Kezar Life Sciences (KZR) 10-K 11 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 08, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
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	No
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		48,066,343
Entity Public Float			$ 174
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 2021 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, 2020.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 21,228	$ 14,951
Marketable securities	119,219	63,255
Prepaid expenses	2,733	1,878
Other current assets	1,631	1,048
Total current assets	144,811	81,132
Property and equipment, net	3,435	4,282
Operating lease right-of-use asset	3,314	3,817
Other assets	282	282
Total assets	151,842	89,513
Current liabilities:
Accounts payable	2,358	823
Accrued liabilities	3,021	4,218
Operating lease liabilities, current	1,042	900
Other liabilities, current	21	62
Total current liabilities	6,442	6,003
Operating lease liabilities, noncurrent	4,422	5,464
Total liabilities	10,864	11,467
Stockholders' equity:
Common stock, $0.001 par value, 125,000,000 shares authorized as of December 31, 2020 and 2019; 46,359,743 and 19,208,077 shares issued and outstanding as of December 31, 2020 and 2019, respectively	46	19
Preferred stock, $0.001 par value, 10,000,000 shares authorized, zero shares issued and outstanding as of December 31, 2020 and 2019
Additional paid-in capital	267,093	162,505
Accumulated other comprehensive loss	(137)	(196)
Accumulated deficit	(126,024)	(84,282)
Total stockholders' equity	140,978	78,046
Total liabilities and stockholders' equity	$ 151,842	$ 89,513

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
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	46,359,743	19,208,077
Common stock, shares outstanding	46,359,743	19,208,077
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, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 30,981	$ 27,363	$ 18,136
General and administrative	11,969	9,979	6,590
Total operating expenses	42,950	37,342	24,726
Loss from operations	(42,950)	(37,342)	(24,726)
Interest income	1,208	2,255	1,559
Net loss	$ (41,742)	$ (35,087)	$ (23,167)
Net loss per common share, basic and diluted	$ (0.95)	$ (1.84)	$ (2.26)
Weighted-average shares used to compute net loss per common share, basic and diluted	44,004,190	19,083,826	10,264,584

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (41,742)	$ (35,087)	$ (23,167)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	82	(45)	(72)
Unrealized (loss) gain on marketable securities	(23)	52	(20)
Total other comprehensive income (loss), net of tax	59	7	(92)
Comprehensive loss	$ (41,683)	$ (35,080)	$ (23,259)

Consolidated Statement of Redee

Consolidated Statement of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2017	$ (25,687)		$ 1	$ 451	$ (111)	$ (26,028)
Balance, shares at Dec. 31, 2017			948,578
Balance at Dec. 31, 2017		$ 77,931
Balance, shares at Dec. 31, 2017		12,263,126
Conversion of redeemable convertible preferred stock to common stock	77,931		$ 12	77,919
Conversion of redeemable convertible preferred stock to common stock, shares			12,263,126
Conversion of redeemable convertible preferred stock to common stock		$ (77,931)
Conversion of redeemable convertible preferred stock to common stock, shares		(12,263,126)
Issuance of common stock upon initial public offering, net of issuance costs	77,695		$ 6	77,689
Issuance of common stock upon initial public offering, net of issuance costs, shares			5,750,000
Issuance of common stock under employee stock incentive plans, net of amount related to early exercised options	55			55
Issuance of common stock under employee stock incentive plans, net of amount related to early exercised options, shares			142,528
Issuance of common stock upon vesting of restricted stock units			10,189
Vesting related to shares of common stock issued pursuant to early exercises	69			69
Stock-based compensation expense	1,993			1,993
Other comprehensive income (loss)	(92)				(92)
Net loss	(23,167)					(23,167)
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, net of amount related to early exercised options	272			272
Issuance of common stock under employee stock incentive plans, net of amount related to early exercised options, 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 (loss)	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, net of amount related to early exercised options	470			470
Issuance of common stock under employee stock incentive plans, net of amount related to early exercised options, 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 (loss)	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

Consolidated Statement of Red_2

Consolidated Statement of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Statement Of Stockholders Equity [Abstract]
Issuance of common stock and pre-funded warrants through underwritten offerings, offering costs	$ 6,748

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (41,742)	$ (35,087)	$ (23,167)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,544	1,301	690
Stock-based compensation	4,943	4,007	1,993
Amortization of premiums and discounts on marketable securities	317	(979)	(476)
Loss on disposal of property and equipment			106
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(1,424)	(553)	(1,136)
Other assets			61
Accounts payable and accrued liabilities	313	2,208	1,440
Operating lease liabilities and other liabilities	(900)	(774)	(8)
Deferred rent			(295)
Net cash used in operating activities	(36,949)	(29,877)	(20,792)
Cash flows from investing activities:
Purchases of property and equipment	(194)	(607)	(1,120)
Purchases of marketable securities	(225,728)	(102,255)	(119,244)
Maturities of marketable securities	169,424	123,281	36,450
Proceeds from sale of property and equipment			10
Net cash provided by (used in) investing activities	(56,498)	20,419	(83,904)
Cash flows from financing activities:
Proceeds from sale of common stock and pre-funded warrants in underwritten offerings, net of offering costs	99,186		77,695
Proceeds from issuance of common stock under employee stock incentive plans	456	272	218
Net cash provided by financing activities	99,642	272	77,913
Effect of exchange rate changes on cash, cash equivalents and restricted cash	82	(45)	(81)
Net (decrease) increase in cash, cash equivalents and restricted cash	6,277	(9,231)	(26,864)
Cash, cash equivalents and restricted cash at the beginning of period	14,951	24,182	51,046
Cash, cash equivalents and restricted cash at the end of period	21,228	14,951	24,182
Supplemental disclosures of noncash investing and financing information:
Reclassification of employee stock liability to equity upon vesting	41	$ 50	69
Addition of tenant improvement paid by landlord			2,703
Purchase of property and equipment in accounts payable			38
Conversion of redeemable convertible preferred stock into common stock			$ 77,931
Unpaid offering costs in accrued liabilities	$ 25

Organization and Description of

Organization and Description of the Business	12 Months Ended
	Dec. 31, 2020
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. Reverse Stock Split On June 8, 2018, the Company filed an Amended and Restated Certificate of Incorporation effecting a 1-for-5.62 reverse stock split of its issued and outstanding shares of common stock and redeemable convertible preferred stock. The par value of the authorized stock was not adjusted as a result of the reverse stock split. In connection with the reverse stock split, the filed Amended and Restated Certificate of Incorporation also adjusted the minimum price per share required in a firm-commitment underwritten public offering of the Company’s common stock in order for the preferred stock to automatically convert to common stock. The minimum price post-split was $15.884 and was adjusted to $7.942. The Company did not adjust the number of authorized shares of common stock or redeemable convertible preferred stock. Other than the par value and the number of authorized shares of common stock and preferred stock, all share and per share data shown in the accompanying consolidated financial statements and related notes have been retroactively revised to reflect the reverse stock split. 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 candidate, KZR-616. 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 $126.0 million as of December 31, 2020. 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, 2020 will be sufficient to fund the Company’s cash requirements for at least 12 months following the issuance of these financial statements. In September 2020, the Company entered into a Sales Agreement (the “ATM Agreement”) with Cowen and Company, LLC (“Cowen”), pursuant to which the Company can offer and sell, from time to time at its sole discretion through Cowen, as its sales agent, shares of common stock having an aggregate offering price of up to $50.0 million. Any shares of common stock sold will be issued pursuant to the Company’s shelf registration statement on Form S-3 (File No. 333-248752 3.0 approximately $11 million worth 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 our 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, an affiliate of Morningside Venture Investments Ltd, 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 our 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, together with its affiliate, Equal Talent Investments Limited, and certain of the Company’s officers and directors purchased an aggregate of approximately $22.9 million of common stock in the February Offering. On June 25, 2018, the Company completed its initial public offering (“IPO”), whereby the Company issued 5,750,000 shares of its common stock (inclusive of 750,000 shares of common stock pursuant to the full exercise of an overallotment option granted to the underwriters in connection with the offering) at a price of $15.00 per share. The shares began trading on The Nasdaq Global Select Market on June 21, 2018. The net proceeds received by the Company from the offering were approximately $77.7 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company of approximately $8.6 million. Upon the closing of the IPO, all outstanding shares of redeemable convertible preferred stock converted into 12,263,126 shares of common stock. Additionally, the Company is now authorized to issue 125,000,000 shares of common stock and 10,000,000 shares of preferred stock.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
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, useful lives of fixed assets, 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. We also anticipate that the COVID-19 pandemic will continue to have an impact on the clinical and preclinical development timelines for our 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 With the global spread of the ongoing COVID-19 pandemic beginning in the first quarter of 2020, we have implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on our business. The extent to which the COVID-19 pandemic impacts our business, our preclinical and clinical development and regulatory efforts, our corporate development objectives and the value of and market for our 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 U nited 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 our business, financial condition, results of operations and growth prospects. In addition, we are subject to other challenges and risks specific to our business and our ability to execute on our 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 our product candidates; delays or problems in the supply of our 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 our intellectual property rights; and complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects our 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. 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, 2020, the majority of the Company’s cash , cash equivalents and marketable securities were held by financial institutions in the United States, while approximately $ 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 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 The Company adopted ASU 2016-02, Leases (Topic 842) on January 1, 2019 using the modified retrospective approach and utilizing the effective date as its date of initial application, for which prior periods are presented in accordance with the previous guidance in ASC 840, 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 elected the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, the Company will not recognize ROU assets or lease liabilities, and this includes not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. The Company separately accounts for lease and non-lease components for all of its leases. 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 nonemployees 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 $58,000, $635,000 and $5,000 as a reduction of research and development expenses for the years ended December 31, 2020, 2019 and 2018, respectively, in connection with the research and development tax incentive from the ATO. As of December 31, 2020 and 2019, the research and development tax credit receivable was $766,000 and $642,000, 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. Accounting Pronouncements Adopted in 2020 In June 2016, the FASB issued ASU No. 2016-13 , Financial Instruments-Credit Losses (Topic 326) The Company adopted the new standard using the modified retrospective approach as of January 1, 2020 and the adoption In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement The amendment of ASU No. 2018-13 removes disclosure requirements from Topic 820 in the areas of: (1) the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy; (2) the policy for timing of transfers between levels; and (3) the valuation processes for Level 3 fair value measurements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes: Simplifying the Accounting for Income Taxes Income Taxes. As part of the simplification, along with other exceptions, it removes the exception to the incremental approach for intraperiod tax allocation in the event of a loss from continuing operations and income or a gain from other items. he adoption did not have a material impact on its

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
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, 2020 or 2019. 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, 2020 Financial Assets: Total Level 1 Level 2 Level 3 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 $ — December 31, 2019 Financial Assets: Total Level 1 Level 2 Level 3 Money market funds $ 14,731 $ 14,731 $ — $ — U.S. Treasury securities 5,285 5,285 — — Commercial paper 15,186 — 15,186 — Corporate debt securities 17,171 — 17,171 — U.S. agency bonds 25,613 — 25,613 — Total $ 77,986 $ 20,016 $ 57,970 $ —

Available-for-Sale Securities

Available-for-Sale Securities	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019 (in thousands): December 31, 2020 Financial Assets: Amortized Cost Unrealized Gains Unrealized Losses Fair Value 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 December 31, 2019 Financial Assets: Amortized Cost Unrealized Gains Unrealized Losses Fair Value Money market funds $ 14,731 $ — $ — $ 14,731 U.S. Treasury securities 5,285 1 (1 ) 5,285 Commercial paper 15,174 12 — 15,186 Corporate debt securities 17,168 3 — 17,171 U.S. agency bonds 25,597 16 — 25,613 Total $ 77,955 $ 32 $ (1 ) $ 77,986 The Company has not recognized an allowance for credit losses on any securities in an unrealized loss position as of December 31, 2020 and 2019. 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, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Less than 12 consecutive months Less than 12 consecutive months Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities $ 43,202 $ (5 ) $ 4,535 $ (1 ) Corporate debt securities 9,006 (1 ) — — Total $ 52,208 $ (6 ) $ 4,535 $ — 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, 2020, 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 $ 138,557 $ 138,566 Total available-for-sale securities $ 138,557 $ 138,566 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, 2020. 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, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Property and Equipment, Net Property and equipment consisted of the following as of December 31, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Leasehold improvements $ 3,268 $ 3,268 Furniture, laboratory and office equipment 2,750 2,578 Computer equipment 159 253 Total property and equipment 6,177 6,099 Less accumulated depreciation and amortization (2,742 ) (1,817 ) Property and equipment, net $ 3,435 $ 4,282 Depreciation expense was $0.9 million for the year ended December 31, 2020, $0.9 million for the year ended December 31, 2019 and $0.7 million for the year ended December 31, 2018. Accrued Liabilities Accrued liabilities consisted of the following as of December 31, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Accrued preclinical and research costs $ 461 $ 1,687 Accrued clinical costs 929 1,027 Accrued employee-related costs 1,355 1,293 Accrued professional services 103 53 Other 173 158 Total accrued liabilities $ 3,021 $ 4,218

Lease

Lease	12 Months Ended
	Dec. 31, 2020
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, we 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 our 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, 2020, the weighted average remaining lease term was 4.17 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, 2020 2019 Cash paid for operating lease liabilities $ 900 $ 774 Operating lease costs 1,099 1,099 Variable lease costs 542 505 Maturities of lease liabilities as of December 31, 2020 were as follows for the years ending December 31: 2021 $ 1,542 2022 1,588 2023 1,635 2024 1,684 2025 282 Total undiscounted lease payments 6,731 Less: imputed interest (1,267 ) Total lease liabilities $ 5,464 Operating lease liabilities, current 1,042 Operating lease liabilities, noncurrent 4,422 Total operating lease liabilities $ 5,464 For the years ended December 31, 2020, 2019 and 2018, the Company recognized $1.1 million, $1.1 million and $1.0 million of rent expense, respectively. Variable lease costs were $0.5 million, $0.5 million and $0.4 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2020
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	7. Redeemable Convertible Preferred Stock In connection with the completion of the Company’s IPO in June 2018, all outstanding shares of convertible preferred stock converted into 12,263,126 shares of common stock.

Pre-Funded Warrants

Pre-Funded Warrants	12 Months Ended
	Dec. 31, 2020
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 our common stock (together with its affiliates) or the combined voting power of our 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 us 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, 2020, 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, 2020. 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, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [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, 2020, options to purchase 2,689,068 shares of common stock were outstanding under the 2018 Plan and 1,286,960 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, 2020, options to purchase 1,800,054 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, 2020, 137,668 shares of common stock had been issued under the ESPP and 445,556 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, 2020. 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 Options Outstanding Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding at December 31, 2019 3,107,066 $ 7.19 8.2 $ 3,151 Options granted 1,503,876 $ 3.87 Options exercised (56,653 ) $ 1.95 $ 185 Options cancelled/forfeited (65,167 ) $ 7.84 Outstanding at December 31, 2020 4,489,122 $ 6.14 7.8 $ 7,134 Vested and exercisable at December 31, 2020 2,358,197 $ 5.62 7.0 $ 4,627 The weighted average grant date fair value of options granted during the years ended December 31, 2020 and 2019 was $2.76 and $9.33 per share, respectively. The aggregate intrinsic value of exercised stock options during the years ended December 31, 2020 and 2019 was $185,000 and $292,000, 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 our board of directors As of December 31, 2020 and 2019, there were 8,859 and 30,027 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 with the corresponding par value in common stock and an offset in additional paid-in capital . As of December 31, 2020 and 2019 , the Company recorded in other current liabilities $ and $ , 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, 2020 2019 2018 Research and development $ 2,102 $ 1,777 $ 842 General and administrative 2,841 2,230 1,151 Total stock-based compensation expense $ 4,943 $ 4,007 $ 1,993 As of December 31, 2020, the unrecognized stock-based compensation cost was $9.6 million with an estimated weighted average amortization period of 2.4 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, 2020 2019 2018 2020 2019 2018 Expected term (years) 5.5 - 6.0 5.8 - 5.9 5.5 - 6.1 0.5 0.5 0.5 Expected volatility 83.8 - 91.9% 78.7 - 83.7% 82.0 - 83.2% 101.7 - 114.3% 73.7 - 109.9% 74.3 % Risk-free interest rate 0.4 - 1.6% 1.5 - 2.6% 2.6 - 3.1% 0.1 - 0.2% 1.6 - 2.4% 2.5 % 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

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
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, 2020
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, 2020
Compensation And Retirement Disclosure [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, 2020, 2019 and 2018, the Company recorded matching contributions of approximately $326,000, $249,000 and $167,000, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes No provision for income taxes was recorded for the years ended December 31, 2020, 2019 and 2018. 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, 2020 2019 2018 Domestic $ (41,599 ) $ (34,181 ) $ (23,047 ) Foreign (143 ) (906 ) (120 ) Total $ (41,742 ) $ (35,087 ) $ (23,167 ) 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 $373,000, $284,000 and $175,000 of R&D tax credits as a reduction of payroll expenses to offset its payroll tax liabilities for the years ended December 31, 2020, 2019 and 2018, respectively. The effective tax rate of the provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2020 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 1.1 0.9 6.4 Foreign tax rate differential 0.0 0.2 0.1 Permanent differences (2.7 ) (1.7 ) 0.3 Research and development credit 2.6 1.9 1.4 Change in valuation allowance (22.0 ) (22.3 ) (29.2 ) Provision for income taxes — % — % — % The components of the deferred tax assets and liabilities are as follows (in thousands): Year Ended December 31, 2020 2019 2018 Deferred tax assets Reserves and accruals $ 1,665 $ 1,056 $ 1,009 Net operating loss carryforwards 24,824 16,986 10,985 Research and development credit carryforwards 2,938 2,177 1,194 Lease Liabilities 1,148 1,336 — Gross deferred tax assets 30,575 21,555 13,188 Valuation allowance (29,410 ) (20,196 ) (12,560 ) Net deferred tax assets 1,165 1,359 628 Deferred tax liabilities Property and equipment (469 ) (557 ) (628 ) Right-of-use asset (696 ) (802 ) — Net deferred tax $ — $ — $ — 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, 2020, and December 31, 2019 have been fully offset by a valuation allowance. The valuation allowance increased approximately $9.2 million, $7.6 million and $5.1 million during the years ended December 31, 2020, 2019, and 2018, respectively. As of December 31, 2020, the Company had federal net operating loss (“NOL”) carryforward of $109.7 million and a federal research and development tax credit carryforward of $2.4 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 $87.6 million generated from years ended after December 31, 2017, carryforward indefinitely. As of December 31, 2020 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 $1.8 million, which does not expire. As of December 31, 2020, the Company also had accumulated Australian tax losses of $1.9 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, 2020. 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 $0.9 million of unrecognized tax benefits as of December 31, 2020. No liability related to uncertain tax positions is recorded on the financial statements. All uncertain tax positions are currently recorded as a reduction to our 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. Unrecognized Income Tax Benefits Balance as of December 31, 2019 $ — Additions for prior year tax positions 381 Additions for current year tax positions 487 Balance as of December 31, 2020 $ 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, 2020
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, 2020 2019 2018 Numerator: Net loss $ (41,742 ) $ (35,087 ) $ (23,167 ) Denominator: Weighted-average shares of common stock outstanding 44,004,190 19,083,826 10,264,584 Net loss per share, basic and diluted $ (0.95 ) $ (1.84 ) $ (2.26 ) 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, 2020 2019 2018 Options to purchase common stock 4,489,122 3,107,066 2,181,466 Common stock subject to future vesting 8,859 30,027 89,257 Total 4,497,981 3,137,093 2,270,723

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information (Unaudited)	15. Selected Quarterly Financial Information (Unaudited) The following amounts are in thousands, except per share amounts: Quarter Ended (in thousands, except per share amounts) March 31, 2020 June 30, 2020 September 30, 2020 December 31, 2020 (Unaudited) Operating expenses $ 10,478 $ 9,853 $ 11,551 $ 11,068 Net loss $ (10,012 ) $ (9,500 ) $ (11,289 ) $ (10,941 ) Net loss per share, basic and diluted $ (0.30 ) $ (0.22 ) $ (0.23 ) $ (0.22 ) Quarter Ended (in thousands, except per share amounts) March 31, 2019 June 30, 2019 September 30, 2019 December 31, 2019 (Unaudited) Operating expenses $ 8,309 $ 9,355 $ 9,681 $ 9,997 Net loss $ (7,642 ) $ (8,718 ) $ (9,148 ) $ (9,579 ) Net loss per share, basic and diluted $ (0.40 ) $ (0.46 ) $ (0.48 ) $ (0.50 ) Basic and diluted net loss per share is computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share amounts may not equal annual basic and diluted net loss per share amounts.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
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, useful lives of fixed assets, 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. We also anticipate that the COVID-19 pandemic will continue to have an impact on the clinical and preclinical development timelines for our 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 With the global spread of the ongoing COVID-19 pandemic beginning in the first quarter of 2020, we have implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on our business. The extent to which the COVID-19 pandemic impacts our business, our preclinical and clinical development and regulatory efforts, our corporate development objectives and the value of and market for our 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 U nited 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 our business, financial condition, results of operations and growth prospects. In addition, we are subject to other challenges and risks specific to our business and our ability to execute on our 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 our product candidates; delays or problems in the supply of our 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 our intellectual property rights; and complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects our 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.
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, 2020, the majority of the Company’s cash , cash equivalents and marketable securities were held by financial institutions in the United States, while approximately $ 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
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 The Company adopted ASU 2016-02, Leases (Topic 842) on January 1, 2019 using the modified retrospective approach and utilizing the effective date as its date of initial application, for which prior periods are presented in accordance with the previous guidance in ASC 840, 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 elected the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, the Company will not recognize ROU assets or lease liabilities, and this includes not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. The Company separately accounts for lease and non-lease components for all of its leases.
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 nonemployees 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 $58,000, $635,000 and $5,000 as a reduction of research and development expenses for the years ended December 31, 2020, 2019 and 2018, respectively, in connection with the research and development tax incentive from the ATO. As of December 31, 2020 and 2019, the research and development tax credit receivable was $766,000 and $642,000, 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.
Accounting Pronouncements Adopted in 2020	Accounting Pronouncements Adopted in 2020 In June 2016, the FASB issued ASU No. 2016-13 , Financial Instruments-Credit Losses (Topic 326) The Company adopted the new standard using the modified retrospective approach as of January 1, 2020 and the adoption In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement The amendment of ASU No. 2018-13 removes disclosure requirements from Topic 820 in the areas of: (1) the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy; (2) the policy for timing of transfers between levels; and (3) the valuation processes for Level 3 fair value measurements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes: Simplifying the Accounting for Income Taxes Income Taxes. As part of the simplification, along with other exceptions, it removes the exception to the incremental approach for intraperiod tax allocation in the event of a loss from continuing operations and income or a gain from other items. he adoption did not have a material impact on its
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, 2020
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, 2020 Financial Assets: Total Level 1 Level 2 Level 3 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 $ — December 31, 2019 Financial Assets: Total Level 1 Level 2 Level 3 Money market funds $ 14,731 $ 14,731 $ — $ — U.S. Treasury securities 5,285 5,285 — — Commercial paper 15,186 — 15,186 — Corporate debt securities 17,171 — 17,171 — U.S. agency bonds 25,613 — 25,613 — Total $ 77,986 $ 20,016 $ 57,970 $ —

Available-for-Sale Securities (

Available-for-Sale Securities (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019 (in thousands): December 31, 2020 Financial Assets: Amortized Cost Unrealized Gains Unrealized Losses Fair Value 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 December 31, 2019 Financial Assets: Amortized Cost Unrealized Gains Unrealized Losses Fair Value Money market funds $ 14,731 $ — $ — $ 14,731 U.S. Treasury securities 5,285 1 (1 ) 5,285 Commercial paper 15,174 12 — 15,186 Corporate debt securities 17,168 3 — 17,171 U.S. agency bonds 25,597 16 — 25,613 Total $ 77,955 $ 32 $ (1 ) $ 77,986
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, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Less than 12 consecutive months Less than 12 consecutive months Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities $ 43,202 $ (5 ) $ 4,535 $ (1 ) Corporate debt securities 9,006 (1 ) — — Total $ 52,208 $ (6 ) $ 4,535 $ —
Summary of Amortized Cost and Estimated Fair Value of Available-for-sale Securities by Contractual Maturity	As of December 31, 2020, 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 $ 138,557 $ 138,566 Total available-for-sale securities $ 138,557 $ 138,566

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Property and Equipment	Property and equipment consisted of the following as of December 31, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Leasehold improvements $ 3,268 $ 3,268 Furniture, laboratory and office equipment 2,750 2,578 Computer equipment 159 253 Total property and equipment 6,177 6,099 Less accumulated depreciation and amortization (2,742 ) (1,817 ) Property and equipment, net $ 3,435 $ 4,282
Accrued Liabilities	Accrued liabilities consisted of the following as of December 31, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Accrued preclinical and research costs $ 461 $ 1,687 Accrued clinical costs 929 1,027 Accrued employee-related costs 1,355 1,293 Accrued professional services 103 53 Other 173 158 Total accrued liabilities $ 3,021 $ 4,218

Lease (Tables)

Lease (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 Cash paid for operating lease liabilities $ 900 $ 774 Operating lease costs 1,099 1,099 Variable lease costs 542 505 Maturities of lease liabilities as of December 31, 2020 were as follows for the years ending December 31: 2021 $ 1,542 2022 1,588 2023 1,635 2024 1,684 2025 282 Total undiscounted lease payments 6,731 Less: imputed interest (1,267 ) Total lease liabilities $ 5,464 Operating lease liabilities, current 1,042 Operating lease liabilities, noncurrent 4,422 Total operating lease liabilities $ 5,464

Pre-Funded Warrants (Tables)

Pre-Funded Warrants (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020. 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, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [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 Options Outstanding Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding at December 31, 2019 3,107,066 $ 7.19 8.2 $ 3,151 Options granted 1,503,876 $ 3.87 Options exercised (56,653 ) $ 1.95 $ 185 Options cancelled/forfeited (65,167 ) $ 7.84 Outstanding at December 31, 2020 4,489,122 $ 6.14 7.8 $ 7,134 Vested and exercisable at December 31, 2020 2,358,197 $ 5.62 7.0 $ 4,627
Stock-Based Compensation Expense Recognized	Total stock-based compensation expense recognized by function was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Research and development $ 2,102 $ 1,777 $ 842 General and administrative 2,841 2,230 1,151 Total stock-based compensation expense $ 4,943 $ 4,007 $ 1,993
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, 2020 2019 2018 2020 2019 2018 Expected term (years) 5.5 - 6.0 5.8 - 5.9 5.5 - 6.1 0.5 0.5 0.5 Expected volatility 83.8 - 91.9% 78.7 - 83.7% 82.0 - 83.2% 101.7 - 114.3% 73.7 - 109.9% 74.3 % Risk-free interest rate 0.4 - 1.6% 1.5 - 2.6% 2.6 - 3.1% 0.1 - 0.2% 1.6 - 2.4% 2.5 % Expected dividend yield — — — — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Domestic $ (41,599 ) $ (34,181 ) $ (23,047 ) Foreign (143 ) (906 ) (120 ) Total $ (41,742 ) $ (35,087 ) $ (23,167 )
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, 2020 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 1.1 0.9 6.4 Foreign tax rate differential 0.0 0.2 0.1 Permanent differences (2.7 ) (1.7 ) 0.3 Research and development credit 2.6 1.9 1.4 Change in valuation allowance (22.0 ) (22.3 ) (29.2 ) 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, 2020 2019 2018 Deferred tax assets Reserves and accruals $ 1,665 $ 1,056 $ 1,009 Net operating loss carryforwards 24,824 16,986 10,985 Research and development credit carryforwards 2,938 2,177 1,194 Lease Liabilities 1,148 1,336 — Gross deferred tax assets 30,575 21,555 13,188 Valuation allowance (29,410 ) (20,196 ) (12,560 ) Net deferred tax assets 1,165 1,359 628 Deferred tax liabilities Property and equipment (469 ) (557 ) (628 ) Right-of-use asset (696 ) (802 ) — Net deferred tax $ — $ — $ —
Reconciliation of Unrecognized Tax Benefits	A reconciliation of our unrecognized tax benefits for the year ended December 31, 2020 is as follows (in thousands): Unrecognized Income Tax Benefits Balance as of December 31, 2019 $ — Additions for prior year tax positions 381 Additions for current year tax positions 487 Balance as of December 31, 2020 $ 868

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Numerator: Net loss $ (41,742 ) $ (35,087 ) $ (23,167 ) Denominator: Weighted-average shares of common stock outstanding 44,004,190 19,083,826 10,264,584 Net loss per share, basic and diluted $ (0.95 ) $ (1.84 ) $ (2.26 )
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, 2020 2019 2018 Options to purchase common stock 4,489,122 3,107,066 2,181,466 Common stock subject to future vesting 8,859 30,027 89,257 Total 4,497,981 3,137,093 2,270,723

Selected Quarterly Financial _2

Selected Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Selected Quarterly Financial Information (Unaudited)	The following amounts are in thousands, except per share amounts: Quarter Ended (in thousands, except per share amounts) March 31, 2020 June 30, 2020 September 30, 2020 December 31, 2020 (Unaudited) Operating expenses $ 10,478 $ 9,853 $ 11,551 $ 11,068 Net loss $ (10,012 ) $ (9,500 ) $ (11,289 ) $ (10,941 ) Net loss per share, basic and diluted $ (0.30 ) $ (0.22 ) $ (0.23 ) $ (0.22 ) Quarter Ended (in thousands, except per share amounts) March 31, 2019 June 30, 2019 September 30, 2019 December 31, 2019 (Unaudited) Operating expenses $ 8,309 $ 9,355 $ 9,681 $ 9,997 Net loss $ (7,642 ) $ (8,718 ) $ (9,148 ) $ (9,579 ) Net loss per share, basic and diluted $ (0.40 ) $ (0.46 ) $ (0.48 ) $ (0.50 )

Organization and Description _2

Organization and Description of the Business - Additional Information (Details)	Jun. 11, 2020USD ($)$ / sharesshares	Feb. 04, 2020USD ($)$ / sharesshares	Jun. 25, 2018USD ($)$ / sharesshares	Jun. 08, 2018$ / shares	Feb. 28, 2021USD ($)	Sep. 30, 2020USD ($)	Jul. 31, 2020shares	Dec. 31, 2020USD ($)Segment$ / sharesshares	Dec. 31, 2019USD ($)shares
Organization And Description Of Business [Line Items]
Number of operating segments | Segment								1
Stockholders equity, reverse stock split				1-for-5.62
Stockholders equity, stock split, conversion ratio				0.1779
Minimum price post-split | $ / shares				$ 15.884
Adjusted price post split | $ / shares				$ 7.942
Accumulated deficit | $								$ 126,024,000	$ 84,282,000
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
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
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, Equal Talent Investments Limited, and one of the Directors
Organization And Description Of Business [Line Items]
Net proceeds from the public offering | $		$ 22,900,000
IPO
Organization And Description Of Business [Line Items]
Issuance of common stock | shares			5,750,000
Common stock, shares issued, price per share | $ / shares			$ 15
Net proceeds from the public offering | $			$ 77,700,000
Payments of stock issuance costs | $			$ 8,600,000
Convertible preferred stock converted into common stock | shares			12,263,126
Overallotment Option
Organization And Description Of Business [Line Items]
Issuance of common stock | shares			750,000
ATM Agreement | Cowen and Company LLC
Organization And Description Of Business [Line Items]
Percentage of commission on gross sales proceeds of issuance of common stock						3.00%
ATM Agreement | Cowen and Company LLC | Subsequent Event
Organization And Description Of Business [Line Items]
Issuance of common stock | $					$ 11,000,000
Minimum
Organization And Description Of Business [Line Items]
Sufficient cash and cash equivalents available period term								12 months
Maximum | ATM Agreement | Cowen and Company LLC
Organization And Description Of Business [Line Items]
Common stock aggregate offering price | $						$ 50,000,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Impairment losses	$ 0
Reduction of research and development expenses	58,000	$ 635,000	$ 5,000
Research and development tax credit receivable	766,000	$ 642,000
Interest charges or penalties related to unrecognized tax benefits	$ 0
ASU 2016-02
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2019
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
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	$ 100,000

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, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	$ 138,566	$ 77,986
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	127,055	20,016
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	11,511	57,970
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	19,347	14,731
Money Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	19,347	14,731
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	107,708	5,285
U.S. Treasury Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	107,708	5,285
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	1,000	15,186
Commercial paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	1,000	15,186
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	10,511	17,171
Corporate debt securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets	$ 10,511	17,171
U.S. agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets		25,613
U.S. agency bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets		$ 25,613

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, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 138,557
Fair Value	138,566
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	138,557	$ 77,955
Unrealized Gains	15	32
Unrealized Losses	(6)	(1)
Fair Value	138,566	77,986
Fair Value, Measurements, Recurring | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	19,347	14,731
Fair Value	19,347	14,731
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	107,703	5,285
Unrealized Gains	10	1
Unrealized Losses	(5)	(1)
Fair Value	107,708	5,285
Fair Value, Measurements, Recurring | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	998	15,174
Unrealized Gains	2	12
Fair Value	1,000	15,186
Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	10,509	17,168
Unrealized Gains	3	3
Unrealized Losses	(1)
Fair Value	$ 10,511	17,171
Fair Value, Measurements, Recurring | U.S. agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		25,597
Unrealized Gains		16
Fair Value		$ 25,613

Available-for-Sale Securities_2

Available-for-Sale Securities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
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, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 52,208	$ 4,535
Unrealized Losses	(6)
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	43,202	4,535
Unrealized Losses	(5)	$ (1)
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	9,006
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, 2020USD ($)
Available-for-sale securities maturing, Amortized Cost:
In one year or less, Amortized Cost	$ 138,557
Amortized Cost	138,557
Available-for-sale securities maturing, Estimated Fair Value:
In one year or less, Estimated Fair Value	138,566
Total available-for-sale securities, Estimated Fair Value	$ 138,566

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 6,177	$ 6,099
Less accumulated depreciation and amortization	(2,742)	(1,817)
Property and equipment, net	3,435	4,282
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	2,750	2,578
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	$ 159	$ 253

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Depreciation expense	$ 0.9	$ 0.9	$ 0.7

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accrued preclinical and research costs	$ 461	$ 1,687
Accrued clinical costs	929	1,027
Accrued employee-related costs	1,355	1,293
Accrued professional services	103	53
Other	173	158
Total accrued liabilities	$ 3,021	$ 4,218

Lease - Additional Information

Lease - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
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	4 years 2 months 1 day
Operating lease liability, weighted average discount rate	10.00%
Rent expense	$ 1,100	$ 1,100	$ 1,000
Variable lease costs	$ 542	$ 505	$ 400
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, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee Disclosure [Abstract]
Cash paid for operating lease liabilities	$ 900	$ 774
Operating lease costs	1,099	1,099
Variable lease costs	542	505	$ 400
2021	1,542
2022	1,588
2023	1,635
2024	1,684
2025	282
Total undiscounted lease payments	6,731
Less: imputed interest	(1,267)
Total lease liabilities	5,464
Operating lease liabilities, current	1,042	900
Operating lease liabilities, noncurrent	4,422	$ 5,464
Total operating lease liabilities	$ 5,464

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock - Additional Information (Details)	1 Months Ended
	Jun. 30, 2018shares
IPO
Temporary Equity [Line Items]
Number of outstanding shares of convertible preferred stock converted into common stock	12,263,126

Pre-Funded Warrants - Additiona

Pre-Funded Warrants - Additional Information (Details) - $ / shares	1 Months Ended
	Jun. 30, 2020	Feb. 29, 2020	Dec. 31, 2020	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, 2020
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, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options shares outstanding	4,489,122	3,107,066
Common stock, shares issued	46,359,743	19,208,077
Aggregate intrinsic value of exercised stock options	$ 185,000
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	8,859	30,027
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	$ 21,000	$ 62,000
Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 9,600,000
Estimated weighted average amortization period	2 years 4 months 24 days
Employee options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	6 years	5 years 10 months 24 days	6 years 1 month 6 days
Employee options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	5 years 6 months	5 years 9 months 18 days	5 years 6 months
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	1,286,960
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	$ 2.76	$ 9.33
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	2,689,068
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	1,800,054
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	445,556			200,000
Common stock, shares issued	137,668
Authorized an offering beginning period	Nov. 16, 2018
Authorized an offering ending period	May 15, 2019
Authorized an additional offering beginning period	Nov. 16, 2020
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%
2015 and 2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of exercised stock options	$ 185,000	$ 292,000

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, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of options outstanding, Outstanding, Beginning balance	3,107,066
Number of options outstanding, Options granted	1,503,876
Number of options outstanding, Options exercised	(56,653)
Number of options outstanding, Options cancelled/forfeited	(65,167)
Number of options outstanding, Outstanding, Ending balance	4,489,122	3,107,066
Number of options outstanding, options vested and exercisable	2,358,197
Weighted average exercise price, Outstanding, Beginning balance	$ 7.19
Weighted average exercise price, Options granted	3.87
Weighted average exercise price, Options exercised	1.95
Weighted average exercise price, Options cancelled/forfeited	7.84
Weighted average exercise price, Outstanding, Ending balance	6.14	$ 7.19
Weighted average exercise price, options vested and exercisable	$ 5.62
Weighted average remaining contractual term, (Years) Outstanding, Beginning balance	7 years 9 months 18 days	8 years 2 months 12 days
Weighted average remaining contractual term, (Years) options vested and exercisable	7 years
Aggregate intrinsic value, Outstanding, Beginning balance	$ 3,151
Aggregate intrinsic value, Options exercised	185
Aggregate intrinsic value, Outstanding, Ending balance	7,134	$ 3,151
Aggregate intrinsic value, options vested and exercisable	$ 4,627

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,943	$ 4,007	$ 1,993
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,102	1,777	842
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,841	$ 2,230	$ 1,151

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, 2020	Dec. 31, 2019	Dec. 31, 2018
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	83.80%	78.70%	82.00%
Expected volatility, Maximum	91.90%	83.70%	83.20%
Risk-free interest rate, Minimum	0.40%	1.50%	2.60%
Risk-free interest rate, Maximum	1.60%	2.60%	3.10%
ESPP Rights
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 months	6 months	6 months
Expected volatility			74.30%
Expected volatility, Minimum	101.70%	73.70%
Expected volatility, Maximum	114.30%	109.90%
Risk-free interest rate			2.50%
Risk-free interest rate, Minimum	0.10%	1.60%
Risk-free interest rate, Maximum	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 9 months 18 days	5 years 6 months
Maximum | Employee options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years	5 years 10 months 24 days	6 years 1 month 6 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, 2020	Dec. 31, 2019	Dec. 31, 2018
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	$ 326,000	$ 249,000	$ 167,000
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, 2020	Dec. 31, 2019	Dec. 31, 2018
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		373,000	284,000	175,000
Valuation allowance increased		9,200,000	$ 7,600,000	$ 5,100,000
Benefit for deferred tax assets		0
Unrecognized tax benefits		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		1,900,000
Federal
Income Taxes Disclosure [Line Items]
Net operating loss (NOL) carryforwards		$ 109,700,000
Net operating loss carryforwards expiration start year		2035
Net operating loss (NOL) carryforwards indefinite		$ 87,600,000
Federal | Research and Development
Income Taxes Disclosure [Line Items]
Tax credit carryforward expiration start year		2035
Tax credit carryforward		$ 2,400,000
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		$ 1,800,000

Income Taxes - Schedule of Dome

Income Taxes - Schedule of Domestic and Foreign Components of Net Loss (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Net loss	$ (10,941)	$ (11,289)	$ (9,500)	$ (10,012)	$ (9,579)	$ (9,148)	$ (8,718)	$ (7,642)	$ (41,742)	$ (35,087)	$ (23,167)
Domestic
Operating Loss Carryforwards [Line Items]
Net loss									(41,599)	(34,181)	(23,047)
Foreign
Operating Loss Carryforwards [Line Items]
Net loss									$ (143)	$ (906)	$ (120)

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
State taxes, net of federal benefit	1.10%	0.90%	6.40%
Foreign tax rate differential	0.00%	0.20%	0.10%
Permanent differences	(2.70%)	(1.70%)	0.30%
Research and development credit	2.60%	1.90%	1.40%
Change in valuation allowance	(22.00%)	(22.30%)	(29.20%)

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Reserves and accruals	$ 1,665	$ 1,056	$ 1,009
Net operating loss carryforwards	24,824	16,986	10,985
Research and development credit carryforwards	2,938	2,177	1,194
Lease Liabilities	1,148	1,336
Gross deferred tax assets	30,575	21,555	13,188
Valuation allowance	(29,410)	(20,196)	(12,560)
Net deferred tax assets	1,165	1,359	628
Deferred tax liabilities
Property and equipment	(469)	(557)	$ (628)
Right-of-use asset	$ (696)	$ (802)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Components Of Deferred Tax Assets And Liabilities [Abstract]
Additions for prior year tax positions	$ 381
Additions for current year tax positions	487
Balance as of December 31, 2020	$ 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	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (10,941)	$ (11,289)	$ (9,500)	$ (10,012)	$ (9,579)	$ (9,148)	$ (8,718)	$ (7,642)	$ (41,742)	$ (35,087)	$ (23,167)
Denominator:
Weighted-average shares of common stock outstanding									44,004,190	19,083,826	10,264,584
Net loss per common share, basic and diluted	$ (0.22)	$ (0.23)	$ (0.22)	$ (0.30)	$ (0.50)	$ (0.48)	$ (0.46)	$ (0.40)	$ (0.95)	$ (1.84)	$ (2.26)

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	4,497,981	3,137,093	2,270,723
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	4,489,122	3,107,066	2,181,466
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	89,257

Selected Quarterly Financial _3

Selected Quarterly Financial Information (Unaudited) - Schedule of Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Operating expenses	$ 11,068	$ 11,551	$ 9,853	$ 10,478	$ 9,997	$ 9,681	$ 9,355	$ 8,309	$ 42,950	$ 37,342	$ 24,726
Net loss	$ (10,941)	$ (11,289)	$ (9,500)	$ (10,012)	$ (9,579)	$ (9,148)	$ (8,718)	$ (7,642)	$ (41,742)	$ (35,087)	$ (23,167)
Net loss per common share, basic and diluted	$ (0.22)	$ (0.23)	$ (0.22)	$ (0.30)	$ (0.50)	$ (0.48)	$ (0.46)	$ (0.40)	$ (0.95)	$ (1.84)	$ (2.26)