carryforwards for state income tax purposes of $46.7 million. Federal tax loss carryforwards that were created prior to December 31, 2017 expire through 2037 and federal losses created after that date do not expire. State loss carryforwards expire starting in 2035. Pursuant to Section 382 of the Internal Revenue Code of 1986, or the Code, and similar state tax law, certain substantial changes in the Company’s ownership may result in a limitation on the amount of net operating loss and tax credit carryforwards that may be used in future years. Utilization of the net operating loss and tax credit carryforwards may be subject to an annual limitation under Section 382 of the Code due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company completed a Section 382 study through December 31, 2020. Based on the study, the Company underwent an ownership change for Section 382 purposes which occurred in February 2018. As a result of the ownership change, the Company’s net operating loss and tax credit carryforwards as of the ownership change dates are subject to limitation under Section 382; however, these limitations are not expected to result in any of the impacted net operating loss and tax credit carryforwards to expire unutilized. Any net operating losses or tax credits generated after the February 2018 change are not subject to this annual limitation. However, subsequent ownership changes, as defined by Section 382, may potentially further limit the amount of net operating loss and tax credit carryforwards that could be utilized to offset future taxable income and tax. 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 2019 through the current year. 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 not under examination by the Internal Revenue Service or any other jurisdictions for any tax years.

As of December 31, 2023, the Company had German corporate income tax and trade tax net operating loss carryforwards of approximately $187.6 million and $183.7 million respectively. Under current German laws, tax loss carryforwards may only be used to offset any relevant later assessment period (calendar year) of $1.2 million plus 60% of the exceeding taxable income and trade profit of such period and do not expire. In addition, certain transactions, including transfers of shares or interest in the loss holding entity, may result in the partial or total forfeiture of tax losses existing at that date. Partial or total forfeiture of tax losses may further occur in corporate reorganizations of the loss holding entity.

As of December 31, 2023, the Company had gross U.S. federal and state research and development and other tax credit carryforwards of $0.5 million and $0.1 million, respectively, which may be available to offset future tax liabilities and begin to expire in 2042 and 2037, respectively. As of December 31, 2022, the Company had gross U.S. federal and state research and development and other tax credit carryforwards of $0.3 million and $0.1 million, respectively, which may be available to offset future tax liabilities and begin to expire in 2042 and 2037, respectively.

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 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, 2023 and December 31, 2022.

On December 22, 2017, the Tax Cuts and Jobs Act, or the TCJA, was signed into law. Under the TCJA provisions, effective with tax years beginning on or after January 1, 2022, taxpayers can no longer immediately expense qualified research and development expenditures. Taxpayers are now required to capitalize and amortize these costs over five years for research conducted within the United States or 15 years for research conducted abroad.

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 year ended December 31, 2023 (in thousands):

Unrecognized tax benefits at December 31, 2022	$	5,363
Decrease as a result of a lapse of the applicable statute of limitations		(5,363	)
Unrecognized tax benefits at December 31, 2023	$	—

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
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-Paragraph 1
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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+ Details

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	At the Market Offering [Member] Preferred Stock [Member]	At the Market Offering [Member] Common Stock [Member]	At the Market Offering [Member] Additional Paid-in Capital [Member]	At the Market Offering [Member] AOCI Attributable to Parent [Member]	At the Market Offering [Member] Retained Earnings [Member]	At the Market Offering [Member]	Private Placement [Member] Preferred Stock [Member]	Private Placement [Member] Common Stock [Member]	Private Placement [Member] Additional Paid-in Capital [Member]	Private Placement [Member] AOCI Attributable to Parent [Member]	Private Placement [Member] Retained Earnings [Member]	Private Placement [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2021													16,000	72,222,000
Balance at Dec. 31, 2021													$ 0	$ 72	$ 306,998	$ 829	$ (257,144)	$ 50,755
Net loss													0	0	0	0	(33,277)	(33,277)
Foreign currency translation adjustment													0	0	0	(1,010)	0	(1,010)
Unrealized loss on investments													0	0	0	(73)	0	(73)
Stock based compensation expense													$ 0	$ 0	4,402	0	0	4,402
Issuance of common stock resulting from exercise of stock options (in shares)													0	46,000
Issuance of common stock resulting from exercise of stock options													$ 0	$ 0	95	0	0	$ 95
Issuance of common stock resulting from purchase of employee stock purchase plan shares (in shares)													0	182,000				181,466
Issuance of common stock resulting from purchase of employee stock purchase plan shares													$ 0	$ 0	197	0	0	$ 197
Issuance of common stock (in shares)	0	2,069,000
Issuance of common stock	$ 0	$ 2	$ 6,838	$ 0	$ 0	$ 6,840
Balance (in shares) at Dec. 31, 2022							16,000	74,519,000
Balance at Dec. 31, 2022							$ 0	$ 74	$ 318,530	$ (254)	$ (290,421)	$ 27,929						27,929
Net loss													0	0	0	0	(24,543)	(24,543)
Foreign currency translation adjustment													0	0	0	208	0	208
Unrealized loss on investments													0	0	0	74	0	74
Stock based compensation expense													$ 0	$ 0	3,349	0	0	$ 3,349
Issuance of common stock resulting from purchase of employee stock purchase plan shares (in shares)													0	155,000				154,656
Issuance of common stock resulting from purchase of employee stock purchase plan shares													$ 0	$ 0	66	0	0	$ 66
Issuance of common stock (in shares)													0	24,261,000
Issuance of common stock													$ 0	$ 24	19,651	0	0	19,675
Balance (in shares) at Dec. 31, 2023													16,000	98,935,000
Balance at Dec. 31, 2023													$ 0	$ 98	$ 341,596	$ 28	$ (314,964)	$ 26,758

Note 13 - Leases - Operating Lease Costs (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Operating lease costs

$ 1,169

$ 1,356

Variable lease costs (1)

^[1]

679

737

Total lease cost

$ 1,848

$ 2,093

[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.

Note 6 - Assets Held for Sale, Property and Equipment - Summary of Assets Held for Sale (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Net Book Value	$ 2,188
Laboratory Furniture and Equipment [Member]
Net Book Value	1,967
Office Furniture and Equipment [Member]
Net Book Value	$ 221

Note 11 - Stock and Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	*Years Ended December 31,*
	*2023*		*2022*
Risk free interest rate		3.33% - 4.11%		1.43% - 3.39%
Expected term (in years)		5.5 - 5.73		5.5 - 5.73
Dividend yield		—		—
Expected volatility		79.5% - 98.6%		79.9% - 81.1%

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

					*Weighted-*
			*Weighted-*		*Average*		*Aggregate*
			*Average*		*Remaining*		*Intrinsic*
	*Number of*		*Exercise*		*Contractual*		*Value*
	*Options*		*Price*		*Life (in years)*		*(in thousands)*
Outstanding, December 31, 2022		13,430,366	$	3.21			$	—
Granted		3,727,942		1.22				—
Canceled/Forfeited		2,655,237		2.65				—
Outstanding, December 31, 2023		14,503,071	$	2.80		5.90	$	—
Vested or expected to vest, December 31, 2023		14,503,071	$	2.80		5.90	$	—
Exercisable, December 31, 2023		10,292,063	$	3.21		4.75	$	—

					*Weighted-*
			*Weighted-*		*Average*		*Aggregate*
			*Average*		*Remaining*		*Intrinsic*
	*Number of*		*Exercise*		*Contractual*		*Value*
	*Options*		*Price*		*Life (in years)*		*(in thousands)*
Outstanding, December 31, 2022		300,000	$	4.65			$	—
Granted		—	$	—			$	—
Canceled/Forfeited		—	$	—			$	—
Outstanding, December 31, 2023		300,000	$	4.65		5.67	$	—
Vested or expected to vest, December 31, 2023		300,000	$	4.65		5.67	$	—
Exercisable, December 31, 2023		300,000	$	4.65		5.67	$	—

Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	*Years Ended December 31,*
	*2023*		*2022*
Research and development	$	1,190	$	1,905
General and administrative		2,159		2,497
Total stock-based compensation	$	3,349	$	4,402

Note 7 - Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Accrued Liabilities [Table Text Block]

	*Years Ended December 31,*
	*2023*		*2022*
Compensation expense	$	6,448	$	3,015
Research and development fees		968		5,758
Accrued accounts payable		558		1,245
Other current liabilities		363		483
Accrued license obligations		213		245
Total	$	8,550	$	10,746

Schedule of Restructuring Reserve by Type of Cost [Table Text Block]

	*Severance and Benefits Costs*
Restructuring expenses	$	7,523
Cash payments	$	(2,418	)
Balance at December 31, 2023	$	5,105

Consolidated Statements of Cash Flows (Parentheticals) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
At the Market Offering [Member] \| Common Stock [Member]
Stock issuance costs	$ 0.7

Note 8 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]

	*Years Ended December 31,*
	*2023*			*2022*
Domestic	$	(9,818	)	$	(11,765	)
Foreign		(14,726	)		(21,512	)
Loss before income taxes	$	(24,544	)	$	(33,277	)

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

	*Years Ended December 31,*
	*2023*		*2022*
Current:
Federal	$	—	$	—
State		—		—
Foreign		—		—
Total current		—		—
Deferred:
Federal		—		—
State		—		—
Foreign		—		—
Total deferred		—		—
Provision for income taxes	$	—	$	—

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	*2023*			*2022*
Federal income tax rate		21.0	%		21.0	%
Foreign rate differential		0.7	%		5.0	%
State tax, net of federal benefit		3.8	%		2.0	%
Share-based awards compensation		(2.1	)%		(2.2	)%
Permanent items		(2.1	)%		0.3	%
Other		(1.0	)%		1.0	%
Release of uncertain tax position		22.7	%		—	%
Credits		0.8	%		1.2	%
Change in valuation allowance		(43.8	)%		(28.3	)%
Effective income tax rate		—	%		—	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

	*Years Ended December 31,*
	*2023*			*2022*
Deferred tax assets:
Net operating loss carryforwards	$	67,496		$	54,845
Share-based awards compensation		2,624			3,112
Accrued expenses		461			216
R&D Credits		644			413
Depreciation and other		479			384
Unrealized foreign currency		(377	)		359
Capitalized R&D		1,165			952
Lease liability		—			3,541
Total deferred tax assets		72,492			63,822
Deferred tax liabilities:
Right-of-use asset		—			(3,270	)
Accrued expenses		—			—
Total deferred tax liabilities		—			(3,270	)
Less: valuation allowance:		(72,492	)		(60,552	)
Net deferred tax asset	$	—		$	—

Summary of Income Tax Contingencies [Table Text Block]

Unrecognized tax benefits at December 31, 2022	$	5,363
Decrease as a result of a lapse of the applicable statute of limitations		(5,363	)
Unrecognized tax benefits at December 31, 2023	$	—

Note 12 - License Agreement

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

License and Transfer Agreement [Text Block]

12.

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 may enter into an amendment reflecting the parties discussions. These discussions may also lead to an increase in the Company's collaborative research activities with TUM.

Note 11 - Stock and Employee Benefit Plans

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

11.

Stock and Employee Benefit Plans

Employee, Director and Consultant Equity Incentive Plans

At the 2020 Annual Shareholder Meeting, held on June 23, 2020, the stockholders approved the 2020 Employee, Director and Consultant Equity Incentive Plan, or the 2020 Plan. The 2020 Plan originally permitted the Company to issue up to 3,500,000 shares of common stock pursuant to awards granted under the 2020 Plan. Upon approval of the 2020 Plan, the 2019 Employee, Director and Consultant Equity Incentive Plan, or the 2019 Plan, was terminated; all unissued options were canceled and no additional awards will be made thereunder. All outstanding awards under the 2019 Plan will remain in effect and any awards forfeited from the outstanding awards will be allocated back into the 2020 Plan. The 2020 Plan, similar to the 2019 Plan, provided for the grant of stock options, restricted and unrestricted stock awards, and other stock-based awards to employees of the Company, non-employee directors of the Company, and certain other consultants performing services for the Company as designated by either the Board of Directors or the compensation committee of the Board of Directors. At the 2021 Annual Meeting of Stockholders, held on June 25, 2021, the Company’s stockholders approved the first amendment to the 2020 Plan to add 2,250,000 shares for issuance under the 2020 Plan, which increased the total permitted for issuance under the 2020 Plan to 5,750,000. At the 2022 Annual Meeting of Stockholders, held on June 22, 2022, the Company’s stockholders approved the second amendment to the 2020 Plan to add an additional 3,000,000 shares for issuance under the 2020 Plan. At the 2023 Annual Meeting of Stockholders held on June 21, 2023, the Company's stockholders approved a third amendment to the 2020 Plan to add 6,000,000 shares of common stock for issuance under the 2020 Plan, which increased the total permitted for issuance under the 2020 Plan to 14,750,000. The 2020 Plan permits the Company to issue up to 14,750,000 shares reserved for issuance pursuant to the 2020 Plan and any additional shares which may be issued if awards outstanding under the Company’s 2014, 2016, 2018 and 2019 Plans are canceled or expire.

The Company’s stock options have a maximum term of 10 years from the date of grant. Stock options granted may be either incentive stock options or nonqualified stock options and the exercise price of stock options must be at least equal to the fair market value of the common stock on the date of grant. The Company’s general policy is to issue shares of common stock 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,*
	*2023*		*2022*
Risk free interest rate		3.33% - 4.11%		1.43% - 3.39%
Expected term (in years)		5.5 - 5.73		5.5 - 5.73
Dividend yield		—		—
Expected volatility		79.5% - 98.6%		79.9% - 81.1%

The weighted-average fair value of the 3,727,942 and 3,075,282 options granted during the years ended December 31, 2023 and 2022 was $0.85 and $1.96, respectively. As of December 31, 2023, there were 9,284,808 shares available for future grant under the 2020 Plan.

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

					*Weighted-*
			*Weighted-*		*Average*		*Aggregate*
			*Average*		*Remaining*		*Intrinsic*
	*Number of*		*Exercise*		*Contractual*		*Value*
	*Options*		*Price*		*Life (in years)*		*(in thousands)*
Outstanding, December 31, 2022		13,430,366	$	3.21			$	—
Granted		3,727,942		1.22				—
Canceled/Forfeited		2,655,237		2.65				—
Outstanding, December 31, 2023		14,503,071	$	2.80		5.90	$	—
Vested or expected to vest, December 31, 2023		14,503,071	$	2.80		5.90	$	—
Exercisable, December 31, 2023		10,292,063	$	3.21		4.75	$	—

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

					*Weighted-*
			*Weighted-*		*Average*		*Aggregate*
			*Average*		*Remaining*		*Intrinsic*
	*Number of*		*Exercise*		*Contractual*		*Value*
	*Options*		*Price*		*Life (in years)*		*(in thousands)*
Outstanding, December 31, 2022		300,000	$	4.65			$	—
Granted		—	$	—			$	—
Canceled/Forfeited		—	$	—			$	—
Outstanding, December 31, 2023		300,000	$	4.65		5.67	$	—
Vested or expected to vest, December 31, 2023		300,000	$	4.65		5.67	$	—
Exercisable, December 31, 2023		300,000	$	4.65		5.67	$	—

Employee Stock Purchase Plans

At the 2023 Annual Meeting of Stockholders, the Company’s stockholders approved the 2023 Employee Stock Purchase Plan, or the 2023 ESPP, which replaces the former 2018 Employee Stock Purchase Plan, or 2018 ESPP. The 2023 ESPP provides eligible employees with the opportunity to purchase shares of the Company's common stock at a discount of 85% of the lower closing market price of the common stock at the beginning date or ending date of each purchase period, on a tax-favored basis, through regular payroll deductions in compliance with federal tax regulations. The Company has reserved 750,000 shares of common stock for issuance under the 2023 ESPP.

Total shares purchased under the 2023 ESPP and 2018 ESPP plan were 154,656 and 181,466 for the years ended December 31, 2023 and 2022, respectively.

Total Stock-based Compensation Expense

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

	*Years Ended December 31,*
	*2023*		*2022*
Research and development	$	1,190	$	1,905
General and administrative		2,159		2,497
Total stock-based compensation	$	3,349	$	4,402

As of December 31, 2023, the total unrecognized compensation cost related to all non-vested awards was $4.3 million. The unrecognized compensation cost would be recognized over a remaining weighted-average period of 2.24 years.

Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2023	Mar. 08, 2024	Jun. 30, 2023
Document Information [Line Items]
Entity Central Index Key	0001583648
Entity Registrant Name	PIERIS PHARMACEUTICALS, INC.
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-37471
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	30-0784346
Entity Address, Address Line One	225 Franklin Street, 26th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02110
City Area Code	857
Local Phone Number	246-8998
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	PIRS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 11,222,444
Entity Common Stock, Shares Outstanding		98,935,025
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Boston, Massachusetts

Note 5 - Cash, Cash Equivalents and Investments - Cash Equivalents and Investments Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value	$ 8,970
Total	22,194	$ 38,152
Fair Value, Inputs, Level 1 [Member]
Total	22,194	22,087
Fair Value, Inputs, Level 2 [Member]
Total	0	16,065
Fair Value, Inputs, Level 3 [Member]
Total	0	0
Money Market Funds [Member]
Money market funds, included in cash equivalents	13,224	17,618
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Money market funds, included in cash equivalents	13,224	17,618
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Money market funds, included in cash equivalents	0	0
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Money market funds, included in cash equivalents	0	0
US Treasury Securities [Member]
Fair Value	8,970	3,573
US Treasury Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value	8,970	3,573
US Treasury Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value	0	0
US Treasury Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value	$ 0	0
Debt Security, Government, Non-US [Member]
Fair Value		896
Debt Security, Government, Non-US [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value		896
Debt Security, Government, Non-US [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value		0
Debt Security, Government, Non-US [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value		0
Asset-Backed Securities [Member]
Fair Value		499
Asset-Backed Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value		0
Asset-Backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value		499
Asset-Backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value		0
Corporate Bond Securities [Member]
Fair Value		15,566
Corporate Bond Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value		0
Corporate Bond Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value		15,566
Corporate Bond Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value		$ 0

Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Preferred Stock, Par Value (in dollars per share)	$ 0.001	$ 0.001
Preferred Stock, Shares Authorized (in shares)	10,000,000	10,000,000
Preferred Stock, Shares Issued (in shares)	15,617	15,617
Preferred Stock, Shares Outstanding (in shares)	15,617	15,617
Common Stock, Par Value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, Shares Authorized (in shares)	300,000,000	300,000,000
Common Stock, Shares Issued (in shares)	98,935,025	74,519,103
Common Stock, Shares Outstanding (in shares)	98,935,025	74,519,103

Note 7 - Accrued Expenses - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Compensation expense	$ 6,448	$ 3,015
Research and development fees	968	5,758
Accrued accounts payable	558	1,245
Other current liabilities	363	483
Accrued license obligations	213	245
Total	$ 8,550	$ 10,746

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue
Customer revenue	$ 38,711	$ 25,469
Collaboration revenue	4,099	433
Total revenue	42,810	25,902
Operating expenses
Research and development	41,801	52,982
General and administrative	16,853	16,394
Asset impairment	13,912	0
Total operating expenses	72,566	69,376
Loss from operations	(29,756)	(43,474)
Other income (expense)
Interest income	1,851	721
Grant income	3,612	8,173
Other (expense) income	(250)	1,303
Net loss	(24,543)	(33,277)
Other comprehensive (loss) income:
Foreign currency translation	208	(1,010)
Unrealized gain (loss) on available-for-sale securities	74	(73)
Comprehensive loss	$ (24,261)	$ (34,360)
Net loss per share
Basic and diluted (in dollars per share)	$ (0.27)	$ (0.45)
Weighted average number of common shares outstanding
Basic and diluted (in shares)	90,064	74,172

Note 8 - Income Tax - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Net operating loss carryforwards	$ 67,496	$ 54,845
Share-based awards compensation, tax assets	2,624	3,112
Accrued expenses, tax assets	461	216
R&D Credits	644	413
Depreciation and other	479	384
Unrealized foreign currency	(377)	(359)
Unrealized foreign currency	377	359
Capitalized R&D	1,165	952
Lease liability	0	3,541
Total deferred tax assets	72,492	63,822
Right-of-use asset	0	(3,270)
Total deferred tax liabilities	0	(3,270)
Less: valuation allowance:	(72,492)	(60,552)
Net deferred tax asset	$ 0	$ 0

Note 3 - Revenue

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Revenue from Contract with Customer [Text Block]

3.	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, 2023 and 2022, respectively, the Company recognized revenue from the following strategic partnerships and other license agreements (in thousands):

	*Year Ended December 31,*
	*2023*		*2022*
AstraZeneca	$	8,399	$	9,117
Pfizer		15,134		8,287
Servier		4,099		5,359
Genentech		12,697		3,139
Boston Pharmaceuticals		2,481		—
Total Revenue	$	42,810	$	25,902

Under the Company´s existing strategic partnerships and other license agreements, the Company could receive the following potential milestone payments (in millions) as of December 31, 2023:

	*Research, Development, Regulatory & Commercial Milestones*		*Sales Milestones*
Pfizer	$	759	$	450
Servier		107		99
Boston Pharmaceuticals		85		265
Total potential milestone payments	$	951	$	814

Strategic Partnerships

Genentech

On May 19, 2021, the Company and Genentech, Inc., or Genentech, entered into a Research Collaboration and License Agreement, or the Genentech Agreement, to discover, develop and commercialize locally delivered respiratory and ophthalmology therapies that leverage the Company’s proprietary Anticalin technology. Upon signing the Genentech Agreement, Genentech paid the Company a $20 million upfront fee. In addition, the Company may be eligible to receive additional milestone payments across multiple programs, as well as tiered royalty payments on net sales at percentages ranging from the mid-single to low double-digits, subject to certain standard reductions and offsets.

Under the terms of the Genentech Agreement, the Company was responsible for discovery and preclinical development of two initial programs. In April and May 2023, Genentech and the Company decided to discontinue the discovery-stage programs in ophthalmology and respiratory, respectively, for scientific reasons. Pursuant to this decision, the material right performance obligations related to the target swaps for these programs also expired. Based on these decisions, there aren't any active performance obligations remaining under the collaboration and the Company recognized all remaining revenue, or $12.5 million, under the collaboration in the second quarter of 2023.

The Genentech Agreement also provided an option to select additional programs, at Genentech's discretion, for a fee and this option expires in May 2024. If Genentech exercises its option to start additional programs, the Company would be eligible to receive additional milestone payments, as well as tiered royalty payments on net sales, subject to certain standard reductions and offsets. Genentech’s options to nominate two additional collaboration targets of their choosing is subject to the legal availability of the target to be researched. As of December 31, 2023, any variable consideration related to the exercise of such options is considered fully constrained.

Boston Pharmaceuticals

On April 24, 2021, the Company and BP Asset XII, Inc., or Boston Pharmaceuticals, a subsidiary of Boston Pharma Holdings, LLC, entered into an Exclusive Product License Agreement, or the BP Agreement, to develop PRS-342, a 4-1BB/GPC3 preclinical immuno-oncology Anticalin-antibody bispecific fusion protein.

Under the terms of the BP Agreement, Boston Pharmaceuticals exclusively licensed worldwide rights to PRS-342. The Company received an upfront payment of $10.0 million and is further entitled to receive development, regulatory and sales-based milestone payments, tiered royalties up to low double-digits on sales of PRS-342 and a percentage of consideration received by Boston Pharmaceuticals in the event of a sublicense of a program licensed under the BP Agreement or a change of control of Boston Pharmaceuticals. The Company also contributed $4.0 million toward manufacturing activities.

The Company completed all performance obligations in 2021, at which point the revenue was recorded from the upfront payment. In August 2023, the first patient was dosed in the Boston Pharmaceuticals sponsored Phase 1/2 study for BOS-342 in hepatocellular carcinoma, or HCC, for which the Company received a milestone payment.

Pfizer

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

Under the terms of the Pfizer Agreements, the companies pursued multiple Anticalin-antibody fusion proteins during the research phase. The Pfizer Agreements provide Pfizer 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. Pfizer will solely develop, fund and commercialize the other two programs. Pfizer 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.

On March 24, 2021, the Company announced that Pfizer made a strategic equity investment in Pieris, and that the companies had entered into a Second Pfizer Amendment (formerly Second Seagen Amendment), in which their existing immuno-oncology collaboration agreement has been amended relating to joint development and commercial rights for one program in the alliance. Under the Second Pfizer Amendment, Pieris’ option to co-develop and co-commercialize one of three programs in the collaboration was converted to a co-promotion option in the United States, with Pfizer solely responsible for the development and overall commercialization of that program. Pieris will also be entitled to increased royalties from that program in the event that it chooses to exercise the co-promotion option. In connection with the agreements described above, the Company and Pfizer entered into a subscription agreement, or the Pfizer Subscription Agreement (formerly the Seagen Subscription Agreement), pursuant to which the Company agreed to issue to Pfizer, and Pfizer agreed to acquire from the Company, 3,706,174 shares of the Company’s common stock for a total purchase price of $13.0 million, or $3.51 per share, in a private placement transaction pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended. The Pfizer Subscription Agreement includes a provision to the effect that Pfizer may ask the Company to file a registration statement to register the resale of the shares issued to Pfizer, at any time beginning on the date that is 60 calendar days from the date of issuance of the shares. The Company assessed the ASC 606 implications of the Pfizer Subscription Agreement and concluded that the fair value of the shares on a per share basis was $2.61 per share as of the transaction date. This resulted in a premium paid for the shares of $3.3 million, all of which was recorded in deferred revenue upon contract execution and allocated to the remaining performance obligations.

F-18

In the second quarter of 2022, the Company recorded approximately $1.5 million in revenue related to completion of the performance obligation for the expiration of the target swap under the second program in the collaboration.

Under the Pfizer 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, with the exception of the $5.0 million milestone as described in the following paragraph.

In January 2023, the Company achieved a milestone for the first program in the collaboration for $5.0 million. The Company evaluated the recognition of the milestone under ASC 606 and concluded that the constraints on the milestone no longer existed as of December 31, 2022 and therefore recorded the full $5.0 million as revenue for the year ended December 31, 2022.

In September 2023, Pfizer and the Company entered into an amendment of the Second Pfizer Amendment that provides Pfizer with collaboration product licenses and no changes to the amounts achievable under the collaboration agreement. The effect of the September 2023 amendment was to transfer responsibility for substantially all activities previously performed by the Company to Pfizer. Subsequently, in December 2023, the transfer of the programs was fully approved by the combined joint steering committee. Accordingly, the Company recognized revenue of approximately $10.1 million for the delivery on its performance obligations related to the two programs for the year ended December 31, 2023. With this amendment, the Company has satisfied all remaining obligations under the collaboration.

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 agreed to advance several novel inhaled Anticalin proteins.

In addition to the Company’s former lead inhaled drug candidate, PRS-060/AZD1402, or the AstraZeneca Lead Product, the Company and AstraZeneca, under the original terms of the AstraZeneca Collaboration Agreement, would 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. As of June 2023, the AstraZeneca Lead Product and three of the four AstraZeneca Collaboration Products had been discontinued. The first two discovery-stage programs were previously discontinued in 2022, which led to approximately $9.7 million in revenue recognized due to these discontinuations. Elarekibep and the third discovery-stage program were discontinued in the second quarter of 2023. The discontinuation of the third discovery program led to recognition of $4.0 million of revenue in the quarter ended June 30, 2023, while there was no revenue recognized as a result of the discontinuation of elarekibep.

The Company was responsible for advancing the AstraZeneca Lead Product through its phase 1 study, with the associated costs funded by AstraZeneca. The parties would 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 had the option to co-develop the AstraZeneca Lead Product and also had a separate option to co-commercialize the AstraZeneca Lead Product in the United States. For the AstraZeneca Collaboration Products, the Company was responsible for the initial discovery of the novel Anticalin proteins, after which AstraZeneca would take the lead on continued development of the AstraZeneca Collaboration Products. The Company had 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 would be responsible for development and commercialization of the other programs worldwide.

On July 17, 2023, AstraZeneca notified the Company of its intention to terminate the AstraZeneca Collaboration Agreement and the AstraZeneca Platform License, effective October 15, 2023. AstraZeneca’s decision to terminate the AstraZeneca Agreements was based on non-clinical safety findings in a 13-week toxicology study of elarekibep in non-human primates previously disclosed by the Company. As a result of this, the remaining amount of current deferred revenue, or $3.5 million, related to the fourth discovery-stage program was recognized in revenue as of September 30, 2023. With the termination of the AstraZeneca Agreements, there are no more active programs or performance obligations related to the collaboration. Following the termination date, the Company determined that it would not continue development of the programs under 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. In accordance with the termination of the AstraZeneca Agreements and recognition of remaining revenue, the Company also amortized the remaining deferred transactions costs to obtain the contract, or $0.3 million. Amortization for the year ended December 31, 2022 was $0.3 million.

Servier

In 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. The intention of the collaboration and defined programs was to 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.

In the first quarter of 2022, the Company satisfied the performance obligation related to the material right for S095025 (PRS-352), which led to point-in-time recognition of revenue for $4.9 million of revenue previously deferred. In the fourth quarter of 2022, Servier discontinued development of S095025 based upon a strategic portfolio review. Since inception, four of the five initially committed programs have been discontinued by Servier. The Company does not presently intend to continue development of the four discontinued programs but retains full rights to advance the development and commercialization of those products on a world-wide basis in the future.

In July 2023, the Company notified Servier of its decision to opt out of co-development and commercialization of S095012 (PRS-344), a 4- 1BB/PD- L1 bispecific Mabcalin protein, in the U.S. Servier retains exclusive, even as to the Company, worldwide rights to the program, including the right to continue to advance development and potential commercialization of S095012 (PRS-344) in the U.S. As a result of the Company's decision to opt out of co-development, the Company will be entitled to increased royalty rates and potential royalties and milestones, if any, for S095012 (PRS-344) under the terms of the Servier Agreement. With the decision to opt out of co-development of S095012 (PRS-344), the Company recognized the remaining revenue under the collaboration, or $4.7 million, in 2023 and there are no more active co-development programs under the collaboration.

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 year ended December 31, 2023 and reductions to deferred revenue were $39.7 million for the year ended December 31, 2023.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
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-URI https://asc.fasb.org//1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-URI https://asc.fasb.org//1943274/2147479806/606-10-50-10

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//606/tableOfContent

+ Details

Note 9 - Stockholders' Equity (Details Textual) $ / shares in Units, $ in Millions								1 Months Ended			12 Months Ended
	Jun. 20, 2023 shares	Jun. 22, 2022 shares	Jun. 25, 2021 shares	May 20, 2021 $ / shares shares	Apr. 01, 2020 shares	Jan. 30, 2019 shares	Jun. 01, 2016 USD ($) shares	Nov. 30, 2022 USD ($)	Aug. 31, 2021 USD ($) $ / shares	Nov. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 $ / shares	Jun. 30, 2016 $ / shares
Common Stock, Shares Authorized (in shares)											300,000,000	300,000,000
Common Stock, Shares, Issued (in shares)											98,935,025	74,519,103
Common Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares											$ 0.001	$ 0.001
Preferred Stock, Shares Authorized (in shares)											10,000,000	10,000,000
Preferred Stock, Shares Issued (in shares)											15,617	15,617
Preferred Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares											$ 0.001	$ 0.001
Preferred Stock, Shares Outstanding, Ending Balance (in shares)											15,617	15,617
Common Stock, Shares, Outstanding (in shares)											98,935,025	74,519,103
Jefferies L L C [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares									$ 0.001
Conversion of Common Stock into Series E Preferred Stock [Member]
Conversion of Stock, Shares Converted (in shares)				5,000,000
Conversion of Stock, Shares Issued (in shares)				5,000
Employee Director And Consultant Equity Incentive Plan2020 [Member]
Sale of Stock, Number of Shares Issued in Transaction (in shares)					3,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)	6,000,000	3,000,000	2,250,000		3,000,000
Securities Purchase Agreement [Member]
Preferred Stock, Shares Issued (in shares)							4,963
Partners' Capital Account, Units, Sold in Private Placement (in shares)							8,188,804
Shares Issued, Price Per Share (in dollars per share) \| $ / shares														$ 2.015
Proceeds from Issuance of Private Placement \| $							$ 16.5
Proceeds From Issuance Of Private Placement Net \| $							$ 15.3
Sale of Stock, Number of Shares Issued in Transaction (in shares)							3,225,804
At the Market Offering [Member] \| Jefferies L L C [Member]
Shares Issued, Price Per Share (in dollars per share) \| $ / shares											$ 0.84
Sale of Stock, Price Per Share (in dollars per share) \| $ / shares													$ 3.46
Sale of Stock, Authorized Amount \| $								$ 75.0	$ 50.0
Stock Issued During Period, Shares, New Issues (in shares)											24,300,000	2,100,000
Stock Issued During Period, Value, Issued for Services \| $											$ 20.3	$ 7.2
Common Stock [Member]
Number Of Votes Per Share											1
Stock Issued During Period, Shares, New Issues (in shares)											24,261,000
Common Stock [Member] \| Stock Exchange Shares from Existing Shareholders [Member]
Sale of Stock, Number of Shares Issued in Transaction (in shares)						5,000,000
Common Stock [Member] \| At the Market Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)												2,069,000
Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)											0
Preferred Stock [Member] \| Preferred Share Exchange [Member]
Sale of Stock, Number of Shares Issued in Transaction (in shares)						5,000
Preferred Stock [Member] \| At the Market Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)												0
Series A Preferred Stock [Member]
Preferred Stock, Shares Issued (in shares)											85	85
Preferred Stock, Shares Outstanding, Ending Balance (in shares)											85	85
Series B Preferred Stock [Member]
Preferred Stock, Shares Issued (in shares)											4,026	4,026
Preferred Stock, Shares Outstanding, Ending Balance (in shares)											4,026	4,026
Series C Preferred Stock [Member]
Preferred Stock, Shares Issued (in shares)											3,506	3,506
Preferred Stock, Shares Outstanding, Ending Balance (in shares)											3,506	3,506
Series C Preferred Stock [Member] \| Preferred Share Exchange [Member]
Sale of Stock, Price Per Share (in dollars per share) \| $ / shares										$ 3.43
Debt Instrument, Convertible, Beneficial Conversion Feature \| $										$ 2.8
Series C Preferred Stock [Member] \| Private Placement [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)										0.001
Proceeds From Issuance Of Private Placement Net \| $										$ 31.0
Sale of Stock, Number of Shares Issued in Transaction (in shares)										9,014,960
Sale of Stock, Price Per Share (in dollars per share) \| $ / shares										$ 3.55
Sale of Stock, Consideration Received Per Transaction \| $										$ 32.0
Stock Issued During Period, Shares, Conversion of Units (in shares)										1
Sale of Stock, Number of Warrants, Per Unit (in shares)										1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)										1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) \| $ / shares										$ 7.1
Convertible Preferred Stock, Weighted Average Stock Price, Percent										3.00%
Series C Preferred Stock [Member] \| Private Placement [Member] \| Maximum [Member]
Warrants and Rights Outstanding, Term (Year)										5 years
Series D Preferred Stock [Member]
Preferred Stock, Shares Issued (in shares)											3,000	3,000
Preferred Stock, Shares Outstanding, Ending Balance (in shares)											3,000	3,000
Series E Preferred Stock [Member]
Preferred Stock, Shares Issued (in shares)											5,000	5,000
Preferred Stock, Shares Outstanding, Ending Balance (in shares)											5,000	5,000
Series A Through E [Member] \| Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares				$ 0.001
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)				1,000
Convertible Preferred Stock, Common Stock Ownership Limit, Percent				9.99%
Convertible Preferred Stock, Beneficial Ownership Limitation, Percent				19.99%
Convertible Preferred Stock, Beneficial Ownership Limitation, Notice Period Before Increase (Year)				61 years

Note 7 - Accrued Expenses

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Accounts Payable and Accrued Liabilities Disclosure [Text Block]

7.	Accrued Expenses

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

	*Years Ended December 31,*
	*2023*		*2022*
Compensation expense	$	6,448	$	3,015
Research and development fees		968		5,758
Accrued accounts payable		558		1,245
Other current liabilities		363		483
Accrued license obligations		213		245
Total	$	8,550	$	10,746

The compensation expense line item in the above table includes both severance and benefit costs associated with the Company's corporate restructuring actions announced in 2023, inclusive of those employees retained as the service period to earn such benefits is considered complete. The Company recognized restructuring expenses consisting of one-time cash severance payments and other employee-related costs. Severance pay and related costs for certain retained employees are estimated to be paid through the end of 2024. The Company recorded these restructuring charges based on each employee’s role to the respective research and development and general and administrative operating expense categories on its consolidated statements of operations and comprehensive loss.

The following table includes a roll forward of the restructuring activity and payments recorded for the year ended December 31, 2023 (in thousands):

	*Severance and Benefits Costs*
Restructuring expenses	$	7,523
Cash payments	$	(2,418	)
Balance at December 31, 2023	$	5,105

Note 11 - Stock and Employee Benefit Plans - Schedule of Employee Service Share-based Compensation Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based payment arrangement expense	$ 3,349	$ 4,402
Research and Development Expense [Member]
Share-based payment arrangement expense	1,190	1,905
General and Administrative Expense [Member]
Share-based payment arrangement expense	$ 2,159	$ 2,497

Note 5 - Cash, Cash Equivalents and Investments (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Cash, Cash Equivalents and Investments [Table Text Block]

	*Total*		*Quoted prices in active markets (Level 1)*		*Significant other observable inputs (Level 2)*		*Significant unobservable inputs (Level 3)*
December 31, 2023
Money market funds, included in cash equivalents	$	13,224	$	13,224	$	—	$	—
Investments - US treasuries		8,970		8,970		—		—
Total	$	22,194	$	22,194	$	—	$	—

	*Total*		*Quoted prices in active markets (Level 1)*		*Significant other observable inputs (Level 2)*		*Significant unobservable inputs (Level 3)*
December 31, 2022
Money market funds, included in cash equivalents	$	17,618	$	17,618	$	—	$	—
Investments - US treasuries		3,573		3,573		—		—
Investments - Foreign treasuries		896		896		—		—
Investments - Asset-backed securities		499		—		499		—
Investments - Corporate bonds		15,566		—		15,566		—
Total	$	38,152	$	22,087	$	16,065	$	—

Debt Securities, Available-for-Sale [Table Text Block]

	*Contractual maturity*
	*(in days)*		*Amortized Cost*		*Unrealized gains*		*Unrealized losses*		*Fair Value*
Investments
US treasuries		4-51	$	8,969	$	1	$	—	$	8,970
Total			$	8,969	$	1	$	—	$	8,970

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Note 4 - Grant Income (Details Textual) - Jun. 30, 2021 € in Millions, $ in Millions	USD ($)	EUR (€)
Grants Receivable	$ 17	€ 14.2

Note 4 - Grant Income

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Government Assistance [Text Block]

4.	Grant Income

One of the Company's proprietary respiratory assets is PRS-220, an oral inhaled Anticalin protein targeting connective tissue growth factor, or CTGF, was being developed as a local treatment for idiopathic pulmonary fibrosis, and other forms for fibrotic lung disorders. In June 2021, the Company received a €14.2 million (approximately $17.0 million) grant from the Bavarian Ministry of Economic Affairs, Regional Development and Energy (the Bavarian Grant) supporting research and development for post-acute sequelae of SARS-CoV-2 infection (PASC) pulmonary fibrosis, or PASC-PF, also known as post-COVID-19 syndrome pulmonary fibrosis, or “long COVID”.

The Bavarian Grant provides partial reimbursement for qualifying research and development activities on PRS-220, including drug manufacturing costs, activities and costs to support an IND filing, and phase 1 clinical trials costs. The Bavarian Grant provides reimbursement of qualifying costs incurred through December 2023, with submission for reimbursements allowed through February 2024, which was successfully completed by the Company. The timing follows the expected development timeline of this program. Qualifying costs incurred may exceed the annual grant funding thresholds.

In addition, the Company is required to communicate if there is a change in control or other event that would impact the continuation of PRS- 220 to the Bavarian project agency, in which case the Company may be required to refund some or all amounts received under the grant.

Note 5 - Cash, Cash Equivalents and Investments

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Cash, Cash Equivalents, and Marketable Securities [Text Block]

5.	Cash, Cash Equivalents and Investments

As of December 31, 2023, cash, cash equivalents and investments comprised funds in depository, money market accounts and U.S. treasury securities. As of December 31, 2022, cash, cash equivalents and investments comprised funds in depository, money market accounts, U.S. and foreign 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, 2023.

	*Total*		*Quoted prices in active markets (Level 1)*		*Significant other observable inputs (Level 2)*		*Significant unobservable inputs (Level 3)*
December 31, 2023
Money market funds, included in cash equivalents	$	13,224	$	13,224	$	—	$	—
Investments - US treasuries		8,970		8,970		—		—
Total	$	22,194	$	22,194	$	—	$	—

	*Total*		*Quoted prices in active markets (Level 1)*		*Significant other observable inputs (Level 2)*		*Significant unobservable inputs (Level 3)*
December 31, 2022
Money market funds, included in cash equivalents	$	17,618	$	17,618	$	—	$	—
Investments - US treasuries		3,573		3,573		—		—
Investments - Foreign treasuries		896		896		—		—
Investments - Asset-backed securities		499		—		499		—
Investments - Corporate bonds		15,566		—		15,566		—
Total	$	38,152	$	22,087	$	16,065	$	—

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, 2023.

Investments at December 31, 2023 consist of the following (in thousands):

	*Contractual maturity*
	*(in days)*		*Amortized Cost*		*Unrealized gains*		*Unrealized losses*		*Fair Value*
Investments
US treasuries		4-51	$	8,969	$	1	$	—	$	8,970
Total			$	8,969	$	1	$	—	$	8,970

The Company recorded realized losses from the maturity of available-for-sale securities of $0.1 million and realized gains of $0.4 million for the years ended December 31, 2023 and 2022, respectively.

As of December 31, 2023, 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.

Note 13 - Leases

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Lessee, Operating Leases [Text Block]

13.

Leases

In August 2015, the Company entered into a sublease to lease approximately 3,950 square feet in Boston, Massachusetts, which expired on December 31, 2022. The Company did not extend the sublease. The Company generally conducts its operational functions in the United States remotely.

In October 2018, Pieris Pharmaceuticals GmbH entered into a lease for office and laboratory space located in Hallbergmoos, Germany, or the Hallbergmoos Lease. Pieris GmbH moved its operations to the Hallbergmoos facility in February 2020. The Hallbergmoos Lease was subsequently amended in May 2019 and February 2020. The Hallbergmoos Lease, as amended, provided an initial rental term of 12.5 years, and a rental area of approximately 105,000 square feet.

In December 2023, Pieris Pharmaceuticals GmbH entered into an agreement to terminate the Hallbermoos Lease, or the Lease Termination Agreement. Under the terms of the Lease Termination Agreement, Pieris Pharmaceuticals GmbH terminated the Hallbergmoos Lease in exchange for a termination fee of approximately €9.7 million, and vacated the majority of the premises by December 31, 2023, while continuing to occupy, through June 2024, a limited portion of the office space and using another portion of the former lab space to house its assets being held for sale.

Cash paid for amounts included in the measurement of the lease liabilities were $2.2 million and $2.4 million for the years ended December 31, 2023 and 2022, respectively, all of which were incurred prior to the lease termination.

The Hallbergmoos Lease included $11.5 million of tenant improvements allowance for normal tenant improvements which was incurred prior to commencing the lease. The Company capitalized the leasehold incentives which were included in Property and equipment, net on the Consolidated Balance Sheet and were amortized on a straight-line basis over the shorter of the useful life or the remaining lease term. The leasehold improvement were subsequently fully impaired in the third quarter of 2023.

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

	*Year Ended December 31,*
	*2023*		*2022*
Operating lease costs	$	1,169	$	1,356
Variable lease costs (1)		679		737
Total lease cost	$	1,848	$	2,093

(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. These costs also included costs associated with increases rent expense based on CPI.

Note 8 - Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Federal income tax rate	21.00%	21.00%
Foreign rate differential	0.70%	5.00%
State tax, net of federal benefit	3.80%	2.00%
Share-based awards compensation, tax rate	(2.10%)	(2.20%)
Permanent items	(2.10%)	0.30%
Other	(1.00%)	1.00%
Release of uncertain tax position	22.70%	0.00%
Credits	0.80%	1.20%
Change in valuation allowance	(43.80%)	(28.30%)
Effective income tax rate	0.00%	0.00%

Note 3 - Revenue (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Disaggregation of Revenue [Table Text Block]

	*Year Ended December 31,*
	*2023*		*2022*
AstraZeneca	$	8,399	$	9,117
Pfizer		15,134		8,287
Servier		4,099		5,359
Genentech		12,697		3,139
Boston Pharmaceuticals		2,481		—
Total Revenue	$	42,810	$	25,902

Revenue From Contract With Customer, Milestone Payments [Table Text Block]

	*Research, Development, Regulatory & Commercial Milestones*		*Sales Milestones*
Pfizer	$	759	$	450
Servier		107		99
Boston Pharmaceuticals		85		265
Total potential milestone payments	$	951	$	814

Note 6 - Assets Held for Sale, Property and Equipment (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Asset Impairment Charges	$ 13,912	$ 0
Long-Lived Assets Held-for-Sale, Net Book Value	2,188
Depreciation	1,800	$ 2,300
Office and Laboratory Space [Member] \| Hallbergmoos Germany [Member]
Operating Lease, Impairment Loss	$ 1,800

Note 3 - Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total revenue	$ 42,810	$ 25,902
Astra Zeneca A B [Member]
Total revenue	8,399	9,117
Pfizer [Member]
Total revenue	15,134	8,287
Les Laboratoires Servier And Institut De Recherches Internationales Servier [Member]
Total revenue	4,099	5,359
Genentech [Member]
Total revenue	12,697	3,139
Boston Pharmaceuticals [Member]
Total revenue	$ 2,481	$ 0

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Note 5 - Cash, Cash Equivalents and Investments (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale, Realized Gain (Loss)	$ (0.1)	$ 0.4

Note 6 - Assets Held for Sale, Property and Equipment

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Assets Held for Sale and Property, Plant and Equipment Disclosure [Text Block]

6.	Assets Held for Sale, Property and Equipment

As of December 31, 2023, assets held for sale are summarized as follows (in thousands):

	*December 31,*
	*2023*
Laboratory furniture and equipment	$	1,967
Office furniture and equipment		221
Assets held for sale	$	2,188

At the end of the third quarter of 2023, as part of the Company's strategic process for maximizing the value of assets, the Company committed to a plan to prepare and sell all property and equipment held at the Hallbergmoos, Germany location. The sale of the assets was deemed probable as a result of management's decision, including the estimated timing of sale which was determined to be within a year of the decision. As a result of this decision, the property and equipment met the criteria for held-for-sale accounting.

The Company recorded impairment charges totaling $13.9 million, of which $1.8 million related to impairment of its right-of-use asset under the Hallbergmoos Lease (see Note 13) with the remaining related to a complete write-off of leasehold improvements and a partial impairment of the Company's other long-lived assets. The remaining $2.2 million in net book value of its long-lived assets represents the Company's best estimate of the fair value less costs to sell that could be recovered related to lab and office equipment and furniture as part of the Company's initiative to monetize all remaining assets. As the estimated selling price less costs to sell are based primarily on unobservable inputs as they relate to the location and condition of the specific lab equipment and furniture, they are classified in Level 3 in the fair value hierarchy. In the first quarter of 2024, the Company conducted an auction, with the assistance of a third party, of its assets held for sale. After the conclusion of the auction, the Company has recovered substantially all of the total net book value of the assets held for sale. The Company has further plans to sell all remaining assets in the second quarter of 2024.

As of December 31, 2022, property and equipment are summarized as follows (in thousands):

	December 31,
	2022
Laboratory furniture and equipment	$	11,970
Office furniture and equipment		1,861
Computer equipment		364
Leasehold improvements		12,444
Property and equipment, cost		26,639
Accumulated depreciation		(9,647	)
Property and equipment, net	$	16,992

Depreciation expense was $1.8 million and $2.3 million for the years ended December 31, 2023 and 2022, respectively. There were no other changes in accumulated depreciation other than the foreign currency impact.