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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Mar. 18, 2020	Jun. 28, 2019
Entity Registrant Name	HOOKIPA Pharma Inc.
Entity Central Index Key	0001760542
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Interactive Data Current	Yes
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Public Float			$ 100,500,000
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Common stock
Entity Common Stock, Shares Outstanding		21,824,990
Class A common stock
Entity Common Stock, Shares Outstanding		3,819,732

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 113,151	$ 48,580
Accounts receivable	1,537	4,919
Receivable tax research premium	8,190	2,329
Prepaid expenses and other current assets	5,139	6,483
Total current assets	128,017	62,311
Non-current assets:
Restricted cash	424
Property and equipment, net	5,126	4,337
Operating lease right of use assets	7,875
Finance lease right of use assets	1,602
Other non-current assets	701	1,603
Total non-current assets	15,728	5,940
Total assets	143,745	68,251
Current liabilities
Accounts payable	944	3,656
Deferred revenues	3,591	6,619
Operating lease liabilities, current	1,814
Accrued expenses and other current liabilities	8,406	4,420
Total current liabilities	14,755	14,695
Non-current liabilities
Loans payable, non-current	3,495	4,392
Operating lease liabilities, non-current	5,290
Deferred revenues, non-current	72	1,663
Other non-current liabilities	2,234	3,102
Total non-current liabilities	11,091	9,157
Total liabilities	25,846	23,852
Commitments and contingencies (Note 13)
Redeemable convertible preferred stock (series A, B, C and D), $0.0001 par value; 0 and 1,323,506 shares authorized, issued and outstanding at December 31, 2019 and December 31, 2018, respectively; aggregate liquidation preference of $0.0 million and $99.7 million at December 31, 2019 and December 31, 2018, respectively		104,774
Stockholders’ equity (deficit):
Additional paid-in capital	225,568	3,327
Accumulated other comprehensive loss	(4,653)	(3,720)
Accumulated deficit	(103,019)	(59,982)
Total stockholders’ equity (deficit)	117,899	(60,375)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	143,745	68,251
Common stock
Stockholders’ equity (deficit):
Common stock	3	$ 0
Class A common stock
Stockholders’ equity (deficit):
Common stock	$ 0

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, authorized	0	1,323,506
Redeemable convertible preferred stock, shares issued	0	1,323,506
Redeemable convertible preferred stock, shares outstanding	0	1,323,506
Preferred stock, aggregate liquidation preference	$ 0.0	$ 99.7
Common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	18,454,860
Common stock, shares issued	21,746,392	1,006,595
Common stock, shares outstanding	21,746,392	1,006,595
Class A common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	3,900,000	0
Common stock, shares issued	3,819,732	0
Common stock, shares outstanding	3,819,732	0

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue from collaboration and licensing	$ 11,942	$ 7,629
Operating expenses:
Research and development	(46,312)	(21,965)	$ (9,772)
General and administrative	(16,715)	(6,844)	(4,385)
Total operating expenses	(63,027)	(28,809)	(14,157)
Loss from operations	(51,085)	(21,180)	(14,157)
Other income (expense):
Grant income	6,737	5,612	2,069
Interest income	1,587	0
Interest expense	(877)	(778)	(606)
Other income and expenses, net	601	133	(25)
Total other income, net	8,048	4,967	1,438
Net loss before tax	(43,037)	(16,213)	(12,719)
Income tax expense	0	(24)	(4)
Net loss	(43,037)	(16,237)	(12,723)
Other comprehensive loss:
Foreign currency translation gain (loss), net of tax	(933)	(2,358)	1,764
Comprehensive loss	$ (43,970)	$ (18,595)	$ (10,959)
Net loss per share—basic and diluted	$ (2.41)	$ (17.76)	$ (13.95)
Weighted average common shares outstanding — basic and diluted	17,859,935	914,375	911,777

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ DEFICIT - USD ($) $ in Thousands	Common Stock Common stock	Common Stock Class A common stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Convertible preferred stock	Series B Preferred Stock	Series C Preferred Stock	Series D Preferred Stock	Total
Balance at the beginning of the period at Dec. 31, 2016						$ 40,189
Balance at the beginning of the period (in shares) at Dec. 31, 2016						547,974
Increase (Decrease) in Temporary Equity
Issuance of preferred stock, net of issuance costs							$ 5,315	$ 59,270
Issuance of preferred stock, net of issuance costs (in shares)							82,032	693,500
Balance at the end of the period at Dec. 31, 2017						$ 104,774
Balance at the end of the period (in shares) at Dec. 31, 2017						1,323,506
Balance at the beginning of the period at Dec. 31, 2016			$ 1,682	$ (3,126)	$ (31,022)					$ (32,466)
Balance at the beginning of the period (in shares) at Dec. 31, 2016	911,777
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options (in shares)										0
Foreign currency translation adjustment, net of tax				1,764						$ 1,764
Stock-based compensation expense			769							769
Net loss					(12,723)					(12,723)
Balance at the end of the period at Dec. 31, 2017			2,451	(1,362)	(43,745)					(42,656)
Balance at the end of the period (in shares) at Dec. 31, 2017	911,777
Balance at the end of the period at Dec. 31, 2018						$ 104,774				$ 104,774
Balance at the end of the period (in shares) at Dec. 31, 2018						1,323,506	492,192	693,500		1,323,506
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options			9							$ 9
Issuance of common stock upon exercise of stock options (in shares)	94,818
Foreign currency translation adjustment, net of tax				(2,358)						(2,358)
Stock-based compensation expense			867							867
Net loss					(16,237)					(16,237)
Balance at the end of the period at Dec. 31, 2018			3,327	(3,720)	(59,982)					$ (60,375)
Balance at the end of the period (in shares) at Dec. 31, 2018	1,006,595
Balance at the end of the period (in shares) at Mar. 31, 2019							492,192	693,500	257,000	1,580,506
Increase (Decrease) in Stockholders' Equity
Net loss										$ (9,329)
Balance at the beginning of the period at Dec. 31, 2018						$ 104,774				$ 104,774
Balance at the beginning of the period (in shares) at Dec. 31, 2018						1,323,506	492,192	693,500		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 end of the period (in shares) at Dec. 31, 2019										0
Balance at the beginning of the period at Dec. 31, 2018			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 common stock upon initial public offering at $14.00 per share for cash, net of issuance costs of $9,386	$ 1		74,614							74,615
Issuance of common stock upon initial public offering at $14.00 per share for cash, net of issuance costs of $9,386(in shares)	6,000,000
Conversion of Series A, B, C and D preferred stock into common stock upon initial public offering	$ 2		142,046							142,048
Conversion of Series A, B, C and D preferred stock into common stock upon initial public offering(in shares)	14,582,161	3,819,732
Issuance of common stock upon exercise of stock options			16							$ 16
Issuance of common stock upon exercise of stock options (in shares)	157,636									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		$ 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

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ DEFICIT (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares
Issuance costs	$ 9,400
Share price \| $ / shares	$ 12.23
IPO
Issuance costs	$ 9,386
Share price \| $ / shares	$ 14.00
Series D convertible preferred stock
Issuance costs	$ 158

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (43,037)	$ (16,237)	$ (12,723)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,565	867	770
Depreciation expense	1,443	640	398
Non-cash operating lease expense	1,624
Other non-cash items	52	7	(45)
Changes in operating assets and liabilities:
Accounts receivable	(3,619)	(4,991)
Prepaid expenses and other current assets	(6,005)	(7,049)	(67)
Other non-current assets	869	(1,465)	(83)
Accounts payable	4,203	3,413	(1,172)
Deferred revenues	(4,442)	8,587
Operating lease liabilities	(2,396)
Accrued expenses and other liabilities	4,012	1,230	1,009
Net cash used in operating activities	(41,731)	(14,998)	(11,913)
Investing activities:
Purchases of property and equipment	(1,999)	(2,150)	(1,297)
Net cash used in investing activities	(1,999)	(2,150)	(1,297)
Financing activities:
Payments related to finance leases	(1,437)
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	37,274	6,439	58,145
Proceeds from issuance of common stock, net of issuance costs	74,756	9
Proceeds from borrowings		425	747
Repayments of borrowings	(842)	0
Net cash provided by financing activities	109,751	6,873	58,892
Net increase (decrease) in cash, cash equivalents and restricted cash	66,021	(10,275)	45,682
Cash, cash equivalents and restricted cash at beginning of period	48,580	61,362	13,186
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1,026)	(2,507)	2,494
Cash, cash equivalents and restricted cash at end of period	113,575	48,580	61,362
Supplemental disclosure of cash flow information:
Cash paid for interest	(64)	(71)	(60)
Cash paid for income taxes		(24)	(4)
Supplemental disclosure of non-cash financing activities:
Due from shareholder for issuance of redeemable convertible preferred stock			6,520
Conversion of redeemable preferred shares upon the IPO	142,048
Property and equipment additions in accounts payable and accrued expenses	$ (10)	$ 545	$ (533)

Nature of the business and organization	12 Months Ended
Nature of the business and organization	Dec. 31, 2019
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 targeting infectious diseases and cancers 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 accounting policies

12 Months Ended

Dec. 31, 2019

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.

Stock split

On April 5, 2019, the Company effected a 11.643‑for-one stock split of its issued and outstanding shares of common stock. The par value of the common stock was not adjusted as a result of the split. All issued and outstanding share and per share amounts of common stock and options included in the accompanying consolidated financial statements have been adjusted to reflect this stock split for all periods presented. The conversion ratios for each series of the Company’s redeemable convertible preferred stock (see Note 9) have been adjusted proportionally.

Transaction between entities under common control

In June 2018, the Company acquired all of the shares of its parent company, Hookipa Biotech AG, against issuance of 78,311 shares of common stock and 1,323,506 shares of redeemable convertible preferred stock to the shareholders of Hookipa Biotech AG, who became the sole shareholders of the Company. The transaction was recorded as a transaction between entities under common control that led to a change in the reporting entity. In the accompanying consolidated financial statements, the assets and liabilities and relating operations of the transferring entity are retrospectively presented at their carrying amounts without a change in the basis for all periods during which the transferring entity was under common control. The share capital as well as the share and per share information included in the accompanying consolidated financial statements have been retrospectively adjusted to reflect the share capital of the Company after the transaction. Differences in the par value of common stock between the transferring and the receiving entity were reflected by adjustments to redeemable convertible preferred stock and additional paid-in capital.

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, 2019, the Company has funded its operations with proceeds from sales of common stock in the IPO, 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 $43.0 million, $16.2 million and $12.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, the Company had an accumulated deficit of $103.0 million. The Company expects to continue to generate operating losses in the foreseeable future. As of March 19, 2020, the filing date of this Annual Report on Form 10‑K, the Company expected that its cash and cash equivalents 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, the present value of lease right of use assets and corresponding liabilities, the valuation of common and preferred stock, the valuation of stock-based awards and the valuation of liabilities. 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. 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 Convertible Preferred Stock and Stockholders' 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. The net proceeds from the Company’s offerings in the year ended December 31, 2019 have been deposited in interest-bearing bank accounts with investment grade US financial institutions and have been partially invested in a money market fund. The money market fund, held in U.S. dollar, is primarily invested in U.S. and foreign short-term debt obligations. As of December 31, 2018 and December 31, 2019, 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.

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, 2019 cash equivalents consisted of money market funds. As of December 31, 2018, the Company had no cash equivalents.

Deferred offering costs

The Company capitalized certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs in prepaid expenses and other current assets 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 generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. Total offering costs of $9.4 million recorded in stockholders’ equity in the year ended December 31, 2019 included $1.4 million of cost incurred in previous periods, which were initially recorded as deferred offering costs as of December 31, 2018.

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(1)		5 years
Laboratory equipment		3 - 10 years
Furniture and fixtures		3 - 10 years
Computer equipment and software		3 - 4 years

(1) In the course of the application of ASC 842, the estimated useful life of the leasehold improvements was adjusted to the shorter period of economic useful life of the asset and lease term.

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.

Leases

The Company adopted the new leasing standards as of January 1, 2019. The new leasing standards were adopted using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. Upon adoption, the Company elected the package of transition practical expedients, which allowed the Company to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. The Company also elected the practical expedient to not reassess certain land easements, elected to use hindsight in determining the lease term and made an accounting policy election to not recognize leases with an initial term of 12 months or less within the consolidated balance sheets and to recognize those lease payments on a straight-line basis in the consolidated statements of operations over the lease term. Upon adoption of the new leasing standards an operating lease asset of $3.3 million and a corresponding operating lease liability of $3.3 million were recorded in the consolidated balance sheets. The adoption of the new leasing standards did not have a material impact on the Company’s consolidated statements of operations.

The determination whether an arrangement was qualified as a lease was made at contract inception. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease assets and 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 operating lease assets may include lease incentives, stated rent increases and escalation clauses linked to rates of inflation when determinable and are recognized as operating lease assets on the consolidated balance sheets. In addition, certain of the Company’s arrangements contain lease and non-lease components. The Company elected to generally separate lease payments from non-lease payments but applied an accounting choice to not separate lease payments from certain non-lease payments for its office and laboratory space leases and its car leases. Operating leases are reflected in operating lease assets, in accrued expenses and other current liabilities and in non-current operating lease liabilities in the consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. The right-of-use asset is tested for impairment in accordance with ASC 360.

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, 2019 and 2018.

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 has entered into a collaboration and license agreement (the "Gilead Agreement") with Gilead Sciences, Inc. ("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 Accounting Standards Codification (ASC) 606. 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 collaboration and licensing 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 collaboration and license 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 collaboration and licensing arrangement also includes certain sales-based milestone and royalty payments upon successful commercialization of a licensed product. In accordance with ASC 606-10-55-65, 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.

Redeemable convertible preferred stock

Upon the closing of the Company’s IPO on April 23, 2019, the Company’s outstanding redeemable convertible preferred stock automatically converted into shares of common stock or Class A common stock. Prior to the conversion, the Company has applied the guidance in ASC 480‑10‑S99‑3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities and had therefore classified the Series A, Series B, Series C and Series D redeemable convertible preferred stock as mezzanine equity. The redeemable convertible preferred stock was recorded outside of stockholders’ equity because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock would have become redeemable at the option of the holders. In the event of a change of control of the Company, proceeds received from the sale of such shares would have been distributed in accordance with the liquidation preferences set forth in the Company’s Preferred Stock agreements. The Company has determined not to adjust the carrying values of the redeemable convertible preferred stock to the liquidation preferences of such shares because of the uncertainty of whether or when such an event would occur.

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 years ended December 31, 2019 and 2018, comprehensive loss included $0.9 million and $2.4 million of foreign currency translation loss adjustments, respectively. For the year ended December 31, 2017 comprehensive loss included $1.8 million of foreign currency translation gain.

Net loss per share

Prior to the closing of its IPO, the Company calculated the basic net loss per share by dividing the net loss by the weighted-average number of shares of common stock outstanding or deemed outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share was the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.

Subsequent to the closing of its IPO, basic net loss per share is computed by dividing the net loss by the weighted average number of shares of 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. 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.

In April 2019, upon the closing of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock automatically converted into 14,582,161 shares of the Company’s common stock and 3,819,732 of the Company’s class A common stock.

The Company reported a net loss attributable to common stockholders for the years ended December 31, 2019, 2018 and 2017.

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.

Adopted as of current period

In February 2016, the FASB issued ASU No. 2016‑02, Leases (Topic 842) ("ASU 2016‑02"), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether cost of the lease is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification.

The FASB subsequently issued the following amendments to ASU 2016‑02 that have the same effective date and transition date: ASU No. 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842, ASU No. 2018‑10, Codification Improvements to Topic 842, Leases, ASU No. 2018‑11, Leases (Topic 842): Targeted Improvements, ASU No. 2018‑20, Narrow-Scope Improvement for Lessors, and ASU No. 2019‑01, Leases (Topic 842): Codification Improvements. The Company adopted these amendments with ASU 2016‑02 (collectively, the new leasing standards) effective January 1, 2019. The new leasing standards were adopted using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. Upon adoption, the Company elected the package of transition practical expedients, which allowed the Company to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. The Company also elected the practical expedient to not reassess certain land easements, elected to use hindsight in determining the lease term and made an accounting policy election to not recognize leases with an initial term of 12 months or less within the consolidated balance sheets and to recognize those lease payments on a straight-line basis in the consolidated statements of operations over the lease term. Upon adoption of the new leasing standards an operating lease asset of $3.3 million and a corresponding operating lease liability of $3.3 million were recorded in the consolidated balance sheets. The adoption of the new leasing standards did not have a material impact on the Company’s consolidated statements of operations.

In July 2017, the FASB issued ASU No. 2017‑11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815) I. Accounting for Certain Financial Instruments with Down Round Features II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception ("ASU 2018‑11"). Part I applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down-round features. Part II replaces the indefinite deferral for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities contained within ASC Topic 480 with a scope exception and does not impact the accounting for these mandatorily redeemable instruments. For public entities, this guidance is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. The Company adopted ASU 2017‑11 as of January 1, 2019. The adoption of this ASU did not have a material impact on its consolidated loss from operations or cash flows.

Recently Issued Accounting Pronouncements

In August 2018, the FASB issued ASU 2018‑15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350‑40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The amendments in this update align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by the amendments in this update. For public entities, this guidance is required to be adopted for annual periods beginning January 1, 2020 and early adoption is permitted. The amendments in this update should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company adopted ASU 2018-15 as of January 1, 2020 using the prospective approach. The Company does not expect the adoption of this ASU to have a material impact on its consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses which was clarified and amended by the issuances of ASUs 2018-19, 2019-04, 2019-05 and 2019-11 in November 2018, April 2019, May 2019 and November 2019, respectively. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis are measured using an expected-loss model, replacing the current incurred-loss model, and recorded through an allowance for credit losses. The guidance also establishes a new impairment model for available-for-sale debt securities. The Company adopted the new standard and the related amendments on January 1, 2020 using a modified retrospective approach. The adoption of this ASU did not have a material impact on its consolidated financial statements.

In November 2018, the FASB issued ASU 2018-18, Clarifying the Interaction Between Topic 808 and Topic 606, which clarifies when transactions between participants in a collaborative arrangement are within the scope of the FASB’s revenue standard, Topic 606. This ASU becomes effective for the Company in the year ending December 31, 2020 and early adoption is permitted. The Company is currently assessing the impact that this ASU will have on its consolidated financial statements.

In August 2018, the FASB issued ASU 2018‑13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, (“ASU 2018‑13”). The new standard removes certain disclosures, modifies certain disclosures and adds additional disclosures related to fair value measurement. The new standard will be effective beginning January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2018‑13 will have on its consolidated financial statements.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which eliminates certain exceptions related to the general principles in ASC 740 and makes amendments to other areas with the intention of simplifying various aspects related to accounting for income taxes. The pronouncement is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating the potential impact of the adoption of these updates on its consolidated financial statements.

Collaboration and Licensing Agreements	12 Months Ended
Collaboration and Licensing Agreements	Dec. 31, 2019
Collaboration and Licensing Agreements
Collaboration and Licensing Agreements	3. Collaboration and Licensing Agreements Gilead Collaboration and License Agreement In June 2018, the Company has entered into a collaboration and license agreement (the “Gilead Agreement”) with Gilead Sciences, Inc. (“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). Under the Gilead Agreement, the Company granted Gilead an exclusive, royalty-bearing license to the Company’s technology platforms. In June 2018, the Company has received a non-refundable $10.0 million upfront payment from Gilead of which $4.4 million was recorded as revenue from collaboration and licensing in the year ended December 31, 2019 and $2.6 million was included as a liability in deferred revenues, current and non-current, as of December 31, 2019. In addition deferred revenues as of December 31, 2019 include a prepayment received from Gilead related to ordered manufacturing services of $1.0 million. Approximately 97% of the upfront payment included in deferred revenue as of December 31, 2019 is expected to be recognized in 2020 and the remaining 3% in 2021. 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 a total of $280 million. The commercial milestones amount to a total of $100 million. Additionally, Gilead is obligated to pay royalties on net sales for each program. All payments from Gilead have a 60 days payment term. In addition to the $4.4 million recognition of the upfront payment, the Company recognized $4.3 million revenue from cost reimbursements for research and development services and $3.2 million in milestone payments in the year ended December 31, 2019. For the year ended December 31, 2018, revenue from reimbursement of research and development expenses was $2.0 million, revenue from partial recognition of the upfront payment was $2.8 million, and revenue for the achievement of the first pre-clinical milestone was $2.8 million. Sublicense fees payable to certain licensors of technologies upon the receipt of the non-refundable upfront payment, 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, 2019, the contract asset relating to the sublicense payment was $0.3 million. As of December 31, 2018, the liability and the contract asset relating to the sublicense payment were $0.5 million and $0.4 million, respectively.

Fair Value of Financial Assets

12 Months Ended

Dec. 31, 2019

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, 2019 Using
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	35,132	$	—	$	—	$	35,132
Total	$	35,132	$	—	$	—	$	35,132

The Company did not have any money market funds as of December 31, 2018.

During the year ended December 31, 2019, there were no transfers between Level 1, Level 2 and Level 3.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and equipment, net

12 Months Ended

Dec. 31, 2019

Property and equipment, net

Property and equipment, net

5. Property and equipment, net

Property and equipment, net consisted of the following (in thousands):


	Year ended December 31,
	2019		2018

Leasehold improvements	$	1,919	$	1,885
Finance lease right of use assets		1,967		—
Construction in progress		286		—
Laboratory equipment		4,555		3,443
Furniture and fixtures		524		352
Computer equipment and software		923		723
Property and equipment, gross		10,174		6,403
Less: Accumulated depreciation		(3,446)		(2,066)
Property and equipment, net	$	6,728	$	4,337

Depreciation expense for the years ended December 31, 2019, 2018 and 2017 was $1.4 million, $0.6 million and $0.4 million, respectively. Construction-in-progress as of December 31, 2019 related to leasehold improvements in connection with the expansion of laboratories in the Company's leased facilities. The table presented above consists of the balance sheet items property and equipment and finance lease right of use assets.

Leases

12 Months Ended

Dec. 31, 2019

Leases

Leases

6. 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 1 years 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, 2019.

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,
	Balance sheet location	2019
Assets
Operating lease assets, net	Operating lease right of use assets	$	7,875
Finance lease assets, net	Finance lease right of use assets		1,602
Total lease assets			9,477
Liabilities
Current operating lease liability	Operating lease liabilities, current		1,814
Current finance lease liability	Accrued expenses and other current liabilities		159
Total current lease liabilities			1,973
Non-current operating lease liability	Operating lease liabilities, non-current		5,290
Non-current finance lease liability	Other non-current liabilities		367
Total non-current lease liabilities			5,657
Total lease liabilities		$	7,630

In the year ended December 31, 2019 the Company terminated a lease of office space and derecognized the relating right of use asset and the lease liability of $0.2 million.

The following table summarizes the effect of lease costs in the Company’s consolidated statements of operations and comprehensive loss (in thousands):


		Year ended
	Income statement location	December 31, 2019
Operating lease expenses	Research and development expenses	$	1,108
	General and administrative expenses		712
Finance lease amortization expenses	Research and development expenses		350
	General and administrative expenses		14
Interest on finance lease liabilities	Interest expenses		9
Sublease income	Other income (expense)		(128)
Net lease expense		$	2,065

The minimum lease payments for the next five years and thereafter are expected to be as follows (in thousands):


	December 31, 2019
	Operating lease		Finance lease		Total
2020		1,826		155		1,981
2021		1,832		138		1,970
2022		1,830		122		1,952
2023		1,818		120		1,938
2024		128		10		138
Thereafter		—		—		—
Total lease payments		7,434		545		7,979
Less: interest		330		19		349
Present value of lease liabilities	$	7,104	$	526	$	7,630

Under the prior lease guidance minimum rental commitments under non-cancelable leases for each of the next five years and total thereafter as of December 31, 2018, were as follows (in thousands):


Year ending December 31	Amount
2019	$	520
2020		278
2021		43
2022		43
2023		11
Thereafter		—
Total	$	895

Rent expense under operating leases for the years ended December 31, 2018 and 2017 was $1.1 million and $0.6 million, respectively.

These annual minimum lease payments did not include the embedded lease obligations under service agreements, which commenced in the year ended December 2019.

The weighted average remaining lease term and weighted average discount rate of operating leases are as follows:


	December 31,
	2019

Weighted average remaining lease term in years	4.1
Weighted average discount rate (1)	2.3	%

(1) The majority of the contracts are concluded in euros. The discount rate was determined on a currency-equivalent basis.

The weighted average remaining lease term and weighted average discount rate of finance leases are as follows:


	December 31,
	2019

Weighted average remaining lease term in years	3.9
Weighted average discount rate (1)	1.7	%

(1) The contracts are concluded in euros. The discount rate was determined on a currency-equivalent basis.

The Company subleases certain of its leased real estate that it does not currently utilize to a third party. The sublease has a remaining lease terms of 1.2 years without an option to renew and has been qualified as an operating lease. The Company recognizes sublease income in its consolidated statements of operations and comprehensive loss. The Company continued to account for the head lease as it did before sublease commencement.

Accrued expenses and other current liabilities

12 Months Ended

Dec. 31, 2019

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities

7. Accrued expenses and other current liabilities

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


	December 31,
	2019		2018

Consulting fees	$	724	$	1,764
Salaries and bonuses		2,640		1,404
Social security contributions		177		121
Unearned grant income (current)		725		833
Loans		1,224		—
Invoices not yet received		2,673		—
Finance lease liabilities		159		—
Other accruals and liabilities		84		298
	$	8,406	$	4,420

Loans payable

12 Months Ended

Dec. 31, 2019

Loans payable

Loans payable

8. Loans payable

As of December 31, 2019 and December 31, 2018, loans payable consisted of the following (in thousands):


	Year ended December 31,
	2019		2018

Loans from FFG	$	7,305	$	8,316
Unamortized debt discount		(2,586)		(3,924)
Total Loans payable, net	$	4,719	$	4,392

Note: The short-term portion of the loans are included in other current liabilities.

In connection with the funding agreements with the Austrian Research Promotion Agency, (Österreichische Forschungsförderungsgesellschaft, or “FFG”), the Company has received various loans (“FFG Loans”). The FFG Loans were made on a project-by-project basis. Amounts due under the FFG Loans bear interest at rates ranging from 0.75% to 1.0% per annum and mature at various dates between March 2020 and March 2024. Interest on amounts due under the loans is payable semi-annually in arrears, with all principal and remaining accrued interest due upon maturity.

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 $0.5 million during the years ended December 31, 2019, 2018 and 2017, 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, $0.8 million and $0.7 million as of December 31, 2019, 2018 and 2017, respectively, and unearned income (non-current) presented under loans payable non-current related to such benefit was $1.9 million, $3.0 million and $3.8 million as of December 31, 2019, 2018 and 2017, 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, 2019 and 2018, the unamortized debt discount related to FFG Loans was $2.6 million and $3.9 million, respectively.

The Company recognized interest expense of $0.9 million, $0.8 million and $0.6 million during the years ended December 31, 2019, 2018 and 2017, 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 $0.5 million during the years ended December 31, 2019, 2018 and 2017, respectively. A principal payment of $0.8 million was made in the year ended December 31, 2019. There were no principal payments due or paid under the FFG Loans during the year ended December 31, 2018.

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 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, 2019, the aggregate minimum future principal payments due in connection with the FFG Loans are summarized as follows (in thousands):


Year ending December 31,	Amount
2020		1,280
2021		—
2022		3,029
2023		1,806
2024		1,190
Thereafter		—
Total	$	7,305

Redeemable convertible preferred stock

12 Months Ended

Dec. 31, 2019

Redeemable convertible preferred stock

Redeemable convertible preferred stock

9. Redeemable convertible preferred stock

Redeemable convertible preferred stock

The Company previously issued Series A redeemable convertible preferred stock (the "Series A Preferred Stock"), Series B redeemable convertible preferred stock (the "Series B Preferred Stock"), Series C redeemable convertible preferred stock (the "Series C Preferred Stock") and Series D redeemable convertible preferred stock (the "Series D Preferred Stock"). Upon the closing of the Company’s IPO in April 2019, the Company’s outstanding redeemable convertible preferred stock automatically converted into shares of common stock or, if elected by the holder, into Class A common stock. Prior to conversion, the Preferred Stock had certain contingent redemption features based upon the occurrence of events that were not solely within the control of the Company and was therefore classified as mezzanine equity.

In December 2017, the Company issued and sold 693,500 shares of Series C Preferred Stock at an average price of $85.60 per share for gross proceeds of $59.4 million. An amount of $6.5 million of the gross proceeds from the issuance of Series C Preferred Stock was received on January 4, 2018. The Company incurred issuance costs in connection with the Series C Preferred Stock of $0.1 million.

In February 2019, the Company issued and sold 257,000 shares of Series D Preferred Stock at an average price of $145.65 per share for gross proceeds of $37.4 million. The Company incurred issuance costs in connection with the Series D Preferred Stock of $0.2 million.

Upon issuance of each class of Preferred Stock, the Company assessed the embedded conversion and liquidation features of the shares and determined that such features did not require the Company to separately account for these features. The Company also concluded that no beneficial conversion feature existed on the issuance date of each class of Preferred Stock.

Upon the closing of the Company’s IPO, on April 23, 2019, all 1,580,506 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. The related carrying value of $142.0 million was reclassified to common stock and additional paid-in capital.

As of December 31, 2019, the Company had no shares of Preferred Stock outstanding. The Company is authorized to issue 10,000,000 shares of undesignated preferred stock.

Prior to the IPO, the shares of Preferred Stock consisted of the following (in thousands, except share amounts):


		Preferred
	Preferred	shares			Common stock
	shares	issued and	Carrying		issuable upon
	authorized	outstanding	value		conversion
Series A Preferred Stock	137,814	137,814	$	0.014	1,604,574
Series B Preferred Stock	492,192	492,192		0.049	5,730,612
Series C Preferred Stock	693,500	693,500		0.069	8,074,447
Series D Preferred Stock	257,000	257,000		0.026	2,992,260
	1,580,506	1,580,506	$	0.158	18,401,893

As of December 31, 2018, the outstanding shares of Preferred Stock consisted of the following (in thousands, except share amounts):


		Preferred
	Preferred	shares			Common stock
	shares	issued and	Carrying		issuable upon
	authorized	outstanding	value		conversion
Series A Preferred Stock	137,814	137,814	$	0.014	1,604,574
Series B Preferred Stock	492,192	492,192		0.049	5,730,612
Series C Preferred Stock	693,500	693,500		0.069	8,074,447
	1,323,506	1,323,506	$	0.132	15,409,633

Prior to the conversion of the Preferred Stock upon closing of the IPO, the rights, preferences, and privileges of the Preferred Stock were as follows:

Conversion

Each share of Preferred Stock was convertible, at the option of the holder, at any time, and without the payment of additional consideration, into 11.643 fully paid and non-assessable shares of common stock or non-voting Class A common stock as determined by dividing the original issue price paid for such Preferred Shares by the applicable conversion price in effect at the time of conversion.

Liquidation

In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or certain deemed liquidation events, the holders of Preferred Shares had a right to receive, certain amounts in preference to any distribution to the holders of common stock.

Common stock and Class A common stock	12 Months Ended
Common stock and Class A common stock	Dec. 31, 2019
Common stock and Class A common stock
Common stock and Class A common stock	10. Common stock and Class A common stock In June 2018 the Company became the reporting entity in a transaction between entities under common control. In the accompanying consolidated financial statements and notes, the common stock is retrospectively presented as if the Company had been the reporting entity for all periods during which the previous reporting entity was under common control. 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. As of December 31, 2018, the Company was authorized to issue 18,454,860 shares of common stock and had 1,006,595 shares of common stock outstanding and issued. As of December 31, 2019, the Company was authorized to issue 100,000,000 shares of common stock and 3,900,000 shares of Class A common stock and had 21,746,392 shares of common stock and 3,819,732 shares of Class A common stock outstanding and issued. 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 are not entitled to vote, except as required by law. 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. The holders of common stock and Class A common stock do not have any cumulative voting rights. Subject to any preferential dividend rights of any outstanding preferred stock, 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. 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 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, subject to the preferences that may be applicable to any outstanding shares of preferred stock.

Stock-based compensation

12 Months Ended

Dec. 31, 2019

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 for all periods during which the previous reporting entity was under common control.

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 10th anniversary of the grant date. As of December 31, 2019, 1,357,764 options granted under the 2018 Stock Option and Grant Plan remained outstanding. Any authorization to issue new options under the 2018 Stock Option and Grant Plan was cancelled upon the effectiveness of the 2019 Stock Option and Incentive Plan and no further awards will be granted under the 2018 Plan.

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 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 2,608,042, 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 10th anniversary of the grant date. For each option the beneficiary is entitled to receive one share of common stock upon the exercise of the option.

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 of 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 December 31,
	2019		2018		2017

Risk-free interest rate	2.21	%	2.78	%	(0.67)	%
Expected term (in years)	6.1		5.1		2.8
Expected volatility	74.2	%	72.1	%	66.1	%
Expected dividends	—	%	—	%	—	%

For option grants in 2017, the Company used AAA-rated euro area central government bond yields as the basis for the risk-free interest rate in the Black-Scholes model. For 2018 and 2019 option grants, following the change of incorporation to the United States, the Company used a risk-free interest rate based on the U.S. Treasury yield curve in effect at the time of grant. For the 2019 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, 2019 (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, 2018	1,606,325	$	1.95	8.0	$	13,466
Granted	1,661,200		12.34
Exercised	(157,636)		0.10
Forfeited	(110,605)		6.72
Outstanding as of December 31, 2019	2,999,284	$	7.63	8.1	$	15,840

Options exercisable as of December 31, 2019	836,105	$	0.88	6.1	$	9,488
Options unvested as of December 31, 2019	2,163,179	$	10.23	8.9	$	6,352

The aggregate intrinsic value of stock options was calculated as the difference between the exercise price of the stock options and the estimated 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 estimated fair value per common stock used for calculating the intrinsic values as of December 31, 2019 and December 31, 2018, was $12.23 and $10.33, respectively.

The aggregate intrinsic value of options exercised during the years ended December 31, 2019 and 2018 was $1.4 million and $1.0 million, respectively. There were no options exercised during the year ended December 31, 2017.

The weighted average grant-date fair value per share of stock options granted during the years ended December 31, 2019 and 2018 was $7.92 and $2.55, respectively.

Cash received from option exercise under share-based payment arrangements for the years ended December 31, 2019 and 2018 was $16 thousand and $9 thousand, respectively. No cash from option exercise was received in the year ended December 31, 2017.

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,
	2019		2018		2017

Research and development expenses	$	1,981	$	399	$	295
General and administrative expenses		3,584		468		475
	$	5,565	$	867	$	770

In the year ended December 31, 2018, the terms of 2,000 outstanding stock options were modified to increase the exercise price from $1.17 to $34.12. The Company determined that the fair value of the modified award on the effective date of the modification was smaller than the fair value of the original award immediately before the modification. Therefore, the modification did not lead to recognition of additional compensation cost or a change in unrecognized compensation cost.

As of December 31, 2019 and 2018, total unrecognized compensation cost related to the unvested stock-based awards was $9.3 million and $2.2 million, respectively, which is expected to be recognized over weighted average periods of 1.8 and 1.7 years, respectively.

Income taxes

12 Months Ended

Dec. 31, 2019

Income taxes

Income taxes

12. Income taxes

During the years ended December 31, 2019, 2018 and 2017, 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, 2019, 2018 and 2017 consisted of the following (in thousands):


	Year ended December 31,
	2019		2018		2017
United States	$	(7,886)	$	(604)	$	(121)
Foreign (Austria)		(35,151)		(15,609)		(12,598)
Net loss before tax	$	(43,037)	$	(16,213)	$	(12,719)

The Company's worldwide effective tax rate for the years ended December 31, 2019, 2018 and 2017 was 0.0%, (0.1)% 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, 2019 and 2018 and 35% for the year ended December 31, 2017 and the effective tax rate:


	Year ended December 31,
	2019			2018			2017
U.S. federal statutory income tax rate		(21.0)	%		(21.0)	%		(35.0)	%
State income taxes, net of federal benefit		—			—			—
Foreign tax rate differential(1)		(4.0)			(4.0)			10.0
Not taxable government grants(2)		(5.4)			(7.5)			(3.0)
Stock-based compensation(3)		(0.3)			(4.6)			(3.5)
other		(0.3)			(0.5)			—
Change in deferred tax asset valuation allowance(4)		31.0			37.5			31.5
Effective income tax rate		—	%		(0.1)	%		—	%

(1) The 4% increase for the years ended December 31, 2019 and 2018, respectively, and the 10% reduction for the year ended December 31, 2017 resulted from tax rate differences between U.S. and non-U.S. jurisdictions. Net loss before tax was principally generated in Austria, where the statutory tax rate is 25%.

(2) For the years ended December 31, 2019, 2018 and 2017, 5.4%, 7.5% and 3.0% increase, respectively, resulted from non-taxable research subsidies received from Austrian government agencies.

(3) For the years ended December 31, 2019, 2018 and 2017, 0.3% increase, 4.6% increase and 3.5% increase, respectively, resulted from non-taxable Stock-based compensation expense.

(4) For the years ended December 31, 2019, 2018 and 2017, 31.0% reduction, 37.5% reduction and 31.5% reduction, respectively, resulted from changes in valuation allowance on deferred tax assets. Deferred tax assets will only be recovered when the generation of future taxable income is more likely than not. Due to the nature of the Company's research activities and the inherent uncertainties the deferred tax assets have been fully impaired.

Components of the net deferred tax assets or liabilities as of the years ended December 31, 2019 and 2018 consisted of the following (in thousands):


	Year ended December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	29,180	$	19,011
Credit carryforwards		180		—
Accrued expenses and other		669		94
Stock-based compensation		2,717		51
Operating lease liabilities		1,740		—
Other liabilities		132		—
Total deferred tax assets		34,618		19,156
Valuation allowance		(32,583)		(19,156)
Total deferred tax assets		2,035		—

Deferred tax liabilities:
Operating lease right of use asset		(1,808)		—
Finance lease right of use asset		(227)		—
Total deferred tax liabilities		(2,035)		—

Net deferred tax assets	$	—	$	—

As of December 31, 2019, 2018 and 2017, the Company had Austrian net operating loss carryforwards of $112.3 million, $76.0 million and $55.2 million, respectively, 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, 2019, 2018 and 2017. 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. As of December 31, 2019, there were no pending income tax examinations.

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2019, 2018 and 2017 related primarily to the increases in net operating loss carryforwards as follows (in thousands):


	Year ended December 31,
	2019		2018		2017
Valuation allowance at beginning of period	$	(19,156)	$	(13,789)	$	(8,378)
Increases		(13,427)		(5,367)		(5,411)
Valuation allowance at end of period	$	(32,583)	$	(19,156)	$	(13,789)

On December 22, 2017, the United States enacted the Tax Cuts and Jobs Act ("Tax Reform Legislation" or "TCJA"), which made significant changes to U.S. federal income tax code, including a reduction of the statutory corporate tax rate from 35% to 21%, effective on January 1, 2018. This new legislation also eliminated or reduced certain corporate income tax deductions as well as introduced new provisions that taxed certain foreign income not previously taxed in the United States. The TCJA also includes a provision for a tax on all previously undistributed earnings of U.S. companies located in foreign jurisdictions. Undistributed earnings in the form of cash and cash equivalents is taxed at a rate of 15.5% and all other earnings are taxed at a rate of 8.0%. This tax is payable over 8 years and will not accrue interest.

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.

Due to its loss making situation, the Company has established a full valuation allowance against its deferred tax assets as of December 31, 2019, 2018 and 2017 and the changes under the Tax Reform Legislation therefore did not have an effect on its deferred tax assets and liabilities and deferred tax asset valuation allowances in the period the tax regimen change was enacted.

The Company files income tax returns in the U.S. federal jurisdiction as well as in New York. The tax year 2018 remains open to examination by the jurisdictions in which the Company is subject to tax. Furthermore, the Company files income tax returns in Austria. The tax years 2015 to 2018 remain open to examination by the jurisdictions in which the Company is subject to tax.

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, 2019, the Company had no unrecognized income tax benefits that would affect the Company’s effective tax rate if recognized.

Commitments and contingencies	12 Months Ended
Commitments and contingencies	Dec. 31, 2019
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, 2019, the Company’s total non-cancellable obligations under contracts with CMOs, excluding embedded lease liabilities, were $13.1 million, of which $10.2 million relate to 2020 deliverables, $2.9 million relate to 2021 deliverables and no payments relate to 2022 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 2021. 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. 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, 2019 and 2018, the Company recorded $1.9 million and $0.1 million, respectively, in licensing fees from 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, 2019 and December 31, 2018. 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. 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 any asserted or un-asserted legal claims or proceedings, individually or in the aggregate, will have a material adverse effect on the Company. The Company expenses the costs related to such legal proceedings as incurred.

401(k) Savings Plan	12 Months Ended
401(k) Savings Plan	Dec. 31, 2019
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, 2019, 2018 and 2017, expenses recognized for the 401(k) Plan were insignificant.

Net loss per share

12 Months Ended

Dec. 31, 2019

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,
	2019		2018		2017

Numerator:
Net loss	$	(43,037)	$	(16,237)	$	(12,723)

Denominator:
Weighted-average common shares outstanding, basic and diluted		17,859,935		914,375		911,777

Net loss per share, basic and diluted	$	(2.41)	$	(17.76)	$	(13.95)

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 conversion) that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	Year ended December 31,
	2019	2018	2017

Series A Preferred Stock	—	1,604,574	1,604,574
Series B Preferred Stock	—	5,730,612	5,730,612
Series C Preferred Stock	—	8,074,447	8,074,447
Series D Preferred Stock	—	—	—
Options issued and outstanding	2,999,284	1,606,325	1,434,150
Total	2,999,284	17,015,958	16,843,783

Related parties	12 Months Ended
Related parties	Dec. 31, 2019
Related parties
Related parties	16. Related parties The Company is party to research and service arrangements with the University of Basel. The Company’s Chief Scientific Officer and his spouse are employees of the University of Basel and both involved in providing the services under these arrangements. In the years ended December 31, 2019, 2018 and 2017, the Company recorded $0.3 million, $0.4 million and $0.3 million, respectively, in research and development expenses for service fees paid to the University of Basel. 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 Chief Scientific Officer in the course of his consulting services to the Company. In the years ended December 31, 2019, 2018 and 2017, no royalties were paid pursuant to the terms of this arrangement. During the year ended December 31, 2019, the Company issued 50,670 shares of Series D Preferred Stock for total gross proceeds of $7.4 million and 1,303,750 shares of common stock for total gross proceeds of $18.3 million to certain stockholders that were related parties as part of the IPO. During the year ended December 31, 2018, the Company issued no shares to stockholders that were related parties. During the year ended December 31, 2017, the Company issued 61,524 shares of Series B Preferred Stock for total proceeds of $4.0 million and 147,712 shares of Series C Preferred Stock for total proceeds of $12.6 million to certain stockholders that were related parties. The due from shareholder amount of $6.5 million as of December 31, 2017 is from one of these related parties.

Selected Quarterly Financial information (unaudited)

12 Months Ended

Dec. 31, 2019

Selected Quarterly Financial Information (Unaudited)

Selected Quarterly Financial Information (Unaudited)

17. Selected Quarterly Financial Information (Unaudited)

The following information has been derived from unaudited condensed consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information (in thousands except per share data) for the years ended December 31, 2019 and 2018 are as follows:



	2019 Quarter Ended
	March 31,		June 30,		September 30,		December 31,
Revenue	$	2,235	$	4,051	$	2,038	$	3,618
Operating expenses		(12,890)		(17,680)		(15,614)		(16,843)
Net loss		(9,329)		(12,079)		(11,385)		(10,244)
Net loss per share - basic and diluted	$	(9.27)	$	(0.63)	$	(0.45)	$	(0.40)



	2018 Quarter Ended
	March 31,		June 30,		September 30,		December 31,
Revenue	$	—	$	649	$	1,900	$	5,080
Operating expenses		(6,449)		(7,624)		(7,452)		(7,284)
Net loss		(4,573)		(5,819)		(3,953)		(1,892)
Net loss per share - basic and diluted	$	(5.02)	$	(6.38)	$	(4.34)	$	(2.05)

Summary of significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2019

Summary of significant accounting policies

Basis of presentation

Stock split

Transaction between entities under common control

Going concern

Use of estimates

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.

Concentrations of credit risk and of significant suppliers

Cash equivalents

Deferred offering costs

Fair value measurements

Level 1 - Quoted prices in active markets for identical assets or liabilities.

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


		Estimated useful life
Leasehold improvements(1)		5 years
Laboratory equipment		3 - 10 years
Furniture and fixtures		3 - 10 years
Computer equipment and software		3 - 4 years

(1) In the course of the application of ASC 842, the estimated useful life of the leasehold improvements was adjusted to the shorter period of economic useful life of the asset and lease term.

Leases

Impairment of long-lived Assets

Impairment of long-lived assets

Segment information

Revenue recognition from contracts with customers

Upfront payment

Reimbursement for services

Research and development milestones

Sales-based milestones and royalty payments

Cost to fulfill contracts

Research and development costs

Research and manufacturing contract costs and accruals

Government grant agreements and research incentives

Redeemable convertible preferred stock

Stock-based compensation

Comprehensive loss

Net loss per share

The Company reported a net loss attributable to common stockholders for the years ended December 31, 2019, 2018 and 2017.

Income Taxes.

Income taxes

Recent accounting pronouncements

Adopted as of current period

Recently Issued Accounting Pronouncements

Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2019

Summary of significant accounting policies

Schedule of estimated useful life of each asset


		Estimated useful life
Leasehold improvements(1)		5 years
Laboratory equipment		3 - 10 years
Furniture and fixtures		3 - 10 years
Computer equipment and software		3 - 4 years

(1) In the course of the application of ASC 842, the estimated useful life of the leasehold improvements was adjusted to the shorter period of economic useful life of the asset and lease term.

Fair Value of Financial Assets (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value of Financial Assets

Schedule of financial assets measured at fair value on a recurring basis


	Fair Value Measurement at December 31, 2019 Using
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	35,132	$	—	$	—	$	35,132
Total	$	35,132	$	—	$	—	$	35,132

Property and equipment, net (Tables)

12 Months Ended

Dec. 31, 2019

Property and equipment, net

Schedule of property and equipment, net

Property and equipment, net consisted of the following (in thousands):


	Year ended December 31,
	2019		2018

Leasehold improvements	$	1,919	$	1,885
Finance lease right of use assets		1,967		—
Construction in progress		286		—
Laboratory equipment		4,555		3,443
Furniture and fixtures		524		352
Computer equipment and software		923		723
Property and equipment, gross		10,174		6,403
Less: Accumulated depreciation		(3,446)		(2,066)
Property and equipment, net	$	6,728	$	4,337

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases

Schedule of operating and finance leases presentation in the consolidated balance sheets


		December 31,
	Balance sheet location	2019
Assets
Operating lease assets, net	Operating lease right of use assets	$	7,875
Finance lease assets, net	Finance lease right of use assets		1,602
Total lease assets			9,477
Liabilities
Current operating lease liability	Operating lease liabilities, current		1,814
Current finance lease liability	Accrued expenses and other current liabilities		159
Total current lease liabilities			1,973
Non-current operating lease liability	Operating lease liabilities, non-current		5,290
Non-current finance lease liability	Other non-current liabilities		367
Total non-current lease liabilities			5,657
Total lease liabilities		$	7,630

Summary of the effect of lease costs


		Year ended
	Income statement location	December 31, 2019
Operating lease expenses	Research and development expenses	$	1,108
	General and administrative expenses		712
Finance lease amortization expenses	Research and development expenses		350
	General and administrative expenses		14
Interest on finance lease liabilities	Interest expenses		9
Sublease income	Other income (expense)		(128)
Net lease expense		$	2,065

Summary of maturities of operating lease liabilities


	December 31, 2019
	Operating lease		Finance lease		Total
2020		1,826		155		1,981
2021		1,832		138		1,970
2022		1,830		122		1,952
2023		1,818		120		1,938
2024		128		10		138
Thereafter		—		—		—
Total lease payments		7,434		545		7,979
Less: interest		330		19		349
Present value of lease liabilities	$	7,104	$	526	$	7,630

Summary of maturities of finance lease liabilities


	December 31, 2019
	Operating lease		Finance lease		Total
2020		1,826		155		1,981
2021		1,832		138		1,970
2022		1,830		122		1,952
2023		1,818		120		1,938
2024		128		10		138
Thereafter		—		—		—
Total lease payments		7,434		545		7,979
Less: interest		330		19		349
Present value of lease liabilities	$	7,104	$	526	$	7,630

Schedule of minimum rental commitments under non-cancelable leases

Under the prior lease guidance minimum rental commitments under non-cancelable leases for each of the next five years and total thereafter as of December 31, 2018, were as follows (in thousands):


Year ending December 31	Amount
2019	$	520
2020		278
2021		43
2022		43
2023		11
Thereafter		—
Total	$	895

Schedule of weighted average remaining lease term and weighted average discount rate of operating leases


	December 31,
	2019

Weighted average remaining lease term in years	4.1
Weighted average discount rate (1)	2.3	%

(1) The majority of the contracts are concluded in euros. The discount rate was determined on a currency-equivalent basis.

Schedule of weighted average remaining lease term and weighted average discount rate of finance leases


	December 31,
	2019

Weighted average remaining lease term in years	3.9
Weighted average discount rate (1)	1.7	%

(1) The contracts are concluded in euros. The discount rate was determined on a currency-equivalent basis.

Accrued expenses and other current liabilities (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019		2018

Consulting fees	$	724	$	1,764
Salaries and bonuses		2,640		1,404
Social security contributions		177		121
Unearned grant income (current)		725		833
Loans		1,224		—
Invoices not yet received		2,673		—
Finance lease liabilities		159		—
Other accruals and liabilities		84		298
	$	8,406	$	4,420

Loans payable (Tables)

12 Months Ended

Dec. 31, 2019

Loans payable

Schedule of loans payable


	Year ended December 31,
	2019		2018

Loans from FFG	$	7,305	$	8,316
Unamortized debt discount		(2,586)		(3,924)
Total Loans payable, net	$	4,719	$	4,392

Schedule of aggregate minimum future principal payments due in connection with the FFG Loans

As of December 31, 2019, the aggregate minimum future principal payments due in connection with the FFG Loans are summarized as follows (in thousands):


Year ending December 31,	Amount
2020		1,280
2021		—
2022		3,029
2023		1,806
2024		1,190
Thereafter		—
Total	$	7,305

Redeemable convertible preferred stock (Tables)

12 Months Ended

Dec. 31, 2019

Redeemable convertible preferred stock

Schedule of Preferred Stock

Prior to the IPO, the shares of Preferred Stock consisted of the following (in thousands, except share amounts):


		Preferred
	Preferred	shares			Common stock
	shares	issued and	Carrying		issuable upon
	authorized	outstanding	value		conversion
Series A Preferred Stock	137,814	137,814	$	0.014	1,604,574
Series B Preferred Stock	492,192	492,192		0.049	5,730,612
Series C Preferred Stock	693,500	693,500		0.069	8,074,447
Series D Preferred Stock	257,000	257,000		0.026	2,992,260
	1,580,506	1,580,506	$	0.158	18,401,893

As of December 31, 2018, the outstanding shares of Preferred Stock consisted of the following (in thousands, except share amounts):


		Preferred
	Preferred	shares			Common stock
	shares	issued and	Carrying		issuable upon
	authorized	outstanding	value		conversion
Series A Preferred Stock	137,814	137,814	$	0.014	1,604,574
Series B Preferred Stock	492,192	492,192		0.049	5,730,612
Series C Preferred Stock	693,500	693,500		0.069	8,074,447
	1,323,506	1,323,506	$	0.132	15,409,633

Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2019

Stock-based compensation

Schedule of assumptions used in the Black-Scholes option-pricing model for estimating the fair value of stock options


	Year ended December 31,
	2019		2018		2017

Risk-free interest rate	2.21	%	2.78	%	(0.67)	%
Expected term (in years)	6.1		5.1		2.8
Expected volatility	74.2	%	72.1	%	66.1	%
Expected dividends	—	%	—	%	—	%

Schedule of summary of stock option activity

The following table summarizes the Company’s stock option activity since January 1, 2019 (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, 2018	1,606,325	$	1.95	8.0	$	13,466
Granted	1,661,200		12.34
Exercised	(157,636)		0.10
Forfeited	(110,605)		6.72
Outstanding as of December 31, 2019	2,999,284	$	7.63	8.1	$	15,840

Options exercisable as of December 31, 2019	836,105	$	0.88	6.1	$	9,488
Options unvested as of December 31, 2019	2,163,179	$	10.23	8.9	$	6,352

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,
	2019		2018		2017

Research and development expenses	$	1,981	$	399	$	295
General and administrative expenses		3,584		468		475
	$	5,565	$	867	$	770

Income taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income taxes

Schedule of losses before income taxes

For financial reporting purposes, losses before income taxes for the years ended December 31, 2019, 2018 and 2017 consisted of the following (in thousands):


	Year ended December 31,
	2019		2018		2017
United States	$	(7,886)	$	(604)	$	(121)
Foreign (Austria)		(35,151)		(15,609)		(12,598)
Net loss before tax	$	(43,037)	$	(16,213)	$	(12,719)

Schedule of effective income tax rate reconciliation


	Year ended December 31,
	2019			2018			2017
U.S. federal statutory income tax rate		(21.0)	%		(21.0)	%		(35.0)	%
State income taxes, net of federal benefit		—			—			—
Foreign tax rate differential(1)		(4.0)			(4.0)			10.0
Not taxable government grants(2)		(5.4)			(7.5)			(3.0)
Stock-based compensation(3)		(0.3)			(4.6)			(3.5)
other		(0.3)			(0.5)			—
Change in deferred tax asset valuation allowance(4)		31.0			37.5			31.5
Effective income tax rate		—	%		(0.1)	%		—	%

(2) For the years ended December 31, 2019, 2018 and 2017, 5.4%, 7.5% and 3.0% increase, respectively, resulted from non-taxable research subsidies received from Austrian government agencies.

(3) For the years ended December 31, 2019, 2018 and 2017, 0.3% increase, 4.6% increase and 3.5% increase, respectively, resulted from non-taxable Stock-based compensation expense.

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, 2019 and 2018 consisted of the following (in thousands):


	Year ended December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	29,180	$	19,011
Credit carryforwards		180		—
Accrued expenses and other		669		94
Stock-based compensation		2,717		51
Operating lease liabilities		1,740		—
Other liabilities		132		—
Total deferred tax assets		34,618		19,156
Valuation allowance		(32,583)		(19,156)
Total deferred tax assets		2,035		—

Deferred tax liabilities:
Operating lease right of use asset		(1,808)		—
Finance lease right of use asset		(227)		—
Total deferred tax liabilities		(2,035)		—

Net deferred tax assets	$	—	$	—

Changes in the valuation allowance for deferred tax assets


	Year ended December 31,
	2019		2018		2017
Valuation allowance at beginning of period	$	(19,156)	$	(13,789)	$	(8,378)
Increases		(13,427)		(5,367)		(5,411)
Valuation allowance at end of period	$	(32,583)	$	(19,156)	$	(13,789)

Net loss per share (Tables)

12 Months Ended

Dec. 31, 2019

Net loss per share

Schedule of basic and diluted net loss per share


	Year ended December 31,
	2019		2018		2017

Numerator:
Net loss	$	(43,037)	$	(16,237)	$	(12,723)

Denominator:
Weighted-average common shares outstanding, basic and diluted		17,859,935		914,375		911,777

Net loss per share, basic and diluted	$	(2.41)	$	(17.76)	$	(13.95)

Schedule of potentially dilutive securities that were not included in the diluted per share calculations


	Year ended December 31,
	2019	2018	2017

Series A Preferred Stock	—	1,604,574	1,604,574
Series B Preferred Stock	—	5,730,612	5,730,612
Series C Preferred Stock	—	8,074,447	8,074,447
Series D Preferred Stock	—	—	—
Options issued and outstanding	2,999,284	1,606,325	1,434,150
Total	2,999,284	17,015,958	16,843,783

Selected Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Selected Quarterly Financial Information (Unaudited)

Schedule of selected quarterly financial information (unaudited)



	2019 Quarter Ended
	March 31,		June 30,		September 30,		December 31,
Revenue	$	2,235	$	4,051	$	2,038	$	3,618
Operating expenses		(12,890)		(17,680)		(15,614)		(16,843)
Net loss		(9,329)		(12,079)		(11,385)		(10,244)
Net loss per share - basic and diluted	$	(9.27)	$	(0.63)	$	(0.45)	$	(0.40)



	2018 Quarter Ended
	March 31,		June 30,		September 30,		December 31,
Revenue	$	—	$	649	$	1,900	$	5,080
Operating expenses		(6,449)		(7,624)		(7,452)		(7,284)
Net loss		(4,573)		(5,819)		(3,953)		(1,892)
Net loss per share - basic and diluted	$	(5.02)	$	(6.38)	$	(4.34)	$	(2.05)

Summary of significant accounting policies - Stock split and Transaction between entities under common control (Details)		1 Months Ended
	Apr. 05, 2019	Jun. 30, 2018 shares
Summary of significant accounting policies
Stock split ratio	11.643
Hookipa Biotech AG \| Common stock
Summary of significant accounting policies
Issuance of shares (in shares)		78,311
Hookipa Biotech AG \| Redeemable convertible preferred stock
Summary of significant accounting policies
Issuance of shares (in shares)		1,323,506

Summary of significant accounting policies - Going concern, Cash equivalents and Deferred offering costs (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of significant accounting policies
Net losses	$ 10,244	$ 11,385	$ 12,079	$ 9,329	$ 1,892	$ 3,953	$ 5,819	$ 4,573	$ 43,037	$ 16,237	$ 12,723
Accumulated deficit	$ 103,019				59,982				103,019	59,982
Cash equivalents					0					0
Offering costs									$ 9,400
Deferred offering costs					$ 1,400					$ 1,400

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Summary of significant accounting policies - Property and equipment (Details)	12 Months Ended
	Dec. 31, 2019
Leasehold improvements
Property and equipment
Estimated useful life	5 years
Laboratory equipment \| Minimum
Property and equipment
Estimated useful life	3 years
Laboratory equipment \| Maximum
Property and equipment
Estimated useful life	10 years
Furniture and fixtures \| Minimum
Property and equipment
Estimated useful life	3 years
Furniture and fixtures \| Maximum
Property and equipment
Estimated useful life	10 years
Computer equipment and software \| Minimum
Property and equipment
Estimated useful life	3 years
Computer equipment and software \| Maximum
Property and equipment
Estimated useful life	4 years

Summary of significant accounting policies - Leases and Revenue recognition from contracts with customers (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) item Program	Jan. 01, 2019 USD ($)
Summary of significant accounting policies
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
Operating lease assets	$ 7,875
Operating lease liability	$ 7,104
Adjustment \| ASU 2016-02
Summary of significant accounting policies
Operating lease assets		$ 3,300
Operating lease liability		$ 3,300

Summary of significant accounting policies - Comprehensive loss and Net loss per share (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of significant accounting policies
Foreign currency translation (loss)/gain		$ (0.9)	$ (2.4)	$ 1.8
Common stock
Summary of significant accounting policies
Shares issued upon conversion of redeemable convertible preferred stock (in shares)	14,582,161
Class A common stock
Summary of significant accounting policies
Shares issued upon conversion of redeemable convertible preferred stock (in shares)	3,819,732

Summary of significant accounting policies - Recent accounting pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2019
Summary of significant accounting policies
Lease, Practical Expedients, Package [true false]	true
Lease, Practical Expedient, Land Easement [true false]	true
Lease, Practical Expedient, Use of Hindsight [true false]	true
Operating lease assets		$ 7,875
Operating lease liability		$ 7,104
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Lessee, Finance Lease, Existence of Option to Extend [true false]	true
Lessee, Operating Lease, Existence of Option to Terminate [true false]	true
Lessee, Finance Lease, Existence of Option to Terminate [true false]	true
Adjustment \| ASU 2016-02
Summary of significant accounting policies
Operating lease assets	$ 3,300
Operating lease liability	$ 3,300

Collaboration and Licensing Agreements (Details) - Gilead Collaboration and License Agreement $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($) item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Collaboration and Licensing Agreements
Number of preclinical research programs \| item	2
Non-refundable, upfront payment	$ 10.0
Upfront payment recorded as revenue		$ 4.4	$ 2.8
Liability in deferred revenues		2.6
Prepayment received related to ordered manufacturing services		$ 1.0
Percentage of upfront payment included in deferred revenue expected to be recognized in 2020		97.00%
Percentage of upfront payment included in deferred revenue expected to be recognized in 2021		3.00%
Payment term (in days)		60 days
Revenue recognized from cost reimbursements		$ 4.3
Revenue recognized from milestone payments		3.2	2.0
Contract asset relating to the sublicense payment		0.4	0.3
Contract liability relating to sublicense payment			0.5
Development Milestones
Collaboration and Licensing Agreements
Total milestone amount		280.0
Commercial Milestones
Collaboration and Licensing Agreements
Total milestone amount		$ 100.0
Pre-clinical milestone
Collaboration and Licensing Agreements
Revenue recognized from milestone payments			$ 2.8

Fair Value of Financial Assets (Details) $ in Thousands	12 Months Ended
Fair Value of Financial Assets (Details) $ in Thousands	Dec. 31, 2019 USD ($)
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	35,132
Recurring \| Money market funds
Fair Value of Financial Assets
Cash equivalents	35,132
Recurring \| Level 1
Fair Value of Financial Assets
Total	35,132
Recurring \| Level 1 \| Money market funds
Fair Value of Financial Assets
Cash equivalents	$ 35,132

Property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and equipment
Property and equipment, gross	$ 10,174	$ 6,403
Less: Accumulated depreciation	(3,446)	(2,066)
Property and equipment, net	6,728	4,337
Depreciation expense	1,443	640	$ 398
Leasehold improvements
Property and equipment
Property and equipment, gross	1,919	1,885
Finance lease right of use assets
Property and equipment
Property and equipment, gross	1,967
Construction in progress
Property and equipment
Property and equipment, gross	286
Laboratory equipment
Property and equipment
Property and equipment, gross	4,555	3,443
Furniture and fixtures
Property and equipment
Property and equipment, gross	524	352
Computer equipment and software
Property and equipment
Property and equipment, gross	$ 923	$ 723

Leases (Details) $ in Thousands	12 Months Ended
Leases (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases
Cash balance maintained to secure a letter of credit associated with a real estate lease	$ 424
Presentation of leases in condensed consolidated balance sheets:
Operating lease assets	7,875
Finance lease assets, net	1,602
Total lease assets	9,477
Operating lease liabilities, current	1,814
Current finance lease liability	$ 159
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedExpensesAndOtherCurrentLiabilities
Total current lease liabilities	$ 1,973
Non-current operating lease liability	5,290
Non-current finance lease liability	$ 367
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Total non-current lease liabilities	$ 5,657
Total lease liabilities	7,630
Right-of-use asset derecognized	200
Lease liability derecognized	$ 200
Minimum
Leases
Remaining lease term (in years)	1 year
Maximum
Leases
Remaining lease term (in years)	4 years

Leases - Lease costs (Details) $ in Thousands	12 Months Ended
Leases - Lease costs (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases
Net lease expenses	$ 2,065
Research and Development Expense
Leases
Operating lease expenses	1,108
Finance lease amortization expenses	350
General and Administrative Expense
Leases
Operating lease expenses	712
Finance lease amortization expenses	14
Interest expenses
Leases
Interest on finance lease liabilities	9
Other income (expense)
Leases
Sublease income	$ (128)

Leases - Minimum lease payments (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Operating leases
2020	$ 1,826
2021	1,832
2022	1,830
2023	1,818
2024	128
Total lease payments	7,434
Less: interest	330
Present value of lease liabilities	7,104
Finance leases
2020	155
2021	138
2022	122
2023	120
2024	10
Total lease payments	545
Less: interest	19
Present value of lease liabilities	526
Total
2020	1,981
2021	1,970
2022	1,952
2023	1,938
2024	138
Total lease payments	7,979
Less: interest	349
Present value of lease liabilities	$ 7,630

Leases - Minimum rental commitments under non-cancelable leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Minimum rental commitments under non-cancelable leases
2019	$ 520
2020	278
2021	43
2022	43
2023	11
Total	895
Rent expense	$ 1,100	$ 600

Leases - Weighted average remaining lease term and weighted average discount rate (Details)	12 Months Ended
	Dec. 31, 2019
Leases
Operating lease, Weighted average remaining lease term (in years)	4 years 1 month 6 days
Operating lease, Weighted average discount rate	2.30%
Finance lease, Weighted average remaining lease term (in years)	3 years 10 months 24 days
Finance lease, Weighted average discount rate	1.70%
Sublease, remaining lease term (in years)	1 year 2 months 12 days

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued expenses and other current liabilities
Consulting fees	$ 724	$ 1,764
Salaries and bonuses	2,640	1,404
Social security contributions	177	121
Unearned grant income (current)	725	833
Loans	1,224
Invoices not yet received	2,673
Finance lease liabilities	159
Other accruals and liabilities	84	298
Total	$ 8,406	$ 4,420

Loans payable (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended							12 Months Ended
Loans payable (Details) - USD ($) $ in Thousands	Nov. 30, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans payable
Loans from FFG		$ 7,305				$ 8,316			$ 7,305	$ 8,316
Unamortized debt discount		(2,586)				(3,924)			(2,586)	(3,924)
Total Loans payable, net		4,719				4,392			4,719	4,392
Revenue		3,618	$ 2,038	$ 4,051	$ 2,235	5,080	$ 1,900	$ 649	11,942	7,629
Unearned income (current)		3,591				6,619			3,591	6,619
unearned income (non-current)		72				1,663			72	1,663
Unamortized debt discount		2,600				3,900			2,600	3,900
Interest expense									900	800	$ 600
Amortization of debt discount									800	700	500
Principal payment									$ 842	0
Estimated market rate									20.00%
Threshold for change in estimated market rate									0.10
Scheduled early repayment	$ 3,300
Adjustment
Loans payable
Deferred income reduced	$ 300
Grant
Loans payable
Revenue									$ 800	700	500
Unearned income (current)		700				800			700	800	700
unearned income (non-current)		$ 1,900				$ 3,000			$ 1,900	$ 3,000	$ 3,800
Minimum
Loans payable
Interest rate (as a percent)		0.75%							0.75%
Maximum
Loans payable
Interest rate (as a percent)		1.00%							1.00%

Loans payable - Schedule of aggregate minimum future principal payments (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
2020	$ 1,280
2022	3,029
2023	1,806
2024	1,190
Total	$ 7,305

Redeemable convertible preferred stock (Details) - USD ($)			1 Months Ended		3 Months Ended	12 Months Ended
	Apr. 23, 2019	Jan. 04, 2018	Feb. 28, 2019	Dec. 31, 2017	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Redeemable convertible preferred stock
Average price (in dollars per sale)						$ 12.23	$ 10.33
Issuance costs						$ 9,400,000
Amount reclassified upon conversion of Preferred Stock						$ 142,048,000
Preferred Stock outstanding (in shares)						0
Undesignated Preferred Stock authorized (in shares)						10,000,000
Preferred shares authorized (in shares)					1,580,506	0	1,323,506
Preferred shares issued and outstanding (in shares)					1,580,506	0	1,323,506
Carrying value (in dollars per sale)					$ 0.158		$ 0.132
Common stock issuable upon conversion (in shares)					18,401,893		15,409,633
IPO
Redeemable convertible preferred stock
Average price (in dollars per sale)						$ 14.00
Issuance costs						$ 9,386,000
Outstanding shares of Preferred Stock converted (in shares)	1,580,506
Amount reclassified upon conversion of Preferred Stock	$ 142,000,000
Common Stock \| IPO
Redeemable convertible preferred stock
Average price (in dollars per sale)	$ 14.00
Issuance costs	$ 9,400,000
Stock issued upon conversion of Preferred Stock (in shares)	14,582,161
Series A Preferred Stock
Redeemable convertible preferred stock
Preferred shares authorized (in shares)					137,814		137,814
Preferred shares issued and outstanding (in shares)					137,814		137,814
Carrying value (in dollars per sale)					$ 0.014		$ 0.014
Common stock issuable upon conversion (in shares)					1,604,574		1,604,574
Series B Preferred Stock
Redeemable convertible preferred stock
Preferred Stock issued (in shares)								82,032
Issuance costs								$ 0
Preferred shares authorized (in shares)					492,192		492,192
Preferred shares issued and outstanding (in shares)					492,192		492,192
Carrying value (in dollars per sale)					$ 0.049		$ 0.049
Common stock issuable upon conversion (in shares)					5,730,612		5,730,612
Series C Preferred Stock
Redeemable convertible preferred stock
Preferred Stock issued (in shares)				693,500				693,500
Average price (in dollars per sale)				$ 85.60				$ 85.60
Gross Proceeds from issuance of stock		$ 6,500,000		$ 59,400,000
Issuance costs		$ 100,000						$ 93,000
Preferred shares authorized (in shares)					693,500		693,500
Preferred shares issued and outstanding (in shares)					693,500		693,500
Carrying value (in dollars per sale)					$ 0.069		$ 0.069
Common stock issuable upon conversion (in shares)					8,074,447		8,074,447
Series D Preferred Stock
Redeemable convertible preferred stock
Preferred Stock issued (in shares)			257,000			257,000
Average price (in dollars per sale)			$ 145.65
Gross Proceeds from issuance of stock			$ 37,400,000
Issuance costs			$ 200,000
Preferred shares authorized (in shares)					257,000
Preferred shares issued and outstanding (in shares)					257,000
Carrying value (in dollars per sale)					$ 0.026
Common stock issuable upon conversion (in shares)					2,992,260
Class A common stock
Redeemable convertible preferred stock
Number of common stock issued upon conversion of each share of Preferred Stock						11.643
Class A common stock \| IPO
Redeemable convertible preferred stock
Stock issued upon conversion of Preferred Stock (in shares)	3,819,732
Class A common stock \| Common Stock
Redeemable convertible preferred stock
Stock issued upon conversion of Preferred Stock (in shares)						3,819,732

Common stock and Class A common stock (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 23, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 $ / shares shares
Share Price \| $ / shares		$ 12.23	$ 10.33
Offering costs \| $		$ 9,400
Number of votes \| Vote		1
Common stock
Common stock, issued (in shares)		21,746,392	1,006,595
Common stock, outstanding (in shares)		21,746,392	1,006,595
Common stock, shares authorized		100,000,000	18,454,860
Class A common stock
Common stock, issued (in shares)		3,819,732	0
Common stock, outstanding (in shares)		3,819,732	0
Common stock, shares authorized		3,900,000	0
Number of common stock issued upon conversion of each share		1
Common Stock \| Common stock
Issuance of common stock upon initial public offering		6,000,000
Stock issued upon conversion of Preferred Stock (in shares)		14,582,161
Common Stock \| Class A common stock
Stock issued upon conversion of Preferred Stock (in shares)		3,819,732
IPO
Share Price \| $ / shares		$ 14.00
Offering costs \| $		$ 9,386
IPO \| Common stock
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 upon initial public offering	6,000,000
Share Price \| $ / shares	$ 14.00
Proceeds from Issuance Initial Public Offering \| $	$ 74,600
Offering costs \| $	$ 9,400
Stock issued upon conversion of Preferred Stock (in shares)	14,582,161

Stock-based compensation - 2018 Stock Option and Grant Plan (Details)	12 Months Ended
	Dec. 31, 2019 installment shares	Dec. 31, 2018 € / shares shares	Dec. 31, 2017 shares
Stock-based compensation
Issuance of common stock upon exercise of stock options (in shares)	157,636		0
Number of shares granted to US employee	1,661,200
Options outstanding	2,999,284	1,606,325
2018 Stock Option and Grant Plan
Stock-based compensation
Options outstanding	1,357,764
Vesting period	4 years
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
Number of shares granted to US employee		2.93

Stock-based compensation - 2019 Stock Option and Incentive Plan (Details)		12 Months Ended
	Apr. 01, 2019 installment shares	Dec. 31, 2019
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	2,608,042
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 - Stock option valuation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assumptions used in the Black-Scholes option-pricing model
Risk-free interest rate	2.21	2.78	(0.67)
Expected term (in years)	6 years 1 month 6 days	5 years 1 month 6 days	2 years 9 months 18 days
Expected volatility	74.20%	72.10%	66.10%

Stock-based compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Beginning balance	1,606,325
Granted	1,661,200
Exercised	(157,636)		0
Forfeited	(110,605)
Ending balance	2,999,284	1,606,325
Option exercisable	836,105
Option unvested	2,163,179
Weighted Averaged Exercise Price
Beginning balance	$ 1.95
Granted	12.34
Exercised	0.10
Forfeited	6.72
Ending balance	7.63	$ 1.95
Option exercisable	0.88
Option unvested	$ 10.23
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	8 years 1 month 6 days	8 years
Weighted Average Remaining Contractual Term, option exercisable	6 years 1 month 6 days
Weighted Average Remaining Contractual Term, option unvested	8 years 10 months 24 days
Aggregate Intrinsic Value, beginning balance	$ 13,466
Aggregate Intrinsic Value, ending balance	15,840	$ 13,466
Aggregate Intrinsic Value, option unvested	6,352
Aggregate Intrinsic Value, option exercisable	$ 9,488
Average price (in dollars per sale)	$ 12.23	$ 10.33
Aggregate Intrinsic Value, options exercised	$ 1,400	$ 1,000
Weighted average grant-date fair value per share of stock options granted	$ 7.92	$ 2.55
Cash received from option exercise under share-based payment arrangements	$ 16	$ 9	$ 0

Stock-based compensation - Stock-based compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-based compensation
Stock-based compensation expense	$ 5,565	$ 867	$ 770
Number of outstanding options modified		2,000
Exercise price of the stock options		$ 34.12	$ 1.17
Unrecognized compensation cost related to the unvested stock-based awards	$ 9,300	$ 2,200
Weighted average periods over which expense is expected to be recognized	1 year 9 months 18 days	1 year 8 months 12 days
Research and Development Expense
Stock-based compensation
Stock-based compensation expense	$ 1,981	$ 399	$ 295
General and Administrative Expense
Stock-based compensation
Stock-based compensation expense	$ 3,584	$ 468	$ 475

Income taxes (Details) - USD ($)	12 Months Ended
Income taxes (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income taxes
Income tax benefits for the net operating losses incurred	$ 0	$ 0	$ 0
Unrecognized income tax benefits	$ 0

Income taxes - Losses before income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income taxes
United States	$ (7,886)	$ (604)	$ (121)
Foreign (Austria)	(35,151)	(15,609)	(12,598)
Net loss before tax	$ (43,037)	$ (16,213)	$ (12,719)
Company's worldwide effective tax rate	0.00%	(0.10%)	0.00%

Income taxes - Effective income tax reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
U.S. federal statutory income tax rate	(21.00%)	(21.00%)	(35.00%)
Foreign tax rate differential	(4.00%)	(4.00%)	10.00%
Not taxable government grants	(5.40%)	(7.50%)	(3.00%)
Stock-based compensation	(0.30%)	(4.60%)	(3.50%)
Other	(0.30%)	(0.50%)
Change in deferred tax asset valuation allowance	31.00%	37.50%	31.50%
Effective income tax rate	0.00%	(0.10%)	0.00%
Austria
Operating Loss Carryforwards [Line Items]
U.S. federal statutory income tax rate	(25.00%)

Income taxes - Components of the net deferred tax assets or liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 29,180	$ 19,011
Credit carryforwards	180
Accrued expenses and other	669	94
Stock-based compensation	2,717	51
Operating lease liabilities	1,740
Other liabilities	132
Total deferred tax assets	34,618	19,156
Valuation allowance	(32,583)	$ (19,156)	$ (13,789)	$ (8,378)
Total deferred tax assets	2,035
Deferred tax liabilities:
Operating lease right of use asset	(1,808)
Finance lease right of use asset	(227)
Total deferred tax liabilities	$ (2,035)

Income taxes - Changes in the valuation allowance for deferred tax assets and others (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2026	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income taxes
Net operating loss carryforwards		$ 112,300	$ 76,000	$ 55,200
Valuation allowance at beginning of period		(19,156)	(13,789)	(8,378)
Increases		(13,427)	(5,367)	(5,411)
Valuation allowance at end of period		$ (32,583)	$ (19,156)	$ (13,789)
Statutory corporate tax rate		21.00%	21.00%	35.00%
Tax rate applied on undistributed earnings in the form of cash and cash equivalents		15.50%
Tax rate applied on other earnings		8.00%
Tax payable term (in years)		8 years
Threshold return percentage of GILIT		10.00%
Reduction percentage of inclusion for GILTI		50.00%
Percentage of inclusion for GILTI	37.50%

Commitments and contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commitments and contingencies
Non-cancellable obligations	$ 13.1	$ 13.9
2020 deliverables	10.2
2021 deliverables	2.9
2022 deliverables	0.0
Licensing fees from intellectual property licenses	$ 1.9	$ 0.1

401(k) Savings Plan (Details) - Maximum	12 Months Ended
401(k) Savings Plan (Details) - Maximum	Dec. 31, 2019
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) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss	$ (10,244)	$ (11,385)	$ (12,079)	$ (9,329)	$ (1,892)	$ (3,953)	$ (5,819)	$ (4,573)	$ (43,037)	$ (16,237)	$ (12,723)
Denominator:
Weighted-average common shares outstanding, basic and diluted									17,859,935	914,375	911,777
Net loss per share, basic and diluted	$ (0.40)	$ (0.45)	$ (0.63)	$ (9.27)	$ (2.05)	$ (4.34)	$ (6.38)	$ (5.02)	$ (2.41)	$ (17.76)	$ (13.95)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net loss per share - Antidilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Anti-dilutive securities
Anti-dilutive shares	2,999,284	17,015,958	16,843,783
Series A Preferred Stock
Anti-dilutive securities
Anti-dilutive shares		1,604,574	1,604,574
Series B Preferred Stock
Anti-dilutive securities
Anti-dilutive shares		5,730,612	5,730,612
Series C Preferred Stock
Anti-dilutive securities
Anti-dilutive shares		8,074,447	8,074,447
Options
Anti-dilutive securities
Anti-dilutive shares	2,999,284	1,606,325	1,434,150

Related parties (Details) - USD ($) $ in Thousands	12 Months Ended
Related parties (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related parties
Shares issued		0
Due from shareholder for issuance of redeemable convertible preferred stock			$ 6,520
Series D Preferred Stock
Related parties
Shares issued	50,670
Proceeds from shares issued	$ 7,400
Common stock
Related parties
Shares issued	1,303,750
Proceeds from shares issued	$ 18,300
Series B Preferred Stock
Related parties
Shares issued			61,524
Proceeds from shares issued			$ 4,000
Series C Preferred Stock
Related parties
Shares issued			147,712
Proceeds from shares issued			$ 12,600
University of Basel
Related parties
Research and development expenses	300	$ 400	300
Royalties paid	$ 0	$ 0	$ 0

Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Selected Quarterly Financial Information (Unaudited)
Revenue	$ 3,618	$ 2,038	$ 4,051	$ 2,235	$ 5,080	$ 1,900	$ 649		$ 11,942	$ 7,629
Operating expenses	(16,843)	(15,614)	(17,680)	(12,890)	(7,284)	(7,452)	(7,624)	$ (6,449)
Net loss	$ (10,244)	$ (11,385)	$ (12,079)	$ (9,329)	$ (1,892)	$ (3,953)	$ (5,819)	$ (4,573)	$ (43,037)	$ (16,237)	$ (12,723)
Net loss per share—basic and diluted	$ (0.40)	$ (0.45)	$ (0.63)	$ (9.27)	$ (2.05)	$ (4.34)	$ (6.38)	$ (5.02)	$ (2.41)	$ (17.76)	$ (13.95)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details