Turning Point Therapeutics (TPTX) 10-K 28 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 22, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	TPTX
Entity Registrant Name	Turning Point Therapeutics, Inc.
Entity Central Index Key	0001595893
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		49,622,698
Entity File Number	001-38871
Entity Tax Identification Number	46-3826166
Entity Address, Address Line One	10628 Science Center Drive
Entity Address, Address Line Two	Ste. 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	926-5251
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 3,673
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant’s definitive proxy statement to be filed with the Securities and Exchange Commission (SEC) subsequent to the date hereof pursuant to Regulation 14A in connection with the Registrant's 2022 Annual Meeting of Stockholders, are incorporated by reference into Part III of this Annual Report on Form 10-K. Such proxy statement will be filed with the SEC not later than 120 days after the conclusion of the Registrant's fiscal year ended December 31, 2021.
Auditor Name	Ernst & Young LLP
Auditor Location	San Diego, California
Auditor Firm ID	42

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 427,879	$ 554,101
Marketable securities	553,703	568,407
Prepaid and other current assets	10,880	8,171
Total current assets	992,462	1,130,679
Property and equipment, net	3,822	2,604
Right-of-use lease assets	5,158	3,357
Other assets	2,021	73
Total assets	1,003,463	1,136,713
Current liabilities:
Accounts payable	5,656	5,225
Accrued expenses and other current liabilities	25,300	9,183
Accrued compensation	12,503	8,588
Current portion of operating lease liabilities	3,630	1,396
Total current liabilities	47,089	24,392
Operating lease liabilities, long-term	1,949	2,423
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at December 31, 2021 and 2020, zero shares outstanding at December 31, 2021 and 2020
Common stock, $0.0001 par value; 200,000,000 shares authorized at December 31, 2021 and 2020; 49,582,638 and 48,678,540 shares issued and outstanding at December 31, 2021 and 2020, respectively	5	5
Additional paid-in capital	1,472,421	1,389,860
Accumulated other comprehensive (loss) income	(1,274)	209
Accumulated deficit	(516,727)	(280,176)
Total stockholders' equity	954,425	1,109,898
Total liabilities and stockholders’ equity	$ 1,003,463	$ 1,136,713

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	49,582,638	48,678,540
Common stock, shares outstanding	49,582,638	48,678,540

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 30,829	$ 25,000
Operating expenses:
Research and development	192,979	113,411	$ 57,943
General and administrative	75,850	73,425	19,781
Total operating expenses	268,829	186,836	77,724
Loss from operations	(238,000)	(161,836)	(77,724)
Other income, net	1,449	4,544	5,593
Net loss	(236,551)	(157,292)	(72,131)
Unrealized (loss) gain on marketable securities, net of tax	(1,483)	(62)	271
Comprehensive loss	$ (238,034)	$ (157,354)	$ (71,860)
Net loss per share, basic and diluted	$ (4.80)	$ (3.85)	$ (2.99)
Weighted-average common shares outstanding, basic and diluted	49,264,549	40,843,782	24,124,924

Statements of Changes in Conver

Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2018		$ 145,916	$ 1
Balance, Shares at Dec. 31, 2018		65,423,901
Balance at Dec. 31, 2018	$ (48,406)			$ 2,346		$ (50,753)
Balance, Shares at Dec. 31, 2018			3,411,516
Issuance of common stock in connection with a public offerings, net of underwriting discounts, commissions, and offering costs	364,656		$ 1	364,655
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs, Shares			15,137,500
Conversion of convertible preferred stock into common stock	145,916	$ (145,916)	$ 2	145,914
Conversion of convertible preferred stock into common stock, Shares		(65,423,901)	16,993,194
Option exercises	1,008			1,008
Option exercises, Shares			362,275
Shares issued under employee stock purchase plan	331			331
Shares issued under employee stock purchase plan, Shares			10,634
Stock-based compensation expense	12,706			12,706
Net loss	(72,131)					(72,131)
Other comprehensive loss	271				$ 271
Balance at Dec. 31, 2019	404,351		$ 4	526,960	271	(122,884)
Balance, Shares at Dec. 31, 2019			35,915,119
Issuance of common stock in connection with a public offerings, net of underwriting discounts, commissions, and offering costs	785,469		$ 1	785,468
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs, Shares			11,516,524
Option exercises	12,237			12,237
Option exercises, Shares			1,218,410
Shares issued under employee stock purchase plan	1,032			1,032
Shares issued under employee stock purchase plan, Shares			28,487
Stock-based compensation expense	64,163			64,163
Net loss	(157,292)					(157,292)
Other comprehensive loss	(62)				(62)
Balance at Dec. 31, 2020	$ 1,109,898		$ 5	1,389,860	209	(280,176)
Balance, Shares at Dec. 31, 2020	48,678,540		48,678,540
Option exercises	$ 22,181			22,181
Option exercises, Shares	850,952		856,327
Shares issued under employee stock purchase plan	$ 1,823			1,823
Shares issued under employee stock purchase plan, Shares			47,771
Stock-based compensation expense	58,557			58,557
Net loss	(236,551)					(236,551)
Other comprehensive loss	(1,483)				(1,483)
Balance at Dec. 31, 2021	$ 954,425		$ 5	$ 1,472,421	$ (1,274)	$ (516,727)
Balance, Shares at Dec. 31, 2021	49,582,638		49,582,638

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net loss	$ (236,551)	$ (157,292)	$ (72,131)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	58,557	64,163	12,706
Depreciation	1,209	875	492
Accretion of premium (discount) on marketable securities	5,333	1,261	(1,357)
Amortization of right-of-use operating lease asset	2,758	1,518	1,087
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,855)	(2,374)	(5,229)
Accounts payable	429	3,549	903
Accrued expenses and other current liabilities	13,319	3,655	522
Accrued compensation	3,916	1,852	5,323
Net cash used in operating activities	(153,885)	(82,793)	(57,684)
Investing activities
Purchases of marketable securities	(439,230)	(618,973)	(432,173)
Sales and maturities of marketable securities	447,119	410,205	72,838
Purchases of property and equipment	(2,427)	(1,264)	(1,744)
Net cash provided by (used in) investing activities	5,462	(210,032)	(361,079)
Financing activities
Proceeds from issuance of common stock in initial public offering, net			175,151
Proceeds from issuance of common stock in public offerings, net of offering costs		785,469	189,505
Proceeds from issuance of common stock under equity incentive plans	24,004	13,269	1,339
Net cash provided by financing activities	24,004	798,738	365,995
Net (decrease) increase in cash, cash equivalents and restricted cash	(124,419)	505,913	(52,768)
Cash and cash equivalents and restricted cash at the beginning of period	554,174	48,261	101,029
Cash and cash equivalents and restricted cash at the end of period	429,755	554,174	48,261
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1	$ 1	1
Supplemental disclosure of non-cash investing and financing information:
Purchases of property and equipment in accounts payable			490
Operating lease liabilities arising from obtaining right-of-use assets	$ 4,007		$ 5,554

Organization

Organization	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Formation and Business of the Company	1. Organization Description of Business Turning Point Therapeutics, Inc. (the Company) was organized in October 2013, and commenced operations in 2014. The Company is a clinical-stage precision oncology biopharmaceutical company designing and developing novel therapies that target genetic drivers of cancer to improve the lives of patients. The Company’s principal operations are in the United States and the Company operates in one segment, with its headquarters in San Diego, California. The Company’s primary activities since inception have been to build infrastructure, conduct research and development, including clinical trials, perform business and financial planning, and raise capital. Liquidity The Company’s activities are subject to significant risks and uncertainties, including concentration on the Company’s lead development program, which has significant competition from cancer therapies in development by other companies or already approved for sale by the U.S. Food and Drug Administration. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Drug candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. The COVID-19 pandemic continues to rapidly evolve and has already resulted in a significant disruption of global financial markets. The Company’s ability to raise additional capital may be adversely impacted by potential worsening global economic conditions and further disruptions to, and volatility in, the credit and financial markets in the United States and worldwide resulting from the pandemic. If such further disruption occurs, the Company could experience an inability to access additional capital. The Company determined that there are no conditions or events that raise substantial doubt about its ability to continue as a going concern for a period of at least twelve months from the date of issuance of these financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). Use of Estimates The preparation of the Company's financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. The most significant estimates in the Company’s financial statements relate to determining the standalone selling prices ( SSP) of performance obligations associated with license and collaboration arrangements, accrued research and development expenses and stock-based compensation expenses . The Company bases these estimates on historical experience, knowledge of current events and actions it may undertake in the future, and on various other assumptions that are believed to be reasonable. A ctual results may differ materially from these estimates and assumptions. Although the impact of the COVID-19 pandemic to the Company’s business and operating results presents additional uncertainty, the Company continues to use the best information available to update its critical accounting estimates. Revenue Recognition The Company recognizes revenue in accordance with Accounting Standards Codification (ASC) Topic 606, Revenue From Contracts With Customers (ASC 606). Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. The Company assesses the goods or services promised within each contract and determines those that are performance obligations. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations. The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. The transaction price is then determined and allocated to the identified performance obligations in proportion to their SSP on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment. If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less to be cash equivalents. As of December 31, 2021 and 2020, cash equivale nts consisted of checking, savings, and money market balances. The Company places its cash and cash equivalents with high credit quality financial institutions. All of the Company’s cash and cash equivalent balances are maintained at two financial institutions domiciled in the United States. The following table presents a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets to the amounts shown in the statements of cash flows (in thousands): Year Ended December 31, 2021 2020 2019 Cash and cash equivalents $ 427,879 $ 554,101 $ 48,188 Restricted cash included in other assets 1,876 73 73 Total cash, cash equivalents and restricted cash $ 429,755 $ 554,174 $ 48,261 Marketable Securities The Company classifies all marketable securities as available for sale, as the sale of such securities may be required prior to maturity. These marketable securities are carried at fair value, with unrealized gains and losses reported as accumulated other comprehensive income (loss) until realized. The cost of debt securities is adjusted for accretion of premiums and amortization of discounts to maturity. Such amortization and accretion, as well as interest and dividends, are included in other income, net. Realized gains and losses from the sale of available for sale securities, if any, are determined on a specific identification basis and are also included in other income, net. The Company’s marketable securities are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary. Allowance for Credit Losses The Company segments its portfolio based on the underlying risk profiles of their current securities being held. The Company regularly reviews the securities in an unrealized loss position and evaluates the current expected credit loss by considering factors such as historical experience, market data, issuer-specific factors, current and expected future economic conditions. As of December 31, 2021, the Company did no t record an allowance for credit loss related to its investment portfolio. Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should maximize the use of observable inputs and minimize the use of unobservable inputs. The Company determines the fair value of financial assets and liabilities using three levels of inputs as follows: Level 1 — Observable inputs such as quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 — Inputs (other than quoted market prices included in Level 1) that are either directly or indirectly observable, 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 instrument’s anticipated life; and Level 3 — Unobservable inputs for assets or liabilities and include little or no market activity. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Concentration of Credit Risk Substantially all of the Company’s cash and cash equivalents and marketable securities are held at two financial institutions. Due to the financial strength of the depository institutions, the Company believes these financial institutions represent minimal credit risk. Cash amounts held at financial institutions are insured by the Federal Deposit Insurance Corporation (FDIC) up to $ 250,000 . At December 31, 2021 , cash and cash equivalents and marketable securities totaling $ 981.3 million are either not subject to FDIC insurance, or exceed the FDIC insured limit. The Company’s cash and cash equivalents and marketable securities are invested in short term, high grade securities, and as a result, the Company believes represent a minimal credit risk . Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful life of the assets, which ranges between three to seven years . R epairs and maintenance costs are charged to expense as incurred. Tenant improvements are stated at cost and depreciated over the shorter of the estimated useful life or the remaining life of the lease at the time the asset is placed into service. Impairment of Long-Lived Assets The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its respective fair value. The Company did no t recognize any impairment losses during the years ended December 31, 2021, 2020 and 2019. Leases The Company determines whether a contract is, or contains, a lease at inception. Right-of-use (ROU) assets represent the Company’s right to use an underlying asset during the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at lease commencement based upon the estimated present value of unpaid lease payments over the lease term using the Company’s incremental borrowing rate applicable to the underlying asset unless the implicit rate is readily determinable. The Company's incremental borrowing rate is determined based on the estimated rate of interest for collateralized borrowing over a similar term as the associated lease. ROU assets also include any lease payme nts made at or before lease commencement and any initial direct costs incurred, and exclude any lease incentives received. The Company determines the lease term as the non-cancellable period of the lease, and may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Leases with a term of 12 months or less are not recognized on the balance sheets. Patent Costs Legal and professional costs incurred by the Company to maintain its patent rights have been expensed as part of general and administrative expenses. As of December 31, 2021 and 2020, the Company has determined that these expenses have not met the criteria to be capitalized. General and Administrative Expenses General and administrative expenses consist primarily of salaries and employee-related costs, including stock-based compensation, for personnel in executive, finance, legal, commercial and other administrative functions. General and administrative expenses also include professional fees for legal, patent, accounting and tax-related services, insurance costs, recruiting costs, travel expenses and facility-related costs. Research and Development Expenses and Accruals Research and development costs are expensed as incurred. These costs consist primarily of employee-related expenses, including salaries and related benefits, travel and stock-based compensation for employees engaged in research and development functions; expenses incurred in connection with the preclinial and clinical development of drug candidates, including expenses incurred under the agreements with the CROs; the cost of consultants and contract manufacturing organizations that manufacture drug products for use in the preclinical studies and clinical trials; and facilities, depreciation and other expenses, including allocated expenses for rent and maintenance of facilities, insurance and supplies. The Company accrues the expenses for its clinical trial activities performed by third-party vendors, including CROs and clinical sites, based upon estimates of the proportion of work completed over the life of the individual clinical trial and patient enrollment rates in accordance with associated agreements. The Company determines the estimates by reviewing contracts and purchase orders, and through discussions with internal clinical personnel and external service providers as to the progress or stage of completion of trials or services pursuant to the contracts with the service providers and agreed-upon fees to be paid to identify services that have been performed on its behalf and estimate the level of service performed and the associated cost incurred for which it has not yet been invoiced. The Company records the estimated costs for research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued expenses and other current liabilities in the balance sheet and within research and development expense in the statement of operations and comprehensive loss. As actual costs become known, the Company will adjust its accrued expenses and other current liabilities. Payments for goods and services that will be used in future research and development activities are recorded as prepaid and other current assets and recognized as expense in the period when the goods are consumed or services are performed. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the statement of operations in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (i) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability. Stock-Based Compensation Expense The Company measures and recognizes compensation expense for share-based awards based on the fair value of the award as measured at grant date. The fair value of restricted stock units (RSUs) and performance stock units (PSUs) granted is based on the Company’s closing stock price on the grant date. The fair value of stock options and employee stock purchase plan awards is estimated using the Black-Scholes option-pricing model. The determination of the estimated fair value of stock-based awards utilizing the Black-Scholes model is affected by the Company’s stock price and a number of assumptions, including the expected volatility of the Company’s stock price, the option's expected life, risk-free interest rate and expected dividend yield. Expected Term — The Company uses the simplified method for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years). Expected Volatility — Due to the Company’s limited operating history and a lack of company specific historical and implied volatility data, the Company estimates expected volatility based on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. Risk-Free Interest Rate — The risk-free rate assumption is based on the U.S. Treasury instruments with maturities similar to the expected term of the stock options. Expected Dividend Yield — The Company has not issued any dividends and does not expect to issue dividends over the life of the options. As a result, the Company has estimated the dividend yield to be zero . The estimated fair value of equity awards granted to employees and non-employee service providers are expensed over the requisite service period (generally the vesting term) on a straight-line basis , net of actual forfeitures when they occur . Net Loss Per Share Basic net loss per share is computed by dividing the net loss available to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share assumes the conversion, exercise or issuance of all potential common stock equivalents, unless the effect of inclusion would be anti-dilutive. For purposes of this calculation, common stock equivalents include the Company’s stock options, RSUs and PSUs. The Company excluded stock options to purchase common stock, RSUs and PSUs from the number of shares used to calculate diluted shares outstanding because the inclusion of these potentially dilutive securities would have been antidilutive . Historical outstanding anti-dilutive securities not included in the diluted net loss per share calculation include the following: Year Ended December 31, 2021 2020 2019 Common stock options 5,418,467 5,790,713 5,254,269 RSUs 358,760 21,500 — PSUs 204,759 — — Total 5,981,986 5,812,213 5,254,269

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Marketable Securities	3. Marketable Securities T he Company invests its excess cash in marketable securities, including debt instruments of financial institutions, corporations with investment grade credit ratings, commercial paper and government agencies. At December 31, 2021, marketable securities consisted of the following (in thousands): Maturity Amortized Unrealized in Years Cost Gains Losses Fair Value U.S. Treasuries 2 years or less $ 305,763 $ 1 $ ( 1,006 ) $ 304,758 U.S. Government agency securities 2 years or less 151,047 — ( 180 ) 150,867 Non-U.S. Government agency securities 2 years or less 23,787 — ( 49 ) 23,738 Corporate debt securities 2 years or less 74,391 5 ( 56 ) 74,340 Total marketable securities $ 554,988 $ 6 $ ( 1,291 ) $ 553,703 At December 31, 2020, marketable securities consisted of the following (in thousands): Maturity Amortized Unrealized in Years Cost Gains Losses Fair Value U.S. Treasuries 2 years or less $ 113,662 $ 19 $ ( 1 ) $ 113,680 U.S. Government agency securities 2 years or less 173,583 100 — 173,683 Corporate debt securities 2 years or less 169,189 103 ( 27 ) 169,265 Commercial paper Less than 1 111,779 — — 111,779 Total marketable securities $ 568,213 $ 222 $ ( 28 ) $ 568,407 The Company segments its portfolio based on the underlying risk profiles of their current securities being held. The Company regularly reviews the securities in an unrealized loss position and evaluates the current expected credit loss by considering factors such as historical experience, market data, issuer-specific factors, current and expected future economic conditions. As of December 31, 2021, the Company did not record an allowance for credit loss related to its investment portfolio.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company measures fair value based on the prices that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The carrying amounts of certain of the Company’s financial instruments, including cash and cash equivalents and marketable securities, prepaid and other current assets, accounts payable, and accrued liabilities, approximate fair value due to the short-term nature of these items. The Company’s financial assets subject to fair value measurements on a recurring basis and the level of inputs used for such measurements were as follows (in thousands): Fair Value Measurements at December 31, 2021 Using: Level 1 Level 2 Level 3 Total Money market funds $ 232,813 $ — $ — $ 232,813 U.S. Treasuries 304,758 — — 304,758 U.S. Government agency securities — 150,867 — 150,867 Non-U.S. Government securities — 23,738 — 23,738 Corporate debt securities — 77,400 — 77,400 Commercial paper — 191,130 — 191,130 Total cash equivalents and marketable securities $ 537,571 $ 443,135 $ — $ 980,706 Fair Value Measurements at December 31, 2020 Using: Level 1 Level 2 Level 3 Total Money market funds $ 299,571 $ — $ — $ 299,571 U.S. Treasuries 113,680 — — 113,680 U.S. Government agency securities — 173,683 — 173,683 Corporate debt securities — 180,718 — 180,718 Commercial paper — 354,223 — 354,223 Total cash equivalents and marketable securities $ 413,251 $ 708,624 $ — $ 1,121,875

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, December 31, 2021 2020 Laboratory equipment $ 3,368 $ 1,629 Computer equipment and software 1,283 956 Tenant improvements 1,468 1,108 Furniture and fixtures 358 357 Property and equipment 6,477 4,050 Less: accumulated depreciation ( 2,655 ) ( 1,446 ) Property and equipment, net $ 3,822 $ 2,604 Depreciation expense for the years ended December 31, 2021, 2020 and 2019 wa s $ 1.2 mil lion, $ 0.9 million and $ 0.5 million, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2021
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, December 31, 2021 2020 Accrued research and development expenses $ 23,497 $ 8,457 Accrued general and administrative expenses 1,655 682 Other current liabilities 148 44 Total $ 25,300 $ 9,183

Zai Repotrectinib Agreement

Zai Repotrectinib Agreement	12 Months Ended
	Dec. 31, 2021
Research And Development [Abstract]
Zai Repotrectinib Agreement	7. Zai License Agreements Zai Repotrectinib Agreement In July 2020, the Company entered into a license agreement (the Zai Repotrectinib Agreement) with Zai Lab (Shanghai) Co., Ltd. (Zai), pursuant to which the Company granted Zai exclusive rights to develop and commercialize products containing the Company’s drug candidate, repotrectinib (the Repotrectinib Products), in Mainland China, Hong Kong, Macau and Taiwan (collectively, the Zai Territory or Greater China). The Company retains exclusive rights to, among other things, develop, manufacture and commercialize the Repotrectinib Products outside the Zai Territory. The Company will supply or have supplied to Zai the Repotrectinib Products for use in the Zai Territory pursuant to a supply agreement for agreed upon consideration, except that Zai has the right, at its election, to package and label the Repotrectinib Products in or outside the Zai Territory for use in the Zai Territory . Pursuant to the terms of the Zai Repotrectinib Agreement, the Company received an upfront cash payment of $ 25.0 million in 2020 and is eligible to receive up to $ 151.0 million in development and sales milestone payments, consisting of up to $ 46.0 million of development milestones and up to $ 105.0 million of sales milestones. In addition, during the term of the Zai Repotrectinib Agreement, Zai is obligated to pay the Company tiered percentage royalties ranging from mid-to-high teens on annual net sales of the Repotrectinib Products in the Zai Territory, subject to adjustments in specified circumstances . Zai is responsible for conducting the development and commercialization activities in the Zai Territory related to the Repotrectinib Products at Zai’s own expense, subject to limited exceptions pursuant to which the Company may be responsible for the cost. The Company is responsible for global clinical studies of the Repotrectinib Products, including the portions that may be conducted in the Zai Territory, at the Company’s expense, except that Zai will participate in global clinical studies of the Repotrectinib Products through clinical trial sites in the Zai Territory as agreed as of the effective date of the Zai Repotrectinib Agreement and may, at Zai’s election, participate in future global clinical studies of the Repotrectinib Products through clinical trial sites in the Zai Territory, in each case at Zai’s expense. The Zai Repotrectinib Agreement will continue in effect until expiration of the last royalty term for a Repotrectinib Product in any region in the Zai Territory, where the royalty term for a Repotrectinib Product in a region continues until the later of (i) the date of the last-to-expire valid claim within Company’s patent rights that covers the Repotrectinib Product in such region in the Zai Territory; (ii) the expiry of the regulatory exclusivity for such Repotrectinib Product in such region; or (iii) the close of business of the day that is exactly 10 years after the date of the first commercial sale of such Repotrectinib Product in such region. Subject to the terms of the Zai Repotrectinib Agreement, Zai may terminate the Zai Repotrectinib Agreement for convenience by providing written notice to the Company, which termination will be effective following a prescribed notice period. In addition, the Company may terminate the Zai Repotrectinib Agreement under specified circumstances if Zai or certain other parties challenge the Company’s patent rights. Either party may terminate the Zai Repotrectinib Agreement for the other party’s uncured material breach of the Zai Repotrectinib Agreement, with a customary notice and cure period, for the other party’s insolvency or if the other party acquires a third party and the acquired party is engaged in activities with a competing product that is not divested or discontinued within a specified period. After termination (but not natural expiration), other than certain terminations by Zai for cause, the Company is entitled to retain a worldwide and perpetual license from Zai to exploit the Repotrectinib Products. Revenue Recognition The Company determined that two performance obligations existed: (1) the exclusive license, bundled with the associated know-how and (2) the Company's initial obligation to supply repotrectinib for clinical development in the Zai Territory. The total transaction price of $ 25.7 million was allocated to the performance obligations on the basis of the relative stand-alone selling price estimated for each performance obligation. In estimating the stand-alone selling price for each performance obligation, the Company developed assumptions that require judgment and included forecasted revenues, expected development timelines, discount rates, probabilities of technical and regulatory success and costs for manufacturing clinical supplies. The Company delivered the license and technical know-how to Zai in the third quarter of 2020 to satisfy this performance obligation, and accordingly the Company recognized license revenue of $ 25.0 million in the third quarter of 2020. The $ 0.7 million in consideration allocated to the clinical supply performance obligation was recognized when clinical trial material was shipped by the Company and Zai obtained control of the goods upon delivery, over the period of the obligation. During the year ended December 31, 2021, the Company recogn ized $ 0.8 million of revenue associated with the clinical supply performance obligation. The Company didn’t recognize any revenue associated with the clinical supply performance obligation during the year ended December 31, 2020. During the year ended December 31, 2021, the Company recognized $ 5.0 million of revenue upon the achievement of certain development milestones. The upfront payment received in 2020 and the development milestone payments received in 2021 were subject to foreign tax withholdings, which were recorded as general and administrative expense in the statements of operations and comprehensive loss. The Company assessed and determined that there is no significant financing component associated with the Zai Repotrectinib Agreement. Zai Elzovantinib Agreement On January 10, 2021, the Company entered into a license agreement with Zai, which was amended on March 31, 2021 (the Zai Elzovantinib Agreement), pursuant to which the Company granted Zai exclusive rights to develop and commercialize products containing the Company’s drug candidate, Elzovantinib (the Elzovantinib Products), in the Zai Territory. The Company retains exclusive rights to, among other things, develop, manufacture and commercialize the Elzovantinib Products outside the Zai Territory. Pursuant to the terms of the Zai Elzovantinib Agreement, the Company received an upfront cash payment of $ 25.0 million in the first quarter of 2021 and is eligible to receive up to $ 336.0 million in development and sales milestone payments, consisting of up to $ 121.0 million of development milestones and up to $ 215.0 million of sales milestones. In addition, during the term of the Zai Elzovantinib Agreement, Zai is obligated to pay the Company tiered percentage royalties ranging from mid-teens to low twenties on annual net sales of the Elzovantinib Products in the Zai Territory, subject to adjustments in specified circumstances . Zai is responsible for conducting the development and commercialization activities in the Zai Territory related to the Elzovantinib Products at Zai’s own expense, subject to limited exceptions pursuant to which the Company may be responsible for the cost. The Company is responsible for global clinical studies of the Elzovantinib Products, including the portions that may be conducted in the Zai Territory, at the Company’s expense, except that Zai will participate in global clinical studies of the Elzovantinib Products through clinical trial sites in the Zai Territory as agreed as of the effective date of the Zai Elzovantinib Agreement and may, at Zai’s election subject to specified exceptions, participate in future global clinical studies of the Elzovantinib Products through clinical trial sites in the Zai Territory, in each case at Zai’s expense. The Zai Elzovantinib Agreement will continue in effect until expiration of the last royalty term for a Elzovantinib Product in any region in the Zai Territory, where the royalty term for a Elzovantinib Product in a region continues until the later of (i) the expiry of the last-to-expire valid claim within Company’s patent rights that covers the Elzovantinib Product in such region in the Zai Territory; (ii) the expiry of the regulatory exclusivity for such Elzovantinib Product in such region; or (iii) the close of business of the day that is exactly 10 years after the date of the first commercial sale of such Elzovantinib Product in such region. Subject to the terms of the Zai Elzovantinib Agreement, Zai may terminate the Zai Elzovantinib Agreement for convenience by providing written notice to the Company, which termination will be effective following a prescribed notice period. In addition, the Company may terminate the Zai Elzovantinib Agreement under specified circumstances if Zai or certain other parties challenge the Company’s patent rights. Either party may terminate the Zai Elzovantinib Agreement for the other party’s uncured material breach of the Zai Elzovantinib Agreement, with a customary notice and cure period, for the other party’s insolvency or if the other party acquires a third party and the acquired party is engaged in activities with a competing product that is not divested or discontinued within a specified period. After termination (but not natural expiration), other than certain terminations by Zai for cause, the Company is entitled to retain a worldwide and perpetual license from Zai to exploit the Elzovantinib Products. Revenue Recognition The Company determined that two performance obligations existed: (1) the exclusive license, bundled with the associated know-how and (2) the Company’s initial obligation to supply e lzovantinib for clinical development in the Zai Territory. The total transaction price of $ 25.9 million was allocated to the performance obligations on the basis of the relative stand-alone selling price estimated for each performance obligation. In estimating the stand-alone selling price for each performance obligation, the Company developed assumptions that require judgment and included forecasted revenues, expected development timelines, discount rates, probabilities of technical and regulatory success and costs for manufacturing clinical supplies. The Company delivered the license and technical know-how to Zai in the first quarter of 2021 to satisfy this performance obligation, and accordingly the Company recognized license revenue of $ 25.0 million in the first quarter of 2021. The upfront payment received was subject to foreign tax withholdings, which was recorded as general and administrative expense in the statements of operations and comprehensive loss. The $ 0.9 million in consideration allocable to the clinical supply performance obligation will be recognized when clinical trial material has been shipped by the Company and Zai obtains control of the goods upon delivery, over the period of the obligation. As of December 31, 2021, the Company has no t recognized any revenue associated with the clinical supply performance obligation under the Zai Elzovantinib Agreement. The Company assessed and determined that there is no significant financing component associated with the Zai Elzovantinib Agreement.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Operating Leases The Company leases office and laboratory space under lease agreements that expire in June 2023 . One of the leases contains an option to extend the lease for five years , which was not included in the determination of the lease term as it was not reasonably certain that the Company would exercise this option. As of December 31, 2021, the Company recorded $ 5.2 million as ROU assets, $ 3.6 million as current operating lease liabilities, and $ 2 .0 million as non-current operating lease liabilities on its balance sheet. As of December 31, 2020, the Company recorded $ 3.4 million as ROU assets, $ 1.4 million as current operating lease liabilities and $ 2.4 million as non-current operating lease liabilities on its balance sheet. Operating lease costs for the years ended December 31, 2021, 2020 and 2019 were $ 2.8 million, $ 1.5 million and $ 1.1 million, respectively. Variable lease costs representing the Company's share of the operating expenses and utility costs of the leased properties were $ 1.4 million, $ 1.2 million and $ 0.7 million for the years ended December 31, 2021, 2020 and 2019, respectively. Cash paid for amounts included in the measurement of operating lease liabilities was $ 2.2 million, $ 1.6 million and $ 1.2 million for the years ended December 31, 2021, 2020 and 2019, respectively. The Company ’ s operating leases had a weighted-average remaining lease term of 1.5 years and 2.6 years, and a weighted-average discount rate of 7.0 % and 8.5 %, as of December 31, 2021 and 2020, respectively. Maturities of operating lease liabilities as of December 31, 2021 were as follows (in thousands) : 2022 $ 3,898 2023 1,989 Total future minimum lease payments 5,887 Less: amounts representing interest ( 308 ) Total lease liability $ 5,579 Remaining lease term 1.5 years In May 2021, the Company entered into a lease agreement with HCP Callan Road, LLC for office and laboratory space for the Company’s future corporate headquarters, delivered in two phases. The term of the lease is approximately 11 years and nine months with an option by the Company to extend for an additional five years , and is currently expected to commence in May 2023 . The lease term has an initial abatement period with respect to each phase and the initial base rent payable upon the Company's occupancy of both phases will be approximately $ 1.0 million per month following the end of the abatement period for each phase, which amount will increase by 3 % per year over the lease term. The Company is also responsible for the payment of its share of the operating expenses for the building. The landlord will provide the Company with a tenant improvement allowance of up to $ 220 per square foot. As of December 31, 2021, total aggregate future lease commitments under the lease were approximately $ 165.9 million. In connection with the lease, the Company is required to maintain a letter of credit for the benefit of the landlord in the amount of $ 1.8 million, which was delivered in May 2021 and is included in other assets in the Company ’ s balance sheets.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity At the Market Offering In August 2020, the Company entered into an Open Market Sale Agreement SM with Jefferies LLC (ATM facility), under which the Company may offer and sell, from time to time, at its sole discretion, up to $ 250.0 million shares of the Company’s common stock. As of December 31, 2021, the Company had not yet sold any shares of common stock under the ATM facility. 2019 Equity Incentive Plan T he Company’s 2019 Equity Incentive Plan (the Plan) provides for the grant of stock options, restricted stock and other equity awards of the Company’s common stock to employees, officers, consultants and directors. In addition, the number of shares of common stock available for issuance under the Plan will be automatically increased on the first day of each calendar year through January 1, 2029 , by an amount equal to 4 % of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. On January 1, 2021, the Company added 1,947,141 shares to the Plan. As of December 31, 2021, the Plan had 3,215,165 total shares available for issuance. Stock Options Stock options expire within a period of not more than ten years from the date of grant. Initial option grants to employees typically vest 25 % on the first anniversary of the original vesting date and monthly thereafter over a three-year period and expire three months after employee termination. Subsequent option grants to employees and grants to non-employees typically vest monthly over a four-year period. The following table summarizes stock option activity under the Plan for the year ended December 31, 2021: Outstanding Weighted Weighted Aggregate Balance as of January 1, 2021 5,790,713 $ 34.97 8.4 $ 503,114 Options granted 1,198,486 $ 97.44 Options exercised ( 850,952 ) $ 26.07 Options forfeited or cancelled ( 719,780 ) $ 57.64 Balance as of December 31, 2021 5,418,467 $ 47.17 7.5 $ 91,794 Options vested and exercisable as of December 31, 2021 2,698,520 $ 29.18 6.7 $ 70,798 The weighted-average grant-date fair value of o ptions granted to employees was $ 66.72 , $ 46.00 and $ 21.66 for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, total unrecognized compensation expense related to unvested options was $ 114.6 million, which is expected to be recognized over a weighted average term of 2.30 years . The total intrinsic value of stock options exercised in 2021, 2020 and 2019 was $ 59.7 million, $ 113.8 million and $ 12.7 million, respectively. The fair values of the stock options granted during 2021, 2020 and 2019 was estimated at the date of grant using the Black-Scholes option-pricing model with the following assumptions: Year Ended December 31, 2021 2020 2019 Risk-free interest rate 0.88 % 1.15 % 2.13 % Volatility 80.1 % 79.5 % 79.8 % Expected term (in years) 6.06 6.07 6.05 Dividend yield — — — Restricted Stock Units The following table summarizes restricted stock unit activity under the Plan for the year ended December 31, 2021: Restricted Stock Units Outstanding Weighted Aggregate Balance as of January 1, 2021 21,500 $ 59.94 $ 2,620 Granted 373,982 $ 93.44 Vested ( 5,375 ) $ 59.94 Forfeited ( 31,347 ) $ 125.93 Outstanding as of December 31, 2021 358,760 $ 89.09 $ 17,113 As of December 31, 2021, total unrecognized compensation related to RSUs granted was $ 26.9 million, which is expected to be recognized over a weighted-average period of approximately 3.10 years. The total fair value of RSUs vested in 2021 was $ 0.4 million. There were no RSUs vested in 2020 and 2019. Performance Stock Units The Company grants PSUs that vest based on the achievement of certain predefined Company-specific performance criteria. The fair value of PSUs is estimated based on the closing price of the Company’s common stock on the date of grant. The Company recognizes expense in proportion to the number of PSUs that are deemed probable of vesting, based on the Company’s evaluation of the respective performance-based criteria, at each reporting date. The following table summarizes performance stock unit activity under the Plan for the year ended December 31, 2021: Performance Stock Units Outstanding Weighted Aggregate Balance as of January 1, 2021 — $ — $ — Granted 241,365 $ 122.84 Vested — $ — Forfeited ( 36,606 ) $ 136.82 Outstanding as of December 31, 2021 204,759 $ 120.34 $ 9,767 As of December 31, 2021, the Company does not estimate that the achievement of any performance-based criteria is probable. During the year ended December 31, 2021, there were no PSUs vested and the Company did no t recognize any share-based compensation expense related to the PSUs. 2019 Employee Stock Purchase Plan In April 2019, the Company’s board of directors and stockholders approved and adopted the 2019 Employee Stock Purchase Plan (the ESPP). The ESPP became effective immediately prior to the date of the underwriting agreement related to the Company’ s initial public offering. The ESPP permits eligible employees who elect to participate in an offering under the ESPP to have up to 15 % of their eligible earnings withheld, subject to certain limitations, to purchase shares of common stock pursuant to the ESPP. The price of common stock purchased under the ESPP is equal to 85 percent of the lower of the fair market value of the common stock at the commencement date of each offering period or the relevant date of purchase. Each offering period is 24 months, with new offering periods commencing every six months on the dates of June 11 and December 11 of each year. Each offering period consists of four six month purchase periods (each a Purchase Period) during which payroll deductions of the participants are accumulated under the ESPP. The last business day of each Purchase Period is referred to as the “Purchase Date.” Purchase Dates are every six months on the dates of June 10 and December 10 of each year. As of December 31, 2021, 202,046 shares of co mmon stock were available for purchase under the ESPP. As of December 31, 2021, unrecognized compensation expense related to the ESPP was $ 4.2 million. The assumptions used for the years ended December 31, 2021, 2020 and 2019 and the resulting estimates of weighted-average fair value per share for stock purchased under the ESPP were as follows : Year Ended December 31, 2021 2020 2019 Risk-free interest rate 0.04 - 0.66 % 0.08 – 0.19 % 1.55 - 2.13 % Volatility 69.2 - 80.1 % 79.7 - 91.6 % 70.6 - 76.2 % Expected term (in years) 0.50 - 2.00 0.50 - 2.00 0.50 - 2.00 Dividend yield — — — Modifications to Outstanding Equity Awards On March 30, 2021, Sheila Gujrathi, M.D. and Jacob M. Chacko, M.D. resigned from the Board of Directors (the Board) of the Company, effective immediately, to focus on other endeavors. Dr. Gujrathi also resigned from her position as Chair of the Board and Dr. Chacko resigned from each committee of the Board for which he was a member. In connection with the foregoing, the Board approved an amendment to the option awards held by Drs. Gujrathi and Chacko to provide that (i) all shares subject to such option awards are fully vested and exercisable as of the resignation date and (ii) the post-resignation exercise period shall be extended to September 30, 2022 . The Company determined that the modification to extend the term of vested stock options was a Type I modification pursuant to ASC 718, Compensation – Stock Compensation (ASC 718). The acceleration of the vesting of the unvested stock options was deemed a Type III modification pursuant to ASC 718, because without Board approval, these stock options would have been forfeited on the date of resignation. As a result of these modifications the Company recognized $ 5.6 million in stock-based compensation expense in the first quarter of 2021 in general and administrative expenses in the statements of operations and comprehensive loss. On January 9, 2020, the Company entered into a Transition Separation and Consulting Agreement (the Transition Agreement) with the Company’s former Chief Scientific Officer (CSO), Dr. Jingrong Jean Cui. In connection with the Transition Agreement, Dr. Cui resigned from her position as CSO effective January 31, 2020 and thereafter agreed to serve as a consultant to the Company on an as needed basis until June 30, 2020 . In accordance with the terms of the Transition Agreement, the Company recorded $ 1.2 million in expense during the first quarter of 2020 representing the cash severance that was paid to Dr. Cui during 2020. The terms of the Transition Agreement allowed Dr. Cui to continue to vest her outstanding options through to the end of the consulting period on June 30, 2020. At the termination of the consulting period, Dr. Cui immediately received an additional eighteen months vesting of her stock options. In addition, the Company extended Dr. Cui’s period to exercise her vested stock options from 90 days to 12 months from the date of the termination of the consulting period. The Company determined that the modification to extend the term of vested stock options was a Type I modification pursuant to ASC 718. The acceleration of the vesting of the unvested stock options was deemed a Type III modification pursuant to ASC 718, because pursuant to Dr. Cui’s existing employment agreement as of her resignation date, these stock options would have been forfeited on the date of termination. As a result of these modifications, the Company recognized $ 31.4 million in stock-based compensation expense in the first quarter of 2020. Because the services performed during the consulting period were considered nonsubstantive, the Company recognized the full $ 31.4 million in stock-based compensation expense on the date of the modification and presented this amount in general and administrative expenses in the statement of operations and comprehensive loss. Stock-Based Compensation Expense Stock-based compensation expense recognized is presented in the statements of operations and comprehensive loss as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 27,255 $ 15,539 $ 6,075 General and administrative 31,302 48,624 6,631 Total stock-based compensation expense $ 58,557 $ 64,163 $ 12,706 Common Stock Reserved for Future Issuance Common stock reserved for future issuance consisted of the following: December 31, 2021 2020 Common stock options outstanding 5,418,467 5,790,713 PSUs outstanding 204,759 — RSUs outstanding 358,760 21,500 Shares available for issuance under the Plan 3,215,165 2,294,124 Shares available for purchase under ESPP 202,046 249,817 Total 9,399,197 8,356,154

Defined Contribution Benefit Pl

Defined Contribution Benefit Plan	12 Months Ended
	Dec. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Benefit Plan	10. Defined Contribution Benefit Plan The Company sponsors a 401(k) retirement plan, in which substantially all of its full-time employees are eligible to participate. Participants may contribute a percentage of their annual compensation to this plan, subject to statutory limitations. The Company has recorded as expe nse $ 1.4 million , $ 0.8 million and $ 0.5 million in matching contributions for the years ended December 31, 2021, 2020 and 2019, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes No provision for federal or state income taxes has been recorded for the years ended December 31, 2021, 2020 and 2019, other than the $ 800 annual tax for C corporations paid to the state of California. A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows: Year Ended December 31, 2021 2020 2019 Tax computed at federal statutory rate 21.0 % 21.0 % 21.0 % Stock-based compensation 1.3 ( 1.7 ) 1.6 Research and development tax credits 4.1 2.5 1.6 Orphan drug tax credit 3.7 4.4 6.8 Other — ( 0.1 ) — Valuation allowance ( 30.1 ) ( 26.1 ) ( 31.0 ) Effective income tax rate — % — % — % Deferred tax assets and liabilities consist of the following (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 93,247 $ 47,411 Research and development credits 15,058 5,415 Orphan drug credit 24,476 15,622 Accrued liabilities 2,576 1,552 Right-of-use asset 1,172 802 Stock-based compensation expense 12,339 6,386 Other, net 12 2 Total deferred tax assets 148,880 77,190 Deferred tax liabilities Fixed assets ( 91 ) ( 124 ) Lease liabilities ( 1,084 ) ( 705 ) ( 1,175 ) ( 829 ) Total 147,705 76,361 Less: valuation allowance ( 147,705 ) ( 76,361 ) Net deferred tax assets $ — $ — The valuation allowance increased by $ 71.3 million during the year ended December 31, 2021. Due to the uncertainties surrounding the realization of deferred tax assets, the Company has provided a full valuation allowance and, therefore, no benefit has been recognized for the net operating loss carryforwards and other deferred tax assets. At December 31, 2021, the Company has federal and state net operating loss (NOLs) carryforwards of approximately $ 444.0 million and $ 112.0 million, respectively. Certain federal and state tax loss carryforwards will begin to expire in 2033 if not utilized. Approximate $ 423.0 million and $ 0.8 million of federal and state NOLs will carryforward indefinitely. At December 31, 2021, the Company has federal and state research and development tax credits of approximately $ 9.8 million and $ 10.4 million, respectively. At December 31, 2021, the Company has federal Orphan Drug tax credits of approximately $ 31.4 million. If not utilized, the federal research and development tax credit will begin to expire in 2035 and the Orphan Drug credit will begin to expire in 2037 . The California research and development tax credit can be carried forward indefinitely. Pursuant to Internal Revenue Code sections 382 and 383, use of the Company’s net operating loss and research and development tax credit carryforwards may be limited if a cumulative change in ownership of more than 50 % occurs within a three-year period. The Company completed an analysis under IRC Sections 382 and 383 through December 31, 2020. The Company experienced ownership changes in 2013, 2015, 2017 and 2020, the ownership changes did not result in a forfeiture of tax attributes. Total unrecognized income tax benefits related to California net operating losses, federal and California research and development and federal Orphan drug tax credit carryforwards were approximately $ 20.0 million at December 31, 2021. The Company’s policy is to include interest and penalties related to unrecognized tax benefits within the Company’s provision for income taxes. As of December 31, 2021, the Company has no accrual for interest and penalties related to unrecognized tax benefits. There are no unrecognized tax benefits that, if recognized, would impact the Company’s effective tax rate due to valuation allowances. The Company does not expect any unrecognized tax benefits to be recognized within the next 12 months. The Company recognizes a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. Income tax positions must meet a more likely than not recognition at the effective date to be recognized. As of December 31, 2021 and 2020, the unrecognized tax benefits recorded were approximately $ 20.1 million and $ 16.5 million, respectively. Approximately $ 17.7 million of the unrecognized tax benefits would reduce our annual effective tax rate, if recognized, subject to the valuation allowance. It is not anticipated that there will be significant change in the unrecognized tax benefits over the next 12 months. A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in thousands): December 31, 2021 2020 Beginning balance $ 16,473 $ 14,825 Additions (reductions) for tax positions taken in prior years 56 ( 869 ) Additions (reductions) for tax positions taken in current year 3,600 2,517 Ending balance $ 20,129 $ 16,473 The Company files income tax returns in the United States federal jurisdiction, California and in Florida, and the tax returns filed for the years 2015 through 2020 have not been examined and the applicable statutes of limitation have not expired with respect to those returns. Because of net operating loss and research credit carryovers, substantially all of the Company’s tax years remain open to examination.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP).
Use of Estimates	Use of Estimates The preparation of the Company's financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. The most significant estimates in the Company’s financial statements relate to determining the standalone selling prices ( SSP) of performance obligations associated with license and collaboration arrangements, accrued research and development expenses and stock-based compensation expenses . The Company bases these estimates on historical experience, knowledge of current events and actions it may undertake in the future, and on various other assumptions that are believed to be reasonable. A ctual results may differ materially from these estimates and assumptions. Although the impact of the COVID-19 pandemic to the Company’s business and operating results presents additional uncertainty, the Company continues to use the best information available to update its critical accounting estimates.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with Accounting Standards Codification (ASC) Topic 606, Revenue From Contracts With Customers (ASC 606). Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. The Company assesses the goods or services promised within each contract and determines those that are performance obligations. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations. The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. The transaction price is then determined and allocated to the identified performance obligations in proportion to their SSP on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment. If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less to be cash equivalents. As of December 31, 2021 and 2020, cash equivale nts consisted of checking, savings, and money market balances. The Company places its cash and cash equivalents with high credit quality financial institutions. All of the Company’s cash and cash equivalent balances are maintained at two financial institutions domiciled in the United States. The following table presents a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets to the amounts shown in the statements of cash flows (in thousands): Year Ended December 31, 2021 2020 2019 Cash and cash equivalents $ 427,879 $ 554,101 $ 48,188 Restricted cash included in other assets 1,876 73 73 Total cash, cash equivalents and restricted cash $ 429,755 $ 554,174 $ 48,261
Marketable Securities	Marketable Securities The Company classifies all marketable securities as available for sale, as the sale of such securities may be required prior to maturity. These marketable securities are carried at fair value, with unrealized gains and losses reported as accumulated other comprehensive income (loss) until realized. The cost of debt securities is adjusted for accretion of premiums and amortization of discounts to maturity. Such amortization and accretion, as well as interest and dividends, are included in other income, net. Realized gains and losses from the sale of available for sale securities, if any, are determined on a specific identification basis and are also included in other income, net. The Company’s marketable securities are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary.
Allowance for Credit Losses	Allowance for Credit Losses The Company segments its portfolio based on the underlying risk profiles of their current securities being held. The Company regularly reviews the securities in an unrealized loss position and evaluates the current expected credit loss by considering factors such as historical experience, market data, issuer-specific factors, current and expected future economic conditions. As of December 31, 2021, the Company did no t record an allowance for credit loss related to its investment portfolio.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should maximize the use of observable inputs and minimize the use of unobservable inputs. The Company determines the fair value of financial assets and liabilities using three levels of inputs as follows: Level 1 — Observable inputs such as quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 — Inputs (other than quoted market prices included in Level 1) that are either directly or indirectly observable, 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 instrument’s anticipated life; and Level 3 — Unobservable inputs for assets or liabilities and include little or no market activity. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
Concentration of Credit Risk	Concentration of Credit Risk Substantially all of the Company’s cash and cash equivalents and marketable securities are held at two financial institutions. Due to the financial strength of the depository institutions, the Company believes these financial institutions represent minimal credit risk. Cash amounts held at financial institutions are insured by the Federal Deposit Insurance Corporation (FDIC) up to $ 250,000 . At December 31, 2021 , cash and cash equivalents and marketable securities totaling $ 981.3 million are either not subject to FDIC insurance, or exceed the FDIC insured limit. The Company’s cash and cash equivalents and marketable securities are invested in short term, high grade securities, and as a result, the Company believes represent a minimal credit risk .
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful life of the assets, which ranges between three to seven years . R epairs and maintenance costs are charged to expense as incurred. Tenant improvements are stated at cost and depreciated over the shorter of the estimated useful life or the remaining life of the lease at the time the asset is placed into service.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its respective fair value. The Company did no t recognize any impairment losses during the years ended December 31, 2021, 2020 and 2019.
Leases	Leases The Company determines whether a contract is, or contains, a lease at inception. Right-of-use (ROU) assets represent the Company’s right to use an underlying asset during the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at lease commencement based upon the estimated present value of unpaid lease payments over the lease term using the Company’s incremental borrowing rate applicable to the underlying asset unless the implicit rate is readily determinable. The Company's incremental borrowing rate is determined based on the estimated rate of interest for collateralized borrowing over a similar term as the associated lease. ROU assets also include any lease payme nts made at or before lease commencement and any initial direct costs incurred, and exclude any lease incentives received. The Company determines the lease term as the non-cancellable period of the lease, and may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Leases with a term of 12 months or less are not recognized on the balance sheets.
Patent Costs	Patent Costs Legal and professional costs incurred by the Company to maintain its patent rights have been expensed as part of general and administrative expenses. As of December 31, 2021 and 2020, the Company has determined that these expenses have not met the criteria to be capitalized.
General and Administrative Expenses	General and Administrative Expenses General and administrative expenses consist primarily of salaries and employee-related costs, including stock-based compensation, for personnel in executive, finance, legal, commercial and other administrative functions. General and administrative expenses also include professional fees for legal, patent, accounting and tax-related services, insurance costs, recruiting costs, travel expenses and facility-related costs.
Research and Development Expenses and Accruals	Research and Development Expenses and Accruals Research and development costs are expensed as incurred. These costs consist primarily of employee-related expenses, including salaries and related benefits, travel and stock-based compensation for employees engaged in research and development functions; expenses incurred in connection with the preclinial and clinical development of drug candidates, including expenses incurred under the agreements with the CROs; the cost of consultants and contract manufacturing organizations that manufacture drug products for use in the preclinical studies and clinical trials; and facilities, depreciation and other expenses, including allocated expenses for rent and maintenance of facilities, insurance and supplies. The Company accrues the expenses for its clinical trial activities performed by third-party vendors, including CROs and clinical sites, based upon estimates of the proportion of work completed over the life of the individual clinical trial and patient enrollment rates in accordance with associated agreements. The Company determines the estimates by reviewing contracts and purchase orders, and through discussions with internal clinical personnel and external service providers as to the progress or stage of completion of trials or services pursuant to the contracts with the service providers and agreed-upon fees to be paid to identify services that have been performed on its behalf and estimate the level of service performed and the associated cost incurred for which it has not yet been invoiced. The Company records the estimated costs for research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued expenses and other current liabilities in the balance sheet and within research and development expense in the statement of operations and comprehensive loss. As actual costs become known, the Company will adjust its accrued expenses and other current liabilities. Payments for goods and services that will be used in future research and development activities are recorded as prepaid and other current assets and recognized as expense in the period when the goods are consumed or services are performed.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the statement of operations in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (i) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability.
Stock-Based Compensation Expense	Stock-Based Compensation Expense The Company measures and recognizes compensation expense for share-based awards based on the fair value of the award as measured at grant date. The fair value of restricted stock units (RSUs) and performance stock units (PSUs) granted is based on the Company’s closing stock price on the grant date. The fair value of stock options and employee stock purchase plan awards is estimated using the Black-Scholes option-pricing model. The determination of the estimated fair value of stock-based awards utilizing the Black-Scholes model is affected by the Company’s stock price and a number of assumptions, including the expected volatility of the Company’s stock price, the option's expected life, risk-free interest rate and expected dividend yield. Expected Term — The Company uses the simplified method for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years). Expected Volatility — Due to the Company’s limited operating history and a lack of company specific historical and implied volatility data, the Company estimates expected volatility based on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. Risk-Free Interest Rate — The risk-free rate assumption is based on the U.S. Treasury instruments with maturities similar to the expected term of the stock options. Expected Dividend Yield — The Company has not issued any dividends and does not expect to issue dividends over the life of the options. As a result, the Company has estimated the dividend yield to be zero . The estimated fair value of equity awards granted to employees and non-employee service providers are expensed over the requisite service period (generally the vesting term) on a straight-line basis , net of actual forfeitures when they occur .
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss available to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share assumes the conversion, exercise or issuance of all potential common stock equivalents, unless the effect of inclusion would be anti-dilutive. For purposes of this calculation, common stock equivalents include the Company’s stock options, RSUs and PSUs. The Company excluded stock options to purchase common stock, RSUs and PSUs from the number of shares used to calculate diluted shares outstanding because the inclusion of these potentially dilutive securities would have been antidilutive . Historical outstanding anti-dilutive securities not included in the diluted net loss per share calculation include the following: Year Ended December 31, 2021 2020 2019 Common stock options 5,418,467 5,790,713 5,254,269 RSUs 358,760 21,500 — PSUs 204,759 — — Total 5,981,986 5,812,213 5,254,269

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash and Cash Equivalents and Restricted cash	The following table presents a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets to the amounts shown in the statements of cash flows (in thousands): Year Ended December 31, 2021 2020 2019 Cash and cash equivalents $ 427,879 $ 554,101 $ 48,188 Restricted cash included in other assets 1,876 73 73 Total cash, cash equivalents and restricted cash $ 429,755 $ 554,174 $ 48,261
Schedule of Outstanding Anti-Dilutive Securities not Included in Diluted Net Loss Per Share Calculation	Historical outstanding anti-dilutive securities not included in the diluted net loss per share calculation include the following: Year Ended December 31, 2021 2020 2019 Common stock options 5,418,467 5,790,713 5,254,269 RSUs 358,760 21,500 — PSUs 204,759 — — Total 5,981,986 5,812,213 5,254,269

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities	At December 31, 2021, marketable securities consisted of the following (in thousands): Maturity Amortized Unrealized in Years Cost Gains Losses Fair Value U.S. Treasuries 2 years or less $ 305,763 $ 1 $ ( 1,006 ) $ 304,758 U.S. Government agency securities 2 years or less 151,047 — ( 180 ) 150,867 Non-U.S. Government agency securities 2 years or less 23,787 — ( 49 ) 23,738 Corporate debt securities 2 years or less 74,391 5 ( 56 ) 74,340 Total marketable securities $ 554,988 $ 6 $ ( 1,291 ) $ 553,703 At December 31, 2020, marketable securities consisted of the following (in thousands): Maturity Amortized Unrealized in Years Cost Gains Losses Fair Value U.S. Treasuries 2 years or less $ 113,662 $ 19 $ ( 1 ) $ 113,680 U.S. Government agency securities 2 years or less 173,583 100 — 173,683 Corporate debt securities 2 years or less 169,189 103 ( 27 ) 169,265 Commercial paper Less than 1 111,779 — — 111,779 Total marketable securities $ 568,213 $ 222 $ ( 28 ) $ 568,407

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Subject to Fair Value Measurements on a Recurring Basis and the Level of Inputs	The Company’s financial assets subject to fair value measurements on a recurring basis and the level of inputs used for such measurements were as follows (in thousands): Fair Value Measurements at December 31, 2021 Using: Level 1 Level 2 Level 3 Total Money market funds $ 232,813 $ — $ — $ 232,813 U.S. Treasuries 304,758 — — 304,758 U.S. Government agency securities — 150,867 — 150,867 Non-U.S. Government securities — 23,738 — 23,738 Corporate debt securities — 77,400 — 77,400 Commercial paper — 191,130 — 191,130 Total cash equivalents and marketable securities $ 537,571 $ 443,135 $ — $ 980,706 Fair Value Measurements at December 31, 2020 Using: Level 1 Level 2 Level 3 Total Money market funds $ 299,571 $ — $ — $ 299,571 U.S. Treasuries 113,680 — — 113,680 U.S. Government agency securities — 173,683 — 173,683 Corporate debt securities — 180,718 — 180,718 Commercial paper — 354,223 — 354,223 Total cash equivalents and marketable securities $ 413,251 $ 708,624 $ — $ 1,121,875

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): December 31, December 31, 2021 2020 Laboratory equipment $ 3,368 $ 1,629 Computer equipment and software 1,283 956 Tenant improvements 1,468 1,108 Furniture and fixtures 358 357 Property and equipment 6,477 4,050 Less: accumulated depreciation ( 2,655 ) ( 1,446 ) Property and equipment, net $ 3,822 $ 2,604

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Payables And Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, December 31, 2021 2020 Accrued research and development expenses $ 23,497 $ 8,457 Accrued general and administrative expenses 1,655 682 Other current liabilities 148 44 Total $ 25,300 $ 9,183

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Summary of Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of December 31, 2021 were as follows (in thousands) : 2022 $ 3,898 2023 1,989 Total future minimum lease payments 5,887 Less: amounts representing interest ( 308 ) Total lease liability $ 5,579 Remaining lease term 1.5 years

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Schedule of Stock Option Activity	The following table summarizes stock option activity under the Plan for the year ended December 31, 2021: Outstanding Weighted Weighted Aggregate Balance as of January 1, 2021 5,790,713 $ 34.97 8.4 $ 503,114 Options granted 1,198,486 $ 97.44 Options exercised ( 850,952 ) $ 26.07 Options forfeited or cancelled ( 719,780 ) $ 57.64 Balance as of December 31, 2021 5,418,467 $ 47.17 7.5 $ 91,794 Options vested and exercisable as of December 31, 2021 2,698,520 $ 29.18 6.7 $ 70,798
Schedule of Fair Values of Stock Options Granted	The fair values of the stock options granted during 2021, 2020 and 2019 was estimated at the date of grant using the Black-Scholes option-pricing model with the following assumptions: Year Ended December 31, 2021 2020 2019 Risk-free interest rate 0.88 % 1.15 % 2.13 % Volatility 80.1 % 79.5 % 79.8 % Expected term (in years) 6.06 6.07 6.05 Dividend yield — — — The assumptions used for the years ended December 31, 2021, 2020 and 2019 and the resulting estimates of weighted-average fair value per share for stock purchased under the ESPP were as follows : Year Ended December 31, 2021 2020 2019 Risk-free interest rate 0.04 - 0.66 % 0.08 – 0.19 % 1.55 - 2.13 % Volatility 69.2 - 80.1 % 79.7 - 91.6 % 70.6 - 76.2 % Expected term (in years) 0.50 - 2.00 0.50 - 2.00 0.50 - 2.00 Dividend yield — — —
Summary of Restricted Stock Unit Activity	The following table summarizes restricted stock unit activity under the Plan for the year ended December 31, 2021: Restricted Stock Units Outstanding Weighted Aggregate Balance as of January 1, 2021 21,500 $ 59.94 $ 2,620 Granted 373,982 $ 93.44 Vested ( 5,375 ) $ 59.94 Forfeited ( 31,347 ) $ 125.93 Outstanding as of December 31, 2021 358,760 $ 89.09 $ 17,113
Summary of Performance Stock Unit Activity	The following table summarizes performance stock unit activity under the Plan for the year ended December 31, 2021: Performance Stock Units Outstanding Weighted Aggregate Balance as of January 1, 2021 — $ — $ — Granted 241,365 $ 122.84 Vested — $ — Forfeited ( 36,606 ) $ 136.82 Outstanding as of December 31, 2021 204,759 $ 120.34 $ 9,767
Schedule of Stock Based Compensation Expense	Stock-based compensation expense recognized is presented in the statements of operations and comprehensive loss as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 27,255 $ 15,539 $ 6,075 General and administrative 31,302 48,624 6,631 Total stock-based compensation expense $ 58,557 $ 64,163 $ 12,706
Schedule of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance consisted of the following: December 31, 2021 2020 Common stock options outstanding 5,418,467 5,790,713 PSUs outstanding 204,759 — RSUs outstanding 358,760 21,500 Shares available for issuance under the Plan 3,215,165 2,294,124 Shares available for purchase under ESPP 202,046 249,817 Total 9,399,197 8,356,154

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate	A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows: Year Ended December 31, 2021 2020 2019 Tax computed at federal statutory rate 21.0 % 21.0 % 21.0 % Stock-based compensation 1.3 ( 1.7 ) 1.6 Research and development tax credits 4.1 2.5 1.6 Orphan drug tax credit 3.7 4.4 6.8 Other — ( 0.1 ) — Valuation allowance ( 30.1 ) ( 26.1 ) ( 31.0 ) Effective income tax rate — % — % — %
Summary of Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities consist of the following (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 93,247 $ 47,411 Research and development credits 15,058 5,415 Orphan drug credit 24,476 15,622 Accrued liabilities 2,576 1,552 Right-of-use asset 1,172 802 Stock-based compensation expense 12,339 6,386 Other, net 12 2 Total deferred tax assets 148,880 77,190 Deferred tax liabilities Fixed assets ( 91 ) ( 124 ) Lease liabilities ( 1,084 ) ( 705 ) ( 1,175 ) ( 829 ) Total 147,705 76,361 Less: valuation allowance ( 147,705 ) ( 76,361 ) Net deferred tax assets $ — $ —
Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in thousands): December 31, 2021 2020 Beginning balance $ 16,473 $ 14,825 Additions (reductions) for tax positions taken in prior years 56 ( 869 ) Additions (reductions) for tax positions taken in current year 3,600 2,517 Ending balance $ 20,129 $ 16,473

Organization - Additional Infor

Organization - Additional Information (Details)	Oct. 08, 2013Segment
Basis Of Presentation [Line Items]
Number of operating segments	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash and Cash Equivalents and Restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 427,879	$ 554,101	$ 48,188
Restricted cash included in other assets	1,876	73	73
Total cash, cash equivalents and restricted cash	$ 429,755	$ 554,174	$ 48,261	$ 101,029

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Significant Accounting Policies [Line Items]
Allowance for credit loss	$ 0
Exceed of federal deposits insurance limit	981,300,000
Impairment of long-lived assets	$ 0	$ 0	$ 0
Stock options expected contractual term	6 years 21 days	6 years 25 days	6 years 18 days
Expected dividend yield rate	0.00%
Minimum
Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Maximum
Significant Accounting Policies [Line Items]
Cash FDIC insured amount	$ 250,000
Estimated useful life	7 years
Arithmetic Average
Significant Accounting Policies [Line Items]
Stock options expected contractual term	10 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Outstanding Anti-Dilutive Securities not Included in Diluted Net Loss Per Share Calculation (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share	5,981,986	5,812,213	5,254,269
Common Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share	5,418,467	5,790,713	5,254,269
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share	358,760	21,500
PSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share	204,759

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Amortized Cost	$ 554,988	$ 568,213
Unrealized Gains	6	222
Unrealized Losses	(1,291)	(28)
Fair Value	$ 553,703	$ 568,407
U.S. Treasuries
Marketable Securities [Line Items]
Maturity in Years	2 years or less	2 years or less
Amortized Cost	$ 305,763	$ 113,662
Unrealized Gains	1	19
Unrealized Losses	(1,006)	(1)
Fair Value	$ 304,758	$ 113,680
U.S. Government Agency Securities
Marketable Securities [Line Items]
Maturity in Years	2 years or less	2 years or less
Amortized Cost	$ 151,047	$ 173,583
Unrealized Gains		100
Unrealized Losses	(180)
Fair Value	$ 150,867	$ 173,683
Non-U.S. Government Agency Securities
Marketable Securities [Line Items]
Maturity in Years	2 years or less
Amortized Cost	$ 23,787
Unrealized Losses	(49)
Fair Value	$ 23,738
Corporate Debt Securities
Marketable Securities [Line Items]
Maturity in Years	2 years or less	2 years or less
Amortized Cost	$ 74,391	$ 169,189
Unrealized Gains	5	103
Unrealized Losses	(56)	(27)
Fair Value	$ 74,340	$ 169,265
Commercial Paper
Marketable Securities [Line Items]
Maturity in Years		Less than 1
Amortized Cost		$ 111,779
Fair Value		$ 111,779

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Subject to Fair Value Measurements on a Recurring Basis and the Level of Inputs (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	$ 980,706	$ 1,121,875
Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	232,813	299,571
U.S. Treasuries
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	304,758	113,680
U.S Government Agency Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	150,867	173,683
Non-U.S. Government Agency Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	23,738
Corporate Debt Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	77,400	180,718
Commercial Paper
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	191,130	354,223
Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	537,571	413,251
Level 1 | Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	232,813	299,571
Level 1 | U.S. Treasuries
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	304,758	113,680
Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	443,135	708,624
Level 2 | U.S Government Agency Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	150,867	173,683
Level 2 | Non-U.S. Government Agency Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	23,738
Level 2 | Corporate Debt Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	77,400	180,718
Level 2 | Commercial Paper
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents and market securities	$ 191,130	$ 354,223

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6,477	$ 4,050
Less: accumulated depreciation	(2,655)	(1,446)
Property and equipment, net	3,822	2,604
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,368	1,629
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,283	956
Tenant Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,468	1,108
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 358	$ 357

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation	$ 1,209	$ 875	$ 492

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 23,497	$ 8,457
Accrued general and administrative expenses	1,655	682
Other current liabilities	148	44
Total	$ 25,300	$ 9,183

Zai License Agreements - Additi

Zai License Agreements - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Sep. 30, 2020	Dec. 31, 2021	Jan. 10, 2021	Jul. 31, 2020
License
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue recognized		$ 25,000,000
Zai Repotrectinib Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront cash payment received					$ 25,000,000
Total transaction price allocated to performance obligation			$ 25,700,000
Zai Repotrectinib Agreement | Clinical Supply
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total transaction price allocated to performance obligation			700,000
Revenue recognized			800,000
Zai Repotrectinib Agreement | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments eligible to receive					151,000,000
Zai Repotrectinib Agreement | Development Milestones
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue recognized			5,000,000
Zai Repotrectinib Agreement | Development Milestones | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments eligible to receive					46,000,000
Zai Repotrectinib Agreement | Sales Milestones | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments eligible to receive					$ 105,000,000
Zai Elzovantinib Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront cash payment received	$ 25,000,000
Total transaction price allocated to performance obligation			25,900,000
Zai Elzovantinib Agreement | License
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue recognized	$ 25,000,000
Zai Elzovantinib Agreement | Clinical Supply
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total transaction price allocated to performance obligation			900,000
Revenue recognized			$ 0
Zai Elzovantinib Agreement | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments eligible to receive				$ 336,000,000
Zai Elzovantinib Agreement | Development Milestones | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments eligible to receive				121,000,000
Zai Elzovantinib Agreement | Sales Milestones | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Milestone payments eligible to receive				$ 215,000,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitment And Contingencies [Line Items]
Operating lease, right-of-use asset		$ 5,158,000	$ 3,357,000
Current operating lease liabilities		3,630,000	1,396,000
Non-current operating lease liabilities		$ 1,949,000	2,423,000
Operating lease expiration date		Jun. 30, 2023
Lessee, Operating Lease, Existence of Option to Extend [true false]		true
Operating lease costs		$ 2,800,000	1,500,000	$ 1,100,000
Variable lease costs		1,400,000	1,200,000	700,000
Operating lease, cash payments		$ 2,200,000	$ 1,600,000	$ 1,200,000
Operating lease, weighted-average remaining lease term		1 year 6 months	2 years 7 months 6 days
Operating lease, weighted-average discount rate		7.00%	8.50%
Lessee operating lease option to extend lease term		5 years
Aggregate future lease commitments under lease		$ 5,887,000
HCP Callan Road, LLC
Commitment And Contingencies [Line Items]
Operating lease commencement date	May 31, 2023
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Base rent amount increase percentage per year over lease term	3.00%
Operating lease, lease term	11 years 9 months
Lessee operating lease option to extend lease term	5 years
Base rent	$ 1,000,000
Tenant improvement allowance per square foot	220
Aggregate future lease commitments under lease		$ 165,900,000
HCP Callan Road, LLC | Other Assets
Commitment And Contingencies [Line Items]
Letter of credit, secured deposit	$ 1,800,000

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
2022	$ 3,898
2023	1,989
Total future minimum lease payments	5,887
Less: amounts representing interest	(308)
Total lease liability	$ 5,579
Remaining lease term	1 year 6 months	2 years 7 months 6 days

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	Jan. 01, 2021	Aug. 01, 2020	Mar. 31, 2021	Mar. 31, 2020	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for issuance						3,215,165	2,294,124
Weighted-average grant-date fair value of options granted to employees						$ 66.72	$ 46	$ 21.66
Unrecognized compensation expense related to unvested options						$ 114,600,000
Unrecognized compensation expense, weighted-average period for recognition						2 years 3 months 18 days
Share-based compensation expense						$ 58,557,000	$ 64,163,000	$ 12,706,000
Total intrinsic value of stock options exercised						$ 59,700,000	$ 113,800,000	12,700,000
Common stock available for purchase						9,399,197	8,356,154
Stock-based compensation expense						$ 58,557,000	$ 64,163,000	12,706,000
General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense						$ 31,302,000	$ 48,624,000	$ 6,631,000
Resignation of Board of Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options exercise period extended date						Sep. 30, 2022
Resignation of Board of Directors | General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 5,600,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, weighted-average period for recognition						3 years 1 month 6 days
Total fair value of restricted stock units vested						$ 400,000
Number of awards vested						5,375	0	0
Unrecognized compensation expense related to unvested awards						$ 26,900,000
Performance Stock Unit
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of awards vested						0
Share-based compensation expense						$ 0
Chief Scientific Officer | Transition Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period					18 months
Cash severance expense				$ 1,200,000
Chief Scientific Officer | Transition Agreement | General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense				$ 31,400,000
Maximum | Chief Scientific Officer | Transition Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Extended options vesting period					12 months
Minimum | Chief Scientific Officer | Transition Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Extended options vesting period					90 days
2019 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based award, description						The Company’s 2019 Equity Incentive Plan (the Plan) provides for the grant of stock options, restricted stock and other equity awards of the Company’s common stock to employees, officers, consultants and directors. In addition, the number of shares of common stock available for issuance under the Plan will be automatically increased on the first day of each calendar year through January 1, 2029, by an amount equal to 4% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. On January 1, 2021, the Company added 1,947,141 shares to the Plan. As of December 31, 2021, the Plan had 3,215,165 total shares available for issuance.
Plan expiration date						Jan. 1, 2029
Percentage of outstanding common stock added to plan each year						4.00%
Number of shares added to plan	1,947,141
Number of shares available for issuance						3,215,165
2019 Equity Incentive Plan | After 2nd year
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period						3 months
2019 Equity Incentive Plan | Employees | After one year
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights						Initial option grants to employees typically vest 25% on the first anniversary of the original vesting date and monthly thereafter over a three-year period and expire three months after employee termination.
Exercise price of options as percentage						25.00%
2019 Equity Incentive Plan | Employees | After 2nd year
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period						3 years
2019 Equity Incentive Plan | Employees and non - employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period						4 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights						Subsequent option grants to employees and grants to non-employees typically vest monthly over a four-year period.
2019 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period						10 years
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of eligible earnings withholding						15.00%
Percentage of price of common stock purchased under ESPP						85.00%
Common stock available for purchase						202,046
Unrecognized compensation expense						$ 4,200,000
ATM Facility
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock authorized for issuance yet to issue		$ 250,000,000

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Outstanding Options
Balance as of January 1, 2021	5,790,713
Options granted	1,198,486
Options exercised	(850,952)
Options forfeited or cancelled	(719,780)
Balance as of December 31, 2021	5,418,467	5,790,713
Options vested and exercisable as of December 31, 2021	2,698,520
Weighted Average Exercise Price Per Share
Balance as of January 1, 2021	$ 34.97
Options granted	97.44
Options exercised	26.07
Options forfeited or cancelled	57.64
Balance as of December 31, 2021	47.17	$ 34.97
Options vested and exercisable as of December 31, 2021	$ 29.18
Weighted average remaining contractual term
Weighted average remaining contractual term	7 years 6 months	8 years 4 months 24 days
Options vested and exercisable as of December 31, 2021	6 years 8 months 12 days
Aggregate Value Intrinsic
Balances	$ 91,794	$ 503,114
Options vested and exercisable as of December 31, 2021	$ 70,798

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Fair Values of Stock Options Granted (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.88%	1.15%	2.13%
Volatility	80.10%	79.50%	79.80%
Expected term (in years)	6 years 21 days	6 years 25 days	6 years 18 days
Expected dividend yield rate	0.00%
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate. minimum	0.04%	0.08%	1.55%
Risk-free interest rate. maximum	0.66%	0.19%	2.13%
Volatility, minimum	69.20%	79.70%	70.60%
Volatility, maximum	80.10%	91.60%	76.20%
Minimum | 2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months
Maximum | 2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	2 years	2 years	2 years

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Details) - RSUs - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Restricted Stock Units Outstanding
Balance as of January 1, 2021	21,500
Granted	373,982
Vested	(5,375)	0	0
Forfeited	(31,347)
Outstanding as of December 31, 2021	358,760	21,500
Weighted Average Grant Date Fair Value
Balance as of January 1, 2021	$ 59.94
Granted	93.44
Vested	59.94
Forfeited	125.93
Outstanding as of December 31, 2021	$ 89.09	$ 59.94
Aggregate Intrinsic Value (in thousands)
Outstanding	$ 17,113	$ 2,620

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Performance Stock Unit Activity (Details) - Performance Stock Unit $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Roll Forward
Granted	241,365
Vested	0
Forfeited	36,606
Outstanding as of December 31, 2021	204,759
Weighted Average Grant Date Fair Value
Granted | $ / shares	$ 122.84
Forfeited | $ / shares	136.82
Outstanding as of December 31, 2021 | $ / shares	$ 120.34
Aggregate Intrinsic Value
Outstanding | $	$ 9,767

Stockholders' Equity - Schedu_3

Stockholders' Equity - Schedule of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 58,557	$ 64,163	$ 12,706
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	27,255	15,539	6,075
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 31,302	$ 48,624	$ 6,631

Stockholders' Equity - Schedu_4

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock options outstanding	5,418,467	5,790,713
Shares available for issuance under the Plan	3,215,165	2,294,124
Shares available for purchase under ESPP	202,046	249,817
Total	9,399,197	8,356,154
PSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards outstanding	204,759
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards outstanding	358,760	21,500

Defined Contribution Benefit _2

Defined Contribution Benefit Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan, description	401(k)
Defined contribution plan, cost	$ 1.4	$ 0.8	$ 0.5

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Income Taxes [Line Items]
Provision for federal or state income taxes	$ 0	$ 0	$ 0
Increase in valuation allowance	71,300,000
Benefit recognized for net operating loss carryforwards	0
Federal net operating loss carryforwards	444,000,000
State net operating loss carryforwards	$ 112,000,000
Federal and state tax loss carryforwards expiration year	2033
Federal research and development tax credits	$ 9,800,000
State research and development tax credits	10,400,000
Federal Orphan Drug tax credits	$ 31,400,000
Federal research and development tax credit carry forwards expiration year start	2035
Orphan drug credit carryforwards expiration year	2037
Cumulative change in ownership minimum limited percentage of net operating loss and credit carryforwards	50.00%
Unrecognized tax benefits	$ 20,129,000	16,473,000	14,825,000
Accrual for interest and penalties related to unrecognized tax benefits	0
Unrecognized tax benefits would reduce annual effective tax rate, if recognized	17,700,000
State of California
Schedule Of Income Taxes [Line Items]
Unrecognized tax benefits	20,000,000
Federal
Schedule Of Income Taxes [Line Items]
Net operating loss carryforwards, not subject to expiration	423,000,000
State
Schedule Of Income Taxes [Line Items]
Net operating loss carryforwards, not subject to expiration	800,000
C Corporations | State of California
Schedule Of Income Taxes [Line Items]
Provision for federal or state income taxes	$ 800	$ 800	$ 800

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax computed at federal statutory rate	21.00%	21.00%	21.00%
Stock based compensation	1.30%	(1.70%)	1.60%
Research and development tax credits	4.10%	2.50%	1.60%
Orphan drug tax credit	3.70%	4.40%	6.80%
Other		(0.10%)
Valuation allowance	(30.10%)	(26.10%)	(31.00%)
Effective income tax rate	0.00%	0.00%	0.00%

Income Taxes - Summary of Defer

Income Taxes - Summary of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 93,247	$ 47,411
Research and development credits	15,058	5,415
Orphan drug credit	24,476	15,622
Accrued liabilities	2,576	1,552
Right of use asset	1,172	802
Stock-based compensation expense	12,339	6,386
Other, net	12	2
Total deferred tax assets	148,880	77,190
Deferred tax liabilities
Fixed assets	(91)	(124)
Lease liabilities	(1,084)	(705)
Deferred Tax Liabilities, Gross	(1,175)	(829)
Total	147,705	76,361
Less: valuation allowance	(147,705)	(76,361)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Reconciliation_2

Income Taxes - Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Beginning balance	$ 16,473	$ 14,825
Additions (reductions) for tax positions taken in prior years	56
Additions (reductions) for tax positions taken in prior years		(869)
Additions (reductions) for tax positions taken in current year	3,600	2,517
Ending balance	$ 20,129	$ 16,473

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited) - Summary of Quarterly Results (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Loss from operations	$ (238,000)	$ (161,836)	$ (77,724)
Net loss	$ (236,551)	$ (157,292)	$ (72,131)
Net loss per share, basic and diluted	$ (4.80)	$ (3.85)	$ (2.99)
Weighted-average common shares outstanding, basic and diluted	49,264,549	40,843,782	24,124,924