Akero Therapeutics (AKRO) 10-K 17 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Mar. 14, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding		46,970,989
Entity Public Float			$ 340,434,662
Entity Central Index Key	0001744659
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34
Auditor Location	Morristown, NJ
Documents Incorporated by Reference [Text Block]	Part III of this Annual Report on Form 10-K incorporates by reference certain information from the registrant’s definitive Proxy Statement for its 2023 annual meeting of shareholders, which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the registrant’s fiscal year end of December 31, 2022. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 249,773	$ 150,483
Short-term marketable securities	101,676	37,775
Prepaid expenses and other current assets	3,724	5,324
Total current assets	355,173	193,582
Property and equipment, net	47	90
Right of use asset	1,242	1,459
Other assets, noncurrent	108	417
Total assets	356,570	195,548
Current liabilities:
Accounts payable	7,968	6,706
Accrued expenses and other current liabilities	11,115	18,422
Total current liabilities	19,083	25,128
Loan payable, noncurrent	9,541
Warrant liability	305
Operating lease liability, noncurrent	1,079	1,311
Total liabilities	30,008	26,439
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, $0.0001 par value, 150,000,000 shares authorized as of December 31, 2022 and December 31, 2021; 46,856,206 and 34,900,727 shares issued and outstanding as of December 31, 2022 and December 31, 2021, respectively	5	4
Additional paid-in capital	748,857	479,436
Accumulated other comprehensive income (loss)	37	(27)
Accumulated deficit	(422,337)	(310,304)
Total stockholders' equity	326,562	169,109
Total liabilities and stockholders' equity	$ 356,570	$ 195,548

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 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	46,865,206	34,900,727
Common stock, shares outstanding	46,865,206	34,900,727

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development	$ 85,284	$ 81,759
General and administrative	29,872	19,127
Total operating expenses	115,156	100,886
Loss from operations	(115,156)	(100,886)
Interest expense	(739)
Other income, net	3,862	109
Net loss	(112,033)	(100,777)
Net unrealized gain (loss) on short-term marketable securities	64	(24)
Comprehensive loss	$ (111,969)	$ (100,801)
Net loss per share, basic	$ (2.87)	$ (2.89)
Net loss per share, diluted	$ (2.87)	$ (2.89)
Weighted-average number of shares used in computing net loss per common share, basic	38,984,772	34,827,385
Weighted-average number of shares used in computing net loss per common share, diluted	38,984,772	34,827,385

Consolidated Statements of Stoc

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	750		750
Exercise of stock options (in shares)		140,128
Vesting of restricted stock	21		21
Issuance of common stock pursuant to ESPP purchases	373		373
Issuance of common stock pursuant to ESPP purchases (in shares)		18,950
Stock-based compensation expense	10,054		10,054
Net unrealized gain (loss) on short-term marketable securities	(24)			(24)
Net loss	(100,777)				(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
Exercise of stock options	$ 5,238		5,238
Exercise of stock options (in shares)	559,145	559,145
Issuance of common stock pursuant to ESPP purchases	$ 280		280
Issuance of common stock pursuant to ESPP purchases (in shares)		33,928
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
Issuance of common stock upon closing of follow-on public offering, net of issuance costs and underwriting fees (shares)		8,846,154
Issuance of common stock upon closing of follow-on public offering, net of issuance costs and underwriting fees	215,787	$ 1	215,786
Stock-based compensation expense	23,243		23,243
Net unrealized gain (loss) on short-term marketable securities	64			64
Net loss	(112,033)				(112,033)
Balance at ending at Dec. 31, 2022	$ 326,562	$ 5	$ 748,857	$ 37	$ (422,337)
Balance at ending (in shares) at Dec. 31, 2022		46,865,206

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Statement of Stockholders' Equity [Abstract]
Net issuance costs and underwriting fees	$ 13,800

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (112,033)	$ (100,777)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	23,243	10,054
Depreciation	43	41
Non-cash lease expense	217	203
Net amortization of premiums and discounts on short-term investments	(12)	1,066
Amortization of debt issuance costs and discount	204
Fair value change in warrant liability	264
Unrealized foreign exchange gain and loss	16	5
Changes in operating assets and liabilities:
Prepaid expenses and other assets	2,112	(2,101)
Accounts payable	968	3,273
Accrued expenses and other current liabilities	(7,333)	8,737
Operating lease liability	(206)	(182)
Net cash used in operating activities	(92,517)	(79,681)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of short-term marketable securities	(101,446)	(43,561)
Proceeds from maturities of short-term marketable securities	37,621	85,841
Net cash (used in) provided by investing activities	(63,825)	42,280
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the exercise of stock options	5,016	750
Proceeds from the issuance of common stock pursuant to employee stock purchase plan purchases	280	373
Proceeds from the issuance of common stock pursuant to private offering	25,000
Proceeds from the issuance of common stock in a follow-on public offering, net of underwriting costs	216,200
Proceeds from loan payable	10,000
Payment of loan payable issuance costs	(395)
Payment of follow-on public offering issuance costs	(126)
Payment of private equity offering costs	(212)
Payment of deferred offering costs	(131)	(521)
Net cash provided by financing activities	255,632	602
Net increase (decrease) in cash, cash equivalents and restricted cash	99,290	(36,799)
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	249,881	150,591
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for interest	441
NON-CASH INVESTING AND FINANCING INFORMATION:
Change in net unrealizable gain (loss) on marketable securities	64	$ (24)
Deferred offering costs reclassified to additional paid-in equity	150
Equity Issuance Costs Included in Accounts Payable and Accrued Expenses and Other Current Liabilities	278
Deferred offering costs included in accounts payable and accrued expenses and other current liabilities	$ 7

Nature of the business and basi

Nature of the business and basis of presentation	12 Months Ended
	Dec. 31, 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 patients with cirrhotic NASH (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 recently reported Week 24 results from the HARMONY study, which showed statistically significant response rates for both the 50mg and 28mg dose groups on both fibrosis regression and NASH resolution among patients with biopsy-confirmed NASH. Based on these data and data from the BALANCED study, the Company believes EFX has the potential, if approved, to be a best-in-class medicine for treating NASH. 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 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 and a follow-on public offering in September 2022. The Company has incurred recurring losses since its inception, including net losses of $ 112,033 and $ 100,777 for the years ended December 31, 2022 and 2021, respectively. In addition, as of December 31, 2022, the Company had an accumulated deficit of $ 422,337 . The Company expects to continue to generate operating losses for the foreseeable future. As of March 17, 2023, the issuance date of these consolidated financial statements, the Company expects that its existing cash, cash equivalents and short-term marketable securities of $ 351,449 as of December 31, 2022, will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of these 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 accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Summary of significant accounting policies	2. Summary of significant accounting policies Use of estimates The preparation of the Company's 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 consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these 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 consolidated balance sheets with related unrealized gains and losses included within accumulated other comprehensive gain (loss) on the 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 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 consolidated statements of operations and comprehensive loss, with a corresponding allowance for credit losses account in the 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 consolidated statements of operations. There were no credit losses recorded during the years ended December 31, 2022 and 2021. Restricted cash As of December 31, 2022 and 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 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. The Company regularly maintains deposits in accredited financial institutions in excess of federally insured limits. The Company invests its excess cash primarily in money market funds, U.S. treasury notes, and high quality, marketable debt instruments of corporations in accordance with the Company’s investment policy. The Company’s investment policy defines allowable investments and establishes guidelines relating to credit quality, diversification, and maturities of its investments to preserve principal and maintain liquidity. The Company has not experienced any losses related to its cash equivalents and marketable securities and management believes the Company is not exposed to significant risks of losses . As of December 31, 2022, the Company held cash deposits at Silicon Valley Bank (“SVB”) in excess of government insured limits. On March 10, 2023, SVB was closed by the California Department of Financial Protection and Innovation, and the Federal Deposit Insurance Corporation (“FDIC”) was appointed as receiver. No losses were incurred by the Company on deposits that were held at SVB. Management believes that the Company is not currently exposed to significant credit risk as the vast majority of the Company’s deposits were either owned directly by the Company and held in custody at a third-party financial institution or, subsequent to March 10, 2023, have been transferred to a third-party financial institution. As of March 17, 2023, the Company has approximately € 12,000 on deposit with SVB, which it expects to transfer to another financial institution in the near term. The Company does not currently have any other significant relationships with SVB. 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. Foreign currency transaction gains and losses related to the purchase of contract manufacturing services are included as a component of research and development expense. 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 makes stock-based awards from its stock compensation plans (see Note 7). 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. Stock-based compensation for restricted stock units is measured based on the market closing price of our common stock on the grant date. Stock-based compensation expense is recognized on a straight-line basis over the requisite service period, generally four years. 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 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 represents the Loan and Security Agreement (“Loan Agreement”) with Hercules Capital, Inc. (“Hercules”), which the Company has accounted for as a debt financing arrangement. Interest expense is accrued using the effective interest rate method over the estimated period the loan will be repaid. Loan issuance costs have been recorded as a debt discount in the consolidated balance sheets and are being amortized and recorded as interest expense throughout the life of the Loan Agreement using the effective interest rate method. The Company considered whether there were any embedded features in the Loan Agreement that require bifurcation and separate accounting as derivative financial instruments pursuant to Accounting Standards Codification ("ASC") Topic 815, Derivatives and Hedging. 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. Income taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company's tax returns. Deferred tax assets and liabilities are determined based on the difference between the consolidated financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Net loss per share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration of common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the Company’s net 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 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 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 consolidated financial statements.

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 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 no t 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 December 31, 2022 and 2021: December 31, 2022 Total Level 1 Level 2 Level 3 Money market funds $ 137,286 $ 137,286 $ — $ — U.S. Treasury securities 58,721 58,721 — — Corporate debt securities 5,476 — 5,476 — U.S. Government agency securities 62,955 — 62,955 — Commercial paper 27,738 — 27,738 — Total assets $ 292,176 $ 196,007 $ 96,169 $ — Warrant liabilities $ 305 $ — $ — $ 305 Total liabilities $ 305 $ — $ — $ 305 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. As of December 31, 2022, the Company also held $ 41,834 in interest-bearing, overnight sweep accounts. This amount approximates its fair value due to the short-term nature of the accounts. 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 years ended December 31, 2022 and 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 December 31, 2022, the carrying value of the Loan Payable, approximates its fair value. 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.

Short-term marketable securitie

Short-term marketable securities	12 Months Ended
	Dec. 31, 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 December 31, 2022 and 2021 : December 31, 2022 Amortized cost Gross unrealized gains Gross unrealized losses Credit losses Fair value Money market funds $ 137,286 $ — $ — $ — $ 137,286 U.S. Treasury securities 58,698 23 — — 58,721 Corporate debt securities 5,478 — ( 2 ) — 5,476 U.S. Government agency securities 62,939 15 — — 62,954 Commercial paper 27,739 — — — 27,739 $ 292,140 $ 38 $ ( 2 ) $ — $ 292,176 Cash equivalents $ 190,500 Short-term marketable securities 101,676 $ 292,176 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 December 31, 2022 and 2021, all of the Company’s short-term marketable securities had contractual maturities of less than one year.

Accrued expenses and other curr

Accrued expenses and other current liabilities	12 Months Ended
	Dec. 31, 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 December 31, 2022 and 2021 : December 31, 2022 December 31, 2021 Accrued external research and development expenses $ 9,789 $ 17,539 Accrued employee compensation and benefits 804 554 Accrued legal and professional fees 197 124 Short-term lease liability and other 325 205 $ 11,115 $ 18,422

Loan Payable and Warrant Liabil

Loan Payable and Warrant Liability	12 Months Ended
	Dec. 31, 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, $ 15,000 was borrowed on March 10, 2023 and an additional $ 10,000 is available to the Company at its sole discretion. An additional $ 20,000 will become available to the Company upon the achievement of certain clinical and financial milestones. An additional $ 45,000 may 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 certain 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 number 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 December 31, 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 reassesses the fair value of the warrant liability at the end of each prospective reporting period. The warrant liabilities were valued at $ 305 as of December 31, 2022. The change in fair value of the warrant liability of $ 264 from June 15, 2022 to December 31, 2022 arising from remeasurement was recorded in the statements of operations. Future principal debt payments on the currently outstanding loan payable as of December 31, 2022 are as follows (in thousands): 2022 $ — 2023 — 2024 1,710 2025 3,725 2026 4,169 2027 396 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 ( 1,629 ) Loan Payable - noncurrent $ 9,541 The Company estimated the fair value of the warrant liability as of December 31, 2022 using probability assumptions of achieving the future milestones and using the Black-Scholes model based on the following key assumptions: As of December 31, 2022 Expected term (in years) 6.50 Expected volatility 77.29 % Risk-free interest rate 4.18 % Expected dividend yield 0.00 %

Stockholder's equity (deficit)

Stockholder's equity (deficit)	12 Months Ended
	Dec. 31, 2022
Stockholders' Equity Note [Abstract]
Stockholder's equity (deficit)	7. Stockholder’s equity (deficit) Common stock As of December 31, 2022 and 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 December 31, 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. 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 year ended December 31, 2022, the Company did no t 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. On September 19, 2022, the Company completed a follow-on public offering at which time the Company issued 8,846,154 shares of common stock, including the exercise in full by the underwriters of their option to purchase up to 1,153,846 additional shares of common stock, at a public offering price of $ 26.00 per share. The Company received $ 216,200 net of underwriting discounts and commissions of $ 13,800 , but before deducting offering costs incurred by the Company. As of December 31, 2022 and 2021, there were 46,865,206 and 34,900,727 shares of common stock issued and outstanding, respectively. The following shares of common stock were reserved for issuance as follows: December 31, 2022 December 31, 2021 Options outstanding under the 2018 Stock Option and Grant Plan 1,633,173 2,011,891 Options outstanding under the 2019 Stock Option and Incentive Plan 4,146,831 3,209,203 Restricted stock units outstanding under the 2019 Stock Option and Incentive Plan 129,131 — Warrants to purchase common stock associated with Loan Agreement 36,718 — Options available for future grant 2,038,142 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 1,187,508 872,429 14,318,383 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 December 31, 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.

Stock-based awards

Stock-based awards	12 Months Ended
	Dec. 31, 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: Year Ended December 31, 2022 2021 Expected term (in years) 5.30 5.77 Expected volatility 74.59 % 72.17 % Weighted average risk-free interest rate 2.71 % 1.19 % Expected dividend yield 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 1,355,673 $ 28.76 Options exercised ( 559,145 ) $ 9.37 Options cancelled ( 237,618 ) $ 23.09 Balance outstanding, December 31, 2022 5,780,004 $ 18.88 7.80 $ 207,611 Vested and expected to vest, December 31, 2022 5,780,004 $ 18.88 7.80 $ 207,611 Exercisable, December 31, 2022 3,670,458 $ 14.37 7.19 $ 148,416 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 years ended December 31, 2022 and 2021 was $ 28.76 and $ 13.98 , 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 . In September 2022, two of the three performance-based awards milestones were achieved and were deemed vested . In December 2022, the third portion of the performance-based awards milestones was achieved and was deemed vested. During the year ended December 31, 2022, the Company recognized $ 10,487 of related stock compensation expense, based upon management's estimates of the probabilities of the milestones being achieved and the fully vesting of the performance awards. Restricted Stock Units The 2019 Plan allows for the grants of Restricted Stock Units (RSUs). Generally, the RSUs are subject to a four-year vesting period of which the Company has designated to vest on a quarterly basis over the remaining vesting term. In December 2022, the Company granted 129,131 RSUs to executive management with a total grant date fair value of $ 5,546 . As of December 31, 2022, these awards are not yet vested. The following table summarizes the Company’s RSUs activity since December 31, 2021: Weighted- Weighted- Average Average Aggregate Grant Date remaining Intrinsic Underlying Fair Value per contractual Value shares Share term (years) (000's) Balance outstanding, December 31, 2021 — $ — — — Granted 129,131 $ 42.95 Vested — $ — Cancelled or forfeited — $ — Balance outstanding, December 31, 2022 129,131 $ 42.95 2.07 $ 7,076 Stock-based compensation The following table summarizes the Company’s stock-based compensation expense during the years ended December 31, 2022 and 2021: Year Ended December 31, 2022 2021 Classified within research and development expense $ 8,096 $ 3,054 Classified within general and administrative expense 15,147 7,000 Total stock-based compensation expense $ 23,243 $ 10,054 As of December 31, 2022, total unrecognized compensation cost related to unvested stock options and RSUs was $ 36,164 and 5,461 , respectively. These unvested stock options and RSUs are expected to be recognized over a weighted average period of 2.61 years and 3.94 years respectively.

Amgen license agreement

Amgen license agreement	12 Months Ended
	Dec. 31, 2022
Amgen license agreement
Amgen license agreement	9. 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 years ended December 31, 2022 and 2021, the Company did no t record any research and development expense in connection with the Amgen Agreement.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income taxes	10. Income taxes During the years ended December 31, 2022 and 2021, the Company recorded no 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. A summary of the Company’s current and deferred tax provision is as follows: Year Ended December 31, 2022 2021 Current income tax provision: Federal $ — $ — State — — Total current income tax provision — — Deferred income tax benefit: Federal 27,269 23,352 State 14,568 7,274 Total deferred income tax benefit 41,837 30,626 Change in deferred tax asset valuation allowance ( 41,837 ) ( 30,626 ) Total provision for income taxes $ — $ — A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year Ended December 31, 2022 2021 Federal statutory income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 13.0 7.2 Research and development tax credits 2.4 2.0 Other permanent differences 0.8 ( 0.1 ) Change in deferred tax asset valuation allowance ( 37.2 ) ( 30.1 ) Effect of Section 382 limitation - - Effective income tax rate - % - % Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following: December 31, 2022 2021 Deferred tax assets: Net operating loss carry forwards $ 68,450 $ 56,128 Research and development tax credit carry forwards 7,704 4,522 License fees 3,355 3,523 Stock based compensation 8,974 3,716 Capitalized research and experimentation costs 20,803 — Accruals, reserves and other 191 151 109,477 68,040 Valuation allowance ( 108,690 ) ( 66,853 ) Net deferred tax assets 787 1,187 Deferred tax liabilities: Prepaid expenses ( 787 ) ( 1,187 ) Net deferred tax liabilities ( 787 ) ( 1,187 ) As of December 31, 2022, the Company had U.S. federal and state net operating loss carryforwards of $ 248,406 and $ 235,472 , respectively, which may be available to offset future taxable income and begin to expire in 2037. The federal net operating loss carryforwards include $ 245,963 , which may be carried forward indefinitely. As of December 31, 2022, the Company also had U.S. federal and state research and development tax credit carryforwards of $ 8,827 and $ 1,249 , respectively, which may be available to offset future tax liabilities and begin to expire in 2033. During the year ended December 31, 2022, gross deferred tax assets, before valuation allowance, increased by $ 41,837 , due to the operating loss incurred by the Company during that period. Utilization of the U.S. federal and state net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Sections 382 and 383 of the Internal Revenue Code of 1986, and corresponding provisions of state law, due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income or tax liabilities. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three‑year period. The annual limitation is determined by multiplying the value of the Company's stock at the time of such ownership change by the applicable long-term tax-exempt rate. Such limitations may result in expiration of a portion of the NOL carryforwards before utilization. As of December 31, 2022, the Company determined that ownership changes occurred on March 24, 2017, June 7, 2018 and July 8, 2020. As a result of the ownership changes, approximately $ 2,118 and $ 3,632 of the NOLs will expire unutilized for federal and state purposes, respectively. The ability of the Company to use its remaining NOL carryforwards may be further limited if the Company experiences a Code Section 382 ownership change as a result of future changes in its stock ownership. The Company’s research and development credits are subject to Code Section 383 and are limited due to the ownership changes that the Company has experienced. As of December 31, 2022, the Company has derecognized approximately $ 87 and $ 43 of gross federal and state research and development credits, respectively. The Company has not derecognized any of the California research and development credit-related deferred tax assets because the credits do not expire. The Company has evaluated the positive and negative evidence bearing upon its ability to realize its deferred tax assets at each reporting period. In doing so, the Company has considered its history of cumulative net losses incurred and its lack of commercialization of any products or generation of any revenue from product sales and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been recorded against the net deferred tax assets as of December 31, 2022 and 2021. Management reevaluates the positive and negative evidence at each reporting period. Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2022 and 2021 related primarily to the increase in net operating loss carryforwards and research and development tax credit carryforwards and were as follows: 2022 2021 Valuation allowance as of January 1, $ ( 66,853 ) $ ( 36,227 ) Increases recorded to income tax provision — — Decreases recorded as a benefit to income tax provision ( 41,837 ) ( 30,626 ) Valuation allowance as of December 31, $ ( 108,690 ) $ ( 66,853 ) As of December 31, 2022, the Company had gross unrecognized tax benefits of $ 2,110 , none of which if recognized, would reduce the effective tax rate in a future period, due to the Company's full valuation allowance on U.S. net deferred tax assets. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. As of December 31, 2022, the Company had no t accrued interest or penalties related to uncertain tax positions and no amounts had been recognized in the Company’s consolidated statements of operations and comprehensive loss. For the year ended December 31, 2022, the Company will file income tax returns in the U.S., California, Connecticut, Florida, Illinois, Massachusetts, Maryland, New York, New Jersey, North Carolina, Pennsylvania and Virginia, as prescribed by the tax laws of the jurisdictions in which it operates. The Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. The Company is open to future tax examination under statute from 2018 to the present. A reconciliation of the beginning and ending unrecognized tax benefits for the years ended December 31, 2022 and 2021 is as follows Balance at December 31, 2020 $ 644 Increases related to prior year tax positions 66 Increases related to current year tax positions 603 Balance at December 31, 2021 1,313 Increases related to prior year tax positions 51 Increases related to current year tax positions 746 Balance at December 31, 2022 $ 2,110 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 taxes for the year ended December 31, 2022. On June 29, 2020, California Governor signed Assembly Bill 85 (“A.B. 85”), which now becomes California law. A.B. 85, 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 $ 5,000 of tax per year. Generally, A.B. 85 suspends the use of net operating losses for taxable years 2020, 2021, and 2022 for taxpayers with taxable income of $ 1,000 or more.” On February 9, 2022, the California Governor signed into law CA SB 113 which shortens the previously enacted suspension on the use of NOLs and R&D credits. Accordingly, SB 113 restored NOL utilization and removes the R&D credit limitation for 2022, and as such no impact to the Company for the period ended December 31, 2022. The Tax Cuts and Jobs Act (“TCJA”) included a change in the treatment of research and development expenditures for tax purposes under Section 174. Effective for tax years beginning after December 31, 2021, specified R&D expenditures must undergo a 5-year amortization period for domestic spend and a 15-year amortization period for foreign spend, beginning with the midpoint of the taxable year in which such expenditures are paid or incurred. Prior to the effective date (2021 tax year and prior), taxpayers were able to immediately expense R&D costs under Section 174(a) or had the option to capitalize and amortize R&D expenditures over a 5-year recovery period under Section 174(b). Accordingly, the Company is estimating 2022 capitalization of U.S R&D expenditures net of 2022 amortization of approximately $ 57,658 (an addback to estimated 2022 US taxable income). Additionally, the requirement to capitalize and amortize foreign R&D expenses over 15 years resulted in 2022 capitalization of R&D expenditures (net of amortization) of $ 14,728 . On August 16, 2022, the IRA was signed into law. The IRA includes implementation of a new alternative minimum tax, an excise tax on stock buybacks, and significant tax incentives for energy and climate initiatives, among other provisions. The Company is evaluating the provisions included under the IRA and does not expect the provisions to have a material impact to the Company’s consolidated financial statements. All tax returns will remain open for examination by the federal and state taxing authorities for three and four years, respectively, from the date of utilization of any net operating loss carryforwards or research and development credits.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 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: Year Ended December 31, 2022 2021 Numerator: Net loss $ 112,033 $ 100,777 Denominator: Weighted average common shares outstanding, basic and diluted 38,984,772 34,827,385 Net loss per share, basic and diluted $ 2.87 $ 2.89 The Company excluded nil shares and 8,127 shares of restricted common stock, presented on a weighted average basis, from the calculations of basic net loss per share for the years ended December 31, 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: Year Ended December 31, 2022 2021 Options to purchase common stock 5,780,004 5,221,094 Unvested restricted stock units 129,131 — Warrants to purchase common stock 36,718 — Warrants available for future grant 146,880 — 6,092,733 5,221,094

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 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 years ended December 31, 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 December 31, 2022, maturities of the Company’s operating lease liability was as follows: 2023 321 2024 331 2025 341 2026 351 2027 208 Total future minimum lease payments 1,552 Less imputed interest ( 242 ) Present value of operating lease liabilities $ 1,310 As of December 31, 2022, the total lease liability was $ 1,310 , of which $ 1,079 was noncurrent and $ 231 was short-term and classified within “ Accrued expenses and other current liabilities ” on the consolidated balance sheet. For the years ended December 31, 2022 and 2021, the components of operating lease cost were as follows: Year Ended December 31, 2022 2021 Lease cost: Statement of Operations Classification: Operating lease cost General and administrative expense $ 324 $ 324 Short-term lease cost General and administrative expense 58 — Variable operating lease cost General and administrative expense 58 17 Total operating lease cost $ 440 $ 341 Other information: Cash paid for amounts included in the measurement of operating lease liability $ 312 $ 303 Weighted average remaining lease term 4.6 5.6 Weighted average discount rate 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 December 31, 2022, the Company had non-cancelable purchase and other commitments under these agreements totaling $ 7,239 . 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 consolidated financial statements as of December 31, 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

Subsequent event	12 Months Ended
	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent event	13. Subsequent event The Company evaluated subsequent events through March 17, 2023, the date on which these consolidated financial statements were issued. On Friday, March 10, 2023, the Company drew an incremental $ 15,000 from its term loan facility with Hercules to ensure no interruption to near-term business operations in the face of potential volatility in the financial sector. In connection with the draw of additional funds, the Company’s existing warrants to purchase shares of common stock held by Hercules became exercisable for 45,898 shares of common stock.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Use of estimates	Use of estimates The preparation of the Company's 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 consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these 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 consolidated balance sheets with related unrealized gains and losses included within accumulated other comprehensive gain (loss) on the 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 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 consolidated statements of operations and comprehensive loss, with a corresponding allowance for credit losses account in the 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 consolidated statements of operations. There were no credit losses recorded during the years ended December 31, 2022 and 2021.
Restricted cash	Restricted cash As of December 31, 2022 and 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 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. The Company regularly maintains deposits in accredited financial institutions in excess of federally insured limits. The Company invests its excess cash primarily in money market funds, U.S. treasury notes, and high quality, marketable debt instruments of corporations in accordance with the Company’s investment policy. The Company’s investment policy defines allowable investments and establishes guidelines relating to credit quality, diversification, and maturities of its investments to preserve principal and maintain liquidity. The Company has not experienced any losses related to its cash equivalents and marketable securities and management believes the Company is not exposed to significant risks of losses . As of December 31, 2022, the Company held cash deposits at Silicon Valley Bank (“SVB”) in excess of government insured limits. On March 10, 2023, SVB was closed by the California Department of Financial Protection and Innovation, and the Federal Deposit Insurance Corporation (“FDIC”) was appointed as receiver. No losses were incurred by the Company on deposits that were held at SVB. Management believes that the Company is not currently exposed to significant credit risk as the vast majority of the Company’s deposits were either owned directly by the Company and held in custody at a third-party financial institution or, subsequent to March 10, 2023, have been transferred to a third-party financial institution. As of March 17, 2023, the Company has approximately € 12,000 on deposit with SVB, which it expects to transfer to another financial institution in the near term. The Company does not currently have any other significant relationships with SVB.
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. Foreign currency transaction gains and losses related to the purchase of contract manufacturing services are included as a component of research and development expense. 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 makes stock-based awards from its stock compensation plans (see Note 7). 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. Stock-based compensation for restricted stock units is measured based on the market closing price of our common stock on the grant date. Stock-based compensation expense is recognized on a straight-line basis over the requisite service period, generally four years. 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 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 Loan Payable represents the Loan and Security Agreement (“Loan Agreement”) with Hercules Capital, Inc. (“Hercules”), which the Company has accounted for as a debt financing arrangement. Interest expense is accrued using the effective interest rate method over the estimated period the loan will be repaid. Loan issuance costs have been recorded as a debt discount in the consolidated balance sheets and are being amortized and recorded as interest expense throughout the life of the Loan Agreement using the effective interest rate method. The Company considered whether there were any embedded features in the Loan Agreement that require bifurcation and separate accounting as derivative financial instruments pursuant to Accounting Standards Codification ("ASC") Topic 815, Derivatives and Hedging.
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.
Income taxes	Income taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company's tax returns. Deferred tax assets and liabilities are determined based on the difference between the consolidated financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Net loss per share	Net loss per share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration of common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the Company’s net loss.
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 adopted accounting pronouncements	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 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 consolidated financial statements.

Fair value of financial assets

Fair value of financial assets and liabilities (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2022 and 2021: December 31, 2022 Total Level 1 Level 2 Level 3 Money market funds $ 137,286 $ 137,286 $ — $ — U.S. Treasury securities 58,721 58,721 — — Corporate debt securities 5,476 — 5,476 — U.S. Government agency securities 62,955 — 62,955 — Commercial paper 27,738 — 27,738 — Total assets $ 292,176 $ 196,007 $ 96,169 $ — Warrant liabilities $ 305 $ — $ — $ 305 Total liabilities $ 305 $ — $ — $ 305 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 securit_2

Short-term marketable securities (Tables)	12 Months Ended
	Dec. 31, 2022
Short-term marketable securities
Summary of short-term marketable securities	The following is a summary of short-term marketable securities as of December 31, 2022 and 2021 : December 31, 2022 Amortized cost Gross unrealized gains Gross unrealized losses Credit losses Fair value Money market funds $ 137,286 $ — $ — $ — $ 137,286 U.S. Treasury securities 58,698 23 — — 58,721 Corporate debt securities 5,478 — ( 2 ) — 5,476 U.S. Government agency securities 62,939 15 — — 62,954 Commercial paper 27,739 — — — 27,739 $ 292,140 $ 38 $ ( 2 ) $ — $ 292,176 Cash equivalents $ 190,500 Short-term marketable securities 101,676 $ 292,176 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 cu_2

Accrued expenses and other current liabilities (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2022 and 2021 : December 31, 2022 December 31, 2021 Accrued external research and development expenses $ 9,789 $ 17,539 Accrued employee compensation and benefits 804 554 Accrued legal and professional fees 197 124 Short-term lease liability and other 325 205 $ 11,115 $ 18,422

Loan Payable and Warrant Liab_2

Loan Payable and Warrant Liability (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2022 are as follows (in thousands): 2022 $ — 2023 — 2024 1,710 2025 3,725 2026 4,169 2027 396 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 ( 1,629 ) Loan Payable - noncurrent $ 9,541
Schedule of Assumptions Used to Determine Estimated Fair Value of Warrant Liability	The Company estimated the fair value of the warrant liability as of December 31, 2022 using probability assumptions of achieving the future milestones and using the Black-Scholes model based on the following key assumptions: As of December 31, 2022 Expected term (in years) 6.50 Expected volatility 77.29 % Risk-free interest rate 4.18 % Expected dividend yield 0.00 %

Stockholder's equity (deficit)

Stockholder's equity (deficit) (Tables)	12 Months Ended
	Dec. 31, 2022
Stockholders' Equity Note [Abstract]
Schedule of common stock reserved for issuance	The following shares of common stock were reserved for issuance as follows: December 31, 2022 December 31, 2021 Options outstanding under the 2018 Stock Option and Grant Plan 1,633,173 2,011,891 Options outstanding under the 2019 Stock Option and Incentive Plan 4,146,831 3,209,203 Restricted stock units outstanding under the 2019 Stock Option and Incentive Plan 129,131 — Warrants to purchase common stock associated with Loan Agreement 36,718 — Options available for future grant 2,038,142 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 1,187,508 872,429 14,318,383 12,982,822

Stock-based awards (Tables)

Stock-based awards (Tables)	12 Months Ended
	Dec. 31, 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: Year Ended December 31, 2022 2021 Expected term (in years) 5.30 5.77 Expected volatility 74.59 % 72.17 % Weighted average risk-free interest rate 2.71 % 1.19 % Expected dividend yield 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 1,355,673 $ 28.76 Options exercised ( 559,145 ) $ 9.37 Options cancelled ( 237,618 ) $ 23.09 Balance outstanding, December 31, 2022 5,780,004 $ 18.88 7.80 $ 207,611 Vested and expected to vest, December 31, 2022 5,780,004 $ 18.88 7.80 $ 207,611 Exercisable, December 31, 2022 3,670,458 $ 14.37 7.19 $ 148,416
Summary of stock-based compensation expense	The following table summarizes the Company’s stock-based compensation expense during the years ended December 31, 2022 and 2021: Year Ended December 31, 2022 2021 Classified within research and development expense $ 8,096 $ 3,054 Classified within general and administrative expense 15,147 7,000 Total stock-based compensation expense $ 23,243 $ 10,054
Summary of restricted stock activity	The following table summarizes the Company’s RSUs activity since December 31, 2021: Weighted- Weighted- Average Average Aggregate Grant Date remaining Intrinsic Underlying Fair Value per contractual Value shares Share term (years) (000's) Balance outstanding, December 31, 2021 — $ — — — Granted 129,131 $ 42.95 Vested — $ — Cancelled or forfeited — $ — Balance outstanding, December 31, 2022 129,131 $ 42.95 2.07 $ 7,076

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Schedule of current and deferred tax provision	A summary of the Company’s current and deferred tax provision is as follows: Year Ended December 31, 2022 2021 Current income tax provision: Federal $ — $ — State — — Total current income tax provision — — Deferred income tax benefit: Federal 27,269 23,352 State 14,568 7,274 Total deferred income tax benefit 41,837 30,626 Change in deferred tax asset valuation allowance ( 41,837 ) ( 30,626 ) Total provision for income taxes $ — $ —
Schedule of reconciliation of the U.S. federal statutory income tax	A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year Ended December 31, 2022 2021 Federal statutory income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 13.0 7.2 Research and development tax credits 2.4 2.0 Other permanent differences 0.8 ( 0.1 ) Change in deferred tax asset valuation allowance ( 37.2 ) ( 30.1 ) Effect of Section 382 limitation - - Effective income tax rate - % - %
Schedule of Net deferred tax assets	Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following: December 31, 2022 2021 Deferred tax assets: Net operating loss carry forwards $ 68,450 $ 56,128 Research and development tax credit carry forwards 7,704 4,522 License fees 3,355 3,523 Stock based compensation 8,974 3,716 Capitalized research and experimentation costs 20,803 — Accruals, reserves and other 191 151 109,477 68,040 Valuation allowance ( 108,690 ) ( 66,853 ) Net deferred tax assets 787 1,187 Deferred tax liabilities: Prepaid expenses ( 787 ) ( 1,187 ) Net deferred tax liabilities ( 787 ) ( 1,187 )

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 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: Year Ended December 31, 2022 2021 Numerator: Net loss $ 112,033 $ 100,777 Denominator: Weighted average common shares outstanding, basic and diluted 38,984,772 34,827,385 Net loss per share, basic and diluted $ 2.87 $ 2.89
Schedule of computation of diluted net loss per share attributable to common stockholders	Year Ended December 31, 2022 2021 Options to purchase common stock 5,780,004 5,221,094 Unvested restricted stock units 129,131 — Warrants to purchase common stock 36,718 — Warrants available for future grant 146,880 — 6,092,733 5,221,094

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Schedule of maturity of the Company's operating lease liabilities	As of December 31, 2022, maturities of the Company’s operating lease liability was as follows: 2023 321 2024 331 2025 341 2026 351 2027 208 Total future minimum lease payments 1,552 Less imputed interest ( 242 ) Present value of operating lease liabilities $ 1,310
Schedule of components of operating lease expense	For the years ended December 31, 2022 and 2021, the components of operating lease cost were as follows: Year Ended December 31, 2022 2021 Lease cost: Statement of Operations Classification: Operating lease cost General and administrative expense $ 324 $ 324 Short-term lease cost General and administrative expense 58 — Variable operating lease cost General and administrative expense 58 17 Total operating lease cost $ 440 $ 341 Other information: Cash paid for amounts included in the measurement of operating lease liability $ 312 $ 303 Weighted average remaining lease term 4.6 5.6 Weighted average discount rate 7.6 % 7.6 %

Nature of the business and ba_2

Nature of the business and basis of presentation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ 112,033	$ 100,777
Accumulated deficit	422,337	$ 310,304
Cash, cash equivalents and short-term marketable securities	$ 351,449

Summary of significant accoun_3

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

Summary of significant accoun_4

Summary of significant accounting policies - Concentrations of credit risk (Details) € in Millions	Mar. 17, 2023 EUR (€)
Silicon Valley Bank | Subsequent Event
Concentration Risk [Line Items]
Cash deposit expects to transfer to another financial institution	€ 12,000

Fair value of financial asset_2

Fair value of financial assets and liabilities - Textual (Details) - USD ($)	12 Months Ended
	Dec. 31, 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
Interest-bearing, Overnight Sweep Accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount held in interest-bearing, overnight sweep accounts	$ 41,834,000

Fair value of financial asset_3

Fair value of financial assets and liabilities - Recurring (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 292,176	$ 154,036
Liabilities	305
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	137,286	116,261
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	58,721
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	5,476	37,775
U.S. Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	62,955
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	27,738
Warrant liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	305
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	196,007	116,261
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	137,286	116,261
Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	58,721
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	96,169	37,775
Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	5,476	$ 37,775
Level 2 | U.S. Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	62,955
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	27,738
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	305
Level 3 | Warrant liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	$ 305

Short-term marketable securit_3

Short-term marketable securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	$ 292,140	$ 154,063
Gross unrealized gains	38
Gross unrealized losses	(2)	(27)
Fair value	292,176	154,036
Cash equivalents	190,500	116,261
Short-term marketable securities	101,676	37,775
Total	292,176	154,036
Money market funds
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	137,286	116,261
Fair value	137,286	116,261
U.S. Treasury securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	58,698
Gross unrealized gains	23
Fair value	58,721
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	5,478	37,802
Gross unrealized losses	(2)	(27)
Fair value	5,476	$ 37,775
U.S. Government agency securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	62,939
Gross unrealized gains	15
Fair value	62,954
Commercial paper
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	27,739
Fair value	$ 27,739

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued expenses and other current liabilities
Accrued external research and development expenses	$ 9,789	$ 17,539
Accrued employee compensation and benefits	804	554
Accrued legal and professional fees	197	124
Short-term lease liability and other	325	205
Total accrued expenses and other current liabilities	$ 11,115	$ 18,422

Loan Payable and Warrant Liab_3

Loan Payable and Warrant Liability - Textual (Details)			7 Months Ended	12 Months Ended
	Mar. 10, 2023 USD ($) shares	Jun. 15, 2022 USD ($) Tranche	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 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				$ 204,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.0001	$ 0.0001	$ 0.0001
Fair value change in warrant liability				$ 264,000
Hercules Capital, Inc | Subsequent Event
Debt Instrument [Line Items]
Issued warrants to purchase shares of common stock | shares	45,898
Term Loan | Hercules Capital, Inc | Subsequent Event
Debt Instrument [Line Items]
Proceeds from term loan	$ 15,000,000
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	36,718
Recognized initial warrants at relative fair value			$ 227,000	$ 227,000
Additional remaining warrants were recognized at relative fair value at closing of agreement			41,000	41,000
Fair value associated with equity and liability classified warrants				268,000
Warrant liabilities			305,000	$ 305,000
Fair value change in warrant liability			264,000
Loan Agreement | First Twelve Months After Closing
Debt Instrument [Line Items]
Percentage of prepayment charge of outstanding principal balance		3%
Loan Agreement | Second Twelve Months After Closing
Debt Instrument [Line Items]
Percentage of prepayment charge of outstanding principal balance		2%
Loan Agreement | Thereafter
Debt Instrument [Line Items]
Percentage of prepayment charge of outstanding principal balance		1%
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, $15,000 was borrowed on March 10, 2023 and an additional $10,000 is available to the Company at its sole discretion. An additional $20,000 will become available to the Company upon the achievement of certain clinical and financial milestones. An additional $45,000 may 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	$ 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 First Tranche | Hercules Capital, Inc | Subsequent Event
Debt Instrument [Line Items]
Proceeds from term loan	$ 15,000,000
Loan Agreement | Term Loan Second Tranche | Hercules Capital, Inc
Debt Instrument [Line Items]
Maximum borrowing capacity		20,000,000
Loan Agreement | Term Loan Third 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	$ 0.0001
Maximum percentage of warrants purchased				1.50%

Loan Payable and Warrant Liab_4

Loan Payable and Warrant Liability - Schedule of Future principal Debt Payments on Loan Payable (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Long-Term Debt, Fiscal Year Maturity [Abstract]
2024	$ 1,710
2025	3,725
2026	4,169
2027	396
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	(1,629)
Loan Payable - noncurrent	$ 9,541

Loan Payable and Warrant Liab_5

Loan Payable and Warrant Liability - Schedule of Assumptions Used to Determine Estimated Fair Value of Warrant Liability (Details)	Dec. 31, 2022
Measurement Input, Expected Term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (in years)	6 years 6 months
Measurement Input, Price Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of the Warrants, Measurement input	0.7729
Measurement Input, Risk-Free Interest Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of the Warrants, Measurement input	0.0418
Measurement Input, Expected Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of the Warrants, Measurement input	0

Stockholder's equity (deficit_2

Stockholder's equity (deficit) - Common stock (Details)							12 Months Ended
	Sep. 19, 2022 USD ($) $ / shares shares	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	Dec. 31, 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
Common stock, par value (in dollars per share) | $ / shares							$ 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							46,865,206	34,900,727
Common stock, shares outstanding							46,865,206	34,900,727
Common stock were reserved for issuance
Options available for future grant							14,318,383	12,982,822
Options available for future grant
Common stock were reserved for issuance
Options available for future grant							2,038,142	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
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
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
Warrants Available for Future Grant
Common stock were reserved for issuance
Options available for future grant							146,880
2018 Stock option and grant plan
Common stock were reserved for issuance
Options available for future grant							1,633,173	2,011,891	107,635
2019 Stock Option and Incentive plan
Common stock were reserved for issuance
Options available for future grant							4,146,831	3,209,203
2019 Stock Option and Incentive plan | Restricted Stock Units
Common stock were reserved for issuance
Options available for future grant							129,131
2019 Employee Stock Purchase Plan
Common stock were reserved for issuance
Options available for future grant							1,187,508	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
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	8,846,154				6,012,390
Public offering price | $ / shares	$ 26				$ 36
Proceeds received, net of underwriting discounts and commissions | $	$ 216,200,000				$ 203,460,000
Offering costs | $	$ 13,800,000
Over allotment | Maximum
Class of Stock [Line Items]
Share Issued under agreement	1,153,846				784,224
Common stock, shares issued						862,500

Stockholder's equity (deficit_3

Stockholder's equity (deficit) - Undesignated preferred stock and Restricted common stock (Details) - Undesignated Preferred Stock	Dec. 31, 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_4

Stockholder's equity (deficit) - Warrants Associated with Loan Agreement (Details) - Hercules Capital Inc and Hercules Private Global Venture Growth Fund I L.P.	12 Months Ended
	Dec. 31, 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 (D

Stock-based awards - Textual (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Jun. 18, 2019	Jan. 31, 2022	Jun. 30, 2019	Dec. 31, 2022	Dec. 31, 2021	Jan. 31, 2021
Share-based awards
Number of shares remained available for grant				14,318,383	12,982,822
Weighted average grant-date fair value per share of stock options granted				$ 28.76	$ 13.98
Stock options granted ( in shares)				1,355,673
Exercise price				$ 28.76
Stock compensation expense				$ 23,243	$ 10,054
Total unrecognized compensation cost related to unvested stock-based awards				$ 36,164
Weighted average period of recognition for unrecognized compensation cost				2 years 7 months 9 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				$ 10,487
Options vesting description				One-third of the options vest upon achievement of each of the milestones.
Description of milestones achieved and deemed vested				In September 2022, two of the three performance-based awards milestones were achieved and were deemed vested
Restricted Stock Units
Share-based awards
Total unrecognized compensation cost related to RSU				$ 5,461
Weighted average period of recognition for unrecognized compensation cost				3 years 11 months 8 days
RSU granted (shares)				129,131
Total grant date fair value of RSU				$ 5,546
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			1,633,173	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%
Percentage of exercise price per share of stock options			100%
Percentage of minimum exercise price, holding more than 10% of voting power			110%
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%
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 opti

Stock-based awards - Stock option valuation (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Assumptions to determine grant-date fair value of stock options granted
Expected term (in years)	5 years 3 months 18 days	5 years 9 months 7 days
Expected volatility	74.59%	72.17%
Weighted average risk-free interest rate	2.71%	1.19%
Expected dividend yield	0%	0%

Stock based awards - Stock opti

Stock based awards - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Number of Options
Balance Outstanding, Beginning of the period (in shares)	5,221,094
Options granted ( in shares)	1,355,673
Options exercised ( in shares)	(559,145)
Options cancelled (in shares)	(237,618)
Balance Outstanding, End of the period (in shares)	5,780,004	5,221,094
Vested and expected to vest ( in shares)	5,780,004
Exercisable ( in shares)	3,670,458
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)	28.76
Weighted-average exercise price, Exercised (in dollars per share)	9.37
Weighted-Average Exercise price, cancelled (in dollars per share)	23.09
Weighted-average exercise price, End of the period (in dollars per share)	18.88	$ 15.49
Weighted-average exercise price, Vested and expected to vest at end of the period (in dollars per share)	14.37
Weighted-average exercise price, Exercisable ( in dollars per share )	$ 18.88
Weighted-Average remaining contractual term (years) and Aggregate Intrinsic Value
Weighted-average remaining contractual term outstanding (in years)	7 years 9 months 18 days	8 years 2 months 12 days
Weighted-average remaining contractual term vested and expected to vest (in years)	7 years 2 months 8 days
Weighted-average remaining contractual term , Options Exercisable(in years)	7 years 9 months 18 days
Aggregate Intrinsic Value Balance outstanding	$ 207,611	$ 36,168
Aggregate Intrinsic Value Vested and Expected to vest	148,416
Aggregate Intrinsic Value Exercisable	$ 207,611
Weighted average grant-date fair value per share of stock options granted	$ 28.76	$ 13.98

Stock-based awards - Summary of

Stock-based awards - Summary of Restricted Stock activity (Details) - Restricted Stock Units (RSUs) [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Underlying shares, Granted | shares	129,131
Balance Outstanding, End of the period (in shares) | shares	129,131
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-Average Grant Date Fair Value per Share, Granted | $ / shares	$ 42.95
Weighted-Average Grant Date Fair Value per Share, End of the period | $ / shares	$ 42.95
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted-Average remaining contractual term (years)	2 years 25 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value (000's) | $	$ 7,076

Stock based awards - Stock-base

Stock based awards - Stock-based compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Stock-based compensation
Total stock-based compensation expense	$ 23,243	$ 10,054
Research and development expense
Stock-based compensation
Total stock-based compensation expense	8,096	3,054
General and administrative expense
Stock-based compensation
Total stock-based compensation expense	$ 15,147	$ 7,000

Amgen license agreement (Detail

Amgen license agreement (Details) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Dec. 31, 2022	Dec. 31, 2021
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share Issued value under agreement				$ 24,647,000
Research and development expense				85,284,000	$ 81,759,000
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
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%

Income taxes - Textual (Details

Income taxes - Textual (Details) - USD ($)		12 Months Ended
	Jun. 29, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Income tax benefit related to operating losses and research and development tax credits		$ 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
Net operating loss carry forwards		68,450,000	56,128,000
Deferred Tax Assets, Tax Credit Carryforwards, Research		7,704,000	4,522,000
Increase (Decrease) in Valuation Allowance		41,837,000	30,626,000
Gross unrecognized tax benefit		2,110,000	$ 1,313,000	$ 644,000
Accrued interest or penalties related to uncertain tax positions		0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards		248,406,000
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		245,963,000
Deferred Tax Assets, Tax Credit Carryforwards, Research		8,827,000
NOL carryforwards that expire		2,118,000
Research and development tax credit derecognized		$ 87,000
Federal | Research and development expense
Operating Loss Carryforwards [Line Items]
Research and development expenditures amortization period		5 years
Capitalization of expenditure net of amortization, amount		$ 57,658,000
Foreign | Research and development expense
Operating Loss Carryforwards [Line Items]
Research and development expenditures amortization period		15 years
Capitalization of expenditure net of amortization, amount		$ 14,728,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards		235,472,000
Deferred Tax Assets, Tax Credit Carryforwards, Research		1,249,000
NOL carryforwards that expire		3,632,000
Research and development tax credit derecognized		$ 43,000

Income taxes - Current income t

Income taxes - Current income tax provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Deferred income tax benefit:
Federal	$ 27,269	$ 23,352
State	14,568	7,274
Total deferred income tax benefit	41,837	30,626
Change in deferred tax asset valuation allowance	$ 41,837	$ 30,626

Income taxes - Income tax rate

Income taxes - Income tax rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21%	21%
State income taxes, net of federal benefit	13%	7.20%
Research and development tax credits	2.40%	2%
Other permanent differences	0.80%	(0.10%)
Change in deferred tax asset valuation allowance	(37.20%)	(30.10%)

Income taxes - Deferred tax (De

Income taxes - Deferred tax (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Net operating loss carry forwards	$ 68,450	$ 56,128
Research and development tax credit carry forwards	7,704	4,522
License fees	3,355	3,523
Stock based compensation	8,974	3,716
Capitalized research and experimentation costs	20,803
Accruals, reserves and other	191	151
Total deferred tax assets	109,477	68,040
Valuation allowance	108,690	66,853	$ 36,227
Net deferred tax assets	787	1,187
Deferred tax liabilities
Prepaid expenses	787	1,187
Net deferred tax liabilities	$ 787	$ 1,187

Income taxes - Valuation allowa

Income taxes - Valuation allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Valuation allowance as of January 1,	$ (66,853)	$ (36,227)
Decreases recorded as a benefit to income tax provision	(41,837)	(30,626)
Valuation allowance as of December 31,	$ (108,690)	$ (66,853)

Income taxes - Unrecognized tax

Income taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at the beginning	$ 1,313	$ 644
Increases related to prior year tax positions	51	66
Increases related to current year tax positions	746	603
Balance at the ending	$ 2,110	$ 1,313

Net loss per share - Basic and

Net loss per share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss	$ (112,033)	$ (100,777)
Denominator:
Weighted average common shares outstanding, basic	38,984,772	34,827,385
Weighted average common shares outstanding, diluted	38,984,772	34,827,385
Net loss per share, basic	$ (2.87)	$ (2.89)
Net loss per share, diluted	$ (2.87)	$ (2.89)
Number of weighted average restricted common stock	0	8,127

Net loss per share - Anti-Dilut

Net loss per share - Anti-Diluted (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total	6,092,733	5,221,094
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	5,780,004	5,221,094
Unvested Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from the calculation of diluted earnings per share, total	129,131
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
Warrants Available For Future Grant
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

Commitments and contingencies_2

Commitments and contingencies (Details) $ in Thousands	Dec. 31, 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	$ 7,239
Total lease liability	1,310
Operating lease liability, noncurrent	$ 1,079	$ 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	$ 231

Commitments and contingencies -

Commitments and contingencies - Maturities Of Operating Leases (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Lessee, Operating Lease, Liability, to be Paid [Abstract]
2023	$ 321
2024	331
2025	341
2026	351
2027	208
Total future minimum lease payments	1,552
Less imputed interest	(242)
Present value of operating lease liabilities	$ 1,310

Commitments and contingencies_3

Commitments and contingencies - Components of operating lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating lease expense:
Total operating lease cost	$ 440	$ 341
Other information:
Cash paid for amounts included in the measurement of operating lease liability	$ 312	$ 303
Weighted average remaining lease term	4 years 7 months 6 days	5 years 7 months 6 days
Weighted average discount rate	7.60%	7.60%
General and administrative expense
Operating lease expense:
Operating lease cost	$ 324	$ 324
Short-term lease cost	58
Variable operating lease cost	$ 58	$ 17

Subsequent event - Textual (Det

Subsequent event - Textual (Details) - USD ($) $ in Thousands		12 Months Ended
	Mar. 10, 2023	Dec. 31, 2022
Subsequent Event [Line Items]
Proceeds from term loan		$ 10,000
Subsequent Event | Hercules Capital, Inc
Subsequent Event [Line Items]
Issued warrants to purchase shares of common stock	45,898
Subsequent Event | Hercules Capital, Inc | Term Loan
Subsequent Event [Line Items]
Proceeds from term loan	$ 15,000