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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	May 08, 2020
Document and Entity Information
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Entity Registrant Name	Akero Therapeutics, Inc.
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		28,673,644
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001744659
Amendment Flag	false

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 47,245	$ 64,788
Short-term marketable securities	78,040	71,612
Prepaid expenses and other current assets	933	1,649
Total current assets	126,218	138,049
Right of use asset	226
Other assets	177	69
Total assets	126,621	138,118
Current liabilities:
Accounts payable	1,535	947
Accrued expenses and other current liabilities	6,751	8,422
Total current liabilities	8,286	9,369
Other liabilities	12	23
Total liabilities	8,298	9,392
Commitments and contingencies (Note 11)
Stockholders’ equity:
Common stock, $0.0001 par value, 150,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 28,671,222 and 28,567,837 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	3	3
Additional paid-in capital	260,481	259,049
Accumulated other comprehensive gain (loss)	45	(6)
Accumulated deficit	(142,206)	(130,320)
Total stockholders’ equity	118,323	128,726
Total liabilities and stockholders’ equity	$ 126,621	$ 138,118

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating expenses:
Research and development	$ 8,791	$ 4,063
General and administrative	3,588	1,449
Total operating expenses	12,379	5,512
Loss from operations	(12,379)	(5,512)
Other income (expense):
Interest income	493	166
Other expenses		(16)
Total other income, net	493	150
Net loss	(11,886)	(5,362)
Net unrealizable gain on marketable securities	51
Comprehensive loss	$ (11,835)	$ (5,362)
Net loss per common share, basic and diluted	$ (0.42)	$ (31.90)
Weighted-average number of shares used in computing net loss per common share, basic and diluted	28,499,475	168,071

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Redeemable convertible preferred stock (as converted to common stock)	Common Stock	Additional Paid-In-Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit	Total
Balance at beginning at Dec. 31, 2018	$ 124,728		$ 36,646		$ (86,565)	$ (49,919)
Balance at beginning (in shares) at Dec. 31, 2018	64,730,410	238,986
Stock-based compensation expense			215			215
Net loss					(5,362)	(5,362)
Balance at ending at Mar. 31, 2019	$ 124,728		36,861		(91,927)	(55,066)
Balance at ending (in shares) at Mar. 31, 2019	64,730,410	238,986
Balance at beginning at Dec. 31, 2018	$ 124,728		36,646		(86,565)	(49,919)
Balance at beginning (in shares) at Dec. 31, 2018	64,730,410	238,986
Net loss						(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
Exercise of stock options			112			$ 112
Exercise of stock options (in shares)		103,385				103,385
Vesting of restricted common stock			30			$ 30
Stock-based compensation expense			1,238			1,238
Disgorgment of stockholders' short-swing profits, net			52			52
Net unrealizable gain on marketable securities				51		51
Net loss					(11,886)	(11,886)
Balance at ending at Mar. 31, 2020		$ 3	$ 260,481	$ 45	$ (142,206)	$ 118,323
Balance at ending (in shares) at Mar. 31, 2020		28,671,222

- Definition

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

+ References + Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (11,886)	$ (5,362)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,237	215
Non-cash lease expense	54
Net amortization of premiums and discounts on short-term investments	(103)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	724	197
Accounts payable	588	(564)
Accrued expenses and other current liabilities	(1,931)	70
Net cash used in operating activities	(11,317)	(5,444)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of short-term marketable securities	(24,781)
Proceeds from maturities of short-term marketable securities	18,500
Net cash used in investing activities	(6,281)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the exercise of stock options	112
Proceeds from the disgorgment of stockholders' short-swing profits, net	52
Payment of initial public offering costs		(720)
Net cash provided by (used in) financing activities	164	(720)
Net decrease in cash, cash equivalents and restricted cash	(17,434)	(6,164)
Cash, cash equivalents and restricted cash at the beginning of the period	64,848	76,000
Cash, cash equivalents and restricted cash at the end of the period	47,414	69,836
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Net unrealizable gain on marketable securities	$ 51
Deferred offering costs included in accounts payable and accrued expenses and other current liabilities		$ 556

Nature of the business and basis of presentation	3 Months Ended
Nature of the business and basis of presentation	Mar. 31, 2020
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 biotechnology company developing pioneering medicines designed to restore metabolic balance and improve overall health for patients with nonalcoholic steatohepatitis “NASH”. NASH is a severe form of nonalcoholic fatty liver disease “NAFLD” characterized by inflammation and fibrosis in the liver that can progress to cirrhosis, liver failure, cancer and death. Our lead product candidate is AKR‑001, an analog of fibroblast growth factor 21 (“FGF21”). We are currently conducting a Phase 2a randomized, double-blind, placebo-controlled clinical trial, the BALANCED study, which is evaluating AKR-001 in the treatment of adult NASH patients. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, ability to secure additional capital to fund operations, completion and success of clinical testing, compliance with governmental regulations, development by competitors of new technological innovations, dependence on key personnel and protection of proprietary technology. AKR‑001 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 condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company after elimination of all intercompany accounts and transactions. All adjustments necessary for the fair presentation of the Company’s condensed consolidated financial statements for the periods have been reflected. The Company’s significant accounting policies are disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, dated and filed on March 16, 2020 with the U.S. Securities and Exchange Commission. Since the date of those financial statements, other than the adoption of Accounting Standards Update No. 2016‑02, Leases (Topic 842) as discussed in Note 2, there have been no changes to the Company’s significant accounting policies. Liquidity In accordance with Accounting Standards Update (“ASU”) No. 2014‑15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205‑40), the Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. Since its inception, the Company has funded its operations primarily with proceeds from sales of redeemable convertible preferred stock and most recently with proceeds from its initial public offering (“IPO”) in June 2019. The Company has incurred recurring losses since its inception, including a net loss of $11,886 and $5,362 for the three months ended March 31, 2020 and 2019, respectively and net losses of $43,755 and $81,714 for the years ended December 31, 2019 and 2018, respectively. In addition, as of March 31, 2020, the Company had an accumulated deficit of $142,206. The Company expects to continue to generate operating losses for the foreseeable future. As of May 13, 2020, the issuance date of these condensed consolidated financial statements, the Company expects that its existing cash, cash equivalents and short-term marketable securities of $125,285 as of March 31, 2020, will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of these condensed consolidated financial statements. The Company expects that it will require additional funding beyond this time to complete the clinical development of AKR‑001, to commercialize AKR‑001 if it receives regulatory approval, and to pursue in-licenses or acquisitions of other product candidates. If the Company is unable to obtain funding, the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

Summary of significant accounting policies

3 Months Ended

Mar. 31, 2020

Summary of significant accounting policies

Summary of significant accounting policies

2. Summary of significant accounting policies

Unaudited interim financial statements

The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in accordance with GAAP for interim financial reporting and as required by Regulation S-X, Rule 10‑01. The unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the Company’s financial position as of March 31, 2020 and the results of its operations and its cash flows for the three months ended March 31, 2020 and 2019 and the condensed consolidated statement of stockholders’ equity (deficit) as of March 31, 2020. The financial data and other information disclosed in these notes related to the three months ended March 31, 2020 and 2019 are unaudited. The results for the three months ended March 31, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period.

Use of estimates

The preparation of the Company's condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, 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 estimates.

Cash and cash equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the time of purchase to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts.

Short-term marketable securities

The Company invests in short-term marketable securities, primarily money market funds, commercial paper, U.S. treasury securities and corporate debt securities. The Company classifies its short-term marketable securities as available-for-sale securities and reports them at fair value in short-term marketable securities on the consolidated balance sheets with related unrealized gains and losses included within accumulated other comprehensive gain (loss) on the consolidated balance sheets. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in other income (expense), net on the consolidated statements of operations and comprehensive loss. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income (expense), net. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in other income (expense), net.

The Company regularly reviews all its investments for other-than-temporary declines in estimated fair value. This review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in estimated fair value of an investment is below the amortized cost basis and the decline is other-than-temporary, the carrying value of the security will be reduced and a loss will be recorded for the amount of such decline.

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.

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 842-10-55-2 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. Additionally, a notching method is utilized to apply an upward adjustment to the resulting credit rating to reflect a collateralized borrowing.

Leases (Topic 840) Prior to the Adoption of Topic 842

The Company enters into lease agreements for office facilities which are classified as operating leases. Rent expense is recognized on a straight-line basis over the noncancelable term of the lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability, which is included within accrued expenses and other current liabilities on the condensed consolidated balance sheet.

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 and clinical research organizations ("CROs"), in connection with drug product manufacturing, nonclinical studies and clinical trials, and other related clinical trial fees, such as for investigator grants, patient screening, laboratory work, clinical trial database management, clinical trial material management and statistical compilation and analysis. Non-refundable prepayments for goods or services that will be used or rendered for future research and development activities are recorded as prepaid expenses. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered.

Costs incurred in obtaining technology licenses are charged immediately to research and development expense if the technology licensed has not reached technological feasibility and has no alternative future uses.

Research contract costs and accruals

The Company has entered into various research and development and other agreements with commercial firms, researchers and others for provisions of goods and services. These agreements are generally cancelable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company's estimates.

Stock-based compensation

The Company measures all stock-based awards granted to employees and nonemployees based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company 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 completed its initial public offering 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 restricted common stock award is estimated on the date of grant based on the fair value of the Company's common stock on that same date.

Compensation expense for purchases under the Employee Stock Purchase Plan is recognized based on the fair value of the common stock estimated based on the closing price of our common stock as reported on the date of offering, less the purchase discount percentage provided for in the plan.

The Company classifies stock-based compensation expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient's payroll costs are classified or in which the award recipient's service payments are classified.

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. Our comprehensive loss is comprised of net loss and unrealized gains and losses on our short-term marketable securities.

Emerging growth company

The Company is an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”). Under the JOBS Act, companies have extended transition periods available for complying with new or revised accounting standards. The Company has elected this exemption to delay adopting new or revised accounting standards until such time as those standards apply.

Recently adopted accounting pronouncements

In February 2016 the FASB issued ASU 2016-02, Leases (Topic 842, ASC 842 or ASU 2016-02). ASU 2016-02 amends several aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a ROU asset and corresponding liability, measured at the present value of the lease payments. On January 1, 2020, the Company adopted Topic 842 using the modified retrospective approach and the adoption date as the initial date of application. Results for the three months ended March 31, 2020 are presented under Topic 842. No prior period amounts were adjusted and continue to be reported in accordance with previous lease guidance, Accounting Standards Codification Topic 840, Leases, or Topic 840.

Topic 842 provides a number of optional practical expedients in transition. The Company elected the short-term lease expedient for leases with a term of one year or less, which permits a lessee to not recognize lease assets and lease liabilities for those leases. The Company elected the practical expedients to not reassess its prior conclusions about lease identification under the new standard, to not reassess lease classification, and to not reassess initial direct costs for its existing leases at adoption.

Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected remaining lease term at lease commencement. In transition to ASC 842, the Company utilized the remaining lease term of its leases, as of the effective date, in determining the appropriate incremental borrowing rate. Lease cost for operating leases is recognized on a straight-line basis over the lease term as an operating expense.

The impact of the Company’s adoption of Topic 842 on the accompanying condensed consolidated balance sheet as of January 1, 2020 was as follows:


			Adjustments
			Due to the
	December 31,		Adoption of		January 1,
	2019		Topic 842		2020
Assets:
Operating lease ROU asset	$	—	$	280	$	280
Liabilities:
Operating lease liabilities, current (included in accrued expenses and other current liabilities)		—		224		224
Deferred rent, current (included in accrued expenses and other current liabilities)		2		(2)		—
Operating lease liabilities, noncurrent (included in other liabilities)		—		60		60
Deferred rent, noncurrent (included in other liabilities)		2		(2)		—

The Company adopted Accounting Standards Update No. ASU 2018‑13, Fair Value Measurement (Topic 820)—Disclosure Framework (“ASU 2018‑13”) on January 1, 2020. The adoption of ASU 2018-13 did not have a material impact on the Company’s unaudited condensed consolidated financial statements.

In March 2020, the FASB issued Accounting Standards Update ASU 2020-03, “Codification Improvements to Financial Instruments” (“ASU 2020-03”). ASU 2020-03 improves a variety of codification topics by eliminating inconsistencies and providing clarifications making the codification easier to apply. The conforming amendments are effective upon issuance and did not materially impact the Company’s condensed consolidated financial statements.

Fair value of financial assets and liabilities

3 Months Ended

Mar. 31, 2020

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. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

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

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

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

The following is a summary of our financial assets measured at fair value on a recurring basis as of March 31, 2020 and December 31, 2019:


	Fair Value Measurements as of March 31, 2020 Using:
	Total		Level 1		Level 2		Level 3
Money market funds	$	32,733	$	32,733	$	—	$	—
Commercial paper		46,509		—		46,509		—
U.S. treasury securities		12,141		12,141		—		—
Corporate debt securities		19,390		—		19,390		—
	$	110,773	$	44,874	$	65,899	$	—

	Fair Value Measurements as of December 31, 2019 Using:
	Total		Level 1		Level 2		Level 3
Money market funds	$	49,948	$	49,948	$	—	$	—
Commercial paper		49,114		—		49,114		—
U.S. treasury securities		6,048		6,048		—		—
Corporate debt securities		20,143		—		20,143		—
	$	125,253	$	55,996	$	69,257	$	—

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. The carrying values of the Company’s prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities. During the three months ended March 31, 2020 and 2019, there were no transfers between Level 1, Level 2 and Level 3.

- Definition

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

+ References + Details

Short-term marketable securities

3 Months Ended

Mar. 31, 2020

Short-term marketable securities

Short-term marketable securities

4. Short-term marketable securities

The following is a summary of short-term marketable securities as of March 31, 2020 and December 31, 2019:


	March 31, 2020
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Money market funds	$	32,733	$	—	$	—	$	32,733
Commercial paper		46,509		—		—		46,509
U.S. treasury securities		12,058		83		—		12,141
Corporate debt securities		19,428		—		(38)		19,390
	$	110,728	$	83	$	(38)	$	110,773

Cash and cash equivalents							$	32,733
Short-term marketable securities								78,040
							$	110,773

	December 31, 2019
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Money market funds	$	49,948	$	—	$	—	$	49,948
Commercial paper		49,114		—		—		49,114
U.S. treasury securities		6,048		—		—		6,048
Corporate debt securities		20,149		—		(6)		20,143
	$	125,259	$	—	$	(6)	$	125,253

Cash and cash equivalents							$	53,641
Short-term marketable securities								71,612
							$	125,253

Stockholder's equity (deficit)

3 Months Ended

Mar. 31, 2020

Stockholder’s equity (deficit)

Stockholder’s equity (deficit)

6. Stockholder’s equity (deficit)

Common stock

As of March 31, 2020 and December 31, 2019, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue 150,000,000 shares of $0.0001 par value common stock. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. The holders of common stock, voting exclusively and as a separate class, have the exclusive right to vote for the election of directors of the Company. Common stockholders are entitled to receive dividends, as may be declared by the board of directors. Through March 31, 2020, 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. As of March 31, 2020 and December 31, 2019, there were 28,671,222 and 28,567,837 shares of common stock issued and outstanding, respectively.

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


	March 31, 2020	December 31, 2019
Options outstanding under the 2018 Stock Option and Grant Plan	2,193,592	2,296,029
Options outstanding under the 2019 Stock Option and Incentive Plan	901,858	800,526
Options available for future grant	2,812,364	1,771,931
2019 Employee Stock Purchase Plan	555,042	269,364
	6,462,856	5,137,850

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 March 31, 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. During the vesting period, the Company has the right to repurchase up to all unvested shares at the amount paid if the relationship between the recipient and the Company ceases. Subject to the continued employment or other business relationship with the Company, all of the restricted common stock becomes fully vested within four years of the date of issuance.

In October 2017, 75,467 shares of restricted common stock were subject to repurchase by the Company when one of the founders terminated his relationship with the Company. The Company repurchased the shares in March 2018 for an immaterial amount and immediately reissued the shares to the remaining founders. In connection with the repurchase and reissuance of the shares, the Company amended the restricted stock agreements with the remaining founders such that the restricted common stock is now subject to a vesting schedule over a two-year period commencing in May 2018 and culminating in June 2020.

The Company accounted for the acceleration of vesting under the amended restricted stock agreement as a modification of the original awards and recognized the remaining unvested shares prospectively over the revised vesting period. The grant date fair value of restricted stock vesting during the three months ended March 31, 2020 and 2019 was insignificant.

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.

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	155,149	$	0.52
Shares vesting	(61,617)		0.47
Unvested restricted common stock as of March 31, 2020	93,532	$	0.55

As of March 31, 2020, there were 93,532 shares of unvested restricted common stock consisting of 9,450 shares from unvested restricted common stock awards under restricted stock agreements with the founders and 84,082 shares from the early exercise of stock options.

Stock-based awards

3 Months Ended

Mar. 31, 2020

Stock-based awards

Stock-based awards

7. 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 shall be cumulatively increased on January 1, 2020 and each January 1 thereafter by 4% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s board of directors or compensation committee of the board of directors. The 2019 Plan was increased by 1,142,713 shares on January 1, 2020.

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 outstanding number of shares of the Company’s common stock on the immediately preceding December 31, (ii) 410,803 shares or (iii) such number of shares as determined by the compensation committee. The 2019 ESPP was increased by 285,678 shares on January 1, 2020.

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:


	Three Months Ended
	March 31,
	2020			2019
Expected term (in years)		6.0		6.0
Volatility		80.60	%	67.44	%
Risk-free interest rate		1.63	%	2.57	%
Dividend yield		0	%	0	%

Stock options

The following table summarizes the Company’s stock option activity since December 31, 2019:


		Weighted-		Weighted-
		Average		Average	Aggregate
		Exercise		remaining	Intrinsic
	Number	Price per		contractual	Value
	of Options	Share		term (years)	(000's)
Balance outstanding, December 31, 2019	3,096,555	$	7.89	9.19	$	44,323
Options granted	103,500		20.08
Options exercised	(103,385)		1.09
Options cancelled	(1,220)		0.62
Balance outstanding, March 31, 2020	3,095,450	$	8.53	8.98	$	39,285
Exercisable, March 31, 2020	264,176	$	7.76	8.83	$	3,550
Vested and expected to vest, March 31, 2020	3,095,450	$	8.53	8.98	$	39,285

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

The weighted average grant-date fair value per share of stock options granted during the three months ended March 31, 2020 was $13.91.

Stock-based compensation

The Company recorded $1,237 in stock-based compensation expense for the three months ended March 31, 2020, with $368 classified as research and development expense and $869 classified as general and administrative expense in the condensed consolidated statements of operations and comprehensive loss. The Company recorded $215 in stock-based compensation expense for the three months ended March 31, 2019, with $82 classified as research and development expense and $133 classified as general and administrative expense in the condensed consolidated statements of operations and comprehensive loss.

As of March 31, 2020, total unrecognized compensation cost related to unvested stock options was $15,820, which is expected to be recognized over a weighted average period of 2.9 years.

In April, June and July 2019, certain option holders early exercised options to purchase 491,207 shares of common stock, at an average exercise price of $0.65 per share, for cash proceeds of $321 (See Note 6). Stock-based compensation expense related to these options will continue to be recognized over the requisite service period of the awards based on the grant-date fair value which was determined using the Black-Scholes option-pricing model.

Commitments and contingencies

3 Months Ended

Mar. 31, 2020

Commitments and contingencies

Commitments and contingencies

11. 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 May 2020, 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 three months ended March 31, 2020 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 2020, 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. The First Amendment lease expires in March 2021. Monthly lease payments to be paid under the amended agreement total $19 which are subject to a 3% annual increase beginning in October 2019 and continuing for each successive year until the lease has expired or been terminated. The Company has provided a security deposit of approximately $20, which is included as a component of other assets (non-current) on the Company’s condensed consolidated balance sheets.

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. This early termination will be effective as of June 30, 2020 and reduces the Company’s future minimum lease payments by approximately $180 (see Note 13 – Subsequent Event).

In September 2019 the Company entered into an agreement to use office space in Cambridge, Massachusetts. The agreement was for an initial six-month term, which was extended until September 2020, and provides for rolling six-month extensions. The Company has determined this lease to be short term, as the Company is not obligated at any time for more than a six-month term. The Company makes monthly payments of $4 under the agreement.

For the three months ended March 31, 2020, the components of operating lease cost were as follows:


		Three months ended
		March 31, 2020
Lease cost:	Statement of Operations Classification:
Operating lease cost	General and administrative expense	$	59
Variable operating lease cost	General and administrative expense		27
Short-term lease cost	Research and development expense		8
Total operating lease cost		$	94

Other information:
Cash paid for amounts included in the measurement of operating lease liability		$	59
Weighted average remaining lease term			1 year
Weighted average discount rate			8.0%

The following table presents the maturity of the Company’s operating lease liabilities as of March 31, 2020:


Year ending December 31,
2020 (remainder)	$	178
2021		61
2022		—
2023		—
2024		—
2025 and thereafter		—
Total future minimum lease payments		239
Less imputed interest		(9)
Total operating lease liabilities	$	230

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, which has not yet commenced as the space is not currently available for the Company’s use. Under the agreement, the Company is required to make $2,267 in total minimum payments during the term, which is not included in the maturity table above. The Company anticipates that its occupancy of the space will commence on or about June 2020.

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 contract research organizations and contract manufacturing organizations to provide services in connection with its nonclinical studies and clinical trials and to manufacture clinical development materials. As of March 31, 2020, the Company had non-cancelable purchase commitments under these agreements totaling $7,969.

Indemnification agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not currently aware of any indemnification claims and has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of March 31, 2020.

Legal proceedings

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

Summary of significant accounting policies (Policies)

3 Months Ended

Mar. 31, 2020

Summary of significant accounting policies

Unaudited interim financial statements

Use of estimates

Cash and cash equivalents

Short-term marketable securities

Concentrations of credit risk

Leases

Leases (Topic 842) Effective January 1, 2020

Leases (Topic 840) Prior to the Adoption of Topic 842

Research and development costs

Research contract costs and accruals

Stock-based compensation

Comprehensive loss

Emerging growth company

Recently issued accounting pronouncements not yet adopted

Recently adopted accounting pronouncements

The impact of the Company’s adoption of Topic 842 on the accompanying condensed consolidated balance sheet as of January 1, 2020 was as follows:


			Adjustments
			Due to the
	December 31,		Adoption of		January 1,
	2019		Topic 842		2020
Assets:
Operating lease ROU asset	$	—	$	280	$	280
Liabilities:
Operating lease liabilities, current (included in accrued expenses and other current liabilities)		—		224		224
Deferred rent, current (included in accrued expenses and other current liabilities)		2		(2)		—
Operating lease liabilities, noncurrent (included in other liabilities)		—		60		60
Deferred rent, noncurrent (included in other liabilities)		2		(2)		—

Summary of significant accounting policies (Tables)

3 Months Ended

Mar. 31, 2020

Summary of significant accounting policies

Schedule of impact on the balance sheet upon adoption of lease standard


			Adjustments
			Due to the
	December 31,		Adoption of		January 1,
	2019		Topic 842		2020
Assets:
Operating lease ROU asset	$	—	$	280	$	280
Liabilities:
Operating lease liabilities, current (included in accrued expenses and other current liabilities)		—		224		224
Deferred rent, current (included in accrued expenses and other current liabilities)		2		(2)		—
Operating lease liabilities, noncurrent (included in other liabilities)		—		60		60
Deferred rent, noncurrent (included in other liabilities)		2		(2)		—

Fair value (Tables)

3 Months Ended

Mar. 31, 2020

Fair value of financial assets and liabilities

Summary of assets that are measured at fair value on a recurring basis


	Fair Value Measurements as of March 31, 2020 Using:
	Total		Level 1		Level 2		Level 3
Money market funds	$	32,733	$	32,733	$	—	$	—
Commercial paper		46,509		—		46,509		—
U.S. treasury securities		12,141		12,141		—		—
Corporate debt securities		19,390		—		19,390		—
	$	110,773	$	44,874	$	65,899	$	—

	Fair Value Measurements as of December 31, 2019 Using:
	Total		Level 1		Level 2		Level 3
Money market funds	$	49,948	$	49,948	$	—	$	—
Commercial paper		49,114		—		49,114		—
U.S. treasury securities		6,048		6,048		—		—
Corporate debt securities		20,143		—		20,143		—
	$	125,253	$	55,996	$	69,257	$	—

Short-term marketable securities (Tables)

3 Months Ended

Mar. 31, 2020

Short-term marketable securities

Schedule of short-term marketable securities


	March 31, 2020
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Money market funds	$	32,733	$	—	$	—	$	32,733
Commercial paper		46,509		—		—		46,509
U.S. treasury securities		12,058		83		—		12,141
Corporate debt securities		19,428		—		(38)		19,390
	$	110,728	$	83	$	(38)	$	110,773

Cash and cash equivalents							$	32,733
Short-term marketable securities								78,040
							$	110,773

	December 31, 2019
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Money market funds	$	49,948	$	—	$	—	$	49,948
Commercial paper		49,114		—		—		49,114
U.S. treasury securities		6,048		—		—		6,048
Corporate debt securities		20,149		—		(6)		20,143
	$	125,259	$	—	$	(6)	$	125,253

Cash and cash equivalents							$	53,641
Short-term marketable securities								71,612
							$	125,253

Stock-based awards (Tables)

3 Months Ended

Mar. 31, 2020

Stock-based awards

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


	Three Months Ended
	March 31,
	2020			2019
Expected term (in years)		6.0		6.0
Volatility		80.60	%	67.44	%
Risk-free interest rate		1.63	%	2.57	%
Dividend yield		0	%	0	%

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, 2019	3,096,555	$	7.89	9.19	$	44,323
Options granted	103,500		20.08
Options exercised	(103,385)		1.09
Options cancelled	(1,220)		0.62
Balance outstanding, March 31, 2020	3,095,450	$	8.53	8.98	$	39,285
Exercisable, March 31, 2020	264,176	$	7.76	8.83	$	3,550
Vested and expected to vest, March 31, 2020	3,095,450	$	8.53	8.98	$	39,285

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2020

Commitments and contingencies

Schedule of components of operating lease expense


		Three months ended
		March 31, 2020
Lease cost:	Statement of Operations Classification:
Operating lease cost	General and administrative expense	$	59
Variable operating lease cost	General and administrative expense		27
Short-term lease cost	Research and development expense		8
Total operating lease cost		$	94

Other information:
Cash paid for amounts included in the measurement of operating lease liability		$	59
Weighted average remaining lease term			1 year
Weighted average discount rate			8.0%

Schedule of maturity of the Company’s operating lease liabilities


Year ending December 31,
2020 (remainder)	$	178
2021		61
2022		—
2023		—
2024		—
2025 and thereafter		—
Total future minimum lease payments		239
Less imputed interest		(9)
Total operating lease liabilities	$	230

Short-term marketable securities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 110,728	$ 125,259
Gross unrealized gains	83
Gross unrealized losses	(38)	(6)
Fair value	110,773	125,253
Cash and cash equivalents	32,733	53,641
Short-term marketable securities	78,040	71,612
Total	110,773	125,253
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized cost	32,733	49,948
Fair value	32,733	49,948
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized cost	46,509	49,114
Fair value	46,509	49,114
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost	12,058	6,048
Gross unrealized gains	83
Fair value	12,141	6,048
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost	19,428	20,149
Gross unrealized losses	(38)	(6)
Fair value	$ 19,390	$ 20,143

Stockholder's equity (deficit) - Common stock (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Jun. 24, 2019 USD ($) $ / shares shares	Mar. 31, 2020 Vote $ / shares shares	Dec. 31, 2019 $ / shares shares	Jun. 30, 2019 shares	Jun. 18, 2019 shares
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
Common stock, shares issued		28,671,222	28,567,837
Common stock, shares outstanding		28,671,222	28,567,837
Common stock were reserved for issuance
Options available for future grant		6,462,856	5,137,850
Options to purchase common stock
Common stock were reserved for issuance
Options available for future grant		2,812,364	1,771,931
2018 Stock option and grant plan
Common stock were reserved for issuance
Options available for future grant		2,193,592	2,296,029	107,635	107,635
2019 Stock Option and Incentive plan
Common stock were reserved for issuance
Options available for future grant		901,858	800,526
2019 Employee Stock Purchase Plan
Common stock were reserved for issuance
Options available for future grant		555,042	269,364
IPO
Class of Stock
Common stock, shares issued	6,612,500
Proceeds received, net of underwriting discounts and commissions \| $	$ 98,394
Offering costs \| $	$ 2,942
Number of shares converted	21,056,136
Over allotment
Class of Stock
Public offering price \| $ / shares	$ 16.00
Over allotment \| Maximum
Class of Stock
Common stock, shares issued	862,500

Stock-based awards - Textual (Details) - shares		1 Months Ended
Stock-based awards - Textual (Details) - shares	Jun. 18, 2019	Jun. 30, 2019	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Share-based awards
Number of shares remained available for grant			6,462,856		5,137,850
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	107,635	2,193,592		2,296,029
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				1,142,713
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				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 option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Number of Options
Balance Outstanding, Beginning of the period (in shares)	3,096,555
Options granted ( in shares)	103,500
Options exercised ( in shares)	(103,385)
Options cancelled (in shares)	(1,220)
Balance Outstanding, End of the period (in shares)	3,095,450	3,096,555
Exercisable ( in shares)	264,176
Vested and expected to vest ( in shares)	3,095,450
Weighted-Average Exercise Price per Share
Weighted-average exercise price, Beginning of the period (in dollars per share)	$ 7.89
Weighted-average exercise price, Granted (in dollars per share)	20.08
Weighted-average exercise price, Exercised (in dollars per share)	1.09
Weighted-Average Exercise, cancelled (in dollars per share)	0.62
Weighted-average exercise price, End of the period (in dollars per share)	8.53	$ 7.89
Weighted-average exercise price, Exercisable ( in dollars per share )	7.76
Weighted-average exercise price, Vested and expected to vest at end of the period (in dollars per share)	$ 8.53
Weighted-Average remaining contractual term (years) and Aggregate Intrinsic Value
Weighted-average remaining contractual term outstanding (in years)	8 years 11 months 23 days	9 years 2 months 9 days
Weighted-average remaining contractual term , Options Exercisable(in years)	8 years 9 months 29 days
Weighted-average remaining contractual term vested and expected to vest (in years)	8 years 11 months 23 days
Aggregate Intrinsic Value Balance outstanding	$ 39,285	$ 44,323
Aggregate Intrinsic Value Exercisable	3,550
Aggregate Intrinsic Value Vested and Expected to vest	$ 39,285
Weighted average grant-date fair value per share of stock options granted	$ 13.91

Amgen license agreement (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended
Amgen license agreement (Details) - USD ($) $ in Thousands	Aug. 31, 2019	Nov. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense				$ 8,791	$ 4,063
Amgen
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment for clinical trail	$ 2,500
Amgen Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Initial fair value of the anti-dilution right liability		$ 7,404
Amgen Agreement \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate milestone payments upon the achievement of specified clinical and regulatory milestones	37,500
Aggregate milestone payments upon the achievement of specified commercial milestones	$ 75,000
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]
Initial fair value of the anti-dilution right liability			$ 1,639
Research and development expense				$ 0	$ 0
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

Commitments and contingencies - Components of operating lease expense (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Operating lease expense:
Total operating lease expense	$ 94
Other information:
Cash paid for amounts included in the measurment of operating lease liability	$ 59
Weighted average remaining lease term	1 year
Weighted average discount rate	8.00%
General and administrative expense
Operating lease expense:
Fixed operating lease expense	$ 59
Variable operating lease expense	27
Research and development expense
Operating lease expense:
Short-term lease expense	$ 8

Amgen license agreement	3 Months Ended
Amgen license agreement	Mar. 31, 2020
Amgen license agreement
Amgen license agreement	8. 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 AKR‑001 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. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business. The Company recorded the total consideration transferred to Amgen as research and development expense in the condensed consolidated statements of operations and comprehensive loss because the acquired technology represented in-process research and development and had no alternative future use. In addition, under the Amgen Agreement, Amgen was 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. The Company assessed the Amgen anti-dilution right and determined that the right (i) met the definition of a freestanding financial instrument that was not indexed to the Company’s own stock and (ii) met the definition of a derivative and did not qualify for equity classification. The anti-dilution right liability was initially valued at $1,639 which the Company recorded as research and development expense in June 2018. Changes in the fair value of the anti-dilution right liability continued to be recognized until the Company satisfied the obligation which occurred in November 2018. In November 2018, in connection with the second closing of the Company’s Series A Preferred Stock financing, the Company issued 3,205,128 shares of Series A Preferred Stock to Amgen for a total value of $7,404 satisfying its anti-dilution obligation under the Amgen Agreement. Under the Amgen Agreement, the Company made a milestone payment in August 2019 of $2,500 in connection with dosing the first patient in its Phase 2a clinical trial and is obligated to make aggregate remaining milestone payments to Amgen of up to $37,500 upon the achievement of specified clinical and regulatory milestones and aggregate milestone payments of up to $75,000 upon the achievement of specified commercial milestones for all products licensed under the Amgen Agreement. Under the Amgen Agreement, the Company is obligated to pay Amgen tiered royalties ranging from a low to high single-digit percentages on annual net sales of the licensed products, beginning on the first commercial sale of such licensed products in each country and expiring on a country-by-country basis on the latest of (i) the expiration of the last valid patent claim covering such licensed products in such country, (ii) the loss of regulatory exclusivity in such country, and (iii) ten years after the first commercial sale of such licensed product in such country. The royalty payments are subject to reduction under specified conditions set forth in the Amgen Agreement. The Company is solely responsible for all development, manufacturing, and commercial activities and costs of the licensed products, including clinical studies or other tests necessary to support the use of a licensed product. The Company is also responsible for costs related to the filing, prosecution and maintenance of the licensed patent rights. The Amgen Agreement will remain in effect until the expiration of the royalty term in all countries for all licensed products. The Amgen Agreement may be terminated by either party with at least 90 days' notice in the event of material breach by the other party that remains uncured for 90 days, by either party for insolvency or bankruptcy of the other party and immediately by Amgen if the Company challenges the licensed patents. The Company may also terminate the Amgen Agreement with 90 days' written notice for discretionary reasons such as scientific, technical, regulatory or commercial issues, as defined in the Amgen Agreement. During the three months ended March 31, 2020 and 2019, the Company did not record any research and development expense in connection with the Amgen Agreement.

Income taxes	3 Months Ended
Income taxes	Mar. 31, 2020
Income taxes
Income taxes	9. Income taxes During the three months ended March 31, 2020 and 2019, the Company did not record any income tax benefits for the net operating losses incurred or for the research and development tax credits generated in each period due to its uncertainty of realizing a benefit from those items. All of the Company’s operating losses since inception have been generated in the United States.

Related parties	3 Months Ended
Related parties	Mar. 31, 2020
Related parties
Related parties	12. Related parties Atlas Venture Life Science Advisors, LLC A partner of Atlas Venture Life Science Advisors, LLC (“Atlas”), a significant investor in the Company, has served on the Company’s board of directors since 2018. In August 2018, the Company entered into a use and occupancy agreement for office space with Atlas in Cambridge, Massachusetts (see Note 11). The parties terminated the agreement in September 2019. The Company did not incur any expenses from Atlas during the three months ended March 31, 2020. The Company incurred $5 from Atlas under the use and occupancy agreement during the three months ended March 31, 2019. As of March 31, 2020 and December 31, 2019, the Company did not owe any amounts to Atlas.

Subsequent event	3 Months Ended
Subsequent event	Mar. 31, 2020
Subsequent event
Subsequent event	13. Subsequent event The Company evaluated subsequent events through May 13, 2020, the date on which these financial statements were issued. 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. This early termination will be effective as of June 30, 2020 and will reduce the Company’s future minimum lease payments by approximately $180.

Fair value of financial assets and liabilities - Textual (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
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

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
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	28,671,222	28,567,837
Common stock, shares outstanding	28,671,222	28,567,837

Summary of significant accounting policies - Recently issue accounting Pronouncement (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU asset	$ 226	$ 280
Operating lease liabilities, current (included in accrued expenses and other current liabilities)	$ 230	224
Deferred rent, current (included in accrued expenses and other current liabilities)			$ 2
Operating lease liabilities, noncurrent (included in other liabilities)		60
Deferred rent, noncurrent (included in other liabilities			$ 2
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU asset		280
Operating lease liabilities, current (included in accrued expenses and other current liabilities)		224
Deferred rent, current (included in accrued expenses and other current liabilities)		(2)
Operating lease liabilities, noncurrent (included in other liabilities)		60
Deferred rent, noncurrent (included in other liabilities		$ (2)

Fair value of financial assets and liabilities - Recurring (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 110,773	$ 125,253
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	32,733	49,948
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	46,509	49,114
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	12,141	6,048
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	19,390	20,143
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	44,874	55,996
Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	32,733	49,948
Level 1 \| U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	12,141	6,048
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	65,899	69,257
Level 2 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	46,509	49,114
Level 2 \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 19,390	$ 20,143

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Accrued expenses and other current liabilities
Accrued employee compensation and benefits	$ 740		$ 1,606
Accrued external research and development expenses	4,998		6,361
Accrued legal and professional fees	657		370
Operating lease liability	230	$ 224
Other	126		85
Total accrued expenses and other current liabilities	$ 6,751		$ 8,422

Stockholder's equity (deficit) - Undesignated preferred stock and Restricted common stock (Details) - $ / shares	1 Months Ended
	Oct. 31, 2017	Mar. 31, 2017	Mar. 31, 2020
Restricted stock
Class of Stock
Shares issued (in shares)		226,400
Stock options vesting period	2 years	4 years
Number of shares subject to be repurchased	75,467
Undesignated Preferred Stock
Class of Stock
Preferred stock, par value (in dollars per share)			$ 0.0001
Preferred stock, shares issued			0
Preferred stock, shares outstanding			0
Undesignated Preferred Stock \| Maximum
Class of Stock
Preferred stock, shares authorized			10,000,000

Stockholder's equity (deficit) - Restricted stock activity (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) shares
Number of Shares
Beginning balance of unvested restricted common stock \| shares	155,149
Shares vesting \| shares	(61,617)
Ending balance of unvested restricted common stock \| shares	93,532
Grant-Date Fair Value
Beginning balance of unvested restricted common stock \| $	$ 0.52
Shares vesting \| $	0.47
Ending balance of unvested restricted common stock \| $	$ 0.55

Stockholder's equity (deficit) - Restricted stock activity narrative (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Number of Shares
Unvested restricted common stock	93,532	155,149
Founders
Number of Shares
Unvested restricted common stock	84,082
Restricted stock \| Founders
Number of Shares
Unvested restricted common stock	9,450

Stock-based awards - Stock option valuation (Details)	3 Months Ended
Stock-based awards - Stock option valuation (Details)	Mar. 31, 2020	Mar. 31, 2019
Assumptions to determine grant-date fair value of stock options granted
Expected term (in years)	6 years	6 years
Volatility	80.60%	67.44%
Risk‑free interest rate	1.63%	2.57%
Dividend yield	0.00%	0.00%

Stock based awards - Stock-based compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Apr. 30, 2019	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Total stock based compensation for options granted				$ 1,237	$ 215
Total unrecognized compensation cost related to unvested stock-based awards				$ 15,820
Weighted average period of recognition for unrecognized compensation cost				2 years 10 months 24 days
Common Stock
Stock-based compensation
Issuance of restricted common stock upon early exercise of stock options (in shares)	491,207	491,207	491,207
Exercise price of common stock purchase	$ 0.65	$ 0.65	$ 0.65
Proceeds from the early exercise of stock options in exchange for restricted common stock	$ 321	$ 321	$ 321
Research and development expense
Stock-based compensation
Total stock based compensation for options granted				$ 368	82
General and administrative expense
Stock-based compensation
Total stock based compensation for options granted				$ 869	$ 133

Income taxes - Current income tax provision (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Current income tax provision:
Income tax benefit related to operating losses and research and development tax credits	$ 0	$ 0

Net loss per share - Anti-Diluted (Details) - shares	3 Months Ended
Net loss per share - Anti-Diluted (Details) - shares	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares excluded from the calculation of diluted earnings per share, total	3,188,982	23,436,918
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares excluded from the calculation of diluted earnings per share, total	3,095,450	2,314,740
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	93,532	66,042
Redeemable convertible preferred stock (as converted to common stock)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares excluded from the calculation of diluted earnings per share, total		21,056,136

Commitments and contingencies (Details) $ in Thousands	1 Months Ended
Commitments and contingencies (Details) $ in Thousands	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($) ft²
Commitments and contingencies
Monthly lease payments payable under the amended agreement		$ 19
Increase in rental expense (as a percentage)		3.00%
Security deposit			$ 20
Initial lease term under the agreement	6 months
Extension lease term under the agreement	6 months
Monthly lease payments under the agreement	$ 4
Lease agreement term				7 years
Square feet of office \| ft²				6,647
Minimum payments during the term				$ 2,267
Non-cancelable purchase commitments with contract research organizations and contract manufacturing organizations			$ 7,969

Commitments and contingencies - Operating lease liabilities (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Operating Leases
2020 (remainder)	$ 178
2021	61
Total future minimum lease payments	239
Less imputed interest	(9)
Total operating lease liabilities	$ 230

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

Related parties (Details) $ in Thousands	3 Months Ended
Related parties (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Atlas Venture Life Science Advisors, LLC
Related parties
Related party expense	$ 5

Subsequent event (Details) $ in Thousands	May 07, 2020 USD ($)
Subsequent event
Subsequent event
Reduction in future minimum lease payments due to early termination	$ 180