Akero Therapeutics (AKRO) 10-K25 Feb 222021 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2021	Feb. 15, 2022	Jun. 30, 2021
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
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	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
ICFR Auditor Attestation Flag	true
Entity Common Stock, Shares Outstanding		35,012,935
Entity Public Float			$ 768,216,344
Entity Central Index Key	0001744659
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34
Auditor Location	Parsippany, NJ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 150,483	$ 187,242
Short-term marketable securities	37,775	81,145
Prepaid expenses and other current assets	5,324	2,958
Total current assets	193,582	271,345
Property and equipment, net	90	131
Right of use asset	1,459	1,662
Other assets, noncurrent	417	201
Total assets	195,548	273,339
Current liabilities:
Accounts payable	6,706	3,428
Accrued expenses and other current liabilities	18,422	9,683
Total current liabilities	25,128	13,111
Operating lease liability, noncurrent	1,311	1,516
Total liabilities	26,439	14,627
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.0001 par value, 150,000,000 shares authorized as of December 31, 2021 and December 31, 2020; 34,900,727 and 34,741,649 shares issued and outstanding as of December 31, 2021 and December 31, 2020, respectively	4	4
Additional paid-in capital	479,436	468,238
Accumulated other comprehensive loss	(27)	(3)
Accumulated deficit	(310,304)	(209,527)
Total stockholders' equity	169,109	258,712
Total liabilities and stockholders' equity	$ 195,548	$ 273,339

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Condensed Consolidated Balance Sheets
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	34,900,727	34,741,649
Common stock, shares outstanding	34,900,727	34,741,649

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 81,759	$ 64,916	$ 37,046
General and administrative	19,127	15,238	8,605
Total operating expenses	100,886	80,154	45,651
Loss from operations	(100,886)	(80,154)	(45,651)
Other income	109	947	1,896
Net loss	(100,777)	(79,207)	(43,755)
Net unrealized (loss) gain on short-term marketable securities	(24)	3	(6)
Comprehensive loss	$ (100,801)	$ (79,204)	$ (43,761)
Net loss per common share, basic and diluted	$ (2.89)	$ (2.52)	$ (2.90)
Net loss per common share, diluted	$ (2.89)	$ (2.52)	$ (2.90)
Weighted-average number of shares used in computing net loss per common share, basic and diluted	34,827,385	31,463,248	15,070,728
Weighted-average number of shares used in computing net loss per common share, diluted	34,827,385	31,463,248	15,070,728

Consolidated Statements of Rede

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders Equity (Deficit) - USD ($) $ in Thousands	Redeemable convertible preferred stock.	Common Stock	Additional Paid-In-Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit	Total
Balance at beginning at Dec. 31, 2018	$ 124,728
Balance at beginning at Dec. 31, 2018			$ 36,646		$ (86,565)	$ (49,919)
Balance at beginning (in shares) at Dec. 31, 2018		238,986
Balance at beginning (in shares) at Dec. 31, 2018	64,730,410
Conversion of convertible preferred stock into common stock upon closing of public offering	$ (124,728)	$ 2	124,726			124,728
Conversion of convertible preferred stock into common stock upon closing of public offering (in shares)	(64,730,410)	(21,056,136)
Exercise of stock options			130			130
Exercise of stock options (in shares)		164,503
Vesting of restricted stock			240			240
Issuance of common stock pursuant to ESPP purchases			85			85
Issuance of common stock pursuant to ESPP purchases (in shares)		4,505
Stock-based compensation expense			1,770			1,770
Issuance of stock		$ 1	95,452			95,453
Issuance of stock (in shares)		6,612,500
Net unrealized (loss) gain on short-term marketable securities				$ (6)		(6)
Net loss					(43,755)	(43,755)
Balance at ending at Dec. 31, 2019		$ 3	259,049	(6)	(130,320)	128,726
Balance at ending (in shares) at Dec. 31, 2019		28,567,837
Issuance of common stock upon closing of secondary public offering, net of issuance costs and underwriting fees		$ 1	202,553			202,554
Issuance of common stock upon closing of secondary public offering, net of issuance costs and underwriting fees (shares)		6,012,390
Exercise of stock options			303			303
Exercise of stock options (in shares)		150,343
Vesting of restricted stock			61			61
Issuance of common stock pursuant to ESPP purchases			198			198
Issuance of common stock pursuant to ESPP purchases (in shares)		11,079
Stock-based compensation expense			6,022			6,022
Disgorgement of stockholders' short-swing profits, net			52			52
Net unrealized (loss) gain on short-term marketable securities				3		3
Net loss					(79,207)	(79,207)
Balance at ending at Dec. 31, 2020		$ 4	468,238	(3)	(209,527)	$ 258,712
Balance at ending (in shares) at Dec. 31, 2020		34,741,649
Balance at beginning (in shares) at Dec. 31, 2020						0
Exercise of stock options			750			$ 750
Exercise of stock options (in shares)		140,128				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 (loss) gain on short-term marketable securities				(24)		(24)
Net loss					(100,777)	(100,777)
Balance at ending at Dec. 31, 2021		$ 4	$ 479,436	$ (27)	$ (310,304)	$ 169,109
Balance at ending (in shares) at Dec. 31, 2021		34,900,727

Consolidated Statements of Re_2

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Condensed Consolidated Statements of Stockholders' Equity (Deficit)
Net issuance costs and underwriting fees	$ 906	$ 10,348

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (100,777)	$ (79,207)	$ (43,755)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	10,054	6,022	1,770
Depreciation	41	17
Non-cash lease expense	203	196
Net amortization of premiums and discounts on short-term investments	1,066	83	(104)
Unrealized foreign exchange gain and loss	5
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,101)	(1,378)	(507)
Accounts payable	3,273	2,481	(426)
Accrued expenses and other current liabilities	8,737	1,122	7,395
Other liabilities		(2)
Operating lease liability	(182)	(138)
Net cash used in operating activities	(79,681)	(70,804)	(35,627)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of short-term marketable securities	(43,561)	(115,037)	(71,513)
Proceeds from sales of short-term marketable securities		9,864
Proceeds from maturities of short-term marketable securities	85,841	95,560
Purchase of property and equipment		(148)
Net cash provided by (used in) investing activities	42,280	(9,761)	(71,513)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of common stock in follow-on public offering, net of issuance costs and underwriting fees		202,554
Proceeds from the issuance of common stock in initial public offering, net of issuance costs and underwriting fees			95,452
Proceeds from the exercise of stock options	750	303	130
Proceeds from the issuance of common stock pursuant to employee stock purchase plan purchases	373	198	85
Proceeds from the disgorgement of stockholders' short-swing profits, net		52
Proceeds from the early exercise of stock options in exchange for restricted common stock			321
Payment of deferred offering costs	(521)
Net cash provided by financing activities	602	203,107	95,988
Net (decrease) increase in cash, cash equivalents and restricted cash	(36,799)	122,542	(11,152)
Cash, cash equivalents and restricted cash at the beginning of the period	187,390	64,848	76,000
Cash, cash equivalents and restricted cash at the end of the period	150,591	187,390	64,848
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Right of use asset obtained in exchange for operating lease liability		1,751
Change in net unrealizable (loss) gain on marketable securities	$ (24)	3	(6)
Remeasurement of right of use asset and operating lease liability		$ 173
Conversion of convertible preferred stock into common stock			$ 124,728

Nature of the business and basi

Nature of the business and basis of presentation	12 Months Ended
Nature of the business and basis of presentation	Dec. 31, 2021
Nature of the business and basis of presentation
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 developing transformational treatments for patients with serious metabolic diseases marked by high unmet medical need, including non-alcoholic steatohepatitis (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, EFX, is 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 pre-cirrhotic patients with F2-F3 fibrosis and the SYMMETRY study in cirrhotic patients with compensated F4 fibrosis. The Company previously conducted a Phase 2a clinical trial, the BALANCED study, to evaluate EFX in the treatment of biopsy-confirmed NASH patients. The main portion of this study in patients with F1-F3 fibrosis showed EFX’s potential to reverse fibrosis, resolve NASH, improve liver health, improve glycemic control and improve lipoprotein profile. An expansion cohort in patients with cirrhotic NASH (F4, compensated) showed comparable results. Based on clinical data to date, the Company believes EFX has the potential to be a highly differentiated, best-in-class FGF21 analog and foundational NASH monotherapy. 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 have been reflected. Initial public offering On June 24, 2019, Akero completed its initial public offering or 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 payable by the Company, which were $2,942. Upon the closing of the IPO, all outstanding shares of redeemable convertible preferred stock converted into 21,056,136 shares of common stock (see Note 6). In connection with the completion of its IPO in June 2019, the Company amended its certificate of incorporation to authorize the issuance of up to 150,000,000 shares of $0.0001 par value common stock and 10,000,000 shares of $0.0001 par value preferred stock designated as undesignated preferred stock. Reverse stock split On June 6, 2019, the Company effected a one-for-3.07418 reverse stock split of the Company’s common stock. All common stock, stock options and per share information presented have been adjusted to reflect the reverse stock split on a retroactive basis for all periods presented. There was no change in the par value of the Company’s common stock. The ratio by which shares of preferred stock are convertible into shares of common stock was adjusted to reflect the effects of the reverse stock split. 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) Since its inception, the Company has funded its operations primarily with proceeds from sales of redeemable convertible preferred stock and most recently with proceeds from its IPO in June 2019 and a follow-on public offering of its common stock in July 2020. The Company has incurred recurring losses since its inception, including a net loss of $100,777, $79,207 and $43,755 for the years ended December 31, 2021, 2020 and 2019, respectively. In addition, as of December 31, 2021, the Company had an accumulated deficit of $310,304. The Company expects to continue to generate operating losses for the foreseeable future. As of February 25, 2022, the issuance date of these consolidated financial statements, the Company expects that its existing cash, cash equivalents and short-term marketable securities of $188,258 as of December 31, 2021, 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 beyond this time 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
Summary of significant accounting policies	Dec. 31, 2021
Summary of significant accounting policies
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 accrual of research and development expenses, stock-based compensation expense, the valuations of common stock 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 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 income (loss) on the consolidated balance sheets. The amortized cost of debt 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, an estimate of expected credit losses is made. The credit-related impairment amount is recognized in the consolidated statements of operations. Credit losses are recognized through the use of an allowance for credit losses account in the consolidated balance sheet and 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, 2021, 2020, and 2019. Restricted cash As of December 31, 2021 and 2020 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 2021 and 2020 consolidated balance sheets (see Note 12). As of December 31, 2020, the Company was required to maintain a separate cash balance of $40 to collateralize corporate credit cards with a bank, which are classified within other current assets (non-current) on the consolidated balance sheets. Concentrations of credit risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and short-term marketable securities. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company deposits its cash investments in financial institutions that it believes have high credit quality and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. At December 31, 2021 and 2020, all of the Company's cash, cash equivalents and short-term investments were held at one accredited financial Property and equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is provided using the straight-line method over the estimated useful lives of the assets, which is three years for furniture and equipment. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the improvements. Depreciation and amortization begin at the time the asset is placed in service. Leases Leases (Topic 842) Effective January 1, 2020 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 elected, as allowed under Topic 842 (or “ASC 842”), 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. In accordance with ASC 842, components of a lease should be split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) must be allocated, based on the respective relative fair values, to the lease components and non-lease components. Entities may elect not to separate lease and non-lease components. Accordingly, entities making this election would account for each lease component and related non-lease component together as a single lease component. The Company has elected to account for lease and non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only. ASC 842 allows for the use of judgment in determining whether the assumed lease term is for a major part of the remaining economic life of the underlying asset and whether the present value of lease payments represents substantially all of the fair value of the underlying asset. The Company applies the bright line thresholds referenced in ASC 842 to assist in evaluating leases for appropriate classification. The aforementioned bright lines are applied consistently to the Company’s leases. 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. Leases (Topic 840) Prior to the Adoption of Topic 842 The Company entered into lease agreements for office facilities which were classified as operating leases. Rent expense was recognized on a straight-line basis over the noncancelable term of the lease and, accordingly, the Company recorded the difference between cash rent payments and the recognition of rent expense as a deferred rent liability, which was included within accrued expenses and other current liabilities (short-term portion) and other liabilities (long-term portion) on the consolidated balance sheet. Segment information The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company's singular focus is developing and commercializing transformative treatments for serious metabolic diseases, with an initial focus on NASH. The Company’s chief operating decision-maker, its Chief Executive Officer (CEO), reviews the Company’s operating results on an aggregate basis for purposes of allocating resources and evaluating financial performance. 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 Costs incurred i n obtaining technology licenses are charged immediately to research and development expense if the technology licensed has not reached technological feasibility and has no alternative 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. Patent costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses. Stock-based compensation The Company measures all stock-based awards granted to employees and nonemployees based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company recognizes stock-based compensation expense for awards that contain performance-based conditions using the accelerated attribution method when management determines it is probable that the performance condition will be satisfied.The Company accounts for forfeitures as they occur. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model. Prior to the Company’s initial public offering, the exercise price for all stock options granted was at the estimated fair value of the underlying common stock as determined on the date of grant by the Company’s board of directors. 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 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 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 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 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 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. Deferred offering costs Deferred offering costs, which consist of direct incremental legal, consulting, banking and accounting fees relating to Company's secondary offering or At-the-market (ATM) program, are initially capitalized and subsequently offset against proceeds raised from the same offering or program within stockholders' equity. As of December 31, 2021 and 2020, there were $524 and nil capitalized deferred offering costs on the consolidated balance sheets, respectively, which are classified within Prepaid expenses and other current assets. Recently adopted accounting pronouncements On January 1, 2021, the Company adopted Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. ASU 2019-12 was effective beginning January 1, 2021. The adoption of this new standard did not have a material impact on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) (“ASU 2016-13”), which introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new “expected loss model” that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. The Company adopted ASU 2016-13 as of January 1, 2021. For available-for-sale debt securities with unrealized losses, the Company measures credit losses in a manner similar to previous U.S. GAAP, except that losses will be recognized as allowances instead of reductions in the amortized cost of the debt securities. The adoption of ASU 2016-13 did not have a material impact on the consolidated financial statements.

Fair value of financial assets

Fair value of financial assets and liabilities	12 Months Ended
Fair value of financial assets and liabilities	Dec. 31, 2021
Fair value of financial assets and liabilities
Fair value of financial assets and liabilities	3. Fair value of financial assets and liabilities 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. Observable inputs are inputs that market participants would use in pricing a financial asset or liability based on market data obtained from sources independent of the Company. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ● Level 1—Quoted prices in active markets for identical assets or liabilities. ● Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ● Level 3—Unobservable inputs that are supported by little or no market activity that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The following table summarizes our financial assets measured at fair value on a recurring basis as of December 31, 2021 and 2020: 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 $ — December 31, 2020 Total Level 1 Level 2 Level 3 Money market funds $ 158,023 $ 158,023 $ — $ — Commercial paper 47,955 — 47,955 — Corporate debt securities 33,190 — 33,190 — $ 239,168 $ 158,023 $ 81,145 $ — Commercial paper and 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.

Short-term marketable securitie

Short-term marketable securities	12 Months Ended
Short-term marketable securities	Dec. 31, 2021
Short-term marketable securities
Short-term marketable securities	4. Short-term marketable securities The following is a summary of short-term marketable securities presented on the Company’s consolidated balance sheet as of December 31, 2021 and 2020 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 December 31, 2020 Amortized cost Gross unrealized gains Gross unrealized losses Credit losses Fair value Money market funds $ 158,023 $ — $ — $ — $ 158,023 Commercial paper 47,955 — — — 47,955 Corporate debt securities 33,193 — (3) — 33,190 $ 239,171 $ — $ (3) $ — $ 239,168 Cash equivalents $ 158,023 Short-term marketable securities 81,145 $ 239,168 As of December 31, 2021 and 2020, 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
Accrued expenses and other current liabilities	Dec. 31, 2021
Accrued expenses and other current liabilities
Accrued expenses and other current liabilities	5. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following: Year Ended December 31, 2021 2020 Accrued external research and development expenses $ 17,539 $ 8,740 Accrued employee compensation and benefits 554 495 Accrued legal and professional fees 124 154 Short-term lease liability and other 205 294 $ 18,422 $ 9,683

Redeemable convertible preferre

Redeemable convertible preferred stock	12 Months Ended
Redeemable convertible preferred stock	Dec. 31, 2021
Redeemable convertible preferred stock
Redeemable convertible preferred stock	6. Redeemable convertible preferred stock Upon completion of the Company’s IPO on June 24, 2019, 50,858,462 of the Company’s Series A redeemable convertible preferred stock and 13,871,948 shares of the Company’s Series B redeemable convertible preferred were converted into 21,056,136 shares of common stock and the related carrying value of $124,728 was reclassified to common stock in the amount of $2 and additional paid-in capital in the amount of $124,726. Accordingly, there were no shares of redeemable convertible preferred stock outstanding as of December 31, 2021 or 2020.

Stockholder's equity (deficit)

Stockholder's equity (deficit)	12 Months Ended
Stockholder's equity (deficit)	Dec. 31, 2021
Stockholder's equity (deficit)
Stockholder's equity (deficit)	7. Stockholders’ equity (deficit) Common stock As of December 31, 2021 and 2020, 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, which may be declared by the board of directors. Through December 31, 2021, 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 payable 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 (see Note 6). On July 10, 2020, the Company completed a follow-on public offering at which time the Company issued 6,012,390 shares of common stock, including the exercise in full by the underwriters of their option to purchase up to 784,224 additional shares of common stock, at a public offering price of $36.00 per share. The Company received $203,460 net of underwriting discounts and commissions, but before deducting offering costs paid by the Company, which were $906. On May 18, 2021, the Company filed a Form S-3 Registration Statement and the accompanying prospectus activating an At-the-market, or ATM, facility by entering into a sales agreement with J.P. Morgan Securities LLC, relating to shares of the Company’s common stock offered. Pursuant to the terms of the sales agreement, the Company may offer and sell shares of common stock, having an aggregate price of up to $100.0 million, 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, 2021, the Company did not make any sales under the ATM facility. As of December 31, 2021 and December 31, 2020, there were 34,900,727 and 34,741,649 shares of common stock issued outstanding The following shares of common stock were reserved for issuance as follows: Year Ended December 31, 2021 2020 Options outstanding under the 2018 Stock Option and Grant Plan 2,011,891 2,148,019 Options outstanding under the 2019 Stock Option and Incentive Plan 3,209,203 1,585,293 Options available for future grant 1,889,299 2,127,544 Common stock available for ATM program 5,000,000 — 2019 Employee Stock Purchase Plan 872,429 543,963 12,982,822 6,404,819 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, 2021 or 2020. Restricted common stock In March 2017, the Company issued an aggregate of 226,400 shares of restricted common stock under restricted stock agreements with the founders. Pursuant to the terms of the agreements, the restricted common stock was initially subject to a vesting schedule over a four-year period commencing in January 2017 and culminating in January 2021. In March 2018, the Company amended the restricted stock agreements such that the restricted common stock became subject to a vesting schedule over a two-year period commencing in May 2018 and culminating in June 2020. As of December 31, 2020, all restricted stock issued to the founders is fully vested. In April, June and July 2019, the Company amended certain option grant agreements granted under the Company’s 2018 Stock Option and Grant Plan to allow the holders the right to early exercise unvested options, subject to a repurchase right held by the Company equal to the lesser of the original exercise price per share or the fair value of the shares on the repurchase date. The unvested shares issued as a result of the early exercise are deemed restricted stock pursuant to a restricted stock agreement and a vesting schedule identical to the vesting schedule of the original grant agreement. The proceeds related to unvested restricted common stock are recorded as liabilities until the stock vests, at which point they are reclassified to additional paid-in capital. Common shares issued for the early exercise of options are included in issued and outstanding shares. As of December 31, 2021, there were no shares of unvested restricted common stock from the early exercise of stock options which were subject to repurchase by the Company The following table summarizes restricted stock activity since December 31, 2019: Grant-Date Fair Number of Shares Value Unvested restricted common stock as of December 31, 2019 80,190 $ — Early exercise of unvested stock options 491,207 0.65 Shares vesting (416,248) 0.65 Unvested restricted common stock as of December 31, 2020 155,149 0.52 Shares vesting (155,149) 0.52 Unvested restricted common stock as of December 31, 2021 — $ -

Stock-based awards

Stock-based awards	12 Months Ended
Stock-based awards	Dec. 31, 2021
Stock-based awards
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 is 2,572,457, which includes the 107,635 shares transferred from the 2018 Plan, and 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 thereafter through January 1, 2029, by the least of (i) 1% of the 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 were as follows, presented on a weighted average basis: Year Ended December 31, 2021 2020 2019 Expected term (in years) 5.77 6.00 6.00 Expected volatility 72.17 % 73.38 % 73.75 % Weighted average risk-free interest rate 1.19 % 0.65 % 2.12 % Expected dividend yield 0.00 % 0.00 % 0.00 % Stock options The following table summarizes the Company’s stock option activity during 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, 2020 3,733,312 $ 12.15 8.53 52,498 Options granted 1,648,855 $ 22.29 Options exercised (140,128) $ 5.36 Options cancelled (20,945) $ 23.91 Balance outstanding, December 31, 2021 5,221,094 $ 15.49 8.20 $ 36,168 Vested and expected to vest, December 31, 2021 4,610,548 $ 14.75 7.97 $ 36,137 Exercisable, December 31, 2021 2,115,158 $ 10.45 7.29 $ 24,365 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, 2021, 2020 and 2019 was $13.98, $17.07 and $8.34, 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 certain clinical, manufacturing and regulatory milestones. The Company intends to begin to recognize stock compensation expense for these awards at the time that the related performance milestones are deemed probable to occur. The Company did not recognize any stock compensation expense related to these awards in 2021. Stock-based compensation The following table summarizes the Company’s stock-based compensation expense for the years ended December 31, 2021, 2020 and 2019: Year Ended December 31, 2021 2020 2019 Classified within research and development expense $ 3,054 $ 1,633 $ 485 Classified within general and administrative expense 7,000 4,389 1,285 Total stock-based compensation expense $ 10,054 $ 6,022 $ 1,770 As of December 31, 2021, total unrecognized compensation cost related to the unvested stock-based awards was $35,954, including performance-based awards with unrecognized compensation costs of $7,959.

Amgen license agreement

Amgen license agreement	12 Months Ended
Amgen license agreement	Dec. 31, 2021
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 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 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 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 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 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 During the year ended December 31, 2021 and 2020, the Company did not record any research and development expense in connection with the Amgen Agreement. During the year ended December 31, 2019, the Company recorded research and development expense of $2,500 related to the achievement of a clinical milestone, as specified in the agreement.

Income taxes

Income taxes	12 Months Ended
Income taxes	Dec. 31, 2021
Income taxes
Income taxes	10. Income taxes During the years ended December 31, 2021, 2020 and 2019, the Company recorded no income tax benefits for the net operating losses incurred 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, 2021 2020 2019 Current income tax provision: Federal $ — $ — $ — State — — 24 Total current income tax provision — — 24 Deferred income tax benefit: Federal 23,352 (17,580) (9,400) State 7,274 (3,135) 688 Total deferred income tax benefit 30,626 (20,715) (8,712) Change in deferred tax asset valuation allowance (30,626) 20,715 8,712 Total provision for income taxes $ — $ — $ 24 The $24 provision for income taxes for the year ended December 31, 2019 was classified within general and administrative expense on the Consolidated Statements of Operations and Comprehensive Loss. 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, 2021 2020 2019 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 7.2 4.0 (1.6) Research and development tax credits 2.0 1.3 1.9 Other permanent differences (0.1) (0.1) 0.1 Change in deferred tax asset valuation allowance (30.1) (26.2) (19.9) Effect of Section 382 limitation - - (1.5) Effective income tax rate - % - % - % Net deferred tax assets as of December 31, 2021 and 2020 consisted of the following: December 31, 2021 2020 Deferred tax assets: Net operating loss carry forwards $ 56,128 $ 29,951 Research and development tax credit carry forwards 4,522 2,096 License fees 3,523 3,364 Stock based compensation 3,716 1,402 Accruals, reserves and other 151 63 68,040 36,876 Valuation allowance (66,853) (36,227) Net deferred tax assets 1,187 649 Deferred tax liabilities: Prepaid expenses (1,187) (649) Net deferred tax liabilities (1,187) (649) As of December 31, 2021, the Company had U.S. federal and state net operating loss carryforwards of $222,397 and $137,004, respectively, which may be available to offset future taxable income and begin to expire in 2037. The federal net operating loss carryforwards include $219,953, which may be carried forward indefinitely. As of December 31, 2021, the Company also had U.S. federal and state research and development tax credit carryforwards of $5,388 and $565, respectively, which may be available to offset future tax liabilities and begin to expire in 2033. During the year ended December 31, 2021, gross deferred tax assets, before valuation allowance, increased by $30,626, 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, 2021, 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, 2021, 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, 2021 and 2020. 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, 2021 and 2020 are as follows: 2021 2020 Valuation allowance as of January 1, $ (36,227) $ (15,512) Increases recorded to income tax provision — Decreases recorded as a benefit to income tax provision (30,626) (20,715) Valuation allowance as of December 31, $ (66,853) $ (36,227) As of December 31, 2021, the Company had gross unrecognized tax benefits of $1,313, 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, 2021, the Company had not 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, 2021, the Company will file income tax returns in the U.S., California, Connecticut, Illinois, Massachusetts, Maryland, New York, North Carolina and Pennsylvania, 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 2017 to the present. A reconciliation of the beginning and ending unrecognized tax benefits for the years ended December 31, 2021, 2020 and 2019 is as follows Balance at December 31, 2018 $ — Increases related to current year tax positions 237 Balance at December 31, 2019 $ 237 Increases related to current year tax positions 407 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 $1,000 or more. Since the Company is not expected to generate California source taxable income of more than $1,000, no material impact is anticipated at this time. On January 1, 2021, the Company adopted Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12). This new guidance simplifies the accounting for income taxes by removing certain exceptions to general principles, clarifying requirements and including amendments to improve consistent application of the guidance. The guidance specifically removes the exception to the incremental approach for intra period tax allocation when there is a loss from continuing operations and income or a gain from other items, such as discontinued operations or other comprehensive income. The guidance also requires an entity to recognize a franchise tax that is partially based on income as an income-based tax and to account for any other amounts incurred as a non-income based tax. The guidance is effective for the Company beginning January 1, 2021 using a prospective approach. Historically, the Company has included capital and gross receipts-based taxes as above the line taxes. Thus, the adoption will have no material impact to the Company. Additionally, the changes to the intraperiod allocation and treatment of discontinued operations or other comprehensive income have no impact to the Company.

Net loss per share

Net loss per share	12 Months Ended
Net loss per share	Dec. 31, 2021
Net loss per share
Net loss per share	11. Net loss per share Basic and diluted net loss per share was calculated as follows: Year Ended December 31, 2021 2020 2019 Numerator: Net loss $ (100,777) $ (79,207) $ (43,755) Denominator: Weighted average common shares outstanding, basic and diluted 34,827,385 31,463,248 15,070,728 Net loss per share, basic and diluted $ (2.89) $ (2.52) $ (2.90) The Company excluded 8,127 shares, 31,215 shares and 49,568 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, 2021, 2020 and 2019, respectively, because those s Year Ended December 31, 2021 2020 2019 Options to purchase common stock 5,221,094 3,733,312 3,096,555 Unvested restricted common stock — 33,614 155,149 5,221,094 3,766,926 3,251,704

Commitments and contingencies

Commitments and contingencies	12 Months Ended
Commitments and contingencies	Dec. 31, 2021
Commitments and contingencies
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. As of February 2022, COVID-19 has spread to other countries, including Europe and the United States, and has been declared a pandemic by the World Health Organization. Efforts to contain the spread of COVID-19 have intensified and the United States, Europe and Asia have implemented severe travel restrictions, social distancing requirements, stay-at-home orders and have delayed the commencement of non-COVID-19-related clinical trials, among other restrictions. The Company’s financial results for the years ended December 31, 2021, 2020 and 2019 were not significantly impacted by COVID-19, however, the Company cannot at this time predict the specific extent, duration, or full impact that the 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 leases In October 2018, the Company entered into a lease agreement for office space in South San Francisco, California. In March 2019, the Company amended this lease agreement (the “First Amendment”) to extend the term of the lease and expand the square footage of the existing leased office space. On May 7, 2020, the Company entered into an agreement to effectuate an early termination of the 2018 office lease agreement in South San Francisco, California, without penalty, resulting in a non-cash reduction to the ROU asset and corresponding lease In September 2019, the Company entered into an agreement to use office space in Cambridge, Massachusetts. The agreement was for an initial 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 determined that the lease should be classified as an operating lease. 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 expense when incurred. As of December 31, 2021, maturities of the Company’s operating lease liabilities were as follows: 2022 $ 312 2023 321 2024 331 2025 341 2026 351 2027 208 Total future minimum lease payments 1,864 Less imputed interest (348) Present value of operating lease liabilities $ 1,516 As of December 31, 2021, the total lease liability For the year ended December 31, 2021, the components of operating lease cost were as follows: Year Ended December 31, 2021 2020 Lease cost: Statement of Operations Classification: Operating lease cost General and administrative expense $ 324 $ 267 Variable operating lease cost General and administrative expense 17 43 Short-term lease cost Research and development expense — 32 Total operating lease cost $ 341 $ 342 Other information: Cash paid for amounts included in the measurement of operating lease liability $ 303 $ 210 Weighted average remaining lease term 5.6 6.6 Weighted average discount rate 7.6% 7.6% Prior to the Company’s adoption of ASC 842 on January 1, 2020, the Company recognized rent expense on a straight-line basis over the respective lease periods and recorded rent expense of $305 for the year ended December 31, 2019. As of December 31, 2019, future minimum commitments due under the Company’s leases totaled $401, of which $321 was due in 2020 and $80 was due in 2021. Research and manufacturing commitments The Company has entered into agreements with CROs and CMOs to provide services in connection with its nonclinical studies and clinical trials and to manufacture clinical development materials. As of December 31, 2021, the Company had non-cancelable purchase commitments under these agreements totaling $7,420. 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, 2021, 2020 or 2019. 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 intends to expense as incurred the costs related to such legal proceedings if they should arise.

Related parties

Related parties	12 Months Ended
Related parties	Dec. 31, 2021
Related parties
Related parties	13. Related parties Apple Tree Life Sciences, Inc. The principal and founding member of Apple Tree Life Sciences, Inc. ("Apple Tree"), one of the Company’s early investors, is a member of the Company’s board of directors. The Company's founders, including the current Executive Vice President and Chief Operating Officer and Chief Scientific Officer, were formerly employees of Apple Tree. During the years ended December 31, 2021, 2020 and 2019, the Company incurred fees for certain general and administrative services from Apple Tree totaling $0 , $0 and $20 , respectively. December 31, 2021 2020 Atlas Venture Life Science Advisors, LLC A partner of Atlas Venture Life Science Advisors (“Atlas”), one of the Company’s investors, was a member of the Company’s board of directors up until December 31, 2021. During the year ended December 31, 2019 the Company incurred fees under the use and occupancy agreement with Atlas totaling December 31, 2021 2020

Benefit plans

Benefit plans	12 Months Ended
Benefit plans	Dec. 31, 2021
Benefit plans
Benefit plans	14. Benefit plans The Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Matching contributions to the plan may be made at the discretion of the Company’s board of directors. The Company did not make any matching contributions to the plan during the years ended December 31, 2021, 2020 and 2019.

Subsequent event

Subsequent event	12 Months Ended
Subsequent event	Dec. 31, 2021
Subsequent event.
Subsequent event	15. Subsequent events The Company evaluated subsequent events through February 25, 2022, the date on which these consolidated financial statements were available to be issued. In January 2022, the Company granted 248,376 stock options to employees at an exercise price of $21.70 , which vest upon the achievement on or before December 31, 2022 of certain clinical, manufacturing and regulatory milestones. The Company intends to begin to recognize stock compensation expense for these awards at the time that the related performance milestones are deemed probable to occur.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
Summary of significant accounting policies (Policies)	Dec. 31, 2021
Summary of significant accounting policies
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 accrual of research and development expenses, stock-based compensation expense, the valuations of common stock 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
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 income (loss) on the consolidated balance sheets. The amortized cost of debt 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, an estimate of expected credit losses is made. The credit-related impairment amount is recognized in the consolidated statements of operations. Credit losses are recognized through the use of an allowance for credit losses account in the consolidated balance sheet and 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, 2021, 2020, and 2019.
Restricted cash	Restricted cash As of December 31, 2021 and 2020 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 2021 and 2020 consolidated balance sheets (see Note 12). As of December 31, 2020, the Company was required to maintain a separate cash balance of $40 to collateralize corporate credit cards with a bank, which are classified within other current assets (non-current) on the consolidated balance sheets.
Concentrations of credit risk	Concentrations of credit risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and short-term marketable securities. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company deposits its cash investments in financial institutions that it believes have high credit quality and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. At December 31, 2021 and 2020, all of the Company's cash, cash equivalents and short-term investments were held at one accredited financial
Property and equipment	Property and equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is provided using the straight-line method over the estimated useful lives of the assets, which is three years for furniture and equipment. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the improvements. Depreciation and amortization begin at the time the asset is placed in service.
Leases	Leases Leases (Topic 842) Effective January 1, 2020 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 elected, as allowed under Topic 842 (or “ASC 842”), 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. In accordance with ASC 842, components of a lease should be split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) must be allocated, based on the respective relative fair values, to the lease components and non-lease components. Entities may elect not to separate lease and non-lease components. Accordingly, entities making this election would account for each lease component and related non-lease component together as a single lease component. The Company has elected to account for lease and non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only. ASC 842 allows for the use of judgment in determining whether the assumed lease term is for a major part of the remaining economic life of the underlying asset and whether the present value of lease payments represents substantially all of the fair value of the underlying asset. The Company applies the bright line thresholds referenced in ASC 842 to assist in evaluating leases for appropriate classification. The aforementioned bright lines are applied consistently to the Company’s leases. 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. Leases (Topic 840) Prior to the Adoption of Topic 842 The Company entered into lease agreements for office facilities which were classified as operating leases. Rent expense was recognized on a straight-line basis over the noncancelable term of the lease and, accordingly, the Company recorded the difference between cash rent payments and the recognition of rent expense as a deferred rent liability, which was included within accrued expenses and other current liabilities (short-term portion) and other liabilities (long-term portion) on the consolidated balance sheet.
Segment information	Segment information The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company's singular focus is developing and commercializing transformative treatments for serious metabolic diseases, with an initial focus on NASH. The Company’s chief operating decision-maker, its Chief Executive Officer (CEO), reviews the Company’s operating results on an aggregate basis for purposes of allocating resources and evaluating financial performance.
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 Costs incurred i n obtaining technology licenses are charged immediately to research and development expense if the technology licensed has not reached technological feasibility and has no alternative
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.
Patent costs	Patent costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.
Stock-based compensation	Stock-based compensation The Company measures all stock-based awards granted to employees and nonemployees based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company recognizes stock-based compensation expense for awards that contain performance-based conditions using the accelerated attribution method when management determines it is probable that the performance condition will be satisfied.The Company accounts for forfeitures as they occur. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model. Prior to the Company’s initial public offering, the exercise price for all stock options granted was at the estimated fair value of the underlying common stock as determined on the date of grant by the Company’s board of directors. 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 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
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
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 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 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.
Deferred offering costs	Deferred offering costs Deferred offering costs, which consist of direct incremental legal, consulting, banking and accounting fees relating to Company's secondary offering or At-the-market (ATM) program, are initially capitalized and subsequently offset against proceeds raised from the same offering or program within stockholders' equity. As of December 31, 2021 and 2020, there were $524 and nil capitalized deferred offering costs on the consolidated balance sheets, respectively, which are classified within Prepaid expenses and other current assets.
Recently issued accounting pronouncements and pronouncements not yet adopted	Recently adopted accounting pronouncements On January 1, 2021, the Company adopted Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. ASU 2019-12 was effective beginning January 1, 2021. The adoption of this new standard did not have a material impact on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) (“ASU 2016-13”), which introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new “expected loss model” that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. The Company adopted ASU 2016-13 as of January 1, 2021. For available-for-sale debt securities with unrealized losses, the Company measures credit losses in a manner similar to previous U.S. GAAP, except that losses will be recognized as allowances instead of reductions in the amortized cost of the debt securities. The adoption of ASU 2016-13 did not have a material impact on the consolidated financial statements.

Fair value of financial asset_2

Fair value of financial assets and liabilities (Tables)	12 Months Ended
Fair value of financial assets and liabilities (Tables)	Dec. 31, 2021
Fair value of financial assets and liabilities
Summary of assets that are measured at fair value on a recurring basis	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 $ — December 31, 2020 Total Level 1 Level 2 Level 3 Money market funds $ 158,023 $ 158,023 $ — $ — Commercial paper 47,955 — 47,955 — Corporate debt securities 33,190 — 33,190 — $ 239,168 $ 158,023 $ 81,145 $ —

Short-term marketable securit_2

Short-term marketable securities (Tables)	12 Months Ended
Short-term marketable securities (Tables)	Dec. 31, 2021
Short-term marketable securities
Summary of short-term marketable securities	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 December 31, 2020 Amortized cost Gross unrealized gains Gross unrealized losses Credit losses Fair value Money market funds $ 158,023 $ — $ — $ — $ 158,023 Commercial paper 47,955 — — — 47,955 Corporate debt securities 33,193 — (3) — 33,190 $ 239,171 $ — $ (3) $ — $ 239,168 Cash equivalents $ 158,023 Short-term marketable securities 81,145 $ 239,168

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	12 Months Ended
Accrued expenses and other current liabilities (Tables)	Dec. 31, 2021
Accrued expenses and other current liabilities
Schedule of accrued expenses and other current liabilities	Year Ended December 31, 2021 2020 Accrued external research and development expenses $ 17,539 $ 8,740 Accrued employee compensation and benefits 554 495 Accrued legal and professional fees 124 154 Short-term lease liability and other 205 294 $ 18,422 $ 9,683

Stockholder's equity (deficit)

Stockholder's equity (deficit) (Tables)	12 Months Ended
Stockholder's equity (deficit) (Tables)	Dec. 31, 2021
Stockholder's equity (deficit)
Schedule of common stock reserved for issuance	Year Ended December 31, 2021 2020 Options outstanding under the 2018 Stock Option and Grant Plan 2,011,891 2,148,019 Options outstanding under the 2019 Stock Option and Incentive Plan 3,209,203 1,585,293 Options available for future grant 1,889,299 2,127,544 Common stock available for ATM program 5,000,000 — 2019 Employee Stock Purchase Plan 872,429 543,963 12,982,822 6,404,819
Summary of restricted stock activity	The following table summarizes restricted stock activity since December 31, 2019: Grant-Date Fair Number of Shares Value Unvested restricted common stock as of December 31, 2019 80,190 $ — Early exercise of unvested stock options 491,207 0.65 Shares vesting (416,248) 0.65 Unvested restricted common stock as of December 31, 2020 155,149 0.52 Shares vesting (155,149) 0.52 Unvested restricted common stock as of December 31, 2021 — $ -

Stock-based awards (Tables)

Stock-based awards (Tables)	12 Months Ended
Stock-based awards (Tables)	Dec. 31, 2021
Stock-based awards
Schedule of assumptions used to determine grant-date fair value of stock options granted	Year Ended December 31, 2021 2020 2019 Expected term (in years) 5.77 6.00 6.00 Expected volatility 72.17 % 73.38 % 73.75 % Weighted average risk-free interest rate 1.19 % 0.65 % 2.12 % Expected dividend yield 0.00 % 0.00 % 0.00 %
Summary of stock option activity	Weighted- Weighted- Average Average Aggregate Exercise remaining Intrinsic Number Price per contractual Value of Options Share term (years) (000's) Balance outstanding, December 31, 2020 3,733,312 $ 12.15 8.53 52,498 Options granted 1,648,855 $ 22.29 Options exercised (140,128) $ 5.36 Options cancelled (20,945) $ 23.91 Balance outstanding, December 31, 2021 5,221,094 $ 15.49 8.20 $ 36,168 Vested and expected to vest, December 31, 2021 4,610,548 $ 14.75 7.97 $ 36,137 Exercisable, December 31, 2021 2,115,158 $ 10.45 7.29 $ 24,365
Summary of stock-based compensation expense	Year Ended December 31, 2021 2020 2019 Classified within research and development expense $ 3,054 $ 1,633 $ 485 Classified within general and administrative expense 7,000 4,389 1,285 Total stock-based compensation expense $ 10,054 $ 6,022 $ 1,770

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
Income taxes (Tables)	Dec. 31, 2021
Income taxes
Schedule of current and deferred tax provision	Year Ended December 31, 2021 2020 2019 Current income tax provision: Federal $ — $ — $ — State — — 24 Total current income tax provision — — 24 Deferred income tax benefit: Federal 23,352 (17,580) (9,400) State 7,274 (3,135) 688 Total deferred income tax benefit 30,626 (20,715) (8,712) Change in deferred tax asset valuation allowance (30,626) 20,715 8,712 Total provision for income taxes $ — $ — $ 24
Schedule of reconciliation of the U.S. federal statutory income tax	Year Ended December 31, 2021 2020 2019 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 7.2 4.0 (1.6) Research and development tax credits 2.0 1.3 1.9 Other permanent differences (0.1) (0.1) 0.1 Change in deferred tax asset valuation allowance (30.1) (26.2) (19.9) Effect of Section 382 limitation - - (1.5) Effective income tax rate - % - % - %
Schedule of Net deferred tax assets	December 31, 2021 2020 Deferred tax assets: Net operating loss carry forwards $ 56,128 $ 29,951 Research and development tax credit carry forwards 4,522 2,096 License fees 3,523 3,364 Stock based compensation 3,716 1,402 Accruals, reserves and other 151 63 68,040 36,876 Valuation allowance (66,853) (36,227) Net deferred tax assets 1,187 649 Deferred tax liabilities: Prepaid expenses (1,187) (649) Net deferred tax liabilities (1,187) (649)
Schedule of changes in the valuation allowance for deferred tax assets	2021 2020 Valuation allowance as of January 1, $ (36,227) $ (15,512) Increases recorded to income tax provision — Decreases recorded as a benefit to income tax provision (30,626) (20,715) Valuation allowance as of December 31, $ (66,853) $ (36,227)
Schedule of unrecognized tax benefits roll Forward	Balance at December 31, 2018 $ — Increases related to current year tax positions 237 Balance at December 31, 2019 $ 237 Increases related to current year tax positions 407 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

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
Net loss per share (Tables)	Dec. 31, 2021
Net loss per share
Schedule of basic and diluted net loss per share attributable to common stockholders	Year Ended December 31, 2021 2020 2019 Numerator: Net loss $ (100,777) $ (79,207) $ (43,755) Denominator: Weighted average common shares outstanding, basic and diluted 34,827,385 31,463,248 15,070,728 Net loss per share, basic and diluted $ (2.89) $ (2.52) $ (2.90)
Schedule of computation of diluted net loss per share attributable to common stockholders	Year Ended December 31, 2021 2020 2019 Options to purchase common stock 5,221,094 3,733,312 3,096,555 Unvested restricted common stock — 33,614 155,149 5,221,094 3,766,926 3,251,704

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2021
Commitments and contingencies
Schedule of maturity of the Company's operating lease liabilities	2022 $ 312 2023 321 2024 331 2025 341 2026 351 2027 208 Total future minimum lease payments 1,864 Less imputed interest (348) Present value of operating lease liabilities $ 1,516
Schedule of components of operating lease expense	Year Ended December 31, 2021 2020 Lease cost: Statement of Operations Classification: Operating lease cost General and administrative expense $ 324 $ 267 Variable operating lease cost General and administrative expense 17 43 Short-term lease cost Research and development expense — 32 Total operating lease cost $ 341 $ 342 Other information: Cash paid for amounts included in the measurement of operating lease liability $ 303 $ 210 Weighted average remaining lease term 5.6 6.6 Weighted average discount rate 7.6% 7.6%

Nature of the business and ba_2

Nature of the business and basis of presentation (Details)	Jun. 24, 2019USD ($)$ / sharesshares	Jun. 06, 2019	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Subsidiary, Sale of Stock
Offering costs			$ 521,000
Reverse stock split of the common stock		3.07418
Net loss			100,777,000	$ 79,207,000	$ 43,755,000
Accumulated deficit			310,304,000	$ 209,527,000
Cash, cash equivalents and short-term marketable securities			188,258,000
Payment of deferred offering costs			$ (521,000)
IPO
Subsidiary, Sale of Stock
Public offering price (in dollars per share) \| $ / shares	$ 16
Offering costs	$ 2,942,000
Authorized Preferred stock (in shares) \| shares	10,000,000
Par value preferred stock (in dollars per share) \| $ / shares	$ 0.0001
Conversion of convertible preferred stock into common stock \| shares	21,056,136
Payment of deferred offering costs	$ (2,942,000)
Over allotment \| Maximum
Subsidiary, Sale of Stock
Offering costs	862,500
Payment of deferred offering costs	$ (862,500)

Summary of significant accoun_3

Summary of significant accounting policies - Restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary of significant accounting policies
Separate cash balance for the landlord	$ 108	$ 108
Separate cash balance to collateralize corporate credit cards with a bank		$ 40	$ 40

Summary of significant accoun_4

Summary of significant accounting policies - Property and equipment (Details)	12 Months Ended
	Dec. 31, 2021
Furniture and equipment
Property and equipment
Estimated useful lives	3 years

Summary of significant accoun_5

Summary of significant accounting policies - Deferred offering costs (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Summary of significant accounting policies
Accrued deferred offering costs	$ 524	$ 0

Fair value of financial asset_3

Fair value of financial assets and liabilities - Recurring (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 154,036	$ 239,168
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	116,261	158,023
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		47,955
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	37,775	33,190
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	116,261	158,023
Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	116,261	158,023
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	37,775	81,145
Level 2 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		47,955
Level 2 \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 37,775	$ 33,190

Fair value of financial asset_4

Fair value of financial assets and liabilities - Textual (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair value of financial assets and liabilities
Transfers from level 1 to level 2, Assets	$ 0	$ 0
Transfers from level 2 to level 1, Assets	0	0
Transfers from level 1 to level 2, Liabilities	0	0
Transfers from level 2 to level 1, Liabilities	0	0
Transfers into level 3 Assets	0	0
Transfers out of level 3 Assets	0	0
Transfers into level 3 liabilities	0	0
Transfers out of level 3 liabilities	$ 0	$ 0

Short-term marketable securit_3

Short-term marketable securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 154,063	$ 239,171
Gross unrealized losses	(27)	(3)
Fair value	154,036	239,168
Cash equivalents	116,261	158,023
Short-term marketable securities	37,775	81,145
Total	154,036	239,168
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized cost	116,261	158,023
Fair value	116,261	158,023
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized cost		47,955
Fair value		47,955
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost	37,802	33,193
Gross unrealized losses	(27)	(3)
Fair value	$ 37,775	$ 33,190

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued expenses and other current liabilities
Accrued external research and development expenses	$ 17,539	$ 8,740
Accrued employee compensation and benefits	554	495
Accrued legal and professional fees	124	154
Short-term lease liability and other	205	294
Total accrued expenses and other current liabilities	$ 18,422	$ 9,683

Redeemable convertible prefer_2

Redeemable convertible preferred stock - Textual (Details) - USD ($) $ in Thousands	Jun. 24, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2018
Temporary Equity
Preferred Stock , shares outstanding		0		0
Related carrying value of convertible preferred stock converted into common stock	$ 124,728	$ 202,554
IPO
Temporary Equity
Number of shares converted	21,056,136
Common Stock
Temporary Equity
Number of shares converted			21,056,136
Related carrying value of convertible preferred stock converted into common stock	$ 2	1
Additional Paid-In-Capital
Temporary Equity
Related carrying value of convertible preferred stock converted into common stock	$ 124,726	$ 202,553
Redeemable convertible preferred stock.
Temporary Equity
Preferred Stock , shares outstanding					64,730,410
Number of shares converted			64,730,410
Series A Preferred Stock. \| IPO
Temporary Equity
Preferred Stock , shares outstanding	50,858,462
Series B Preferred Stock \| IPO
Temporary Equity
Preferred Stock , shares outstanding	13,871,948

Stockholder's equity (deficit_2

Stockholder's equity (deficit) - Common stock (Details) $ / shares in Units, $ in Thousands	May 18, 2021USD ($)shares	Jul. 10, 2020USD ($)$ / sharesshares	Jun. 24, 2019USD ($)$ / sharesshares	Dec. 31, 2021Vote$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)shares	Jun. 18, 2019shares
Class of Stock
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 \| $					$ 202,554
Share Issued value under agreement \| $						$ 95,453
Common stock, shares issued				34,900,727	34,741,649
Common stock, shares outstanding				34,900,727	34,741,649
Common stock were reserved for issuance
Options available for future grant				12,982,822	6,404,819
Options available for future grant
Common stock were reserved for issuance
Options available for future grant				1,889,299	2,127,544
Common stock available for ATM program
Common stock were reserved for issuance
Options available for future grant	5,000,000			5,000,000
2018 Stock option and grant plan
Common stock were reserved for issuance
Options available for future grant				2,011,891	2,148,019		107,635
2019 Stock Option and Incentive plan
Common stock were reserved for issuance
Options available for future grant				3,209,203	1,585,293
2019 Employee Stock Purchase Plan
Common stock were reserved for issuance
Options available for future grant				872,429	543,963
Redeemable convertible preferred stock.
Class of Stock
Number of shares converted						64,730,410
Maximum \| Common stock available for ATM program
Class of Stock
Share Issued value under agreement \| $	$ 100,000
IPO
Class of Stock
Common stock, shares authorized			150,000,000
Common stock, par value (in dollars per share) \| $ / shares			$ 0.0001
Public offering price \| $ / shares			$ 16
Proceeds received, net of underwriting discounts and commissions \| $			$ 98,394
Offering costs \| $			$ 2,942
Number of shares converted			21,056,136
Common stock, shares issued			6,612,500
Follow Up Public Offering
Class of Stock
Number of shares issued		6,012,390
Public offering price \| $ / shares		$ 36
Proceeds received, net of underwriting discounts and commissions \| $		$ 203,460
Offering costs \| $		$ 906
Over allotment \| Maximum
Class of Stock
Number of shares issued		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) - $ / shares	1 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2021	Dec. 31, 2020
Restricted stock
Class of Stock
Shares issued (in shares)		226,400
Stock options vesting period	2 years	4 years
Undesignated Preferred Stock
Class of Stock
Preferred stock, par value (in dollars per share)			$ 0.0001
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
Undesignated Preferred Stock \| Maximum
Class of Stock
Preferred stock, shares authorized			10,000,000

Stockholder's equity (deficit_4

Stockholder's equity (deficit) - Restricted stock activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Shares
Beginning balance of unvested restricted common stock	155,149	80,190
Early exercise of unvested stock options		491,207
Shares vesting	(155,149)	(416,248)
Ending balance of unvested restricted common stock		155,149
Grant-Date Fair Value
Beginning balance of unvested restricted common stock	$ 0.52
Early exercise of unvested stock options		$ 0.65
Shares vesting	$ 0.52	0.65
Ending balance of unvested restricted common stock		$ 0.52

Stock-based awards - Textual (D

Stock-based awards - Textual (Details) - shares	Jun. 18, 2019	Jun. 30, 2019	Jan. 01, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020	Jan. 01, 2020
Share-based awards
Number of shares remained available for grant				12,982,822		6,404,819
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			2,011,891		2,148,019
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		1,142,713
Percent of shares reserved and available for issuance automatically increase annually on January 1		4.00%
Percentage of exercise price per share of stock options		100.00%
Percentage of minimum exercise price, holding more than 10% of voting power		110.00%
Stock options vesting period		4 years
2019 Employee stock purchase plan
Share-based awards
Number of shares initially reserved for issuance	273,869
Number of additional shares reserved for issuance			349,007		347,416		285,678
Percent of shares reserved and available for issuance automatically increase annually on January 1		1.00%
Number of shares reserved and available for issuance automatically increase annually on January 1 (in shares)		410,803
Maximum \| 2019 Stock option and incentive plan
Share-based awards
Term of stock option		10 years

Stock-based awards - Stock opti

Stock-based awards - Stock option valuation (Details)	12 Months Ended
Stock-based awards - Stock option valuation (Details)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assumptions to determine grant-date fair value of stock options granted
Expected term (in years)	5 years 9 months 7 days	6 years	6 years
Expected volatility	72.17%	73.38%	73.75%
Weighted average risk-free interest rate	1.19%	0.65%	2.12%
Expected dividend yield	0.00%	0.00%	0.00%

Stock based awards - Stock opti

Stock based awards - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Options
Balance Outstanding, Beginning of the period (in shares)		3,733,312
Options granted ( in shares)		1,648,855
Options exercised ( in shares)		(140,128)
Options cancelled (in shares)		(20,945)
Balance Outstanding, End of the period (in shares)	3,733,312	5,221,094	3,733,312
Vested and expected to vest ( in shares)		4,610,548
Exercisable ( in shares)		2,115,158
Weighted-Average Exercise Price per Share
Weighted-average exercise price, Beginning of the period (in dollars per share)		$ 12.15
Weighted-average exercise price, Granted (in dollars per share)		22.29
Weighted-average exercise price, Exercised (in dollars per share)		5.36
Weighted-Average Exercise, cancelled (in dollars per share)		23.91
Weighted-average exercise price, End of the period (in dollars per share)	$ 12.15	15.49	$ 12.15
Weighted-average exercise price, Exercisable ( in dollars per share )		14.75
Weighted-average exercise price, Vested and expected to vest at end of the period (in dollars per share)		$ 10.45
Weighted-Average remaining contractual term (years) and Aggregate Intrinsic Value
Weighted-average remaining contractual term outstanding (in years)	8 years 6 months 10 days	8 years 2 months 12 days
Weighted-average remaining contractual term , Options Exercisable(in years)		7 years 11 months 19 days
Weighted-average remaining contractual term vested and expected to vest (in years)		7 years 3 months 14 days
Aggregate Intrinsic Value Balance outstanding	$ 52,498	$ 36,168	$ 52,498
Aggregate Intrinsic Value Exercisable		36,137
Aggregate Intrinsic Value Vested and Expected to vest		$ 24,365
Weighted average grant-date fair value per share of stock options granted		$ 13.98	$ 17.07	$ 8.34

Stock based awards - performanc

Stock based awards - performance based awards (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount
Options granted ( in shares)	1,648,855
Weighted-average exercise price, Granted (in dollars per share)	$ 22.29
Total stock-based compensation expense	$ 10,054	$ 6,022	$ 1,770
Performance Shares [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount
Options granted ( in shares)	610,546
Weighted-average exercise price, Granted (in dollars per share)	$ 21.10

Stock based awards - Stock-base

Stock based awards - Stock-based compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-based compensation
Total stock-based compensation expense	$ 10,054	$ 6,022	$ 1,770
Total unrecognized compensation cost related to unvested stock-based awards	35,954
Proceeds from the early exercise of stock options in exchange for restricted common stock			$ 321
Performance-based awards
Stock-based compensation
Total unrecognized compensation cost related to unvested stock-based awards	7,959
Common Stock
Stock-based compensation
Issuance of restricted common stock upon early exercise of stock options (in shares)			491,207
Research and development expense
Stock-based compensation
Total stock-based compensation expense	3,054	1,633	$ 485
General and administrative expense
Stock-based compensation
Total stock-based compensation expense	$ 7,000	$ 4,389	$ 1,285

Amgen license agreement (Detail

Amgen license agreement (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
Amgen license agreement (Details) - USD ($) $ in Thousands	Aug. 31, 2019	Nov. 30, 2018	Jun. 30, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share Issued value under agreement						$ 95,453
Research and development expense				$ 81,759	$ 64,916	37,046
Amgen Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Initial fair value of the anti-dilution right liability		$ 7,404
Payment for clinical trail	$ 2,500
Obligation for payment in connection with dosing of the first patient	7,500
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
Payment in connection with dosing of the first patient	$ 30,000
Amgen Agreement \| Amgen
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Ownership interest of the outstanding shares (as a percent)			10.00%
Amgen Agreement \| Research and development expense
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense				$ 0	$ 0
Research and development expense upon achievement of clinical milestone						$ 2,500
Amgen Agreement \| Amgen
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront payment			$ 5,000
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

Income taxes - Current income t

Income taxes - Current income tax provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current income tax provision:
Income tax benefit related to operating losses and research and development tax credits	$ 0	$ 0	$ 0
State			24
Total current income tax provision			24
Deferred income tax benefit:
Federal	23,352	(17,580)	(9,400)
State	7,274	(3,135)	688
Total deferred income tax benefit	30,626	(20,715)	(8,712)
Change in deferred tax asset valuation allowance	$ (30,626)	$ 20,715	8,712
Income tax benefits			$ 24

Income taxes - Income tax rate

Income taxes - Income tax rate (Details)	12 Months Ended
Income taxes - Income tax rate (Details)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income taxes
Federal statutory income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefit	7.20%	4.00%	(1.60%)
Research and development tax credits	2.00%	1.30%	1.90%
Other permanent differences	(0.10%)	(0.10%)	0.10%
Change in preferred stock tranche obligation	(30.10%)	(26.20%)	(19.90%)
Effect of Section 382 limitation			(1.50%)

Income taxes - Deferred tax (De

Income taxes - Deferred tax (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax assets
Net operating loss carry forwards	$ 56,128	$ 29,951
Research and development tax credit carry forwards	4,522	2,096
License fees	3,523	3,364
Stock based compensation	3,716	1,402
Accruals, reserves and other	151	63
Total deferred tax assets	68,040	36,876
Valuation allowance	(66,853)	(36,227)	$ (15,512)
Net deferred tax assets	1,187	649
Deferred Tax liabilities
Prepaid expenses	(1,187)	(649)
Total deferred tax liabilities	$ (1,187)	$ (649)

Income taxes - Valuation allowa

Income taxes - Valuation allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income taxes
Valuation allowance as of January 1,	$ (36,227)	$ (15,512)
Decreases recorded as a benefit to income tax provision	(30,626)	(20,715)
Valuation allowance as of December 31,	$ (66,853)	$ (36,227)

Income taxes - Unrecognized tax

Income taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at the beginning	$ 644	$ 237
Increases related to prior year tax positions	66
Increases related to current year tax positions	603	407	$ 237
Balance at the ending	$ 1,313	$ 644	$ 237

Income taxes - Textual (Details

Income taxes - Textual (Details) - USD ($) $ in Thousands	Jun. 29, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Income tax benefits				$ 24
Net operating loss carry forwards		$ 56,128	$ 29,951
Deferred Tax Assets, Tax Credit Carryforwards, Research		4,522	2,096
Increase (Decrease) in Valuation Allowance		(30,626)	20,715	8,712
Accrued interest or penalties related to uncertain tax positions		0
Gross unrecognized tax benefit		1,313	$ 644	$ 237
Amount of state tax that can be offset by NOLs and credits for a three year period	$ 5,000
State taxable income amount that can be reduced by NOLs for a three year period.	$ 1,000
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards		222,397
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		219,953
Deferred Tax Assets, Tax Credit Carryforwards, Research		5,388
NOL carryforwards that expire		2,118
Research and development tax credit derecognized		87
State
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards		137,004
Deferred Tax Assets, Tax Credit Carryforwards, Research		565
NOL carryforwards that expire		3,632
Research and development tax credit derecognized		43
General and administrative expense
Operating Loss Carryforwards [Line Items]
Income tax benefits		$ 24

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (100,777)	$ (79,207)	$ (43,755)
Denominator:
Weighted average common shares outstanding, basic and diluted	34,827,385	31,463,248	15,070,728
Net loss per share, basic and diluted	$ (2.89)	$ (2.52)	$ (2.90)
Net loss per common share, diluted	$ (2.89)	$ (2.52)	$ (2.90)
Number of weighted average restricted common stock	8,127	31,215	49,568

Net loss per share - Anti-Dilut

Net loss per share - Anti-Diluted (Details) - shares	12 Months Ended
Net loss per share - Anti-Diluted (Details) - shares	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares excluded from the calculation of diluted earnings per share, total	5,221,094	3,766,926	3,251,704
Options available for future grant
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares excluded from the calculation of diluted earnings per share, total	5,221,094	3,733,312	3,096,555
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares excluded from the calculation of diluted earnings per share, total		33,614	155,149

Commitments and contingencies_2

Commitments and contingencies (Details) $ in Thousands	May 07, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Jul. 10, 2020ft²	Feb. 29, 2020USD ($)
Initial lease term under the agreement		6 months
Extension lease term under the agreement		6 months
Operating lease liability	$ (173)		$ (182)	$ (138)
Operating lease ROU asset	173
Reduction in future minimum lease payments due to early termination	$ 180
Monthly lease payments under the agreement		$ 4
Lease agreement term						7 years
Square feet of office \| ft²					6,647
Minimum payments during the term						$ 2,300
Non-cancelable purchase commitments with contract research organizations and contract manufacturing organizations			7,420
Total lease liability			1,516
Operating lease liability, noncurrent			$ 1,311	$ 1,516
Accounting Standards Update 2016-13 [Member]
Operating Lease, Liability, Statement of Financial Position [Extensible List]			Operating lease liability, noncurrent, Prepaid Expense and Other Assets, Current
Short-term Liabilities			$ 205

Commitments and contingencies -

Commitments and contingencies - Maturities Of Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2022	$ 312	$ 321
2023	321	80
2024	331
2025	341
2026	351
2027	208
Total future minimum lease payments	1,864	$ 401
Less imputed interest	(348)
Present value of operating lease liabilities	$ 1,516

Commitments and contingencies_3

Commitments and contingencies - Prior to the Company's adoption of ASC 842 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021
Commitments and contingencies
Rent expense	$ 305
Future minimum commitments, 2020	321	$ 312
Future minimum commitments, 2021	80	321
Total	$ 401	$ 1,864

Commitments and contingencies_4

Commitments and contingencies - Components of operating lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating lease expense:
Total operating lease cost	$ 341	$ 342
Other information:
Cash paid for amounts included in the measurement of operating lease liability	$ 303	$ 210
Weighted average remaining lease term, in years	5 years 7 months 6 days	6 years 7 months 6 days
Weighted average discount rate	7.60%	7.60%
General and administrative expense
Operating lease expense:
Operating lease cost	$ 324	$ 267
Variable operating lease cost	$ 17	43
Research and development expense
Operating lease expense:
Short-term lease cost		$ 32

Related parties (Details)

Related parties (Details) - USD ($) $ in Thousands	12 Months Ended
Related parties (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Apple Tree
Related parties
Expenses for services received from related party	$ 0	$ 0	$ 20
Due to related party	0	0	0
Atlas Venture Life Science Advisors, LLC
Related parties
Expenses for services received from related party		22
Due to related party	$ 0	$ 0	$ 0

Subsequent events (Details)

Subsequent events (Details) - $ / shares	1 Months Ended	12 Months Ended
Subsequent events (Details) - $ / shares	Jan. 31, 2022	Dec. 31, 2021
Subsequent event
Stock options granted ( in shares)		1,648,855
Exercise price		$ 22.29
Subsequent event
Subsequent event
Stock options granted ( in shares)	248,376
Exercise price	$ 21.70