Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Aug. 12, 2019
Document And Entity Information Abstract
Entity Registrant Name	HOOKIPA Pharma Inc.
Entity Central Index Key	0001760542
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		21,588,756
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 134,893	$ 48,580
Accounts receivable	3,256	4,919
Prepaid expenses and other current assets	12,951	8,812
Total current assets	151,100	62,311
Non-current assets:
Restricted cash	320
Property and equipment, net	4,579	4,337
Operating lease assets	8,909
Other non-current assets	3,187	1,603
Total non-current assets	16,995	5,940
Total assets	168,095	68,251
Current liabilities
Accounts payable	5,095	3,656
Deferred revenues	5,225	6,619
Accrued expenses and other current liabilities	7,063	4,420
Total current liabilities	17,383	14,695
Non-current liabilities
Loans payable, non-current	4,754	4,392
Operating lease liabilities, non-current	6,177
Deferred revenues, non-current	715	1,663
Other non-current liabilities	3,033	3,102
Total non-current liabilities	14,679	9,157
Total liabilities	32,062	23,852
Commitments and contingencies (Note 11)
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 June 30, 2019 and December 31, 2018, respectively; aggregate liquidation preference of $0.0 million and $99.7 million at June 30, 2019 and December 31, 2018, respectively		104,774
Stockholders’ equity (deficit):
Common stock value	3	0
Undesignated preferred stock, $0.0001 par value; 10,000,000 shares and 0 shares authorized at June 30, 2019 and December 31, 2018, respectively; 0 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively
Additional paid-in capital	221,576	3,327
Accumulated other comprehensive loss	(4,156)	(3,720)
Accumulated deficit	(81,390)	(59,982)
Total stockholders’ equity (deficit)	136,033	(60,375)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	168,095	$ 68,251
Class A common stock
Stockholders’ equity (deficit):
Common stock value	$ 0

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Jun. 30, 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, liquidation preference	$ 0.0	$ 99.7
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	21,588,756	1,006,595
Common stock, shares outstanding	21,588,756	1,006,595
Undesignated preferred stock, par value	$ 0.0001	$ 0.0001
Undesignated preferred stock, shares authorized	10,000,000	0
Undesignated preferred stock, shares issued	0	0
Undesignated preferred stock, shares outstanding	0	0
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

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue from collaboration and licensing	$ 4,051	$ 649	$ 6,286	$ 649
Operating expenses:
Research and development	(13,929)	(6,211)	(24,108)	(11,180)
General and administrative	(3,751)	(1,413)	(6,462)	(2,893)
Total operating expenses	(17,680)	(7,624)	(30,570)	(14,073)
Loss from operations	(13,629)	(6,975)	(24,284)	(13,424)
Other income (expense):
Grant income	1,544	1,384	2,736	3,455
Interest income	511	0	575	0
Interest expense	(210)	(191)	(423)	(384)
Other income and expenses, net	(195)	(36)	88	(14)
Total other income (expense), net	1,650	1,157	2,976	3,057
Net loss before tax	(11,979)	(5,818)	(21,308)	(10,367)
Income tax expense	(100)	(1)	(100)	(25)
Net loss	(12,079)	(5,819)	(21,408)	(10,392)
Other comprehensive loss:
Foreign currency translation gain (loss), net of tax	300	(3,018)	(435)	(1,479)
Comprehensive loss	$ (11,779)	$ (8,837)	$ (21,843)	$ (11,871)
Net loss per share—basic and diluted	$ (0.63)	$ (6.38)	$ (2.10)	$ (11.40)
Weighted average common shares outstanding — basic and diluted	19,240,977	911,777	10,174,157	911,777

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ DEFICIT - USD ($) $ in Thousands	Common Stock Class A common stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balance at the beginning of the period at Dec. 31, 2017						$ 104,774
Balance at the beginning of the period (in shares) at Dec. 31, 2017						1,323,506
Balance at the end of the period at Mar. 31, 2018						$ 104,774
Balance at the end of the period (in shares) at Mar. 31, 2018						1,323,506
Balance at the beginning of the period at Dec. 31, 2017		$ 0	$ 2,451	$ (1,362)	$ (43,745)	$ (42,656)
Balance at the beginning of the period (in shares) at Dec. 31, 2017		911,777
Increase (Decrease) in Stockholders' Equity
Foreign currency translation adjustment, net of tax				1,539		1,539
Stock-based compensation expense			206			206
Net loss					(4,573)	(4,573)
Balance at the end of the period at Mar. 31, 2018		$ 0	2,657	177	(48,318)	(45,484)
Balance at the end of the period (in shares) at Mar. 31, 2018		911,777
Balance at the beginning of the period at Dec. 31, 2017						$ 104,774
Balance at the beginning of the period (in shares) at Dec. 31, 2017						1,323,506
Balance at the end of the period at Jun. 30, 2018						$ 104,774
Balance at the end of the period (in shares) at Jun. 30, 2018						1,323,506
Balance at the beginning of the period at Dec. 31, 2017		$ 0	2,451	(1,362)	(43,745)	$ (42,656)
Balance at the beginning of the period (in shares) at Dec. 31, 2017		911,777
Increase (Decrease) in Stockholders' Equity
Foreign currency translation adjustment, net of tax						(1,479)
Net loss						(10,392)
Balance at the end of the period at Jun. 30, 2018		$ 0	2,863	(2,841)	(54,137)	(54,115)
Balance at the end of the period (in shares) at Jun. 30, 2018		911,777
Balance at the beginning of the period at Mar. 31, 2018						$ 104,774
Balance at the beginning of the period (in shares) at Mar. 31, 2018						1,323,506
Balance at the end of the period at Jun. 30, 2018						$ 104,774
Balance at the end of the period (in shares) at Jun. 30, 2018						1,323,506
Balance at the beginning of the period at Mar. 31, 2018		$ 0	2,657	177	(48,318)	$ (45,484)
Balance at the beginning of the period (in shares) at Mar. 31, 2018		911,777
Increase (Decrease) in Stockholders' Equity
Foreign currency translation adjustment, net of tax		$ 0		(3,018)		(3,018)
Stock-based compensation expense			206			206
Net loss					(5,819)	(5,819)
Balance at the end of the period at Jun. 30, 2018		$ 0	2,863	(2,841)	(54,137)	(54,115)
Balance at the end of the period (in shares) at Jun. 30, 2018		911,777
Balance at the beginning of the period at Dec. 31, 2018						$ 104,774
Balance at the beginning of the period (in shares) at Dec. 31, 2018						1,323,506
Increase (Decrease) in Temporary Equity
Issuance of Series D preferred stock, net of issuance costs of $158						$ 37,274
Issuance of Series D preferred stock, net of issuance costs of $158 (in shares)						257,000
Balance at the end of the period at Mar. 31, 2019						$ 142,048
Balance at the end of the period (in shares) at Mar. 31, 2019						1,580,506
Balance at the beginning of the period at Dec. 31, 2018		$ 0	3,327	(3,720)	(59,982)	$ (60,375)
Balance at the beginning of the period (in shares) at Dec. 31, 2018		1,006,595
Increase (Decrease) in Stockholders' Equity
Foreign currency translation adjustment, net of tax				(736)		(736)
Stock-based compensation expense			383			383
Net loss					(9,329)	(9,329)
Balance at the end of the period at Mar. 31, 2019		$ 0	3,710	(4,456)	(69,311)	(70,057)
Balance at the end of the period (in shares) at Mar. 31, 2019		1,006,595
Balance at the beginning of the period at Dec. 31, 2018						$ 104,774
Balance at the beginning of the period (in shares) at Dec. 31, 2018						1,323,506
Balance at the end of the period (in shares) at Jun. 30, 2019						0
Balance at the beginning of the period at Dec. 31, 2018		$ 0	3,327	(3,720)	(59,982)	$ (60,375)
Balance at the beginning of the period (in shares) at Dec. 31, 2018		1,006,595
Increase (Decrease) in Stockholders' Equity
Foreign currency translation adjustment, net of tax						(435)
Net loss						(21,408)
Balance at the end of the period at Jun. 30, 2019	$ 0	$ 3	221,576	(4,156)	(81,390)	136,033
Balance at the end of the period (in shares) at Jun. 30, 2019	3,819,732	21,588,756
Balance at the beginning of the period at Mar. 31, 2019						$ 142,048
Balance at the beginning of the period (in shares) at Mar. 31, 2019						1,580,506
Increase (Decrease) in Temporary Equity
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 Jun. 30, 2019						0
Balance at the beginning of the period at Mar. 31, 2019		$ 0	3,710	(4,456)	(69,311)	$ (70,057)
Balance at the beginning of the period (in shares) at Mar. 31, 2019		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	$ 0	$ 2	142,046			142,048
Conversion of Series A, B, C and D preferred stock into common stock upon initial public offering(in shares)	3,819,732	14,582,161
Foreign currency translation adjustment, net of tax				300		300
Stock-based compensation expense			1,206			1,206
Net loss					(12,079)	(12,079)
Balance at the end of the period at Jun. 30, 2019	$ 0	$ 3	$ 221,576	$ (4,156)	$ (81,390)	$ 136,033
Balance at the end of the period (in shares) at Jun. 30, 2019	3,819,732	21,588,756

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ DEFICIT (Parenthetical) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares
Issuance costs	$ 9,400
Share price \| $ / shares	$ 6.73
IPO
Issuance costs	$ 9,386
Share price \| $ / shares	$ 14.00
Series D convertible preferred stock
Issuance costs	$ 158

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss	$ (21,408)	$ (10,392)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,589	411
Depreciation expense	1,405	291
Other non-cash items	51	5
Changes in operating assets and liabilities:
Accounts receivable	1,892	(149)
Prepaid expenses and other current assets	(5,575)	(2,352)
Other non-current assets	(6,170)	(15)
Accounts payable	994	414
Deferred revenues	(2,265)	9,943
Accrued expenses and other liabilities	2,452	389
Other non-current liabilities	3,582
Net cash used in operating activities	(23,453)	(1,455)
Investing activities:
Purchases of property and equipment	(591)	(1,620)
Net cash used in investing activities	(591)	(1,620)
Financing activities:
Payments related to finance leases	(1,406)
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	37,274	6,439
Proceeds from issuance of common stock, net of issuance costs	75,298
Proceeds from borrowings		433
Net cash provided by financing activities	111,166	6,872
Net increase in cash, cash equivalents and restricted cash	87,122	3,797
Cash, cash equivalents and restricted cash at beginning of period	48,580	61,362
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(489)	(1,799)
Cash, cash equivalents and restricted cash at end of period	135,213	63,360
Supplemental disclosure of cash flow information:
Cash paid for interest	(32)
Cash paid for income taxes	$ (100)	$ (25)

Nature of the business and organization	6 Months Ended
Nature of the business and organization	Jun. 30, 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

6 Months Ended

Jun. 30, 2019

Summary of significant accounting policies

Summary of significant accounting policies

2. Summary of significant accounting policies

Basis of presentation

The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation.

The accompanying condensed consolidated balance sheets as of June 30, 2019, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018, the condensed consolidated statements of cash flows for the six months ended June 30, 2019 and 2018, and the condensed consolidated statement of redeemable convertible preferred stock and stockholders’ deficit for the three and six months ended June 30, 2019 and 2018 are unaudited.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements, except for the accounting of lease agreements that have been reported in accordance with ASC 842 and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement for interim reporting. Certain information and footnote disclosures typically included in annual financial statements prepared in accordance with GAAP have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements as of and for the year ended December 31, 2018, which are included in the Company’s prospectus related to the Company’s IPO, filed April 19, 2019 (File No. 333-230451) with the Securities and Exchange Commission (“SEC”), pursuant to Rule 424 (b) under the Securities Act of 1933, as amended. The results for any interim period are not necessarily indicative of results for any future period.

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 condensed 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 7) have been adjusted proportionally.

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 June 30, 2019, the Company has funded its operations with proceeds from sales of common stock in the IPO, 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 $21.4 million and $10.4 million for the six months ended June 30, 2019 and 2018, respectively. As of June 30, 2019, the Company had an accumulated deficit of $81.4 million. The Company expects to continue to generate operating losses in the foreseeable future. As of August 12, 2019, the filing date of this Quarterly Report on Form 10‑Q, 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 condensed 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 condensed 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 condensed 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 condensed consolidated financial statements include, but are not limited to, the recognition of revenue and income, the accrual of research and development expenses, 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.

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 six months ended June 30, 2019 have been deposited in interest-bearing bank accounts with investment grade US financial institutions. As of December 31, 2018 and June 30, 2019, the Company’s cash and cash equivalents included substantial amounts of cash balances held in euros on accounts with European banks. 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.

Deferred offering costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs 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 condensed consolidated statements of operations and comprehensive loss. Total offering costs of $9.4 million recorded in stockholders’ equity in the six month ended June 30, 2019 included $1.4 million of cost incurred in previous periods, which were initially recorded as deferred offering costs as of December 31, 2018.

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 economic useful lives of the leasehold improvements were adjusted to the lease terms.

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.

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.

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 condensed consolidated balance sheets and to recognize those lease payments on a straight-line basis in the condensed 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 condensed consolidated balance sheets. The adoption of the new leasing standards did not have an impact on the Company’s condensed 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 condensed 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 condensed consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term.

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 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 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. The new standard will be effective 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 is currently evaluating the impact that the adoption of ASU 2018‑15 will have on its consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses. The standard modifies the impairment model for most financial assets, including trade accounts receivables and loans, and will require the use of an “expected loss” model for instruments measured at amortized cost. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The effective date of the standard is for fiscal years beginning after December 15, 2019 with early adoption permitted. In May 2019, the FASB issued ASU 2019-05, Financial Instruments-Credit Losses, to allow entities to irrevocably elect the fair value option for certain financial assets previously measured at amortized cost upon adoption of the new credit losses standard. The new effective dates and transition align with those of ASU 2016-13. The Company is currently evaluating the potential impact of the adoption of these updates on its consolidated financial statements.

Collaboration and Licensing Agreements	6 Months Ended
Collaboration and Licensing Agreements	Jun. 30, 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 $1.4 million and $2.3 million, respectively was recorded as revenue from collaboration and licensing in the three months and six months ended June 30, 2019 and $4.9 million was included as a liability in deferred revenues, current and non-current, as of June 30, 2019. Approximately 73% of the upfront payment included in deferred revenue as of June 30, 2019 is expected to be recognized in the remainder of 2019, 25% in 2020 and the remaining 2% 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 $1.4 million recognition of the upfront payment, the Company recognized $0.7 million revenue from cost reimbursements for research and development services and $2.0 million in milestone payments in the three months ended June 30, 2019. In the six months ended June 30, 2019, the Company recognized $2.0 million revenue from cost reimbursements for research and development services and $2.0 million in milestone payments. For the three and six months ended June 30, 2018, revenue from reimbursement of research and development expenses was $0.2 million and revenue from partial recognition of the upfront payment was $0.4 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 June 30, 2019 and December 31, 2018, the contract asset relating to the sublicense payment was $0.5 million and $0.4 million, respectively.

Leases

6 Months Ended

Jun. 30, 2019

Leases

Leases

4. 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 2 years to 5 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 $0.3 million to secure a letter of credit associated with a real estate lease. This amount was classified as non-current restricted cash in the consolidated balance sheet as of June 30, 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 condensed consolidated balance sheets:


		June 30,
	Balance sheet location	2019
Assets
Operating lease assets	Operating lease assets	$	8,909
Finance lease assets	Other non-current assets		1,803
Total lease assets			10,712
Liabilities
Current operating lease liability	Accrued expenses and other current liabilities		1,786
Current finance lease liability	Accrued expenses and other current liabilities		147
Total current lease liabilities			1,933
Non-current operating lease liability	Operating lease liabilities, non-current		6,177
Non-current finance lease liability	Other non-current liabilities		432
Total non-current lease liabilities			6,609
Total lease liabilities		$	8,542

In the six months ended June 30, 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 condensed consolidated statements of operations and comprehensive loss:


		Three months ended		Six months ended
	Income statement location	June 30, 2019		June 30, 2019
Operating lease expenses	Research and development expenses	$	296	$	498
	General and administrative expenses		199		310
Finance lease amortization expenses	Research and development expenses		95		158
	General and administrative expenses		4		6
Interest on finance lease liabilities	Interest expenses		3		4
Sublease income	Other income (expense)		(39)		(46)
Net lease expense		$	558	$	930

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


	June 30, 2019
	Operating lease		Finance lease		Total
2019 (remaining six months)	$	865	$	72	$	937
2020		1,847		143		1,990
2021		1,853		131		1,984
2022		1,851		123		1,974
2023		1,839		121		1,960
2024		128		10		138
Thereafter		—		—		—
Total lease payments		8,383		600		8,983
Less: interest		418		23		441
Present value of lease liabilities	$	7,965	$	577	$	8,542

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

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

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


	June 30,
	2019

Weighted average remaining lease term in years	4.6
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:


	June 30,
	2019

Weighted average remaining lease term in years	4.4
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 1.7 years without an option to renew and has been qualified as an operating lease. The Company recognizes sublease income as incurred in its condensed consolidated statements of operations and comprehensive loss. The Company continued to account for the head lease as it did before sublease commencement.

Supplemental disclosure of cash flow information related to our operating and finance leases included in cash flows provided by operating activities in our condensed consolidated statements of cash flows is as follows:


	Six months ended
	June 30, 2019

Cash paid for amounts included in the measurement of operating lease liabilities (1)	$	1,725
Cash paid for amounts included in the measurement of finance lease liabilities (1)		1,391
Operating lease assets obtained in exchange for lease obligations (2)		5,557
Finance lease assets obtained in exchange for lease obligations (2)		634

(1)

The cash paid for amounts included in the measurement of lease liabilities includes upfront payments.

(2)

The lease assets reported in the cash flow information exclude upfront payments.

Accrued expenses and other current liabilities

6 Months Ended

Jun. 30, 2019

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities

5. Accrued expenses and other current liabilities

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


	June 30,		December 31,
	2019		2018

Consulting fees	$	1,213	$	1,764
Salaries and bonuses		1,098		1,404
Social security contributions		232		121
Unearned grant income (current)		907		833
Operating lease liabilities		1,786		—
Finance lease liabilities		147		—
Other accruals and liabilities		1,680		298
Total	$	7,063	$	4,420

Loans payable

6 Months Ended

Jun. 30, 2019

Loans payable

Loans payable

6. Loans payable

As of June 30, 2019 and December 31, 2018, loans payable consisted of the following (in thousands):


	June 30,		December 31,
	2019		2018

Loans from FFG	$	8,256	$	8,316
Unamortized debt discount		(3,502)		(3,924)
Total Loans payable, net	$	4,754	$	4,392

In connection with the funding agreements with the Austrian Research Promotion Agency, (Österreichische Forschungs- förderungsgesellschaft, 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 2021 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.

Redeemable convertible preferred stock

6 Months Ended

Jun. 30, 2019

Redeemable convertible preferred stock

Redeemable convertible preferred stock

7. 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 June 30, 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	6 Months Ended
Common stock and Class A common stock	Jun. 30, 2019
Common stock and Class A common stock
Common stock and Class A common stock	8. 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 condensed 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 June 30, 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 21,588,756 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

6 Months Ended

Jun. 30, 2019

Stock-based compensation

Stock-based compensation

9. 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 condensed 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. As of June 30, 2019, 1,538,987 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. Options granted to non-executive directors generally vest over a three-year term with 25% of the options vesting upon the first anniversary of the grant date and the remaining 75% of the options vesting in eight equal quarterly installments following the first anniversary of the grant date.

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


	Three months ended June 30,			Six months ended June 30,
	2019		2018	2019		2018

Risk-free interest rate	2.45	%	—	2.45	%	—
Expected term (in years)	6.1		—	6.1		—
Expected volatility	73.5	%	—	73.5	%	—
Expected dividends	—		—	—		—

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. In the three and six months ended June 30, 2018 the Company did not issue any stock options.

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	1,070,896		14.00
Exercised	—		—
Forfeited	(84,266)		6.81
Outstanding as of June 30, 2019	2,592,955	$	6.77	8.5	$	8,472

Options exercisable as of June 30, 2019	814,494	$	0.13	7.6	$	5,375
Options unvested as of June 30, 2019	1,778,461	$	9.80	8.9	$	3,097

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 June 30, 2019 and December 31, 2018, was $6.73 and $10.33, respectively.

No cash from option exercise was received in the six months ended June 30, 2019 and 2018, respectively.

Stock-based compensation

Stock-based compensation expense was classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):


	Three months ended June 30,				Six months ended June 30,
	2019		2018		2019		2018

Research and development expenses	$	401	$	93	$	662	$	186
General and administrative expenses		805		113		927		225
	$	1,206	$	206	$	1,589	$	411

Income taxes	6 Months Ended
Income taxes	Jun. 30, 2019
Income taxes
Income taxes	10. Income taxes Income tax expense during the three and six months ended June 30, 2018 and 2019 resulted from minimum tax obligations. During the three and six months ended June 30, 2018 and 2019, the Company recorded no income tax benefits for the net operating losses incurred, 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. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets resulting from its net operating loss carryforwards. 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 June 30, 2019 and December 31, 2018. Management reevaluates the positive and negative evidence at each reporting period.

Commitments and contingencies	6 Months Ended
Commitments and contingencies	Jun. 30, 2019
Commitments and contingencies
Commitments and contingencies	11. 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 June 30, 2019, the Company’s total non-cancellable obligations under contracts with CMOs, excluding embedded lease liabilities, were $15.9 million, of which $6.1 million relate to 2019 (remaining six months) deliverables $7.7 million relate to 2020 deliverables and $2.1 million relate to 2021 deliverables. 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 three and six months ended June 30, 2019, the Company recorded $0.1 million and $0.3 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 condensed consolidated financial statements as of June 30, 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.

Net loss per share

6 Months Ended

Jun. 30, 2019

Net loss per share

Net loss per share

12. 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):


	Three months ended June 30,				Six months ended June 30,
	2019		2018		2019		2018

Numerator:
Net loss	$	(12,079)	$	(5,819)	$	(21,408)	$	(10,392)

Denominator:
Weighted-average common shares outstanding, basic and diluted		19,240,977		911,777		10,174,157		911,777

Net loss per share, basic and diluted	$	(0.63)	$	(6.38)	$	(2.10)	$	(11.40)

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 as of June 30 that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	Three and six months ended June 30,
	2019	2018

Series A Preferred Stock	—	1,604,574
Series B Preferred Stock	—	5,730,612
Series C Preferred Stock	—	8,074,447
Series D Preferred Stock	—	—
Options issued and outstanding	2,592,955	1,428,191
Total	2,592,955	16,837,824

Related parties	6 Months Ended
Related parties	Jun. 30, 2019
Related parties
Related parties	13. 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 six months ended June 30, 2019 and 2018, the Company recorded $0.3 million and $0.3 million, respectively, in research and development expenses for service fees paid to the University of Basel. 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 six months ended June 30, 2019 and 2018, no royalties were paid pursuant to the terms of this arrangement. During the six months ended June 30, 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.

Summary of significant accounting policies (Policies)

6 Months Ended

Jun. 30, 2019

Summary of significant accounting policies

Basis of presentation

Stock split

Going concern

Use of estimates

Concentrations of credit risk and of significant suppliers

Deferred offering costs

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 economic useful lives of the leasehold improvements were adjusted to the lease terms.

Redeemable convertible preferred stock

Recent accounting pronouncements

Adopted as of current period

Recently Issued Accounting Pronouncements

Summary of significant accounting policies (Tables)

6 Months Ended

Jun. 30, 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 economic useful lives of the leasehold improvements were adjusted to the lease terms.

Leases (Tables)

6 Months Ended

Jun. 30, 2019

Leases

Schedule of operating and finance leases


		June 30,
	Balance sheet location	2019
Assets
Operating lease assets	Operating lease assets	$	8,909
Finance lease assets	Other non-current assets		1,803
Total lease assets			10,712
Liabilities
Current operating lease liability	Accrued expenses and other current liabilities		1,786
Current finance lease liability	Accrued expenses and other current liabilities		147
Total current lease liabilities			1,933
Non-current operating lease liability	Operating lease liabilities, non-current		6,177
Non-current finance lease liability	Other non-current liabilities		432
Total non-current lease liabilities			6,609
Total lease liabilities		$	8,542

Summary of the effect of lease costs


		Three months ended		Six months ended
	Income statement location	June 30, 2019		June 30, 2019
Operating lease expenses	Research and development expenses	$	296	$	498
	General and administrative expenses		199		310
Finance lease amortization expenses	Research and development expenses		95		158
	General and administrative expenses		4		6
Interest on finance lease liabilities	Interest expenses		3		4
Sublease income	Other income (expense)		(39)		(46)
Net lease expense		$	558	$	930

Summary of maturities of operating lease liabilities


	June 30, 2019
	Operating lease		Finance lease		Total
2019 (remaining six months)	$	865	$	72	$	937
2020		1,847		143		1,990
2021		1,853		131		1,984
2022		1,851		123		1,974
2023		1,839		121		1,960
2024		128		10		138
Thereafter		—		—		—
Total lease payments		8,383		600		8,983
Less: interest		418		23		441
Present value of lease liabilities	$	7,965	$	577	$	8,542

Summary of maturities of finance lease liabilities


	June 30, 2019
	Operating lease		Finance lease		Total
2019 (remaining six months)	$	865	$	72	$	937
2020		1,847		143		1,990
2021		1,853		131		1,984
2022		1,851		123		1,974
2023		1,839		121		1,960
2024		128		10		138
Thereafter		—		—		—
Total lease payments		8,383		600		8,983
Less: interest		418		23		441
Present value of lease liabilities	$	7,965	$	577	$	8,542

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


	June 30,
	2019

Weighted average remaining lease term in years	4.6
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


	June 30,
	2019

Weighted average remaining lease term in years	4.4
Weighted average discount rate (1)	1.7	%

(1)

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

Schedule of supplemental cash flow information related to operating and finance leases


	Six months ended
	June 30, 2019

Cash paid for amounts included in the measurement of operating lease liabilities (1)	$	1,725
Cash paid for amounts included in the measurement of finance lease liabilities (1)		1,391
Operating lease assets obtained in exchange for lease obligations (2)		5,557
Finance lease assets obtained in exchange for lease obligations (2)		634

(1)

The cash paid for amounts included in the measurement of lease liabilities includes upfront payments.

(2)

The lease assets reported in the cash flow information exclude upfront payments.

Accrued expenses and other current liabilities (Tables)

6 Months Ended

Jun. 30, 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):


	June 30,		December 31,
	2019		2018

Consulting fees	$	1,213	$	1,764
Salaries and bonuses		1,098		1,404
Social security contributions		232		121
Unearned grant income (current)		907		833
Operating lease liabilities		1,786		—
Finance lease liabilities		147		—
Other accruals and liabilities		1,680		298
Total	$	7,063	$	4,420

Loans payable (Tables)

6 Months Ended

Jun. 30, 2019

Loans payable

Schedule of loans payable


	June 30,		December 31,
	2019		2018

Loans from FFG	$	8,256	$	8,316
Unamortized debt discount		(3,502)		(3,924)
Total Loans payable, net	$	4,754	$	4,392

Redeemable convertible preferred stock (Tables)

6 Months Ended

Jun. 30, 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)

6 Months Ended

Jun. 30, 2019

Stock-based compensation

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


	Three months ended June 30,			Six months ended June 30,
	2019		2018	2019		2018

Risk-free interest rate	2.45	%	—	2.45	%	—
Expected term (in years)	6.1		—	6.1		—
Expected volatility	73.5	%	—	73.5	%	—
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	1,070,896		14.00
Exercised	—		—
Forfeited	(84,266)		6.81
Outstanding as of June 30, 2019	2,592,955	$	6.77	8.5	$	8,472

Options exercisable as of June 30, 2019	814,494	$	0.13	7.6	$	5,375
Options unvested as of June 30, 2019	1,778,461	$	9.80	8.9	$	3,097

Schedule of stock-based compensation expense

Stock-based compensation expense was classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):


	Three months ended June 30,				Six months ended June 30,
	2019		2018		2019		2018

Research and development expenses	$	401	$	93	$	662	$	186
General and administrative expenses		805		113		927		225
	$	1,206	$	206	$	1,589	$	411

Net loss per share (Tables)

6 Months Ended

Jun. 30, 2019

Net loss per share

Schedule of basic and diluted net loss per share


	Three months ended June 30,				Six months ended June 30,
	2019		2018		2019		2018

Numerator:
Net loss	$	(12,079)	$	(5,819)	$	(21,408)	$	(10,392)

Denominator:
Weighted-average common shares outstanding, basic and diluted		19,240,977		911,777		10,174,157		911,777

Net loss per share, basic and diluted	$	(0.63)	$	(6.38)	$	(2.10)	$	(11.40)

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


	Three and six months ended June 30,
	2019	2018

Series A Preferred Stock	—	1,604,574
Series B Preferred Stock	—	5,730,612
Series C Preferred Stock	—	8,074,447
Series D Preferred Stock	—	—
Options issued and outstanding	2,592,955	1,428,191
Total	2,592,955	16,837,824

Summary of significant accounting policies - Going concern and Deferred offering costs (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Summary of significant accounting policies
Net losses	$ 12,079	$ 9,329	$ 5,819	$ 4,573	$ 21,408	$ 10,392
Accumulated deficit	$ 81,390				81,390		$ 59,982
Issuance costs					$ 9,400
Deferred offering costs							$ 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)	6 Months Ended
	Jun. 30, 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 - Recent accounting pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Jun. 30, 2019
Summary of significant accounting policies
Lease, Practical Expedients, Package [true false]	true
Lease, Practical Expedient Land Easement [true false]	false
Lease, Practical Expedient, Use of Hindsight [true false]	false
Operating lease assets		$ 8,909
Operating lease liability		$ 7,965
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
Restatement Adjustment \| ASU 2016-02
Summary of significant accounting policies
Operating lease assets	$ 3,300
Operating lease liability	$ 3,300

Collaboration and Licensing Agreements (Details)	1 Months Ended	3 Months Ended		6 Months Ended
Collaboration and Licensing Agreements (Details)	Jun. 30, 2018 USD ($) item	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Collaboration and Licensing Agreements
Revenue from milestones amount		$ 4,051,000	$ 649,000	$ 6,286,000	$ 649,000
Gilead Collaboration and License Agreement
Collaboration and Licensing Agreements
Number of preclinical research programs \| item	2
Non-refundable, upfront payment	$ 10,000,000
Revenue from collaboration and licensing		1,400,000		2,300,000
Liability in deferred revenues		4,900,000		$ 4,900,000
Percentage of deferred revenue is expected to be recognized				73.00%
Percentage of deferred revenue is expected to be recognized in 2020				25.00%
Percentage of deferred revenue is expected to be recognized in 2021				$ 2
Revenue from milestones amount		2,000,000		$ 2,000,000	$ 400,000
Payment term (in days)				60 days
Revenue from cost reimbursements		700,000	$ 200,000	$ 2,000,000
Contract asset relating to the sublicense payment		$ 500,000		500,000		$ 400,000
Development Milestones \| Gilead Collaboration and License Agreement
Collaboration and Licensing Agreements
Revenue from milestones amount				280,000,000
Commercial Milestones \| Gilead Collaboration and License Agreement
Collaboration and Licensing Agreements
Revenue from milestones amount				$ 100,000,000

Leases (Details) $ in Thousands	6 Months Ended
Leases (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Leases
Cash balance maintained to secure a letter of credit associated with a real estate lease	$ 320
Presentation of leases in condensed consolidated balance sheets:
Operating lease assets	$ 8,909
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Operating lease assets
Finance lease assets	$ 1,803
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent
Total lease assets	$ 10,712
Current operating lease liability	$ 1,786
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedExpensesAndOtherCurrentLiabilities
Current finance lease liability	$ 147
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedExpensesAndOtherCurrentLiabilities
Total current lease liabilities	$ 1,933
Non-current operating lease liability	$ 6,177
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Non-current operating lease liability
Non-current finance lease liability	$ 432
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Total non-current lease liabilities	$ 6,609
Total lease liabilities	8,542
Right-of-use asset derecognized	200
Lease liability derecognized	$ 200
Minimum
Leases
Remaining lease term (in years)	2 years
Maximum
Leases
Remaining lease term (in years)	5 years

Leases - Lease costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Leases - Lease costs (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2019
Leases
Net lease expenses	$ 558	$ 930
Research and Development Expense
Leases
Operating lease expenses	296	498
Finance lease amortization expenses	95	158
General and Administrative Expense
Leases
Operating lease expenses	199	310
Finance lease amortization expenses	4	6
Interest expenses
Leases
Interest on finance lease liabilities	3	4
Other income (expense)
Leases
Sublease income	$ (39)	$ (46)

Leases - Minimum lease payments (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Operating leases
2019 (remaining six months)	$ 865
2020	1,847
2021	1,853
2022	1,851
2023	1,839
2024	128
Total lease payments	8,383
Less: interest	418
Present value of lease liabilities	7,965
Finance leases
2019 (remaining six months)	72
2020	143
2021	131
2022	123
2023	121
2024	10
Total lease payments	600
Less: interest	23
Present value of lease liabilities	577
Total
2019 (remaining six months)	937
2020	1,990
2021	1,984
2022	1,974
2023	1,960
2024	138
Total lease payments	8,983
Less: interest	441
Present value of lease liabilities	$ 8,542

Leases - Minimum rental commitments under non-cancelable leases (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Minimum rental commitments under non-cancelable leases
2019	$ 520
2020	278
2021	43
2022	43
2023	11
Total	$ 895

Leases - Lease guidance minimum rental commitments - weighted average remaining lease term and weighted average discount rate (Details)	6 Months Ended
	Jun. 30, 2019
Leases
Operating lease, Weighted average remaining lease term (in years)	4 years 7 months 6 days
Operating lease, Weighted average discount rate	2.30%
Finance lease, Weighted average remaining lease term (in years)	4 years 4 months 24 days
Finance lease, Weighted average discount rate	1.70%
Sublease, remaining lease term	1 year 8 months 12 days

Leases - Supplemental disclosure of cash flow information related to operating and finance leases (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Leases
Cash paid for amounts included in the measurement of operating lease liabilities	$ 1,725
Cash paid for amounts included in the measurement of finance lease liabilities	1,391
Operating lease assets obtained in exchange for lease obligations	5,557
Finance lease assets obtained in exchange for lease obligations	$ 634

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued expenses and other current liabilities
Consulting fees	$ 1,213	$ 1,764
Salaries and bonuses	1,098	1,404
Social security contributions	232	121
Unearned grant income (current)	907	833
Operating lease liabilities	1,786
Finance lease liabilities	147
Other accruals and liabilities	1,680	298
Total	$ 7,063	$ 4,420

Loans payable (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Loans payable
Loans from FFG	$ 8,256	$ 8,316
Unamortized debt discount	(3,502)	(3,924)
Total Loans payable, net	$ 4,754	$ 4,392
Minimum
Loans payable
Interest rate (as a percent)	0.75%
Maximum
Loans payable
Interest rate (as a percent)	1.00%

Redeemable convertible preferred stock (Details) - USD ($)			1 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended
	Apr. 23, 2019	Jan. 04, 2018	Feb. 28, 2019	Dec. 31, 2017	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018
Redeemable convertible preferred stock
Preferred Stock issued (in shares)						257,000
Average price (in dollars per sale)					$ 6.73		$ 6.73	$ 10.33
Issuance costs							$ 9,400,000
Outstanding shares of Preferred Stock converted (in shares)					(1,580,506)
Amount reclassified upon conversion of Preferred Stock					$ 142,048,000
Preferred Stock outstanding (in shares)					0		0	0
Undesignated Preferred Stock authorized (in shares)					10,000,000		10,000,000	0
Preferred shares authorized (in shares)					0	1,580,506	0	1,323,506
Preferred shares issued and outstanding (in shares)				1,323,506	0	1,580,506	0	1,323,506	1,323,506	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		$ 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
Redeemable convertible preferred stock
Stock issued upon conversion of Preferred Stock (in shares)					14,582,161
Amount reclassified upon conversion of Preferred Stock					$ 2,000
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 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
Average price (in dollars per sale)				$ 85.60
Gross Proceeds from issuance of stock		$ 6,500,000		$ 59,400,000
Issuance costs		$ 100,000
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
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		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
Amount reclassified upon conversion of Preferred Stock					$ 0

Common stock and Class A common stock (Details) $ / shares in Units, $ in Thousands			3 Months Ended	6 Months Ended
	Apr. 23, 2019 USD ($) $ / shares shares	Apr. 05, 2019	Jun. 30, 2019 Vote $ / shares shares	Jun. 30, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 $ / shares shares
Share Price \| $ / shares			$ 6.73	$ 6.73	$ 10.33
Offering costs \| $				$ 9,400
Common stock, issued (in shares)			21,588,756	21,588,756	1,006,595
Common stock, outstanding (in shares)			21,588,756	21,588,756	1,006,595
Number of votes \| Vote			1	1
Common stock, shares authorized			100,000,000	100,000,000	18,454,860
Number of common stock issued upon conversion of each share of Class A Common Stock		11.643
IPO
Share Price \| $ / shares			$ 14.00	$ 14.00
Offering costs \| $				$ 9,386
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 \| IPO
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
Class A common stock
Common stock, issued (in shares)			3,819,732	3,819,732	0
Common stock, outstanding (in shares)			3,819,732	3,819,732	0
Common stock, shares authorized			3,900,000	3,900,000	0
Number of common stock issued upon conversion of each share				1
Class A common stock \| IPO
Stock issued upon conversion of Preferred Stock (in shares)	3,819,732
Class A common stock \| Common Stock
Stock issued upon conversion of Preferred Stock (in shares)			3,819,732

Stock-based compensation - 2018 Stock Option and Grant Plan (Details)		6 Months Ended	12 Months Ended
	Apr. 01, 2019 installment shares	Jun. 30, 2019 installment shares	Dec. 31, 2018 € / shares shares
Stock-based compensation
Number of shares granted to US employee		1,070,896
Options outstanding		2,592,955	1,606,325
2018 Stock Option and Grant Plan
Stock-based compensation
Options outstanding		1,538,987
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
2019 Stock Option and Incentive Plan
Stock-based compensation
Number stock option authorized	2,608,042
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	25.00%
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	75.00%
Number of quarterly installments for vesting \| installment	8

Stock-based compensation - 2019 Stock Option and Incentive Plan (Details) - 2019 Stock Option and Incentive Plan		6 Months Ended
	Apr. 01, 2019 installment shares	Jun. 30, 2019
Stock-based compensation
Number stock option authorized \| shares	2,608,042
Number of shares outstanding were cumulatively increased		4.00%
Vesting period	4 years
Non Executive Directors
Stock-based compensation
Vesting period	3 years
Vesting upon first anniversary
Stock-based compensation
Percentage of options vesting	25.00%
Vesting upon first anniversary \| Non Executive Directors
Stock-based compensation
Percentage of options vesting	25.00%
Vesting in equal quarterly installments
Stock-based compensation
Percentage of options vesting	75.00%
Number of quarterly installments for vesting	12
Vesting in equal quarterly installments \| Non Executive Directors
Stock-based compensation
Percentage of options vesting	75.00%
Number of quarterly installments for vesting	8

Stock-based compensation - Assumptions used for estimating the fair value of stock options granted (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Assumptions used in the Black-Scholes option-pricing model
Risk-free interest rate	2.45%	2.45%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	73.50%	73.50%

Stock-based compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Number of Shares
Beginning balance	1,606,325
Granted	1,070,896
Forfeited	(84,266)
Ending balance	2,592,955		1,606,325
Option exercisable	814,494
Option unvested	1,778,461
Weighted Averaged Exercise Price
Beginning balance	$ 1.95
Granted	14.00
Forfeited	6.81
Ending balance	6.77		$ 1.95
Option exercisable	0.13
Option unvested	$ 9.80
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	8 years 6 months		8 years
Weighted Average Remaining Contractual Term, option exercisable	7 years 7 months 6 days
Weighted Average Remaining Contractual Term, option unvested	8 years 10 months 24 days
Aggregate Intrinsic Value, option unvested	$ 3,097
Aggregate Intrinsic Value, option exercisable	5,375
Aggregate Intrinsic Value, ending balance	8,472		$ 13,466
Aggregate Intrinsic Value, beginning balance	$ 13,466
Average price (in dollars per sale)	$ 6.73		$ 10.33
Proceeds from option exercise	$ 0	$ 0

Stock-based compensation - Stock-based compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Stock-based compensation
Stock-based compensation expense	$ 1,206	$ 206	$ 1,589	$ 411
Research and Development Expense
Stock-based compensation
Stock-based compensation expense	401	93	662	186
General and Administrative Expense
Stock-based compensation
Stock-based compensation expense	$ 805	$ 113	$ 927	$ 225

Commitments and contingencies (Details) $ in Millions	3 Months Ended	6 Months Ended
Commitments and contingencies (Details) $ in Millions	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Commitments and contingencies
Non-cancellable obligations	$ 15.9	$ 15.9
2019 (remaining six months)	6.1	6.1
2020	7.7	7.7
2021	2.1	2.1
Licensing fees from intellectual property licenses	$ 0.1	$ 0.3

Net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (12,079)	$ (9,329)	$ (5,819)	$ (4,573)	$ (21,408)	$ (10,392)
Denominator:
Weighted-average common shares outstanding, basic and diluted	19,240,977		911,777		10,174,157	911,777
Net loss per share, basic and diluted	$ (0.63)		$ (6.38)		$ (2.10)	$ (11.40)

- 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	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Anti-dilutive securities
Anti-dilutive shares	2,592,955	16,837,824
Series A Preferred Stock
Anti-dilutive securities
Anti-dilutive shares		1,604,574
Series B Preferred Stock
Anti-dilutive securities
Anti-dilutive shares		5,730,612
Series C Preferred Stock
Anti-dilutive securities
Anti-dilutive shares		8,074,447
Options
Anti-dilutive securities
Anti-dilutive shares	2,592,955	1,428,191

Related parties (Details) - USD ($) $ in Millions	6 Months Ended
Related parties (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jun. 30, 2018
Series D Preferred Stock
Related parties
Shares issued	50,670
Proceeds from shares issued	$ 7.4
Common Stock
Related parties
Shares issued	1,303,750
Proceeds from shares issued	$ 18.3
University of Basel
Related parties
Research and development expenses	0.3	$ 0.3
Royalties paid	$ 0.0	$ 0.0

Subsequent events (Details)		6 Months Ended
Subsequent events (Details)	Jul. 12, 2019 installment shares	Jun. 30, 2019 shares
Subsequent events
Granted		1,070,896
Subsequent events \| Options
Subsequent events
Granted	164,592
Vesting period	4 years
Number of quarterly installments of vesting \| installment	12
Subsequent events \| Options \| Vesting upon first anniversary
Subsequent events
Vesting percentage	25.00%
Subsequent events \| Options \| Vesting in equal quarterly installments
Subsequent events
Vesting percentage	75.00%

Summary of significant accounting policies - Stock split (Details)	Apr. 05, 2019
Summary of significant accounting policies
Stock split ratio	11.643

Income taxes (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2018
Income taxes
Income tax benefits for the net operating losses incurred	$ 0	$ 0