Kezar Life Sciences (KZR) 10-K 17 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 15, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	KZR
Entity Registrant Name	Kezar Life Sciences, Inc.
Entity Central Index Key	0001645666
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		56,712,716
Entity Public Float			$ 252
Entity Interactive Data Current	Yes
Entity File Number	001-38542
Entity Tax Identification Number	47-3366145
Entity Address, Address Line One	4000 Shoreline Court
Entity Address, Address Line Two	Suite 300
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	822-5600
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Title of 12(b) Security	Common Stock, $0.001 par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the definitive proxy statement for the 2022 Annual Meeting of Stockholders of the registrant, or the Proxy Statement, are incorporated by reference into Part III of this Annual Report on Form 10-K. The Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2021.
Auditor Name	KPMG LLP
Auditor Location	San Francisco, California
Auditor Firm ID	185

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 62,882	$ 21,228
Marketable securities	145,473	119,219
Prepaid expenses	2,570	2,733
Other current assets	729	1,631
Total current assets	211,654	144,811
Property and equipment, net	3,283	3,435
Operating lease right-of-use asset	2,714	3,314
Other assets	282	282
Total assets	217,933	151,842
Current liabilities:
Accounts payable	2,028	2,358
Accrued liabilities	4,985	3,021
Operating lease liabilities, current	1,199	1,042
Other liabilities, current		21
Total current liabilities	8,212	6,442
Operating lease liabilities, noncurrent	3,223	4,422
Debt, noncurrent	9,622
Total liabilities	21,057	10,864
Stockholders' equity:
Common stock, $0.001 par value, 125,000,000 shares authorized as of December 31, 2021 and 2020; 56,259,747 and 46,359,743 shares issued and outstanding as of December 31, 2021 and 2020, respectively	56	46
Preferred stock, $0.001 par value, 10,000,000 shares authorized, zero shares issued and outstanding as of December 31, 2021 and 2020
Additional paid-in capital	377,765	267,093
Accumulated other comprehensive loss	(291)	(137)
Accumulated deficit	(180,654)	(126,024)
Total stockholders' equity	196,876	140,978
Total liabilities and stockholders' equity	$ 217,933	$ 151,842

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	56,259,747	46,359,743
Common stock, shares outstanding	56,259,747	46,359,743
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 38,935	$ 30,981	$ 27,363
General and administrative	15,724	11,969	9,979
Total operating expenses	54,659	42,950	37,342
Loss from operations	(54,659)	(42,950)	(37,342)
Interest income	188	1,208	2,255
Interest expense	(159)
Net loss	$ (54,630)	$ (41,742)	$ (35,087)
Net loss per common share, basic and diluted	$ (1.04)	$ (0.95)	$ (1.84)
Weighted-average shares used to compute net loss per common share, basic and diluted	52,759,335	44,004,190	19,083,826

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (54,630)	$ (41,742)	$ (35,087)
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(50)	82	(45)
Unrealized (loss) gain on marketable securities	(104)	(23)	52
Total other comprehensive (loss) income, net of tax	(154)	59	7
Comprehensive loss	$ (54,784)	$ (41,683)	$ (35,080)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ATM Agreement	Common Stock	Common StockATM Agreement	Additional Paid-in Capital	Additional Paid-in CapitalATM Agreement	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2018	$ 108,797		$ 19		$ 158,176		$ (203)	$ (49,195)
Balance, shares at Dec. 31, 2018			19,114,421
Issuance of common stock under employee stock incentive plans	272				272
Issuance of common stock under employee stock incentive plans, shares			93,656
Vesting related to shares of common stock issued pursuant to early exercises	50				50
Stock-based compensation expense	4,007				4,007
Other comprehensive income	7						7
Net loss	(35,087)							(35,087)
Balance at Dec. 31, 2019	78,046		$ 19		162,505		(196)	(84,282)
Balance, shares at Dec. 31, 2019			19,208,077
Issuance of common stock and pre-funded warrants through underwritten offerings	99,161		$ 27		99,134
Issuance of common stock and pre-funded warrants through underwritten offerings, shares			26,984,001
Issuance of common stock under employee stock incentive plans	470				470
Issuance of common stock under employee stock incentive plans, shares			167,665
Vesting related to shares of common stock issued pursuant to early exercises	41				41
Stock-based compensation expense	4,943				4,943
Other comprehensive income	59						59
Net loss	(41,742)							(41,742)
Balance at Dec. 31, 2020	$ 140,978		$ 46		267,093		(137)	(126,024)
Balance, shares at Dec. 31, 2020			46,359,743
Issuance of common stock net of offering costs		$ 100,995		$ 9		$ 100,986
Issuance of common stock net of offering costs, shares	9,352,359			9,352,359
Issuance of common stock under employee stock incentive plans	$ 2,070		$ 1		2,069
Issuance of common stock under employee stock incentive plans, shares			547,645
Vesting related to shares of common stock issued pursuant to early exercises	21				21
Stock-based compensation expense	7,596				7,596
Other comprehensive income	(154)						(154)
Net loss	(54,630)							(54,630)
Balance at Dec. 31, 2021	$ 196,876		$ 56		$ 377,765		$ (291)	$ (180,654)
Balance, shares at Dec. 31, 2021			56,259,747

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Pre-funded Warrants
Issuance of common stock through underwritten offerings, offering costs		$ 6,748
ATM Agreement
Issuance of common stock through underwritten offerings, offering costs	$ 3,123

Consolidated Statements of Cash

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	$ (54,630)	$ (41,742)	$ (35,087)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,510	1,544	1,301
Stock-based compensation	7,596	4,943	4,007
Amortization of premiums and discounts on marketable securities	1,770	317	(979)
Amortization of debt discount and issuance costs and other non-cash interest	91
Changes in operating assets and liabilities
Prepaid expenses and other current assets	1,051	(1,424)	(553)
Accounts payable and accrued liabilities	1,217	313	2,208
Operating lease liabilities and other liabilities	(1,042)	(900)	(774)
Net cash used in operating activities	(42,437)	(36,949)	(29,877)
Cash flows from investing activities:
Purchases of property and equipment	(316)	(194)	(607)
Purchases of marketable securities	(156,378)	(225,728)	(102,255)
Maturities of marketable securities	128,250	169,424	123,281
Net cash (used in) provided by investing activities	(28,444)	(56,498)	20,419
Cash flows from financing activities:
Proceeds from long-term debt, net of debt discount and issuance costs of $469	9,531
Proceeds from issuance of common stock under at-the-market offerings, net of issuance costs	100,970
Proceeds from sale of common stock and pre-funded warrants in public offerings, net of offering costs		99,186
Proceeds from issuance of common stock under employee stock incentive plans	2,084	456	272
Net cash provided by financing activities	112,585	99,642	272
Effect of exchange rate changes on cash and cash equivalents	(50)	82	(45)
Net increase (decrease) in cash and cash equivalents	41,654	6,277	(9,231)
Cash and cash equivalents at the beginning of period	21,228	14,951	24,182
Cash and cash equivalents at the end of period	62,882	21,228	14,951
Supplemental disclosures of noncash investing and financing information:
Reclassification of employee stock liability to equity upon vesting	21	41	$ 50
Purchase of property and equipment in accounts payable	442
Unpaid offering costs in accrued liabilities		$ 25
Supplemental disclosures
Cash paid for interest	$ 69

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Statement of Cash Flows [Abstract]
Debt discount and issuance costs	$ 469

Organization and Description of

Organization and Description of the Business	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of the Business	1. Organization and Description of the Business Description of Business Kezar Life Sciences, Inc. (the “Company”) was incorporated in Delaware on February 19, 2015, and commenced operations in June 2015. The Company is a clinical-stage biotechnology company, discovering and developing novel small molecule therapeutics to treat unmet needs in immune-mediated diseases and cancer. The Company’s principal operations are in South San Francisco, California, and it operates in one segment. Liquidity Since commencing operations in mid-2015, substantially all of the Company’s efforts have been focused on research, development and the advancement of the Company’s lead product candidates, KZR-616 and KZR-261. The Company’s ultimate success depends on the outcome of the ongoing research and development activities. The Company has not yet generated product sales and as a result has experienced operating losses since inception and had an accumulated deficit of $ 180.7 million as of December 31, 2021. The Company expects to incur additional losses in the future to conduct research and development and will need to raise additional capital to fully implement management’s business plan. The Company intends to raise such capital through the issuance of additional equity and potentially through borrowings, strategic alliances with partner companies and other licensing transactions. However, if such financing is not available at adequate levels, the Company may need to reevaluate its operating plans. Management believes that its cash, cash equivalents and marketable securities as of December 31, 2021 will be sufficient to fund the Company’s cash requirements for at least 12 months following the issuance of these financial statements. During 2021, the Company sold an aggregate of 9,352,359 shares of its common stock at a weighted average purchase price of $ 11.13 per share pursuant to the Company's a t-the-market offering programs for net proceeds of approximately $ 101.0 million after deducting $ 3.1 million commission paid. Between January 1, 2022 and March 15, 2022 , the Company sold an additional 424,043 shares of common stock pursuant to the ATM program for gross proceeds of approximately $ 6.4 million at a weighted average purchase price of $ 15.04 per share. In November 2021, the Company entered into a loan and security agreement (the “Loan Agreement”) with Oxford Finance LLC (“Oxford Finance”), which provides the Company up to $ 50.0 million in borrowing capacity across five potential tranches. The initial tranche of $ 10.0 million was funded at the closing of the Loan Agreement. On June 11, 2020, the Company completed an underwritten public offering of 7,590,909 shares of its common stock and, to certain investors in lieu thereof, pre-funded warrants to purchase 909,091 shares of its common stock at an exercise price of $ 0.001 per share (the “June Offering”). The public offering price of the Company’s common stock was $ 5.50 per share and the public offering price of each pre-funded warrant was $ 5.499 per underlying share. In July 2020, the underwriters exercised an option to purchase an additional 427,707 shares of common stock. The net proceeds from the June Offering were approximately $ 45.8 million, after deducting underwriting discounts and commissions and other offering expenses paid by us. The Company’s existing stockholder, Equal Talent Investments Limited, and one of the Company’s directors purchased an aggregate of approximately $ 8.5 million of common stock in the June Offering. On February 4, 2020, the Company completed an underwritten public offering of 18,965,385 shares of its common stock, which includes the full exercise of the underwriters’ option to purchase additional shares of common stock, and, to certain investors in lieu thereof, pre-funded warrants to purchase 2,884,615 shares of its common stock at an exercise price of $ 0.001 per share (the “February Offering”). The public offering price of the Company’s common stock was $ 2.60 per share and the public offering price of each pre-funded warrant was $ 2.599 per underlying share. The net proceeds from the February Offering were approximately $ 53.4 million, after deducting underwriting discounts and commissions and other offering expenses paid by us. The Company’s existing stockholder, Morningside Ventures Investments Ltd, and certain of the Company’s officers and directors purchased an aggregate of approximately $ 10.4 million of common stock in the February Offering.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the Company’s accounts and those of its wholly owned Australian subsidiary, Kezar Life Sciences Australia Pty Ltd, which is a proprietary company limited by shares. All intercompany balances and transactions have been eliminated upon consolidation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant items subject to such estimates and assumptions include the valuation of marketable securities, stock-based compensation, and accrued research and development costs. Management bases its estimates on historical experience and on various other market-specific relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates. The Company also anticipates that the COVID-19 pandemic will continue to have an impact on the clinical and preclinical development timelines for its clinical and preclinical programs. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s consolidated financial statements. Significant Risks and Uncertainties The Company has implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on its business. The extent to which the COVID-19 pandemic impacts the Company’s business, preclinical and clinical development and regulatory efforts, corporate development objectives and the value of and market for its common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing, safety measures and business closure requirements in the United States, Europe and other countries, and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its strategy, as well as risks and uncertainties common to companies in the biotechnology industry with development operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory feedback regarding the Company’s product candidates; delays or problems in the supply of its product candidates; loss of single source suppliers or their failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional technologies or product candidates; clinical development and the inherent uncertainty of clinical success; the challenges of protecting and enhancing its intellectual property rights; and complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above. Foreign Currency Translation The functional currency of the Company’s non-U.S. subsidiary is the Australian dollar. Asset and liability balances denominated in non-U.S. dollar currency are translated into U.S. dollars using period-end exchange rates, while expenses are based upon the exchange rate at the time of the transaction, if known, or at the average rate for the period. Equity accounts, except for the change in accumulated deficit during the year, have been translated using historical exchange rates. Differences are included in stockholders’ equity as a component of accumulated other comprehensive loss. 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 are stated at fair value. The Company has no restricted cash. Marketable Securities All marketable securities have been classified as “available-for-sale” and are carried at estimated fair value, based upon quoted market prices or pricing models for similar securities. The Company considers its available-for-sale portfolio as available for use in current operations. Unrealized gains and losses are excluded from earnings and are included in other comprehensive income or loss and reported as a separate component of stockholders’ equity or deficit until realized or until a determination is made that an other-than-temporary decline in market value has occurred. Realized gains and losses as well as credit losses, 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. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion, together with interest on securities, are included in interest income on the Company’s consolidated statements of operations. In accordance with the Company’s investment policy, management invests to diversify credit risk and only invests in debt securities with high credit quality, including U.S. government securities. The Company regularly reviews all of its investments for other-than-temporary declines in estimated fair value. Its 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. If a credit loss does exist for available-for-sale debt securities and should be recognized, an allowance will be recorded rather than a write-down of the amortized cost basis. To date, no such credit losses have occurred or have been recorded. Concentration of Credit Risk Financial instruments that potentially expose the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. As of December 31, 2021, the majority of the Company’s cash, cash equivalents and marketable securities were held by financial institutions in the United States, while approximately $ 0.7 million was held by a financial institution in Australia. Such deposits in the United States were in excess of insured limits. Impairment of Long-Lived Assets Long-lived assets include property and equipment. The Company reviews the carrying value of its long-lived assets for possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The Company recognizes an impairment loss when the total estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount. Through December 31, 2021, there have been no such impairment losses. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation on property and equipment is calculated on the straight-line method over the estimated useful lives of the assets. Furniture, laboratory and office equipment are depreciated over five to seven years . Computer equipment are depreciated over three years . Leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term. Other Assets Other assets consist of security deposits for the Company’s operating leases of office and laboratory space. Leases At lease commencement, the Company records a lease liability based on the present value of lease payments over the expected lease term. The Company calculates the present value of lease payments using the discount rate implicit in the lease, unless that rate cannot be readily determined. In that case, the Company uses its incremental borrowing rate, which is the rate of interest that the Company would have to pay to borrow on a collateralized basis an amount equal to the lease payments over the expected lease term. The Company records a corresponding right-of-use (“ROU”) lease asset based on the lease liability, adjusted for any lease incentives received and any initial direct costs paid to the lessor prior to the lease commencement date. After lease commencement, the Company measures its leases as follows: (i) the lease liability based on the present value of the remaining lease payments using the discount rate determined at lease commencement; and (ii) the ROU lease asset based on the remeasured lease liability, adjusted for any unamortized lease incentives received, any unamortized initial direct costs and the cumulative difference between rent expense and amounts paid under the lease agreement. Any lease incentives received and any initial direct costs are amortized on a straight-line basis over the expected lease term. Rent expense is recorded on a straight-line basis over the expected lease term. The Company does not recognize ROU assets or lease liabilities for short-term leases with terms less than 12 months and separately accounts for lease and non-lease components for all of its leases. Debt Issuance Costs and Debt Discounts Debt issuance costs include legal fees, accounting fees, and other direct costs incurred in connection with the execution of the Company’s debt financing. Debt discounts represent costs paid to the lenders. Debt issuance costs and debt discounts are deducted from the carrying amount of the debt liability and are amortized to interest expense over the term of the related debt using the effective interest method. Research and Development Costs Research and development costs are expensed as incurred and consist primarily of salaries and benefits, stock-based compensation expense, lab supplies and facility costs, as well as fees paid to consultants and entities that conduct certain research and development activities on the Company’s behalf and expenses incurred in connection with license agreements. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are capitalized and then expensed as the related goods are delivered or the services are performed. The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies and contract manufacturing activities. The Company estimates the amount of work completed through discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fee to be paid for such services. The Company makes significant judgments and estimates in determining the accrued balance in each reporting period. As actual costs become known, the Company adjusts the accrued estimates. Although the Company does not expect the estimates to be materially different from amounts actually incurred, the status and timing of services performed, the number of patients enrolled and the rate of patient enrollment may vary from the Company’s estimates and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrued expenses are dependent, in part, upon the receipt of timely and accurate reporting from clinical research organizations and other third-party service providers. To date, there have been no material differences from the Company’s accrued expenses to actual expenses. Research and Development Tax Incentive The Company is eligible under the AusIndustry Research and Tax Development Tax Incentive Program to obtain a cash amount from the Australian Taxation Office (ATO). The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply related to research and development expenditures in Australia. These research and development tax incentives are recognized as contra research and development expense when the right to receive has been attained and funds are considered to be collectible. The Company recognized $ 0 , $ 58,000 and $ 635,000 as a reduction of research and development expenses for the years ended December 31, 2021, 2020 and 2019, respectively, in connection with the research and development tax incentive from the ATO. As of December 31, 2021 and 2020, the research and development tax credit receivable was $ 70,000 and $ 766,000 , respectively, which is included in other current assets in the consolidated balance sheets. Stock-Based Compensation Stock-based awards issued to employees, directors and nonemployee consultants, including stock options, are recorded at fair value as of the grant date using the Black-Scholes option pricing model and recognized as expense on a straight-line basis over the expected vesting period. For share-based awards that vest subject to a performance condition, the Company will recognize compensation cost for awards if and when the Company concludes that it is probable that the awards with a performance condition will be achieved on an accelerated attribution method. The Company accounts for forfeitures as they occur by reversing any expense recognized for unvested awards. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company records a valuation allowance against deferred tax assets if it is more likely than not that a portion or all of the asset will not be realized in future periods. In making such determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies and recent financial operations. The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merits, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest charges or penalties related to unrecognized tax benefits. 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 and pre-funded warrants outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is the same as basic net loss per share for the periods presented since the effects of potentially dilutive securities are antidilutive given the net loss of the Company. The pre-funded warrants are included in the computation of basic and diluted net loss per common share as the exercise price is negligible and the pre-funded warrants are fully vested and exercisable. Common share equivalents are only included in the calculation of diluted net loss per common share when their effect is dilutive. Recently Issued Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance . ASU 2021-10 requires entities to disclose certain information about the nature of certain governmental assistance received, including the nature of the transaction and the related accounting policy, the financial statement line items impacted by the assistance, as well as the significant terms and conditions of the transactions. The standard is effective for annual reporting periods beginning after December 15, 2021, with early adoption permitted. The adoption on ASU 2021-10 is not expected to have a material impact on the Company's consolidated financial statements. In May 2021, the FASB issued ASU 2021-04 Earnings Per Share (Topic 260), Debt-Modifications and Extinguishments (Subtopic 370-50), Compensation-Stock Compensation (Topic 718),and Derivatives and Hedging-Contracts in Entity's Own Equity (Subtopic 815-40); Issuer's Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options (a consensus of the FASB Emerging Issues Task Force) , which clarifies and reduces diversity in an issuer's accounting for modifications or exchanges of freestanding equity-classified written call options that remain equity classified after modification or exchange. The standard is effective for all entities for fiscal years beginning after December 15, 2021. Adoption of this standard will not have a material impact on the Company's consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-04 is intended to provide optional expedients and exceptions to the U.S. GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the discontinuation of the London Interbank Offered Rate (“LIBOR”) or by another reference rate expected to be discontinued. The FASB also issued ASU 2021-01, Reference Rate Reform (Topic 848): Scope , in January 2021. It clarifies that certain optional expedients and exceptions apply to derivatives that are affected by the discounting transition. The amendments in this ASU affect the guidance in ASU No. 2020-04 and are effective in the same timeframe as ASU 2020-04. The relief offered by this guidance, if adopted, is available to companies for the period March 12, 2020 through December 31, 2022. The Company's Loan Agreement with Oxford Finance includes a provision for the determination of a benchmark replacement rate as a successor to the LIBOR rate, therefore the Company does not expect the discontinuation of LIBOR to have an impact on its consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash, cash equivalents, marketable securities, other current assets, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are required to be recognized or disclosed at fair value in the financial statements. The Company determines the fair value of Level 1 assets using quoted prices in active markets for identical assets. The Company reviews trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, which are obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. The Company did not have any assets or liabilities measured using Level 3 inputs as of December 31, 2021 or 2020. The following table summarizes the Company’s financial assets measured at fair value on a recurring basis and classified under the appropriate level of the fair value hierarchy as described above (in thousands): December 31, 2021 Financial Assets: Total Level 1 Level 2 Level 3 U.S. Treasury money market funds $ 60,375 $ 60,375 $ — $ — U.S. Treasury securities 82,106 82,106 — — Commercial paper 46,687 — 46,687 — Corporate debt securities 15,481 — 15,481 — U.S. Government agency bonds 1,199 — 1,199 — Total $ 205,848 $ 142,481 $ 63,367 $ — December 31, 2020 Financial Assets: Total Level 1 Level 2 Level 3 U.S. Treasury money market funds $ 19,347 $ 19,347 $ — $ — U.S. Treasury securities 107,708 107,708 — — Commercial paper 1,000 — 1,000 — Corporate debt securities 10,511 — 10,511 — Total $ 138,566 $ 127,055 $ 11,511 $ —

Available-for-Sale Securities

Available-for-Sale Securities	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale Securities	4. Available-for-Sale Securities The following table is a summary of available-for-sale securities recorded in cash and cash equivalents or marketable securities in the Company’s consolidated balance sheets as of December 31, 2021 and 2020 (in thousands): December 31, 2021 Financial Assets: Amortized Unrealized Unrealized Fair U.S. Treasury money market funds $ 60,375 $ — $ — $ 60,375 U.S. Treasury securities 82,204 — ( 98 ) 82,106 Commercial paper 46,678 13 ( 4 ) 46,687 Corporate debt securities 15,486 — ( 5 ) 15,481 U.S. agency bonds 1,200 — ( 1 ) 1,199 Total $ 205,943 $ 13 $ ( 108 ) $ 205,848 December 31, 2020 Financial Assets: Amortized Cost Unrealized Unrealized Fair Value U.S. Treasury money market funds $ 19,347 $ — $ — $ 19,347 U.S. Treasury securities 107,703 10 ( 5 ) 107,708 Commercial paper 998 2 — 1,000 Corporate debt securities 10,509 3 ( 1 ) 10,511 Total $ 138,557 $ 15 $ ( 6 ) $ 138,566 The Company has no t recognized an allowance for credit losses on any securities in an unrealized loss position as of December 31, 2021 and 2020. The following table displays additional information regarding gross unrealized losses and fair value by major security type for available-for-sale securities in an unrealized loss position as of December 31, 2021 and 2020 (in thousands): December 31, 2021 December 31, 2020 Less than 12 consecutive months Less than 12 consecutive months Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities $ 82,106 $ ( 98 ) $ 43,202 $ ( 5 ) Commercial paper 13,734 ( 4 ) — — Corporate debt securities 15,481 ( 5 ) 9,006 ( 1 ) U.S. agency bonds 1,199 ( 1 ) — — Total $ 112,520 $ ( 108 ) $ 52,208 $ ( 6 ) The Company believes that the individual unrealized losses represent temporary declines primarily resulting from interest rate changes, and intends to hold these marketable securities to their maturities. As of December 31, 2021, the amortized cost and estimated fair value of the Company’s available-for-sale securities by contractual maturity are shown below (in thousands): Amortized Estimated Cost Fair Value Available-for-sale securities maturing: In one year or less $ 205,943 $ 205,848 Total available-for-sale securities $ 205,943 $ 205,848 The Company currently does not intend to sell these securities prior to maturity and does not consider these investments to be other-than-temporarily impaired at December 31, 2021. There were no sales of available-for-sale securities in any of the periods presented.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Property and Equipment, Net Property and equipment, net consisted of the following as of December 31, 2021 and 2020 (in thousands): December 31, December 31, Leasehold improvements $ 3,268 $ 3,268 Furniture, laboratory and office equipment 3,423 2,750 Computer equipment 244 159 Total property and equipment 6,935 6,177 Less accumulated depreciation and amortization ( 3,652 ) ( 2,742 ) Property and equipment, net $ 3,283 $ 3,435 Depreciation expense was $ 0.9 million, $ 0.9 million, and $ 0.9 million for the year ended December 31, 2021, 2020, and 2019, respectively. Accrued Liabilities Accrued liabilities consisted of the following as of December 31, 2021 and 2020 (in thousands): December 31, December 31, Accrued preclinical and research costs $ 1,043 $ 461 Accrued clinical costs 1,642 929 Accrued employee-related costs 1,970 1,355 Accrued professional services 231 103 Other 99 173 Total accrued liabilities $ 4,985 $ 3,021

Lease

Lease	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Lease	6. Lease In August 2017, the Company entered into a lease agreement to lease 24,357 square feet of combination laboratory and office space in 4000 Shoreline Court, South San Francisco, California. The lease commenced on March 1, 2018 and terminates on February 28, 2025 . The contractually specified minimum rent and annual rent increases for the operating lease are included in the measurement of the ROU asset and related lease liabilities. Under the lease arrangement, the Company may be required to pay directly, or reimburse the lessor for real estate taxes, insurance, utilities, maintenance and other operating costs. Such amounts are generally variable and therefore not included in the measurement of the ROU asset and related lease liability but are instead recognized as variable lease expense in the Company’s Consolidated Statements of Operations when they are incurred. The operating lease agreement has one option to extend the lease term for a period of five years at the fair market rate at the time of the extension. The option to extend the lease was not recognized as part of the Company’s lease liability and ROU asset as the Company determined the renewal rent costs are uncertain and the option is not reasonably certain to be exercised. As of December 31, 2021, the weighted average remaining lease term was 3.16 years and the weighted average discount rate used to determine the operating lease liability was 10.0 %. Information related to the Company’s ROU asset and related lease liabilities were as follows (in thousands): For the Year Ended December 31, 2021 2020 2019 Cash paid for operating lease liabilities $ 1,042 $ 900 $ 774 Operating lease costs 1,099 1,099 1,099 Variable lease costs 765 542 505 Maturities of lease liabilities as of December 31, 2021 were as follows 2022 $ 1,588 2023 1,635 2024 1,684 2025 282 Total undiscounted lease payments 5,189 Less: imputed interest ( 767 ) Total lease liabilities $ 4,422 Operating lease liabilities, current 1,199 Operating lease liabilities, noncurrent 3,223 Total operating lease liabilities $ 4,422 For the years ended December 31, 2021, 2020 and 2019, the Company recognized $ 1.1 million, $ 1.1 million and $ 1.1 million of rent expense, respectively. Variable lease costs were $ 0.8 million, $ 0.5 million and $ 0.5 million for the years ended December 31, 2021, 2020 and 2019, respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Debt	7. Debt In November 2021, the Company entered into a Loan Agreement with Oxford Finance, which provides the Company up to $ 50.0 million in borrowing capacity across five potential tranches. The initial tranche of $ 10.0 million was funded at the closing of the Loan Agreement, and an additional $ 10.0 million will be available at the Company’s election from July 1, 2022 to December 30, 2022 . Subsequent tranches of $ 20.0 million each would become available upon achieving milestones related to the Company’s MISSION Phase 2 clinical trial, PRESIDIO Phase 2 clinical trial and KZR-261 Phase 1 clinical trial, up to the aggregate maximum amount of $50.0 million. The loan facility is secured by all assets except intellectual property, which has a negative pledge, and will mature on November 1, 2026 . There are no warrants or financial covenants associated with the Loan Agreement. The term loans bear interest at a floating per annum rate (based on the actual number of days elapsed divided by a year of 360 days) equal to the sum of (a) the greater of (i) 30-day U.S. LIBOR rate reported in the Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue and (ii) 0.08 %, plus (b) 7.87 %. The Company is required to make monthly interest-only payments prior to the amortization date of January 1, 2025, subject to a potential one-year extension upon satisfaction of certain conditions. All unpaid principal and accrued and unpaid interest with respect to each term loan is due and payable in full on November 1, 2026 (the “Maturity Date”). The Company has the option to prepay the outstanding balance prior to maturity, subject to a prepayment fee of 1.0 % to 2.0 % depending upon when the prepayment occurs. Upon repayment of the Term Loans, the Company is required to make a final payment fee to the Lenders equal to 6.5 % of the original principal amount of the Term Loans funded which will be accrued by charges to interest expense over the term of the loans using the effective interest method. The Agreement also includes subjective acceleration clauses which permit the lenders to accelerate the Maturity Date under certain circumstances, including, but not limited to, material adverse effects on a Company’s financial status or otherwise. As of December 31, 2021, the Company is in compliance with all covenants in Agreement. Interest expense was $ 0.2 million for the year ended December 31, 2021. The effective interest rate on the term loans, including the amortization of the debt discount and issuance costs, and accretion of the final payment, was 11 %. The components of the long-term debt balance are as follows: December 31, December 31, Principal loan balance $ 10,000 $ — Unamortized debt discount and issuance costs ( 431 ) — Cumulative accretion of final fee 53 — Long-term debt, net $ 9,622 $ — As of December 31, 2021, the estimated future principal payments due were as follows: Years Ending December 31, 2022 $ — 2023 — 2024 — 2025 5,217 2026 4,783 Total $ 10,000

Pre-Funded Warrants

Pre-Funded Warrants	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
Pre-Funded Warrants	8. Pre-Funded Warrants In February 2020, the Company completed the February Offering, which included the issuance and sale of pre-funded warrants to purchase 2,884,615 shares of its common stock. The public offering price of the pre-funded warrants was $ 2.599 per underlying share. In June 2020, the Company completed the June Offering, which included the issuance and sale of pre-funded warrants to purchase 909,091 shares of its common stock. The public offering price of the pre-funded warrants was $ 5.499 per underlying share. Each pre-funded warrant entitles the holder to purchase shares of common stock at an exercise price of $ 0.001 per share and expires 20 years from the date of issuance. These warrants were recorded as a component of stockholders’ equity within additional paid-in capital. Per the terms of the warrant agreement, a holder of the outstanding warrant is not entitled to exercise any portion of the pre-funded warrant if, upon exercise of such portion of the warrant, the holder’s ownership of the Company’s common stock (together with its affiliates) or the combined voting power of the Company’s securities beneficially owned by such holder (together with its affiliates) would exceed 4.99 % after giving effect to the exercise (“Maximum Ownership Percentage”). Upon at least 61 days’ prior notice to the Company by the warrant holder, any warrant holder may increase or decrease the Maximum Ownership Percentage to any other percentage not to exceed 19.99 %. As of December 31, 2021, no shares underlying the pre-funded warrants have been exercised. The following table represents a summary of the pre-funded warrants outstanding as of December 31, 2021. Issue Date Classification Exercise price Expiration Date Number of shares underlying February 4, 2020 Equity $ 0.001 February 4, 2040 2,884,615 June 11, 2020 Equity $ 0.001 June 11, 2040 909,091 Total Outstanding 3,793,706

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation Stock Incentive Plans 2018 Equity Incentive Plan In June 2018, the Company’s board of directors adopted and its stockholders approved the 2018 Equity Incentive Plan (the “2018 Plan”), which became effective as of June 20, 2018, at which point no further grants could be made under the 2015 Equity Incentive Plan (the “2015 Plan”) described below. Under the 2018 Plan, the Company may grant incentive stock options (“ISOs”), nonstatutory stock options (“NSOs”), stock appreciation rights, restricted stock awards, restricted stock units (“RSUs”) and other stock-based awards. As of December 31, 2021, options to purchase 5,327,356 shares of common stock were outstanding under the 2018 Plan and 709,804 shares were available for future issuance under the 2018 Plan. Initially, subject to adjustment as provided in the 2018 Plan, the aggregate number of shares of the Company’s common stock authorized for issuance pursuant to stock awards under the 2018 Plan was 4,000,000 shares, which is the sum of (i) 1,600,692 shares plus (ii) the number of shares reserved and available for issuance under the 2015 Plan at the time the 2018 Plan became effective and (iii) the number of shares subject to stock options or other stock awards granted under the 2015 Plan that expire, terminate, are forfeited or otherwise not issued, or are withheld to satisfy a tax withholding obligation in connection with an award or to satisfy a purchase or exercise price of an award (such as upon the expiration or termination of a stock award prior to vesting). The number of shares of the Company’s common stock reserved for issuance under the 2018 Plan automatically increases on January 1 of each year, beginning on January 1, 2019 and continuing through and including January 1, 2028 , by 5 % of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Company’s board of directors prior to such increase. The maximum number of shares that may be issued upon the exercise of ISOs under the 2018 Plan is 12,500,000 shares. 2015 Equity Incentive Plan The Company’s 2015 Plan provided for the granting of ISOs and NSOs to employees, directors and consultants at the discretion of the board of directors. The 2015 Plan was terminated as to future awards in June 2018, although it continues to govern the terms of options that remain outstanding under the 2015 Plan. No additional stock awards will be granted under the 2015 Plan, and all outstanding stock awards granted under the 2015 Plan that are repurchased, forfeited, expire or are cancelled will become available for grant under the 2018 Plan in accordance with its terms. Options granted under the 2015 Plan expire no later than 10 years from the date of grant. Options granted under the 2015 Plan vest over periods determined by the board of directors, generally over four years . The 2015 Plan allows for early exercise of certain options prior to vesting. Upon termination of employment, the unvested shares are subject to repurchase at the original exercise price. As of December 31, 2021, options to purchase 1,617,828 shares of common stock were outstanding under the 2015 Plan. 2018 Employee Stock Purchase Plan In June 2018, the Company’s board of directors adopted and its stockholders approved the 2018 Employee Stock Purchase Plan (the “ESPP”), which became effective as of June 20, 2018. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the U.S. Internal Revenue Code of 1986, as amended (the “Code”). The number of shares of common stock initially reserved for issuance under the ESPP was 200,000 shares. The ESPP provides for an annual increase on January 1 of each year, beginning on January 1, 2019 and continuing through and including January 1, 2028, equal to the lesser of (i) 1 % of the shares of common stock outstanding on the last day of the prior fiscal year or (ii) 375,000 shares, or a lesser number of shares determined by the Company’s board of directors prior to such increase. As of December 31, 2021, 246,232 shares of common stock had been issued under the ESPP and 711,992 shares remained available for future issuance under the ESPP. The price per share of common stock to be paid by an ESPP participant on the applicable purchase date of an offering period shall be equal to 85 % of the lesser of the fair market value of a share of common stock on (i) the applicable offering date or (ii) the applicable purchase date. The Company’s board of directors authorized an initial six-month offering period beginning on November 16, 2018 and ending on May 15, 2019 . The Company’s board of directors has subsequently authorized additional six-month offering periods, with the most recent offering period beginning on November 16, 2021 . Stock Option Activity The following table summarizes activity under the Company’s stock option plans and related information (in thousands, except share and per share amounts): Number of Weighted Weighted Average Aggregate Outstanding at December 31, 2020 4,489,122 $ 6.14 7.8 $ 7,134 Options granted 3,574,500 $ 5.81 Options exercised ( 439,081 ) $ 3.59 $ 2,107 Options cancelled/forfeited ( 679,357 ) $ 7.97 Outstanding at December 31, 2021 6,945,184 $ 5.95 7.9 $ 77,363 Vested and exercisable at December 31, 2021 3,369,559 $ 5.79 6.8 $ 38,713 The weighted average grant date fair value of options granted during the years ended December 31, 2021 and 2020 was $ 4.20 and $ 2.76 per share, respectively. The aggregate intrinsic value of exercised stock options during the years ended December 31, 2021 and 2020 was $ 2.1 million and $ 0.2 million, respectively. The aggregate intrinsic value is calculated as the difference between the exercise price and the estimated fair value of the Company’s common stock at the date of exercise. Early Exercise Stock Options The 2015 Plan allows for early exercisable option grants, which permit the holder to exercise a stock option for the purchase of common stock before the requisite service is provided (i.e., before the award is vested under its original terms); however, such arrangements permit the Company to subsequently repurchase at the exercise price any shares of common stock for which the applicable vesting conditions have not been satisfied. Under the 2015 Plan, the Company only made such early exercisable option grants to non-employee members of its board of directors. As of December 31, 2021 and 2020, there were 0 and 8,859 shares, respectively, of nonvested common stock outstanding that were exercised early and remain subject to repurchase by the Company at the original issuance price upon termination of the stockholder’s services. The right to repurchase these shares generally lapses with respect to 25 % of the shares underlying the option one year after the applicable vesting commencement date and 1/48 of the shares underlying the option each month for 36 months thereafter. The shares purchased pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest. The cash received in exchange for exercised and nonvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the balance sheets with the corresponding par value in common stock and an offset in additional paid-in capital. As of December 31, 2021 and 2020, the Company recorded in other current liabilities $ 0 and $ 21,000 , respectively, associated with shares issued upon the early exercise of stock options that are subject to repurchase. Stock-Based Compensation Expense Total stock-based compensation expense recognized by function was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 2,955 $ 2,102 $ 1,777 General and administrative 4,641 2,841 2,230 Total stock-based compensation expense $ 7,596 $ 4,943 $ 4,007 As of December 31, 2021, the unrecognized stock-based compensation cost was $ 14.7 million with an estimated weighted average amortization period of 2.6 years. The fair value of the employee stock options granted and the ESPP rights to purchase common stock of the Company is calculated using the Black-Scholes option-pricing model with the following weighted-average assumptions: Options ESPP Rights Year Ended December 31, Year Ended December 31, 2021 2020 2019 2021 2020 2019 Expected term (years) 5.5 - 6.1 5.5 - 6.0 5.8 - 5.9 0.5 0.5 0.5 Expected volatility 85.4 - 88.1 % 83.8 - 91.9 % 78.7 - 83.7 % 64.0 - 77.2 % 101.7 - 114.3 % 73.7 - 109.9 % Risk-free interest rate 0.5 - 1.3 % 0.4 - 1.6 % 1.5 - 2.6 % 0.0 - 0.1 % 0.1 - 0.2 % 1.6 - 2.4 % Expected dividend yield — — — — — — The expected term of options granted represents the period of time that options granted are expected to be outstanding and was determined by calculating the midpoint between the date of vesting and the contractual life of each option. The expected term of the ESPP rights is equal to the six-month look-back period. Volatility is based on the average of the historical volatility of the Company's stock price and that of a peer group of public companies over the expected term. The peer group was selected on the basis of operational and economic similarity with the Company’s principal business operations. The risk-free interest rate for the expected term of the options is based on the U.S. Treasury yield curve with a maturity equal to the expected term in effect at the time of grant. The Company has no t paid, and does not anticipate paying, cash dividends on its shares of common stock; therefore, the expected dividend yield is zero .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments & Contingencies Indemnification In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by California corporate law. The Company currently has directors’ and officers’ insurance.

License Agreement

License Agreement	12 Months Ended
	Dec. 31, 2021
License Agreement [Abstract]
License Agreement	11. License Agreement In June 2015, the Company entered into an exclusive license agreement with Onyx Therapeutics, Inc. (“Onyx”), a wholly owned subsidiary of Amgen, Inc., for a worldwide, exclusive license under certain patents, and a non-exclusive license to certain know-how, in each case controlled by Onyx and relating to the Company’s immunoproteasome program. The Company may be required to make future payments of up to $ 172.5 million upon achievement of certain development and commercial milestones for KZR-616, as well as royalty payments in the mid to high single digits on future annual net sales, if any.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Defined Contribution Plan	12. Defined Contribution Plan The Company has a qualified 401(k) Savings and Investment Plan (the “Plan”) whereby employees may contribute up to the lesser of $ 56,000 or 100 % of their pre-tax compensation. The total contributed amount from the employees is only up to Federal annual limits. The Company matches $ 1.00 for every $ 1.00 contributed to the Plan by participants up to the first 4 % of base compensation and incentive cash bonus (subject to statutory limits). During the years ended December 31, 2021, 2020 and 2019, the Company recorded matching contributions of approximately $ 423,000 , $ 326,000 and $ 249,000 , respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes No provision for income taxes was recorded for the years ended December 31, 2021, 2020 and 2019. The U.S. federal deferred tax assets generated from the Company’s net operating losses have been fully reserved, as the Company believes it is not more likely than not that the benefit will be realized. The following table presents domestic and foreign components of net loss for the periods presented (in thousands): Year Ended December 31, 2021 2020 2019 Domestic $ ( 54,581 ) $ ( 41,599 ) $ ( 34,181 ) Foreign ( 49 ) ( 143 ) ( 906 ) Total $ ( 54,630 ) $ ( 41,742 ) $ ( 35,087 ) In December 2015, the Protecting Americans from Tax Hikes Act of 2015 (“PATH”) was signed into law, which created several new research and development (“R&D”) tax credit provisions, including allowing qualified small businesses to utilize the R&D credit against the employer’s portion of payroll tax up to a maximum of $ 250,000 per year. The Company qualified as a small business under PATH for years 2016 through 2020. The Company has utilized $ 325,000 , $ 373,000 and $ 284,000 of R&D tax credits as a reduction of payroll expenses to offset its payroll tax liabilities for the years ended December 31, 2021, 2020 and 2019, respectively. The effective tax rate of the provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2021 2020 2019 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 1.3 1.1 0.9 Foreign tax rate differential 0.0 0.0 0.2 Permanent differences ( 2.2 ) ( 2.7 ) ( 1.7 ) Research and development credit 4.0 2.6 1.9 Change in valuation allowance ( 24.1 ) ( 22.0 ) ( 22.3 ) Provision for income taxes — % — % — % The components of the deferred tax assets and liabilities are as follows (in thousands): Year Ended December 31, 2021 2020 2019 Deferred tax assets Reserves and accruals $ 2,043 $ 1,665 $ 1,056 Net operating loss carryforwards 34,617 24,824 16,986 Research and development credit carryforwards 5,127 2,938 2,177 Lease Liabilities 929 1,148 1,336 Gross deferred tax assets 42,716 30,575 21,555 Valuation allowance ( 41,771 ) ( 29,410 ) ( 20,196 ) Net deferred tax assets 945 1,165 1,359 Deferred tax liabilities Property and equipment ( 375 ) ( 469 ) ( 557 ) Right-of-use asset ( 570 ) ( 696 ) ( 802 ) Net deferred tax assets $ — $ — $ — Realization of the deferred tax assets is dependent upon future taxable income. Since the amount and timing of future income are uncertain, the net deferred tax assets, as of December 31, 2021, and December 31, 2020 have been fully offset by a valuation allowance. The valuation allowance increased approximately $ 12.4 million, $ 9.2 million and $ 7.6 million during the years ended December 31, 2021, 2020, and 2019, respectively. As of December 31, 2021, the Company had federal net operating loss (“NOL”) carryforward of $ 156.4 million and a federal research and development tax credit carryforward of $ 4.6 million. If not utilized sooner, the federal NOL generated through December 31, 2017 and tax credit carryforwards will expire, beginning in 2035 . Federal net operating loss carryforwards of $ 134.4 million generated from years ended after December 31, 2017, carryforward indefinitely. As of December 31, 2021 the Company had a state NOL carryforward of $ 17.3 million, which will expire beginning in 2035 , and a state research and development tax credit carryforward of $ 2.6 million, which does not expire. As of December 31, 2021, the Company also had accumulated Australian tax losses of $ 0.6 million available for carry forward against future earnings, which under relevant tax laws do not expire but may not be available under certain circumstances. In general, if the Company experiences a greater than 50 percentage point aggregate change in ownership over a three-year period (a Section 382 ownership change), utilization of the Company’s pre-change NOL carryforwards is subject to an annual limitation under Section 382 of the Code and similar California laws. The annual limitation generally is determined by multiplying the value of the Company’s stock at the time of such ownership change (subject to certain adjustments) by the applicable long-term tax-exempt rate. Such limitations may result in expiration of a portion of the NOL carryforwards before utilization. The Company has not utilized any NOL carryforwards through December 31, 2021. In addition, the Company’s deferred tax assets are subject to a full valuation allowance, and thus no benefit for deferred tax assets is recorded on the Company’s books. The Company’s ability to use the remaining NOL carryforwards may be further limited if the Company experiences a Section 382 ownership change as a result of future changes in the Company’s stock ownership. The Company had $ 1.6 million of unrecognized tax benefits as of December 31, 2021. No liability related to uncertain tax positions is recorded on the financial statements. All uncertain tax positions are currently recorded as a reduction to the Company’s deferred tax assets, which are subject to a valuation allowance. If recognized, none of the unrecognized tax benefits would affect the effective tax rate. The Company does not anticipate that the total amounts of unrecognized tax benefits will significantly increase or decrease in the next 12 months. The Company’s policy is to include interest and penalties related to unrecognized tax benefits within the provision for income taxes, as necessary. The Company did no t recognize any accrued interest and penalties related to gross unrecognized tax benefits related to the year ended December 31, 2021. A reconciliation of the Company’s unrecognized tax benefits for the year ended December 31, 2021 and 2020 is as follows (in thousands): Year Ended December 31, 2021 2020 Balance at the beginning of the year $ 868 $ — Increase related to prior year tax positions — 381 Increase related to current year tax positions 775 487 Balance at the end of the year $ 1,643 $ 868 The Company files income tax returns in the United States federal jurisdiction, state jurisdictions and Australia. The Company currently has no federal, state or other jurisdictional tax examinations in progress. All years are open for examination by federal, state and Australian authorities.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	14. Net Loss Per Share Net Loss Per Share The following table sets forth the calculation of basic and diluted net loss per share during the periods presented (in thousands, except share and per share data): Year Ended December 31, 2021 2020 2019 Numerator: Net loss $ ( 54,630 ) $ ( 41,742 ) $ ( 35,087 ) Denominator: Weighted-average shares of common stock outstanding 52,759,335 44,004,190 19,083,826 Net loss per share, basic and diluted $ ( 1.04 ) $ ( 0.95 ) $ ( 1.84 ) The following outstanding shares of common stock equivalents were excluded from the computation of the diluted net loss per share for the periods presented because their effect would have been anti-dilutive: Year Ended December 31, 2021 2020 2019 Options to purchase common stock 6,945,184 4,489,122 3,107,066 Common stock subject to future vesting — 8,859 30,027 Total 6,945,184 4,497,981 3,137,093

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of presentation and consolidation	Basis of Presentation and Consolidation The consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the Company’s accounts and those of its wholly owned Australian subsidiary, Kezar Life Sciences Australia Pty Ltd, which is a proprietary company limited by shares. All intercompany balances and transactions have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant items subject to such estimates and assumptions include the valuation of marketable securities, stock-based compensation, and accrued research and development costs. Management bases its estimates on historical experience and on various other market-specific relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates. The Company also anticipates that the COVID-19 pandemic will continue to have an impact on the clinical and preclinical development timelines for its clinical and preclinical programs. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s consolidated financial statements.
Significant Risks and Uncertainties	Significant Risks and Uncertainties The Company has implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on its business. The extent to which the COVID-19 pandemic impacts the Company’s business, preclinical and clinical development and regulatory efforts, corporate development objectives and the value of and market for its common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing, safety measures and business closure requirements in the United States, Europe and other countries, and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its strategy, as well as risks and uncertainties common to companies in the biotechnology industry with development operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory feedback regarding the Company’s product candidates; delays or problems in the supply of its product candidates; loss of single source suppliers or their failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional technologies or product candidates; clinical development and the inherent uncertainty of clinical success; the challenges of protecting and enhancing its intellectual property rights; and complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above.
Foreign Currency Translation	Foreign Currency Translation The functional currency of the Company’s non-U.S. subsidiary is the Australian dollar. Asset and liability balances denominated in non-U.S. dollar currency are translated into U.S. dollars using period-end exchange rates, while expenses are based upon the exchange rate at the time of the transaction, if known, or at the average rate for the period. Equity accounts, except for the change in accumulated deficit during the year, have been translated using historical exchange rates. Differences are included in stockholders’ equity as a component of accumulated other comprehensive loss.
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 are stated at fair value. The Company has no restricted cash.
Marketable Securities	Marketable Securities All marketable securities have been classified as “available-for-sale” and are carried at estimated fair value, based upon quoted market prices or pricing models for similar securities. The Company considers its available-for-sale portfolio as available for use in current operations. Unrealized gains and losses are excluded from earnings and are included in other comprehensive income or loss and reported as a separate component of stockholders’ equity or deficit until realized or until a determination is made that an other-than-temporary decline in market value has occurred. Realized gains and losses as well as credit losses, 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. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion, together with interest on securities, are included in interest income on the Company’s consolidated statements of operations. In accordance with the Company’s investment policy, management invests to diversify credit risk and only invests in debt securities with high credit quality, including U.S. government securities. The Company regularly reviews all of its investments for other-than-temporary declines in estimated fair value. Its 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. If a credit loss does exist for available-for-sale debt securities and should be recognized, an allowance will be recorded rather than a write-down of the amortized cost basis. To date, no such credit losses have occurred or have been recorded.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially expose the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. As of December 31, 2021, the majority of the Company’s cash, cash equivalents and marketable securities were held by financial institutions in the United States, while approximately $ 0.7 million was held by a financial institution in Australia. Such deposits in the United States were in excess of insured limits.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets include property and equipment. The Company reviews the carrying value of its long-lived assets for possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The Company recognizes an impairment loss when the total estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount. Through December 31, 2021, there have been no such impairment losses.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation on property and equipment is calculated on the straight-line method over the estimated useful lives of the assets. Furniture, laboratory and office equipment are depreciated over five to seven years . Computer equipment are depreciated over three years . Leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term.
Other Assets	Other Assets Other assets consist of security deposits for the Company’s operating leases of office and laboratory space.
Leases	Leases At lease commencement, the Company records a lease liability based on the present value of lease payments over the expected lease term. The Company calculates the present value of lease payments using the discount rate implicit in the lease, unless that rate cannot be readily determined. In that case, the Company uses its incremental borrowing rate, which is the rate of interest that the Company would have to pay to borrow on a collateralized basis an amount equal to the lease payments over the expected lease term. The Company records a corresponding right-of-use (“ROU”) lease asset based on the lease liability, adjusted for any lease incentives received and any initial direct costs paid to the lessor prior to the lease commencement date. After lease commencement, the Company measures its leases as follows: (i) the lease liability based on the present value of the remaining lease payments using the discount rate determined at lease commencement; and (ii) the ROU lease asset based on the remeasured lease liability, adjusted for any unamortized lease incentives received, any unamortized initial direct costs and the cumulative difference between rent expense and amounts paid under the lease agreement. Any lease incentives received and any initial direct costs are amortized on a straight-line basis over the expected lease term. Rent expense is recorded on a straight-line basis over the expected lease term. The Company does not recognize ROU assets or lease liabilities for short-term leases with terms less than 12 months and separately accounts for lease and non-lease components for all of its leases.
Debt Issuance Costs and Debt Discounts	Debt Issuance Costs and Debt Discounts Debt issuance costs include legal fees, accounting fees, and other direct costs incurred in connection with the execution of the Company’s debt financing. Debt discounts represent costs paid to the lenders. Debt issuance costs and debt discounts are deducted from the carrying amount of the debt liability and are amortized to interest expense over the term of the related debt using the effective interest method.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred and consist primarily of salaries and benefits, stock-based compensation expense, lab supplies and facility costs, as well as fees paid to consultants and entities that conduct certain research and development activities on the Company’s behalf and expenses incurred in connection with license agreements. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are capitalized and then expensed as the related goods are delivered or the services are performed. The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies and contract manufacturing activities. The Company estimates the amount of work completed through discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fee to be paid for such services. The Company makes significant judgments and estimates in determining the accrued balance in each reporting period. As actual costs become known, the Company adjusts the accrued estimates. Although the Company does not expect the estimates to be materially different from amounts actually incurred, the status and timing of services performed, the number of patients enrolled and the rate of patient enrollment may vary from the Company’s estimates and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrued expenses are dependent, in part, upon the receipt of timely and accurate reporting from clinical research organizations and other third-party service providers. To date, there have been no material differences from the Company’s accrued expenses to actual expenses.
Research and Development Tax Incentive	Research and Development Tax Incentive The Company is eligible under the AusIndustry Research and Tax Development Tax Incentive Program to obtain a cash amount from the Australian Taxation Office (ATO). The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply related to research and development expenditures in Australia. These research and development tax incentives are recognized as contra research and development expense when the right to receive has been attained and funds are considered to be collectible. The Company recognized $ 0 , $ 58,000 and $ 635,000 as a reduction of research and development expenses for the years ended December 31, 2021, 2020 and 2019, respectively, in connection with the research and development tax incentive from the ATO. As of December 31, 2021 and 2020, the research and development tax credit receivable was $ 70,000 and $ 766,000 , respectively, which is included in other current assets in the consolidated balance sheets.
Stock-Based Compensation	Stock-Based Compensation Stock-based awards issued to employees, directors and nonemployee consultants, including stock options, are recorded at fair value as of the grant date using the Black-Scholes option pricing model and recognized as expense on a straight-line basis over the expected vesting period. For share-based awards that vest subject to a performance condition, the Company will recognize compensation cost for awards if and when the Company concludes that it is probable that the awards with a performance condition will be achieved on an accelerated attribution method. The Company accounts for forfeitures as they occur by reversing any expense recognized for unvested awards.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company records a valuation allowance against deferred tax assets if it is more likely than not that a portion or all of the asset will not be realized in future periods. In making such determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies and recent financial operations. The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merits, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest charges or penalties related to unrecognized tax benefits.
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 and pre-funded warrants outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is the same as basic net loss per share for the periods presented since the effects of potentially dilutive securities are antidilutive given the net loss of the Company. The pre-funded warrants are included in the computation of basic and diluted net loss per common share as the exercise price is negligible and the pre-funded warrants are fully vested and exercisable. Common share equivalents are only included in the calculation of diluted net loss per common share when their effect is dilutive.
Recently Issued Accounting Pronouncements to be Adopted	Recently Issued Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance . ASU 2021-10 requires entities to disclose certain information about the nature of certain governmental assistance received, including the nature of the transaction and the related accounting policy, the financial statement line items impacted by the assistance, as well as the significant terms and conditions of the transactions. The standard is effective for annual reporting periods beginning after December 15, 2021, with early adoption permitted. The adoption on ASU 2021-10 is not expected to have a material impact on the Company's consolidated financial statements. In May 2021, the FASB issued ASU 2021-04 Earnings Per Share (Topic 260), Debt-Modifications and Extinguishments (Subtopic 370-50), Compensation-Stock Compensation (Topic 718),and Derivatives and Hedging-Contracts in Entity's Own Equity (Subtopic 815-40); Issuer's Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options (a consensus of the FASB Emerging Issues Task Force) , which clarifies and reduces diversity in an issuer's accounting for modifications or exchanges of freestanding equity-classified written call options that remain equity classified after modification or exchange. The standard is effective for all entities for fiscal years beginning after December 15, 2021. Adoption of this standard will not have a material impact on the Company's consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-04 is intended to provide optional expedients and exceptions to the U.S. GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the discontinuation of the London Interbank Offered Rate (“LIBOR”) or by another reference rate expected to be discontinued. The FASB also issued ASU 2021-01, Reference Rate Reform (Topic 848): Scope , in January 2021. It clarifies that certain optional expedients and exceptions apply to derivatives that are affected by the discounting transition. The amendments in this ASU affect the guidance in ASU No. 2020-04 and are effective in the same timeframe as ASU 2020-04. The relief offered by this guidance, if adopted, is available to companies for the period March 12, 2020 through December 31, 2022. The Company's Loan Agreement with Oxford Finance includes a provision for the determination of a benchmark replacement rate as a successor to the LIBOR rate, therefore the Company does not expect the discontinuation of LIBOR to have an impact on its consolidated financial statements.
Fair Value Measurements	Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash, cash equivalents, marketable securities, other current assets, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are required to be recognized or disclosed at fair value in the financial statements. The Company determines the fair value of Level 1 assets using quoted prices in active markets for identical assets. The Company reviews trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, which are obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on a Recurring Basis	The following table summarizes the Company’s financial assets measured at fair value on a recurring basis and classified under the appropriate level of the fair value hierarchy as described above (in thousands): December 31, 2021 Financial Assets: Total Level 1 Level 2 Level 3 U.S. Treasury money market funds $ 60,375 $ 60,375 $ — $ — U.S. Treasury securities 82,106 82,106 — — Commercial paper 46,687 — 46,687 — Corporate debt securities 15,481 — 15,481 — U.S. Government agency bonds 1,199 — 1,199 — Total $ 205,848 $ 142,481 $ 63,367 $ — December 31, 2020 Financial Assets: Total Level 1 Level 2 Level 3 U.S. Treasury money market funds $ 19,347 $ 19,347 $ — $ — U.S. Treasury securities 107,708 107,708 — — Commercial paper 1,000 — 1,000 — Corporate debt securities 10,511 — 10,511 — Total $ 138,566 $ 127,055 $ 11,511 $ —

Available-for-Sale Securities (

Available-for-Sale Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Summary of Available-For-Sale Securities Recorded in Cash and Cash Equivalents or Marketable Securities	The following table is a summary of available-for-sale securities recorded in cash and cash equivalents or marketable securities in the Company’s consolidated balance sheets as of December 31, 2021 and 2020 (in thousands): December 31, 2021 Financial Assets: Amortized Unrealized Unrealized Fair U.S. Treasury money market funds $ 60,375 $ — $ — $ 60,375 U.S. Treasury securities 82,204 — ( 98 ) 82,106 Commercial paper 46,678 13 ( 4 ) 46,687 Corporate debt securities 15,486 — ( 5 ) 15,481 U.S. agency bonds 1,200 — ( 1 ) 1,199 Total $ 205,943 $ 13 $ ( 108 ) $ 205,848 December 31, 2020 Financial Assets: Amortized Cost Unrealized Unrealized Fair Value U.S. Treasury money market funds $ 19,347 $ — $ — $ 19,347 U.S. Treasury securities 107,703 10 ( 5 ) 107,708 Commercial paper 998 2 — 1,000 Corporate debt securities 10,509 3 ( 1 ) 10,511 Total $ 138,557 $ 15 $ ( 6 ) $ 138,566
Summary of Gross Unrealized Losses and Fair Value by Major Security Type for Available-For-Sale Securities in Unrealized Loss Position	The following table displays additional information regarding gross unrealized losses and fair value by major security type for available-for-sale securities in an unrealized loss position as of December 31, 2021 and 2020 (in thousands): December 31, 2021 December 31, 2020 Less than 12 consecutive months Less than 12 consecutive months Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities $ 82,106 $ ( 98 ) $ 43,202 $ ( 5 ) Commercial paper 13,734 ( 4 ) — — Corporate debt securities 15,481 ( 5 ) 9,006 ( 1 ) U.S. agency bonds 1,199 ( 1 ) — — Total $ 112,520 $ ( 108 ) $ 52,208 $ ( 6 )
Summary of Amortized Cost and Estimated Fair Value of Available-for-sale Securities by Contractual Maturity	As of December 31, 2021, the amortized cost and estimated fair value of the Company’s available-for-sale securities by contractual maturity are shown below (in thousands): Amortized Estimated Cost Fair Value Available-for-sale securities maturing: In one year or less $ 205,943 $ 205,848 Total available-for-sale securities $ 205,943 $ 205,848

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Property and Equipment, Net	Property and equipment, net consisted of the following as of December 31, 2021 and 2020 (in thousands): December 31, December 31, Leasehold improvements $ 3,268 $ 3,268 Furniture, laboratory and office equipment 3,423 2,750 Computer equipment 244 159 Total property and equipment 6,935 6,177 Less accumulated depreciation and amortization ( 3,652 ) ( 2,742 ) Property and equipment, net $ 3,283 $ 3,435
Accrued Liabilities	Accrued liabilities consisted of the following as of December 31, 2021 and 2020 (in thousands): December 31, December 31, Accrued preclinical and research costs $ 1,043 $ 461 Accrued clinical costs 1,642 929 Accrued employee-related costs 1,970 1,355 Accrued professional services 231 103 Other 99 173 Total accrued liabilities $ 4,985 $ 3,021

Lease (Tables)

Lease (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Details of Right-of-Use Assets and Lease Liabilities	Information related to the Company’s ROU asset and related lease liabilities were as follows (in thousands): For the Year Ended December 31, 2021 2020 2019 Cash paid for operating lease liabilities $ 1,042 $ 900 $ 774 Operating lease costs 1,099 1,099 1,099 Variable lease costs 765 542 505 Maturities of lease liabilities as of December 31, 2021 were as follows 2022 $ 1,588 2023 1,635 2024 1,684 2025 282 Total undiscounted lease payments 5,189 Less: imputed interest ( 767 ) Total lease liabilities $ 4,422 Operating lease liabilities, current 1,199 Operating lease liabilities, noncurrent 3,223 Total operating lease liabilities $ 4,422

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule of Long-term Debt Balance	The components of the long-term debt balance are as follows: December 31, December 31, Principal loan balance $ 10,000 $ — Unamortized debt discount and issuance costs ( 431 ) — Cumulative accretion of final fee 53 — Long-term debt, net $ 9,622 $ —
Schedule of Estimated Future Principal Payments	As of December 31, 2021, the estimated future principal payments due were as follows: Years Ending December 31, 2022 $ — 2023 — 2024 — 2025 5,217 2026 4,783 Total $ 10,000

Pre-Funded Warrants (Tables)

Pre-Funded Warrants (Tables)	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
Summary of Pre-Funded Warrants Outstanding	The following table represents a summary of the pre-funded warrants outstanding as of December 31, 2021. Issue Date Classification Exercise price Expiration Date Number of shares underlying February 4, 2020 Equity $ 0.001 February 4, 2040 2,884,615 June 11, 2020 Equity $ 0.001 June 11, 2040 909,091 Total Outstanding 3,793,706

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Activity under Stock Option Plans and Related Information	The following table summarizes activity under the Company’s stock option plans and related information (in thousands, except share and per share amounts): Number of Weighted Weighted Average Aggregate Outstanding at December 31, 2020 4,489,122 $ 6.14 7.8 $ 7,134 Options granted 3,574,500 $ 5.81 Options exercised ( 439,081 ) $ 3.59 $ 2,107 Options cancelled/forfeited ( 679,357 ) $ 7.97 Outstanding at December 31, 2021 6,945,184 $ 5.95 7.9 $ 77,363 Vested and exercisable at December 31, 2021 3,369,559 $ 5.79 6.8 $ 38,713
Stock-Based Compensation Expense Recognized	Total stock-based compensation expense recognized by function was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 2,955 $ 2,102 $ 1,777 General and administrative 4,641 2,841 2,230 Total stock-based compensation expense $ 7,596 $ 4,943 $ 4,007
Fair Value of Employee Stock Options Granted and ESPP Rights to Purchase Common Stock Calculated Using Black Scholes Option Pricing Model with Weighted Average Assumptions	The fair value of the employee stock options granted and the ESPP rights to purchase common stock of the Company is calculated using the Black-Scholes option-pricing model with the following weighted-average assumptions: Options ESPP Rights Year Ended December 31, Year Ended December 31, 2021 2020 2019 2021 2020 2019 Expected term (years) 5.5 - 6.1 5.5 - 6.0 5.8 - 5.9 0.5 0.5 0.5 Expected volatility 85.4 - 88.1 % 83.8 - 91.9 % 78.7 - 83.7 % 64.0 - 77.2 % 101.7 - 114.3 % 73.7 - 109.9 % Risk-free interest rate 0.5 - 1.3 % 0.4 - 1.6 % 1.5 - 2.6 % 0.0 - 0.1 % 0.1 - 0.2 % 1.6 - 2.4 % Expected dividend yield — — — — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Domestic and Foreign Components of Net Loss	The following table presents domestic and foreign components of net loss for the periods presented (in thousands): Year Ended December 31, 2021 2020 2019 Domestic $ ( 54,581 ) $ ( 41,599 ) $ ( 34,181 ) Foreign ( 49 ) ( 143 ) ( 906 ) Total $ ( 54,630 ) $ ( 41,742 ) $ ( 35,087 )
Schedule of Effective Tax Rate of Provision for Income Taxes Differs From Federal Statutory Rate	The effective tax rate of the provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2021 2020 2019 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 1.3 1.1 0.9 Foreign tax rate differential 0.0 0.0 0.2 Permanent differences ( 2.2 ) ( 2.7 ) ( 1.7 ) Research and development credit 4.0 2.6 1.9 Change in valuation allowance ( 24.1 ) ( 22.0 ) ( 22.3 ) Provision for income taxes — % — % — %
Schedule of Components of Deferred Tax Assets and Liabilities	The components of the deferred tax assets and liabilities are as follows (in thousands): Year Ended December 31, 2021 2020 2019 Deferred tax assets Reserves and accruals $ 2,043 $ 1,665 $ 1,056 Net operating loss carryforwards 34,617 24,824 16,986 Research and development credit carryforwards 5,127 2,938 2,177 Lease Liabilities 929 1,148 1,336 Gross deferred tax assets 42,716 30,575 21,555 Valuation allowance ( 41,771 ) ( 29,410 ) ( 20,196 ) Net deferred tax assets 945 1,165 1,359 Deferred tax liabilities Property and equipment ( 375 ) ( 469 ) ( 557 ) Right-of-use asset ( 570 ) ( 696 ) ( 802 ) Net deferred tax assets $ — $ — $ —
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the Company’s unrecognized tax benefits for the year ended December 31, 2021 and 2020 is as follows (in thousands): Year Ended December 31, 2021 2020 Balance at the beginning of the year $ 868 $ — Increase related to prior year tax positions — 381 Increase related to current year tax positions 775 487 Balance at the end of the year $ 1,643 $ 868

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Calculation of Basic and Diluted Net Loss per Share	The following table sets forth the calculation of basic and diluted net loss per share during the periods presented (in thousands, except share and per share data): Year Ended December 31, 2021 2020 2019 Numerator: Net loss $ ( 54,630 ) $ ( 41,742 ) $ ( 35,087 ) Denominator: Weighted-average shares of common stock outstanding 52,759,335 44,004,190 19,083,826 Net loss per share, basic and diluted $ ( 1.04 ) $ ( 0.95 ) $ ( 1.84 )
Anti-dilutive Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share	The following outstanding shares of common stock equivalents were excluded from the computation of the diluted net loss per share for the periods presented because their effect would have been anti-dilutive: Year Ended December 31, 2021 2020 2019 Options to purchase common stock 6,945,184 4,489,122 3,107,066 Common stock subject to future vesting — 8,859 30,027 Total 6,945,184 4,497,981 3,137,093

Organization and Description _2

Organization and Description of the Business - Additional Information (Details)	Jun. 11, 2020USD ($)$ / sharesshares	Feb. 04, 2020USD ($)$ / sharesshares	Jul. 31, 2020shares	Mar. 15, 2022USD ($)$ / sharesshares	Dec. 31, 2021USD ($)Segment$ / sharesshares	Nov. 30, 2021USD ($)Tranche	Dec. 31, 2020USD ($)shares
Organization And Description Of Business [Line Items]
Number of operating segments | Segment					1
Accumulated deficit					$ 180,654,000		$ 126,024,000
Issuance of common stock | shares					9,352,359
Weighted average purchase price, per share | $ / shares					$ 11.13
Pre funded warrants to purchase shares of common stock | shares	909,091	2,884,615			3,793,706
Pre funded warrants exercise price | $ / shares	$ 0.001	$ 0.001			$ 0.001
Net proceeds under at-the-market offering programs					$ 100,970,000
Common stock, shares authorized | shares					125,000,000		125,000,000
Preferred stock, shares authorized | shares					10,000,000		10,000,000
Underwritten Public Offering
Organization And Description Of Business [Line Items]
Issuance of common stock | shares	7,590,909	18,965,385	427,707
Pre funded warrants to purchase shares of common stock | shares	909,091	2,884,615
Pre funded warrants exercise price | $ / shares	$ 0.001	$ 0.001
Common stock, shares issued, price per share | $ / shares	5.50	2.60
Warrant issue price per share | $ / shares	$ 5.499	$ 2.599
Net proceeds from the public offering	$ 45,800,000	$ 53,400,000
Commission paid					$ 3,100,000
Underwritten Public Offering | Existing Stockholder, Equal Talent Investments Limited, and one of the Directors
Organization And Description Of Business [Line Items]
Net proceeds from the public offering	$ 8,500,000
Underwritten Public Offering | Existing Stockholder, Morningside Ventures and certain officers and directors
Organization And Description Of Business [Line Items]
Net proceeds from the public offering		$ 10,400,000
ATM Offering Program
Organization And Description Of Business [Line Items]
Net proceeds from the public offering					$ 101,000,000
Subsequent Event | ATM Offering Program
Organization And Description Of Business [Line Items]
Gross proceeds from ATM program				$ 6,400,000
Issuance of common stock | shares				424,043
Weighted average purchase price, per share | $ / shares				$ 15.04
Loan and Security Agreement | Oxford Finance LLC
Organization And Description Of Business [Line Items]
Line of credit facility, maximum borrowing capacity						$ 50,000,000
Number of tranches | Tranche						5
Loan and Security Agreement | Oxford Finance LLC | Tranche One
Organization And Description Of Business [Line Items]
Current borrowing capacity						$ 10,000,000
Minimum
Organization And Description Of Business [Line Items]
Sufficient cash and cash equivalents available period term					12 months

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Impairment losses	$ 0
Reduction of research and development expenses	0	$ 58,000	$ 635,000
Research and development tax credit receivable	70,000	$ 766,000
Interest charges or penalties related to unrecognized tax benefits	0
Restricted cash	$ 0
Furniture, Laboratory and Office Equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	5 years
Furniture, Laboratory and Office Equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	7 years
Computer Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	3 years
Australia
Summary Of Significant Accounting Policies [Line Items]
Concentrations of credit risk	$ 700,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	$ 205,848	$ 138,566
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	142,481	127,055
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	63,367	11,511
U.S. Treasury money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	60,375	19,347
U.S. Treasury money market funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	60,375	19,347
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	82,106	107,708
U.S. Treasury Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	82,106	107,708
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	46,687	1,000
Commercial paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	46,687	1,000
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	15,481	10,511
Corporate debt securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	15,481	$ 10,511
U.S. Government agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	1,199
U.S. Government agency bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	$ 1,199

Available-for-Sale Securities -

Available-for-Sale Securities - Summary of Available-For-Sale Securities Recorded in Cash and Cash Equivalents or Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 205,943
Fair Value	205,848
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	205,943	$ 138,557
Unrealized Gains	13	15
Unrealized Losses	(108)	(6)
Fair Value	205,848	138,566
Fair Value, Measurements, Recurring | U.S. Treasury money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	60,375	19,347
Fair Value	60,375	19,347
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	82,204	107,703
Unrealized Gains		10
Unrealized Losses	(98)	(5)
Fair Value	82,106	107,708
Fair Value, Measurements, Recurring | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	46,678	998
Unrealized Gains	13	2
Unrealized Losses	(4)
Fair Value	46,687	1,000
Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	15,486	10,509
Unrealized Gains		3
Unrealized Losses	(5)	(1)
Fair Value	15,481	$ 10,511
Fair Value, Measurements, Recurring | U.S. agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	1,200
Unrealized Losses	(1)
Fair Value	$ 1,199

Available-for-Sale Securities_2

Available-for-Sale Securities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Allowance for credit losses on securities in unrealized loss position	$ 0	$ 0
Sale of available-for-sale securities	$ 0

Available-for-Sale Securities_3

Available-for-Sale Securities - Summary of Gross Unrealized Losses and Fair Value by Major Security Type for Available-For-Sale Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 112,520	$ 52,208
Unrealized Losses	(108)	(6)
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	82,106	43,202
Unrealized Losses	(98)	(5)
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	13,734
Unrealized Losses	(4)
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	15,481	9,006
Unrealized Losses	(5)	$ (1)
U.S. agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	1,199
Unrealized Losses	$ (1)

Available-for-Sale Securities_4

Available-for-Sale Securities - Summary of Amortized Cost and Estimated Fair Value of Available-for-sale Securities by Contractual Maturity (Details) $ in Thousands	Dec. 31, 2021USD ($)
Available-for-sale securities maturing, Amortized Cost:
In one year or less, Amortized Cost	$ 205,943
Amortized Cost	205,943
Available-for-sale securities maturing, Estimated Fair Value:
In one year or less, Estimated Fair Value	205,848
Total available-for-sale securities, Estimated Fair Value	$ 205,848

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 6,935	$ 6,177
Less accumulated depreciation and amortization	(3,652)	(2,742)
Property and equipment, net	3,283	3,435
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	3,268	3,268
Furniture, Laboratory and Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	3,423	2,750
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	$ 244	$ 159

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Depreciation expense	$ 0.9	$ 0.9	$ 0.9

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued preclinical and research costs	$ 1,043	$ 461
Accrued clinical costs	1,642	929
Accrued employee-related costs	1,970	1,355
Accrued professional services	231	103
Other	99	173
Total accrued liabilities	$ 4,985	$ 3,021

Lease - Additional Information

Lease - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)ft²	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Operating lease existence of option to extend [true false]		true
Operating lease, option to extend	The operating lease agreement has one option to extend the lease term for a period of five years at the fair market rate at the time of the extension.
Operating lease, renewal term	5 years
Weighted average remaining lease term	3 years 1 month 28 days
Operating lease liability, weighted average discount rate	10.00%
Rent expense	$ 1,100	$ 1,100	$ 1,100
Variable lease costs	$ 765	$ 542	$ 505
South San Francisco, California [Member]
Area of lease | ft²	24,357
Lease commenced date	Mar. 1, 2018
Lease expiration date	Feb. 28, 2025

Lease - Details of Right-of-Use

Lease - Details of Right-of-Use Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee Disclosure [Abstract]
Cash paid for operating lease liabilities	$ 1,042	$ 900	$ 774
Operating lease costs	1,099	1,099	1,099
Variable lease costs	765	542	$ 505
2022	1,588
2023	1,635
2024	1,684
2025	282
Total undiscounted lease payments	5,189
Less: imputed interest	(767)
Total lease liabilities	4,422
Operating lease liabilities, current	1,199	1,042
Operating lease liabilities, noncurrent	3,223	$ 4,422
Total operating lease liabilities	$ 4,422

Debt - Additional Information (

Debt - Additional Information (Details) - Loan and Security Agreement - Oxford Finance LLC	1 Months Ended	12 Months Ended
	Nov. 30, 2021USD ($)Tranche	Dec. 31, 2021USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000
Number of tranches | Tranche	5
Line of credit facility, Maturity period	Nov. 1, 2026
Line of credit facility frequency of payments		monthly interest-only payments
Line of credit facility, extension period	1 year
Final payment fee percentage	6.50%
Interest expense		$ 200,000
Effective interest rate percentage	11.00%
Minimum
Debt Instrument [Line Items]
Prepayment fee percentage	1.00%
Maximum
Debt Instrument [Line Items]
Prepayment fee percentage	2.00%
Tranche One
Debt Instrument [Line Items]
Current borrowing capacity	$ 10,000,000
Tranche Two
Debt Instrument [Line Items]
Current borrowing capacity	10,000,000
Tranche, available period		July 1, 2022 to December 30, 2022
Tranche Three
Debt Instrument [Line Items]
Current borrowing capacity	$ 20,000,000
Equal To Sum Of A | Floor Rate
Debt Instrument [Line Items]
Line of credit facility, additional interest rate	0.08%
Equal To Sum Of B
Debt Instrument [Line Items]
Line of credit facility, interest rate	7.87%

Debt - Schedule of Long-term De

Debt - Schedule of Long-term Debt Balance (Details) $ in Thousands	Dec. 31, 2021USD ($)
Debt Disclosure [Abstract]
Principal loan balance	$ 10,000
Unamortized debt discount and issuance costs	(431)
Cumulative accretion of final fee	53
Long-term debt, net	$ 9,622

Debt - Schedule of Estimated Fu

Debt - Schedule of Estimated Future Principal Payments (Details) $ in Thousands	Dec. 31, 2021USD ($)
Debt Disclosure [Abstract]
2025	$ 5,217
2026	4,783
Total	$ 10,000

Pre-Funded Warrants - Additiona

Pre-Funded Warrants - Additional Information (Details) - $ / shares	1 Months Ended
	Jun. 30, 2020	Feb. 29, 2020	Dec. 31, 2021	Jun. 11, 2020	Feb. 04, 2020
Class Of Warrant Or Right [Line Items]
Pre funded warrants to purchase shares of common stock			3,793,706	909,091	2,884,615
Pre funded warrants exercise price			$ 0.001	$ 0.001	$ 0.001
Maximum ownership percentage, not to exceed upon exercise of warrants			4.99%
Maximum ownership percentage, increase or decrease upon prior notice			19.99%
Pre-funded warrants exercised			0
February Offering
Class Of Warrant Or Right [Line Items]
Pre funded warrants to purchase shares of common stock		2,884,615
Warrant issue price per share		$ 2.599
June Offering
Class Of Warrant Or Right [Line Items]
Pre funded warrants to purchase shares of common stock	909,091
Warrant issue price per share	$ 5.499

Pre-Funded Warrants - Summary o

Pre-Funded Warrants - Summary of Pre-Funded Warrants Outstanding (Details) - $ / shares	Jun. 11, 2020	Feb. 04, 2020	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
Issue Date	Jun. 11, 2020	Feb. 4, 2020
Exercise Price	$ 0.001	$ 0.001	$ 0.001
Expiration Date	Jun. 11, 2040	Feb. 4, 2040
Number of shares underlying	909,091	2,884,615	3,793,706

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options shares outstanding	6,945,184	4,489,122
Common stock, shares issued	56,259,747	46,359,743
Aggregate intrinsic value of exercised stock options	$ 2,107,000	$ 200,000
Period for right to purchase underlying option shares lapses after applicable vesting commencement date	1 year
Payments of dividends of common stock	$ 0
Expected dividend yield	0.00%
Early Exercise Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	36 months
Nonvested common shares outstanding	0	8,859
Percentage of underlying option shares whose right to purchase lapses after applicable vesting commencement date	25.00%
Right to repurchase shares underlying shares	0.0208
Other Current Liabilities | Early Exercise Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued upon early exercise of stock options are subject to repurchase	$ 0	$ 21,000
Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 14,700,000
Estimated weighted average amortization period	2 years 7 months 6 days
Employee options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	6 years 1 month 6 days	6 years	5 years 10 months 24 days
Employee options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	5 years 6 months	5 years 6 months	5 years 9 months 18 days
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	6 months	6 months	6 months
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for future issuance	709,804
Number of shares will increase automatically through every year on specified date	--01-01
Number of shares increase automatically continuing through maximum period	beginning on January 1, 2019 and continuing through and including January 1, 2028
Weighted average grant date fair value of options granted	$ 4.20	$ 2.76
2018 Equity Incentive Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares authorized available for issuance	1,600,692
Increase in number of shares reserved for issuance as percentage of total number of shares of capital stock outstanding on last date of preceding calendar year	5.00%
2018 Equity Incentive Plan | Maximum | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares authorized available for issuance	4,000,000
2018 Equity Incentive Plan | Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options shares outstanding	5,327,356
2018 Equity Incentive Plan | Incentive Stock Options | Maximum | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares issued upon exercise of incentive stock options	12,500,000
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
Options to purchase of common stock outstanding	1,617,828
2015 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted expiry period	10 years
2018 Employee Stock Purchase Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for future issuance	711,992			200,000
Common stock, shares issued	246,232
Authorized an offering beginning period	Nov. 16, 2018
Authorized an offering ending period	May 15, 2019
Authorized an additional offering beginning period	Nov. 16, 2021
2018 Employee Stock Purchase Plan | Maximum | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of annual increase in number of common stock shares	1.00%
Annual increase in number of common stock shares	375,000
Option price per share of common stock at fair market value	85.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity under Stock Option Plans and Related Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Number of options outstanding, Outstanding, Beginning balance	4,489,122
Number of options outstanding, Options granted	3,574,500
Number of options outstanding, Options exercised	(439,081)
Number of options outstanding, Options cancelled/forfeited	(679,357)
Number of options outstanding, Outstanding, Ending balance	6,945,184	4,489,122
Number of options outstanding, options vested and exercisable	3,369,559
Weighted average exercise price, Outstanding, Beginning balance	$ 6.14
Weighted average exercise price, Options granted	5.81
Weighted average exercise price, Options exercised	3.59
Weighted average exercise price, Options cancelled/forfeited	7.97
Weighted average exercise price, Outstanding, Ending balance	5.95	$ 6.14
Weighted average exercise price, options vested and exercisable	$ 5.79
Weighted average remaining contractual term, (Years) Outstanding, Beginning balance	7 years 10 months 24 days	7 years 9 months 18 days
Weighted average remaining contractual term, (Years) options vested and exercisable	6 years 9 months 18 days
Aggregate intrinsic value, Outstanding, Beginning balance	$ 7,134
Aggregate intrinsic value, Options exercised	2,107	$ 200
Aggregate intrinsic value, Outstanding, Ending balance	77,363	$ 7,134
Aggregate intrinsic value, options vested and exercisable	$ 38,713

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 7,596	$ 4,943	$ 4,007
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,955	2,102	1,777
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,641	$ 2,841	$ 2,230

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value of Employee Stock Options Granted and ESPP Rights to Purchase Common Stock Calculated Using Black Scholes Option Pricing Model with Weighted Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield	0.00%
Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	85.40%	83.80%	78.70%
Expected volatility, Maximum	88.10%	91.90%	83.70%
Risk-free interest rate, Minimum	0.50%	0.40%	1.50%
Risk-free interest rate, Maximum	1.30%	1.60%	2.60%
ESPP Rights
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 months	6 months	6 months
Expected volatility, Minimum	64.00%	101.70%	73.70%
Expected volatility, Maximum	77.20%	114.30%	109.90%
Risk-free interest rate, Minimum	0.00%	0.10%	1.60%
Risk-free interest rate, Maximum	0.10%	0.20%	2.40%
Minimum | Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 6 months	5 years 6 months	5 years 9 months 18 days
Maximum | Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years 1 month 6 days	6 years	5 years 10 months 24 days

License Agreement - Additional

License Agreement - Additional Information (Details)	1 Months Ended
	Jun. 30, 2015USD ($)
License Agreement | Amgen, Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum future payments upon achievement of certain development and commercial milestones	$ 172,500,000

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Details) - Savings and Investment Plan - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Employees contributions amount up to lesser of pre-tax compensation	$ 56,000
Percentage of employees contributions amount up to lesser of pre-tax compensation	100.00%
Employer match of per contribution towards participants contribution	$ 1
Participants of plan per contribution	1
Employer incurred matching contribution expenses	$ 423,000	$ 326,000	$ 249,000
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer match of employees contributions in amount in percentage	4.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes Disclosure [Line Items]
Provision for income taxes		$ 0	$ 0	$ 0
Research and development tax credit utilized against employer's portion of payroll tax	$ 250,000
Research and development tax credit utilized as reduction of payroll expenses		325,000	373,000	284,000
Valuation allowance increased		12,400,000	9,200,000	$ 7,600,000
Benefit for deferred tax assets		0
Unrecognized tax benefits		1,643,000	$ 868,000
Liability related to uncertain tax positions		0
Accrued interest and penalties related to gross unrecognized tax benefits		0
Australian Taxation Office
Income Taxes Disclosure [Line Items]
Net operating loss (NOL) carryforwards		600,000
Federal
Income Taxes Disclosure [Line Items]
Net operating loss (NOL) carryforwards		$ 156,400,000
Net operating loss carryforwards expiration start year		2035
Net operating loss (NOL) carryforwards indefinite		$ 134,400,000
Federal | Research and Development
Income Taxes Disclosure [Line Items]
Tax credit carryforward expiration start year		2035
Tax credit carryforward		$ 4,600,000
State
Income Taxes Disclosure [Line Items]
Net operating loss (NOL) carryforwards		$ 17,300,000
Net operating loss carryforwards expiration start year		2035
State | Research and Development
Income Taxes Disclosure [Line Items]
Tax credit carryforward		$ 2,600,000

Income Taxes - Schedule of Dome

Income Taxes - Schedule of Domestic and Foreign Components of Net Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Net loss	$ (54,630)	$ (41,742)	$ (35,087)
Domestic
Operating Loss Carryforwards [Line Items]
Net loss	(54,581)	(41,599)	(34,181)
Foreign
Operating Loss Carryforwards [Line Items]
Net loss	$ (49)	$ (143)	$ (906)

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Tax Rate of Provision for Income Taxes Differs From Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
State taxes, net of federal benefit	1.30%	1.10%	0.90%
Foreign tax rate differential	0.00%	0.00%	0.20%
Permanent differences	(2.20%)	(2.70%)	(1.70%)
Research and development credit	4.00%	2.60%	1.90%
Change in valuation allowance	(24.10%)	(22.00%)	(22.30%)

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
Reserves and accruals	$ 2,043	$ 1,665	$ 1,056
Net operating loss carryforwards	34,617	24,824	16,986
Research and development credit carryforwards	5,127	2,938	2,177
Lease Liabilities	929	1,148	1,336
Gross deferred tax assets	42,716	30,575	21,555
Valuation allowance	(41,771)	(29,410)	(20,196)
Net deferred tax assets	945	1,165	1,359
Deferred tax liabilities
Property and equipment	(375)	(469)	(557)
Right-of-use asset	$ (570)	$ (696)	$ (802)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Components of Deferred Tax Assets and Liabilities [Abstract]
Balance at the beginning of the year	$ 868
Increase related to prior year tax positions		$ 381
Increase related to current year tax positions	775	487
Balance at the end of the year	$ 1,643	$ 868

Net Loss Per Share - Calculatio

Net Loss Per Share - Calculation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (54,630)	$ (41,742)	$ (35,087)
Denominator:
Weighted-average shares of common stock outstanding	52,759,335	44,004,190	19,083,826
Net loss per common share, basic and diluted	$ (1.04)	$ (0.95)	$ (1.84)

Net Loss Per Share - Anti-dilut

Net Loss Per Share - Anti-dilutive Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	6,945,184	4,497,981	3,137,093
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	6,945,184	4,489,122	3,107,066
Common stock subject to future vesting [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share		8,859	30,027

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited) - Schedule of Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Operating expenses	$ 54,659	$ 42,950	$ 37,342
Net loss	$ (54,630)	$ (41,742)	$ (35,087)
Net loss per common share, basic and diluted	$ (1.04)	$ (0.95)	$ (1.84)