HOOKIPA Pharma (HOOK) 10-K 24 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 14, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-38869
Entity Registrant Name	HOOKIPA PHARMA INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-5395687
Entity Address, Address Line One	350 Fifth Avenue, 72nd Floor, Suite 7240
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10118
Country Region	+43
City Area Code	1
Local Phone Number	890 63 60
Title of 12(b) Security	Common Stock, $0.0001 Par Value per Share
Trading Symbol	HOOK
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	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 237.9
Auditor Name	PwC Wirtschaftsprüfung GmbH
Auditor Firm ID	1259
Auditor Location	Vienna, Austria
Entity Central Index Key	0001760542
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		50,868,668
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,819,732

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 65,921	$ 142,743
Restricted cash	566
Accounts receivable	6,895	5,542
Receivable research incentives	14,271	15,115
Prepaid expenses and other current assets	14,482	8,104
Total current assets	102,135	171,504
Non-current assets:
Restricted cash	425	434
Property, plant and equipment, net	16,352	6,219
Operating lease right of use assets	5,673	6,452
Finance lease right of use assets	90	1,298
Other non-current assets	1,370	1,910
Total non-current assets	23,910	16,313
Total assets	126,045	187,817
Current liabilities
Accounts payable	8,762	8,009
Deferred revenues	5,538	3,750
Operating lease liabilities, current	1,682	1,998
Accrued expenses and other current liabilities	8,880	7,386
Loans payable, current	2,792
Total current liabilities	27,654	21,143
Non-current liabilities
Loans payable, non-current	2,219	4,537
Operating lease liabilities, non-current	3,911	3,819
Deferred revenues, non-current	21	784
Other non-current liabilities	2,648	1,411
Total non-current liabilities	8,799	10,551
Total liabilities	36,453	31,694
Commitments and contingencies (Note 13)
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at December 31, 2021 and December 31, 2020, respectively; Series A convertible preferred stock, 2,978 shares designated, 1,697 shares and 2,978 shares outstanding at December 31, 2021 and December 31, 2020, respectively	0	0
Additional paid-in capital	317,135	309,288
Accumulated other comprehensive loss	(4,780)	(6,067)
Accumulated deficit	(222,766)	(147,101)
Total stockholders' equity	89,592	156,123
Total liabilities and stockholders' equity	126,045	187,817
Common stock
Stockholders' equity:
Common stock	3	3
Class A common stock
Stockholders' equity:
Common stock	$ 0	$ 0

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Series A Convertible Preferred Stock
Preferred stock shares Designated	2,978	2,978
Preferred stock, shares outstanding	1,697	2,978
Common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	27,383,483	25,948,712
Common stock, shares outstanding	27,383,483	25,948,712
Class A common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	3,900,000	3,900,000
Common stock, shares issued	3,819,732	3,819,732
Common stock, shares outstanding	3,819,732	3,819,732

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue from collaboration and licensing	$ 18,448	$ 19,584	$ 11,942
Operating expenses:
Research and development	(82,853)	(54,787)	(46,312)
General and administrative	(17,269)	(18,082)	(16,715)
Total operating expenses	(100,122)	(72,869)	(63,027)
Loss from operations	(81,674)	(53,285)	(51,085)
Other income (expense):
Grant income	9,724	6,517	6,737
Interest income	27	400	1,587
Interest expense	(898)	(786)	(877)
Other income and (expenses), net	(2,843)	3,072	601
Total other income, net	6,010	9,203	8,048
Net loss before tax	(75,664)	(44,082)	(43,037)
Income tax expense	(1)	0	0
Net loss	(75,665)	(44,082)	(43,037)
Other comprehensive loss:
Foreign currency translation gain (loss), net of tax	1,287	(1,414)	(933)
Comprehensive loss	$ (74,378)	$ (45,496)	$ (43,970)
Net loss per share - basic	$ (2.30)	$ (1.69)	$ (2.41)
Net loss per share - diluted	$ (2.30)	$ (1.69)	$ (2.41)

CONSOLIDATED STATEMENTS OF CONV

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Redeemable Convertible Preferred StockSeries D convertible preferred stock	Redeemable Convertible Preferred Stock	Convertible Preferred StockSeries A Convertible Preferred Stock	Convertible Preferred Stock	Common StockCommon stock	Common StockClass A common stock	Additional Paid-In CapitalSeries A Convertible Preferred Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Series A Convertible Preferred Stock	Total
Balance at the beginning of the period at Dec. 31, 2018		$ 104,774
Balance at the beginning of the period (in shares) at Dec. 31, 2018		1,323,506
Increase (Decrease) in Temporary Equity
Issuance of preferred stock, net of issuance costs	$ 37,274
Issuance of preferred stock, net of issuance costs (in shares)	257,000
Conversion of Series A, B, C and D preferred stock into common stock upon initial public offering		$ (142,048)
Conversion of Series A, B, C and D preferred stock into common stock upon initial public offering (in shares)		(1,580,506)
Balance at the beginning of the period at Dec. 31, 2018					$ 0			$ 3,327	$ (3,720)	$ (59,982)		$ (60,375)
Balance at the beginning of the period (in shares) at Dec. 31, 2018					1,006,595
Increase (Decrease) in Stockholders' Equity
Issuance of stock					$ 1			74,614				74,615
Issuance of stock (in shares)					6,000,000
Conversion of preferred stock into common stock					$ 2	$ 0		142,046				142,048
Conversion of preferred stock into common stock (in shares)					14,582,161	3,819,732
Issuance of common stock upon exercise of stock options					$ 0			16				16
Issuance of common stock upon exercise of stock options (in shares)					157,636
Foreign currency translation adjustment, net of tax									(933)			(933)
Stock-based compensation expense								5,565				5,565
Net loss										(43,037)		(43,037)
Balance at the end of the period at Dec. 31, 2019					$ 3	$ 0		225,568	(4,653)	(103,019)		117,899
Balance at the end of the period (in shares) at Dec. 31, 2019					21,746,392	3,819,732
Increase (Decrease) in Stockholders' Equity
Issuance of stock			$ 0		$ 0		$ 32,426	42,574			$ 32,426	42,574
Issuance of stock (in shares)			2,978		3,910,000
Issuance of common stock upon exercise of stock options					$ 0			63				63
Issuance of common stock upon exercise of stock options (in shares)					255,011
Vesting of restricted stock					$ 0			0
Vesting of restricted stock (in shares)					1,060
Foreign currency translation adjustment, net of tax									(1,414)			(1,414)
Vesting of equity grants					$ 0			0
Vesting of equity grants (in shares)					36,249
Stock-based compensation expense								8,657				8,657
Net loss										(44,082)		(44,082)
Balance at the end of the period at Dec. 31, 2020				$ 0	$ 3	$ 0		309,288	(6,067)	(147,101)		156,123
Balance at the end of the period (in shares) at Dec. 31, 2020				2,978	25,948,712	3,819,732
Increase (Decrease) in Stockholders' Equity
Conversion of preferred stock into common stock				$ 0	$ 0			0
Conversion of preferred stock into common stock (in shares)				(1,281)	1,281,000
Issuance of common stock upon exercise of stock options					$ 0			203				$ 203
Issuance of common stock upon exercise of stock options (in shares)					110,071							125,020
Vesting of restricted stock					$ 0			0
Vesting of restricted stock (in shares)					43,700
Foreign currency translation adjustment, net of tax									1,287			$ 1,287
Stock-based compensation expense								7,644				7,644
Net loss										(75,665)		(75,665)
Balance at the end of the period at Dec. 31, 2021				$ 0	$ 3	$ 0		$ 317,135	$ (4,780)	$ (222,766)		$ 89,592
Balance at the end of the period (in shares) at Dec. 31, 2021				1,697	27,383,483	3,819,732

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)$ / shares
Series D convertible preferred stock
Issuance costs	$ 158
Common stock | IPO
Share price (in USD per share) | $ / shares	$ 14
Issuance costs	$ 9,386

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net loss	$ (75,665)	$ (44,082)	$ (43,037)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,644	8,657	5,565
Depreciation and amortization expense	4,640	4,150	3,067
Other non-cash items	1,226	53	52
Changes in operating assets and liabilities:
Accounts receivable	(1,943)	(3,576)	(3,619)
Receivable research incentives	(295)	(5,825)	(5,892)
Prepaid expenses and other current assets	(7,091)	(2,286)	(113)
Other non-current assets	416	(1,080)	869
Accounts payable	858	6,298	4,203
Deferred revenues	1,422	511	(4,442)
Operating lease liabilities	(1,588)	(1,833)	(2,396)
Accrued expenses and other liabilities	4,776	(184)	5,142
Other non-current liabilities	(416)	(142)	(1,130)
Net cash used in operating activities	(66,016)	(39,339)	(41,731)
Investing activities:
Purchases of property and equipment	(12,581)	(2,371)	(1,999)
Net cash used in investing activities	(12,581)	(2,371)	(1,999)
Financing activities:
Payments related to finance leases	(438)	(108)	(1,437)
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs			37,274
Proceeds from issuance of convertible preferred stock, net of issuance costs		32,426
Proceeds from issuance of common stock, net of issuance costs	203	42,637	74,756
Payments for deferred offering costs		(224)
Repayments of borrowings	0	(1,311)	(842)
Net cash (used in) provided by financing activities	(235)	73,420	109,751
Net (decrease) increase in cash, cash equivalents and restricted cash	(78,832)	31,710	66,021
Cash, cash equivalents and restricted cash at beginning of period	143,177	113,575	48,580
Effect of exchange rate changes on cash, cash equivalents and restricted cash	2,567	(2,108)	(1,026)
Cash, cash equivalents and restricted cash at end of period	66,912	143,177	113,575
Supplemental disclosure of cash flow information:
Cash paid for interest	(48)	(97)	(64)
Cash paid for income taxes	(1)	0
Supplemental disclosure of non-cash financing activities:
Conversion of redeemable preferred shares upon the IPO			142,048
Property and equipment additions in accounts payable and accrued expenses	(742)	16	(10)
Lease assets obtained in exchange for new operating lease liabilities	2,727	12
Lease assets derecognized upon lease cancellation	$ 1,061	$ 30	$ 182

Nature of the business and orga

Nature of the business and organization	12 Months Ended
	Dec. 31, 2021
Nature of the business and organization
Nature of the business and organization	1. Nature of the business and organization HOOKIPA Pharma Inc. (“HOOKIPA” or the “Company”) is a clinical stage biopharmaceutical company developing a new class of immunotherapeutics based on its proprietary arenavirus platform that is designed to reprogram the body’s immune system. The Company was incorporated under the name of Hookipa Biotech, Inc. under the laws of the State of Delaware in February 2017 as a fully-owned subsidiary of Hookipa Biotech AG. In June 2018, the Company changed its name from Hookipa Biotech, Inc. to HOOKIPA Pharma Inc. and in order to effectuate the change of the jurisdiction of incorporation, the Company acquired all of the shares of Hookipa Biotech AG, now Hookipa Biotech GmbH. HOOKIPA is headquartered in New York, with European research and preclinical development operations headquartered in Vienna, Austria. In April 2019, the Company closed its initial public offering (“IPO”) and its common stock started trading on the Nasdaq Global Select Market under the ticker symbol “HOOK”. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, the ability to establish clinical- and commercial-scale manufacturing processes and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities and may not ultimately lead to a marketing approval and commercialization of a product. Even if the Company’s drug development efforts are successful, it is uncertain if and when the Company will realize significant revenue from product sales. ​

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2021
Summary of significant accounting policies
Summary of significant accounting policies	2. Summary of significant accounting policies Basis of presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. Going concern Since inception, the Company’s activities have consisted primarily of performing research and development to advance its technologies. The Company is still in the development phase and has not been marketing its technologies to date. Through December 31, 2021, the Company has funded its operations with proceeds from sales of common stock, sales of convertible preferred stock, sales of redeemable convertible preferred stock, collaboration and licensing agreements, grants and borrowings under various agreements with foreign public funding agencies. Since inception, the Company has incurred recurring losses, including net losses of $75.7 million, $44.1 million and $43.0 million for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, the Company had an accumulated deficit of $222.8 million. The Company expects to continue to generate operating losses in the foreseeable future. As of March 24, 2022, the filing date of this Annual Report on Form 10-K, the Company expects that its cash and cash equivalents, together with the net proceeds from the offering in March 2022, and the funds received under the Restated Collaboration Agreement with Gilead, both described below, would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments through at least 12 months from the issuance date of the consolidated financial statements. The Company will seek additional funding in order to reach its development and commercialization objectives. The Company will seek funds through further equity financings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The consolidated financial statements do not reflect any adjustments relating to the recoverability and classification of assets or the amounts and classification of liabilities that might be necessary if the Company is unable to continue as a going concern. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue, income and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the recognition of revenue and income, the accrual of research and development expenses and general and administrative expenses, the present value of lease right of use assets and corresponding liabilities, the valuation of stock-based awards and the valuation of current and non-current loans payable. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. On March 11, 2020, the World Health Organization designated COVID-19 as a global pandemic. The Company believes the extent of the COVID-19 pandemic’s impact on the Company’s business, results of operations and financial condition has been and will continue to be driven by many factors, most of which are beyond the Company’s control and ability to forecast. Because of these uncertainties, the Company cannot estimate how long or to what extent the pandemic will impact its operations. The Company’s accounting estimates and assumptions may change over time in response to COVID-19 and the change could be material in future periods. As of the date of issuance of these consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update estimates, judgments or revise the carrying value of any assets or liabilities. Actual results may differ from those estimates or assumptions. Foreign currency and currency translation The functional currency for the Company is the United States dollar and the functional currency for the Company's wholly owned foreign subsidiary, Hookipa Biotech GmbH, is the euro. Assets and liabilities of Hookipa Biotech GmbH are translated into United States dollars at the exchange rate in effect on the balance sheet date. Income items and expenses are translated at the average exchange rate in effect during the period. Unrealized translation gains and losses are recorded as a cumulative translation adjustment, which is included in the Consolidated Statements of Redeemable Convertible Preferred Stock, Convertible Preferred Stock and Stockholders' Equity (Deficit) as a component of Accumulated other comprehensive loss. Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the local currency are included in other income and expenses, net in the Consolidated Statements of Operations and Comprehensive Loss as incurred. Concentrations of credit risk and of significant suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and short-term bank deposits held with banks in excess of publicly insured limits. For the years ended December 31, 2021 and December 31, 2020 the net proceeds from the Company’s offerings have been deposited in interest-bearing bank accounts with investment grade U.S. financial institutions and have been partially invested in a money market fund. The money market fund, held in U.S. dollars, is primarily invested in U.S. and foreign short-term debt obligations. As of December 31, 2021 and December 31, 2020, the Company’s cash and cash equivalents included smaller amounts of cash balances held in accounts with European banks at the Company’s Austrian subsidiary, partially in euros. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and raw materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services or the availability of raw materials. As of December 31, 2021 and December 31, 2020, respectively, Gilead accounted for the majority of the accounts receivable balance. For the years ended December 31, 2021, December 31, 2020 and December 31, 2019 Gilead accounted for the majority of the Company’s revenues. No other customers accounted for more than 10.0% of accounts receivable or net sales. The Company monitors the financial performance of its customers so that it can appropriately respond to changes in their credit worthiness. To date, the Company has not experienced any significant losses with respect to collection of its accounts receivable. Cash equivalents The Company considers all highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. As of December 31, 2021 and December 31, 2020 cash equivalents consisted of money market funds. Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of an equity financing, these costs are recorded in stockholders’ equity as a reduction of the additional paid-in capital on a pro-rata basis generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. Fair value measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ● Level 1 - Quoted prices in active markets for identical assets or liabilities. ● Level 2 - Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ● Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents are carried at fair value, determined according to the fair value hierarchy described above (see Note 4). Property and equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows: ​ ​ ​ ​ ​ Estimated useful life Leasehold improvements shorter of useful life or term of lease Laboratory equipment 2 - 10 years Furniture and fixtures 2 - 10 years Computer equipment and software 2 - 4 years ​ Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. Expenditures for repairs and maintenance are charged to expense as incurred. When property and equipment is sold or otherwise disposed of, the cost and related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in the consolidated statements of operations. Leases The Company adopted the new leasing standards as of January 1, 2019. For leases with an initial term of 12 months or less, the Company does not recognize a right of use asset or lease liability. These short-term leases are expensed on a straight-line basis over the lease term. The determination whether an arrangement qualifies as a lease is made at contract inception. A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, or (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term. All other leases are recorded as operating leases and are included in right of use (“ROU”) assets and lease liabilities in the consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that the option will be exercised. The Company uses the implicit rate when readily determinable and uses its incremental borrowing rate when the implicit rate is not readily determinable based upon the information available at the commencement date in determining the present value of the lease payments. The incremental borrowing rate is determined using a secured borrowing rate for the same currency and term as the associated lease. The lease payments used to determine ROU assets may include lease incentives, stated rent increases and escalation clauses linked to rates of inflation when determinable and are recognized as ROU asset on the consolidated balance sheet. In addition, certain of the Company’s arrangements contain lease and non-lease components. The Company generally separates lease payments from non-lease payments. Operating leases are reflected in operating lease assets, in current operating lease liabilities and non-current operating lease liabilities in the consolidated balance sheets. Finance leases are reflected in finance lease assets, in accrued expenses and other current liabilities and in other non-current operating lease liabilities in the consolidated balance sheets. The ROU asset is tested for impairment in accordance with Accounting Standards Codification (“ASC”) 360. Capitalized Software Development Cost The Company capitalizes certain implementation costs for internal-use software incurred in a cloud computing agreement that is a service contract. Eligible costs associated with cloud computing arrangements, such as software business applications used in the normal course of business, are capitalized in accordance with ASC 350. These costs are recognized on a straight-line basis in the same line item in the statement of operations and comprehensive loss as the expense for fees for the associated cloud computing arrangement, over the term of the arrangement, plus reasonably certain renewals. Amortization expense of less than $0.1 million associated with the Company's cloud computing arrangements has been recognized during the fiscal year ended December 31, 2021. No amortization expense associated with the Company's cloud computing arrangements has been recognized during the fiscal year ended December 31, 2020 (see Note 5). The Company tests for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Impairment of long-lived assets Long-lived assets, including operating and finance lease right of use assets, consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative technological, scientific or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized in loss from operations when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2021, 2020 and 2019. Segment information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company's singular focus is on developing pharmaceutical products to prevent and cure infectious diseases and cancer. The Chief Executive Officer is the chief operating decision maker, and regularly reviews the consolidated operating results to make decisions about the allocation of the Company's resources. The majority of the Company's tangible assets are held in Austria. Revenue recognition from contracts with customers The Company entered into a collaboration and license agreement (the “Gilead Agreement”) with Gilead whereby the parties agreed to collaborate with respect to two preclinical research programs to evaluate potential vaccine products for the treatment, cure, diagnosis or prevention of the hepatitis B virus (“HBV”) and the human immunodeficiency virus (“HIV”). The Company’s performance obligations under the terms of this agreement include one combined performance obligation for each research program (HBV and HIV) comprised of the transfer of intellectual property rights (licenses) and providing research and development services. The licenses do not represent distinct performance obligations, because they cannot be used without the research and development services. Payments to the Company under this agreement include a non-refundable up-front payment, payments for research and development activities, payments based upon the achievement of defined milestones, and if certain future conditions are met, payments for manufacturing services, commercial milestones and royalties on product sales. The Company evaluates its collaboration and licensing arrangements pursuant to ASC 606 Revenue from Contracts with Customers. To determine the recognition of revenue from arrangements that fall within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. Under ASC 606, the Company applies significant judgement to evaluate whether the obligations under the collaboration and licensing arrangement, represent separate or one or more combined performance obligations, the allocation of the transaction price to identified performance obligations, and the determination of when milestone payments are probable of being received. Upfront payment The non-refundable upfront-payment received by the Company under the Gilead Agreement is recorded as deferred revenue and allocated between the two research program performance obligations. Such amounts are recognized as revenue over the performance period of the respective services on a percent of completion basis using total estimated research and development labor hours (input method) for each of the obligations. The percent of completion basis using labor hours was considered the best measure of progress in which control of the combined performance obligations transfers to the customer, due to the short time intervals in which research results are shared with the collaboration partner and the nature of the work being performed. Reimbursement for services Under the Gilead Agreement, the Company incurs employee expenses as well as external costs for research and manufacturing activities presented as operating expenses or prepaid expenses. Based on the nature of the Company's responsibilities under the collaboration arrangement, reimbursement of those costs are presented as revenue and not deducted from expenses, as the Company controls the research activities. Amounts of consideration allocated to the performance of research or manufacturing services are recognized over the period in which services are performed. Reimbursements for external costs are recognized as revenues in the period in which the goods or services are received and external costs are recognized. Unpaid reimbursement amounts are presented as Accounts receivable. Research and development milestones The Gilead Agreement includes contingent milestone payments related to specified preclinical and clinical development milestones. These milestone payments represent variable consideration that are not initially recognized within the transaction price as they are fully constrained under the guidance in ASC 606, due to the scientific uncertainties and the required commitment from Gilead. The Company will continue to assess the probability of significant reversals for any amounts that become likely to be realized prior to recognizing the variable consideration associated with these payments within the transaction price. Sales-based milestones and royalty payments The Gilead Agreement also includes certain sales-based milestone and royalty payments upon successful commercialization of a licensed product. In accordance with ASC 606-10-55-65 Sales Based or Usage Based Royalties, the Company recognizes revenues from sales-based milestone and royalty payments at the later of (i) the occurrence of the subsequent sale; or (ii) the performance obligation to which some or all of the sales-based milestone or royalty payments has been allocated has been satisfied. The Company anticipates recognizing these milestones and royalty payments if and when subsequent sales are generated from a licensed product by the collaboration partner. Cost to fulfill contracts The Company incurs costs for personnel, supplies and other costs related to its laboratory operations as well as fees from third parties and license expenses in connection with its research and development obligations under the collaboration and licensing agreement. These costs are recognized as research and development expenses over the period in which services are performed. Sublicense fees triggered by the receipt of payments are capitalized as an asset when the obligation to pay the fee arises. The capitalized asset is amortized over the period in which the revenue from the triggering payment is recognized. Research and development costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, laboratory supplies, depreciation, manufacturing expenses and external costs of vendors engaged to conduct preclinical development activities and clinical trials as well as the cost of licensing technology. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed. All patent-related costs incurred in connection with filing and prosecuting patent applications are classified as research and development expenses and expensed as incurred due to the uncertainty about the recovery of the expenditure. Upfront payments, milestone payments and annual payments made for the licensing of technology are generally expensed as research and development in the period in which they are incurred. Incremental sublicense fees triggered by contracts with customers are capitalized and expensed as research and development expenses over the period in which the related revenue is recognized. Research and manufacturing contract costs and accruals The Company has entered into various research and development and manufacturing contracts. Related payments are recorded as the corresponding expenses are incurred. The Company records accruals for estimated ongoing costs and prepaid expenses for advance payments. When evaluating the adequacy of the accrued liabilities and prepaid expenses, the Company analyzes progress of the research studies or clinical trials and manufacturing activities, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company's estimates. The Company's historical accrual estimates have not been materially different from the actual costs. Government grant agreements and research incentives The Company recognizes funding from grants and research incentives received from Austrian government agencies as other income. Income from grants and incentives is recognized in the period during which the related qualifying expenses are incurred, provided that the conditions under which the grants or incentives were provided have been met. For grants under funding agreements and for proceeds under research incentive programs, the Company recognizes grant and incentive income in an amount equal to the estimated qualifying expenses incurred in each period multiplied by the applicable reimbursement percentage. Grant funding that has been received by the Company in advance of incurring qualifying expenses is recorded as deferred income. Grant and incentive income recognized upon incurring qualifying expenses in advance of receipt of grant funding or proceeds from research and development incentives is recorded in the consolidated balance sheets as prepaid expenses and other current assets. The Company has received loans under funding agreements that bear interest at rates that are below market rates of interest. The Company accounts for the imputed benefit arising from the difference between a market rate of interest and the rate of interest charged as additional grant funding, and records interest expense for the loans at a market rate of interest. On the date that loan proceeds are received, the Company recognizes the portion of the loan proceeds allocated to grant funding as a discount to the carrying value of the loan and as other liability, which is subsequently recognized as additional grant income over the term of the funding agreement. Stock-based compensation The Company measures stock-based awards granted to employees and directors based on the fair value on the date of grant using the Black-Scholes option-pricing model for options or the difference between the purchase price per share of the award, if any, and the fair value of the Company's common stock for restricted common stock awards. Compensation expense for those awards is recognized over the requisite service period, which is generally the vesting period of the respective award. The Company uses the graded-vesting method to record the expense of awards with service-based vesting conditions. The Company classifies stock-based compensation expense in its Consolidated Statements of Operations and Comprehensive Loss in the same manner in which the recipient's payroll costs are classified or in which the recipient's service payments are classified. Comprehensive loss Comprehensive loss includes net loss and foreign currency translation adjustments. For the year ended December 31, 2021, comprehensive loss included $1.3 million of foreign currency translation gain adjustments. For the years ended December 31, 2020 and 2019, comprehensive loss included $1.4 million and $0.9 million of foreign currency translation loss adjustments, respectively. Net loss per share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing net loss by the weighted average number of shares outstanding for the period, including potential dilutive shares assuming the dilutive effect of outstanding stock options and of convertible preferred stock. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per share, since dilutive common shares are not assumed to have been issued if their affect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2021, 2020 and 2019. Income taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or in the Company's tax returns. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Changes in deferred tax assets and liabilities are recorded in income tax expense. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that the Company adopts as of the specified effective date. Recently Issued Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance, which requires business entities to provide certain disclosures when they have received government assistance and when they use a grant or contribution accounting model by analogy to other accounting guidance (e.g., a grant model under IAS 20, Accounting for Government Grants and Disclosure of Government Assistance, or ASC 958-605, Not-For-Profit Entities — Revenue Recognition). Topic 832 requires the annual disclosures about transactions with a government that are accounted for by applying a grant or contribution accounting model by analogy of information about the nature of the transactions and the related accounting policy used to account for the transactions, the line items on the balance sheet and income statement that are affected by the transactions, and the amoun

Collaboration and Licensing Agr

Collaboration and Licensing Agreements	12 Months Ended
	Dec. 31, 2021
Collaboration and Licensing Agreements
Collaboration and Licensing Agreements	3. Collaboration and Licensing Agreements Gilead Collaboration and License Agreement In June 2018, the Company entered into the Gilead Agreement whereby the Company and Gilead agreed to collaborate with respect to two preclinical research programs to evaluate potential vaccine products for the treatment, cure, diagnosis or prevention of HBV and HIV. In February 2022, the Company signed an Amended and Restated Collaboration Agreement, which altered key aspects of the collaboration pertaining to the HIV therapeutic (see Note 17). Under the Gilead Agreement, the Company granted Gilead an exclusive, royalty-bearing license to the Company’s technology platforms. Upon entering into the agreement, the Company received a non-refundable $10.0 million upfront payment from Gilead. Gilead is also obligated to make additional payments to the Company upon the achievement of pre-clinical, development and commercial milestones. The development milestones amount to over $300 million. The commercial milestones amount to a total of $115 million. Additionally, Gilead is obligated to pay royalties on net sales for each program. Payments from Gilead generally have a 60 days payment term. The $10.0 million upfront payment and $8.0 million in milestone payments were initially recorded as deferred revenue in the consolidated balance sheet and are recognized as revenue when revenue recognition criteria are met. As of December 31, 2021, $4.3 million of upfront and milestone payments were included as a liability in deferred revenues, current. As of December 31, 2020, $2.5 million of upfront and milestone payments were included as a liability in deferred revenues, current and non-current. As of December 31, 2021, $1.2 million of cost reimbursements for research and development services were included as a liability in deferred revenues. As of December 31, 2020, $2.0 million of cost reimbursements for research and development services were included as a liability in deferred revenues. Reimbursements for external costs are recognized as revenues in the period in which the services are provided and external costs are recognized. In the year ended December 31, 2021, the Company recognized $0.6 million of the upfront payment received in 2018 and $1.5 million of a $4.0 million milestone payment received in 2020. Furthermore, the Company recognized $16.3 million revenue from cost reimbursements for research and development services, of which $2.2 million were initially recorded as deferred revenue in the consolidated balance sheet. No revenue has yet been recognized for another $4.0 million milestone payment that was recorded as deferred revenue in December 2021. For the year ended December 31, 2020, revenue from reimbursement of research and development expenses was $13.0 million, of which $1.1 million were initially recorded as deferred revenue in the consolidated balance sheet. Furthermore, the Company recognized $2.0 million of the upfront payment of $10.0 million received in 2018 and $2.4 million of the $4.0 million milestone payment received in 2020 as revenue. In addition, the Company fully recognized revenue for $2.2 million milestone payments for milestones achieved in the year ended December 31, 2020. For the year ended December 31, 2019, revenue from reimbursement of research and development expenses was $4.3 million, and revenue from partial recognition of the upfront payment of $10.0 million received in 2018 was $4.4 million. Additionally, the Company recognized $3.2 million in milestone payments for milestones achieved in the year ended December 31, 2019. Sublicense fees payable to certain licensors of technologies upon the receipt of the deferred upfront and milestone payments, were capitalized as a contract asset and will be amortized over the period in which the revenue from the triggering payment is recognized. As of December 31, 2021 and December 31, 2020, the contract asset and the liability relating to the sublicense payment was $0.3 million million ​

Fair Value of Financial Assets

Fair Value of Financial Assets	12 Months Ended
	Dec. 31, 2021
Fair Value of Financial Assets
Fair Value of Financial Assets	4. Fair Value of Financial Assets The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicating the level of the fair value hierarchy utilized to determine such fair values (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2021 Using ​ Level 1 Level 2 Level 3 ​ Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 35,403 $ — $ — ​ $ 35,403 Total ​ $ 35,403 $ — $ — ​ $ 35,403 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2020 Using ​ Level 1 Level 2 Level 3 ​ Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 35,397 $ — $ — ​ $ 35,397 Total ​ $ 35,397 $ — $ — ​ $ 35,397 ​ During the year ended December 31, 2021 , there were no transfers between Level 1, Level 2 and Level 3 .

Property, plant and equipment,

Property, plant and equipment, net	12 Months Ended
	Dec. 31, 2021
Property, plant and equipment, net
Property, plant and equipment, net	5. Property, plant and equipment, net Property, plant and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Land ​ $ 2,072 ​ $ — Leasehold improvements ​ ​ 3,348 ​ ​ 3,322 Construction in progress ​ ​ 7,746 ​ ​ 28 Laboratory equipment ​ 7,025 ​ 5,982 Furniture and fixtures ​ 651 ​ 430 Computer equipment and software ​ 1,876 ​ 1,554 Property and equipment, gross ​ 22,718 ​ 11,316 Less: Accumulated depreciation ​ (6,366) ​ (5,097) Property and equipment, net ​ $ 16,352 ​ $ 6,219 ​ Depreciation expense for the years ended December 31, 2021, 2020 and 2019 was $2.1 million, $1.7 million and $1.1 million, respectively. Construction-in-progress as of December 31, 2021 related to investments in connection with the Company’s GMP manufacturing facility project. Construction-in-progress as of December 31, 2020 related to implementation costs for a cloud computing arrangement which is a service contract.

Receivable research incentive

Receivable research incentive	12 Months Ended
	Dec. 31, 2021
Receivable research incentive
Receivable research incentive	6. Receivable research incentive The Company participates in a research incentive program provided by the Austrian government under which it is entitled to reimbursement of a percentage of qualifying research and development expenses and capital expenditures incurred in Austria. Submissions for reimbursement under the program are submitted annually. Incentive amounts are generally paid out during the calendar year that follows the year of the expenses but remain subject to subsequent examinations by the responsible authority. Reimbursements received in excess of the recognized receivable research incentive for a certain period are recorded within other long term liabilities for potential repayment until such time that an audit has taken place, upon expiration of the potential reclaim period, or when it is no longer probable that a reclaim will happen. The years 2018 to present remain open to examination by the authorities. As of December 31, 2021, the Company recognized receivables of $14.3 million from the research incentive program, which are reported in research incentive receivables in the Company’s consolidated balance sheet. As of December 31, 2020, the receivables from the research incentive program were $15.1 million. During the years ended December 31, 2021, 2020 and 2019, the Company recorded $8.9 million, $5.8 million and $5.9 million, respectively, of income related to the incentive program within the Company’s consolidated statements of operations as part of the grant income.

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases
Leases	7. Leases The Company leases real estate, including office and laboratory space and has entered into various other agreements with respect to assets used in conducting its business. The Company’s leases have remaining lease terms ranging from less than 1 year to 4 years. Some of the lease agreements contain rent holidays and rent escalation clauses that were included in the calculation of the right of use assets and lease liabilities. The Company is required to maintain a cash balance of $0.4 million to secure letters of credit associated with real estate leases. This amount was classified as non-current restricted cash in the consolidated balance sheet as of December 31, 2021. Certain of the Company’s leases qualify as operating leases, and certain of its leases qualify as finance leases. The following table summarizes the presentation in the consolidated balance sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ Balance sheet location ​ 2021 ​ 2020 Assets ​ ​ ​ ​ Operating lease assets, net Operating lease right of use assets ​ $ 5,673 ​ $ 6,452 Finance lease assets, net Finance lease right of use assets ​ ​ 90 ​ ​ 1,298 Total lease assets ​ ​ 5,763 ​ ​ 7,750 Liabilities ​ ​ ​ ​ ​ Current operating lease liability Operating lease liabilities, current ​ ​ 1,682 ​ ​ 1,998 Current finance lease liability Accrued expenses and other current liabilities ​ ​ 21 ​ ​ 155 Total current lease liabilities ​ ​ ​ 1,703 ​ ​ 2,153 Non-current operating lease liability Operating lease liabilities, non-current ​ ​ 3,911 ​ ​ 3,819 Non-current finance lease liability Other non-current liabilities ​ ​ — ​ ​ 258 Total non-current lease liabilities ​ ​ 3,911 ​ ​ 4,077 Total lease liabilities ​ $ 5,614 ​ $ 6,230 ​ In the years ended December 31, 2021 and 2020 the Company terminated leases of parking spaces and derecognized the relating right of use asset and the lease liability which were insignificant. ​ The following table summarizes the effect of lease costs in the Company’s consolidated statements of operations and comprehensive loss (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Income statement location December 31, 2021 ​ December 31, 2020 Operating lease expenses Research and development expenses ​ $ 1,910 ​ $ 1,654 ​ General and administrative expenses ​ 203 ​ 376 Finance lease amortization expenses Research and development expenses ​ 425 ​ 395 ​ General and administrative expenses ​ 7 ​ 21 Interest on finance lease liabilities ​ Interest expenses ​ ​ 5 ​ ​ 8 Sublease income Other income (expense) ​ (40) ​ (155) Net lease expense ​ $ 2,510 ​ $ 2,299 ​ The minimum lease payments for the next five years and thereafter are expected to be as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ Operating lease Finance lease Total 2022 ​ 1,585 ​ 21 ​ 1,606 2023 ​ 1,547 ​ — ​ 1,547 2024 ​ 1,340 ​ — ​ 1,340 2025 ​ 1,242 ​ — ​ 1,242 2026 ​ — ​ — ​ — Thereafter ​ — ​ — ​ — Total lease payments ​ ​ 5,714 ​ 21 ​ 5,735 Less: interest ​ ​ 121 ​ 0 ​ 121 Present value of lease liabilities ​ $ 5,593 $ 21 $ 5,614 ​ The weighted average remaining lease term and weighted average discount rate of operating leases are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2021 ​ 2020 ​ Weighted average remaining lease term in years 3.7 ​ ​ 3.1 ​ Weighted average discount rate (1) 1.3 % ​ 2.3 % (1) The weighted average remaining lease term and weighted average discount rate of finance leases are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2021 ​ 2020 ​ Weighted average remaining lease term in years 0.2 ​ ​ 3.0 ​ Weighted average discount rate (1) 0.4 % ​ 1.7 % (1) In December 2021 the Company extended the lease term of existing operating leases for the office and laboratory space in Vienna, Austria. The respective lease liabilities were remeasured and the amounts resulting from the remeasurement of the lease liability were recognized as an adjustment to the corresponding right of use asset. Also in December 2021, the Company reduced the lease term for existing operating and finance leases related to an agreement with a contract manufacturing organization for the production of clinical trial material and accounted for the proportionate decrease in the lease liability and the right of use asset with the difference recognized as a loss of $1.0 million on lease modification in operating research and development expenses on the income statement. Until March 2021, the Company subleased certain of its leased real estate that it did not utilize to a third party. The sublease was qualified as an operating lease. The Company recognized sublease income in its consolidated statements of operations and comprehensive loss. The sublease had no influence on the Company’s accounting for the head lease.

Accrued expenses and other curr

Accrued expenses and other current liabilities	12 Months Ended
	Dec. 31, 2021
Accrued expenses and other current liabilities
Accrued expenses and other current liabilities	8. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2021 2020 Salaries and bonuses ​ 4,754 ​ 4,381 Social security contributions ​ 250 ​ 211 Unearned grant income (current) ​ 693 ​ 878 Sublicense fees ​ ​ 304 ​ ​ — Accrued external research and development expenses ​ ​ 2,165 ​ ​ 895 Accrued external general and administration expenses ​ ​ 629 ​ ​ 634 Accrued for property and equipment acquisitions ​ ​ 7 ​ ​ — Finance lease liabilities ​ ​ 21 ​ ​ 155 Other accruals and liabilities ​ 57 ​ 232 ​ ​ $ 8,880 ​ $ 7,386 ​

Loans payable

Loans payable	12 Months Ended
	Dec. 31, 2021
Loans payable
Loans payable	9. Loans payable As of December 31, 2021 and December 31, 2020, loans payable consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2021 2020 Loans from FFG ​ $ 6,074 ​ $ 6,564 Unamortized debt discount ​ (1,063) ​ (2,027) Total Loans payable, net ​ $ 5,011 ​ $ 4,537 ​ In connection with the funding agreements with the Austrian Research Promotion Agency, ( Österreichische Forschungsförderungsgesellschaft, The FFG Loans bear interest at rates that are below market rates of interest. The Company accounts for the imputed benefit arising from the difference between an estimated market rate of interest and the rate of interest charged by FFG as grant income from FFG. On the date that FFG loan proceeds are received, the Company recognizes the portion of the loan proceeds allocated to grant funding as a discount to the carrying value of the loan and as unearned income, which is recognized as grant income over the term of the funding agreement. The Company recognized grant income of $0.8 million, $0.7 million and $0.8 million during the years ended December 31, 2021, 2020 and 2019, respectively, related to the recognition of the unearned income recorded for the imputed benefit of FFG Loans at below-market interest rates. Unearned income (current) related to the imputed benefit of FFG Loans at below-market interest rates was $0.7 million and $0.9 million as of December 31, 2021 and 2020, respectively, and unearned income (non-current) presented under loans payable non-current related to such benefit was $0.4 million and $1.1 million as of December 31, 2021 and 2020, respectively. In addition, the Company has recorded a discount to the carrying value of each FFG Loan for the portion of the loan proceeds allocated to grant funding, which is being amortized to interest expense over the term of the loan using the effective interest method. As of December 31, 2021 and 2020, the unamortized debt discount related to FFG Loans was $1.1 million and $2.0 million, respectively. The Company recognized interest expense of $0.9 million, $0.8 million and $0.9 million during the years ended December 31, 2021, 2020 and 2019, respectively, related to the FFG Loans, which included interest expense related to the amortization of debt discount of $0.8 million, $0.7 million and $0.8 million during the years ended December 31, 2021, 2020 and 2019, respectively. No principal payment and a principal payment of $1.3 million was made in the years ended December 31, 2021 and 2020, respectively. The Company uses an estimated market rate of 20%, which was determined based on an average of the available interest rates on unsecured loans to comparable companies. A 10% increase or decrease in the estimated market rate of interest would have no material impact on grant income or liabilities. In the event that the underlying program research results in a scientific or technical failure, the principal then outstanding under any loan may be forgiven by FFG on a project-by-project basis. The FFG Loans contain no financial covenants and are not secured by any of the Company's assets. In November 2019, the Company agreed to an earlier repayment schedule for $3.3 million of the outstanding loans with FFG. As a result of the change, the Company reduced the deferred income attributable to the imputed benefit from below market interest by $0.3 million and increased the carrying value of the loans by the same amount. The change had no effect on the income of the year ended December 31, 2019 and the effect on the aggregate future cash flows under the loans is immaterial. As of December 31, 2021, the aggregate minimum future principal payments due in connection with the FFG Loans are summarized as follows (in thousands): ​ ​ ​ ​ Payments Due by Calendar Year Amount 2022 ​ ​ 3,054 2023 ​ ​ 1,821 2024 ​ ​ 1,199 2025 ​ ​ — 2026 ​ ​ — Thereafter ​ ​ — Total ​ $ 6,074 ​

Common stock, Class A common st

Common stock, Class A common stock and convertible preferred stock	12 Months Ended
	Dec. 31, 2021
Common stock, Class A common stock and convertible preferred stock
Common stock, Class A common stock and convertible preferred stock	10. Common stock, Class A common stock and convertible preferred stock The Company’s capital structure consists of common stock, Class A common stock and preferred stock. As of December 31, 2021, the Company was authorized to issue 100,000,000 shares of common stock, 3,900,000 shares of Class A common stock and 10,000,000 shares of preferred stock. The Company has designated 2,978 of the 10,000,000 authorized shares of preferred stock as non-voting Series A convertible preferred stock. As of December 31, 2021, the Company had 27,383,483 shares of common stock Class A common stock issued ​ On April 23, 2019, the Company closed its IPO of 6,000,000 shares of common stock, at an offering price to the public of $14.00 per share. The Company received net proceeds of $74.6 million, after deducting $9.4 million in underwriting discounts and commissions and offering expenses. Upon the closing of the Company’s IPO all then outstanding shares of Preferred Stock converted into 14,582,161 shares of common stock and 3,819,732 shares of Class A common stock. ​ On December 11, 2020, the Company closed a public offering of 3,910,000 shares of its common stock, which included the full exercise of the underwriters’ option to purchase additional shares and of 2,978 shares of Series A convertible preferred stock at a public offering price of $11.75 and $11,750.00 per share, respectively, for net proceeds of $75.0 million after deducting underwriting discounts and commissions and offering expenses. ​ Holders of common stock are entitled to one vote for each share held on all matters submitted to a vote of the stockholders. The holders of Class A common stock and Series A convertible preferred stock are not entitled to vote, except as required by law. The holders of common stock and Class A common stock do not have any cumulative voting rights. Each holder of Class A common stock has the right to convert each share of Class A common stock into one share of common stock at such holder's election. Each holder of Series A convertible preferred stock has the right to convert each share of Series A convertible preferred stock into 1,000 shares of common stock at any time at the holder’s option, provided that the holder will be prohibited, subject to certain exceptions, from converting Series A preferred stock into shares of our 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 our common stock then issued and outstanding. Holders of common stock and Class A common stock are entitled to receive ratably any dividends declared by the board of directors out of funds legally available for that purpose, subject to any preferential dividend rights of any outstanding preferred stock. Holders of Series A preferred stock will be entitled to receive dividends at a rate equal to (on an as-if-converted-to-common stock basis), and in the same form and manner as, dividends actually paid on shares of our common stock. Holders of common stock and Class A common stock have no preemptive rights, conversion rights, or other subscription rights or redemption or sinking fund provisions. In the event of a liquidation, dissolution, or winding up of the Company, holders of our Series A preferred stock will receive a payment equal to $0.001 per share of Series A preferred stock before any proceeds are distributed to the holders of common stock. Then, holders of common stock and Class A common stock will be entitled to share ratably in all assets remaining after payment of all debts and other liabilities. ​ There were 1,697 and 2,978 shares of Series A convertible preferred stock outstanding as of December 31, 2021 and December 31, 2020, respectively. In October 2021 and December 2021 certain of the Company’s stockholders elected to convert an aggregate of 1,281 shares (55 and 1,226 shares, respectively) of Series A convertible preferred stock owned by such holders into an aggregate of 1,281,000 shares of the Company’s common stock.

Stock-based compensation

Stock-based compensation	12 Months Ended
	Dec. 31, 2021
Stock-based compensation
Stock-based compensation	11. Stock-based compensation 2018 Stock Option and Grant Plan In connection with a transaction between entities under common control by which the Company became the reporting entity in June 2018, the Board of Directors approved the 2018 Stock Option and Grant Plan, by which options granted by the previous reporting entity under the 2016 Stock Option Plan and outstanding at the time of the effectiveness of the transaction were replaced at similar commercial terms. In the accompanying consolidated financial statements and notes, options issued under previous stock option plans and respective compensation expenses are retrospectively presented as if such options had been issued and outstanding under the 2018 Stock Option and Grant Plan. The exercise price for options granted as a replacement of the 2016 Stock Option Plan is the U.S. dollar equivalent of €0.09, except for 23,286 options granted to an US employee, for which the exercise price is $2.93 following a repricing of these options in December 2018. For any new options, the exercise price shall not be less than 100% of the fair market value of the common stock on the grant date. Options granted under the 2018 Stock Option and Grant Plan generally vest over four years, with 25% of the options vesting upon the first anniversary of the grant date and the remaining 75% of the options vesting in 12 equal quarterly installments following the first anniversary of the grant date, provided the option holder continues to have an employment or service relationship with the Company on each vesting date. The options expire on the 10 th 2019 Stock Option and Incentive Plan On April 1, 2019, the Company’s stockholders approved the 2019 Stock Option and Incentive Plan, which became effective as of the effective date of the registration statement in connection with the Company’s IPO. The plan provides for the grant of shares of restricted stock, long term incentive awards, stock options or other equity-based awards. The maximum number of shares of the Company’s common stock that may be issued under the Company’s 2019 Stock Option and Incentive Plan is 3,630,686 shares which shall be cumulatively increased each year by up to 4.0% of the then outstanding number of shares. Options granted under the 2019 Stock Option and Incentive Plan generally vest over four years, with 25% of the options vesting upon the first anniversary of the grant date and the remaining 75% of the options vesting in 12 equal quarterly installments following the first anniversary of the grant date, provided the option holder continues to have an employment or service relationship with the Company on each vesting date. Initial options granted to non-executive directors upon their election generally vest over a three-year term with 33% of the options vesting upon the first anniversary of the grant date and the remaining 67% of the options vesting in eight equal quarterly installments following the first anniversary of the grant date. Option re-grants to non-executive directors generally vest on the first anniversary of the grant date. The options expire on the 10 th Stock option valuation The Company estimates the option’s fair value on the date of grant using the Black-Scholes option-pricing model. Black-Scholes utilizes assumptions related to expected term, volatility, the risk-free interest rate, the dividend and employee exercise behavior. Forfeitures are accounted for when they occur. Expected volatilities utilized in the Black-Scholes model are based on historical volatilities of a group of comparable companies. The group of representative companies have characteristics similar to the Company, including the stage of product development and focus on the life science industry. Management believes that this represents the most accurate basis for estimating expected future volatilities under the current conditions. The risk-free interest rate is derived from the yields for U.S. Treasuries with a remaining term approximating the expected life of the options. The expected term represents the period of time that the options granted are expected to be outstanding. The following table summarizes, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model for estimating the fair value of stock options granted during: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended December 31, ​ ​ 2021 2020 2019 ​ ​ ​ ​ ​ ​ ​ ​ Risk-free interest rate 1.07 % 0.44 % 2.21 % Expected term (in years) 6.1 6.1 6.1 Expected volatility 85.5 % 80.2 % 74.2 % Expected dividends — % — % — % ​ For the 2019, 2020 and 2021 grants, the Company used the simplified method in developing an estimate of the expected term due to a lack of historical exercise data. ​ Stock option activity ​ The following table summarizes the Company’s stock option activity since January 1, 2021 (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Number of ​ Exercise ​ Contractual ​ Intrinsic ​ Shares Price Term Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ ​ ​ Outstanding as of December 31, 2020 3,555,945 ​ $ 8.45 7.9 ​ $ 12,839 Granted 990,548 ​ 11.46 ​ ​ ​ Exercised (125,020) ​ 1.93 ​ ​ ​ Forfeited (190,295) ​ 11.50 ​ ​ ​ Outstanding as of December 31, 2021 4,231,178 ​ $ 9.21 7.5 ​ $ 1,640 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable as of December 31, 2021 2,224,349 ​ $ 7.62 6.6 ​ $ 1,624 Options unvested as of December 31, 2021 2,006,829 ​ $ 10.96 8.5 ​ $ 16 ​ The aggregate intrinsic value of stock options was calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The fair value per common stock used for calculating the intrinsic values as of December 31, 2021, December 31, 2020 and December 31, 2019, was $2.33, $11.09 and $12.23, respectively. The aggregate intrinsic value of options exercised during the years ended December 31, 2021, 2020 and 2019 was $1.0 million, $2.9 million and $1.4 million, respectively. The weighted average grant-date fair value per share of stock options granted during the years ended December 31, 2021, 2020 and 2019 was $11.46, $8.95 and $7.92, respectively. The total fair value of stock options vested during the years ended December 31, 2021 and 2020 was $6.0 million and $5.6 million, respectively. Cash received from stock option exercise under share-based payment arrangements for the years ended December 31, 2021, 2020 and 2019 was $203 thousand, $63 thousand and $16 thousand, respectively. Restricted Stock Units In the year ended December 31, 2020, the Company granted restricted stock units with time-based vesting conditions to officers, employees and a consultant to compensate them for a temporary salary or fee reduction in response to the coronavirus pandemic. The restricted stock units are subject to time-based vesting conditions and generally vested in four equal installments between March 2021 and November 2021. The Company measures the fair value of restricted stock units on the date of grant using the grant date market price of the underlying shares. Expenses are recorded using the graded-vesting method. The table below summarizes the Company’s restricted stock unit activity since December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Grant ​ ​ Number of ​ Date Fair ​ Shares Value Outstanding as of December 31, 2020 43,700 ​ $ 11.87 Granted — ​ — Vested (43,700) ​ 11.87 Forfeited — ​ — Outstanding as of December 31, 2021 — ​ $ — ​ The total fair value of restricted stock vested during the year ended December 31, 2021 was $0.5 million. The total fair value of restricted stock vested during the year ended December 31, 2020 was insignificant. The Company had no restricted stock outstanding in the year ended 2019. Common Stock Awards In the year ended December 31, 2020, the Company issued 36,249 unrestricted shares of common stock to the non-executive members of its Board of Directors. The Company’s directors received equity instead of cash as their 2020 board remuneration as part of the Company’s response to the coronavirus pandemic. The total fair value of common stock awards issued during the year ended December 31, 2020 was $0.3 million. The grant date fair value per share of common stock was $9.56 and was measured at the closing price of the common stock on the date of grant. Expenses were recorded immediately and are included in stock based compensation in the year ended December 31, 2020. In the years ended 2021 and 2019, the Company has not issued common stock awards. Stock-based compensation Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Research and development expenses ​ $ 3,200 ​ $ 3,084 ​ $ 1,981 General and administrative expenses ​ 4,444 ​ 5,573 ​ 3,584 ​ ​ $ 7,644 ​ $ 8,657 ​ $ 5,565 ​ As of December 31, 2021 total unrecognized compensation cost related to the unvested stock-based awards was $5.7 million, which is expected to be recognized over a weighted average period of 1.6 years.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2021
Income taxes
Income taxes	12. Income taxes During the years ended December 31, 2021, 2020 and 2019, the Company recorded no income tax benefits for the net operating losses incurred in each year, due to its uncertainty of realizing a benefit from those items. The Company's losses before income taxes were generated in the United States and Austria. For financial reporting purposes, losses before income taxes for the years ended December 31, 2021, 2020 and 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 United States $ (11,403) $ (11,603) $ (7,886) Foreign (Austria) ​ ​ (64,261) ​ ​ (32,479) ​ ​ (35,151) Net loss before tax $ (75,664) $ (44,082) $ (43,037) ​ The Company's worldwide effective tax rate for the years ended December 31, 2021, 2020 and 2019 was 0.0%, 0.0% and 0.0%, respectively. The tax rate is affected by recurring items, such as tax rates in foreign jurisdictions and the relative amounts of income earned in those jurisdictions, which is expected to be fairly consistent in the near term. It is also affected by discrete items that may occur in any given year, but are not consistent from year to year. The following items had the most significant impact on the difference between the statutory U.S. federal income tax rate of 21% for the years ended December 31, 2021, 2020 and 2019 and the effective tax rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2021 2020 2019 ​ U.S. federal statutory income tax rate ​ ​ (21.0) % ​ (21.0) % ​ (21.0) % State income taxes, net of federal benefit ​ ​ — ​ ​ — ​ ​ — ​ Foreign tax rate differential (1) ​ ​ (4.0) ​ ​ (4.0) ​ ​ (4.0) ​ Not taxable government grants (2) ​ ​ (3.8) ​ ​ (4.7) ​ ​ (5.4) ​ Stock-based compensation (3) ​ ​ (1.5) ​ ​ (1.0) ​ ​ (0.3) ​ Other ​ ​ 0.1 ​ ​ 0.5 ​ ​ (0.3) ​ Change in deferred tax asset valuation allowance (4) ​ ​ 30.2 ​ ​ 30.2 ​ ​ 31.0 ​ Effective income tax rate ​ ​ — % ​ — % ​ — % ​ (1) (2) (3) (4) Components of the net deferred tax assets or liabilities as of the years ended December 31, 2021 and 2020 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 55,752 $ 43,563 Credit carryforwards ​ ​ 64 ​ ​ 64 Accrued expenses and other ​ ​ 357 ​ ​ (36) Stock-based compensation ​ ​ 1,209 ​ ​ 2,725 Operating lease liabilities ​ ​ 1,378 ​ ​ 1,513 Finance lease liabilities ​ ​ 5 ​ ​ 103 Total deferred tax assets ​ ​ 58,765 ​ ​ 47,932 Valuation allowance ​ ​ (53,728) ​ ​ (46,064) Total deferred tax assets ​ ​ 5,037 ​ ​ 1,868 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ Accrued expenses and other ​ ​ (3,604) ​ ​ — Fixed assets and intangible assets ​ ​ (11) ​ ​ — Operating lease right of use asset ​ ​ (1,400) ​ ​ (1,614) Finance lease right of use asset ​ ​ (22) ​ ​ (254) Total deferred tax liabilities ​ ​ (5,037) ​ ​ (1,868) ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets ​ $ — $ — ​ As of December 31, 2021, 2020 and 2019, the Company had Austrian net operating loss carryforwards of $219.7 million, $163.2 million and $112.3 million, respectively, and US Federal net operating loss carryforwards of $17.9 million, $8.3 million and $4.9 million, respectively, all of them with no expiry date. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company's history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of its deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2021, 2020 and 2019. Management reevaluates the positive and negative evidence at each reporting period. The amount of the deferred tax asset considered realizable, however, could be adjusted if estimates of future taxable income during the carryforward period are reduced or increased or if objective negative evidence in the form of losses is no longer present and additional weight may be given to subjective evidence. The tax years in which the tax carryforwards were generated may still be adjusted upon examination by the tax authorities. Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2021, 2020 and 2019 related primarily to the increases in net operating loss carryforwards as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Valuation allowance at beginning of period $ (46,064) ​ $ (32,583) ​ $ (19,156) Increases ​ ​ (7,664) ​ ​ (13,481) ​ ​ (13,427) Valuation allowance at end of period $ (53,728) ​ $ (46,064) ​ $ (32,583) ​ On December 22, 2017, the United States enacted the Tax Cuts and Jobs Act (“Tax Reform Legislation” or “TCJA”). The Tax Reform Legislation introduced section 951A, a new tax on so-called “global intangible low-taxed income,” or “GILTI”. GILTI applies to income of a controlled foreign corporation (“CFC”) that is not otherwise subpart F income, and consists of the excess "tested income" over a 10% return on the CFC's “qualified business asset investment,” or “QBAI”. QBAI is the total tax basis of the CFC's depreciable, tangible property used in the production of tested income. The full amount of GILTI is included in taxable income. The GILTI inclusion is then reduced by 50% (reduced to 37.5% after 2025). However, that reduction in GILTI may be limited based on the level of U.S. taxable income. A limited allowance for foreign tax credits is allowed that would reduce the U.S. tax cost. GILTI foreign tax credits can only reduce U.S. taxes owed on GILTI and are not eligible for carryforward. The Company's Austrian subsidiary falls under the category of a CFC and due to the nature of its business model as a technology company, there may not be a material amount of tangible assets if this subsidiary starts to generate profits. GILTI taxation therefore may be applicable. The Company files income tax returns in the U.S. federal jurisdiction as well as in New York. The tax years from 2018 to present remain open to examination by the jurisdictions in which the Company is subject to tax. There are currently no pending income tax examinations in the U.S. ​ The Company evaluates tax positions for recognition using a more likely than not recognition threshold, and those tax positions eligible for recognition are measured as the largest amount of tax benefit that is greater than 50% likely of being realized upon the effective settlement with a taxing authority that has full knowledge of all relevant information. As of December 31, 2021 and 2020, the Company had no unrecognized income tax benefits that would affect the Company’s effective tax rate if recognized.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and contingencies
Commitments and contingencies	13. Commitments and contingencies Contract manufacturing arrangements The Company has entered into arrangements with contract manufacturing organizations (“CMOs”) for manufacturing of materials for research and development purposes, including manufacturing of clinical trial materials. These contracts generally provide for non-cancellable obligations or cancellation penalties depending on the time of cancellation. As of December 31, 2021, the Company’s total non-cancellable obligations under contracts with CMOs, excluding embedded lease liabilities, were $10.5 million, of which $10.4 million relate to 2022 deliverables and $0.1 million relate to 2023 deliverables. In December 2018, the Company entered into an agreement with a contract manufacturing organization for the production of clinical trial material, including seed lots, drug substance for toxicology studies, stability studies and clinical studies as well as related technology transfer, quality control and process optimization activities which commenced in February 2019. Under the financial terms of the agreement the Company is obliged to pay non-cancellable minimum service fees totaling $13.9 million through January 2022. The Company has determined that the agreement includes embedded leases which resulted in recognition of operating and finance lease assets and corresponding liabilities on the Consolidated Balance Sheet. The agreement was not extended beyond the initial term and its wind-down during the first quarter of 2022 has been agreed. Intellectual property licenses The Company has entered into certain license agreements under which it is obligated to make milestone payments upon the achievement of certain development and regulatory milestones, to pay royalties on net sales of licensed products, and to pay a percentage of the sublicense fees which the Company receives from its sublicensees. In the years ended December 31, 2021, 2020 and 2019, the Company recorded $1.3 million, $1.2 million and $1.9 million, respectively, in licensing fees related to intellectual property licenses as research and development expenses. These amounts mainly related to the upfront payment and milestone payments received by the Company under the Gilead Agreement. The amounts recognized as expenses have been agreed to by the licensors but calculation of sublicensing fees on future payments may be subject to interpretation and may change until agreed to by the receiving party. Indemnification agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its Board of Directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2021 or December 31, 2020. Legal proceedings At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company is currently a party to a patent proceeding opposing European Patent No. 3218504, which was granted to the University of Geneva in July 2020 and is exclusively licensed to the Company. While it is not feasible to predict the outcome of these matters with certainty, and some lawsuits, claims or proceedings may be disposed or decided unfavorably, the Company does not expect that the pending patent opposition, and any asserted or un-asserted legal claims or proceedings, individually or in the aggregate, will have a material adverse effect on the Company. However, if, as a result of the current patent proceeding, the Company would lose all, or at least part, of the protection under the opposed patent, such loss could erode the Company’s competitive position and harm its business and ability to achieve profitability. The Company expenses the costs related to the pending and other such legal proceedings as incurred.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2021
401(k) Savings Plan
401(k) Savings Plan	14. 401(k) Savings Plan The Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan provides that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations, on a pretax basis. The Company matches up to 100% of the first 4% of each employee’s contribution. During the years ended December 31, 2021 and December 31, 2020 expenses recognized for the 401(k) Plan were $0.4 million and $0.2 million, respectively. During the year ended December 31, 2019 expenses recognized for the 401(k) Plan were insignificant.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2021
Net loss per share
Net loss per share	15. Net loss per share The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except for per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Numerator: ​ ​ ​ Net loss ​ $ (75,665) ​ $ (44,082) ​ $ (43,037) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding, basic and diluted ​ ​ 29,945,954 ​ ​ 25,876,376 ​ ​ 17,859,935 Weighted-average Series A convertible preferred shares outstanding, basic and diluted, presented as if converted into common stock (1) ​ ​ 2,887,636 ​ ​ 162,732 ​ ​ — Total number of shares used to calculate net loss per share, basic and diluted ​ 32,833,590 ​ 26,039,108 ​ 17,859,935 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share, basic and diluted ​ $ (2.30) ​ $ (1.69) ​ $ (2.41) (1) ​ Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all potential common shares (Common Stock and Class A Common Stock) outstanding would have been anti-dilutive. Potentially dilutive securities (upon exercise) that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Options issued and outstanding 4,231,178 3,555,945 2,999,284 Unvested restricted stock units ​ — ​ 43,700 ​ — Total 4,231,178 3,599,645 2,999,284 ​

Related parties

Related parties	12 Months Ended
	Dec. 31, 2021
Related parties
Related parties	​ 16. Related parties Following the expiry of the consultancy agreement between the Company and its Chief Scientific Officer, Daniel Pinschewer, on March 19, 2020 the Company entered into a new consultancy agreement with Daniel Pinschewer on March 20, 2020, pursuant to which he serves as Scientific Advisor to the Chief Executive Officer. The Company is party to research and service arrangements with the University of Basel. Daniel Pinschewer, formerly Chief Scientific Officer, and his spouse are employees of the University of Basel and both involved in providing the services under these arrangements. Payments to the University of Basel during Daniel Pinschewer’s term as Chief Scientific Officer were reported as related party transactions but payments following the expiry of that role in March 2020 were no longer considered related party transactions. In the year ended December 31, 2021, the Company did not record any related party transactions. In the years ended December 31, 2020 and 2019, the Company recorded $0.3 million and $0.3 million, respectively, in research and development expenses for service fees paid to the University of Basel, which represented related party transactions. The University of Basel is also entitled to receive de minimis royalties on the net sales of any product that is based on a patent created by the Company’s Scientific Advisor to the Chief Executive Officer in the course of his consulting services to the Company. In the years ended December 31, 2021, 2020 and 2019, no royalties were paid pursuant to the terms of this arrangement.

Subsequent events

Subsequent events	12 Months Ended
	Dec. 31, 2021
Subsequent events.
Subsequent events	​ 17. Subsequent events Stock option and equity grant to senior management On February 1, 2022, members of the Company’s executive team received 50% of their 2021 annual bonus in the form of a grant of fully vested stock options, determined based on a value of $3.00 per share and resulting in the issuance of a total number of 145,071 options. The granted options have an exercise price of $1.50 per share, the closing price of the Company’s common stock on January 31, 2022. At the same time, the members of the Company’s executive team agreed to convert a portion of their base salaries, for the six months ending June 30, 2022 for shares of the Company’s fully vested common stock having a value equal to their foregone salary, determined based on a value of $3.00 per share, resulting in the issuance of an aggregate of 112,551 shares of common stock. ​ Amended and restated research collaboration and license agreement ​ In February 2022, the Company and Gilead entered into an amended and restated research collaboration and license agreement. For the future performance of development activities under the amended agreement, the Company received a $4 million milestone payment and a $15.0 million program initiation fee, which have been initially recorded as deferred revenue in the consolidated balance sheet and will be recognized as revenue when revenue recognition criteria are met. ​ In connection with the Restated Collaboration Agreement, the Company entered into a stock purchase agreement with Gilead. Pursuant to, and subject to the terms and conditions of, the stock purchase agreement, Gilead will be required, at the Company’s option, to purchase up to $35,000,000 of the Company’s common stock, par value $0.0001 per share. In February 2022 Gilead purchased an initial amount of 1,666,666 unregistered shares of the Company’s common stock for $5.0 million, corresponding to a purchase price per share of $3.00. ​ Follow-on public offering ​ In March 2022, the Company issued and sold 21,700,000 shares of its common stock, and 15,800 shares of its Series A-1 convertible preferred stock in a follow-on public offering at a public offering price of $2.0 per share of common stock and $2,000 per share of Series A-1 convertible preferred stock, resulting in net proceeds of $70.5 million after underwriting discounts and commission but before other offering expenses. The Company granted the underwriters an option for a period of 30 days to purchase up to 5,625,000 additional shares of its common stock. ​ War between Russia and Ukraine ​ On February 24, 2022, Russian forces began an invasion of the Ukraine. While we have no operations in the Ukraine or Russia and do not perform research, conduct clinical trials, or otherwise do business in these two countries, the geopolitical effects of the war and its potential further escalation, including the effects of other nations’ responses and economic sanctions, are currently unpredictable and may adversely affect our business in the future. ​ ​ ​

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2021
Summary of significant accounting policies
Basis of presentation	Basis of presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation.
Going concern	Going concern Since inception, the Company’s activities have consisted primarily of performing research and development to advance its technologies. The Company is still in the development phase and has not been marketing its technologies to date. Through December 31, 2021, the Company has funded its operations with proceeds from sales of common stock, sales of convertible preferred stock, sales of redeemable convertible preferred stock, collaboration and licensing agreements, grants and borrowings under various agreements with foreign public funding agencies. Since inception, the Company has incurred recurring losses, including net losses of $75.7 million, $44.1 million and $43.0 million for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, the Company had an accumulated deficit of $222.8 million. The Company expects to continue to generate operating losses in the foreseeable future. As of March 24, 2022, the filing date of this Annual Report on Form 10-K, the Company expects that its cash and cash equivalents, together with the net proceeds from the offering in March 2022, and the funds received under the Restated Collaboration Agreement with Gilead, both described below, would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments through at least 12 months from the issuance date of the consolidated financial statements. The Company will seek additional funding in order to reach its development and commercialization objectives. The Company will seek funds through further equity financings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The consolidated financial statements do not reflect any adjustments relating to the recoverability and classification of assets or the amounts and classification of liabilities that might be necessary if the Company is unable to continue as a going concern.
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue, income and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the recognition of revenue and income, the accrual of research and development expenses and general and administrative expenses, the present value of lease right of use assets and corresponding liabilities, the valuation of stock-based awards and the valuation of current and non-current loans payable. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. On March 11, 2020, the World Health Organization designated COVID-19 as a global pandemic. The Company believes the extent of the COVID-19 pandemic’s impact on the Company’s business, results of operations and financial condition has been and will continue to be driven by many factors, most of which are beyond the Company’s control and ability to forecast. Because of these uncertainties, the Company cannot estimate how long or to what extent the pandemic will impact its operations. The Company’s accounting estimates and assumptions may change over time in response to COVID-19 and the change could be material in future periods. As of the date of issuance of these consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update estimates, judgments or revise the carrying value of any assets or liabilities. Actual results may differ from those estimates or assumptions.
Foreign currency and currency translation	Foreign currency and currency translation The functional currency for the Company is the United States dollar and the functional currency for the Company's wholly owned foreign subsidiary, Hookipa Biotech GmbH, is the euro. Assets and liabilities of Hookipa Biotech GmbH are translated into United States dollars at the exchange rate in effect on the balance sheet date. Income items and expenses are translated at the average exchange rate in effect during the period. Unrealized translation gains and losses are recorded as a cumulative translation adjustment, which is included in the Consolidated Statements of Redeemable Convertible Preferred Stock, Convertible Preferred Stock and Stockholders' Equity (Deficit) as a component of Accumulated other comprehensive loss. Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the local currency are included in other income and expenses, net in the Consolidated Statements of Operations and Comprehensive Loss as incurred.
Concentrations of credit risk and of significant suppliers	Concentrations of credit risk and of significant suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and short-term bank deposits held with banks in excess of publicly insured limits. For the years ended December 31, 2021 and December 31, 2020 the net proceeds from the Company’s offerings have been deposited in interest-bearing bank accounts with investment grade U.S. financial institutions and have been partially invested in a money market fund. The money market fund, held in U.S. dollars, is primarily invested in U.S. and foreign short-term debt obligations. As of December 31, 2021 and December 31, 2020, the Company’s cash and cash equivalents included smaller amounts of cash balances held in accounts with European banks at the Company’s Austrian subsidiary, partially in euros. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and raw materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services or the availability of raw materials. As of December 31, 2021 and December 31, 2020, respectively, Gilead accounted for the majority of the accounts receivable balance. For the years ended December 31, 2021, December 31, 2020 and December 31, 2019 Gilead accounted for the majority of the Company’s revenues. No other customers accounted for more than 10.0% of accounts receivable or net sales. The Company monitors the financial performance of its customers so that it can appropriately respond to changes in their credit worthiness. To date, the Company has not experienced any significant losses with respect to collection of its accounts receivable.
Cash equivalents	Cash equivalents The Company considers all highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. As of December 31, 2021 and December 31, 2020 cash equivalents consisted of money market funds.
Deferred offering costs	Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of an equity financing, these costs are recorded in stockholders’ equity as a reduction of the additional paid-in capital on a pro-rata basis generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss.
Fair value measurements	Fair value measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ● Level 1 - Quoted prices in active markets for identical assets or liabilities. ● Level 2 - Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ● Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents are carried at fair value, determined according to the fair value hierarchy described above (see Note 4).
Property and equipment	Property and equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows: ​ ​ ​ ​ ​ Estimated useful life Leasehold improvements shorter of useful life or term of lease Laboratory equipment 2 - 10 years Furniture and fixtures 2 - 10 years Computer equipment and software 2 - 4 years ​ Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. Expenditures for repairs and maintenance are charged to expense as incurred. When property and equipment is sold or otherwise disposed of, the cost and related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in the consolidated statements of operations.
Leases	Leases The Company adopted the new leasing standards as of January 1, 2019. For leases with an initial term of 12 months or less, the Company does not recognize a right of use asset or lease liability. These short-term leases are expensed on a straight-line basis over the lease term. The determination whether an arrangement qualifies as a lease is made at contract inception. A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, or (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term. All other leases are recorded as operating leases and are included in right of use (“ROU”) assets and lease liabilities in the consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that the option will be exercised. The Company uses the implicit rate when readily determinable and uses its incremental borrowing rate when the implicit rate is not readily determinable based upon the information available at the commencement date in determining the present value of the lease payments. The incremental borrowing rate is determined using a secured borrowing rate for the same currency and term as the associated lease. The lease payments used to determine ROU assets may include lease incentives, stated rent increases and escalation clauses linked to rates of inflation when determinable and are recognized as ROU asset on the consolidated balance sheet. In addition, certain of the Company’s arrangements contain lease and non-lease components. The Company generally separates lease payments from non-lease payments. Operating leases are reflected in operating lease assets, in current operating lease liabilities and non-current operating lease liabilities in the consolidated balance sheets. Finance leases are reflected in finance lease assets, in accrued expenses and other current liabilities and in other non-current operating lease liabilities in the consolidated balance sheets. The ROU asset is tested for impairment in accordance with Accounting Standards Codification (“ASC”) 360.
Capitalized Software Development Cost	Capitalized Software Development Cost The Company capitalizes certain implementation costs for internal-use software incurred in a cloud computing agreement that is a service contract. Eligible costs associated with cloud computing arrangements, such as software business applications used in the normal course of business, are capitalized in accordance with ASC 350. These costs are recognized on a straight-line basis in the same line item in the statement of operations and comprehensive loss as the expense for fees for the associated cloud computing arrangement, over the term of the arrangement, plus reasonably certain renewals. Amortization expense of less than $0.1 million associated with the Company's cloud computing arrangements has been recognized during the fiscal year ended December 31, 2021. No amortization expense associated with the Company's cloud computing arrangements has been recognized during the fiscal year ended December 31, 2020 (see Note 5). The Company tests for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable.
Impairment of long-lived assets	Impairment of long-lived assets Long-lived assets, including operating and finance lease right of use assets, consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative technological, scientific or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized in loss from operations when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2021, 2020 and 2019.
Segment information	Segment information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company's singular focus is on developing pharmaceutical products to prevent and cure infectious diseases and cancer. The Chief Executive Officer is the chief operating decision maker, and regularly reviews the consolidated operating results to make decisions about the allocation of the Company's resources. The majority of the Company's tangible assets are held in Austria.
Revenue recognition from contracts with customers	Revenue recognition from contracts with customers The Company entered into a collaboration and license agreement (the “Gilead Agreement”) with Gilead whereby the parties agreed to collaborate with respect to two preclinical research programs to evaluate potential vaccine products for the treatment, cure, diagnosis or prevention of the hepatitis B virus (“HBV”) and the human immunodeficiency virus (“HIV”). The Company’s performance obligations under the terms of this agreement include one combined performance obligation for each research program (HBV and HIV) comprised of the transfer of intellectual property rights (licenses) and providing research and development services. The licenses do not represent distinct performance obligations, because they cannot be used without the research and development services. Payments to the Company under this agreement include a non-refundable up-front payment, payments for research and development activities, payments based upon the achievement of defined milestones, and if certain future conditions are met, payments for manufacturing services, commercial milestones and royalties on product sales. The Company evaluates its collaboration and licensing arrangements pursuant to ASC 606 Revenue from Contracts with Customers. To determine the recognition of revenue from arrangements that fall within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. Under ASC 606, the Company applies significant judgement to evaluate whether the obligations under the collaboration and licensing arrangement, represent separate or one or more combined performance obligations, the allocation of the transaction price to identified performance obligations, and the determination of when milestone payments are probable of being received. Upfront payment The non-refundable upfront-payment received by the Company under the Gilead Agreement is recorded as deferred revenue and allocated between the two research program performance obligations. Such amounts are recognized as revenue over the performance period of the respective services on a percent of completion basis using total estimated research and development labor hours (input method) for each of the obligations. The percent of completion basis using labor hours was considered the best measure of progress in which control of the combined performance obligations transfers to the customer, due to the short time intervals in which research results are shared with the collaboration partner and the nature of the work being performed. Reimbursement for services Under the Gilead Agreement, the Company incurs employee expenses as well as external costs for research and manufacturing activities presented as operating expenses or prepaid expenses. Based on the nature of the Company's responsibilities under the collaboration arrangement, reimbursement of those costs are presented as revenue and not deducted from expenses, as the Company controls the research activities. Amounts of consideration allocated to the performance of research or manufacturing services are recognized over the period in which services are performed. Reimbursements for external costs are recognized as revenues in the period in which the goods or services are received and external costs are recognized. Unpaid reimbursement amounts are presented as Accounts receivable. Research and development milestones The Gilead Agreement includes contingent milestone payments related to specified preclinical and clinical development milestones. These milestone payments represent variable consideration that are not initially recognized within the transaction price as they are fully constrained under the guidance in ASC 606, due to the scientific uncertainties and the required commitment from Gilead. The Company will continue to assess the probability of significant reversals for any amounts that become likely to be realized prior to recognizing the variable consideration associated with these payments within the transaction price. Sales-based milestones and royalty payments The Gilead Agreement also includes certain sales-based milestone and royalty payments upon successful commercialization of a licensed product. In accordance with ASC 606-10-55-65 Sales Based or Usage Based Royalties, the Company recognizes revenues from sales-based milestone and royalty payments at the later of (i) the occurrence of the subsequent sale; or (ii) the performance obligation to which some or all of the sales-based milestone or royalty payments has been allocated has been satisfied. The Company anticipates recognizing these milestones and royalty payments if and when subsequent sales are generated from a licensed product by the collaboration partner. Cost to fulfill contracts The Company incurs costs for personnel, supplies and other costs related to its laboratory operations as well as fees from third parties and license expenses in connection with its research and development obligations under the collaboration and licensing agreement. These costs are recognized as research and development expenses over the period in which services are performed. Sublicense fees triggered by the receipt of payments are capitalized as an asset when the obligation to pay the fee arises. The capitalized asset is amortized over the period in which the revenue from the triggering payment is recognized.
Research and development costs	Research and development costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, laboratory supplies, depreciation, manufacturing expenses and external costs of vendors engaged to conduct preclinical development activities and clinical trials as well as the cost of licensing technology. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed. All patent-related costs incurred in connection with filing and prosecuting patent applications are classified as research and development expenses and expensed as incurred due to the uncertainty about the recovery of the expenditure. Upfront payments, milestone payments and annual payments made for the licensing of technology are generally expensed as research and development in the period in which they are incurred. Incremental sublicense fees triggered by contracts with customers are capitalized and expensed as research and development expenses over the period in which the related revenue is recognized.
Research and manufacturing contract costs and accruals	Research and manufacturing contract costs and accruals The Company has entered into various research and development and manufacturing contracts. Related payments are recorded as the corresponding expenses are incurred. The Company records accruals for estimated ongoing costs and prepaid expenses for advance payments. When evaluating the adequacy of the accrued liabilities and prepaid expenses, the Company analyzes progress of the research studies or clinical trials and manufacturing activities, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company's estimates. The Company's historical accrual estimates have not been materially different from the actual costs.
Government grant agreements and research incentives	Government grant agreements and research incentives The Company recognizes funding from grants and research incentives received from Austrian government agencies as other income. Income from grants and incentives is recognized in the period during which the related qualifying expenses are incurred, provided that the conditions under which the grants or incentives were provided have been met. For grants under funding agreements and for proceeds under research incentive programs, the Company recognizes grant and incentive income in an amount equal to the estimated qualifying expenses incurred in each period multiplied by the applicable reimbursement percentage. Grant funding that has been received by the Company in advance of incurring qualifying expenses is recorded as deferred income. Grant and incentive income recognized upon incurring qualifying expenses in advance of receipt of grant funding or proceeds from research and development incentives is recorded in the consolidated balance sheets as prepaid expenses and other current assets. The Company has received loans under funding agreements that bear interest at rates that are below market rates of interest. The Company accounts for the imputed benefit arising from the difference between a market rate of interest and the rate of interest charged as additional grant funding, and records interest expense for the loans at a market rate of interest. On the date that loan proceeds are received, the Company recognizes the portion of the loan proceeds allocated to grant funding as a discount to the carrying value of the loan and as other liability, which is subsequently recognized as additional grant income over the term of the funding agreement.
Stock-based compensation	Stock-based compensation The Company measures stock-based awards granted to employees and directors based on the fair value on the date of grant using the Black-Scholes option-pricing model for options or the difference between the purchase price per share of the award, if any, and the fair value of the Company's common stock for restricted common stock awards. Compensation expense for those awards is recognized over the requisite service period, which is generally the vesting period of the respective award. The Company uses the graded-vesting method to record the expense of awards with service-based vesting conditions. The Company classifies stock-based compensation expense in its Consolidated Statements of Operations and Comprehensive Loss in the same manner in which the recipient's payroll costs are classified or in which the recipient's service payments are classified.
Comprehensive loss	Comprehensive loss Comprehensive loss includes net loss and foreign currency translation adjustments. For the year ended December 31, 2021, comprehensive loss included $1.3 million of foreign currency translation gain adjustments. For the years ended December 31, 2020 and 2019, comprehensive loss included $1.4 million and $0.9 million of foreign currency translation loss adjustments, respectively.
Net loss per share	Net loss per share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing net loss by the weighted average number of shares outstanding for the period, including potential dilutive shares assuming the dilutive effect of outstanding stock options and of convertible preferred stock. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per share, since dilutive common shares are not assumed to have been issued if their affect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2021, 2020 and 2019.
Income taxes	Income taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or in the Company's tax returns. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Changes in deferred tax assets and liabilities are recorded in income tax expense. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Recent accounting pronouncements	Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that the Company adopts as of the specified effective date. Recently Issued Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance, which requires business entities to provide certain disclosures when they have received government assistance and when they use a grant or contribution accounting model by analogy to other accounting guidance (e.g., a grant model under IAS 20, Accounting for Government Grants and Disclosure of Government Assistance, or ASC 958-605, Not-For-Profit Entities — Revenue Recognition). Topic 832 requires the annual disclosures about transactions with a government that are accounted for by applying a grant or contribution accounting model by analogy of information about the nature of the transactions and the related accounting policy used to account for the transactions, the line items on the balance sheet and income statement that are affected by the transactions, and the amounts applicable to each financial statement line item, significant terms and conditions of the transactions, including commitments and contingencies. The guidance in ASU 2021-10 is effective for all entities for fiscal years beginning after December 15, 2021. Entities may apply the ASU’s provisions either prospectively to all transactions within the scope of ASC 832 that are reflected in the financial statements as of the adoption date and all new transactions entered into after the date of adoption or retrospectively. Early adoption is permitted. The Company analyzed ASU 2021-10 and does not believe the guidance will have a material impact on its consolidated financial statements since the Company has already provided disclosures regarding Government Assistance on its consolidated financial statements. In August 2020, the FASB issued ASU 2020-06, Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40). The ASU provides guidance that simplified the accounting for certain financial instruments with characteristics of liabilities and equity. The new guidance reduced the number of accounting models for convertible debt and convertible preferred stock instruments and made certain disclosure amendments intended to improve the information provided to users. The guidance also amended the derivative guidance for the “own stock” scope exception, which exempts qualifying instruments from being accounted for as derivatives if certain criteria are met. Finally, the standard changed the way certain convertible instruments are treated when calculating earnings per share. This guidance is effective for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years with early adoption permitted. The Company is currently assessing the impact that this guidance will have on its consolidated financial statements.

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2021
Summary of significant accounting policies
Schedule of estimated useful life of each asset	​ ​ ​ ​ ​ Estimated useful life Leasehold improvements shorter of useful life or term of lease Laboratory equipment 2 - 10 years Furniture and fixtures 2 - 10 years Computer equipment and software 2 - 4 years ​

Fair Value of Financial Assets

Fair Value of Financial Assets (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value of Financial Assets
Schedule of financial assets measured at fair value on a recurring basis	The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicating the level of the fair value hierarchy utilized to determine such fair values (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2021 Using ​ Level 1 Level 2 Level 3 ​ Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 35,403 $ — $ — ​ $ 35,403 Total ​ $ 35,403 $ — $ — ​ $ 35,403 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2020 Using ​ Level 1 Level 2 Level 3 ​ Total Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 35,397 $ — $ — ​ $ 35,397 Total ​ $ 35,397 $ — $ — ​ $ 35,397

Property, plant and equipment_2

Property, plant and equipment, net (Tables)	12 Months Ended
	Dec. 31, 2021
Property, plant and equipment, net
Schedule of property, plant and equipment, net	Property, plant and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Land ​ $ 2,072 ​ $ — Leasehold improvements ​ ​ 3,348 ​ ​ 3,322 Construction in progress ​ ​ 7,746 ​ ​ 28 Laboratory equipment ​ 7,025 ​ 5,982 Furniture and fixtures ​ 651 ​ 430 Computer equipment and software ​ 1,876 ​ 1,554 Property and equipment, gross ​ 22,718 ​ 11,316 Less: Accumulated depreciation ​ (6,366) ​ (5,097) Property and equipment, net ​ $ 16,352 ​ $ 6,219

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases
Schedule of operating and finance leases presentation in the consolidated balance sheets	Certain of the Company’s leases qualify as operating leases, and certain of its leases qualify as finance leases. The following table summarizes the presentation in the consolidated balance sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ Balance sheet location ​ 2021 ​ 2020 Assets ​ ​ ​ ​ Operating lease assets, net Operating lease right of use assets ​ $ 5,673 ​ $ 6,452 Finance lease assets, net Finance lease right of use assets ​ ​ 90 ​ ​ 1,298 Total lease assets ​ ​ 5,763 ​ ​ 7,750 Liabilities ​ ​ ​ ​ ​ Current operating lease liability Operating lease liabilities, current ​ ​ 1,682 ​ ​ 1,998 Current finance lease liability Accrued expenses and other current liabilities ​ ​ 21 ​ ​ 155 Total current lease liabilities ​ ​ ​ 1,703 ​ ​ 2,153 Non-current operating lease liability Operating lease liabilities, non-current ​ ​ 3,911 ​ ​ 3,819 Non-current finance lease liability Other non-current liabilities ​ ​ — ​ ​ 258 Total non-current lease liabilities ​ ​ 3,911 ​ ​ 4,077 Total lease liabilities ​ $ 5,614 ​ $ 6,230
Summary of the effect of lease costs	The following table summarizes the effect of lease costs in the Company’s consolidated statements of operations and comprehensive loss (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Income statement location December 31, 2021 ​ December 31, 2020 Operating lease expenses Research and development expenses ​ $ 1,910 ​ $ 1,654 ​ General and administrative expenses ​ 203 ​ 376 Finance lease amortization expenses Research and development expenses ​ 425 ​ 395 ​ General and administrative expenses ​ 7 ​ 21 Interest on finance lease liabilities ​ Interest expenses ​ ​ 5 ​ ​ 8 Sublease income Other income (expense) ​ (40) ​ (155) Net lease expense ​ $ 2,510 ​ $ 2,299
Summary of maturities of operating lease liabilities	The minimum lease payments for the next five years and thereafter are expected to be as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ Operating lease Finance lease Total 2022 ​ 1,585 ​ 21 ​ 1,606 2023 ​ 1,547 ​ — ​ 1,547 2024 ​ 1,340 ​ — ​ 1,340 2025 ​ 1,242 ​ — ​ 1,242 2026 ​ — ​ — ​ — Thereafter ​ — ​ — ​ — Total lease payments ​ ​ 5,714 ​ 21 ​ 5,735 Less: interest ​ ​ 121 ​ 0 ​ 121 Present value of lease liabilities ​ $ 5,593 $ 21 $ 5,614
Summary of maturities of finance lease liabilities	The minimum lease payments for the next five years and thereafter are expected to be as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ Operating lease Finance lease Total 2022 ​ 1,585 ​ 21 ​ 1,606 2023 ​ 1,547 ​ — ​ 1,547 2024 ​ 1,340 ​ — ​ 1,340 2025 ​ 1,242 ​ — ​ 1,242 2026 ​ — ​ — ​ — Thereafter ​ — ​ — ​ — Total lease payments ​ ​ 5,714 ​ 21 ​ 5,735 Less: interest ​ ​ 121 ​ 0 ​ 121 Present value of lease liabilities ​ $ 5,593 $ 21 $ 5,614 ​
Schedule of weighted average remaining lease term and weighted average discount rate of operating leases	The weighted average remaining lease term and weighted average discount rate of operating leases are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2021 ​ 2020 ​ Weighted average remaining lease term in years 3.7 ​ ​ 3.1 ​ Weighted average discount rate (1) 1.3 % ​ 2.3 % (1)
Schedule of weighted average remaining lease term and weighted average discount rate of finance leases	The weighted average remaining lease term and weighted average discount rate of finance leases are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ ​ 2021 ​ 2020 ​ Weighted average remaining lease term in years 0.2 ​ ​ 3.0 ​ Weighted average discount rate (1) 0.4 % ​ 1.7 % (1)

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Accrued expenses and other current liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2021 2020 Salaries and bonuses ​ 4,754 ​ 4,381 Social security contributions ​ 250 ​ 211 Unearned grant income (current) ​ 693 ​ 878 Sublicense fees ​ ​ 304 ​ ​ — Accrued external research and development expenses ​ ​ 2,165 ​ ​ 895 Accrued external general and administration expenses ​ ​ 629 ​ ​ 634 Accrued for property and equipment acquisitions ​ ​ 7 ​ ​ — Finance lease liabilities ​ ​ 21 ​ ​ 155 Other accruals and liabilities ​ 57 ​ 232 ​ ​ $ 8,880 ​ $ 7,386

Loans payable (Tables)

Loans payable (Tables)	12 Months Ended
	Dec. 31, 2021
Loans payable
Schedule of loans payable	As of December 31, 2021 and December 31, 2020, loans payable consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2021 2020 Loans from FFG ​ $ 6,074 ​ $ 6,564 Unamortized debt discount ​ (1,063) ​ (2,027) Total Loans payable, net ​ $ 5,011 ​ $ 4,537
Schedule of aggregate minimum future principal payments due in connection with the FFG Loans	As of December 31, 2021, the aggregate minimum future principal payments due in connection with the FFG Loans are summarized as follows (in thousands): ​ ​ ​ ​ Payments Due by Calendar Year Amount 2022 ​ ​ 3,054 2023 ​ ​ 1,821 2024 ​ ​ 1,199 2025 ​ ​ — 2026 ​ ​ — Thereafter ​ ​ — Total ​ $ 6,074

Stock-based compensation (Table

Stock-based compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Stock-based compensation
Schedule of assumptions used in the Black-Scholes option-pricing model for estimating the fair value of stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended December 31, ​ ​ 2021 2020 2019 ​ ​ ​ ​ ​ ​ ​ ​ Risk-free interest rate 1.07 % 0.44 % 2.21 % Expected term (in years) 6.1 6.1 6.1 Expected volatility 85.5 % 80.2 % 74.2 % Expected dividends — % — % — %
Schedule of summary of stock option activity	The following table summarizes the Company’s stock option activity since January 1, 2021 (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Number of ​ Exercise ​ Contractual ​ Intrinsic ​ Shares Price Term Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ ​ ​ Outstanding as of December 31, 2020 3,555,945 ​ $ 8.45 7.9 ​ $ 12,839 Granted 990,548 ​ 11.46 ​ ​ ​ Exercised (125,020) ​ 1.93 ​ ​ ​ Forfeited (190,295) ​ 11.50 ​ ​ ​ Outstanding as of December 31, 2021 4,231,178 ​ $ 9.21 7.5 ​ $ 1,640 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable as of December 31, 2021 2,224,349 ​ $ 7.62 6.6 ​ $ 1,624 Options unvested as of December 31, 2021 2,006,829 ​ $ 10.96 8.5 ​ $ 16
Schedule of summary of restricted stock unit activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Grant ​ ​ Number of ​ Date Fair ​ Shares Value Outstanding as of December 31, 2020 43,700 ​ $ 11.87 Granted — ​ — Vested (43,700) ​ 11.87 Forfeited — ​ — Outstanding as of December 31, 2021 — ​ $ —
Schedule of stock-based compensation expense	Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Research and development expenses ​ $ 3,200 ​ $ 3,084 ​ $ 1,981 General and administrative expenses ​ 4,444 ​ 5,573 ​ 3,584 ​ ​ $ 7,644 ​ $ 8,657 ​ $ 5,565

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income taxes
Schedule of losses before income taxes	For financial reporting purposes, losses before income taxes for the years ended December 31, 2021, 2020 and 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 United States $ (11,403) $ (11,603) $ (7,886) Foreign (Austria) ​ ​ (64,261) ​ ​ (32,479) ​ ​ (35,151) Net loss before tax $ (75,664) $ (44,082) $ (43,037)
Schedule of effective income tax rate reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2021 2020 2019 ​ U.S. federal statutory income tax rate ​ ​ (21.0) % ​ (21.0) % ​ (21.0) % State income taxes, net of federal benefit ​ ​ — ​ ​ — ​ ​ — ​ Foreign tax rate differential (1) ​ ​ (4.0) ​ ​ (4.0) ​ ​ (4.0) ​ Not taxable government grants (2) ​ ​ (3.8) ​ ​ (4.7) ​ ​ (5.4) ​ Stock-based compensation (3) ​ ​ (1.5) ​ ​ (1.0) ​ ​ (0.3) ​ Other ​ ​ 0.1 ​ ​ 0.5 ​ ​ (0.3) ​ Change in deferred tax asset valuation allowance (4) ​ ​ 30.2 ​ ​ 30.2 ​ ​ 31.0 ​ Effective income tax rate ​ ​ — % ​ — % ​ — % ​ (1) (2) (3) (4)
Components of the net deferred tax assets or liabilities	Components of the net deferred tax assets or liabilities as of the years ended December 31, 2021 and 2020 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 Deferred tax assets: ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 55,752 $ 43,563 Credit carryforwards ​ ​ 64 ​ ​ 64 Accrued expenses and other ​ ​ 357 ​ ​ (36) Stock-based compensation ​ ​ 1,209 ​ ​ 2,725 Operating lease liabilities ​ ​ 1,378 ​ ​ 1,513 Finance lease liabilities ​ ​ 5 ​ ​ 103 Total deferred tax assets ​ ​ 58,765 ​ ​ 47,932 Valuation allowance ​ ​ (53,728) ​ ​ (46,064) Total deferred tax assets ​ ​ 5,037 ​ ​ 1,868 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ Accrued expenses and other ​ ​ (3,604) ​ ​ — Fixed assets and intangible assets ​ ​ (11) ​ ​ — Operating lease right of use asset ​ ​ (1,400) ​ ​ (1,614) Finance lease right of use asset ​ ​ (22) ​ ​ (254) Total deferred tax liabilities ​ ​ (5,037) ​ ​ (1,868) ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets ​ $ — $ —
Changes in the valuation allowance for deferred tax assets	Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2021, 2020 and 2019 related primarily to the increases in net operating loss carryforwards as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Valuation allowance at beginning of period $ (46,064) ​ $ (32,583) ​ $ (19,156) Increases ​ ​ (7,664) ​ ​ (13,481) ​ ​ (13,427) Valuation allowance at end of period $ (53,728) ​ $ (46,064) ​ $ (32,583)

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2021
Net loss per share
Schedule of basic and diluted net loss per share	The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except for per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Numerator: ​ ​ ​ Net loss ​ $ (75,665) ​ $ (44,082) ​ $ (43,037) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding, basic and diluted ​ ​ 29,945,954 ​ ​ 25,876,376 ​ ​ 17,859,935 Weighted-average Series A convertible preferred shares outstanding, basic and diluted, presented as if converted into common stock (1) ​ ​ 2,887,636 ​ ​ 162,732 ​ ​ — Total number of shares used to calculate net loss per share, basic and diluted ​ 32,833,590 ​ 26,039,108 ​ 17,859,935 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share, basic and diluted ​ $ (2.30) ​ $ (1.69) ​ $ (2.41) (1)
Schedule of potentially dilutive securities that were not included in the diluted per share calculations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2021 2020 2019 Options issued and outstanding 4,231,178 3,555,945 2,999,284 Unvested restricted stock units ​ — ​ 43,700 ​ — Total 4,231,178 3,599,645 2,999,284

Summary of significant accoun_4

Summary of significant accounting policies - Going concern (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary of significant accounting policies
Net losses	$ 75,665	$ 44,082	$ 43,037
Accumulated deficit	$ 222,766	$ 147,101

Summary of significant accoun_5

Summary of significant accounting policies - Property and equipment (Details)	12 Months Ended
	Dec. 31, 2021
Laboratory equipment | Minimum
Property and equipment
Estimated useful life (in years)	2 years
Laboratory equipment | Maximum
Property and equipment
Estimated useful life (in years)	10 years
Furniture and fixtures | Minimum
Property and equipment
Estimated useful life (in years)	2 years
Furniture and fixtures | Maximum
Property and equipment
Estimated useful life (in years)	10 years
Computer equipment and software | Minimum
Property and equipment
Estimated useful life (in years)	2 years
Computer equipment and software | Maximum
Property and equipment
Estimated useful life (in years)	4 years

Summary of significant accoun_6

Summary of significant accounting policies - Others (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)itemProgram	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Summary of significant accounting policies
Amortization expense		$ 0
Impairment losses on long-lived assets	$ 0	$ 0	$ 0
Number of preclinical research programs | Program	2
Number of combined performance obligation for each research program | item	1
Number of research program performance obligations | item	2
Maximum
Summary of significant accounting policies
Amortization expense	$ 0.1

Summary of significant accoun_7

Summary of significant accounting policies - Comprehensive loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary of significant accounting policies
Foreign currency translation (loss)/gain	$ 1.3	$ (1.4)	$ (0.9)

Collaboration and Licensing A_2

Collaboration and Licensing Agreements (Details) - Gilead Collaboration and License Agreement $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2018USD ($)item	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Collaboration and Licensing Agreements
Number of preclinical research programs | item	2
Upfront payment received	$ 10		$ 2
Payment term (in days)		60 days
Milestone payment received	$ 8		4
Upfront and milestone payments included in deferred revenues		$ 4.3	2.5
Milestone payments included in deferred revenues		4
Cost reimbursements for research and development services included in deferred revenues		1.2	2
Revenue recognized from upfront payment		0.6	10	$ 10
Revenue recognized from milestone payments			2.4		$ 4.4
Revenue recognized from cost reimbursements for research and development services		16.3	13	4.3
Revenue recognized from cost reimbursements for research and development services initially recorded as deferred revenue		2.2	1.1
Revenue recognized from milestone payments for milestones achieved			2.2	$ 3.2
Contract asset relating to the sublicense payment		0.3	0.1
Contract liability relating to sublicense payment		0.3	$ 0.1
Development Milestones
Collaboration and Licensing Agreements
Total milestone amount		300
Milestone Payments One
Collaboration and Licensing Agreements
Revenue recognized from milestone payments		1.5
Milestone Payments Two
Collaboration and Licensing Agreements
Revenue recognized from milestone payments		0
Commercial Milestones
Collaboration and Licensing Agreements
Total milestone amount		$ 115

Fair Value of Financial Asset_2

Fair Value of Financial Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value of Financial Assets
Transfers from Level 1 to Level 2	$ 0
Transfers from Level 2 to Level 1	0
Transfers from into Level 3	0
Transfers from out of Level 3	0
Recurring
Fair Value of Financial Assets
Total	35,403	$ 35,397
Recurring | Money market funds
Fair Value of Financial Assets
Cash equivalents	35,403	35,397
Recurring | Level 1
Fair Value of Financial Assets
Total	35,403	35,397
Recurring | Level 1 | Money market funds
Fair Value of Financial Assets
Cash equivalents	$ 35,403	$ 35,397

Property, plant and equipment_3

Property, plant and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property and equipment
Property and equipment, gross	$ 22,718	$ 11,316
Less: Accumulated depreciation	(6,366)	(5,097)
Property and equipment, net	16,352	6,219
Depreciation expense	2,100	1,700	$ 1,100
Land
Property and equipment
Property and equipment, gross	2,072
Leasehold improvements
Property and equipment
Property and equipment, gross	3,348	3,322
Construction in progress
Property and equipment
Property and equipment, gross	7,746	28
Laboratory equipment
Property and equipment
Property and equipment, gross	7,025	5,982
Furniture and fixtures
Property and equipment
Property and equipment, gross	651	430
Computer equipment and software
Property and equipment
Property and equipment, gross	$ 1,876	$ 1,554

Receivable research incentive (

Receivable research incentive (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Receivable research incentive
Receivable research incentive	$ 14,271	$ 15,115
Income related to the incentive program recorded as grant income	$ 8,900	$ 5,800	$ 5,900

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases
Cash balance maintained to secure a letter of credit associated with a real estate lease	$ 425	$ 434
Presentation of leases in condensed consolidated balance sheets:
Operating lease right-of-use assets	5,673	6,452
Finance lease right-of-use assets	90	1,298
Total lease assets	5,763	7,750
Current operating lease liability	1,682	1,998
Current finance lease liability	$ 21	$ 155
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued Expenses and Other Current Liabilities.	Accrued Expenses and Other Current Liabilities.
Total current lease liabilities	$ 1,703	$ 2,153
Non-current operating lease liability	$ 3,911	3,819
Non-current finance lease liability		$ 258
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
Total non-current lease liabilities	$ 3,911	$ 4,077
Total lease liabilities	$ 5,614	$ 6,230
Minimum
Leases
Remaining lease term (in years)	1 year
Maximum
Leases
Remaining lease term (in years)	4 years

Leases - Lease costs (Details)

Leases - Lease costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases
Net lease expenses	$ 2,510	$ 2,299
Research and development expenses
Leases
Operating lease expenses	1,910	1,654
Finance lease amortization expenses	425	395
General and Administrative Expense
Leases
Operating lease expenses	203	376
Finance lease amortization expenses	7	21
Interest expenses
Leases
Interest on finance lease liabilities	5	8
Other income (expense)
Leases
Sublease income	$ (40)	$ (155)

Leases - Minimum lease payments

Leases - Minimum lease payments (Details) $ in Thousands	Dec. 31, 2021USD ($)
Operating leases
2022	$ 1,585
2023	1,547
2024	1,340
2025	1,242
Total lease payments	5,714
Less: interest	121
Present value of lease liabilities	5,593
Finance leases
2022	21
Total lease payments	21
Less: interest	0
Present value of lease liabilities	21
Total
2022	1,606
2023	1,547
2024	1,340
2025	1,242
Total lease payments	5,735
Less: interest	121
Present value of lease liabilities	$ 5,614

Leases - Weighted average remai

Leases - Weighted average remaining lease term and weighted average discount rate (Details) - USD ($) $ in Millions	1 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating lease, Weighted average remaining lease term (in years)	3 years 8 months 12 days	3 years 1 month 6 days
Operating lease, Weighted average discount rate	1.30%	2.30%
Finance lease, Weighted average remaining lease term (in years)	2 months 12 days	3 years
Finance lease, Weighted average discount rate	0.40%	1.70%
Research and development expenses
Lessee, Lease, Description [Line Items]
Lease modification loss	$ 1

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued expenses and other current liabilities
Salaries and bonuses	$ 4,754	$ 4,381
Social security contributions	250	211
Unearned grant income (current)	693	878
Sublicense fees	304
Accrued external research and development expenses	2,165	895
Accrued external general and administration expenses	629	634
Accrued for property and equipment acquisitions	7
Finance lease liabilities	21	155
Other accruals and liabilities	57	232
Total	$ 8,880	$ 7,386

Loans payable (Details)

Loans payable (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loans payable
Loans from FFG		$ 6,074	$ 6,564
Unamortized debt discount		(1,063)	(2,027)
Total Loans payable, net		$ 5,011	4,537
Interest rate (as a percent)		0.75%
Scheduled early repayment	$ 3,300
Principal payment		$ 0	1,311	$ 842
Unamortized debt discount		1,100	2,000
Interest expense		900	800	900
Amortization of debt discount		$ 800	700	800
Estimated market rate		20.00%
Threshold for change in estimated market rate		0.10
Revenue		$ 18,448	19,584	11,942
Unearned income (current)		5,538	3,750
Unearned income (non-current)		21	784
Adjustment
Loans payable
Deferred income reduced	$ 300
Grant
Loans payable
Revenue		800	700	$ 800
Unearned income (current)		700	900
Unearned income (non-current)		$ 400	$ 1,100

Loans payable - Schedule of agg

Loans payable - Schedule of aggregate minimum future principal payments (Details) $ in Thousands	Dec. 31, 2021USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
2022	$ 3,054
2023	1,821
2024	1,199
Total	$ 6,074

Common stock, Class A common _2

Common stock, Class A common stock and convertible preferred stock (Details) $ / shares in Units, $ in Thousands	Dec. 11, 2020USD ($)$ / sharesshares	Apr. 23, 2019USD ($)$ / sharesshares	Dec. 31, 2021Vote$ / sharesshares	Oct. 31, 2021shares	Dec. 31, 2021Vote$ / sharesshares	Dec. 31, 2021Vote$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Preferred Stock, Shares Authorized			10,000,000		10,000,000	10,000,000	10,000,000
Preferred Stock, Shares Issued			1,697		1,697	1,697
Net proceeds from public offering | $	$ 75,000
Common stock
Common Stock, Shares Authorized			100,000,000		100,000,000	100,000,000	100,000,000
Common stock, issued (in shares)			27,383,483		27,383,483	27,383,483	25,948,712
Common stock, outstanding (in shares)			27,383,483		27,383,483	27,383,483	25,948,712
Issuance of common stock	3,910,000
Share Price | $ / shares	$ 11.75						$ 11.75
Offering costs | $							$ 3,368
Number of votes | Vote			1		1	1
Class A common stock
Common Stock, Shares Authorized			3,900,000		3,900,000	3,900,000	3,900,000
Common stock, issued (in shares)			3,819,732		3,819,732	3,819,732	3,819,732
Common stock, outstanding (in shares)			3,819,732		3,819,732	3,819,732	3,819,732
Number of common stock issued upon conversion of each share						1
Series A Convertible Preferred Stock
Preferred stock shares Designated			2,978		2,978	2,978	2,978
Preferred Stock, Shares Issued	2,978
Preferred Stock, Shares Outstanding			1,697		1,697	1,697	2,978
Share Price | $ / shares	$ 11,750						$ 11,750
Offering costs | $							$ 2,565
Number of common stock issued upon conversion of each share						1,000
Threshold Percentage For Conversion			9.99%		9.99%	9.99%
Liquidation preference per share | $ / shares			$ 0.001		$ 0.001	$ 0.001
Number of shares elected to convert			1,226	55	1,281
Common Stock
Shares issued upon conversion					1,281,000
Common Stock | Common stock
Issuance of common stock							3,910,000	6,000,000
Stock issued upon conversion of Preferred Stock (in shares)						1,281,000		14,582,161
Common Stock | Class A common stock
Stock issued upon conversion of Preferred Stock (in shares)								3,819,732
IPO | Common stock
Share Price | $ / shares								$ 14
Offering costs | $								$ 9,386
Stock issued upon conversion of Preferred Stock (in shares)		14,582,161
IPO | Class A common stock
Stock issued upon conversion of Preferred Stock (in shares)		3,819,732
IPO | Common Stock
Issuance of common stock		6,000,000
Share Price | $ / shares		$ 14
Net proceeds from IPO | $		$ 74,600
Offering costs | $		$ 9,400

Stock-based compensation - 2018

Stock-based compensation - 2018 Stock Option and Grant Plan (Details)	12 Months Ended
	Dec. 31, 2021installment€ / sharesshares	Dec. 31, 2020shares	Dec. 31, 2018$ / shares
Stock-based compensation
Number of shares granted to US employee	990,548
Options outstanding	4,231,178	3,555,945
2018 Stock Option and Grant Plan
Stock-based compensation
Vesting period	4 years
Options outstanding	968,504
2018 Stock Option and Grant Plan | Vesting upon first anniversary
Stock-based compensation
Percentage of options vesting	25.00%
2018 Stock Option and Grant Plan | Vesting in equal quarterly installments
Stock-based compensation
Percentage of options vesting	75.00%
Number of quarterly installments for vesting | installment	12
2016 Stock Option Plan
Stock-based compensation
Percentage of share price with fair market value	100.00%
2016 Stock Option Plan | Exercise price 0.09 euros
Stock-based compensation
Exercise price for options granted as a replacement | € / shares	€ 0.09
Number of shares granted to US employee	23,286
2016 Stock Option Plan | Exercise price $2.93
Stock-based compensation
Exercise price for options granted as a replacement | $ / shares			$ 2.93

Stock-based compensation - 2019

Stock-based compensation - 2019 Stock Option and Incentive Plan (Details)	Apr. 01, 2019installmentshares
Stock-based compensation
Number of common stock entitled for each option upon the exercise of the option | shares	1
2019 Stock Option and Incentive Plan
Stock-based compensation
Number stock option authorized | shares	3,630,686
Number of shares outstanding were cumulatively increased	4.00%
Vesting period	4 years
2019 Stock Option and Incentive Plan | Non Executive Directors
Stock-based compensation
Vesting period	3 years
2019 Stock Option and Incentive Plan | Vesting upon first anniversary
Stock-based compensation
Percentage of options vesting	25.00%
2019 Stock Option and Incentive Plan | Vesting upon first anniversary | Non Executive Directors
Stock-based compensation
Percentage of options vesting	33.00%
2019 Stock Option and Incentive Plan | Vesting in equal quarterly installments
Stock-based compensation
Percentage of options vesting	75.00%
Number of quarterly installments for vesting | installment	12
2019 Stock Option and Incentive Plan | Vesting in equal quarterly installments | Non Executive Directors
Stock-based compensation
Percentage of options vesting	67.00%
Number of quarterly installments for vesting | installment	8

Stock-based compensation - Stoc

Stock-based compensation - Stock option valuation (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assumptions used in the Black-Scholes option-pricing model
Risk-free interest rate	1.07%	0.44%	2.21%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	85.50%	80.20%	74.20%

Stock-based compensation - St_2

Stock-based compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Shares
Beginning balance	3,555,945
Granted	990,548
Exercised	(125,020)
Forfeited	(190,295)
Ending balance	4,231,178	3,555,945
Option exercisable	2,224,349
Option unvested	2,006,829
Weighted Averaged Exercise Price
Beginning balance	$ 8.45
Granted	11.46
Exercised	1.93
Forfeited	11.50
Ending balance	9.21	$ 8.45
Option exercisable	7.62
Option unvested	$ 10.96
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	7 years 6 months	7 years 10 months 24 days
Weighted Average Remaining Contractual Term, option exercisable	6 years 7 months 6 days
Weighted Average Remaining Contractual Term, option unvested	8 years 6 months
Aggregate Intrinsic Value, beginning balance	$ 12,839
Aggregate Intrinsic Value, ending balance	1,640	$ 12,839
Aggregate Intrinsic Value, option exercisable	1,624
Aggregate Intrinsic Value, option unvested	$ 16
Fair value per common stock used for calculating intrinsic values	$ 2.33	$ 11.09	$ 12.23
Aggregate Intrinsic Value, options exercised	$ 1,000	$ 2,900	$ 1,400
Weighted average grant-date fair value per share of stock options granted	$ 11.46	$ 8.95	$ 7.92
Total fair value of stock options vested	$ 6,000	$ 5,600
Cash received from option exercise under share-based payment arrangements	$ 203	$ 63	$ 16

Stock-based compensation - Rest

Stock-based compensation - Restricted Stock Units (Details) - Restricted stock units	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020$ / sharesshares
Stock-based compensation
Number of equal installments of vesting | $	4
Total fair value of restricted stock vested | $	$ 500,000
Number of Shares
Beginning balance | shares	43,700	0
Vested | shares	(43,700)
Ending balance | shares		43,700
Weighted Average Grant Date Fair Value
Beginning balance | $ / shares	$ 11.87
Vested | $ / shares	$ 11.87
Ending balance | $ / shares		$ 11.87

Stock-based compensation - Comm

Stock-based compensation - Common Stock Awards (Details) - Common Stock Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-based compensation
Share-based awards granted	0	36,249	0
Aggregate fair value of share-based awards granted		$ 0.3
Grant date fair value per share		$ 9.56

Stock-based compensation - St_3

Stock-based compensation - Stock-based compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-based compensation
Stock-based compensation expense	$ 7,644	$ 8,657	$ 5,565
Unrecognized compensation cost related to the unvested stock-based awards	$ 5,700
Weighted average periods over which expense is expected to be recognized	1 year 7 months 6 days
Research and development expenses
Stock-based compensation
Stock-based compensation expense	$ 3,200	3,084	1,981
General and Administrative Expense
Stock-based compensation
Stock-based compensation expense	$ 4,444	$ 5,573	$ 3,584

Income taxes (Details)

Income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income taxes
Income tax benefits for the net operating losses incurred	$ 0	$ 0	$ 0
Increase in tax rate differences	4.00%	4.00%	4.00%
Increase in non-taxable research subsidies received	3.80%	4.70%	5.40%
Increase in non-taxable stock-based compensation	1.50%	1.00%	0.30%
Reduction in change in deferred tax asset valuation allowance	30.20%	30.20%	31.00%
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%

Income taxes - Losses before in

Income taxes - Losses before income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income taxes
United States	$ (11,403)	$ (11,603)	$ (7,886)
Foreign (Austria)	(64,261)	(32,479)	(35,151)
Net loss before tax	$ (75,664)	$ (44,082)	$ (43,037)
Company's worldwide effective tax rate	0.00%	0.00%	0.00%

Income taxes - Effective income

Income taxes - Effective income tax reconciliation (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
U.S. federal statutory income tax rate	(21.00%)	(21.00%)	(21.00%)
Foreign tax rate differential	(4.00%)	(4.00%)	(4.00%)
Not taxable government grants	(3.80%)	(4.70%)	(5.40%)
Stock-based compensation	(1.50%)	(1.00%)	(0.30%)
Other	0.10%	0.50%	(0.30%)
Reduction in change in deferred tax asset valuation allowance	30.20%	30.20%	31.00%
Effective income tax rate	0.00%	0.00%	0.00%
Austria
Operating Loss Carryforwards [Line Items]
U.S. federal statutory income tax rate	(25.00%)

Income taxes - Components of th

Income taxes - Components of the net deferred tax assets or liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 55,752	$ 43,563
Credit carryforwards	64	64
Accrued expenses and other	357	(36)
Stock-based compensation	1,209	2,725
Operating lease liabilities	1,378	1,513
Finance lease liabilities	5	103
Total deferred tax assets	58,765	47,932
Valuation allowance	(53,728)	(46,064)	$ (32,583)	$ (19,156)
Total deferred tax assets	5,037	1,868
Deferred tax liabilities:
Accrued expenses and other	(3,604)
Fixed assets and intangible assets	(11)
Operating lease right of use asset	(1,400)	(1,614)
Finance lease right of use asset	(22)	(254)
Total deferred tax liabilities	$ (5,037)	$ (1,868)

Income taxes - Changes in the v

Income taxes - Changes in the valuation allowance for deferred tax assets and others (Details) - USD ($)	12 Months Ended
	Dec. 31, 2026	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Valuation allowance at beginning of period		$ (46,064,000)	$ (32,583,000)	$ (19,156,000)
Increases		(7,664,000)	(13,481,000)	(13,427,000)
Valuation allowance at end of period		$ (53,728,000)	$ (46,064,000)	$ (32,583,000)
Statutory corporate tax rate		21.00%	21.00%	21.00%
Threshold return percentage of GILIT		10.00%
Reduction percentage of inclusion for GILTI		50.00%
Percentage of inclusion for GILTI	37.50%
Unrecognized income tax benefits		$ 0	$ 0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards		17,900,000	8,300,000	$ 4,900,000
Austria
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards		$ 219,700,000	$ 163,200,000	$ 112,300,000
Statutory corporate tax rate		25.00%

Commitments and contingencies -

Commitments and contingencies - Others (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments and contingencies
Non-cancellable obligations	$ 10.5			$ 13.9
2022 deliverables	10.4
2023 deliverables	0.1
Licensing fees from intellectual property licenses	$ 1.3	$ 1.2	$ 1.9

401(k) Savings Plan (Details)

401(k) Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Expenses recognized for the 401(k) Plan	$ 0.4	$ 0.2
Maximum
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution savings plan	100.00%
Employer's Matching contribution to defined contribution savings plan	4.00%

Net loss per share (Details)

Net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (75,665)	$ (44,082)	$ (43,037)
Denominator:
Weighted-average common shares outstanding, basic and diluted	29,945,954	25,876,376	17,859,935
Weighted-average Series A convertible preferred shares outstanding, basic and diluted, presented as if converted into common stock	2,887,636	162,732
Total number of shares used to calculate net loss per share, basic	32,833,590	26,039,108	17,859,935
Total number of shares used to calculate net loss per share, diluted	32,833,590	26,039,108	17,859,935
Net loss per share - basic	$ (2.30)	$ (1.69)	$ (2.41)
Net loss per share - diluted	$ (2.30)	$ (1.69)	$ (2.41)
Number of common stock issued upon conversion of each share of Preferred Stock	1,000
Number of common stock issuable upon conversion of Series A convertible preferred stock	1,697,000

Net loss per share - Antidiluti

Net loss per share - Antidilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Anti-dilutive securities
Anti-dilutive shares	4,231,178	3,599,645	2,999,284
Options
Anti-dilutive securities
Anti-dilutive shares	4,231,178	3,555,945	2,999,284
Restricted stock units
Anti-dilutive securities
Anti-dilutive shares		43,700

Related parties (Details)

Related parties (Details) - University of Basel - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related parties
Royalties paid	$ 0	$ 0	$ 0
Research and development expenses
Related parties
Service fees paid		$ 0.3	$ 0.3

Subsequent events (Details)

Subsequent events (Details) - USD ($)	Feb. 01, 2022	Dec. 11, 2020	Mar. 31, 2022	Feb. 28, 2022	Jun. 30, 2018	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Subsequent events
Granted							990,548
Exercise price							$ 11.46
Purchase price							$ 203,000	$ 42,637,000	$ 74,756,000
Common stock
Subsequent events
Share price (in USD per share)		$ 11.75						$ 11.75
Common stock, par value (in dollars per share)							$ 0.0001	$ 0.0001
Issuance of unregistered shares		3,910,000
Gilead Collaboration and License Agreement
Subsequent events
Milestone payment received					$ 8,000,000			$ 4,000,000
Subsequent event
Subsequent events
Share price (in USD per share)	$ 3					$ 3
Granted	145,071
Exercise price	$ 1.50
Shares issued						112,551
Subsequent event | Follow-on public offering
Subsequent events
Purchase price			$ 70,500,000
Subsequent event | Follow-on public offering | Common stock
Subsequent events
Issuance of unregistered shares			21,700,000
Purchase price per share			$ 2
Subsequent event | Follow-on public offering | Series A-1 convertible preferred stock
Subsequent events
Issuance of unregistered shares			15,800
Purchase price per share			$ 2,000
Subsequent event | Over-allotment option
Subsequent events
Issuance of unregistered shares			5,625,000
Period granted to purchase additional shares			30 days
Subsequent event | Gilead Collaboration and License Agreement
Subsequent events
Milestone payment received				$ 4,000,000
Program initiation fee				15,000,000
Amount of common stock to be purchased				$ 35,000,000
Common stock, par value (in dollars per share)				$ 0.0001
Issuance of unregistered shares				1,666,666
Purchase price				$ 5,000,000
Purchase price per share				$ 3
Subsequent event | Executive team
Subsequent events
Percentage of annual bonus paid through stock options	50.00%