0000950170-22-014904 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2022	Jul. 29, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2022
Entity File Number	001-38944
Entity Registrant Name	Akero Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-5266573
Entity Address, Address Line One	601 Gateway Boulevard, Suite 350
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	487-6488
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	AKRO
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		37,571,426
Entity Central Index Key	0001744659
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 177,727	$ 150,483
Short-term marketable securities	2,998	37,775
Prepaid expenses and other current assets	3,422	5,324
Total current assets	184,147	193,582
Property and equipment, net	68	90
Right of use asset	1,352	1,459
Other assets, noncurrent	108	417
Total assets	185,675	195,548
Current liabilities:
Accounts payable	6,877	6,706
Accrued expenses and other current liabilities	19,820	18,422
Total current liabilities	26,697	25,128
Loan payable, noncurrent	9,366
Warrant liability	41
Operating lease liability, noncurrent	1,199	1,311
Total liabilities	37,303	26,439
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, $0.0001 par value, 150,000,000 shares authorized as of June 30, 2022 and December 31, 2021; 37,570,326 and 34,900,727 shares issued and outstanding as of June 30, 2022 and December 31, 2021, respectively	4	4
Additional paid-in capital	512,107	479,436
Accumulated other comprehensive loss	(3)	(27)
Accumulated deficit	(363,736)	(310,304)
Total stockholders' equity	148,372	169,109
Total liabilities and stockholders' equity	$ 185,675	$ 195,548

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	37,570,326	34,900,727
Common stock, shares outstanding	37,570,326	34,900,727

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating expenses:
Research and development	$ 21,363	$ 23,976	$ 41,877	$ 34,578
General and administrative	6,231	4,990	11,768	9,516
Total operating expenses	27,594	28,966	53,645	44,094
Loss from operations	(27,594)	(28,966)	(53,645)	(44,094)
Interest expense	53		53
Other income	244	33	266	71
Net loss	(27,403)	(28,933)	(53,432)	(44,023)
Net unrealized gain (loss) on short-term marketable securities	27	(7)	24	(6)
Comprehensive loss	$ (27,376)	$ (28,940)	$ (53,408)	$ (44,029)
Net loss per share, basic	$ (0.77)	$ (0.83)	$ (1.52)	$ (1.27)
Net loss per share, diluted	$ (0.77)	$ (0.83)	$ (1.52)	$ (1.27)
Weighted-average number of shares used in computing net loss per common share, basic	35,383,685	34,814,631	35,195,638	34,779,647
Weighted-average number of shares used in computing net loss per common share, diluted	35,383,685	34,814,631	35,195,638	34,779,647

Condensed Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In-Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Balance at beginning at Dec. 31, 2020	$ 258,712	$ 4	$ 468,238	$ (3)	$ (209,527)
Balance at beginning (in shares) at Dec. 31, 2020		34,741,649
Exercise of stock options	24		24
Exercise of stock options (in shares)		28,670
Vesting of restricted stock	9		9
Stock-based compensation expense	2,364		2,364
Net unrealized gain (loss) on short-term marketable securities	1			1
Net loss	(15,090)				(15,090)
Balance at ending at Mar. 31, 2021	246,020	$ 4	470,635	(2)	(224,617)
Balance at ending (in shares) at Mar. 31, 2021		34,770,319
Balance at beginning at Dec. 31, 2020	258,712	$ 4	468,238	(3)	(209,527)
Balance at beginning (in shares) at Dec. 31, 2020		34,741,649
Net unrealized gain (loss) on short-term marketable securities	(6)
Net loss	(44,023)
Balance at ending at Jun. 30, 2021	220,133	$ 4	473,688	(9)	(253,550)
Balance at ending (in shares) at Jun. 30, 2021		34,840,782
Balance at beginning at Dec. 31, 2020	258,712	$ 4	468,238	(3)	(209,527)
Balance at beginning (in shares) at Dec. 31, 2020		34,741,649
Net loss	(100,777)
Balance at ending at Dec. 31, 2021	169,109	$ 4	479,436	(27)	(310,304)
Balance at ending (in shares) at Dec. 31, 2021		34,900,727
Balance at beginning at Mar. 31, 2021	246,020	$ 4	470,635	(2)	(224,617)
Balance at beginning (in shares) at Mar. 31, 2021		34,770,319
Exercise of stock options	393		393
Exercise of stock options (in shares)		60,333
Vesting of restricted stock	9		9
Issuance of common stock pursuant to ESPP purchases	215		215
Issuance of common stock pursuant to ESPP purchases (in shares)		10,130
Stock-based compensation expense	2,436		2,436
Net unrealized gain (loss) on short-term marketable securities	(7)			(7)
Net loss	(28,933)				(28,933)
Balance at ending at Jun. 30, 2021	220,133	$ 4	473,688	(9)	(253,550)
Balance at ending (in shares) at Jun. 30, 2021		34,840,782
Balance at beginning at Dec. 31, 2021	169,109	$ 4	479,436	(27)	(310,304)
Balance at beginning (in shares) at Dec. 31, 2021		34,900,727
Exercise of stock options	147		147
Exercise of stock options (in shares)		122,208
Stock-based compensation expense	3,311		3,311
Net unrealized gain (loss) on short-term marketable securities	(3)			(3)
Net loss	(26,029)				(26,029)
Balance at ending at Mar. 31, 2022	146,535	$ 4	482,894	(30)	(336,333)
Balance at ending (in shares) at Mar. 31, 2022		35,022,935
Balance at beginning at Dec. 31, 2021	$ 169,109	$ 4	479,436	(27)	(310,304)
Balance at beginning (in shares) at Dec. 31, 2021		34,900,727
Exercise of stock options (in shares)	122,208
Net unrealized gain (loss) on short-term marketable securities	$ 24
Net loss	(53,432)
Balance at ending at Jun. 30, 2022	148,372	$ 4	512,107	(3)	(363,736)
Balance at ending (in shares) at Jun. 30, 2022		37,570,326
Balance at beginning at Mar. 31, 2022	146,535	$ 4	482,894	(30)	(336,333)
Balance at beginning (in shares) at Mar. 31, 2022		35,022,935
Issuance of common stock pursuant to ESPP purchases	178		178
Issuance of common stock pursuant to ESPP purchases (in shares)		22,139
Issuance of common stock pursuant to equity investment by Pfizer, net of issuance costs	24,647		24,647
Issuance of common stock pursuant to equity investment by Pfizer, net of issuance costs (in shares)		2,525,252
Vested warrants issued pursuant to loan agreement	227		227
Stock-based compensation expense	4,161		4,161
Net unrealized gain (loss) on short-term marketable securities	27			27
Net loss	(27,403)				(27,403)
Balance at ending at Jun. 30, 2022	$ 148,372	$ 4	$ 512,107	$ (3)	$ (363,736)
Balance at ending (in shares) at Jun. 30, 2022		37,570,326

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (53,432)	$ (44,023)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,472	4,800
Depreciation	22	21
Non-cash lease expense	107	100
Net amortization of premiums and discounts on short-term investments	181	303
Amortization of debt issuance costs and discount	16
Unrealized foreign exchange gain and loss	(24)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	2,122	(2,848)
Accounts payable	145	(1,121)
Accrued expenses and other current liabilities	1,105	4,475
Operating lease liability	(99)	(87)
Net cash used in operating activities	(42,385)	(38,380)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of short-term marketable securities		(31,654)
Proceeds from maturities of short-term marketable securities	34,620	40,000
Net cash provided by investing activities	34,620	8,346
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the exercise of stock options	147	417
Proceeds from the issuance of common stock pursuant to employee stock purchase plan purchases	178	215
Proceeds from the issuance of common stock pursuant to private offering	25,000
Proceeds from loan payable	10,000
Payment of loan payable issuance costs	(255)
Payment of deferred offering costs	(61)	(342)
Net cash provided by financing activities	35,009	290
Net increase (decrease) in cash, cash equivalents and restricted cash	27,244	(29,744)
Cash, cash equivalents and restricted cash at the beginning of the period	150,591	187,390
Cash, cash equivalents and restricted cash at the end of the period	177,835	157,646
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Change in net unrealizable (loss) gain on marketable securities	24	(6)
Deferred offering costs reclassified to additional paid-in equity	150
Equity Issuance Costs Included in Accounts Payable and Accrued Expenses and Other Current Liabilities	202
Debt issuance costs included in accounts payable and accrued expenses and other current liabilities	127
Deferred offering costs included in accounts payable and accrued expenses and other current liabilities	$ 15	$ 123

Nature of the business and basis of presentation

6 Months Ended

Jun. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of the business and basis of presentation

1. Nature of the business and basis of presentation

Akero Therapeutics, Inc., together with its wholly owned subsidiary Akero Securities Corporation, (“Akero” or the “Company”) is a clinical-stage company dedicated to developing transformational treatments for patients with serious metabolic diseases marked by high unmet medical need, including non-alcoholic steatohepatitis, or NASH, a disease without any approved therapies. NASH is a severe form of nonalcoholic fatty liver disease, or NAFLD, characterized by inflammation and fibrosis in the liver that can progress to cirrhosis, liver failure, cancer and death. The Company’s lead product candidate is efruxifermin, or EFX, an analog of fibroblast growth factor 21, or FGF21, which is an endogenously expressed hormone that protects against cellular stress and regulates metabolism of lipids, carbohydrates and proteins throughout the body. EFX is currently being evaluated in two Phase 2b clinical trials in patients with biopsy-confirmed NASH: the HARMONY study in patients with pre-cirrhotic NASH (F2-F3 fibrosis) and the SYMMETRY study in cirrhotic patients (F4 fibrosis, compensated). The SYMMETRY study includes an expansion cohort, known as Cohort D, evaluating the safety and tolerability of EFX compared to placebo when added to an existing GLP-1 receptor agonist in patients with pre-cirrhotic NASH (F1-F3 fibrosis) and Type 2 diabetes. The Company previously conducted a Phase 2a clinical trial, the BALANCED study, to evaluate EFX in the treatment of patients with biopsy-confirmed NASH. The main portion of this study in patients with pre-cirrhotic NASH (F1-F3 fibrosis) showed EFX’s potential to reverse fibrosis, resolve NASH, improve liver health, improve glycemic control and improve lipoprotein profile. An expansion cohort in patients with cirrhotic NASH (F4 fibrosis), compensated) showed comparable results. Based on clinical data to date, the Company believes EFX has the potential to be a highly differentiated, best-in-class FGF21 analog and promising NASH monotherapy, if approved.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, completion and success of clinical testing, development by competitors of new technological innovations, compliance with governmental regulations, dependence on key personnel and protection of proprietary technology and the ability to secure additional capital to fund operations. EFX will require extensive clinical testing prior to regulatory approval and commercialization. These efforts require significant amounts of additional capital, adequate personnel, and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Basis of presentation

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company after elimination of all intercompany accounts and transactions. All adjustments necessary for the fair presentation of the Company’s condensed consolidated financial statements for the periods presented have been reflected.

Liquidity

In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), the Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the consolidated financial statements are issued.

Since its inception, the Company has funded its operations primarily with proceeds from sales of redeemable convertible preferred stock and with proceeds from its initial public offering (“IPO”) in June 2019, a follow-on public offering of its common stock in July 2020 and most recently through a term loan and a registered direct offering in June 2022. The Company has incurred recurring losses since its inception, including net losses of $53,432 and $44,023 for the six months ended June 30, 2022 and 2021, respectively, and net losses of $100,777 and $79,207 for the years ended December 31, 2021 and 2020, respectively. In addition, as of June 30, 2022, the Company had an accumulated deficit of

$363,736. The Company expects to continue to generate operating losses for the foreseeable future. As of August 5, 2022, the issuance date of these condensed consolidated financial statements, the Company expects that its existing cash, cash equivalents and short-term marketable securities of $180,725 as of June 30, 2022, will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of these condensed consolidated financial statements. The Company expects that it will require additional funding to complete the clinical development of EFX, commercialize EFX, if it receives regulatory approval, and pursue in-licenses or acquisitions of other product candidates.

If the Company is unable to obtain funding, the Company will 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, or the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

Summary of significant accounting policies	6 Months Ended
Summary of significant accounting policies	Jun. 30, 2022
Accounting Policies [Abstract]
Summary of significant accounting policies	2. Summary of significant accounting policies Unaudited interim financial statements The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in accordance with GAAP for interim financial reporting and as required by Regulation S-X, Rule 10-01. The unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the Company’s condensed consolidated balance sheet as of June 30, 2022, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2022 and 2021, the condensed consolidated statement of stockholders’ equity (deficit) as of June 30, 2022 and the condensed consolidated statements of cash flows for the six months ended June 30, 2022. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2022 and 2021 are unaudited. The results for the three and six months ended June 30, 2022 are not necessarily indicative of results to be expected for the year ending December 31, 2022, any other interim periods, or any future year or period. Use of estimates The preparation of the Company's condensed consolidated 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 condensed consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the recognition of research and development expenses, stock-based compensation expense, warrant liabilities and the valuation allowance for deferred tax assets. 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 when there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Cash and cash equivalents The Company considers all highly liquid investments with original maturities of three months or less at the time of purchase to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts. Short-term marketable securities The Company invests in short-term marketable securities, primarily money market funds, commercial paper, U.S. treasury securities and corporate debt securities. The Company continually evaluates the credit ratings of its investment portfolio and underlying securities. The Company invests in accordance with its investment policy and invests at the date of purchase in securities with high ratings from top rating agencies. The Company classifies its short-term marketable securities as available-for-sale securities and reports them at fair value in short-term marketable securities on the condensed consolidated balance sheets with related unrealized gains and losses included within accumulated other comprehensive gain (loss) on the condensed consolidated balance sheets. The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in other income on the condensed consolidated statements of operations and comprehensive loss. When the fair value is below the amortized cost of a marketable security, the Company reviews and determines whether the impairment is due to credit-related factors or noncredit-related factors. The credit-related impairment amount is recognized in other income on the condensed consolidated statements of operations and comprehensive loss, with a corresponding allowance for credit losses account in the condensed consolidated balance sheet. Subsequent improvements in expected credit losses are recognized as a reversal of an amount in the allowance account. If the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis, then the allowance for the credit loss is written-off and the excess of the amortized cost basis of the asset over its fair value is recorded in the condensed consolidated statements of operations. There were no credit losses recorded during the periods ended June 30, 2022 and December 31, 2021. Restricted cash As of June 30, 2022 and December 31, 2021, the Company was required to maintain a separate cash balance of $108 for the benefit of the landlord in connection with the Company’s Gateway office space lease in South San Francisco, California (the “Gateway Lease”), which is classified within other assets (non-current) on the condensed consolidated balance sheets (see Note 12). Concentrations of credit risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and short-term marketable securities. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company deposits its cash investments in financial institutions that it believes have high credit quality and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. At June 30, 2022 and December 31, 2021, all of the Company's cash, cash equivalents and short-term investments were held at one accredited financial institution. Leases The Company determines whether an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether the Company has the right to control the identified asset. Right-of-use, or ROU, assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement date based on the present value of future lease payments over the lease term. ROU assets are based on the measurement of the lease liability and are further adjusted by any lease payments made prior to or on lease commencement, lease incentives received and initial direct costs incurred, as applicable. The Company has elected to not recognize leases with a lease term of one year or less on its balance sheet. Operating lease costs included in the measurement of the lease are recognized on a straight-line basis over the lease term. Variable lease costs are expensed as incurred as an operating expense. The Company determines the lease classification and the present value of future lease payments at the time of the lease commencement using an incremental borrowing rate that it estimates based upon the Company’s credit risk and term of the lease. The interest rate implicit in lease contracts has not historically been readily determinable and the Company must therefore use the appropriate incremental borrowing rate to measure its leases. To estimate the incremental borrowing rate, a credit rating applicable to the Company is estimated using a synthetic credit rating analysis since the Company does not currently have a rating agency-based credit rating. Research and development costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred to discover, research and develop drug candidates, including personnel expenses, stock-based compensation expense, third-party license fees and external costs including fees paid to consultants, contract manufacturing organizations, or CMOs, and clinical research organizations, or CROs, in connection with drug product manufacturing, nonclinical studies and clinical trials, and other related clinical trial fees, such as for investigator grants, patient screening, laboratory work, clinical trial database management, clinical trial material management and statistical compilation and analysis. Non-refundable prepayments for goods or services that will be used or rendered for future research and development activities are recorded as prepaid expenses. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered. Costs incurred in obtaining technology licenses are charged immediately to research and development expense if the technology licensed has not reached technological feasibility and has no alternative future uses. Research contract costs and accruals The Company has entered into various research and development and other agreements with commercial firms, researchers and others for provisions of goods and services. These agreements are generally cancelable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company's estimates. Stock-based compensation The Company measures all stock-based awards granted to employees and nonemployees based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company recognizes stock-based compensation expense for awards that contain performance-based conditions using the accelerated attribution method when management determines it is probable that the performance condition will be satisfied. The Company accounts for forfeitures as they occur. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which requires inputs based on certain subjective assumptions, including the expected stock price volatility, the expected term of the option, the risk-free interest rate for a period that approximates the expected term of the option, and the Company's expected dividend yield. The Company went public in June 2019 and accordingly, lacks sufficient company-specific historical and implied volatility information for its shares traded in the public markets. Therefore, it estimates its expected share price volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded share price. The expected term of the Company's stock options has been determined utilizing the "simplified" method for awards that qualify as "plain-vanilla" options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future. The fair value of each common stock award is estimated on the date of grant based on the fair value of the Company's common stock on that same date. Compensation expense for purchases under the Employee Stock Purchase Plan is recognized based on the fair value of the common stock estimated based on the closing price of our common stock as reported on the date of offering, less the purchase discount percentage provided for in the plan. The Company classifies stock-based compensation expense in its condensed consolidated statement of operations and comprehensive loss in the same manner in which the award recipient's payroll costs are classified or in which the award recipient's service payments are classified. Loan Payable The Company initially reviews loan payables to identify the units of account for recognition purposes. The Company identifies the units of account by identifying each freestanding financial instrument included in the debt arrangement. For freestanding equity-linked financial instruments that are not in the form of shares, liability classification is used if the instrument embodies an obligation to repurchase the Company’s shares that may require the use of cash or other assets or the instrument may require the issuance of a variable number of the Company’s shares with a monetary value that is predominately based on a fixed value, based on variations in variables other than the fair value of the Company’s stock, or based on variations inversely related to the fair value of the Company’s stock. The Company will then review for embedded features within the debt instrument to evaluate whether the embedded features require bifurcation from the debt host instrument. Embedded features typically include conversion or exchange features, redemption features, or other embedded features. The identified embedded feature is bifurcated from the debt host instrument if the criteria in ASC 815-15-25-1 are met. Debt arrangements are classified on the consolidated balance sheet as current if the obligation of the debt arrangement is reasonably expected to be liquidated within 12 months. Loan payable is recorded net of debt discount which comprises issuance costs, customary closing and end of term charge or final fees, and the fair value of additional warrants issued in conjunction with the loan payable. Debt discount is amortized over the term of the loan payable using the effective interest method, and is recorded to interest expense on the consolidated statements of operations (see Note 6). Warrant Liabilities The Company accounts for warrants anticipated to be issued in the future under the Loan Agreement as liabilities and measures them at fair value using the Black-Scholes valuation model. The warrants are subject to remeasurement at each prospective balance sheet date, with any changes in the fair value recorded in the consolidated statements of operations. Comprehensive loss Comprehensive loss includes net loss as well as other changes in stockholders' equity (deficit) that result from transactions and economic events other than those with stockholders. The Company’s comprehensive loss is comprised of net loss and changes in unrealized gains and losses on its short-term marketable securities. Recently adopted accounting pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) ("ASU 2016-13"), which introduced a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The Company adopted ASU 2016-03 as of January 1, 2021. For available-for-sale debt securities with unrealized losses, those losses are recognized as allowances rather than reductions in the amortized cost of the underlying security. The adoption of ASU 2016-03 did not have a material impact on the Company's condensed consolidated financial statements. In August 2020, the FASB issued ASU No. 2020-06, “Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity”, or ASU 2020-06. ASU 2020-06 simplifies the accounting for convertible instruments by eliminating the requirement to separate embedded conversion features from the host contract when the conversion features are not required to be accounted for as derivatives under Topic 815, Derivatives and Hedging, or that do not result in substantial premiums accounted for as paid-in capital. The Company adopted ASU 2020-06 on January 1, 2022, on a modified retrospective basis. The adoption of ASU 2020-06 did not have a material impact on the Company's condensed consolidated financial statements.

Fair value measurements

6 Months Ended

Jun. 30, 2022

Fair Value Disclosures [Abstract]

Fair value measurements

3. Fair value measurements

Certain assets and liabilities of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

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

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Unobservable inputs that are supported by little or no market activity that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The following is a summary of our financial assets and liabilities measured at fair value on a recurring basis as of June 30, 2022 and December 31, 2021:


	June 30, 2022
	Total		Level 1		Level 2		Level 3
Money market funds	$	151,791	$	151,791	$	—	$	—
Corporate debt securities		2,998		—		2,998		—
Total assets	$	154,789	$	151,791	$	2,998	$	—

Warrant liabilities	$	41	$	—	$	—	$	41
Total liabilities	$	41	$	—	$	—	$	41

	December 31, 2021
	Total		Level 1		Level 2		Level 3
Money market funds	$	116,261	$	116,261	$	—	$	—
Corporate debt securities		37,775		—		37,775		—
	$	154,036	$	116,261	$	37,775	$	—

Corporate debt securities were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy.

The carrying values of the Company’s prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities. During the six months ended June 30, 2022 and the twelve months ended December 31, 2021, there were no transfers between Level 1, Level 2 and Level 3.

The Loan Payable is classified as a Level 3 liability. As of June 30, 2022, the carrying value of the Loan Payable, excluding unamortized debt issuance costs, approximates its fair value due to the variable interest rate. The Company estimated the fair value of the warrant liabilities using the Black-Scholes model based on key assumption and inputs (see Note 6). The Company utilizes a probability assessment to estimate the likelihood of vesting for the remaining Loan Agreement warrants and allocated the probability of occurrence percentage to the fair values calculated.

- Definition

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

+ References + Details

Short-term marketable securities

6 Months Ended

Jun. 30, 2022

Short-term marketable securities

Short-term marketable securities

4. Short-term marketable securities

The following is a summary of short-term marketable securities as of June 30, 2022 and December 31, 2021:


	June 30, 2022
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Credit losses		Fair value
Money market funds	$	151,791	$	—	$	—		$	—	$	151,791
Corporate debt securities		3,001		—		(3	)		—		2,998
	$	154,792	$	—	$	(3	)	$	—	$	154,789

Cash equivalents										$	151,791
Short-term marketable securities											2,998
										$	154,789

	December 31, 2021
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Credit losses		Fair value
Money market funds	$	116,261	$	—	$	—		$	—	$	116,261
Corporate debt securities		37,802		—		(27	)		—		37,775
	$	154,063	$	—	$	(27	)	$	—	$	154,036

Cash equivalents										$	116,261
Short-term marketable securities											37,775
										$	154,036

As of June 30, 2022 and December 31, 2021, all of the Company’s short-term marketable securities had contractual maturities of less than one year.

Accrued expenses and other current liabilities

6 Months Ended

Jun. 30, 2022

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities

5. Accrued expenses and other current liabilities

The following is a summary of accrued expenses and other current liabilities as of June 30, 2022 and December 31, 2021:


	June 30, 2022		December 31, 2021
Accrued external research and development expenses	$	16,847	$	17,539
Accrued employee compensation and benefits		1,910		554
Accrued legal and professional fees		808		124
Short-term lease liability and other		255		205
	$	19,820	$	18,422

Loan Payable and Warrant Liability

6 Months Ended

Jun. 30, 2022

Debt Disclosure [Abstract]

Loan Payable and Warrant Liability

6. Loan Payable and Warrant Liability

On June 15, 2022, the Company entered into a Loan and Security Agreement (“Loan Agreement”) with Hercules Capital, Inc. (“Hercules”), for an aggregate principal amount of $100,000 (“Term Loan”). Pursuant to the Loan Agreement, the Term Loan is available to the Company in four tranches, subject to certain terms and conditions.

Under the terms of the Loan Agreement, the Company received $10,000 upon closing and an additional $10,000 is available to the Company at its sole discretion. The second tranche of the Term Loan, consisting of up to an additional $15,000, will become available to the Company subject to the Company's achievement of certain clinical development milestones. The third tranche of the Term Loan, consisting of up to an additional $20,000, will become available to the Company upon the achievement of certain clinical and financial milestones. The fourth tranche of the Term Loan, consisting of up to an additional $45,000, will become available to the Company at Hercules sole discretion.

The Term Loan will mature on January 1, 2027 (the “Maturity Date”). The Term Loan bears interest at a variable annual rate equal to the greater of (a) 7.65% and (b) the Prime Rate (as reported in the Wall Street Journal) plus 3.65% (the “Interest Rate”). The Company may make payments of interest only through July 1, 2024, which may be extended to July 1, 2025 upon the achievement of the third tranche milestones (the “interest-only period”). After the interest-only period, the principal balance and related interest will be required to be repaid in equal monthly installments and continuing until the Maturity Date.

The Loan Agreement contains customary closing fees, events of default, and representations, warranties and covenants, including a financial covenant requiring the Company to maintain a minimum cash balance in relation to the outstanding principal balance of the Term Loan. The Loan Agreement provides for a prepayment charge equal to 3% of the outstanding principal balance of the Term Loan if prepayment is made within the first twelve months after closing, 2% if within the second twelve months after closing and 1% thereafter. In addition, the Loan Agreement provides for an End of Term Charge that will be the greater of 5.85% of the outstanding principal balance or $1,170, which is recognized as a debt discount and is being accreted into the amortization of debt issuance costs and discount using the effective interest rate method over the term of the loan payable.

Upon closing, the Company issued warrants to Hercules to purchase shares of the Company’s common stock, par value $0.0001 per share ("common stock"). The amount of shares that may be purchased for the Warrants will not exceed 1.5% multiplied by the greater of Tranche I and the aggregate original amount of the term loan advances, divided by the exercise price of the Warrants.

The Company was in compliance with all covenants of the Loan Agreement as of June 30, 2022.

The Company determined in accordance with ASC 480-10 that the initial tranche one advance of $10,000, the additional Term Loan advances available under tranches one, two, three and four and the warrants issued upon closing shall be accounted for as freestanding financial instruments as they are legally detachable and separately exercisable. The Company also determined in accordance with ASC 815-10 that the additional Term Loan advances available under tranches one, two, three and four do not qualify as derivative instruments and that the value associated with these commitments is immaterial.

Upon closing, the Company issued to Hercules warrants to purchase 36,718 shares of Company’s common stock and recognized the initial warrants at their relative fair value of $227 in shareholders equity. In accordance with ASC 815-40, the additional remaining warrants to purchase shares of the Company’s common stock at the closing of the Loan Agreement were recognized at their fair value of $41 as warrant liabilities given the variable settlement amount of the warrant shares. The additional remaining warrants under the Loan Agreement are considered an outstanding instrument at close of the Loan Agreement. The total fair value of $268 associated with these equity and liability classified warrants, is recognized as a debt discount and is being accreted into the amortization of debt issuance costs and discount using the effective interest rate method over the term of the loan payable. The Company will reassess the fair value of the warrant liability at the end of each prospective reporting period. The change in fair value of the warrant liability from June 15, 2022 until June 30, 2022 was immaterial.

Future principal debt payments on the currently outstanding loan payable as of June 30, 2022 are as follows (in thousands):


2022	$	—
2023		—
2024		1,764
2025		3,763
2026		4,096
2027		377
Total principal outstanding		10,000
End of term charge		1,170
Total principal outstanding and end of term charge		11,170
Unamortized discount and issuance costs		(1,804	)
Loan Payable - noncurrent	$	9,366

The Company estimated the fair value of the Warrant using the Black-Scholes model based on the following key assumptions:


	Three months ended June 30, 2022
Expected term (in years)		7.00
Expected volatility		76.15	%
Weighted average risk-free interest rate		3.39	%
Expected dividend yield		0.00	%

Stockholder's equity (deficit)

6 Months Ended

Jun. 30, 2022

Stockholders' Equity Note [Abstract]

Stockholder's equity (deficit)

7. Stockholder’s equity (deficit)

Common stock

As of June 30, 2022 and December 31, 2021, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue 150,000,000 shares of $0.0001 par value common stock. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. The holders of common stock, voting exclusively and as a separate class, have the exclusive right to vote for the election of directors of the Company. Common stockholders are entitled to receive dividends, as may be declared by the board of directors. Through June 30, 2022, no cash dividends had been declared or paid.

On June 24, 2019, the Company completed its IPO at which time the Company issued 6,612,500 shares of common stock, including the exercise in full by the underwriters of their option to purchase up to 862,500 additional shares of common stock, at a public offering price of $16.00 per share. The Company received $98,394, net of underwriting discounts and commissions, but before deducting offering costs paid by the Company, which were $2,942. Upon the closing of the IPO, all outstanding shares of convertible preferred stock converted into 21,056,136 shares of common stock.

On July 10, 2020, the Company completed a follow-on public offering at which time the Company issued 6,012,390 shares of common stock, including the exercise in full by the underwriters of their option to purchase up to 784,224 additional shares of common stock, at a public offering price of $36.00 per share. The Company received $203,460 net of underwriting discounts and commissions, but before deducting offering costs paid by the Company, which were $906.

On May 18, 2021, the Company filed a Form S-3 Registration Statement and the accompanying prospectus activating an At-The-Market, or ATM, facility by entering into a sales agreement with J.P. Morgan Securities LLC, relating to shares of the Company’s common stock offered. Pursuant to the terms of the sales agreement, the Company may offer and sell shares of common stock, having an aggregate price of up to $100,000, from time to time. The

Company reserved 5,000,000 shares of common stock related to the ATM offering. During the three months ended June 30, 2022, the Company did not make any sales under the ATM facility.

On June 15, 2022, the Company entered into a securities purchase agreement for the sale of 2,525,252 shares of the Company's common stock to Pfizer Inc. at $9.90 per share in a registered direct offering conducted without an underwriter or placement agent and pursuant to the Company’s effective shelf registration statement on Form S-3ASR and a related prospectus supplement filed with the SEC. The offering closed on June 17, 2022, for net proceeds of $24,647, after deducting offering costs paid by the Company which were $353.

As of June 30, 2022 and December 31, 2021, there were 37,570,326 and 34,900,727 shares of common stock issued and outstanding, respectively.

The following shares of common stock were reserved for issuance as follows:


	June 30, 2022		December 31, 2021
Options outstanding under the 2018 Stock Option and Grant Plan		1,889,683		2,011,891
Options outstanding under the 2019 Stock Option and Incentive Plan		3,881,675		3,209,203
Warrants to purchase common stock associated with Loan Agreement		36,718		—
Options available for future grant		2,612,856		1,889,299
Warrants available for future grant		146,880		—
Common stock available for ATM program		5,000,000		5,000,000
2019 Employee Stock Purchase Plan		1,199,297		872,429
		14,767,109		12,982,822

Undesignated preferred stock

The Company’s fourth amended and restated certificate of incorporation authorizes the Company to issue up to 10,000,000 shares of undesignated preferred stock, par value $0.0001 per share. There were no undesignated preferred shares issued or outstanding as of June 30, 2022.

Warrants Associated with Loan Agreement

In connection with the entry into the Loan Agreement, the Company issued to Hercules warrants to purchase shares of the Company’s common stock. The amount of shares that may be purchased for the Warrants will not exceed 1.5% multiplied by the greater of Tranche I and the aggregate original amount of the term loan advances, divided by the exercise price of the Warrants. Upon execution of the Loan Agreement, the Company issued 36,718 warrants to purchase shares of the Company’s common stock and recorded the initial warrants at their relative fair value in shareholder's equity.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI https://asc.fasb.org/topic&trid=2208762

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 13
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 18
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-based awards

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Stock-based awards

8. Stock-based awards

2018 Stock option and grant plan

The Company’s 2018 Stock Option and Grant Plan (the “2018 Plan”) provided for the Company to grant incentive stock options or nonqualified stock options, restricted stock awards and other stock-based awards to employees, directors and consultants of the Company. The 2018 Plan was administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions were determined at the discretion of the board of directors, or its committee if so delegated.

The total number of shares of common stock that could have been issued under the 2018 Plan was 3,071,960 shares, of which 107,635 shares remained available for grant on June 18, 2019, the date that the Company’s 2019 Stock Option and Incentive Plan (the “2019 Plan”) became effective. Upon the effectiveness of the 2019 Plan, the 107,635 remaining shares available under the 2018 Plan were transferred and became available for issuance under the 2019 Plan. Shares of common stock underlying outstanding awards under the 2018 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock, expire or are otherwise terminated (other than by exercise) will be added to the shares of common stock available for issuance under the 2019 Plan.

2019 Stock option and incentive plan

The 2019 Plan was adopted and approved by the Company’s board of directors in May 2019 and by the Company’s stockholders in June 2019. The 2019 Plan became effective on June 18, 2019 and replaced the Company’s 2018 Plan on that date. The 2019 Plan allows the board of directors or the compensation committee of the board of directors to make equity-based incentive awards to the Company’s officers, employees, directors or other key persons (including consultants). The number of shares initially reserved for issuance under the 2019 Plan was 2,572,457, which included the 107,635 shares transferred from the 2018 Plan, and shall be cumulatively increased on each January 1 by 4% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s board of directors or compensation committee of the board of directors. The 2019 Plan was increased by 1,389,665 shares on January 1, 2021 and by 1,396,029 shares on January 1, 2022.

The 2019 Plan is administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of stock option may not be greater than ten years. All incentive options granted to any person possessing more than 10% of the total combined voting power of all classes of shares may not have an exercise price of less than 110% of the fair market value of the common stock on the grant date. Stock options granted to employees, officers, members of the board of directors and consultants will typically vest over a four-year period.

Shares that are expired, terminated, surrendered or canceled under the 2019 Plan without having been fully exercised will be available for future awards.

2019 Employee stock purchase plan

The 2019 Employee Stock Purchase Plan (the “2019 ESPP”) was adopted and approved by the Company’s board of directors in May 2019 and by the Company’s stockholders in June 2019. The 2019 ESPP became effective on June 18, 2019, at which time 273,869 shares were reserved for issuance. The 2019 ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2020 and each January 1 through January 1, 2029, by the least of (i) 1% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, (ii) 410,803 shares or (iii) such number of shares as determined by the compensation committee. The 2019 ESPP was increased by 347,416 shares on January 1, 2021 and by 349,007 shares on January 1, 2022.

Stock option valuation

The assumptions that the Company used to determine the grant-date fair value of stock options granted to employees, directors and consultants as follows, presented on a weighted average basis:


	Three Months Ended June 30,						Six Months Ended June 30,
	2022			2021			2022			2021
Expected term (in years)		5.75			5.66			5.77			5.86
Expected volatility		74.24	%		70.43	%		73.10	%		70.43	%
Weighted average risk-free interest rate	2.91		%	1.05		%		1.82	%		0.80	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

Stock options

The following table summarizes the Company’s stock option activity since December 31, 2021:


				Weighted-		Weighted-
				Average		Average		Aggregate
				Exercise		remaining		Intrinsic
	Number			Price per		contractual		Value
	of Options			Share		term (years)		(000's)
Balance outstanding, December 31, 2021		5,221,094		$	15.49		8.20		36,168
Options granted		703,527		$	18.10
Options exercised		(122,208	)	$	1.21
Options cancelled		(31,055	)	$	22.16
Balance outstanding, June 30, 2022		5,771,358		$	16.07		7.87	$	10,986
Vested and expected to vest, June 30, 2022		5,189,977		$	15.49		7.75	$	10,986
Exercisable, June 30, 2022		2,719,542		$	11.91		7.08	$	9,145

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock.

The weighted average grant-date fair value per share of stock options granted during the three months ended June 30, 2022 and 2021 was $8.67 and $16.49, respectively. Additionally, the weighted average grant-date fair value per share of stock options granted during the six months ended June 30, 2022 and 2021 was $18.10 and $16.27, respectively.

Awards with performance-based vesting conditions granted under the 2019 Plan

In December 2021, the Company granted 610,546 stock options to management at an exercise price of $21.10, which vest upon the achievement on or before December 31, 2022 of three pre-determined milestones regarding progress related to the HARMONY study, progress related to the SYMMETRY study, and progress related to availability of drug product for use in Phase 3 clinical trials. One-third of the options vest upon achievement of each of the milestones. In January 2022, the Company granted an additional 248,376 stock options to Company employees with the same performance-based milestones and vesting terms at an exercise price of $21.70. During the three months ended June 30, 2022, the Company determined that it was probable that one of the milestones would be achieved and consequently recognized $911 of related stock compensation expense. In July 2022, the Company determined a second milestone was probable of being achieved and will begin recognizing stock compensation expense in the third quarter of 2022.

Stock-based compensation

The following table summarizes the Company’s stock-based compensation expense during the three and six months ended June 30, 2022 and 2021:


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Classified within research and development expense	$	1,474	$	734	$	2,585	$	1,453
Classified within general and administrative expense		2,687		1,702		4,887		3,347
Total stock-based compensation expense	$	4,161	$	2,436	$	7,472	$	4,800

As of June 30, 2022, total unrecognized compensation cost related to unvested stock options was $36,635, including performance-based awards with unrecognized compensation costs of $10,021. These unvested stock options are expected to be recognized over a weighted average period of 1.78 years.

Amgen license agreement

6 Months Ended

Jun. 30, 2022

Amgen license agreement

Amgen license agreement

. Amgen license agreement

In June 2018, the Company entered into a license agreement (the “Amgen Agreement”) with Amgen, Inc. (“Amgen”) pursuant to which the Company was granted an exclusive license to certain patents and intellectual property related to a long-acting FGF21 analog in order to commercially develop, manufacture, use and distribute FGF21 as a treatment for NASH and other serious metabolic diseases. The Amgen Agreement provides the Company with exclusive global rights to the licensed products and the right to grant sublicenses that cover EFX to third parties.

In exchange for these rights, the Company made an upfront payment of $5,000 and issued 2,653,333 shares of Series A Preferred Stock with a fair value of $1,353 to Amgen. Amgen was also entitled to maintain a 10% ownership interest of the outstanding shares of the Company’s common stock, on a fully diluted and converted basis, through the second closing of the Company’s Series A Preferred Stock financing. In November 2018, in connection with the second closing of the Company’s Series A Preferred Stock financing, the Company issued 3,205,128 shares of Series A Preferred Stock to Amgen for a total value of $7,404, satisfying its anti-dilution obligation under the Amgen Agreement.

Under the Amgen Agreement, the Company made a milestone payment in the third quarter of 2019 of $2,500 in connection with dosing the first patient in the BALANCED study and is obligated to pay Amgen $7,500 in connection with dosing the first patient in a Phase 3 clinical trial, up to $30,000 in connection with marketing approvals, and aggregate milestone payments of up to $75,000 upon the achievement of specified commercial milestones for all products licensed under the Amgen Agreement.

Under the Amgen Agreement, the Company is obligated to pay Amgen tiered royalties ranging from a low to high single-digit percentages on annual net sales of the licensed products, beginning on the first commercial sale of such licensed products in each country and expiring on a country-by-country basis on the latest of (i) the expiration of the last valid patent claim covering such licensed products in such country, (ii) the loss of regulatory exclusivity in such country, and (iii) ten years after the first commercial sale of such licensed product in such country. The royalty payments are subject to reduction under specified conditions set forth in the Amgen Agreement.

The Company is solely responsible for all development, manufacturing, and commercial activities and costs of the licensed products, including clinical studies or other tests necessary to support the use of a licensed product. The Company is also responsible for costs related to the filing, prosecution and maintenance of the licensed patent rights.

The Amgen Agreement will remain in effect until the expiration of the royalty term in all countries for all licensed products. The Amgen Agreement may be terminated by either party with at least 90 days' notice in the event of material breach by the other party that remains uncured for 90 days, by either party for insolvency or bankruptcy of the

other party and immediately by Amgen if the Company challenges the licensed patents. The Company may also terminate the Amgen Agreement with 90 days' written notice for discretionary reasons such as scientific, technical, regulatory or commercial issues, as defined in the Amgen Agreement.

During the three and six months ended June 30, 2022 and 2021, the Company did not record any research and development expense in connection with the Amgen Agreement.

Income taxes

6 Months Ended

Jun. 30, 2022

Income Tax Disclosure [Abstract]

Income taxes

10. Income taxes

During the three and six months ended June 30, 2022 and 2021, the Company did not record any income tax benefits for the net operating losses incurred or for the research and development tax credits generated in each period due to its uncertainty of realizing a benefit from those items. All of the Company’s operating losses since inception have been generated in the United States.

On March 27, 2020, the Coronavirus Aid, Relief and Economic Security (CARES) Act, (the “Act”) was signed into law. The Act includes provisions relating to refundable payroll tax credits, deferment of the employer portion of certain payroll taxes, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. The Company analyzed the provisions of the Act and determined there was no significant impact to its income tax provision for the three and six months ended June 30, 2022.

On June 29, 2020, California Assembly Bill 85 ("AB85") was signed into law. AB85, which includes several tax measures, provides for a three-year suspension of the use of net operating losses for medium and large businesses and a three-year cap on the use of business incentive tax credits to offset no more than $5 million of tax per year. Generally, AB85 suspends the use of net operating losses for taxable years 2020, 2021 and 2022 for taxpayers with taxable income of $1 million or more. Since the Company is not expected to generate California source taxable income of more than $1 million during these periods, no material impact is anticipated at this time.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Net loss per share

6 Months Ended

Jun. 30, 2022

Earnings Per Share [Abstract]

Net loss per share

11. Net loss per share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
	2022			2021			2022			2021
Numerator:
Net loss	$	(27,403	)	$	(28,933	)	$	(53,432	)	$	(44,023	)
Denominator:
Weighted average common shares outstanding, basic and diluted		35,383,685			34,814,631			35,195,638			34,779,647
Net loss per share, basic and diluted	$	(0.77	)	$	(0.83	)	$	(1.52	)	$	(1.27	)

The Company excluded nil shares and 8,963 shares of restricted common stock, presented on a weighted average basis, from the calculations of basic net loss per share for the three months ended June 30, 2022 and 2021, respectively, because those shares had not vested. The Company excluded nil shares and 16,367 shares of restricted common stock, presented on a weighted average basis, from the calculations of basic net loss per share for the six months ended June 30, 2022 and 2021, respectively, because those shares had not vested.

The Company’s potentially dilutive securities, which include stock options, warrants and unvested restricted common stock, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both

basic and diluted net loss per share is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:


	Three and six months ended June 30,
	2022		2021
Options to purchase common stock		5,771,358		3,962,372
Warrants to purchase common stock		36,718		—
Warrants available for future grant		146,880		—
Unvested restricted common stock		—		3,836
		5,954,956		3,966,208

Commitments and contingencies

6 Months Ended

Jun. 30, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and contingencies

12. Commitments and contingencies

COVID-19 Pandemic

In December 2019, a novel strain of coronavirus (“COVID-19”) was reported to have surfaced in Wuhan, China and subsequently spread to other countries, including Europe and the United States, and was declared a pandemic by the World Health Organization. Despite progress with distribution and administration of vaccines, COVID-19 and its effects continue to evolve and countries including the United States, Europe and Asia continue to respond by implementing restrictions such as travel restrictions, social distancing requirements, stay-at-home orders and delayed commencement of non-COVID-19-related clinical trials. The Company’s financial results for the three and six months ended June 30, 2022 and 2021 were not significantly impacted by COVID-19, however, the Company cannot at this time predict the specific extent, duration, or full impact that the ongoing COVID-19 pandemic will have on its financial condition, operations, and business plans for 2022, including the timing and enrollment of patients in its planned clinical trials and other expected milestones of its product candidate.

Operating lease

In February 2020, the Company entered into a seven-year agreement to occupy 6,647 square feet of office space in South San Francisco, California. The lease commenced on July 10, 2020 when the Company took occupancy of the leased space and the lease was determined to be operating classified. Under the agreement, the Company is required to make approximately $2,300 in total minimum payments during the term. The Company is also required to pay its proportionate share of building operating and tax costs after the first year under lease which are not included in the measurement of the lease and treated as variable lease cost and expensed when incurred.

As of June 30, 2022, maturities of the Company’s operating lease liability was as follows:


2022 (remaining)	$	158
2023		321
2024		331
2025		341
2026		351
2027		208
Total future minimum lease payments		1,710
Less imputed interest		(293	)
Present value of operating lease liabilities	$	1,417

As of June 30, 2022, the total lease liability was $1,417, of which $1,199 was noncurrent and $218 was short-term and classified within “Accrued expenses and other current liabilities” on the condensed consolidated balance sheet.

For the three and six months ended June 30, 2022 and 2021, the components of operating lease cost were as follows:


		Three Months Ended June 30,								Six Months Ended June 30,
			2022				2021				2022				2021
Lease cost:	Statement of Operations Classification:
Operating lease cost	General and administrative expense	$		81		$		81		$		162		$		162
Short-term lease cost	General and administrative expense			—				—				29				—
Variable operating lease cost	General and administrative expense			31				—				43				—
Total operating lease cost		$		112		$		81		$		234		$		162

Other information:
Cash paid for amounts included in the measurement of operating lease liability		$		77				75		$		154		$		150
Weighted average remaining lease term				5.1				6.1				5.1				6.1
Weighted average discount rate				7.6	%			7.6	%			7.6	%			7.6	%

Research and manufacturing and other commitments

The Company has entered into agreements with contract research organizations and contract manufacturing organizations to provide services in connection with its nonclinical studies and clinical trials and to manufacture clinical development materials. As of June 30, 2022, the Company had non-cancelable purchase and other commitments under these agreements totaling $6,957.

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 its executive officers 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 currently aware of any indemnification claims and has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of June 30, 2022.

Legal proceedings

The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings.

Subsequent event

6 Months Ended

Jun. 30, 2022

Subsequent Events [Abstract]

Subsequent event

13. Subsequent event

The Company evaluated subsequent events through August 5, 2022, the date on which these financial statements were issued. Based on this evaluation, it was determined that no subsequent events occurred that require recognition or disclosure in its financial statements for the three months and six months ended June 30, 2022.

Summary of significant accounting policies (Policies)	6 Months Ended
Summary of significant accounting policies (Policies)	Jun. 30, 2022
Accounting Policies [Abstract]
Unaudited interim financial statements	Unaudited interim financial statements The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in accordance with GAAP for interim financial reporting and as required by Regulation S-X, Rule 10-01. The unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the Company’s condensed consolidated balance sheet as of June 30, 2022, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2022 and 2021, the condensed consolidated statement of stockholders’ equity (deficit) as of June 30, 2022 and the condensed consolidated statements of cash flows for the six months ended June 30, 2022. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2022 and 2021 are unaudited. The results for the three and six months ended June 30, 2022 are not necessarily indicative of results to be expected for the year ending December 31, 2022, any other interim periods, or any future year or period.
Use of estimates	Use of estimates The preparation of the Company's condensed consolidated 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 condensed consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the recognition of research and development expenses, stock-based compensation expense, warrant liabilities and the valuation allowance for deferred tax assets. 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 when there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments with original maturities of three months or less at the time of purchase to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts.
Short-term marketable securities	Short-term marketable securities The Company invests in short-term marketable securities, primarily money market funds, commercial paper, U.S. treasury securities and corporate debt securities. The Company continually evaluates the credit ratings of its investment portfolio and underlying securities. The Company invests in accordance with its investment policy and invests at the date of purchase in securities with high ratings from top rating agencies. The Company classifies its short-term marketable securities as available-for-sale securities and reports them at fair value in short-term marketable securities on the condensed consolidated balance sheets with related unrealized gains and losses included within accumulated other comprehensive gain (loss) on the condensed consolidated balance sheets. The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in other income on the condensed consolidated statements of operations and comprehensive loss. When the fair value is below the amortized cost of a marketable security, the Company reviews and determines whether the impairment is due to credit-related factors or noncredit-related factors. The credit-related impairment amount is recognized in other income on the condensed consolidated statements of operations and comprehensive loss, with a corresponding allowance for credit losses account in the condensed consolidated balance sheet. Subsequent improvements in expected credit losses are recognized as a reversal of an amount in the allowance account. If the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis, then the allowance for the credit loss is written-off and the excess of the amortized cost basis of the asset over its fair value is recorded in the condensed consolidated statements of operations. There were no credit losses recorded during the periods ended June 30, 2022 and December 31, 2021.
Restricted cash	Restricted cash As of June 30, 2022 and December 31, 2021, the Company was required to maintain a separate cash balance of $108 for the benefit of the landlord in connection with the Company’s Gateway office space lease in South San Francisco, California (the “Gateway Lease”), which is classified within other assets (non-current) on the condensed consolidated balance sheets (see Note 12).
Concentrations of credit risk	Concentrations of credit risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and short-term marketable securities. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company deposits its cash investments in financial institutions that it believes have high credit quality and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. At June 30, 2022 and December 31, 2021, all of the Company's cash, cash equivalents and short-term investments were held at one accredited financial institution.
Leases	Leases The Company determines whether an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether the Company has the right to control the identified asset. Right-of-use, or ROU, assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement date based on the present value of future lease payments over the lease term. ROU assets are based on the measurement of the lease liability and are further adjusted by any lease payments made prior to or on lease commencement, lease incentives received and initial direct costs incurred, as applicable. The Company has elected to not recognize leases with a lease term of one year or less on its balance sheet. Operating lease costs included in the measurement of the lease are recognized on a straight-line basis over the lease term. Variable lease costs are expensed as incurred as an operating expense. The Company determines the lease classification and the present value of future lease payments at the time of the lease commencement using an incremental borrowing rate that it estimates based upon the Company’s credit risk and term of the lease. The interest rate implicit in lease contracts has not historically been readily determinable and the Company must therefore use the appropriate incremental borrowing rate to measure its leases. To estimate the incremental borrowing rate, a credit rating applicable to the Company is estimated using a synthetic credit rating analysis since the Company does not currently have a rating agency-based credit rating.
Research and development costs	Research and development costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred to discover, research and develop drug candidates, including personnel expenses, stock-based compensation expense, third-party license fees and external costs including fees paid to consultants, contract manufacturing organizations, or CMOs, and clinical research organizations, or CROs, in connection with drug product manufacturing, nonclinical studies and clinical trials, and other related clinical trial fees, such as for investigator grants, patient screening, laboratory work, clinical trial database management, clinical trial material management and statistical compilation and analysis. Non-refundable prepayments for goods or services that will be used or rendered for future research and development activities are recorded as prepaid expenses. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered. Costs incurred in obtaining technology licenses are charged immediately to research and development expense if the technology licensed has not reached technological feasibility and has no alternative future uses.
Research contract costs and accruals	Research contract costs and accruals The Company has entered into various research and development and other agreements with commercial firms, researchers and others for provisions of goods and services. These agreements are generally cancelable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company's estimates.
Stock-based compensation	Stock-based compensation The Company measures all stock-based awards granted to employees and nonemployees based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company recognizes stock-based compensation expense for awards that contain performance-based conditions using the accelerated attribution method when management determines it is probable that the performance condition will be satisfied. The Company accounts for forfeitures as they occur. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which requires inputs based on certain subjective assumptions, including the expected stock price volatility, the expected term of the option, the risk-free interest rate for a period that approximates the expected term of the option, and the Company's expected dividend yield. The Company went public in June 2019 and accordingly, lacks sufficient company-specific historical and implied volatility information for its shares traded in the public markets. Therefore, it estimates its expected share price volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded share price. The expected term of the Company's stock options has been determined utilizing the "simplified" method for awards that qualify as "plain-vanilla" options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future. The fair value of each common stock award is estimated on the date of grant based on the fair value of the Company's common stock on that same date. Compensation expense for purchases under the Employee Stock Purchase Plan is recognized based on the fair value of the common stock estimated based on the closing price of our common stock as reported on the date of offering, less the purchase discount percentage provided for in the plan. The Company classifies stock-based compensation expense in its condensed consolidated statement of operations and comprehensive loss in the same manner in which the award recipient's payroll costs are classified or in which the award recipient's service payments are classified.
Loan Payable	Loan Payable The Company initially reviews loan payables to identify the units of account for recognition purposes. The Company identifies the units of account by identifying each freestanding financial instrument included in the debt arrangement. For freestanding equity-linked financial instruments that are not in the form of shares, liability classification is used if the instrument embodies an obligation to repurchase the Company’s shares that may require the use of cash or other assets or the instrument may require the issuance of a variable number of the Company’s shares with a monetary value that is predominately based on a fixed value, based on variations in variables other than the fair value of the Company’s stock, or based on variations inversely related to the fair value of the Company’s stock. The Company will then review for embedded features within the debt instrument to evaluate whether the embedded features require bifurcation from the debt host instrument. Embedded features typically include conversion or exchange features, redemption features, or other embedded features. The identified embedded feature is bifurcated from the debt host instrument if the criteria in ASC 815-15-25-1 are met. Debt arrangements are classified on the consolidated balance sheet as current if the obligation of the debt arrangement is reasonably expected to be liquidated within 12 months. Loan payable is recorded net of debt discount which comprises issuance costs, customary closing and end of term charge or final fees, and the fair value of additional warrants issued in conjunction with the loan payable. Debt discount is amortized over the term of the loan payable using the effective interest method, and is recorded to interest expense on the consolidated statements of operations (see Note 6).
Warrant Liabilities	Warrant Liabilities The Company accounts for warrants anticipated to be issued in the future under the Loan Agreement as liabilities and measures them at fair value using the Black-Scholes valuation model. The warrants are subject to remeasurement at each prospective balance sheet date, with any changes in the fair value recorded in the consolidated statements of operations.
Comprehensive loss	Comprehensive loss Comprehensive loss includes net loss as well as other changes in stockholders' equity (deficit) that result from transactions and economic events other than those with stockholders. The Company’s comprehensive loss is comprised of net loss and changes in unrealized gains and losses on its short-term marketable securities.
Recently issued accounting pronouncements and pronouncements not yet adopted	Recently adopted accounting pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) ("ASU 2016-13"), which introduced a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The Company adopted ASU 2016-03 as of January 1, 2021. For available-for-sale debt securities with unrealized losses, those losses are recognized as allowances rather than reductions in the amortized cost of the underlying security. The adoption of ASU 2016-03 did not have a material impact on the Company's condensed consolidated financial statements. In August 2020, the FASB issued ASU No. 2020-06, “Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity”, or ASU 2020-06. ASU 2020-06 simplifies the accounting for convertible instruments by eliminating the requirement to separate embedded conversion features from the host contract when the conversion features are not required to be accounted for as derivatives under Topic 815, Derivatives and Hedging, or that do not result in substantial premiums accounted for as paid-in capital. The Company adopted ASU 2020-06 on January 1, 2022, on a modified retrospective basis. The adoption of ASU 2020-06 did not have a material impact on the Company's condensed consolidated financial statements.

Fair value of financial assets and liabilities (Tables)

6 Months Ended

Jun. 30, 2022

Fair Value Disclosures [Abstract]

Summary of assets and liabilities measured at fair value on a recurring basis

The following is a summary of our financial assets and liabilities measured at fair value on a recurring basis as of June 30, 2022 and December 31, 2021:


	June 30, 2022
	Total		Level 1		Level 2		Level 3
Money market funds	$	151,791	$	151,791	$	—	$	—
Corporate debt securities		2,998		—		2,998		—
Total assets	$	154,789	$	151,791	$	2,998	$	—

Warrant liabilities	$	41	$	—	$	—	$	41
Total liabilities	$	41	$	—	$	—	$	41

	December 31, 2021
	Total		Level 1		Level 2		Level 3
Money market funds	$	116,261	$	116,261	$	—	$	—
Corporate debt securities		37,775		—		37,775		—
	$	154,036	$	116,261	$	37,775	$	—

Short-term marketable securities (Tables)

6 Months Ended

Jun. 30, 2022

Short-term marketable securities

Summary of short-term marketable securities

The following is a summary of short-term marketable securities as of June 30, 2022 and December 31, 2021:


	June 30, 2022
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Credit losses		Fair value
Money market funds	$	151,791	$	—	$	—		$	—	$	151,791
Corporate debt securities		3,001		—		(3	)		—		2,998
	$	154,792	$	—	$	(3	)	$	—	$	154,789

Cash equivalents										$	151,791
Short-term marketable securities											2,998
										$	154,789

	December 31, 2021
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Credit losses		Fair value
Money market funds	$	116,261	$	—	$	—		$	—	$	116,261
Corporate debt securities		37,802		—		(27	)		—		37,775
	$	154,063	$	—	$	(27	)	$	—	$	154,036

Cash equivalents										$	116,261
Short-term marketable securities											37,775
										$	154,036

Accrued expenses and other current liabilities (Tables)

6 Months Ended

Jun. 30, 2022

Accrued expenses and other current liabilities

Schedule of accrued expenses and other current liabilities

The following is a summary of accrued expenses and other current liabilities as of June 30, 2022 and December 31, 2021:


	June 30, 2022		December 31, 2021
Accrued external research and development expenses	$	16,847	$	17,539
Accrued employee compensation and benefits		1,910		554
Accrued legal and professional fees		808		124
Short-term lease liability and other		255		205
	$	19,820	$	18,422

Loan Payable and Warrant Liability (Tables)

6 Months Ended

Jun. 30, 2022

Debt Disclosure [Abstract]

Schedule of Future principal Debt Payments on Loan Payable

Future principal debt payments on the currently outstanding loan payable as of June 30, 2022 are as follows (in thousands):


2022	$	—
2023		—
2024		1,764
2025		3,763
2026		4,096
2027		377
Total principal outstanding		10,000
End of term charge		1,170
Total principal outstanding and end of term charge		11,170
Unamortized discount and issuance costs		(1,804	)
Loan Payable - noncurrent	$	9,366

Schedule of Assumptions Used to Determine Estimated Fair Value of Warrant

The Company estimated the fair value of the Warrant using the Black-Scholes model based on the following key assumptions:


	Three months ended June 30, 2022
Expected term (in years)		7.00
Expected volatility		76.15	%
Weighted average risk-free interest rate		3.39	%
Expected dividend yield		0.00	%

Stockholder's equity (deficit) (Tables)

6 Months Ended

Jun. 30, 2022

Stockholders' Equity Note [Abstract]

Schedule of common stock reserved for issuance

The following shares of common stock were reserved for issuance as follows:


	June 30, 2022		December 31, 2021
Options outstanding under the 2018 Stock Option and Grant Plan		1,889,683		2,011,891
Options outstanding under the 2019 Stock Option and Incentive Plan		3,881,675		3,209,203
Warrants to purchase common stock associated with Loan Agreement		36,718		—
Options available for future grant		2,612,856		1,889,299
Warrants available for future grant		146,880		—
Common stock available for ATM program		5,000,000		5,000,000
2019 Employee Stock Purchase Plan		1,199,297		872,429
		14,767,109		12,982,822

Stock-based awards (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of assumptions used to determine grant-date fair value of stock options granted

The assumptions that the Company used to determine the grant-date fair value of stock options granted to employees, directors and consultants as follows, presented on a weighted average basis:


	Three Months Ended June 30,						Six Months Ended June 30,
	2022			2021			2022			2021
Expected term (in years)		5.75			5.66			5.77			5.86
Expected volatility		74.24	%		70.43	%		73.10	%		70.43	%
Weighted average risk-free interest rate	2.91		%	1.05		%		1.82	%		0.80	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

Summary of stock option activity

The following table summarizes the Company’s stock option activity since December 31, 2021:


				Weighted-		Weighted-
				Average		Average		Aggregate
				Exercise		remaining		Intrinsic
	Number			Price per		contractual		Value
	of Options			Share		term (years)		(000's)
Balance outstanding, December 31, 2021		5,221,094		$	15.49		8.20		36,168
Options granted		703,527		$	18.10
Options exercised		(122,208	)	$	1.21
Options cancelled		(31,055	)	$	22.16
Balance outstanding, June 30, 2022		5,771,358		$	16.07		7.87	$	10,986
Vested and expected to vest, June 30, 2022		5,189,977		$	15.49		7.75	$	10,986
Exercisable, June 30, 2022		2,719,542		$	11.91		7.08	$	9,145

Summary of stock-based compensation expense

The following table summarizes the Company’s stock-based compensation expense during the three and six months ended June 30, 2022 and 2021:


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Classified within research and development expense	$	1,474	$	734	$	2,585	$	1,453
Classified within general and administrative expense		2,687		1,702		4,887		3,347
Total stock-based compensation expense	$	4,161	$	2,436	$	7,472	$	4,800

Net loss per share (Tables)

6 Months Ended

Jun. 30, 2022

Earnings Per Share [Abstract]

Schedule of basic and diluted net loss per share attributable to common stockholders

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
	2022			2021			2022			2021
Numerator:
Net loss	$	(27,403	)	$	(28,933	)	$	(53,432	)	$	(44,023	)
Denominator:
Weighted average common shares outstanding, basic and diluted		35,383,685			34,814,631			35,195,638			34,779,647
Net loss per share, basic and diluted	$	(0.77	)	$	(0.83	)	$	(1.52	)	$	(1.27	)

Schedule of computation of diluted net loss per share attributable to common stockholders


	Three and six months ended June 30,
	2022		2021
Options to purchase common stock		5,771,358		3,962,372
Warrants to purchase common stock		36,718		—
Warrants available for future grant		146,880		—
Unvested restricted common stock		—		3,836
		5,954,956		3,966,208

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2022

Commitments and Contingencies Disclosure [Abstract]

Schedule of maturity of the Company's operating lease liabilities


2022 (remaining)	$	158
2023		321
2024		331
2025		341
2026		351
2027		208
Total future minimum lease payments		1,710
Less imputed interest		(293	)
Present value of operating lease liabilities	$	1,417

Schedule of components of operating lease expense


		Three Months Ended June 30,								Six Months Ended June 30,
			2022				2021				2022				2021
Lease cost:	Statement of Operations Classification:
Operating lease cost	General and administrative expense	$		81		$		81		$		162		$		162
Short-term lease cost	General and administrative expense			—				—				29				—
Variable operating lease cost	General and administrative expense			31				—				43				—
Total operating lease cost		$		112		$		81		$		234		$		162

Other information:
Cash paid for amounts included in the measurement of operating lease liability		$		77				75		$		154		$		150
Weighted average remaining lease term				5.1				6.1				5.1				6.1
Weighted average discount rate				7.6	%			7.6	%			7.6	%			7.6	%

Nature of the business and basis of presentation (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ 27,403	$ 26,029	$ 28,933	$ 15,090	$ 53,432	$ 44,023	$ 100,777	$ 79,207
Accumulated deficit	363,736				363,736		$ 310,304
Cash, cash equivalents and short-term marketable securities	$ 180,725				$ 180,725

- Definition

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

+ References

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+ Details

Summary of significant accounting policies - Restricted cash (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Separate cash balance for the landlord	$ 108	$ 108

Fair value of financial assets and liabilities - Recurring (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 154,789	$ 154,036
Liabilities	41
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	151,791	116,261
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	2,998	37,775
Warrant liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	41
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	151,791	116,261
Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	151,791	116,261
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	2,998	37,775
Level 2 \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	2,998	$ 37,775
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	41
Level 3 \| Warrant liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	$ 41

Fair value of financial assets and liabilities - Textual (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers into level 3 Assets	$ 0	$ 0
Transfers out of level 3 Assets	0	0
Transfers into level 3 liabilities	0	0
Transfers out of level 3 liabilities	$ 0	$ 0

Short-term marketable securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	$ 154,792	$ 154,063
Gross unrealized losses	(3)	(27)
Fair value	154,789	154,036
Cash equivalents	151,791	116,261
Short-term marketable securities	2,998	37,775
Total	154,789	154,036
Money market funds
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	151,791	116,261
Fair value	151,791	116,261
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	3,001	37,802
Gross unrealized losses	(3)	(27)
Fair value	$ 2,998	$ 37,775

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Accrued expenses and other current liabilities
Accrued external research and development expenses	$ 16,847	$ 17,539
Accrued employee compensation and benefits	1,910	554
Accrued legal and professional fees	808	124
Short-term lease liability and other	255	205
Total accrued expenses and other current liabilities	$ 19,820	$ 18,422

Loan Payable and Warrant Liability - Textual (Details)		6 Months Ended
Loan Payable and Warrant Liability - Textual (Details)	Jun. 15, 2022 USD ($) Tranche	Jun. 30, 2022 USD ($) $ / shares shares	Dec. 31, 2021 $ / shares
Debt Instrument [Line Items]
Proceeds from term loan		$ 10,000,000
Amortization of debt issuance costs and discount		$ 16,000
Common stock, par value (in dollars per share) \| $ / shares		$ 0.0001	$ 0.0001
Loan Agreement
Debt Instrument [Line Items]
End of term charge of outstanding principal balance, in percentage	5.85%
Amortization of debt issuance costs and discount	$ 1,170,000
Issued warrants to purchase shares of common stock \| shares		36,718
Recognized initial warrants at relative fair value		$ 227,000
Additional remaining warrants were recognized at relative fair value at closing of agreement		41,000
Fair value associated with equity and liability classified warrants		$ 268,000
Loan Agreement \| First Twelve Months After Closing
Debt Instrument [Line Items]
Percentage of prepayment charge of outstanding principal balance	3.00%
Loan Agreement \| Second Twelve Months After Closing
Debt Instrument [Line Items]
Percentage of prepayment charge of outstanding principal balance	2.00%
Loan Agreement \| Thereafter
Debt Instrument [Line Items]
Percentage of prepayment charge of outstanding principal balance	1.00%
Loan Agreement \| Term Loan \| Hercules Capital, Inc
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 100,000,000
Number of tranches available for loan \| Tranche	4
Proceeds from term loan	$ 10,000,000
Term loan, description		Under the terms of the Loan Agreement, the Company received $10,000 upon closing and an additional $10,000 is available to the Company at its sole discretion. The second tranche of the Term Loan, consisting of up to an additional $15,000, will become available to the Company subject to the Company's achievement of certain clinical development milestones. The third tranche of the Term Loan, consisting of up to an additional $20,000, will become available to the Company upon the achievement of certain clinical and financial milestones. The fourth tranche of the Term Loan, consisting of up to an additional $45,000, will become available to the Company at Hercules sole discretion.
Maturity date	Jan. 01, 2027
Variable annual rate	7.65%
Loan Agreement \| Term Loan \| Hercules Capital, Inc \| Prime Rate
Debt Instrument [Line Items]
Variable annual rate	3.65%
Loan Agreement \| Term Loan First Tranche
Debt Instrument [Line Items]
Additional loan advances available		$ 10,000,000
Loan Agreement \| Term Loan First Tranche \| Hercules Capital, Inc
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 10,000,000
Loan Agreement \| Term Loan Second Tranche \| Hercules Capital, Inc
Debt Instrument [Line Items]
Maximum borrowing capacity	15,000,000
Loan Agreement \| Term Loan Third Tranche \| Hercules Capital, Inc
Debt Instrument [Line Items]
Maximum borrowing capacity	20,000,000
Loan Agreement \| Term Loan Fourth Tranche \| Hercules Capital, Inc
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 45,000,000
Warrants to Purchase Common Stock \| Loan Agreement \| Term Loan \| Hercules Capital, Inc
Debt Instrument [Line Items]
Common stock, par value (in dollars per share) \| $ / shares		$ 0.0001
Maximum percentage of warrants purchased		1.50%

Loan Payable and Warrant Liability - Schedule of Future principal Debt Payments on Loan Payable (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Long-Term Debt, Fiscal Year Maturity [Abstract]
2024	$ 1,764
2025	3,763
2026	4,096
2027	377
Total principal outstanding	10,000
End of term charge	1,170
Total principal outstanding and end of term charge	11,170
Unamortized discount and issuance costs	(1,804)
Loan Payable - noncurrent	$ 9,366

Loan Payable and Warrant Liability - Schedule of Assumptions Used to Determine Estimated Fair Value of Warrant (Details)	Jun. 30, 2022
Measurement Input, Expected Term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (in years)	7 years
Measurement Input, Price Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of the Warrants, Measurement input	0.7615
Measurement Input, Weighted Average Risk-Free Interest Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of the Warrants, Measurement input	0.0339
Measurement Input, Expected Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of the Warrants, Measurement input	0.0000

Stockholder's equity (deficit) - Common stock (Details)						3 Months Ended	6 Months Ended
Stockholder's equity (deficit) - Common stock (Details)	Jun. 17, 2022 USD ($)	Jun. 15, 2022 $ / shares shares	May 18, 2021 USD ($) shares	Jul. 10, 2020 USD ($) $ / shares shares	Jun. 24, 2019 USD ($) $ / shares shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2022 USD ($) Vote $ / shares shares	Dec. 31, 2021 $ / shares shares	Jun. 18, 2019 shares
Class of Stock [Line Items]
Common stock, shares authorized						150,000,000	150,000,000	150,000,000
Common stock, par value (in dollars per share) \| $ / shares						$ 0.0001	$ 0.0001	$ 0.0001
Number of votes per share \| Vote							1
Cash dividend declared \| $ / shares							$ 0
Cash dividend paid \| $ / shares							$ 0
Proceeds received, net of underwriting discounts and commissions \| $							$ 25,000,000
Share Issued value under agreement \| $						$ 24,647,000
Common stock, shares issued						37,570,326	37,570,326	34,900,727
Common stock, shares outstanding						37,570,326	37,570,326	34,900,727
Common stock were reserved for issuance
Options available for future grant						14,767,109	14,767,109	12,982,822
Options available for future grant
Common stock were reserved for issuance
Options available for future grant						2,612,856	2,612,856	1,889,299
Common stock Available under ATM Offering
Class of Stock [Line Items]
Proceeds received, net of underwriting discounts and commissions \| $	$ 24,647,000
Offering costs \| $	$ 353,000
Sale of stock under agreement						0
Common stock were reserved for issuance
Options available for future grant			5,000,000			5,000,000	5,000,000	5,000,000
Common stock Available under ATM Offering \| Pfizer Inc
Class of Stock [Line Items]
Sale of stock under agreement		2,525,252
Sale of stock, price per share \| $ / shares		$ 9.90
Warrants to Purchase Common Stock
Common stock were reserved for issuance
Options available for future grant						36,718	36,718
Warrants Available for Future Grant
Common stock were reserved for issuance
Options available for future grant						146,880	146,880
2018 Stock option and grant plan
Common stock were reserved for issuance
Options available for future grant						1,889,683	1,889,683	2,011,891	107,635
2019 Stock Option and Incentive plan
Common stock were reserved for issuance
Options available for future grant						3,881,675	3,881,675	3,209,203
2019 Employee Stock Purchase Plan
Common stock were reserved for issuance
Options available for future grant						1,199,297	1,199,297	872,429
Maximum \| Common stock Available under ATM Offering
Class of Stock [Line Items]
Share Issued value under agreement \| $			$ 100,000
IPO
Class of Stock [Line Items]
Public offering price \| $ / shares					$ 16.00
Proceeds received, net of underwriting discounts and commissions \| $					$ 98,394,000
Offering costs \| $					$ 2,942,000
Number of shares converted					21,056,136
Common stock, shares issued					6,612,500
Follow Up Public Offering
Class of Stock [Line Items]
Share Issued under agreement				6,012,390
Public offering price \| $ / shares				$ 36.00
Proceeds received, net of underwriting discounts and commissions \| $				$ 203,460,000
Offering costs \| $				$ 906,000
Over allotment \| Maximum
Class of Stock [Line Items]
Share Issued under agreement				784,224
Common stock, shares issued					862,500

Stockholder's equity (deficit) - Undesignated preferred stock and Restricted common stock (Details) - Undesignated Preferred Stock	Jun. 30, 2022 $ / shares shares
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.0001
Preferred stock, shares issued	0
Preferred stock, shares outstanding	0
Maximum
Class of Stock [Line Items]
Preferred stock, shares authorized	10,000,000

Stockholder's equity (deficit) - Warrants Associated with Loan Agreement (Details) - Hercules Capital Inc and Hercules Private Global Venture Growth Fund I L.P.	6 Months Ended
	Jun. 30, 2022 shares
Class of Stock [Line Items]
Maximum percentage of warrants purchased	1.50%
Issued warrants to purchase shares of common stock	36,718

Stock-based awards - Textual (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 18, 2019	Jan. 31, 2022	Jun. 30, 2019	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Jan. 31, 2021
Share-based awards
Number of shares remained available for grant				14,767,109		14,767,109		12,982,822
Weighted average grant-date fair value per share of stock options granted				$ 8.67	$ 16.49	$ 18.10	$ 16.27
Stock options granted ( in shares)						703,527
Exercise price						$ 18.10
Stock compensation expense				$ 4,161	$ 2,436	$ 7,472	$ 4,800
Total unrecognized compensation cost related to unvested stock-based awards				36,635		$ 36,635
Weighted average period of recognition for unrecognized compensation cost						1 year 9 months 10 days
Performance Shares
Share-based awards
Stock options granted ( in shares)								610,546
Additional stock options granted (in shares)		248,376
Exercise price		$ 21.70						$ 21.10
Stock compensation expense				911
Total unrecognized compensation cost related to unvested stock-based awards				$ 10,021		$ 10,021
Options vesting description						One-third of the options vest upon achievement of each of the milestones.
2018 Stock option and grant plan
Share-based awards
Number of shares of common stock issued	3,071,960
Number of shares remained available for grant	107,635			1,889,683		1,889,683		2,011,891
2019 Stock option and incentive plan
Share-based awards
Number of shares remained available for grant	107,635
Number of shares initially reserved for issuance			2,572,457
Number of additional shares reserved for issuance		1,396,029							1,389,665
Percent of shares reserved and available for issuance automatically increase annually on January 1			4.00%
Percentage of exercise price per share of stock options			100.00%
Percentage of minimum exercise price, holding more than 10% of voting power			110.00%
Stock options vesting period			4 years
2019 Employee stock purchase plan
Share-based awards
Number of shares initially reserved for issuance	273,869
Number of additional shares reserved for issuance		349,007							347,416
Percent of shares reserved and available for issuance automatically increase annually on January 1			1.00%
Number of shares reserved and available for issuance automatically increase annually on January 1 (in shares)			410,803
Maximum \| 2019 Stock option and incentive plan
Share-based awards
Term of stock option			10 years

Stock-based awards - Stock option valuation (Details)	3 Months Ended		6 Months Ended
Stock-based awards - Stock option valuation (Details)	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Assumptions to determine grant-date fair value of stock options granted
Expected term (in years)	5 years 9 months	5 years 7 months 28 days	5 years 9 months 7 days	5 years 10 months 9 days
Expected volatility	74.24%	70.43%	73.10%	70.43%
Weighted average risk-free interest rate	2.91%	1.05%	1.82%	0.80%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Stock based awards - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Number of Options
Balance Outstanding, Beginning of the period (in shares)			5,221,094
Options granted ( in shares)			703,527
Options exercised ( in shares)			(122,208)
Options cancelled (in shares)			(31,055)
Balance Outstanding, End of the period (in shares)	5,771,358		5,771,358		5,221,094
Vested and expected to vest ( in shares)	5,189,977		5,189,977
Exercisable ( in shares)	2,719,542		2,719,542
Weighted-Average Exercise Price per Share
Weighted-average exercise price, Beginning of the period (in dollars per share)			$ 15.49
Weighted-average exercise price, Granted (in dollars per share)			18.10
Weighted-average exercise price, Exercised (in dollars per share)			1.21
Weighted-Average Exercise price, cancelled (in dollars per share)			22.16
Weighted-average exercise price, End of the period (in dollars per share)	$ 16.07		16.07		$ 15.49
Weighted-average exercise price, Vested and expected to vest at end of the period (in dollars per share)	15.49		15.49
Weighted-average exercise price, Exercisable ( in dollars per share )	$ 11.91		$ 11.91
Weighted-Average remaining contractual term (years) and Aggregate Intrinsic Value
Weighted-average remaining contractual term outstanding (in years)			7 years 10 months 13 days		8 years 2 months 12 days
Weighted-average remaining contractual term vested and expected to vest (in years)			7 years 9 months
Weighted-average remaining contractual term , Options Exercisable(in years)			7 years 29 days
Aggregate Intrinsic Value Balance outstanding	$ 10,986		$ 10,986		$ 36,168
Aggregate Intrinsic Value Vested and Expected to vest	10,986		10,986
Aggregate Intrinsic Value Exercisable	$ 9,145		$ 9,145
Weighted average grant-date fair value per share of stock options granted	$ 8.67	$ 16.49	$ 18.10	$ 16.27

Stock based awards - Stock-based compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Stock-based compensation
Total stock-based compensation expense	$ 4,161	$ 2,436	$ 7,472	$ 4,800
Research and development expense
Stock-based compensation
Total stock-based compensation expense	1,474	734	2,585	1,453
General and administrative expense
Stock-based compensation
Total stock-based compensation expense	$ 2,687	$ 1,702	$ 4,887	$ 3,347

Amgen license agreement (Details) - USD ($)	1 Months Ended		3 Months Ended			6 Months Ended
Amgen license agreement (Details) - USD ($)	Nov. 30, 2018	Jun. 30, 2018	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2019	Jun. 30, 2022	Jun. 30, 2021
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share Issued value under agreement			$ 24,647,000
Research and development expense			21,363,000	$ 23,976,000		$ 41,877,000	$ 34,578,000
Amgen Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Initial fair value of the anti-dilution right liability	$ 7,404,000
Payment for clinical trail					$ 2,500,000
Obligation for payment in connection with dosing of the first patient					7,500,000
Amgen Agreement \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate milestone payments upon the achievement of specified commercial milestones					75,000,000
Payment in connection with dosing of the first patient					$ 30,000,000
Amgen Agreement \| Research and development expense
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense			$ 0	$ 0		$ 0	$ 0
Amgen Agreement \| Amgen
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront payment		$ 5,000,000
Amgen Agreement \| Series A Preferred Stock
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share Issued under agreement	3,205,128
Amgen Agreement \| Series A Preferred Stock \| Amgen
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share Issued under agreement		2,653,333
Share Issued value under agreement		$ 1,353,000
Ownership Interest [Member] \| Amgen Agreement \| Amgen
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Ownership interest of the outstanding shares (as a percent)		10.00%

Income taxes - Textual (Details) - USD ($)		3 Months Ended		6 Months Ended
Income taxes - Textual (Details) - USD ($)	Jun. 29, 2020	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income tax benefit related to operating losses and research and development tax credits		$ 0	$ 0	$ 0	$ 0
Income tax benefits		$ 0		$ 0
Amount of state tax that can be offset by NOLs and credits for a three year period	$ 5,000,000
State taxable income amount that can be reduced by NOLs for a three year period	$ 1,000,000

- Definition

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

+ References + Details

Net loss per share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss	$ (27,403)	$ (26,029)	$ (28,933)	$ (15,090)	$ (53,432)	$ (44,023)	$ (100,777)	$ (79,207)
Denominator:
Weighted average common shares outstanding, basic	35,383,685		34,814,631		35,195,638	34,779,647
Weighted average common shares outstanding, diluted	35,383,685		34,814,631		35,195,638	34,779,647
Net loss per share, basic	$ (0.77)		$ (0.83)		$ (1.52)	$ (1.27)
Net loss per share, diluted	$ (0.77)		$ (0.83)		$ (1.52)	$ (1.27)
Number of weighted average restricted common stock	0		8,963		0	16,367

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- 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 - Anti-Diluted (Details) - shares	3 Months Ended		6 Months Ended
Net loss per share - Anti-Diluted (Details) - shares	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total	5,954,956	3,966,208	5,954,956	3,966,208
Options to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total	5,771,358	3,962,372	5,771,358	3,962,372
Warrants to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total	36,718		36,718
Warrants Reserved for Contingent Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total	146,880		146,880
Unvested Restricted Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total		3,836		3,836

Commitments and contingencies (Details) $ in Thousands	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jul. 10, 2020 ft²	Feb. 29, 2020 USD ($)
Lease agreement term				7 years
Square feet of office \| ft²			6,647
Minimum payments during the term				$ 2,300
Non-cancelable purchase and other commitments with contract research organizations and contract manufacturing organizations	$ 6,957
Total lease liability	1,417
Operating lease liability, noncurrent	$ 1,199	$ 1,311
Accounting Standards Update 2016-13 [Member]
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Operating lease liability, noncurrent, Prepaid Expense and Other Assets, Current
Short-term Liabilities	$ 218

Commitments and contingencies - Maturities Of Operating Leases (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Lessee, Operating Lease, Liability, to be Paid [Abstract]
2022 (remaining)	$ 158
2023	321
2024	331
2025	341
2026	351
2027	208
Total future minimum lease payments	1,710
Less imputed interest	(293)
Present value of operating lease liabilities	$ 1,417

Commitments and contingencies - Components of operating lease expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating lease expense:
Total operating lease cost	$ 112	$ 81	$ 234	$ 162
Other information:
Cash paid for amounts included in the measurement of operating lease liability	$ 77	$ 75	$ 154	$ 150
Weighted average remaining lease term	5 years 1 month 6 days	6 years 1 month 6 days	5 years 1 month 6 days	6 years 1 month 6 days
Weighted average discount rate	7.60%	7.60%	7.60%	7.60%
General and administrative expense
Operating lease expense:
Operating lease cost	$ 81	$ 81	$ 162	$ 162
Short-term lease cost			29
Variable operating lease cost	$ 31		$ 43