Viking Therapeutics (VKTX) 10-Q 25 Oct 23 2023 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Oct. 15, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Security Exchange Name	NASDAQ
Trading Symbol	VKTX
Entity Registrant Name	VIKING THERAPEUTICS, INC.
Entity Central Index Key	0001607678
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		100,028,953
Entity File Number	001-37355
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-1073877
Entity Address, Address Line One	9920 Pacific Heights Blvd
Entity Address, Address Line Two	Suite 350
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	704-4660
Document Quarterly Report	true
Document Transition Report	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 37,185	$ 36,632
Short-term investments – available for sale	339,056	118,853
Prepaid clinical trial and preclinical study costs	4,389	8,144
Prepaid expenses and other current assets	670	3,411
Total current assets	381,300	167,040
Right-of-use assets	1,200	1,418
Deferred financing costs	130	38
Deposits	33	33
Total assets	382,663	168,529
Current liabilities:
Accounts payable	5,711	8,529
Other accrued liabilities	7,375	13,114
Lease liability, current	319	304
Total current liabilities	13,405	21,947
Lease liability, net of current portion	1,018	1,260
Total long-term liabilities	1,018	1,260
Total liabilities	14,423	23,207
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.00001 par value: 10,000,000 shares authorized at September 30, 2023 and December 31, 2022; no shares issued and outstanding at September 30, 2023 and December 31, 2022
Common stock, $0.00001 par value: 300,000,000 shares authorized at September 30, 2023 and December 31, 2022; 100,028,828 shares issued and outstanding at September 30, 2023 and 78,257,258 shares issued and outstanding at December 31, 2022	1	1
Treasury stock at cost, 2,193,251 shares at September 30, 2023 and December 31, 2022	(6,795)	(6,795)
Additional paid-in capital	729,278	445,267
Accumulated deficit	(353,339)	(292,049)
Accumulated other comprehensive loss	(905)	(1,102)
Total stockholders’ equity	368,240	145,322
Total liabilities and stockholders’ equity	$ 382,663	$ 168,529

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	100,028,828	78,257,258
Common stock, shares outstanding	100,028,828	78,257,258
Treasury stock, shares	2,193,251	2,193,251

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Revenues	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	18,379	11,959	43,304	38,056
General and administrative	8,886	4,237	28,238	12,016
Total operating expenses	27,265	16,196	71,542	50,072
Loss from operations	(27,265)	(16,196)	(71,542)	(50,072)
Other income (expense):
Amortization of financing costs	(2)	(27)	(62)	(51)
Interest income, net	4,733	450	10,314	857
Realized loss on investments, net	0	0	0	(42)
Total other income, net	4,731	423	10,252	764
Net loss	(22,534)	(15,773)	(61,290)	(49,308)
Other comprehensive loss, net of tax:
Unrealized gain (loss) on securities	221	111	305	(813)
Foreign currency translation loss	(86)	(223)	(108)	(399)
Comprehensive loss	$ (22,399)	$ (15,885)	$ (61,093)	$ (50,520)
Basic net loss per common share	$ (0.23)	$ (0.21)	$ (0.66)	$ (0.64)
Weighted-average shares used to compute basic net loss per share	99,845,733	76,505,383	92,481,155	76,916,845
Diluted net loss per common share	$ (0.23)	$ (0.21)	$ (0.66)	$ (0.64)
Weighted-average shares used to compute diluted net loss per share	99,845,733	76,505,383	92,481,155	76,916,845

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2021	$ 201,884	$ 1	$ 425,614	$ (223,182)	$ (549)
Balance (in shares) at Dec. 31, 2021		78,248,401
Employee stock-based compensation, net	6,517		6,517
Shares withheld related to employee tax withholding	(499)		(499)
Shares withheld related to employee tax withholding (in shares)		(105,475)
Issuance of common stock under employee stock plans	84		84
Issuance of common stock under employee stock plans (in shares)		266,303
Issuance of common stock from warrant exercises	614		614
Issuance of common stock from warrant exercises (in shares)		472,500
Repurchase of common stock	(6,795)					$ (6,795)
Repurchase of common stock (in shares)		(2,193,251)
Unrealized gain/loss on Investments	(813)				(813)
Unrealized currency translation loss	(399)				(399)
Net Loss	(49,308)			(49,308)
Balance at Sep. 30, 2022	151,285	$ 1	432,330	(272,490)	(1,761)	(6,795)
Balance (in shares) at Sep. 30, 2022		76,688,478
Balance at Dec. 31, 2021	$ 201,884	$ 1	425,614	(223,182)	(549)
Balance (in shares) at Dec. 31, 2021		78,248,401
Sale of common stock, net of issuance costs (in shares)	0
Balance at Dec. 31, 2022	$ 145,322	$ 1	445,267	(292,049)	(1,102)	(6,795)
Balance (in shares) at Dec. 31, 2022		78,257,258
Balance at Jun. 30, 2022	165,230	$ 1	430,390	(256,717)	(1,649)	(6,795)
Balance (in shares) at Jun. 30, 2022		76,688,478
Employee stock-based compensation, net	1,940		1,940
Unrealized gain/loss on Investments	111				111
Unrealized currency translation loss	(223)				(223)
Net Loss	(15,773)			(15,773)
Balance at Sep. 30, 2022	151,285	$ 1	432,330	(272,490)	(1,761)	(6,795)
Balance (in shares) at Sep. 30, 2022		76,688,478
Balance at Dec. 31, 2022	145,322	$ 1	445,267	(292,049)	(1,102)	(6,795)
Balance (in shares) at Dec. 31, 2022		78,257,258
Employee stock-based compensation, net	12,670		12,670
Shares withheld related to employee tax withholding	(7,121)		(7,121)
Shares withheld related to employee tax withholding (in shares)		(509,686)
Issuance of common stock under employee stock plans	6,580		6,580
Issuance of common stock under employee stock plans (in shares)		2,274,752
Sale of common stock, net of issuance costs	$ 271,882		271,882
Sale of common stock, net of issuance costs (in shares)	0	20,006,504
Unrealized gain/loss on Investments	$ 305				305
Unrealized currency translation loss	(108)				(108)
Net Loss	(61,290)			(61,290)
Balance at Sep. 30, 2023	368,240	$ 1	729,278	(353,339)	(905)	(6,795)
Balance (in shares) at Sep. 30, 2023		100,028,828
Balance at Jun. 30, 2023	386,115	$ 1	724,754	(330,805)	(1,040)	(6,795)
Balance (in shares) at Jun. 30, 2023		100,028,828
Employee stock-based compensation, net	4,481		4,481
Sale of common stock, net of issuance costs	43		43
Unrealized gain/loss on Investments	221				221
Unrealized currency translation loss	(86)				(86)
Net Loss	(22,534)			(22,534)
Balance at Sep. 30, 2023	$ 368,240	$ 1	$ 729,278	$ (353,339)	$ (905)	$ (6,795)
Balance (in shares) at Sep. 30, 2023		100,028,828

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		21 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023
Cash flows from operating activities
Net loss			$ (61,290)	$ (49,308)
Adjustments to reconcile net loss to net cash used in operating activities
Amortization of investment premiums			(5,500)	1,270
Amortization of financing costs	$ 2	$ 27	62	51
Stock-based compensation	4,481	1,940	12,670	6,517
Amortization of right-of-use assets			218	219
Realized loss on investment				42
Interest expense related to operating lease liability			33	29
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			6,466	(1,698)
Accrued interest, net of interest receivable on maturity of investments			422	499
Accounts payable			(2,819)	1,698
Accrued expenses			(5,738)	3,315
Lease liability			(260)	(105)
Net cash used in operating activities			(55,736)	(37,471)
Cash flows from investing activities
Purchases of investments			(380,770)	(76,825)
Proceeds from sales and maturities of investments			165,951	124,318
Net cash (used in) provided by investing activities			(214,819)	47,493
Cash flows from financing activities
Public offering, net of offering costs			269,760	10
Value of shares withheld related to employee tax withholding			(7,121)	(499)
Repurchase of common stock				(6,795)
Proceeds from warrant and option exercises and stock issuances under employee stock purchase plan			6,580	698
ATM offering, net of fees			1,969
Net cash provided by (used in) financing activities			271,188	(6,586)
Net increase in cash and cash equivalents			633	3,436
Cash and cash equivalents beginning of period			36,632	26,371	$ 26,371
Effect of exchange rate changes on cash			(80)	(399)
Cash and cash equivalents end of period	$ 37,185	$ 29,408	37,185	29,408	$ 37,185
Supplemental disclosure of non-cash investing and financing transactions
Unpaid deferred public offering and other financing costs			$ 50	25
Right-of-use asset obtained in exchange for lease obligation				$ 1,664

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies The Company Viking Therapeutics, Inc., a Delaware corporation, together with its subsidiary (the “Company”), is a clinical-stage biopharmaceutical company focused on the development of novel therapies for metabolic and endocrine disorders. In June of 2021, the Company formed an Australian subsidiary, Viking Therapeutics, PTY LTD, so as to be able to take advantage of certain research and development reimbursements available to local Australian based research and development companies that choose to do research in Australia. The Company was incorporated under the laws of the State of Delaware on September 24, 2012 and its principal executive offices are located in San Diego, California, with a subsidiary located in Adelaide, Australia. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying consolidated balance sheet as of September 30, 2023, consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2023 and 2022, consolidated statements of stockholders’ equity for the three and nine months ended September 30, 2023 and 2022, and consolidated statements of cash flows for the nine months ended September 30, 2023 and 2022 are unaudited. These unaudited consolidated financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (the “SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the accompanying notes for the year ended December 31, 2022 contained in the Annual Report on Form 10-K filed by the Company with the SEC on February 10, 2023. The unaudited interim consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of September 30, 2023, the unaudited consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2023 and 2022, the unaudited consolidated statements of stockholders’ equity for the three and nine months ended September 30, 2023 and 2022 and the unaudited consolidated statements of cash flows for the nine months ended September 30, 2023 and 2022. The December 31, 2022 consolidated balance sheet included herein was derived from the audited consolidated financial statements, but it does not include all disclosures or notes required by GAAP for complete consolidated financial statements. The financial data and other information disclosed in these notes to the consolidated financial statements related to the three and nine months ended September 30, 2023 and 2022 are unaudited. Interim results are not necessarily indicative of results for an entire year. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying consolidated financial statements. Significant estimates made in preparing these consolidated financial statements relate to accounting for an operating lease and certain commitments. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. Investments Available-for-Sale Available-for-sale investments are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive loss. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. The amortization of premiums and accretion of discounts is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income (expense). The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured depository institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity. Prepaid Clinical Trial and Preclinical Study Costs Prepaid clinical trial and preclinical study costs represent advance payments by the Company for future clinical trial and preclinical study services to be performed by the clinical research organization and other research organizations. Such amounts are recognized as research and development expense as the related clinical trial and preclinical study services are performed. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) assets, and lease liability obligations are included in the Company’s consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liability obligations represent its obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company uses the implicit rate when readily determinable. The ROU asset also includes any lease payments made and excludes lease incentives and lease direct costs. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. Please refer to Note 4 for additional information. Deferred Financing Costs Deferred financing costs represent legal, accounting and other direct costs related to the Company’s efforts to raise capital through a public or private sale of the Company’s common stock. Costs related to the public sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are reclassified to additional paid-in-capital as a reduction of the proceeds. Costs related to the private sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are amortized over the term of the applicable purchase agreement. Revenue Recognition The Company has not recorded any revenues since its inception. However, in the future, the Company may enter into collaborative research and licensing agreements, under which the Company could be eligible for payments made in the form of upfront license fees, research funding, cost reimbursement, contingent event-based payments and/or royalties. On January 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers and all related amendments (“ASC 606” or “the revenue standard”). ASC 606 is a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The revenue standard is based on the principle that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, ASC 606 provides that an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when (or as) the entity satisfies a performance obligation. The revenue standard also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, and costs to obtain or fulfill contracts. The Company will apply ASC 606 prospectively to all contracts. Research and Development Expenses All costs of research and development are expensed in the period incurred. Research and development costs primarily consist of fees paid to CROs and clinical trial sites, employee and consultant related expenses, which include salaries, benefits and stock-based compensation for research and development personnel, external research and development expenses incurred pursuant to agreements with third-party manufacturing organizations, facilities costs, travel costs, dues and subscriptions, depreciation and materials used in preclinical studies, clinical trials and research and development. The Company estimates its preclinical study and clinical trial expenses based on the services it received pursuant to contracts with research institutions and CROs that conduct and manage preclinical studies and clinical trials on the Company’s behalf. Clinical trial-related contracts vary significantly in length, and may be for a fixed amount based on milestones or deliverables, a variable amount based on actual costs incurred, capped at a certain limit, or a combination of these elements. The Company accrues service fees based on work performed, which relies on estimates of total costs incurred based on milestones achieved, patient enrollment and other events. The majority of the Company’s service providers invoice the Company in arrears, and to the extent that amounts invoiced differ from its estimates of expenses incurred, the Company accrues for additional costs. The financial terms of these agreements vary from contract to contract and may result in uneven expenses and payment flows. Preclinical study and clinical trial expenses include: • fees paid to CROs, consultants and laboratories in connection with preclinical studies; • fees paid to CROs, clinical trial sites, investigators and consultants in connection with clinical trials; and • fees paid to contract manufacturers and service providers in connection with the production, testing and packaging of active pharmaceutical ingredients and drug materials for preclinical studies and clinical trials. Payments under some of these agreements depend on factors such as the milestones accomplished, including enrollment of certain numbers of patients, site initiation and the completion of clinical trial milestones. To date, the Company has not experienced any events requiring it to make material adjustments to its accruals for service fees. If the Company does not identify costs that it has begun to incur or if it underestimates or overestimates the level of services performed or the costs of these services, its actual expenses could differ from its estimates, which could materially affect its results of operations. Adjustments to the Company’s accruals are recorded as changes in estimates become evident. Furthermore, based on amounts invoiced to the Company by its service providers, the Company may also record payments made to those providers as prepaid expenses that will be recognized as expense in future periods as services are rendered. Related to the Company’s Australian subsidiary, Viking Therapeutics, PTY LTD, the Company is eligible under the AusIndustry Research and Tax Development Tax Incentive Program to obtain a cash amount from the Australian Taxation Office (ATO). The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply related to research and development expenditures in Australia. As there is no specific GAAP guidance related to how to record this research and development tax incentive, the Company looked to International Accounting Standard (IAS) 20 and determined that it will recognize these research and development tax incentives as contra research and development expense once received. The amounts are determined based on a cost-reimbursement basis, and the incentive is related to the Company’s research and development expenditures and is due regardless of whether any Australian tax is owed. Patent Costs Costs related to filing and pursuing patent applications are expensed as incurred to general and administrative expense, as recoverability of such expenditures is uncertain. Stock-Based Compensation The Company generally uses the straight-line method to allocate compensation cost to reporting periods over each optionee’s requisite service period, which is generally the vesting period, and estimates the fair value of stock-based awards or restricted stock units to employees and directors using the Black-Scholes option-valuation model (the “Black-Scholes model”). The Black-Scholes model requires the input of subjective assumptions, including volatility, the expected term and the fair value of the underlying common stock on the date of grant, among other inputs. For restricted stock and restricted stock unit awards, the Company generally uses the straight-line method to allocate compensation cost to reporting periods over the holder’s requisite service period, which is generally the vesting period, and uses the fair value at grant date to value the awards. For restricted stock that vests upon the satisfaction of certain performance conditions, the Company recognizes stock-based compensation expense when it becomes probable that the performance conditions will be met. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of the Company’s common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. For the Company’s 2014 Employee Stock Purchase Plan (the “ESPP”), the Company generally recognizes compensation expense for the fair value of the purchase options, as measured on the grant date, and uses the graded vesting method to allocate this compensation cost to each purchase period within the related two-year offering period. As the ESPP also allows for up to one increase in contributions during each purchase period, as an employee elects to increase his or her contributions, the Company treats this as an accounting modification. The pre- and post-modification values are calculated on the date of the modification, and the incremental expense is then amortized over the remaining purchase periods. Income Taxes The Company accounts for its income taxes using the liability method whereby deferred tax assets and liabilities are determined based on temporary differences between the basis used for financial reporting and income tax reporting purposes. Deferred income taxes are provided based on the enacted tax rates in effect at the time such temporary differences are expected to reverse. A valuation allowance is provided for deferred tax assets if it is more likely than not that the Company will not realize those tax assets through future operations. FASB Accounting Standards Codification Topic 740-10, Income Taxes , clarifies the accounting for uncertainty in income taxes recognized in the Company’s consolidated financial statements in accordance with GAAP. Income tax positions must meet a more-likely-than-not recognition threshold to be recognized. Income tax positions that previously failed to meet the more-likely-than-not threshold are recognized in the first subsequent financial reporting period in which that threshold is met. Previously recognized tax positions that no longer meet the more-likely-than-not threshold are derecognized in the first subsequent financial reporting period in which that threshold is no longer met. The Company’s policy is to recognize interest and penalties accrued on any unrecognized tax benefits as a component of income tax expense. Foreign Currency The financial statements of the Company’s foreign subsidiary whose functional currency is the local currency are translated into U.S. dollars for consolidation as follows: assets and liabilities at the exchange rate as of the balance sheet date, stockholders’ equity at the historical rates of exchange, and income and expense amounts at the average exchange rate for the period. Translation adjustments resulting from the translation of the subsidiaries’ accounts are included in “Accumulated other comprehensive loss” as equity in the consolidated balance sheet. Transactions denominated in currencies other than the applicable functional currency are converted to the functional currency at the exchange rate on the transaction date. At period end, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses resulting from foreign currency transactions are included within “Total other income, net” in the consolidated statement of operations. For the three months ended September 30, 2023 and 2022, foreign currency transaction loss amounted to $ 86,000 and $ 1,000 , respectively. For the nine months ended September 30, 2023 and 2022, foreign currency transaction loss amounted to $ 108,000 and $ 1,000 , respectively. Comprehensive Loss The Company’s comprehensive loss consists of net loss, changes in unrealized gains and losses on its investments and foreign currency translation adjustments arising from the consolidation of the Company’s foreign subsidiary. Net Loss per Common Share Basic net loss per share is calculated by dividing the net loss attributable 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 is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, the Company currently does not have any deemed common share equivalents; therefore, its basic and diluted net loss per share calculations are the same. The following table presents the computation of basic and diluted net loss per common share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Numerator: Net loss attributable to common stockholders $ ( 22,534 ) $ ( 15,773 ) $ ( 61,290 ) $ ( 49,308 ) Denominator: Weighted-average common shares outstanding 100,028,828 76,688,478 92,664,250 77,099,940 Less: Weighted-average shares subject to repurchase ( 183,095 ) ( 183,095 ) ( 183,095 ) ( 183,09 5 ) Denominator for basic and diluted net loss per share 99,845,733 76,505,383 92,481,155 76,916,845 Net loss per share: Basic and diluted $ ( 0.23 ) $ ( 0.21 ) $ ( 0.66 ) $ ( 0.64 ) Potentially dilutive securities that are not included in the calculation of diluted net loss per share because their effect is anti-dilutive are as follows (in common equivalent shares): As of September 30, 2023 2022 Common stock warrants — 14,587 Restricted stock units 2,855,656 1,770,582 Common stock subject to repurchase 183,095 183,095 Common stock options 5,243,807 5,107,857 8,282,558 7,076,121 Segments The Company operates in only one segment. Management uses cash flows as the primary measure to manage its business and does not segment its business for internal reporting or decision-making purposes.

Investments in Marketable Secur

Investments in Marketable Securities	9 Months Ended
	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Investments in Marketable Securities	2. Investments in Marketable Securities The Company’s investment strategy is focused on capital preservation. The Company invests in instruments that meet the credit quality standards outlined in the Company’s investment policy. This policy also limits the amount of credit exposure to any one issue or type of instrument. As of each of September 30, 2023 and December 31, 2022, the Company’s investments were in government money market funds, certificates of deposit, commercial paper, corporate debt securities and government debt securities. There were no sales of available-for-sale securities during the three and nine months ended September 30, 2023 or during the year ended December 31, 2022. Investments classified as available-for-sale as of September 30, 2023 consisted of the following (in thousands): As of September 30, 2023 Amortized Gross (1) Gross (1) Aggregate Commercial paper (2) $ 90,828 $ 1 $ ( 1 ) $ 90,828 Corporate debt securities (2) 98,539 26 ( 226 ) 98,339 Government debt securities (2) 150,228 1 ( 340 ) 149,889 $ 339,595 $ 28 $ ( 567 ) $ 339,056 (1) Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At September 30, 2023, there were 10 securities in an unrealized gain position and there were 97 securities in an unrealized loss position. The unrealized gains were less than $ 19,000 individually and $ 29,000 in the aggregate. The unrealized losses were less than $ 48,000 individually and $ 567,000 in the aggregate. The Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell these investments before recovery of their amortized cost basis, which may be at maturity. The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. (2) At September 30, 2023, none of these securities were classified as cash and cash equivalents on the Company’s consolidated balance sheet, and none o f the corporate debt securities were scheduled to mature outside of one year at the time of purchase. Investments classified as available-for-sale as of December 31, 2022 consisted of the following (in thousands): As of December 31, 2022 Amortized Gross (1) Gross (1) Aggregate Commercial paper (2) $ 43,780 $ — $ — $ 43,780 Corporate debt securities (2) 72,183 — ( 824 ) 71,359 Government debt securities (2) 3,732 — ( 18 ) 3,714 $ 119,695 $ — $ ( 842 ) $ 118,853 (1) Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At December 31, 2022, there were no securities in an unrealized gain position and 39 securities in an unrealized loss position. The unrealized losses were less than $ 124,000 individually and $ 842,000 in the aggregate. 22 of these securities have been in a continuous unrealized loss or unrealized gain position for more than 12 months. The Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell these investments before recovery of their amortized cost basis, which may be at maturity. The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. (2) At December 31, 2022, none of these securities were classified as cash and cash equivalents on the Company’s consolidated balance sheet, and none of the corporate debt securities were scheduled to mature outside of one year.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	3. Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, investments and accounts payable. The carrying amounts reported in the accompanying consolidated balance sheets for cash and cash equivalents and accounts payable approximate fair value because of the short-term maturity of those instruments. Fair value measurements are classified and disclosed in one of the following three categories: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. As of September 30, 2023 and December 31, 2022, all of the Company’s financial assets that were subject to fair value measurements were valued using observable inputs. The Company’s financial assets valued based on Level 1 inputs consist of money market funds. The Company’s financial assets valued based on Level 2 inputs consist of certificates of deposit, commercial paper, corporate debt securities and government debt securities, which consist of investments in highly rated investment-grade corporations. The Company’s investment strategy is focused on capital preservation. The Company invests in instruments that meet the credit quality standards outlined in the Company’s investment policy. This policy also limits the amount of credit exposure to any one issue or type of instrument. As of September 30, 2023, the Company’s investments were in government money market funds, commercial paper, corporate debt securities and government debt securities. The fair values of the Company’s financial instruments are presented below (in thousands): Fair Value Measurements at September 30, 2023 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: $ 32,844 $ 19,398 $ 13,446 $ — Short-term investments Commercial paper, available-for-sale 90,828 — 90,828 — Corporate debt securities, available-for-sale 98,339 — 98,339 — Government debt securities, available-for-sale 149,889 — 149,889 — Total financial assets $ 371,900 $ 19,398 $ 352,502 $ — Fair Value Measurements at December 31, 2022 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: $ 16,243 $ 5,617 $ 10,626 $ — Short-term investments Commercial paper, available-for-sale 43,780 — 43,780 — Corporate debt securities, available-for-sale 71,359 — 71,359 — Government debt securities, available-for-sale 3,714 — 3,714 — Total financial assets $ 135,096 $ 5,617 $ 129,479 $ —

Operating Leases - ROU Assets a

Operating Leases - ROU Assets and Lease Liability Obligations	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Operating Leases - ROU Assets and Lease Liability Obligations	4. Operating Leases – ROU Assets and Lease Liability Obligations The Company has only one operating lease (the “Office Lease”), which is for office space under a lease that commenced on March 1, 2022 and expires on July 31, 2027 (the “Term”). Below is a summary of the Company’s ROU assets and lease liabilities as of September 30, 2023 and December 31, 2022 (in thousands, except for years and %): September 30, 2023 December 31, 2022 Right-of-use assets $ 1,200 $ 1,418 Lease liability obligations, current $ 319 $ 304 Lease liability obligations, less current portion 1,018 1,260 Total lease liability obligations $ 1,337 $ 1,564 Weighted-average remaining lease term 3.83 years 4.58 years Weighted-average discount rate 3.00 % 3.00 % During the three and nine months ended September 30, 2023, the Company recognize d $ 84,000 and $ 255,000 in operating lease expenses, respectively, which are included in operating expenses in the Company’s consolidated statement of operations. During the three and nine months ended September 30, 2022, the Company recognized $ 88,000 and $ 257,000 in operating lease expenses, respectively, which are included in operating expenses in the Company’s consolidated statement of operations. Approximate future minimum lease payments for the Company’s ROU assets over the remaining lease period as of September 30, 2023 are as follows (in thousands): Remainder of 2023 $ 88 2024 357 2025 368 2026 379 2027 227 Total minimum lease payments $ 1,419 Less: amount representing interest $ ( 82 ) Total lease liability obligations $ 1,337 The Office Lease provides the Company with an option to extend the term of the Office Lease for a period of five years beyond the Term. If the option is exercised, the renewal term will be upon the same terms and conditions as the original Term, except that the base rent will be equal to the prevailing market rate as determined pursuant to the terms of the Office Lease. The option to extend the Term was not recognized as part of the Company’s lease liability and right-of-use assets.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Stockholders' Equity	5. Stockholders’ Equity Preferred Stock The Company is authorized to issue up to 10,000,000 shares of preferred stock, $ 0.00001 par value per share, with no shares of preferred stock outstanding as of September 30, 2023 and December 31, 2022. The Company’s Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company may issue without further action by the stockholders of the Company. Common Stock The Company is authorized to issue up to 300,000,000 shares of common stock, $ 0.00001 par value per share. In February 2014, the Company entered into a stock purchase agreement with one of its founders. The agreement provided for the purchase of 1,000,000 shares of the Company’s common stock at a price per share of $ 0.01 in exchange for future services to be rendered to the Company as measured by certain performance criteria. The shares were subject to a repurchase option and were to vest in two tranches of 500,000 shares each, upon achievement of the performance target or upon a triggering event as defined. The Company determined that the fair value of the unrecognized expense was $ 168,000 at February 20, 2014, the grant date. In May 2015, the Company repurchased 633,810 of these shares at a purchase price of $ 0.00001 per share. In connection with the repurchase, the Company entered into an amendment to the stock purchase agreement to provide that the remaining 366,190 shares will continue to vest in two tranches of 183,095 shares each, upon achievement of the performance target or upon a triggering event as defined. The pro rata grant date fair value of the unrecognized expense is $ 62,000 . In October 2015, a triggering event became probable of occurrence and was deemed achieved in October 2016; therefore, the Company recorded $ 31,000 of stock-based compensation expense through December 31, 2016. No similar expense was recognized during each of the three and nine months ended September 30, 2023 and 2022. The Company will continue to reassess at each reporting period whether it is probable that the performance target will be achieved, and if and when it is deemed probable, the Company will begin to record compensation expense using the fair value to determine stock-based compensation expense in its consolidated financial statements over the period the Company estimates the performance target will actually be achieved. On September 28, 2017, the Company entered into a purchase agreement (the “Commitment Purchase Agreement”) and a registration rights agreement with Lincoln Park Capital Fund, LLC (“LPC”), pursuant to which the Company had the right to sell to LPC up to $ 15.0 million in shares of common stock, subject to certain limitations and conditions set forth in the Commitment Purchase Agreement. Upon the satisfaction of the conditions in the Commitment Purchase Agreement (the “Commencement”), which occurred on October 26, 2017, the Company has the right, from time to time at its sole discretion over the 30 -month period from and after the first day of the month following the Commencement, to direct LPC to purchase up to 75,000 shares of common stock on any business day (subject to certain limitations contained in the Commitment Purchase Agreement), with such amounts increasing based on certain threshold prices set forth in the Commitment Purchase Agreement; however, not to exceed $ 1.0 million in total purchase proceeds per purchase date. The purchase price of shares of common stock that the Company elects to sell to LPC pursuant to the Commitment Purchase Agreement will be based on the market prices of the common stock at the time of such purchases as set forth in the Commitment Purchase Agreement. In addition to regular purchases, as described above, the Company may also direct LPC to purchase additional amounts as accelerated purchases or as additional purchases if the closing sale price of the common stock is not below certain threshold prices, as set forth in the Commitment Purchase Agreement. In all instances, the Company may not sell shares of its common stock to LPC under the Commitment Purchase Agreement if it would result in LPC beneficially owning more than 4.99 % of the common stock. As consideration for LPC’s commitment to purchase shares of common stock pursuant to the Commitment Purchase Agreement, the Company issued to LPC 100,000 shares of common stock (the “LPC Commitment Shares”). From inception of the Commitment Purchase Agreement through December 31, 2017, 343,051 shares were issued pursuant to the Commitment Purchase Agreement resulting in aggregate gross proceeds of $ 802,000 in addition to the LPC Commitment Shares. In May 2020, the Company extended the termination date of the Commitment Purchase Agreement to May 1, 2023, and the Commitment Purchase Agreement terminated on that date. No additional shares were issued during the years ended December 31, 2018 through 2022 or during 2023 until the termination date. On July 28, 2021, the Company filed with the SEC a universal Shelf Registration Statement on Form S-3 (File No. 333-258231) (the “2021 Shelf Registration Statement”). The 2021 Shelf Registration Statement provided the Company with the ability to offer up to $ 600.0 million of securities, including equity, debt and other securities as described in the 2021 Shelf Registration Statement. The 2021 Shelf Registration Statement was declared effective by the SEC on August 11, 2021 and the offering of all remaining unsold securities under the 2021 Shelf Registration Statement terminated on July 26, 2023 . On July 28, 2021, the Company entered into an At-The-Market Equity Offering Sales Agreement (the “ATM Agreement”), with Stifel, Nicolaus & Company, Incorporated, Truist Securities, Inc. and H.C. Wainwright & Co. LLC (collectively, the “Agents”), pursuant to which the Company may offer and sell, from time to time, through or to the Agents, as sales agent or principal (the “ATM Offering”), shares of the Company’s common stock (the “ATM Shares”). Any ATM Shares offered and sold in the ATM Offering were to be issued pursuant to the 2021 Shelf Registration Statement and the 424(b) prospectus supplement relating to the ATM Offering dated August 11, 2021. The 2021 Shelf Registration Statement terminated on July 26, 2023 . From its inception through the termination of the 2021 Shelf Registration Statement, 1,587,404 shares of the Company’s common stock were sold pursuant to the ATM Offering for aggregate net proceeds to the Company of approximately $ 13.6 million. On March 17, 2020, the Company’s Board of Directors authorized a stock repurchase program, whereby the Company could purchase up to $ 50.0 million in shares of its common stock and outstanding warrants to purchase its common stock, over a period of up to two years (the “Repurchase Program”). The Repurchase Program could be carried out at the discretion of a committee of the Company’s Board of Directors through open market purchases, one or more Rule 10b5-1 trading plans, block trades and in privately negotiated transactions. Through March 17, 2022, the termination date of the Repurchase Program, an aggregate of 1,464,217 shares of the Company’s common stock were repurchased by the Company under the Repurchase Program. These shares repurchased by the Company under the Repurchase Program are being held in treasury until such time as they are reissued or retired by the Company. On March 10, 2022, the Company’s Board of Directors authorized a new stock repurchase program effective March 18, 2022, whereby the Company may purchase up to $ 50.0 million in shares of its common stock, over a period of up to two years (the “New Repurchase Program”). The New Repurchase Program may be carried out at the discretion of a committee of the Company’s Board of Directors through open market purchases, one or more Rule 10b5-1 trading plans, block trades and in privately negotiated transactions. Through September 30, 2023, 729,034 shares of the Company’s common stock were repurchased by the Company under the New Repurchase Program. Shares repurchased by the Company under the New Repurchase Program are being held in treasury until such time as they are reissued or retired by the Company. On April 3, 2023, the Company completed an underwritten public offering of its common stock (the “April 2023 Offering”) pursuant to the 2021 Shelf Registration Statement. In the April 2023 Offering, the Company sold an aggregate of 19,828,300 shares of its common stock at a public offering price of $ 14.50 per share, which included the exercise in full by the underwriters of their option to purchase 2,586,300 additional shares of common stock. Upon the closing of the April 2023 Offering, the Company received net proceeds of $ 270.0 million, after deducting underwriting discounts, commissions and other offering expenses. On July 26, 2023, the Company filed an automatic universal shelf registration statement on Form S-3 (File No. 333-273460) as a well-known seasoned issuer as defined in Rule 405 under the Securities Act of 1933, as amended, which became effective upon filing (the “2023 Shelf Registration Statement”). The 2023 Shelf Registration Statement allows the Company to offer an indeterminate amount of securities, including equity securities, debt securities, warrants, rights, units and depositary shares, from time to time as described in the 2023 Shelf Registration Statement. The specific terms of any offering under the 2023 Shelf Registration Statement will be established at the time of such offering. The 2023 Shelf Registration Statement will expire on July 26, 2026. On July 26, 2023, the Company entered into an Amendment No. 1 to At-The-Market Equity Offering Sales Agreement (the “ATM Agreement Amendment”) with Stifel, Nicolaus & Company, Incorporated, Truist Securities, Inc., H.C. Wainwright & Co. LLC and BTIG, LLC. Pursuant to the ATM Agreement Amendment, BTIG, LLC was added as a sales agent for the ATM Offering and the ATM Agreement was amended to provide that the ATM Offering could be conducted off of registration statements on Form S-3 subsequently filed by the Company. Any ATM Shares offered and sold in the ATM Offering will now be issued pursuant to the 2023 Shelf Registration Statement and the prospectus relating to the ATM Offering, dated July 26, 2023, that was included in the 2023 Shelf Registration Statement (the “ATM Prospectus”). The 2023 Shelf Registration Statement will expire on July 26, 2026 . From the date of the ATM Prospectus through September 30, 2023, no shares of the Company’s common stock were sold pursuant to the ATM Offering and, as of September 30, 2023, the Company may sell shares of its common stock for remaining gross proceeds of up to $ 200.0 million from time to time pursuant to the ATM Prospectus. During the nine months ended September 30, 2023 and 2022, the Company issued 95,357 and 43,800 shares of its common stock pursuant to the ESPP, respectively.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	6. Stock-Based Compensation The Company generally uses the straight-line method to allocate compensation cost to reporting periods over each optionee’s requisite service period, which is generally the vesting period, and estimates the fair value of stock-based awards or restricted stock units to employees and directors using the Black-Scholes option-valuation model. The Black-Scholes model requires the input of subjective assumptions, including volatility, the expected term and the fair value of the underlying common stock on the date of grant, among other inputs. For restricted stock and restricted stock unit awards, the Company generally uses the straight-line method to allocate compensation cost to reporting periods over the holder’s requisite service period, which is generally the vesting period, and uses the fair value at grant date to value the awards. For restricted stock that vests upon the satisfaction of certain performance conditions, the Company recognizes stock-based compensation expense when it becomes probable that the performance conditions will be met. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of its common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. For the ESPP, the Company generally recognizes compensation expense for the fair value of the purchase options, as measured on the grant date, and uses the graded vesting method to allocate this compensation cost to each purchase period within the related two-year offering period. As the ESPP also allows for up to one increase in contributions during each purchase period, then as an employee elects to increase their contributions, the Company treats this as an accounting modification. The pre- and post-modification values are calculated on the date of the modification, and the incremental expense is then amortized over the remaining purchase periods. 2014 Plan . The Company’s 2014 Equity Incentive Plan (the “2014 Plan”) provides that the compensation committee of the Company’s Board of Directors (the “Compensation Committee”) may grant or issue stock options, stock appreciation rights, restricted shares, restricted stock units and unrestricted shares, deferred share units, performance and cash-settled awards and dividend equivalent rights to participants under the 2014 Plan. Initially, a total of 1,527,770 shares of the Company’s common stock were reserved for issuance pursuant to the 2014 Plan. The number of shares available for issuance under the 2014 Plan will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 3.5 % of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year. The shares of common stock deliverable pursuant to awards under the 2014 Plan are authorized but unissued shares of the Company’s common stock, or shares of the Company’s common stock that the Company otherwise holds in treasury or in trust. Any shares of the Company’s common stock underlying awards that are settled in cash or otherwise expire, or are forfeited, terminated or cancelled (including pursuant to an exchange program established by the Compensation Committee) prior to the issuance of stock will again be available for issuance under the 2014 Plan. In addition, shares of the Company’s common stock that are withheld (or not issued) in payment of the exercise price or taxes relating to an award, and shares of the Company’s common stock equal to the number surrendered in payment of any exercise price or withholding taxes relating to an award, will again be available for issuance under the 2014 Plan. As of December 31, 2022, there were 6,228,558 shares of the Company’s common stock available for issuance and, effective January 1, 2023, an additional 2,739,004 shares of the Company’s common stock were added to the number of shares reserved for issuance under the 2014 Plan in accordance with the terms of the 2014 Plan. As of September 30, 2023, there were 6,531,433 shares of the Company’s common stock available for issuance under the 2014 Plan. ESPP . Initially, a total of 458,331 shares of the Company’s common stock were reserved for issuance pursuant to the ESPP. The number of shares available for issuance under the ESPP will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 1 % of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year. The shares of common stock available for purchase pursuant to the ESPP are authorized but unissued shares of the Company’s common stock, shares of the Company’s common stock that the Company otherwise holds in treasury or shares of the Company’s common stock that were purchased on the open market in arms’ length transactions in accordance with applicable securities laws. Shares of the Company’s common stock will be offered for purchase under the ESPP as determined by the Compensation Committee through a series of successive offerings that each have a term of 24 months and consist of four consecutive purchase periods of six months each. Prior to the commencement of any future offering under the ESPP, the Compensation Committee may determine that the current offering shall end, may commence a new offering on the first day after the end of such terminal purchase period (or any desired later date), and may decide that future offerings will consist of one or more consecutive purchase periods, each to be of such duration as determined by the Compensation Committee; however, no offering will exceed 27 months and no purchase period will exceed one year . Each employee of the Company who (1) is an employee on the first date of any offering under the ESPP, (2) is customarily scheduled to work for more than 20 hours per week and more than five months per calendar year, and (3) meets such other criteria as may be determined by the Compensation Committee (consistent with Section 423 of the Internal Revenue Code of 1986, as amended), is eligible to participate in the ESPP for each purchase period within such offering. The purchase price per share of the Company’s common stock under the ESPP may not be less than, and will initially be equal to, the lesser of: (1) 85 % of the fair market value per share of the Company’s common stock on the first day of the offering, or (2) 85 % of the fair market value per share of the Company’s common stock on the date the purchase right is exercised, which will be the last day of the applicable purchase period. As of December 31, 2022, there were 3,649,046 shares of the Company’s common stock available for issuance and, effective January 1, 2023, an additional 782,572 shares of the Company’s common stock were added to the number of shares reserved for issuance under the ESPP in accordance with the terms of the ESPP. As of September 30, 2023, there were 4,336,261 shares of the Company’s common stock available for issuance under the ESPP. During the three and nine months ended September 30, 2023 and 2022, the Company recognized the following stock-based compensation expense (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2022 2023 2022 Stock-based compensation expense by type of award: Stock options $ 1,320 $ 835 $ 4,311 $ 2,841 Restricted stock and restricted stock units 2,699 1,038 7,251 3,512 Employee stock purchase plan 462 67 1,108 164 Total stock-based compensation expense included $ 4,481 $ 1,940 $ 12,670 $ 6,517 Stock-based compensation expense by line item: Research and development expenses $ 1,145 $ 447 $ 3,571 $ 1,722 General and administrative expenses 3,336 1,493 9,099 4,795 Total stock-based compensation expense included $ 4,481 $ 1,940 $ 12,670 $ 6,517 The following table sets forth the Company’s unrecognized stock-based compensation expense by type of award and the weighted-average period over which that expense is expected to be recognized (in thousands, except for years): As of September 30, 2023 Unrecognized Weighted- Type of award: Stock options $ 10,607 2.79 Restricted stock and restricted stock units $ 11,891 1.93 The following table is a summary of restricted stock activity during the nine months ended September 30, 2023: Shares of Restricted Stock Weighted- Unvested at December 31, 2022 183,095 $ 0.17 Granted — $ — Vested — $ — Forfeited — $ — Unvested at September 30, 2023 183,095 $ 0.17 The following table summarizes restricted stock unit activity during the nine months ended September 30, 2023: Shares Subject to Restricted Stock Units Weighted- Unvested at December 31, 2022 1,868,518 $ 5.37 Granted 1,772,243 $ 8.52 Vested ( 785,105 ) $ 5.40 Forfeited — $ — Unvested at September 30, 2023 2,855,656 $ 7.32 In 2019, the Company commenced issuing performance-based restricted stock units (“PRSU awards”). These awards have been issued to several of its employees and the shares subject to these PRSU awards will vest upon the Company achieving certain milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of the Company’s common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. In January 2019, the Company issued 221,600 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100 % of the PRSU awards vesting upon the achievement of three of the milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. As of December 31, 2022, 40,000 PRSU awards were forfeited and the Company recorded stock-based compensation expense of $ 1.4 million cumulatively from inception in 2019 through December 31, 2022. In January 2020, the Company issued 244,000 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100 % of the shares subject to the PRSU awards vesting upon the achievement of three of the milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. As of September 30, 2023, 10,500 PRSU awards were forfeited and the Company recorded stock-based compensation expense of $ 1.2 million cumulatively from inception in 2020 through September 30, 2023, including $( 454,000 ) during the nine months ended September 30, 2023. In January 2021, the Company issued 205,500 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100 % of the shares subject to the PRSU awards vesting upon the achievement of three of the milestones over a four-year period and 133.3 % of the shares subject to the PRSU awards vesting upon the achievement of all four milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. As of September 30, 2023, 10,000 PRSU awards were forfeited and the Company recorded stock-based compensation expense of $ 1.0 million cumulatively from inception in 2021 through September 30, 2023, including $ 103,000 d uring the nine months ended September 30, 2023. In January 2022, the Company issued 657,000 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100 % of the shares subject to the PRSU awards vesting upon the achievement of three of the milestones over a four-year period and 133.3 % of the shares subject to the PRSU awards vesting upon the achievement of all four milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. As of September 30, 2023, no PRSU awards were forfeited and the Company recorded stock-based compens ation expense of $ 3.7 million cumulatively from the PRSU awards that were granted in 2022 through September 30, 2023, including $ 1.7 million during the nine months ended September 30, 2023. In January 2023, the Company issued 920,000 PRSU awards to several of its employees, which are reflected in the above table summarizing restricted stock unit activity. The shares subject to these PRSU awards shall vest upon the Company achieving certain milestones, with 100 % of the shares subject to the PRSU awards vesting upon the achievement of three of the milestones over a four-year period and 133.3 % of the shares subject to the PRSU awards vesting upon the achievement of all four milestones over a four-year period, with any then-unvested portion of the PRSU awards to be cancelled on the four-year anniversary of the grant dates. As of September 30, 2023, no PRSU awards were forfeited and the Company recorded stock-based compensation expense of $ 3.7 million during the nine months ended September 30, 2023. The following table summarizes stock option activity during the three months ended September 30, 2023: Shares Subject to Stock Options Weighted- Weighted- Aggregate Intrinsic Value Options outstanding at December 31, 2022 5,157,857 $ 5.45 6.66 20,515,000 Granted 1,483,990 $ 9.31 Exercised ( 1,394,290 ) $ 4.59 Forfeited — Cancelled ( 3,750 ) $ 4.05 Options outstanding at September 30, 2023 5,243,807 $ 6.78 7.35 23,332,000 Options exercisable at September 30, 2023 2,380,983 $ 6.04 5.88 12,152,000 The Company received $ 6.6 million from exercises of stock options during the nine months ended September 30, 2023. The Company did no t receive any cash proceeds from exercises of stock options during the nine months ended September 30, 2022. Compensation cost for stock options granted to employees is based on the estimated grant date fair value and is recognized ratably over the vesting period of the applicable option. The estimated per share weighted average fair value of stock options granted to employees during the nine months ended September 30, 2023 was $ 9.31 . As stock-based compensation expense recognized is based on options ultimately expected to vest, the fair value of each employee option grant during the nine months ended September 30, 2023 was estimated on the date of grant using the Black-Scholes model with the following weighted average assumptions: Nine Months Ended September 30, 2023 Expected volatility 81.29 % Expected term (in years) 6.17 Risk-free interest rate 3.88 % Expected dividend yield 0 % Expected Volatility. The expected volatility rate used to value stock option grants is based on the volatility of the Company’s historical share prices. Expected Term . The Company elected to utilize the “simplified” method for “plain vanilla” options to value stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option. Risk-free Interest Rate . The risk-free interest rate assumption was based on zero-coupon U.S. Treasury instruments that had terms consistent with the expected term of the Company’s stock option grants. Expected Dividend Yield . The Company has never declared or paid any cash dividends and does not presently plan to pay cash dividends in the foreseeable future. Forfeitures are accounted for as actual forfeitures occur. Since the Company had a net operating loss carryforward as of September 30, 2023, no excess tax benefits for the tax deductions related to stock-based awards were recognized in the consolidated statements of operations.

Warrants

Warrants	9 Months Ended
	Sep. 30, 2023
Warrants and Rights Note Disclosure [Abstract]
Warrants	7. Warrants On June 14, 2017, the Company entered into a securities purchase agreement with certain accredited investors (the “Purchasers”) pursuant to which the Company sold an aggregate of 3,749,783 shares (the “Shares”) of its common stock and warrants to purchase up to an aggregate of 2,812,337 shares of its common stock to the Purchasers (the “Warrants”). The combined purchase price for one Share and one Warrant to purchase 0.75 shares of common stock was $ 1.15 . The closing of the issuance of the Shares and the Warrants occurred on June 19, 2017. The Warrants had an exercise price of $ 1.30 per share, subject to adjustment as provided therein, and became exercisable beginning on December 19, 2017 through December 19, 2022 . During the year ended December 31, 2022, 487,087 Warrants were exercised. The Warrants were exercised in full during the year ended December 31, 2022.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies On May 25, 2018, the Company entered into an office lease (the “Prior Lease”) with Kilroy Realty, L.P. The Prior Lease was for approximately 7,149 rentable square feet of space located at 12340 El Camino Real, Suite 250, San Diego, California 92130 (the “2018 Premises”). The 2018 Premises was the Company’s corporate headquarters. The Prior Lease commenced on November 1, 2018 and expired on January 31, 2022 (the “Prior Lease Term”). Monthly base rent payments due under the Prior Lease for the 2018 Premises were $ 27,000 , subject to annual increases of 3.0 % during the Prior Lease Term. Under the Prior Lease, the Company was responsible for certain charges for common area maintenance and other costs, including electricity and utility expenses and the Prior Lease provided for abatement of rent during certain periods and escalating rent payments throughout the Prior Lease Term. Rent expense was recorded on a straight-line basis over the life of the Lease and the difference between the rent expense and rent paid was recorded as deferred rent. The Prior Lease provided the Company with an option to extend the term of the lease for a period of three years beyond the Prior Lease Term, which was not exercised. On November 15, 2021, the Company entered into the Office Lease with One Pacific Heights. LLC. The Office Lease is for approximately 7,940 rentable square feet of space located at 9920 Pacific Heights Blvd, Suite 350, San Diego, California 92121 (the “Premises”). The Premises are now the Company’s corporate headquarters. Monthly base rent payments due under the Office Lease for the Premises are $ 28,187 , subject to annual increases of 3.0 % during the Term. Under the Office Lease, the Company is responsible for certain charges for common area maintenance and other costs, including utility expenses and the Office Lease provides for abatement of rent during certain periods and escalating rent payments throughout the Term. The Office Lease provides the Company with an option to extend the term of the Office Lease for a period of five years beyond the Term. If the option is exercised, the renewal term will be upon the same terms and conditions as the original Term, except that the base rent will be equal to the prevailing market rate as determined pursuant to the terms of the Office Lease.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	9. Subsequent Events The Company has evaluated all subsequent events through the date of the filing of this Quarterly Report on Form 10-Q with the SEC, to ensure that this filing includes appropriate disclosure of events both recognized in the consolidated financial statements as of September 30, 2023, and events which occurred subsequent to September 30, 2023, but were not recognized in the consolidated financial statements. The Company has determined that there were no subsequent events which required recognition, adjustment to or disclosure in the consolidated financial statements.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company	The Company Viking Therapeutics, Inc., a Delaware corporation, together with its subsidiary (the “Company”), is a clinical-stage biopharmaceutical company focused on the development of novel therapies for metabolic and endocrine disorders. In June of 2021, the Company formed an Australian subsidiary, Viking Therapeutics, PTY LTD, so as to be able to take advantage of certain research and development reimbursements available to local Australian based research and development companies that choose to do research in Australia. The Company was incorporated under the laws of the State of Delaware on September 24, 2012 and its principal executive offices are located in San Diego, California, with a subsidiary located in Adelaide, Australia.
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying consolidated balance sheet as of September 30, 2023, consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2023 and 2022, consolidated statements of stockholders’ equity for the three and nine months ended September 30, 2023 and 2022, and consolidated statements of cash flows for the nine months ended September 30, 2023 and 2022 are unaudited. These unaudited consolidated financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (the “SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the accompanying notes for the year ended December 31, 2022 contained in the Annual Report on Form 10-K filed by the Company with the SEC on February 10, 2023. The unaudited interim consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of September 30, 2023, the unaudited consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2023 and 2022, the unaudited consolidated statements of stockholders’ equity for the three and nine months ended September 30, 2023 and 2022 and the unaudited consolidated statements of cash flows for the nine months ended September 30, 2023 and 2022. The December 31, 2022 consolidated balance sheet included herein was derived from the audited consolidated financial statements, but it does not include all disclosures or notes required by GAAP for complete consolidated financial statements. The financial data and other information disclosed in these notes to the consolidated financial statements related to the three and nine months ended September 30, 2023 and 2022 are unaudited. Interim results are not necessarily indicative of results for an entire year.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying consolidated financial statements. Significant estimates made in preparing these consolidated financial statements relate to accounting for an operating lease and certain commitments. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents.
Investments Available-for-Sale	Investments Available-for-Sale Available-for-sale investments are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive loss. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. The amortization of premiums and accretion of discounts is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income (expense). The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured depository institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Prepaid Clinical Trial and Preclinical Study Costs	Prepaid Clinical Trial and Preclinical Study Costs Prepaid clinical trial and preclinical study costs represent advance payments by the Company for future clinical trial and preclinical study services to be performed by the clinical research organization and other research organizations. Such amounts are recognized as research and development expense as the related clinical trial and preclinical study services are performed.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) assets, and lease liability obligations are included in the Company’s consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liability obligations represent its obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company uses the implicit rate when readily determinable. The ROU asset also includes any lease payments made and excludes lease incentives and lease direct costs. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. Please refer to Note 4 for additional information.
Deferred Financing Costs	Deferred Financing Costs Deferred financing costs represent legal, accounting and other direct costs related to the Company’s efforts to raise capital through a public or private sale of the Company’s common stock. Costs related to the public sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are reclassified to additional paid-in-capital as a reduction of the proceeds. Costs related to the private sale of the Company’s common stock are deferred until the completion of the applicable offering, at which time such costs are amortized over the term of the applicable purchase agreement.
Revenue Recognition	Revenue Recognition The Company has not recorded any revenues since its inception. However, in the future, the Company may enter into collaborative research and licensing agreements, under which the Company could be eligible for payments made in the form of upfront license fees, research funding, cost reimbursement, contingent event-based payments and/or royalties. On January 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers and all related amendments (“ASC 606” or “the revenue standard”). ASC 606 is a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The revenue standard is based on the principle that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, ASC 606 provides that an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when (or as) the entity satisfies a performance obligation. The revenue standard also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, and costs to obtain or fulfill contracts. The Company will apply ASC 606 prospectively to all contracts.
Research and Development Expenses	Research and Development Expenses All costs of research and development are expensed in the period incurred. Research and development costs primarily consist of fees paid to CROs and clinical trial sites, employee and consultant related expenses, which include salaries, benefits and stock-based compensation for research and development personnel, external research and development expenses incurred pursuant to agreements with third-party manufacturing organizations, facilities costs, travel costs, dues and subscriptions, depreciation and materials used in preclinical studies, clinical trials and research and development. The Company estimates its preclinical study and clinical trial expenses based on the services it received pursuant to contracts with research institutions and CROs that conduct and manage preclinical studies and clinical trials on the Company’s behalf. Clinical trial-related contracts vary significantly in length, and may be for a fixed amount based on milestones or deliverables, a variable amount based on actual costs incurred, capped at a certain limit, or a combination of these elements. The Company accrues service fees based on work performed, which relies on estimates of total costs incurred based on milestones achieved, patient enrollment and other events. The majority of the Company’s service providers invoice the Company in arrears, and to the extent that amounts invoiced differ from its estimates of expenses incurred, the Company accrues for additional costs. The financial terms of these agreements vary from contract to contract and may result in uneven expenses and payment flows. Preclinical study and clinical trial expenses include: • fees paid to CROs, consultants and laboratories in connection with preclinical studies; • fees paid to CROs, clinical trial sites, investigators and consultants in connection with clinical trials; and • fees paid to contract manufacturers and service providers in connection with the production, testing and packaging of active pharmaceutical ingredients and drug materials for preclinical studies and clinical trials. Payments under some of these agreements depend on factors such as the milestones accomplished, including enrollment of certain numbers of patients, site initiation and the completion of clinical trial milestones. To date, the Company has not experienced any events requiring it to make material adjustments to its accruals for service fees. If the Company does not identify costs that it has begun to incur or if it underestimates or overestimates the level of services performed or the costs of these services, its actual expenses could differ from its estimates, which could materially affect its results of operations. Adjustments to the Company’s accruals are recorded as changes in estimates become evident. Furthermore, based on amounts invoiced to the Company by its service providers, the Company may also record payments made to those providers as prepaid expenses that will be recognized as expense in future periods as services are rendered. Related to the Company’s Australian subsidiary, Viking Therapeutics, PTY LTD, the Company is eligible under the AusIndustry Research and Tax Development Tax Incentive Program to obtain a cash amount from the Australian Taxation Office (ATO). The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply related to research and development expenditures in Australia. As there is no specific GAAP guidance related to how to record this research and development tax incentive, the Company looked to International Accounting Standard (IAS) 20 and determined that it will recognize these research and development tax incentives as contra research and development expense once received. The amounts are determined based on a cost-reimbursement basis, and the incentive is related to the Company’s research and development expenditures and is due regardless of whether any Australian tax is owed.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are expensed as incurred to general and administrative expense, as recoverability of such expenditures is uncertain.
Stock-Based Compensation	Stock-Based Compensation The Company generally uses the straight-line method to allocate compensation cost to reporting periods over each optionee’s requisite service period, which is generally the vesting period, and estimates the fair value of stock-based awards or restricted stock units to employees and directors using the Black-Scholes option-valuation model (the “Black-Scholes model”). The Black-Scholes model requires the input of subjective assumptions, including volatility, the expected term and the fair value of the underlying common stock on the date of grant, among other inputs. For restricted stock and restricted stock unit awards, the Company generally uses the straight-line method to allocate compensation cost to reporting periods over the holder’s requisite service period, which is generally the vesting period, and uses the fair value at grant date to value the awards. For restricted stock that vests upon the satisfaction of certain performance conditions, the Company recognizes stock-based compensation expense when it becomes probable that the performance conditions will be met. At the grant date, the Company determines the grant date fair value, as a publicly traded company, using the intrinsic value, or the closing price of the Company’s common stock on the date of grant. At the point where the criteria are deemed probable of being met, the Company records stock-based compensation with a cumulative catch-up expense in the period first recognized and then on a straight-line basis over the remaining period for which the performance criteria are expected to be completed. For the Company’s 2014 Employee Stock Purchase Plan (the “ESPP”), the Company generally recognizes compensation expense for the fair value of the purchase options, as measured on the grant date, and uses the graded vesting method to allocate this compensation cost to each purchase period within the related two-year offering period. As the ESPP also allows for up to one increase in contributions during each purchase period, as an employee elects to increase his or her contributions, the Company treats this as an accounting modification. The pre- and post-modification values are calculated on the date of the modification, and the incremental expense is then amortized over the remaining purchase periods.
Income Taxes	Income Taxes The Company accounts for its income taxes using the liability method whereby deferred tax assets and liabilities are determined based on temporary differences between the basis used for financial reporting and income tax reporting purposes. Deferred income taxes are provided based on the enacted tax rates in effect at the time such temporary differences are expected to reverse. A valuation allowance is provided for deferred tax assets if it is more likely than not that the Company will not realize those tax assets through future operations. FASB Accounting Standards Codification Topic 740-10, Income Taxes , clarifies the accounting for uncertainty in income taxes recognized in the Company’s consolidated financial statements in accordance with GAAP. Income tax positions must meet a more-likely-than-not recognition threshold to be recognized. Income tax positions that previously failed to meet the more-likely-than-not threshold are recognized in the first subsequent financial reporting period in which that threshold is met. Previously recognized tax positions that no longer meet the more-likely-than-not threshold are derecognized in the first subsequent financial reporting period in which that threshold is no longer met. The Company’s policy is to recognize interest and penalties accrued on any unrecognized tax benefits as a component of income tax expense.
Foreign Currency	Foreign Currency The financial statements of the Company’s foreign subsidiary whose functional currency is the local currency are translated into U.S. dollars for consolidation as follows: assets and liabilities at the exchange rate as of the balance sheet date, stockholders’ equity at the historical rates of exchange, and income and expense amounts at the average exchange rate for the period. Translation adjustments resulting from the translation of the subsidiaries’ accounts are included in “Accumulated other comprehensive loss” as equity in the consolidated balance sheet. Transactions denominated in currencies other than the applicable functional currency are converted to the functional currency at the exchange rate on the transaction date. At period end, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses resulting from foreign currency transactions are included within “Total other income, net” in the consolidated statement of operations. For the three months ended September 30, 2023 and 2022, foreign currency transaction loss amounted to $ 86,000 and $ 1,000 , respectively. For the nine months ended September 30, 2023 and 2022, foreign currency transaction loss amounted to $ 108,000 and $ 1,000 , respectively.
Comprehensive Loss	Comprehensive Loss The Company’s comprehensive loss consists of net loss, changes in unrealized gains and losses on its investments and foreign currency translation adjustments arising from the consolidation of the Company’s foreign subsidiary.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per share is calculated by dividing the net loss attributable 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 is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, the Company currently does not have any deemed common share equivalents; therefore, its basic and diluted net loss per share calculations are the same. The following table presents the computation of basic and diluted net loss per common share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Numerator: Net loss attributable to common stockholders $ ( 22,534 ) $ ( 15,773 ) $ ( 61,290 ) $ ( 49,308 ) Denominator: Weighted-average common shares outstanding 100,028,828 76,688,478 92,664,250 77,099,940 Less: Weighted-average shares subject to repurchase ( 183,095 ) ( 183,095 ) ( 183,095 ) ( 183,09 5 ) Denominator for basic and diluted net loss per share 99,845,733 76,505,383 92,481,155 76,916,845 Net loss per share: Basic and diluted $ ( 0.23 ) $ ( 0.21 ) $ ( 0.66 ) $ ( 0.64 ) Potentially dilutive securities that are not included in the calculation of diluted net loss per share because their effect is anti-dilutive are as follows (in common equivalent shares): As of September 30, 2023 2022 Common stock warrants — 14,587 Restricted stock units 2,855,656 1,770,582 Common stock subject to repurchase 183,095 183,095 Common stock options 5,243,807 5,107,857 8,282,558 7,076,121
Segments	Segments The Company operates in only one segment. Management uses cash flows as the primary measure to manage its business and does not segment its business for internal reporting or decision-making purposes.

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Computation of Basic and Diluted Net Loss per Common Share	The following table presents the computation of basic and diluted net loss per common share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Numerator: Net loss attributable to common stockholders $ ( 22,534 ) $ ( 15,773 ) $ ( 61,290 ) $ ( 49,308 ) Denominator: Weighted-average common shares outstanding 100,028,828 76,688,478 92,664,250 77,099,940 Less: Weighted-average shares subject to repurchase ( 183,095 ) ( 183,095 ) ( 183,095 ) ( 183,09 5 ) Denominator for basic and diluted net loss per share 99,845,733 76,505,383 92,481,155 76,916,845 Net loss per share: Basic and diluted $ ( 0.23 ) $ ( 0.21 ) $ ( 0.66 ) $ ( 0.64 )
Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share	Potentially dilutive securities that are not included in the calculation of diluted net loss per share because their effect is anti-dilutive are as follows (in common equivalent shares): As of September 30, 2023 2022 Common stock warrants — 14,587 Restricted stock units 2,855,656 1,770,582 Common stock subject to repurchase 183,095 183,095 Common stock options 5,243,807 5,107,857 8,282,558 7,076,121

Investments in Marketable Sec_2

Investments in Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Investments Classified As Available-For-Sale Securities	Investments classified as available-for-sale as of September 30, 2023 consisted of the following (in thousands): As of September 30, 2023 Amortized Gross (1) Gross (1) Aggregate Commercial paper (2) $ 90,828 $ 1 $ ( 1 ) $ 90,828 Corporate debt securities (2) 98,539 26 ( 226 ) 98,339 Government debt securities (2) 150,228 1 ( 340 ) 149,889 $ 339,595 $ 28 $ ( 567 ) $ 339,056 Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At September 30, 2023, there were 10 securities in an unrealized gain position and there were 97 securities in an unrealized loss position. The unrealized gains were less than $ 19,000 individually and $ 29,000 in the aggregate. The unrealized losses were less than $ 48,000 individually and $ 567,000 in the aggregate. The Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell these investments before recovery of their amortized cost basis, which may be at maturity. The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. (2) At September 30, 2023, none of these securities were classified as cash and cash equivalents on the Company’s consolidated balance sheet, and none o f the corporate debt securities were scheduled to mature outside of one year at the time of purchase. Investments classified as available-for-sale as of December 31, 2022 consisted of the following (in thousands): As of December 31, 2022 Amortized Gross (1) Gross (1) Aggregate Commercial paper (2) $ 43,780 $ — $ — $ 43,780 Corporate debt securities (2) 72,183 — ( 824 ) 71,359 Government debt securities (2) 3,732 — ( 18 ) 3,714 $ 119,695 $ — $ ( 842 ) $ 118,853 Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At December 31, 2022, there were no securities in an unrealized gain position and 39 securities in an unrealized loss position. The unrealized losses were less than $ 124,000 individually and $ 842,000 in the aggregate. 22 of these securities have been in a continuous unrealized loss or unrealized gain position for more than 12 months. The Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell these investments before recovery of their amortized cost basis, which may be at maturity. The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. (2) At December 31, 2022, none of these securities were classified as cash and cash equivalents on the Company’s consolidated balance sheet, and none of the corporate debt securities were scheduled to mature outside of one year.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Summary of Fair Values of Financial Instruments	The fair values of the Company’s financial instruments are presented below (in thousands): Fair Value Measurements at September 30, 2023 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: $ 32,844 $ 19,398 $ 13,446 $ — Short-term investments Commercial paper, available-for-sale 90,828 — 90,828 — Corporate debt securities, available-for-sale 98,339 — 98,339 — Government debt securities, available-for-sale 149,889 — 149,889 — Total financial assets $ 371,900 $ 19,398 $ 352,502 $ — Fair Value Measurements at December 31, 2022 Total Level 1 Level 2 Level 3 Financial assets carried at fair value: Cash equivalents: $ 16,243 $ 5,617 $ 10,626 $ — Short-term investments Commercial paper, available-for-sale 43,780 — 43,780 — Corporate debt securities, available-for-sale 71,359 — 71,359 — Government debt securities, available-for-sale 3,714 — 3,714 — Total financial assets $ 135,096 $ 5,617 $ 129,479 $ —

Operating Leases - ROU Assets_2

Operating Leases - ROU Assets and Lease Liability Obligations (Tables)	9 Months Ended
	Sep. 30, 2023
Schedule of Right-of-use Assets and Lease Liabilities	The Company has only one operating lease (the “Office Lease”), which is for office space under a lease that commenced on March 1, 2022 and expires on July 31, 2027 (the “Term”). Below is a summary of the Company’s ROU assets and lease liabilities as of September 30, 2023 and December 31, 2022 (in thousands, except for years and %): September 30, 2023 December 31, 2022 Right-of-use assets $ 1,200 $ 1,418 Lease liability obligations, current $ 319 $ 304 Lease liability obligations, less current portion 1,018 1,260 Total lease liability obligations $ 1,337 $ 1,564 Weighted-average remaining lease term 3.83 years 4.58 years Weighted-average discount rate 3.00 % 3.00 %
Office Space [Member]
Schedule of Future Minimum Lease Payments	Approximate future minimum lease payments for the Company’s ROU assets over the remaining lease period as of September 30, 2023 are as follows (in thousands): Remainder of 2023 $ 88 2024 357 2025 368 2026 379 2027 227 Total minimum lease payments $ 1,419 Less: amount representing interest $ ( 82 ) Total lease liability obligations $ 1,337

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2023
Summary of Stock-based Compensation Expense Recognized	During the three and nine months ended September 30, 2023 and 2022, the Company recognized the following stock-based compensation expense (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2022 2023 2022 Stock-based compensation expense by type of award: Stock options $ 1,320 $ 835 $ 4,311 $ 2,841 Restricted stock and restricted stock units 2,699 1,038 7,251 3,512 Employee stock purchase plan 462 67 1,108 164 Total stock-based compensation expense included $ 4,481 $ 1,940 $ 12,670 $ 6,517 Stock-based compensation expense by line item: Research and development expenses $ 1,145 $ 447 $ 3,571 $ 1,722 General and administrative expenses 3,336 1,493 9,099 4,795 Total stock-based compensation expense included $ 4,481 $ 1,940 $ 12,670 $ 6,517
Schedule of Unrecognized Stock-based Compensation Expense by Type of Award and Weighted-average Recognition Period	The following table sets forth the Company’s unrecognized stock-based compensation expense by type of award and the weighted-average period over which that expense is expected to be recognized (in thousands, except for years): As of September 30, 2023 Unrecognized Weighted- Type of award: Stock options $ 10,607 2.79 Restricted stock and restricted stock units $ 11,891 1.93
Summary of Stock Option Activity	The following table summarizes stock option activity during the three months ended September 30, 2023: Shares Subject to Stock Options Weighted- Weighted- Aggregate Intrinsic Value Options outstanding at December 31, 2022 5,157,857 $ 5.45 6.66 20,515,000 Granted 1,483,990 $ 9.31 Exercised ( 1,394,290 ) $ 4.59 Forfeited — Cancelled ( 3,750 ) $ 4.05 Options outstanding at September 30, 2023 5,243,807 $ 6.78 7.35 23,332,000 Options exercisable at September 30, 2023 2,380,983 $ 6.04 5.88 12,152,000 The Company received $ 6.6 million from exercises of stock options during the nine months ended September 30, 2023. The Company did no t receive any cash proceeds from exercises of stock options during the nine months ended September 30, 2022.
Schedule of Weighted Average Assumptions using Black-Scholes Option Pricing Model	the fair value of each employee option grant during the nine months ended September 30, 2023 was estimated on the date of grant using the Black-Scholes model with the following weighted average assumptions: Nine Months Ended September 30, 2023 Expected volatility 81.29 % Expected term (in years) 6.17 Risk-free interest rate 3.88 % Expected dividend yield 0 %
Restricted stock [Member]
Summary of Shares Granted and Stock Activity	The following table is a summary of restricted stock activity during the nine months ended September 30, 2023: Shares of Restricted Stock Weighted- Unvested at December 31, 2022 183,095 $ 0.17 Granted — $ — Vested — $ — Forfeited — $ — Unvested at September 30, 2023 183,095 $ 0.17
Restricted stock units [Member]
Summary of Shares Granted and Stock Activity	The following table summarizes restricted stock unit activity during the nine months ended September 30, 2023: Shares Subject to Restricted Stock Units Weighted- Unvested at December 31, 2022 1,868,518 $ 5.37 Granted 1,772,243 $ 8.52 Vested ( 785,105 ) $ 5.40 Forfeited — $ — Unvested at September 30, 2023 2,855,656 $ 7.32

Organization and Summary of S_4

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Segment	Sep. 30, 2022 USD ($)
Accounting Policies [Abstract]
Date of incorporation			Sep. 24, 2012
State code of incorporation			DE
Highly liquid investments maturities			three months or less
Foreign currency translation loss | $	$ 86,000	$ 1,000	$ 108,000	$ 1,000
Number of operating segment | Segment			1

Organization and Summary of S_5

Organization and Summary of Significant Accounting Policies - Schedule of Computation of Basic and Diluted Net Loss per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator:
Net loss attributable to common stockholders	$ (22,534)	$ (15,773)	$ (61,290)	$ (49,308)
Denominator:
Weighted-average common shares outstanding	100,028,828	76,688,478	92,664,250	77,099,940
Less: Weighted-average shares subject to repurchase	(183,095)	(183,095)	(183,095)	(18,309)
Denominator for basic net loss per share	99,845,733	76,505,383	92,481,155	76,916,845
Denominator for diluted net loss per share	99,845,733	76,505,383	92,481,155	76,916,845
Net loss per share:
Basic	$ (0.23)	$ (0.21)	$ (0.66)	$ (0.64)
Diluted	$ (0.23)	$ (0.21)	$ (0.66)	$ (0.64)

Organization and Summary of S_6

Organization and Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share (Detail) - shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	8,282,558	7,076,121
Common stock warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	0	14,587
Restricted stock units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	2,855,656	1,770,582
Common stock subject to repurchase [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	183,095	183,095
Common stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded in calculation of diluted net loss per share	5,243,807	5,107,857

Investments in Marketable Sec_3

Investments in Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Abstract]
Proceeds from sales of available-for-sale securities	$ 0	$ 0	$ 0

Investments in Marketable Sec_4

Investments in Marketable Securities - Summary of Investments Classified As Available-For-Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 339,595	$ 119,695
Gross Unrealized Gains	28
Gross Unrealized Losses	(567)	(842)
Aggregate Estimated Fair Value	339,056	118,853
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	90,828	43,780
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)
Aggregate Estimated Fair Value	90,828	43,780
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	98,539	72,183
Gross Unrealized Gains	26
Gross Unrealized Losses	(226)	(824)
Aggregate Estimated Fair Value	98,339	71,359
Government debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	150,228	3,732
Gross Unrealized Gains	1
Gross Unrealized Losses	(340)	(18)
Aggregate Estimated Fair Value	$ 149,889	$ 3,714

Investments in Marketable Sec_5

Investments in Marketable Securities - Summary of Investments Classified As Available-For-Sale Securities (Parenthetical) (Detail)	Sep. 30, 2023 USD ($) Security	Dec. 31, 2022 USD ($) Security
Schedule of Available-for-sale Securities [Line Items]
Number of securities in unrealized gain position | Security	10	0
Number of securities in unrealized loss position | Security	97	39
Unrealized losses, aggregate	$ 567,000	$ 842,000
Short-term investments – available for sale	339,056,000	118,853,000
Unrealized gains, aggregate	28,000
Cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments – available for sale	0	0
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses, aggregate	1,000
Short-term investments classified as available-for-sale, noncurrent	0	0
Unrealized gains, aggregate	1,000
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses, aggregate	226,000	824,000
Short-term investments classified as available-for-sale, noncurrent	0	0
Unrealized gains, aggregate	26,000
Government debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses, aggregate	340,000	18,000
Short-term investments classified as available-for-sale, noncurrent	0	0
Unrealized gains, aggregate	1,000
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains, individually	19,000
Unrealized losses, individually	48,000	124,000
Unrealized losses, aggregate	567,000	$ 842,000
Unrealized gains, aggregate	$ 29,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial assets carried at fair value:
Cash equivalents, fair value disclosure	$ 32,844	$ 16,243
Short-term investments, available for sale	339,056	118,853
Total financial assets	371,900	135,096
Level 1 [Member]
Financial assets carried at fair value:
Cash equivalents, fair value disclosure	19,398	5,617
Total financial assets	19,398	5,617
Level 2 [Member]
Financial assets carried at fair value:
Cash equivalents, fair value disclosure	13,446	10,626
Total financial assets	352,502	129,479
Commercial paper, available-for-sale [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	90,828	43,780
Commercial paper, available-for-sale [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	90,828	43,780
Corporate debt securities, available-for-sale [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	98,339	71,359
Corporate debt securities, available-for-sale [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	98,339	71,359
Government debt securities [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	149,889	3,714
Government debt securities [Member] | Level 2 [Member]
Financial assets carried at fair value:
Short-term investments, available for sale	$ 149,889	$ 3,714

Operating Leases - ROU Assets_3

Operating Leases - ROU Assets and Lease Liability Obligations - Additional Information (Detail)			3 Months Ended		9 Months Ended
	Nov. 15, 2021	May 25, 2018	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Lease	Sep. 30, 2022 USD ($)
Lessee Lease Description [Line Items]
Operating lease number of leases | Lease					1
Lease Commencement Date					Mar. 01, 2022
Lease expiration date					Jul. 31, 2027
Operating lease expense | $			$ 84,000	$ 88,000	$ 255,000	$ 257,000
Operating lease option to extend term	5 years	3 years
Office Lease [Member]
Lessee Lease Description [Line Items]
Operating lease, option to extend					true
Operating lease option to extend term					5 years
Operating lease, option to extend, description					The Office Lease provides the Company with an option to extend the term of the Office Lease for a period of five years beyond the Term.

Operating Leases - ROU Assets_4

Operating Leases - ROU Assets and Lease Liability Obligations - Schedule of Right-of-use Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Lessee Disclosure [Abstract]
Right-of-use assets	$ 1,200	$ 1,418
Lease liability, current	319	304
Lease liability, net of current portion	1,018	1,260
Total lease liability obligations	$ 1,337	$ 1,564
Weighted-average remaining lease term	3 years 9 months 29 days	4 years 6 months 29 days
Weighted-average discount rate	3%	3%

Operating Leases - ROU Assets_5

Operating Leases - ROU Assets and Lease Liability Obligations - Schedule of Future Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Lessee Lease Description [Line Items]
Total lease liability obligations	$ 1,337	$ 1,564
Office Space [Member]
Lessee Lease Description [Line Items]
Remainder of 2023	88
2024	357
2025	368
2026	379
2027	227
Total minimum lease payments	1,419
Less: amount representing interest	(82)
Total lease liability obligations	$ 1,337

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail)

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

15 Months Ended

19 Months Ended

24 Months Ended

33 Months Ended

Jul. 26, 2023 USD ($)

Apr. 03, 2023 USD ($) $ / shares shares

Mar. 18, 2022 USD ($)

Jul. 28, 2021 USD ($)

Mar. 17, 2020 USD ($)

Sep. 28, 2017 USD ($) shares

May 31, 2015 USD ($) $ / shares shares

Feb. 28, 2014 Tranche $ / shares shares

Sep. 30, 2023 USD ($) $ / shares shares

Sep. 30, 2022 USD ($)

Dec. 31, 2017 USD ($) shares

Sep. 30, 2023 USD ($) $ / shares shares

Sep. 30, 2022 USD ($) shares

Dec. 31, 2022 $ / shares shares

Dec. 31, 2021 shares

Dec. 31, 2020 shares

Dec. 31, 2019 shares

Dec. 31, 2018 shares

Dec. 31, 2016 USD ($)

Sep. 30, 2023 $ / shares shares

Mar. 17, 2022 shares

Sep. 30, 2023 USD ($) $ / shares shares

Feb. 20, 2014 USD ($)

Equity [Line Items]

Preferred stock, shares authorized

10,000,000

10,000,000

10,000,000

10,000,000

10,000,000

Preferred stock, par value | $ / shares

$ 0.00001

$ 0.00001

$ 0.00001

$ 0.00001

$ 0.00001

Preferred stock, shares outstanding

0

0

0

0

0

Common stock, shares authorized

300,000,000

300,000,000

300,000,000

300,000,000

300,000,000

Common stock, par value | $ / shares

$ 0.00001

$ 0.00001

$ 0.00001

$ 0.00001

$ 0.00001

Number of common stock for issuance in exchange for future services from founders

1,000,000

Common stock price per share | $ / shares

$ 0.01

Number of tranches | Tranche

2

Unrecognized compensation expense | $

$ 62,000

$ 168,000

Common stock shares repurchased

633,810

Repurchase of common stock from stockholders, per share | $ / shares

$ 0.00001

Remaining number of repurchased shares

366,190

Common stock sold

0

0

0

0

0

0

Shares issued under ESPP

95,357

43,800

ATM Agreement [Member]

Equity [Line Items]

Gross proceeds from common stock issuance | $

$ 200,000,000

Shelf registration statement expiry date

Jul. 26, 2026

April 2023 Offering [Member]

Equity [Line Items]

Common stock sold

19,828,300

Proceeds from issuance of common stock net | $

$ 270,000,000

Offering price per share | $ / shares

$ 14.5

Sale of stock, shares issued

2,586,300

2021 Shelf Registration Statement [Member]

Equity [Line Items]

Maximum amount of Securities that can be offered | $

$ 600,000,000

Shelf registration statement expiry date

Jul. 26, 2023

Common Stock [Member]

Equity [Line Items]

Common stock sold

20,006,504

Repurchase of common stock (in shares)

2,193,251

Common Stock [Member] | ATM Agreement [Member]

Equity [Line Items]

Common stock sold

1,587,404

Shelf registration statement expiry date

Jul. 26, 2023

Proceeds from issuance of common stock net | $

$ 13,600,000

Repurchase Program [Member]

Equity [Line Items]

Repurchase of common stock (in shares)

1,464,217

Stock repurchase program, additional maturity period

2 years

New Repurchase Program [Member]

Equity [Line Items]

Repurchase of common stock (in shares)

729,034

Stock repurchase program, additional maturity period

2 years

Maximum [Member] | Repurchase Program [Member]

Equity [Line Items]

Purchase of common stock and warrants | $

$ 50,000,000

Maximum [Member] | New Repurchase Program [Member]

Equity [Line Items]

Purchase of common stock and warrants | $

$ 50,000,000

LPC [Member] | Commitment Purchase Agreement [Member] | Common Stock [Member] | Registration Rights Agreement [Member]

Equity [Line Items]

Common stock purchase agreement term

30 months

Common stock issued as consideration for commitment

100,000

Gross proceeds from common stock issuance | $

$ 802,000

Common stock sold

343,051

LPC [Member] | Maximum [Member] | Commitment Purchase Agreement [Member] | Common Stock [Member] | Registration Rights Agreement [Member]

Equity [Line Items]

Total of purchase agreement and potential aggregate future purchases | $

$ 15,000,000

Common stock to be sold, subject to certain limitations

75,000

Total purchase proceeds per purchase date, subject to certain limitations | $

$ 1,000,000

LPC [Member] | Minimum [Member] | Commitment Purchase Agreement [Member] | Common Stock [Member] | Registration Rights Agreement [Member]

Equity [Line Items]

Percentage of shares may not sell if it is beneficial owning

4.99%

Tranche One [Member]

Equity [Line Items]

Number of common stock for issuance in exchange for future services from founders

500,000

Remaining number of repurchased shares

183,095

Stock compensation expense | $

$ 0

$ 0

$ 0

$ 0

$ 31,000

Tranche Two [Member]

Equity [Line Items]

Number of common stock for issuance in exchange for future services from founders

500,000

Remaining number of repurchased shares

183,095

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

21 Months Ended

33 Months Ended

45 Months Ended

48 Months Ended

Jan. 31, 2023 Milestone shares

Jan. 31, 2022 Milestone shares

Jan. 31, 2021 Milestone shares

Jan. 31, 2020 Milestone shares

Jan. 31, 2019 Milestone shares

Sep. 30, 2023 USD ($) shares

Sep. 30, 2022 USD ($)

Sep. 30, 2023 USD ($) Period $ / shares shares

Sep. 30, 2022 USD ($)

Dec. 31, 2022 shares

Dec. 31, 2019

Sep. 30, 2023 USD ($) shares

Sep. 30, 2023 USD ($) shares

Sep. 30, 2023 USD ($) shares

Dec. 31, 2022 USD ($) shares

Jan. 01, 2023 shares

Apr. 28, 2015 shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation | $

$ 4,481,000

$ 1,940,000

$ 12,670,000

$ 6,517,000

Forfeited awards

0

Cash proceeds from exercises of stock options | $

$ 6,600,000

$ 0

Weighted average fair value of stock options granted to employees | $ / shares

$ 9.31

Excess tax benefit from stock-based awards | $

$ 0

Performance Based Restricted Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Milestone achievement period

4 years

4 years

4 years

4 years

4 years

4 years

Issuance of performance based award

920,000

657,000

205,500

244,000

221,600

Percentage of shares vested upon achievement of certain milestone

100%

100%

Number of milestones to be achieve | Milestone

3

3

Forfeited awards

40,000

Performance Based Restricted Stock Units [Member] | PRSU Awards Vesting Upon the Achievement of Three of the Milestones Over a Four Year Period [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of shares vested upon achievement of certain milestone

100%

100%

100%

Number of milestones to be achieve | Milestone

3

3

3

Performance Based Restricted Stock Units [Member] | PRSU Awards Vesting Upon the Achievement of Four of the Milestones Over a Four Year Period [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of shares vested upon achievement of certain milestone

133.30%

Number of milestones to be achieve | Milestone

4

Performance Based Restricted Stock Units [Member] | PRSU Awards Vesting Upon the Achievement of All Four of the Milestones Over a Four Year Period [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of shares vested upon achievement of certain milestone

133.30%

133.30%

Number of milestones to be achieve | Milestone

4

4

Performance Based Restricted Stock Units [Member] | January 2019 [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation | $

$ 1,400,000

Performance Based Restricted Stock Units [Member] | January 2020 [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation | $

$ (454,000)

$ 1,200,000

Forfeiture of performance based award

10,500

Performance Based Restricted Stock Units [Member] | January 2021 [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation | $

$ 103,000

$ 1,000,000

Forfeiture of performance based award

10,000

Performance Based Restricted Stock Units [Member] | January 2022 [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation | $

$ 1,700,000

$ 3,700,000

Forfeiture of performance based award

0

Performance Based Restricted Stock Units [Member] | January 2023 [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation | $

$ 3,700,000

Forfeiture of performance based award

0

2014 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock reserved for issuance, description

Initially, a total of 1,527,770 shares of the Company’s common stock were reserved for issuance pursuant to the 2014 Plan. The number of shares available for issuance under the 2014 Plan will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 3.5% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year.

Percentage of common stock outstanding to increase shares reserved for issuance

3.50%

Common stock reserved for future issuance

6,228,558

6,228,558

1,527,770

Additional number of shares of common stock reserved for issuance

2,739,004

Number of common shares available for grant

6,531,433

6,531,433

6,531,433

6,531,433

6,531,433

2014 ESPP [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock reserved for issuance, description

The number of shares available for issuance under the ESPP will, unless otherwise determined by the Company’s Board of Directors or the Compensation Committee, be automatically increased on January 1 of each year commencing on January 1, 2016 and ending on (and including) January 1, 2024, in an amount equal to 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year.

Percentage of common stock outstanding to increase shares reserved for issuance

1%

Common stock reserved for future issuance

3,649,046

3,649,046

458,331

Additional number of shares of common stock reserved for issuance

782,572

Number of common shares available for grant

4,336,261

4,336,261

4,336,261

4,336,261

4,336,261

Duration of employee stock purchase plan as determined by the compensation committee

24 months

Duration for offering period, employee stock purchase plan

6 months

Employee stock purchase plan, number of purchase periods | Period

4

Maximum duration for purchase under employee stock purchase plan

1 year

Maximum duration of employee stock purchase plan

27 months

Percentage of purchase of common stock

85%

Percentage of common stock on the date of purchase

85%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	$ 4,481	$ 1,940	$ 12,670	$ 6,517
Research and development expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	1,145	447	3,571	1,722
General and administrative expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	3,336	1,493	9,099	4,795
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	1,320	835	4,311	2,841
Restricted stock and restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	2,699	1,038	7,251	3,512
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense included in expenses	$ 462	$ 67	$ 1,108	$ 164

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Unrecognized Stock-based Compensation Expense by Type of Award and Weighted-average Recognition Period (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2023	May 31, 2015	Feb. 20, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense, Net of Estimated Forfeitures		$ 62,000	$ 168,000
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense, Net of Estimated Forfeitures	$ 10,607
Weighted-average Recognition Period	2 years 9 months 14 days
Restricted stock and restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense, Net of Estimated Forfeitures	$ 11,891
Weighted-average Recognition Period	1 year 11 months 4 days

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted stock [Member]	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Unvested, Beginning balance | shares	183,095
Shares, Granted | shares	0
Shares, Vested | shares	0
Shares, Forfeited | shares	0
Shares, Unvested, Ending balance | shares	183,095
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 0.17
Weighted-Average Grant Date Fair Value, Granted | $ / shares	0
Weighted-Average Grant Date Fair Value, Vested | $ / shares	0
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	0
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 0.17

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) - Restricted stock units [Member]	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Unvested, Beginning balance | shares	1,868,518
Shares, Granted | shares	1,772,243
Shares, Vested | shares	(785,105)
Shares, Unvested, Ending balance | shares	2,855,656
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 5.37
Weighted-Average Grant Date Fair Value, Granted | $ / shares	8.52
Weighted-Average Grant Date Fair Value, Vested | $ / shares	5.4
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 7.32

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Options outstanding beginning balance, Shares Subject to Stock Options	5,157,857
Granted, Shares Subject to Stock Options	1,483,990
Exercised, Shares Subject to Stock Options	(1,394,290)
Forfeited, Shares Subject to Stock Options	0
Cancelled, Shares Subject to Stock Options	(3,750)
Options outstanding ending balance, Shares Subject to Stock Options	5,243,807	5,157,857
Options exercisable, Shares Subject to Stock Options	2,380,983
Options outstanding beginning balance, Weighted-Average Exercise Price	$ 5.45
Granted, Weighted-Average Exercise Price	9.31
Exercised, Weighted-Average Exercise Price	4.59
Cancelled, Weighted-Average Exercise Price	4.05
Options outstanding ending balance, Weighted-Average Exercise Price	6.78	$ 5.45
Options exercisable, Weighted-Average Exercise Price	$ 6.04
Options outstanding, Weighted-Average Remaining Contractual Term	7 years 4 months 6 days	6 years 7 months 28 days
Options exercisable, Weighted-Average Remaining Contractual Term	5 years 10 months 17 days
Options outstanding, Aggregate Intrinsic Value	$ 23,332,000	$ 20,515,000
Options exercisable, Aggregate Intrinsic Value	$ 12,152,000

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Weighted Average Assumptions using Black-Scholes Option Pricing Model (Detail)	9 Months Ended
	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	81.29%
Expected term (in years)	6 years 2 months 1 day
Risk-free interest rate	3.88%
Expected dividend yield	0%

Warrants (Additional Informatio

Warrants (Additional Information) (Details) - $ / shares		9 Months Ended	12 Months Ended
	Jun. 14, 2017	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Common stock sold		0	0	0	0	0	0
Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Exercise price of warrant	$ 1.15
Warrants exercised			487,087
Private Placement and Registered Direct Offering [Member] | Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Number of warrants issued for common stock	0.75
Exercise price of warrant	$ 1.3
Warrants exercisable date		Dec. 19, 2017
Warrants expiry date		Dec. 19, 2022
Common Stock [Member]
Class of Warrant or Right [Line Items]
Common stock sold		20,006,504
Common Stock [Member] | Private Placement and Registered Direct Offering [Member] | Securities Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Common stock sold	3,749,783
Common Stock [Member] | Private Placement and Registered Direct Offering [Member] | Securities Purchase Agreement [Member] | Maximum [Member]
Class of Warrant or Right [Line Items]
Warrants sold	2,812,337

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)			3 Months Ended		9 Months Ended
	Nov. 15, 2021 USD ($) ft²	May 25, 2018 USD ($) ft²	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Commitments And Contingencies [Line Items]
Lease Commencement Date					Mar. 01, 2022
Lease expiration date					Jul. 31, 2027
Monthly base rent payments			$ 84,000	$ 88,000	$ 255,000	$ 257,000
Operating lease option to extend term	5 years	3 years
Office Lease [Member]
Commitments And Contingencies [Line Items]
Operating lease option to extend term					5 years
California [Member] | Office Lease [Member]
Commitments And Contingencies [Line Items]
Area of lease premises | ft²	7,940	7,149
Lease Commencement Date		Nov. 01, 2018
Lease expiration date		Jan. 31, 2022
Monthly base rent payments	$ 28,187	$ 27,000
Percentage of rent increase under lease	3%	3%