Satsuma Pharmaceuticals (STSA) 10-K 28 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 22, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Registrant Name	Satsuma Pharmaceuticals, Inc.
Entity Central Index Key	0001692830
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 93.3
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	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity File Number	001-39041
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3039831
Entity Address, Address Line One	400 Oyster Point Boulevard
Entity Address, Address Line Two	Suite 221
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	410-3200
Document Annual Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	STSA
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		33,152,498
Auditor Name	KPMG LLP
Auditor Location	San Diego, California
Auditor Firm ID	185
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement relating to the 2023 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. The proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2022.

Balance Sheets

Balance Sheets - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Assets
Cash and cash equivalents	$ 16,429,000	$ 15,835,000
Short-term marketable securities	36,052,000	77,315,000
Prepaid expenses and other current assets	2,328,000	6,698,000
Total current assets	54,809,000	99,848,000
Property and equipment, net	0	6,792,000
Operating lease right-of-use asset	108,000
Long-term marketable securities		2,620,000
Other non-current assets	22,000	572,000
Total assets	54,939,000	109,832,000
Liabilities
Accounts payable	1,911,000	1,469,000
Accrued and other current liabilities	6,066,000	5,943,000
Operating lease liability	138,000
Debt		1,080,000
Total current liabilities	8,115,000	8,492,000
Total liabilities	8,115,000	8,492,000
Commitments and Contingencies (Note 5)
Stockholders’ equity
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of December 31, 2022 and December 31, 2021; no shares issued and outstanding as of December 31, 2022 and December 31, 2021
Common stock, $0.0001 par value, 300,000,000 shares authorized as of December 31, 2022 and December 31, 2021, respectively; 33,152,498 shares and 31,545,564 shares issued and outstanding as of December 31, 2022 and December 31, 2021, respectively	3,000	3,000
Additional paid-in-capital	258,642,000	243,115,000
Accumulated other comprehensive loss	(30,000)	(42,000)
Accumulated deficit	(211,791,000)	(141,736,000)
Total stockholders’ equity	46,824,000	101,340,000
Total liabilities, preferred stock and stockholders' equity	$ 54,939,000	$ 109,832,000

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	33,152,498	31,545,564
Common stock, shares outstanding	33,152,498	31,545,564

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating expenses
Research and development	$ 44,092,000	$ 37,635,000
General and administrative	15,126,000	13,531,000
Impairment loss	11,729,000	0
Total operating expenses	70,947,000	51,166,000
Loss from operations	(70,947,000)	(51,166,000)
Interest income	905,000	157,000
Interest expense	(13,000)	(163,000)
Net loss	(70,055,000)	(51,172,000)
Unrealized gain (loss) on marketable securities	12,000	(71,000)
Comprehensive loss	$ (70,043,000)	$ (51,243,000)
Net loss per share attributable to common stockholders, basic	$ (2.19)	$ (1.75)
Net loss per share attributable to common stockholders, diluted	$ (2.19)	$ (1.75)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic	32,024,991	29,174,386
Weighted-average shares used in computing net loss per share attributable to common stockholders, diluted	32,024,991	29,174,386

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning balance at Dec. 31, 2020	$ 71,936	$ 2	$ 162,469	$ (90,564)	$ 29
Beginning balance, Shares at Dec. 31, 2020		17,436,978
Issuance of common stock upon exercise of stock options	8		8
Issuance of common stock upon exercise of stock options, Shares		7,932
Issuance of common stock, net of issuance costs	75,215	$ 1	75,214
Issuance of common stock, net of issuance costs, Shares		14,084,507
Stock-based compensation	5,364		5,364
Issuance of common stock upon purchases under employee share purchase plan	60		60
Issuance of common stock upon purchases under employee share purchase plan, Shares		16,147
Other comprehensive income (loss)	(71)				(71)
Net loss	(51,172)			(51,172)
Ending balance at Dec. 31, 2021	101,340	$ 3	243,115	(141,736)	(42)
Ending Balance, Shares at Dec. 31, 2021		31,545,564
Issuance of common stock, net of issuance costs	9,700		9,700
Issuance of common stock, net of issuance costs, Shares		1,538,461
Stock-based compensation	5,705		5,705
Issuance of common stock upon purchases under employee share purchase plan	122		122
Issuance of common stock upon purchases under employee share purchase plan, Shares		68,473
Other comprehensive income (loss)	12				12
Net loss	(70,055)			(70,055)
Ending balance at Dec. 31, 2022	$ 46,824	$ 3	$ 258,642	$ (211,791)	$ (30)
Ending Balance, Shares at Dec. 31, 2022		33,152,498

Statements of Stockholders' E_2

Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Private Placement
Common stock issuance costs		$ 4,785
At-The-Market Offering
Common stock issuance costs	$ 300

Statements of Cash Flows

Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net loss	$ (70,055,000)	$ (51,172,000)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	510,000	393,000
Amortization of operating lease right-of-use asset	173,000
Loss on disposal of property and equipment		618,000
Non-cash interest expense, and amortization of debt discount and issuance costs	3,000	48,000
Amortization of premiums / (accretion of discounts), net on marketable securities	52,000	651,000
Stock-based compensation	5,705,000	5,364,000
Impairment loss	11,729,000	0
Changes in assets and liabilities
Prepaid expenses and other assets	2,687,000	(946,000)
Accounts payable	466,000	(1,212,000)
Accrued and other current liabilities	(2,643,000)	3,268,000
Operating lease liabilities, net	(143,000)
Other non-current liabilities		(9,000)
Net cash used in operating activities	(51,516,000)	(42,997,000)
Cash flows from investing activities
Purchases of marketable securities	(47,772,000)	(88,620,000)
Proceeds from maturities of marketable securities	91,615,000	39,873,000
Purchases of property and equipment	(472,000)	(2,030,000)
Net cash provided by (used in) investing activities	43,371,000	(50,777,000)
Cash flows from financing activities
Repayment of debt	(1,083,000)	(2,000,000)
Proceeds from private placement financing, net of issuance costs		75,215,000
Proceeds from At-the-Market offering, net of issuance costs	9,700,000
Proceeds from issuance of common stock under employee plans	122,000	68,000
Net cash provided by financing activities	8,739,000	73,283,000
Net increase (decrease) in cash and cash equivalents	594,000	(20,491,000)
Cash and cash equivalents
Cash and cash equivalents, at beginning of period	15,835,000	36,326,000
Cash and cash equivalents, at end of period	16,429,000	15,835,000
Supplemental disclosure of cash flow information:
Cash paid for income taxes		5,000
Cash paid for interest	14,000	126,000
Supplemental non-cash investing and financing activities:
Operating lease right-of-use asset recorded on the adoption of ASC 842	80,000
Operating lease right-of-use assets obtained in exchange for new lease liabilities	$ 201,000
Purchases of property and equipment in accounts payable and accrued and other current liabilities		$ 24,000

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Organization and Summary of significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies Description of the Business Satsuma Pharmaceuticals, Inc. (the “Company”) is a development-stage biopharmaceutical company developing a novel therapeutic for the acute treatment of migraine. The Company’s product candidate, STS101, is a drug-device combination of a proprietary dry-powder formulation of dihydroergotamine mesylate, or DHE, which can be quickly and easily self-administered by a proprietary pre-filled, single-use, nasal delivery device. The Company, headquartered in South San Francisco, was incorporated in 2016 in the state of Delaware. Private Placement In February 2021, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company agreed to sell and issue to certain purchasers an aggregate of 14,084,507 shares of its common stock at a per share purchase price of $ 5.68 , the closing price of its common stock on the Nasdaq Global Market on February 26, 2021, for gross proceeds of $ 80.0 million (“Private Placement”). The Private Placement closed in March 2021 and the Company received $ 75.2 million in net proceeds after deducting commissions and offering expenses. At-the-Market Equity Offering In October 2020, the Company entered into a sales agreement (the “SVB Sales Agreement”) with SVB Securities LLC (formerly known as SVB Leerink LLC) (“SVB”) to sell shares of its common stock, from time to time, through an at-the-market (“ATM”) equity offering program under which SVB acted as its sales agent and pursuant to which the Company could sell common stock for aggregate gross sales proceeds of up to $ 50.0 million. The issuance and sale of shares of common stock by the Company pursuant to the SVB Sales Agreement was deemed an ATM offering under the Securities Act of 1933, as amended. SVB was entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold through SVB under the SVB Sales Agreement. In September 2022, the Company issued and sold 1,538,461 shares of common stock under the SVB Sales Agreement. The shares were sold at a price of $ 6.50 per share for aggregate net proceeds of approximately $ 9.7 million, after deducting sales commission of $ 0.3 million payable by the Company. Prior to the quarter ended September 30, 2022, the Company had not issued any shares of common stock under the SVB Sales Agreement. In October 2022, the Company terminated the SVB Sales Agreement and the offer and sale of shares under the SVB Sales Agreement prospectus supplement filed in October 2020. In November 2022, the Company entered into an At-the-Market Sales Agreement (the “Virtu Sales Agreement”), with Virtu Americas LLC (“Virtu”), to sell shares of its common stock, from time to time, through an ATM equity offering program under which Virtu will act as its sales agent and pursuant to which the Company may sell common stock for aggregate gross sales proceeds of up to $ 100.0 million. The issuance and sale of shares of common stock by the Company pursuant to the Virtu Sales Agreement is deemed an ATM offering under the Securities Act of 1933, as amended. Virtu is entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold through Virtu under the Virtu Sales Agreement. As of December 31, 2022, no shares of common stock have been sold pursuant to this agreement. Liquidity The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, risks of clinical delays or failure, development by competitors of new technological innovations, protection of proprietary technology, dependence on key personnel, reliance on contract manufacturing organizations (“CMOs”) and contract research organizations (“CROs”), compliance with government regulations and the need to obtain additional financing to fund operations. STS101 is an investigational product candidate that will require completion of clinical development prior to any submission for regulatory approval and commercialization, if approved. These efforts require significant amounts of additional capital, adequate personnel, infrastructure, and extensive compliance and reporting. The Company has incurred significant losses and negative cash flows from operations in all periods since its inception and had an accumulated deficit of $ 211.8 million as of December 31, 2022. The Company has historically financed its operations primarily through its initial public offering (“IPO”), private placements of its equity securities, an ATM equity offering and borrowings under its former long-term debt facility. The Company has no products approved for sale, and the Company has not generated any revenue since its inception. The Company expects to incur significant additional operating losses over at least the next several years. There can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations or raise additional capital to support its operations would have a material adverse effect on the Company’s ability to achieve its intended business objectives. The Company has suffered recurring losses from operations that raise substantial doubt about its ability to continue as a going concern. As a result of the reported topline results from the STS101 SUMMIT Phase 3 efficacy trial, the Company does not plan to invest in commercialization of STS101. The Company will continue to look for strategic alternatives and does not plan on raising additional funds. As of December 31, 2022, the Company had cash, cash equivalents and marketable securities of $ 52.5 million . The Company’s management believes that the Company’s cash, cash equivalents and marketable securities may not be sufficient to continue as a going concern for a period of one year from the issuance date of these annual financial statements and as such, substantial doubt exists about the Company’s ability to continue as a going concern. Failure to manage discretionary spending may adversely impact the Company’s ability to achieve its intended business objectives and have an adverse effect on its results of operations and future prospects. The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The accompanying financial statements do not reflect any adjustments relating to the recoverability and reclassifications of assets and liabilities that might be necessary if the Company is unable to continue as a going concern. During the year ended December 31, 2022, the Company recorded an impairment loss of $ 11.7 million consisting of $ 6.7 million impairment loss to write down the property and equipment to its fair market value, $ 2.2 million impairment loss to write off prepaid expenses and other current assets related to purchases of property and equipment, and $ 2.8 million impairment loss to accrue non-cancelable future payments related to purchases of the property and equipment. The impairment loss was a result of the reported topline results from the STS101 SUMMIT Phase 3 efficacy trial and the plan not to invest in commercialization of STS101. Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“US GAAP”), as defined by the Financial Accounting Standards Board, or the FASB. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Such estimates include the accrual of research and development expenses, useful lives of property and equipment and the fair value of stock-based awards. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the impact of the COVID-19 pandemic and related impacts on the global economy which may delay the enrollment of subjects for our clinical trials and may disrupt our supply chain for development and manufacturing activities, and adjust those estimates and assumptions when facts and circumstances dictate. Actual results could differ materially from those estimates and assumptions. Segments The Company operates and manages its business as a single operating and reportable segment, which is the business of developing, seeking regulatory approval for and commercializing STS101 for the acute treatment of migraine. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. No product revenue has been generated since its inception. As of December 31, 2021, the Company’s long-lived assets of $ 0.1 million were located in the United States and $ 6.7 million in the United Kingdom. As of December 31, 2022, the balance of the Company's long-lived assets was nil . Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original or remaining maturity of three months or less at the date of purchase to be cash equivalents. Marketable Debt Securities The Company determines the appropriate classification of its marketable debt securities at the time of purchase and reevaluates such designation at each balance sheet date. All marketable debt securities are considered available-for-sale and carried at estimated fair values and reported in cash equivalents, short-term marketable securities or long-term marketable securities. Unrealized gains and losses on available-for-sale debt securities are excluded from net income and reported in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Interest income includes amortization of purchase premiums and discounts, realized gains and losses on sales of securities and other-than-temporary declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method. The Company regularly reviews all its investments for other-than-temporary declines in fair value . The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in fair value of an investment is below its accounting basis and the decline is other-than-temporary, the Company reduces the carrying value of the security it holds and records a loss for the amount of such decline. Concentration of Credit Risk The Company has no significant off-balance sheet concentrations of credit risk. Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and marketable securities. Substantially all the Company’s cash, cash equivalents and marketable securities are held by Silicon Valley Bank, and the Company historically has relied primarily on Silicon Valley Bank for commercial banking services. On March 10, 2023, the California Department of Financial Protection and Innovation closed Silicon Valley Bank and appointed the Federal Deposit Insurance Corporation (" FDIC") as receiver. On March 12, 2023, the U.S. Department of the Treasury, the Federal Reserve and the FDIC released a joint statement confirming that all depositors of Silicon Valley Bank would have access to all of their money after only one business day of closure, including funds held in uninsured deposit accounts. The Company received full access to the funds in its deposit and money market accounts on March 13, 2023. In light of actions by the federal government to fully protect deposit accounts, the Company has not experienced any credit losses on its deposits of cash or cash equivalents. The Company invests its cash equivalents in marketable securities and money market funds. Fair Value of Financial Instruments The carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities and market interest rates, if applicable. Refer to Note 2 for details on the fair value of marketable securities. Property and Equipment, Net Property and equipment are stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, which generally ranges from three to five years . Leasehold improvements are stated at cost and amortized over the shorter of the useful lives of the assets or the lease term. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized. Leases In February 2016, the FASB issued Accounting Standards Update No. 2016-02 (Topic 842) "Leases." Topic 842 supersedes the lease requirements in Accounting Standards Codification (“ASC”) Topic 840, " Leases ." Under Topic 842, lessees are required to recognize assets and liabilities on the balance sheet for most leases and provide enhanced disclosures. Leases will continue to be classified as either finance or operating. In July 2018, the FASB issued ASU 2018-11, “ Leases (ASC 842): Targeted Improvements ,” which provides companies an optional adoption method to ASU 2016-02 whereby a company does not have to adjust comparative period financial statements for the new standard. The Company adopted ASC 842 effective January 1, 2022 using a modified retrospective method and did not restate comparative periods. The Company recognized ROU assets of $ 0.1 million and lease liabilities of $ 0.1 million for its operating leases as of January 1, 2022 . The adoption of these ASUs did not have any impact on the statements of operations and comprehensive loss and statements of cash flows. See Note 5 for more information related to the Company’s lease obligations. The reported results for the year ended December 31, 2022 reflect the application of ASC 842, while the comparative information has not been restated and continues to be reported under the related lease accounting standards in effect for those periods. The adoption of this update represents a change in accounting principle and resulted in the recognition of right-of-use ("ROU") assets and operating lease liabilities. The Company elected the package of practical expedients, which permits the Company not to reassess prior conclusions about lease identification, lease classification and initial direct costs incurred. The Company also elected the practical expedient to combine lease and non-lease components when determining the ROU asset and lease liability, as well as the practical expedient to exclude leases with an initial term of 12 months or less. The primary effect of adopting this standard relates to the recognition of operating leases on the balance sheets and providing additional disclosures about the Company’s leasing activities. Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable or that the useful life is shorter than the Company had originally estimated. Recoverability is measured by comparison of the carrying amount of the asset or asset group to the future undiscounted cash flows which the asset or asset group is expected to generate. If the asset or asset group is considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group. If the useful life is shorter than originally estimated, the Company amortizes the remaining carrying value over the new shorter useful life. In November 2022, the Company reported topline results from the STS101 SUMMIT Phase 3 efficacy trial. Although topline data showed numerical differences in favor of STS101 5.2 mg versus placebo on the pre-specified co-primary endpoints of freedom from pain and freedom from most bothersome symptom at two hours post-administration, these differences did not achieve statistical significance. This significant change was a triggering event which resulted in an evaluation of impairment of the Company's property and equipment which were designed for future use in production of STS101 after the commercialization. The Company evaluated the recoverability of the property and equipment by comparing their carrying amount to the future undiscounted cash flows expected to be generated by the assets to determine if the carrying value was not recoverable. The recoverability test indicated that the Company's property and equipment were impaired. As a result, the Company recognized an impairment loss of $ 11.7 million for the year ended December 31, 2022. No impairment loss was recorded for the year ended December 31, 2021. Research and Development Expenses The Company’s research and development expenses consist primarily of payroll and personnel-related expenses, including salaries, employee benefit costs and stock-based compensation expenses for the Company’s research and product development employees, fees paid to third parties to conduct preclinical and clinical studies and other research and development activities on behalf of the Company, including CROs, CMOs and other service providers, costs for licenses, and allocated overhead, including rent, equipment, depreciation, information technology costs and utilities. The Company charges all research and development costs, both internal and external, to research and development expenses within the statements of operations and comprehensive loss as incurred. Payments associated with licensing agreements to acquire exclusive licenses to develop, use, manufacture and commercialize products that have not reached technological feasibility and do not have alternate commercial use are also expensed as incurred. Accrued Research and Development The Company monitors the activity under its various agreements with CROs, CMOs and other service providers to the extent possible through communication with each service provider, detailed invoice and task completion review, analysis of actual expenses against budget, pre-approval of any changes in scope, and review of contractual terms. The Company’s research and development accruals are estimated based on the level of services performed, progress of the studies, including the phase or completion of events, and contracted costs. These estimates may or may not match the actual services performed by the service providers. The estimated costs of research and development provided, but not yet invoiced, are included accrued and other current liabilities on the balance sheet. If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the accrual accordingly. Payments made to service providers under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and other current assets on the balance sheet until the services are rendered. Stock-Based Compensation The Company maintains incentive plans under which incentive stock options and nonqualified stock options may be granted to employees and non-employee service providers. The Company accounts for all shared-based awards granted to employees and non-employees based on the fair value on the date of grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. The Company accounts for forfeitures as they occur. Generally, the Company issues awards with only service-based vesting conditions. For share-based awards with service-based vesting conditions, the Company recognizes compensation expense using the straight-line method. Estimating fair value of stock-based awards using an option pricing model requires input of subjective assumptions, including fair value of the Company’s common stock, and, for stock options, expected term of options and stock price volatility. The Company uses the Black-Scholes option-pricing model to value its stock option awards. The assumptions used in calculating the fair value of stock-based awards represent management’s estimates, involve inherent uncertainties and require application of management’s judgment. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards. The Company classifies stock-based compensation expense in its statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. Comprehensive Income (Loss) Comprehensive gain or loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. In 2022 the Company recorded unrealized gain on marketable securities of less than $ 0.1 million, and in 2021 the Company recorded $ 0.1 million of unrealized loss on marketable securities in other comprehensive income (loss). Net Loss per Share Attributable to Common Stockholders Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common stock outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, outstanding stock options are considered to be potentially dilutive securities. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. Income Taxes Income taxes are recorded using an asset and liability approach. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company’s tax positions are subject to income tax audits. The Company recognizes the tax benefit of an uncertain tax position only if it is more likely than not that the position is sustainable upon examination by the taxing authority, based on the technical merits. The tax benefit recognized is measured as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its tax provision. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals that the Company believes are appropriate, as well as the related net interest and penalties. On June 29, 2020, California State Assembly Bill 85 (the “Trailer Bill”) was enacted which suspends the use of California net operating loss (“NOL”) deductions and certain tax credits, including research and development tax credits, for the 2020, 2021, and 2022 tax years. Recent Accounting Pronouncements New Accounting Pronouncements Adopted In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases . ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a ROU asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This ASU provides a lessee with an option to not account for leases with a term of 12 months or less as leases in the scope of this ASU. This ASU also requires new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. This ASU should be applied through a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements , which allows entities to elect an optional transition method where entities may continue to apply the existing lease guidance during the comparative periods and apply the new lease requirements through a cumulative effect adjustment in the period of adoption rather than in the earliest period presented. In June 2020, the FASB issued ASU 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities , which delayed the adoption dates for ASU 2016-02 for non-public entities to fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is allowed. The Company adopted Topic 842 effective January 1, 2022 using a modified retrospective method and did not restate comparative periods. The Company recognized ROU assets of $ 0.1 million and lease liabilities of $ 0.1 million for its operating leases as of January 1, 2022 . The adoption of these ASUs did no t have any impact on the statements of operations and comprehensive loss and statements of cash flows. See Note 5 for more information related to the Company’s lease obligations. New Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) , to provide financial statement users with more useful information about expected credit losses, which was subsequently updated by ASU 2019-04, Codification Improvements to Topic 326, Financial Instrument - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, and ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. Accordingly, these financial assets will be presented at the net amount expected to be collected. The amendment also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than reducing the carrying amount under the current, other-than-temporary-impairment model. In November 2019, the FASB issued ASU No. 2019-10, according to which, the new standard is effective for public business entities that meet the definition of an SEC filer, excluding entities eligible to be smaller reporting companies (“SRC”) as defined by the SEC, for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For all other entities, the new standard is effective for fiscal years beginning after December 15, 2022, and interim periods within that fiscal year. Early adoption is permitted. The Company is a SRC for fiscal years 2021 and 2022. For the Company this standard is effective for fiscal years beginning after December 15, 2022, and interim periods within that fiscal year. The adoption of this standard is not expected to have a material impact on the Company’s financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	2. Fair Value Measurements The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Unobservable inputs which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value. As of December 31, 2022, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2022 Quoted Price Significant Significant Total Assets U.S. government bonds $ 18,703 $ — $ — $ 18,703 Corporate bonds — 16,941 — 16,941 Asset backed securities — 408 — 408 Marketable securities 18,703 17,349 — 36,052 Money market funds (1) 16,384 — — 16,384 Total fair value of assets $ 35,087 $ 17,349 $ — $ 52,436 (1) Included in cash and cash equivalents on the balance sheet. Fair Value Measurements at December 31, 2022 Amortized Gross Gross Estimate Assets U.S. government bonds 18,724 2 $ ( 23 ) 18,703 Corporate bonds 16,947 1 ( 7 ) 16,941 Asset backed securities 411 — ( 3 ) 408 Marketable securities 36,082 3 ( 33 ) 36,052 Money market funds (1) 16,384 — — 16,384 Total fair value of assets $ 52,466 $ 3 $ ( 33 ) $ 52,436 (1) Included in cash and cash equivalents on the balance sheet. As of December 31, 2021, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2021 Quoted Price Significant Significant Total Assets U.S. government bonds $ 4,667 $ — $ — $ 4,667 Foreign government agency bonds (1) — 6,526 — 6,526 Corporate bonds — 49,989 — 49,989 Asset backed securities — 18,753 — 18,753 Marketable securities 4,667 75,268 — 79,935 Money market funds (2) 15,809 — — 15,809 Total fair value of assets $ 20,476 $ 75,268 $ — $ 95,744 (1) Consists of short-term agency bonds of Asian Development Bank and International Bank for Reconstruction and Development. (2) Included in cash and cash equivalents on the balance sheet. Fair Value Measurements at December 31, 2021 Amortized Gross Gross Estimate Assets U.S. government bonds $ 4,670 $ — $ ( 3 ) $ 4,667 Foreign government agency bonds (1) 6,530 — ( 4 ) 6,526 Corporate bonds 50,008 — ( 19 ) 49,989 Asset backed securities 18,769 — ( 16 ) 18,753 Marketable securities 79,977 — ( 42 ) 79,935 Money market funds (2) 15,809 — — 15,809 Total fair value of assets $ 95,786 $ — $ ( 42 ) $ 95,744 (1) Consists of short-term agency bonds of Asian Development Bank and International Bank for Reconstruction and Development. (2) Included in cash and cash equivalents on the balance sheet. There were no transfers of assets or liabilities between the fair value measurement levels during the years ended December 31, 2022 and 2021. There were no financial liabilities measured and recognized at fair value as of December 31, 2022 and December 31, 2021.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	3. Balance Sheet Components Property and Equipment, Net Property and equipment consisted of the following (in thousands, except years): December 31, Useful Life (In Years) 2022 2021 Furniture and fixtures 3 - 5 $ — $ 75 Leasehold improvements Shorter of useful life or lease term — 62 Machinery and equipment 6 — 1,084 Tooling 6 — 974 Construction in progress — — 5,219 — 7,414 Less: Accumulated depreciation — ( 622 ) $ — $ 6,792 Depreciation is computed using the straight-line method. Depreciation expense was $ 0.5 million and $ 0.4 million for the years ended December 31, 2022 and 2021, respectively. In 2022, the Company performed a recoverability test for its property and equipment when it was determined that it was more likely than not that the carrying value of the long-lived assets would not be recoverable. As a result, the Company recognized a non-cash impairment loss of $ 6.7 million for the year ended December 31, 2022, to write down the property and equipment to its fair market value, which was determined to be nil as of December 31, 2022. The Company determined that prepaid expenses and other current assets of $ 2.2 million related to purchases of property and equipment were impaired as of December 31, 2022. The Company recognized a non-cash impairment loss of $ 2.2 million for the year ended December 31, 2022, to write off prepaid expenses and other current assets related to purchases of property and equipment. Additionally, as of December 31, 2022, the Company had non-cancelable future payments of $ 2.8 million related to purchases of the property and equipment. The Company recognized a non-cash impairment loss of $ 2.8 million for the year ended December 31, 2022, and recorded a $ 2.8 million accrued impairment loss in accrued and other current liabilities on the Company's balance sheets. Accrued and Other Current Liabilities Accrued and other current liabilities consisted of the following (in thousands): December 31, 2022 2021 Accrued salaries and benefits $ 536 $ 2,117 Accrued research and development expenses 2,630 3,396 Accrued impairment loss 2,765 — Accrued professional services 66 361 Other 69 69 $ 6,066 $ 5,943

Debt

Debt	12 Months Ended
	Dec. 31, 2022
Debt Disclosure [Abstract]
Debt	4. Debt On October 26, 2018, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Silicon Valley Bank. The Loan Agreement provided for loan advances of up to $ 10.0 million. The first advance (the “Term A Loan”) of $ 5.0 million was available for draw down by the Company as of the effective date of the Loan Agreement. The remaining $ 5.0 million under the facility was never drawn down and is no longer available for draw. Interest on the loan advances were payable monthly at a floating per annum rate equal to the greater of 1.5 % above the prime rate or 6.5 %. Upon the occurrence of an event of default, interest would increase to 5.0 % above the rate that is otherwise applicable. The maturity date of the loan advances was May 1, 2022 . The effective interest rate of the Term Loan approximated its stated interest rates. The Company incurred debt issuance costs of $ 0.1 million, which was presented as reduction of the Term A Loan advance, consistent with the presentation of debt discount. Debt issuance cost and final payment of $ 0.3 million was recognized as additional interest expense using the effective interest method over the term of the loan. The Company accreted the final payment due at maturity using the effective interest rate method. The accrued liabilities related to the accretion of the final payment were $ 0.2 million as of December 31, 2021 and were included in the debt on the Company’s balance sheets. On May 3, 2022, the Company repaid its entire obligation under the Loan Agreement amounting to $ 0.4 million, including outstanding loan amount of $ 0.2 million and final payment of $ 0.2 million.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies Operating Leases On January 9, 2018, the Company entered into an office lease agreement for office space in South San Francisco, California. The lease term was through April 30, 2021 and was amended in March 2021 to extend it through October 31, 2021 . In October 20 21, the Company entered into second amendment of the office lease agreement which extended the lease term through October 31, 2022 . In October 20 22, the Company entered into third amendment of the office lease agreement which extended the lease term through April 30, 2023 . In July 2019, the Company entered into a lease agreement to lease another office space in North Carolina. The lease term for this office space was three years and was schedule to expire in July 2022 . The lease agreement was amended in February 2022 to ex tend the lease term through July 31, 2025 . The Company had the right to terminate the lease agreement effective as of July 31, 2023 by providing landlord with a written notice on or before January 31, 2023 , if the Company failed to achieve certain clinical milestones on or before January 31, 2023. For accounting purposes, the lease term is through July 31, 2023, as it is not reasonably certain that the Company will not exercise its termination option. In January 2023, the lease agreement was amended, which provided the Company the right to terminate the lease agreement effective as of October 31, 2023 by providing landlord with a written notice on or before April 30, 2023 . Rent expense was $ 0.3 million for the year ended December 31, 2021. As of December 31, 2021, less than $ 0.1 million of deferred rent representing future minimum rental payments for leases with scheduled rent escalations was included in accrued and other current liabilities on the Company’s balance sheets. Operating lease cost consists of the following (in thousands): Year Ended December 31, 2022 Operating lease cost $ 182 Short-term lease cost 139 Total lease cost $ 321 Future minimum lease payments under non-cancelable operating leases as of December 31, 2021 were as follows (in thousands): Operating 2022 $ 201 Total minimum lease payments $ 201 The maturities of operating lease liabilities as of December 31, 2022 are as follows (in thousands): December 31, 2022 2023 141 Total undiscounted lease payments 141 Less: imputed interest 3 Total operating lease liability 138 Less: current portion 138 Operating lease liability, net of current portion $ — As of December 31, 2022, the remaining term for the operating lease in North Carolina was 0.6 years, and the discount rate used to measure the lease liability for such operating lease upon recognition was 4.9 %. D uring the year ended December 31, 2022, cash paid for amounts included in operating lease liabilities of $ 0.1 million was included in cash flows from operating activities on the statements of cash flows. Contingencies From time to time, the Company may be involved in litigation related to claims that arise in the ordinary course of its business activities. The Company accrues for these matters when it is probable that future expenditures will be made, and these expenditures can be reasonably estimated. As of December 31, 2022 and 2021, the Company did not believe that any such matters, individually or in the aggregate, would have a material adverse effect on the Company’s financial position, results of operations or cash flows. Indemnification The Company enters into standard indemnification arrangements in the ordinary course of business. Pursuant to these arrangements, the Company indemnifies, holds harmless and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, in connection with any trade secret, copyright, patent or other intellectual property infringement claim by any third party with respect to its technology. The term of these indemnification agreements is generally perpetual any time after the execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these arrangements is not determinable. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the Company believes the fair value of these agreements is minimal.

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Preferred Stock	6. Preferred Stock As of December 31, 2022 and 2021, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue up to 10,000,000 shares of preferred stock at the par value of $ 0.0001 per share. As of December 31, 2022 and 2021, there were no shares of preferred stock issued and outstanding.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Common Stock	7. Common Stock The Company has authorized 300,000,000 shares of common stock, $ 0.0001 par value per share. Each holder of shares of common stock shall be entitled to one vote for each share thereof held. The Company had reserved common stock, on an as-converted basis, for future issuance as follows: December 31, 2022 2021 Exercise of outstanding options 5,292,403 3,202,588 Shares of common stock available for grant under the 2019 Plan 665,900 1,493,893 Shares of common stock available for ESPP 724,258 477,276 Total 6,682,561 5,173,757

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation 2019 Incentive Award Plan The Company’s board of directors adopted and the Company’s stockholders approved, effective on the day of effectiveness of the registration statement on Form S-1, the 2019 Incentive Award Plan (the “2019 Plan”). Awards granted under the 2019 Plan may be either incentive stock options (“ISOs”), nonqualified stock options (“NSOs”), stock appreciation rights (“SARs”), or restricted stock units (“RSUs”). ISOs may be granted only to Company employees (including officers and directors who are also employees). Following the effectiveness of the 2019 Plan, the Company will not make any further grants under the 2016 Equity Incentive Plan. However, the 2016 Plan will continue to govern the terms and conditions of the outstanding awards granted under it. Shares of common stock subject to awards granted under the 2016 Plan that are forfeited or lapse unexercised and which following the effective date of the 2019 Plan are not issued under the 2016 Plan will be available for issuance under the 2019 Plan. 2016 Incentive Award Plan In 2016, the Company established its 2016 Equity Incentive Plan (the “2016 Plan”) which provides for the granting of stock options to employees and consultants of the Company. Awards granted under the 2016 Plan may be either incentive stock options (“ISOs”), nonqualified stock options (“NSOs”), stock appreciation rights (“SARs”), or restricted stock units (“RSUs”). ISOs may be granted only to Company employees (including officers and directors who are also employees). NSOs may be granted to Company employees and consultants. The exercise price of ISOs and NSOs shall not be less than 100 % of the estimated fair value of the shares on the date of grant. The exercise price of ISOs granted to an employee who, at the time of grant, owns stock representing more than 10 % (“10% stockholder”) of the voting power of all classes of stock of the Company shall be no less than 110 % of the estimated fair value of the shares on the date of grant. The options usually have a term of 10 years (or no more than five years if granted to a 10% stockholder). Vesting conditions determined by the plan administrator may apply to stock options and may include continued service, performance and/or other conditions. Generally, options and restricted stock awards vest over a four-year period. In January 2023, the number of shares of common stock available for issuance under the 2019 Plan was increased by 1,326,099 shares as a result of the automatic increase provision in the 2019 Plan. Activity under the 2019 Plan and 2016 Plan is set forth below: Outstanding Options Shares Number of Weighted Weighted- Balance, January 1, 2021 844,475 3,162,459 $ 9.31 8.79 Additional shares authorized 697,479 Options granted ( 129,000 ) 129,000 $ 4.85 9.65 Options exercised — ( 7,932 ) $ 1.04 Options cancelled 80,939 ( 80,939 ) $ 9.77 Balance, December 31, 2021 1,493,893 3,202,588 $ 9.14 7.73 Additional shares authorized 1,261,822 Options granted ( 2,154,500 ) 2,154,500 $ 3.52 9.40 Options cancelled 64,685 ( 64,685 ) $ 10.21 Balance, December 31, 2022 665,900 5,292,403 $ 6.84 7.89 Exercisable as of December 31, 2022 2,391,071 $ 8.62 6.60 Vested and expected to vest, December 31, 2022 5,292,403 $ 6.84 7.89 The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the fair value of the Company’s common stock for stock options that were in-the-money as of December 31, 2022 and December 31, 2021. The aggregate intrinsic value of options vested and expected to vest as of December 31, 2022 and December 31, 2021 was $ 0 and $ 2.2 million, respectively. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2021 was less than $ 0.1 million. No stock options were exercised during the year ended December 31, 2022. The weighted-average grant-date fair value of options granted during the years ended December 31, 2022 and 2021 was $ 2.76 and $ 3.66 per share, respectively. The total fair value of options vested for the years ended December 31, 2022 and December 31, 2021 was $ 5.0 and $ 5.3 million, respectively. As of December 31, 2022, the total unrecognized stock-based compensation expense for stock options was $ 9.8 million, which is expected to be recognized over a weighted-average period of 2.5 years. The Company accounts for forfeitures as they occur. Stock-Based Compensation Associated with Awards to Employees and Non-employees The Company estimated the fair value of stock options using the Black Scholes option-pricing model. The fair value of stock options was valued using the following assumptions: December 31, 2022 2021 Expected term (years) 5.5 - 6.1 5.8 - 6.1 Expected volatility 95.2 %- 98.2 % 91.5 %- 98.6 % Risk-free interest rate 1.7 %- 3.4 % 0.6 %- 1.4 % Dividend yield 0 % 0 % Expected Term . The expected term is calculated using the simplified method, which is available where there is insufficient historical data about exercise patterns and post-vesting employment termination behavior. The simplified method is based on the vesting period and the contractual term for each grant, or for each vesting-tranche for awards with graded vesting. The mid-point between the vesting date and the maximum contractual expiration date is used as the expected term under this method. For awards with multiple vesting-tranches, the periods from grant until the mid-point for each of the tranches are averaged to provide an overall expected term. Expected Volatility . The Company used an average historical stock price volatility of a peer group of publicly traded companies to be representative of its expected future stock price volatility, as the Company has limited trading history for its common stock. For purposes of identifying these peer companies, the Company considered the industry, stage of development, size and financial leverage of potential comparable companies. For each grant, the Company measured historical volatility over a period equivalent to the expected term. Risk-Free Interest Rate . The risk-free interest rate is based on the implied yield currently available on U.S. Treasury zero-coupon issues with a remaining term equivalent to the expected term of a stock award. Expected Dividend Rate . The Company has not paid any dividends and does not anticipate paying any dividends in the near future. Accordingly, the Company has estimated the dividend yield to be zero . Fair Value of Common Stock The fair value of the Company’s common stock is determined based on its closing market price on the date of grant. 2019 Employee Share Purchase Plan In September 2019, the Company adopted the 2019 Employee Share Purchase Plan (“ESPP”), which became effective on the business day prior to the effectiveness of the registration statement relating to the IPO. A total of 160,000 shares of common stock were initially reserved for issuance under the ESPP. The ESPP permits eligible employees to acquire shares of the Company’s common stock through periodic payroll deductions of up to 15 % of base compensation. No employee may purchase more tha n 50,000 shares duri ng an offering period. In addition, no employee may purchase more than $ 25,000 worth of stock, determined by the fair market value of the shares at the time such option is granted, in one calendar year. At the end of each purchase period, employees are able to purchase shares at 85 % of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. The Company issued 68,473 and 16,147 shares under the ESPP for the years ended December 31, 2022 and December 31, 2021, respectively. Shares authorized for future purchase under the ESPP were 724,258 at December 31, 2022. In January 2023, the number of shares of common stock available for issuance under the ESPP was increased by 331,524 shares as a result of the automatic increase provision in the ESPP. The offering period and purchase period is determined by the board of directors. As of December 31, 2022, no new offerings had been authorized. Compensation expense is calculated using the fair value of the employees' purchase rights under the Black-Scholes option pricing model. December 31, 2022 2021 Expected term (years) 0.5 0.5 Expected volatility 60.2 %- 86.4 % 58.8 % Risk-free interest rate 0.1 %- 2.2 % 0.50 % Dividend yield 0 % 0 % Stock-Based Compensation Expense Total stock-based compensation expense recorded was as follows (in thousands): Year Ended December 31, 2022 2021 Research and development $ 2,010 $ 1,777 General and administrative 3,695 3,587 Total $ 5,705 $ 5,364 The above stock-based compensation expense related to the following equity-based awards: Year Ended December 31, 2022 2021 Stock options $ 5,662 $ 5,338 ESPP 43 26 Total $ 5,705 $ 5,364

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2022
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	9. Net Loss Per Share Attributable to Common Stockholders The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, 2022 2021 Numerator: Net loss attributable to common stockholders $ ( 70,055 ) $ ( 51,172 ) Denominator: Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 32,024,991 29,174,386 Net loss per share attributable to common stockholders, basic and diluted $ ( 2.19 ) $ ( 1.75 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive: Year Ended December 31, 2022 2021 Options to purchase common stock 5,292,403 3,202,588 Shares committed under ESPP — 33,203 Total 5,292,403 3,235,791

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes No provision for income taxes was recorded for the years ended December 31, 2022 and 2021. The Company has incurred net operating losses only in the United States since its inception. The Company has not reflected any benefit of such net operating loss carryforwards in the financial statements. The differences between the statutory tax expense (benefit) rate and the effective tax expense (benefit) rate, were as follows (in thousands): Year Ended December 31, 2022 2021 Tax at federal statutory income tax rate $ ( 14,711 ) $ ( 10,746 ) Change in valuation allowance 14,748 12,877 Permanent differences 223 141 Research and development credits ( 1,081 ) ( 2,374 ) State income taxes ( 132 ) ( 346 ) Other 953 448 Tax at effective income tax rate $ — $ — Significant components of the Company’s net deferred tax assets are summarized as follows (in thousands): December 31, 2022 2021 Deferred tax assets: Net operating loss carryforwards $ 30,706 $ 27,511 Research and development credit carryforwards 4,676 3,514 Property and equipment 1,428 — Capitalized research and experimentation expenses 8,352 — Stock-based compensation 1,210 1,189 Operating lease liability 29 — Accruals and other 688 432 Gross deferred tax assets 47,089 32,646 Less: Valuation allowance ( 47,066 ) ( 32,318 ) Deferred tax assets, net of valuation allowance 23 328 Deferred tax liabilities: Property and equipment — ( 328 ) Operating lease right-of-use asset ( 23 ) — Net deferred tax assets $ — $ — As of December 31, 2022, the Company had federal and state net operating loss carryforwards (“NOLs”) of $ 145.4 million and $ 3.3 million, respectively. The federal NOLs consist of: (1) $ 4.7 million generated before January 1, 2018, which will begin to expire in 2036 but are able to offset 100 % of taxable income; and (2) $ 140.8 million generated after December 31, 2017 that will carryforward indefinitely, but are subject to an 80 % taxable income limitation beginning in tax years after December 31, 2020 as provided by the Coronavirus Aid, Relief, and Economic Security (CARES) Act (PL 116-136). The state NOLs will begin to expire in 2036 . The Company also has California state research and development (“R&D”) credit carryforwards of $ 0.9 million, which do not expire and Federal R&D credit carryforwards of $ 5.1 million which will begin to expire in 2036 . As part of the Protecting Americans from Tax Hikes Act of 2015 (the “PATH Act”), certain eligible companies have the ability to convert a portion of their R&D tax credits to offset payroll tax liabilities. As of December 31, 2022, the Company had converted $ 1.2 million of its federal R&D credits to be utilized as an offset against future payroll taxes. The utilization of NOLs and tax credit carryforwards to offset future taxable income may be subject to an annual limitation as a result of ownership changes that have occurred previously or may occur in the future. Under Sections 382 and 383 of the Internal Revenue Code (“IRC”) a corporation that undergoes an ownership change may be subject to limitations on its ability to utilize its pre-change NOLs and other tax attributes otherwise available to offset future taxable income and/or tax liability. An ownership change is defined as a cumulative change of 50 % or more in the ownership positions of certain stockholders during a rolling three-year period. The Company has not completed a formal study to determine if any ownership changes within the meaning of IRC Section 382 and 383 have occurred. If an ownership change has occurred, the Company’s ability to use its NOLs or tax credit carryforwards may be restricted, which could require the Company to pay federal or state income taxes earlier than would be required if such limitations were not in effect. Effective for tax years beginning after December 31, 2021, taxpayers are required to capitalize any expenses incurred that are considered incidental to research and experimentation ("R&E") activities under IRC Section 174. While taxpayers historically had the option of deducting these expenses under IRC Section 174, the December 2017 Tax Cuts and Jobs Act mandates capitalization and amortization of R&E expenses for tax years beginning after December 31, 2021. Expenses incurred in connection with R&E activities in the US must be amortized over a 5-year period if incurred, and R&E expenses incurred outside the US must be amortized over a 15-year period. R&E activities are broader in scope than qualified research activities considered under IRC Section 41 (relating to the research tax credit). For the year ended December 31, 2022, the Company performed an analysis based on available guidance and determined that it will continue to be in a loss position even after the required capitalization and amortization of its R&E expenses. The Company will continue to monitor this issue for future developments, but it does not expect R&E capitalization and amortization to require it to pay cash taxes now or in the near future. Uncertain Income Tax Positions The total amount of unrecognized tax benefits as of December 31, 2022 was $ 1.2 million. If recognized, no ne of the unrecognized tax benefits would affect the Company’s effective tax rate. The following table summarizes the activity related to the Company’s unrecognized tax benefits: Balance as of January 1, 2021 $ 156 Increase related to current year tax positions 213 Increase related to prior year tax positions 38 Balance as of December 31, 2021 $ 407 Increase related to current year tax positions 958 Decrease related to prior year tax positions ( 137 ) Balance as of December 31, 2022 $ 1,228 The Company’s policy is to account for interest and penalties as income tax expense. As of December 31, 2022, the Company had no interest related to unrecognized tax benefits. No amounts of penalties related to unrecognized tax benefits were recognized in the provision for income taxes. The Company does not anticipate any significant change within twelve months following the date of the filing of this Annual Report on Form 10-K. The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. The Company is subject to U.S. federal and state income tax examination for calendar tax years beginning in 2016 due to net operating losses that are being carried forward for tax purposes.

Related Party Transaction

Related Party Transaction	12 Months Ended
	Dec. 31, 2022
Related Party Transactions [Abstract]
Related Party Transactions	11. Related Party Transactions Two existing stockholders of the Company that are affiliated with directors of the Company purchased a total of 2,464,788 shares of the Company’s common stock, with an aggregate purchase price of $ 14.0 million, in the Private Placement.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events On March 10, 2023, Silicon Valley Bank was closed by the California Department of Financial Protection and Innovation, which appointed the FDIC as receiver. At the time of the closure, the Company held assets valued at $ 0.9 million in deposit and money market accounts with Silicon Valley Bank. The Company received full access to the funds in its deposit and money market accounts on March 13, 2023. In light of actions by the federal government to fully protect deposit accounts, the Company does not expect its operations will be materially impacted by the closure of Silicon Valley Bank. On March 27, 2023, the Company's board of directors approved a plan to reduce its workforce by 9 employees, or approximately 36 % of its total headcount as of such date (the "Workforce Reduction"), in order to preserve cash and maximize the value of STS101 for a potential strategic transaction partner. In connection with the Workforce Reduction, the position of Detlef Albrecht, M.D., our Chief Medical Officer, with the Company was eliminated. The Company estimates that it will incur aggregate charges in connection with the Workforce Reduction of approximately $ 1.3 million, which relate primarily to severance payments and related continuation of benefits costs, all of which are anticipated to result in future cash expenditures, along with the payment of approximately $ 0.2 million in accrued benefits including paid-time-off. The Company expects the majority of these costs to be incurred during the quarter ending March 31, 2023.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Description of the Business	Description of the Business Satsuma Pharmaceuticals, Inc. (the “Company”) is a development-stage biopharmaceutical company developing a novel therapeutic for the acute treatment of migraine. The Company’s product candidate, STS101, is a drug-device combination of a proprietary dry-powder formulation of dihydroergotamine mesylate, or DHE, which can be quickly and easily self-administered by a proprietary pre-filled, single-use, nasal delivery device. The Company, headquartered in South San Francisco, was incorporated in 2016 in the state of Delaware.
Private Placement	Private Placement In February 2021, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company agreed to sell and issue to certain purchasers an aggregate of 14,084,507 shares of its common stock at a per share purchase price of $ 5.68 , the closing price of its common stock on the Nasdaq Global Market on February 26, 2021, for gross proceeds of $ 80.0 million (“Private Placement”). The Private Placement closed in March 2021 and the Company received $ 75.2 million in net proceeds after deducting commissions and offering expenses.
At-The-Market Equity Offering	At-the-Market Equity Offering In October 2020, the Company entered into a sales agreement (the “SVB Sales Agreement”) with SVB Securities LLC (formerly known as SVB Leerink LLC) (“SVB”) to sell shares of its common stock, from time to time, through an at-the-market (“ATM”) equity offering program under which SVB acted as its sales agent and pursuant to which the Company could sell common stock for aggregate gross sales proceeds of up to $ 50.0 million. The issuance and sale of shares of common stock by the Company pursuant to the SVB Sales Agreement was deemed an ATM offering under the Securities Act of 1933, as amended. SVB was entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold through SVB under the SVB Sales Agreement. In September 2022, the Company issued and sold 1,538,461 shares of common stock under the SVB Sales Agreement. The shares were sold at a price of $ 6.50 per share for aggregate net proceeds of approximately $ 9.7 million, after deducting sales commission of $ 0.3 million payable by the Company. Prior to the quarter ended September 30, 2022, the Company had not issued any shares of common stock under the SVB Sales Agreement. In October 2022, the Company terminated the SVB Sales Agreement and the offer and sale of shares under the SVB Sales Agreement prospectus supplement filed in October 2020. In November 2022, the Company entered into an At-the-Market Sales Agreement (the “Virtu Sales Agreement”), with Virtu Americas LLC (“Virtu”), to sell shares of its common stock, from time to time, through an ATM equity offering program under which Virtu will act as its sales agent and pursuant to which the Company may sell common stock for aggregate gross sales proceeds of up to $ 100.0 million. The issuance and sale of shares of common stock by the Company pursuant to the Virtu Sales Agreement is deemed an ATM offering under the Securities Act of 1933, as amended. Virtu is entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold through Virtu under the Virtu Sales Agreement. As of December 31, 2022, no shares of common stock have been sold pursuant to this agreement.
Liquidity	Liquidity The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, risks of clinical delays or failure, development by competitors of new technological innovations, protection of proprietary technology, dependence on key personnel, reliance on contract manufacturing organizations (“CMOs”) and contract research organizations (“CROs”), compliance with government regulations and the need to obtain additional financing to fund operations. STS101 is an investigational product candidate that will require completion of clinical development prior to any submission for regulatory approval and commercialization, if approved. These efforts require significant amounts of additional capital, adequate personnel, infrastructure, and extensive compliance and reporting. The Company has incurred significant losses and negative cash flows from operations in all periods since its inception and had an accumulated deficit of $ 211.8 million as of December 31, 2022. The Company has historically financed its operations primarily through its initial public offering (“IPO”), private placements of its equity securities, an ATM equity offering and borrowings under its former long-term debt facility. The Company has no products approved for sale, and the Company has not generated any revenue since its inception. The Company expects to incur significant additional operating losses over at least the next several years. There can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations or raise additional capital to support its operations would have a material adverse effect on the Company’s ability to achieve its intended business objectives. The Company has suffered recurring losses from operations that raise substantial doubt about its ability to continue as a going concern. As a result of the reported topline results from the STS101 SUMMIT Phase 3 efficacy trial, the Company does not plan to invest in commercialization of STS101. The Company will continue to look for strategic alternatives and does not plan on raising additional funds. As of December 31, 2022, the Company had cash, cash equivalents and marketable securities of $ 52.5 million . The Company’s management believes that the Company’s cash, cash equivalents and marketable securities may not be sufficient to continue as a going concern for a period of one year from the issuance date of these annual financial statements and as such, substantial doubt exists about the Company’s ability to continue as a going concern. Failure to manage discretionary spending may adversely impact the Company’s ability to achieve its intended business objectives and have an adverse effect on its results of operations and future prospects. The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The accompanying financial statements do not reflect any adjustments relating to the recoverability and reclassifications of assets and liabilities that might be necessary if the Company is unable to continue as a going concern. During the year ended December 31, 2022, the Company recorded an impairment loss of $ 11.7 million consisting of $ 6.7 million impairment loss to write down the property and equipment to its fair market value, $ 2.2 million impairment loss to write off prepaid expenses and other current assets related to purchases of property and equipment, and $ 2.8 million impairment loss to accrue non-cancelable future payments related to purchases of the property and equipment. The impairment loss was a result of the reported topline results from the STS101 SUMMIT Phase 3 efficacy trial and the plan not to invest in commercialization of STS101.
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“US GAAP”), as defined by the Financial Accounting Standards Board, or the FASB.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Such estimates include the accrual of research and development expenses, useful lives of property and equipment and the fair value of stock-based awards. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the impact of the COVID-19 pandemic and related impacts on the global economy which may delay the enrollment of subjects for our clinical trials and may disrupt our supply chain for development and manufacturing activities, and adjust those estimates and assumptions when facts and circumstances dictate. Actual results could differ materially from those estimates and assumptions.
Segments	Segments The Company operates and manages its business as a single operating and reportable segment, which is the business of developing, seeking regulatory approval for and commercializing STS101 for the acute treatment of migraine. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. No product revenue has been generated since its inception. As of December 31, 2021, the Company’s long-lived assets of $ 0.1 million were located in the United States and $ 6.7 million in the United Kingdom. As of December 31, 2022, the balance of the Company's long-lived assets was nil .
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original or remaining maturity of three months or less at the date of purchase to be cash equivalents.
Marketable Debt Securities	Marketable Debt Securities The Company determines the appropriate classification of its marketable debt securities at the time of purchase and reevaluates such designation at each balance sheet date. All marketable debt securities are considered available-for-sale and carried at estimated fair values and reported in cash equivalents, short-term marketable securities or long-term marketable securities. Unrealized gains and losses on available-for-sale debt securities are excluded from net income and reported in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Interest income includes amortization of purchase premiums and discounts, realized gains and losses on sales of securities and other-than-temporary declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method. The Company regularly reviews all its investments for other-than-temporary declines in fair value . The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in fair value of an investment is below its accounting basis and the decline is other-than-temporary, the Company reduces the carrying value of the security it holds and records a loss for the amount of such decline.
Concentration of Credit Risk	Concentration of Credit Risk The Company has no significant off-balance sheet concentrations of credit risk. Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and marketable securities. Substantially all the Company’s cash, cash equivalents and marketable securities are held by Silicon Valley Bank, and the Company historically has relied primarily on Silicon Valley Bank for commercial banking services. On March 10, 2023, the California Department of Financial Protection and Innovation closed Silicon Valley Bank and appointed the Federal Deposit Insurance Corporation (" FDIC") as receiver. On March 12, 2023, the U.S. Department of the Treasury, the Federal Reserve and the FDIC released a joint statement confirming that all depositors of Silicon Valley Bank would have access to all of their money after only one business day of closure, including funds held in uninsured deposit accounts. The Company received full access to the funds in its deposit and money market accounts on March 13, 2023. In light of actions by the federal government to fully protect deposit accounts, the Company has not experienced any credit losses on its deposits of cash or cash equivalents. The Company invests its cash equivalents in marketable securities and money market funds.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities and market interest rates, if applicable. Refer to Note 2 for details on the fair value of marketable securities.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, which generally ranges from three to five years . Leasehold improvements are stated at cost and amortized over the shorter of the useful lives of the assets or the lease term. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized.
Leases	Leases In February 2016, the FASB issued Accounting Standards Update No. 2016-02 (Topic 842) "Leases." Topic 842 supersedes the lease requirements in Accounting Standards Codification (“ASC”) Topic 840, " Leases ." Under Topic 842, lessees are required to recognize assets and liabilities on the balance sheet for most leases and provide enhanced disclosures. Leases will continue to be classified as either finance or operating. In July 2018, the FASB issued ASU 2018-11, “ Leases (ASC 842): Targeted Improvements ,” which provides companies an optional adoption method to ASU 2016-02 whereby a company does not have to adjust comparative period financial statements for the new standard. The Company adopted ASC 842 effective January 1, 2022 using a modified retrospective method and did not restate comparative periods. The Company recognized ROU assets of $ 0.1 million and lease liabilities of $ 0.1 million for its operating leases as of January 1, 2022 . The adoption of these ASUs did not have any impact on the statements of operations and comprehensive loss and statements of cash flows. See Note 5 for more information related to the Company’s lease obligations. The reported results for the year ended December 31, 2022 reflect the application of ASC 842, while the comparative information has not been restated and continues to be reported under the related lease accounting standards in effect for those periods. The adoption of this update represents a change in accounting principle and resulted in the recognition of right-of-use ("ROU") assets and operating lease liabilities. The Company elected the package of practical expedients, which permits the Company not to reassess prior conclusions about lease identification, lease classification and initial direct costs incurred. The Company also elected the practical expedient to combine lease and non-lease components when determining the ROU asset and lease liability, as well as the practical expedient to exclude leases with an initial term of 12 months or less. The primary effect of adopting this standard relates to the recognition of operating leases on the balance sheets and providing additional disclosures about the Company’s leasing activities.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable or that the useful life is shorter than the Company had originally estimated. Recoverability is measured by comparison of the carrying amount of the asset or asset group to the future undiscounted cash flows which the asset or asset group is expected to generate. If the asset or asset group is considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group. If the useful life is shorter than originally estimated, the Company amortizes the remaining carrying value over the new shorter useful life. In November 2022, the Company reported topline results from the STS101 SUMMIT Phase 3 efficacy trial. Although topline data showed numerical differences in favor of STS101 5.2 mg versus placebo on the pre-specified co-primary endpoints of freedom from pain and freedom from most bothersome symptom at two hours post-administration, these differences did not achieve statistical significance. This significant change was a triggering event which resulted in an evaluation of impairment of the Company's property and equipment which were designed for future use in production of STS101 after the commercialization. The Company evaluated the recoverability of the property and equipment by comparing their carrying amount to the future undiscounted cash flows expected to be generated by the assets to determine if the carrying value was not recoverable. The recoverability test indicated that the Company's property and equipment were impaired. As a result, the Company recognized an impairment loss of $ 11.7 million for the year ended December 31, 2022. No impairment loss was recorded for the year ended December 31, 2021.
Research and Development Expenses	Research and Development Expenses The Company’s research and development expenses consist primarily of payroll and personnel-related expenses, including salaries, employee benefit costs and stock-based compensation expenses for the Company’s research and product development employees, fees paid to third parties to conduct preclinical and clinical studies and other research and development activities on behalf of the Company, including CROs, CMOs and other service providers, costs for licenses, and allocated overhead, including rent, equipment, depreciation, information technology costs and utilities. The Company charges all research and development costs, both internal and external, to research and development expenses within the statements of operations and comprehensive loss as incurred. Payments associated with licensing agreements to acquire exclusive licenses to develop, use, manufacture and commercialize products that have not reached technological feasibility and do not have alternate commercial use are also expensed as incurred.
Accrued Research and Development	Accrued Research and Development The Company monitors the activity under its various agreements with CROs, CMOs and other service providers to the extent possible through communication with each service provider, detailed invoice and task completion review, analysis of actual expenses against budget, pre-approval of any changes in scope, and review of contractual terms. The Company’s research and development accruals are estimated based on the level of services performed, progress of the studies, including the phase or completion of events, and contracted costs. These estimates may or may not match the actual services performed by the service providers. The estimated costs of research and development provided, but not yet invoiced, are included accrued and other current liabilities on the balance sheet. If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the accrual accordingly. Payments made to service providers under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and other current assets on the balance sheet until the services are rendered.
Stock-Based Compensation	Stock-Based Compensation The Company maintains incentive plans under which incentive stock options and nonqualified stock options may be granted to employees and non-employee service providers. The Company accounts for all shared-based awards granted to employees and non-employees based on the fair value on the date of grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. The Company accounts for forfeitures as they occur. Generally, the Company issues awards with only service-based vesting conditions. For share-based awards with service-based vesting conditions, the Company recognizes compensation expense using the straight-line method. Estimating fair value of stock-based awards using an option pricing model requires input of subjective assumptions, including fair value of the Company’s common stock, and, for stock options, expected term of options and stock price volatility. The Company uses the Black-Scholes option-pricing model to value its stock option awards. The assumptions used in calculating the fair value of stock-based awards represent management’s estimates, involve inherent uncertainties and require application of management’s judgment. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards. The Company classifies stock-based compensation expense in its statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive gain or loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. In 2022 the Company recorded unrealized gain on marketable securities of less than $ 0.1 million, and in 2021 the Company recorded $ 0.1 million of unrealized loss on marketable securities in other comprehensive income (loss).
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common stock outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, outstanding stock options are considered to be potentially dilutive securities. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.
Income Taxes	Income Taxes Income taxes are recorded using an asset and liability approach. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company’s tax positions are subject to income tax audits. The Company recognizes the tax benefit of an uncertain tax position only if it is more likely than not that the position is sustainable upon examination by the taxing authority, based on the technical merits. The tax benefit recognized is measured as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its tax provision. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals that the Company believes are appropriate, as well as the related net interest and penalties. On June 29, 2020, California State Assembly Bill 85 (the “Trailer Bill”) was enacted which suspends the use of California net operating loss (“NOL”) deductions and certain tax credits, including research and development tax credits, for the 2020, 2021, and 2022 tax years.
Recent Accounting Pronouncements	Recent Accounting Pronouncements New Accounting Pronouncements Adopted In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases . ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a ROU asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This ASU provides a lessee with an option to not account for leases with a term of 12 months or less as leases in the scope of this ASU. This ASU also requires new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. This ASU should be applied through a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements , which allows entities to elect an optional transition method where entities may continue to apply the existing lease guidance during the comparative periods and apply the new lease requirements through a cumulative effect adjustment in the period of adoption rather than in the earliest period presented. In June 2020, the FASB issued ASU 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities , which delayed the adoption dates for ASU 2016-02 for non-public entities to fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is allowed. The Company adopted Topic 842 effective January 1, 2022 using a modified retrospective method and did not restate comparative periods. The Company recognized ROU assets of $ 0.1 million and lease liabilities of $ 0.1 million for its operating leases as of January 1, 2022 . The adoption of these ASUs did no t have any impact on the statements of operations and comprehensive loss and statements of cash flows. See Note 5 for more information related to the Company’s lease obligations. New Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) , to provide financial statement users with more useful information about expected credit losses, which was subsequently updated by ASU 2019-04, Codification Improvements to Topic 326, Financial Instrument - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, and ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. Accordingly, these financial assets will be presented at the net amount expected to be collected. The amendment also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than reducing the carrying amount under the current, other-than-temporary-impairment model. In November 2019, the FASB issued ASU No. 2019-10, according to which, the new standard is effective for public business entities that meet the definition of an SEC filer, excluding entities eligible to be smaller reporting companies (“SRC”) as defined by the SEC, for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For all other entities, the new standard is effective for fiscal years beginning after December 15, 2022, and interim periods within that fiscal year. Early adoption is permitted. The Company is a SRC for fiscal years 2021 and 2022. For the Company this standard is effective for fiscal years beginning after December 15, 2022, and interim periods within that fiscal year. The adoption of this standard is not expected to have a material impact on the Company’s financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured and Recognized at Fair Value	As of December 31, 2022, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2022 Quoted Price Significant Significant Total Assets U.S. government bonds $ 18,703 $ — $ — $ 18,703 Corporate bonds — 16,941 — 16,941 Asset backed securities — 408 — 408 Marketable securities 18,703 17,349 — 36,052 Money market funds (1) 16,384 — — 16,384 Total fair value of assets $ 35,087 $ 17,349 $ — $ 52,436 (1) Included in cash and cash equivalents on the balance sheet. Fair Value Measurements at December 31, 2022 Amortized Gross Gross Estimate Assets U.S. government bonds 18,724 2 $ ( 23 ) 18,703 Corporate bonds 16,947 1 ( 7 ) 16,941 Asset backed securities 411 — ( 3 ) 408 Marketable securities 36,082 3 ( 33 ) 36,052 Money market funds (1) 16,384 — — 16,384 Total fair value of assets $ 52,466 $ 3 $ ( 33 ) $ 52,436 (1) Included in cash and cash equivalents on the balance sheet. As of December 31, 2021, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2021 Quoted Price Significant Significant Total Assets U.S. government bonds $ 4,667 $ — $ — $ 4,667 Foreign government agency bonds (1) — 6,526 — 6,526 Corporate bonds — 49,989 — 49,989 Asset backed securities — 18,753 — 18,753 Marketable securities 4,667 75,268 — 79,935 Money market funds (2) 15,809 — — 15,809 Total fair value of assets $ 20,476 $ 75,268 $ — $ 95,744 (1) Consists of short-term agency bonds of Asian Development Bank and International Bank for Reconstruction and Development. (2) Included in cash and cash equivalents on the balance sheet. Fair Value Measurements at December 31, 2021 Amortized Gross Gross Estimate Assets U.S. government bonds $ 4,670 $ — $ ( 3 ) $ 4,667 Foreign government agency bonds (1) 6,530 — ( 4 ) 6,526 Corporate bonds 50,008 — ( 19 ) 49,989 Asset backed securities 18,769 — ( 16 ) 18,753 Marketable securities 79,977 — ( 42 ) 79,935 Money market funds (2) 15,809 — — 15,809 Total fair value of assets $ 95,786 $ — $ ( 42 ) $ 95,744 (1) Consists of short-term agency bonds of Asian Development Bank and International Bank for Reconstruction and Development. (2) Included in cash and cash equivalents on the balance sheet.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands, except years): December 31, Useful Life (In Years) 2022 2021 Furniture and fixtures 3 - 5 $ — $ 75 Leasehold improvements Shorter of useful life or lease term — 62 Machinery and equipment 6 — 1,084 Tooling 6 — 974 Construction in progress — — 5,219 — 7,414 Less: Accumulated depreciation — ( 622 ) $ — $ 6,792
Schedule of Accrued and Other Current Liabilities	Accrued and other current liabilities consisted of the following (in thousands): December 31, 2022 2021 Accrued salaries and benefits $ 536 $ 2,117 Accrued research and development expenses 2,630 3,396 Accrued impairment loss 2,765 — Accrued professional services 66 361 Other 69 69 $ 6,066 $ 5,943

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Schedule of Operating Lease Cost	Operating lease cost consists of the following (in thousands): Year Ended December 31, 2022 Operating lease cost $ 182 Short-term lease cost 139 Total lease cost $ 321
Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases	Future minimum lease payments under non-cancelable operating leases as of December 31, 2021 were as follows (in thousands): Operating 2022 $ 201 Total minimum lease payments $ 201 The maturities of operating lease liabilities as of December 31, 2022 are as follows (in thousands): December 31, 2022 2023 141 Total undiscounted lease payments 141 Less: imputed interest 3 Total operating lease liability 138 Less: current portion 138 Operating lease liability, net of current portion $ —

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Schedule of Reserved Common Stock on an as-Converted Basis for Future Issuance	The Company had reserved common stock, on an as-converted basis, for future issuance as follows: December 31, 2022 2021 Exercise of outstanding options 5,292,403 3,202,588 Shares of common stock available for grant under the 2019 Plan 665,900 1,493,893 Shares of common stock available for ESPP 724,258 477,276 Total 6,682,561 5,173,757

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of Activity Under 2019 and 2016 Plan	Activity under the 2019 Plan and 2016 Plan is set forth below: Outstanding Options Shares Number of Weighted Weighted- Balance, January 1, 2021 844,475 3,162,459 $ 9.31 8.79 Additional shares authorized 697,479 Options granted ( 129,000 ) 129,000 $ 4.85 9.65 Options exercised — ( 7,932 ) $ 1.04 Options cancelled 80,939 ( 80,939 ) $ 9.77 Balance, December 31, 2021 1,493,893 3,202,588 $ 9.14 7.73 Additional shares authorized 1,261,822 Options granted ( 2,154,500 ) 2,154,500 $ 3.52 9.40 Options cancelled 64,685 ( 64,685 ) $ 10.21 Balance, December 31, 2022 665,900 5,292,403 $ 6.84 7.89 Exercisable as of December 31, 2022 2,391,071 $ 8.62 6.60 Vested and expected to vest, December 31, 2022 5,292,403 $ 6.84 7.89
Summary of Stock Based Compensation Expense	Total stock-based compensation expense recorded was as follows (in thousands): Year Ended December 31, 2022 2021 Research and development $ 2,010 $ 1,777 General and administrative 3,695 3,587 Total $ 5,705 $ 5,364 The above stock-based compensation expense related to the following equity-based awards: Year Ended December 31, 2022 2021 Stock options $ 5,662 $ 5,338 ESPP 43 26 Total $ 5,705 $ 5,364
2016 Incentive Award Plan
Schedule of Fair Value Assumptions of Stock Options	The Company estimated the fair value of stock options using the Black Scholes option-pricing model. The fair value of stock options was valued using the following assumptions: December 31, 2022 2021 Expected term (years) 5.5 - 6.1 5.8 - 6.1 Expected volatility 95.2 %- 98.2 % 91.5 %- 98.6 % Risk-free interest rate 1.7 %- 3.4 % 0.6 %- 1.4 % Dividend yield 0 % 0 %
2019 Employee Share Purchase Plan
Schedule of Fair Value Assumptions of Stock Options	Compensation expense is calculated using the fair value of the employees' purchase rights under the Black-Scholes option pricing model. December 31, 2022 2021 Expected term (years) 0.5 0.5 Expected volatility 60.2 %- 86.4 % 58.8 % Risk-free interest rate 0.1 %- 2.2 % 0.50 % Dividend yield 0 % 0 %

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2022
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, 2022 2021 Numerator: Net loss attributable to common stockholders $ ( 70,055 ) $ ( 51,172 ) Denominator: Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 32,024,991 29,174,386 Net loss per share attributable to common stockholders, basic and diluted $ ( 2.19 ) $ ( 1.75 )
Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive: Year Ended December 31, 2022 2021 Options to purchase common stock 5,292,403 3,202,588 Shares committed under ESPP — 33,203 Total 5,292,403 3,235,791

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Schedule of Statutory Tax Expense (Benefit) Rate and Effective Tax Expense (Benefit) Rate	The differences between the statutory tax expense (benefit) rate and the effective tax expense (benefit) rate, were as follows (in thousands): Year Ended December 31, 2022 2021 Tax at federal statutory income tax rate $ ( 14,711 ) $ ( 10,746 ) Change in valuation allowance 14,748 12,877 Permanent differences 223 141 Research and development credits ( 1,081 ) ( 2,374 ) State income taxes ( 132 ) ( 346 ) Other 953 448 Tax at effective income tax rate $ — $ —
Components of Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets are summarized as follows (in thousands): December 31, 2022 2021 Deferred tax assets: Net operating loss carryforwards $ 30,706 $ 27,511 Research and development credit carryforwards 4,676 3,514 Property and equipment 1,428 — Capitalized research and experimentation expenses 8,352 — Stock-based compensation 1,210 1,189 Operating lease liability 29 — Accruals and other 688 432 Gross deferred tax assets 47,089 32,646 Less: Valuation allowance ( 47,066 ) ( 32,318 ) Deferred tax assets, net of valuation allowance 23 328 Deferred tax liabilities: Property and equipment — ( 328 ) Operating lease right-of-use asset ( 23 ) — Net deferred tax assets $ — $ —
Summary of Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s unrecognized tax benefits: Balance as of January 1, 2021 $ 156 Increase related to current year tax positions 213 Increase related to prior year tax positions 38 Balance as of December 31, 2021 $ 407 Increase related to current year tax positions 958 Decrease related to prior year tax positions ( 137 ) Balance as of December 31, 2022 $ 1,228

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies - Additional Information (Details)			1 Months Ended			12 Months Ended
	Nov. 03, 2022 USD ($)	Feb. 26, 2021 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) $ / shares shares	Mar. 31, 2021 USD ($)	Oct. 31, 2020 USD ($)	Dec. 31, 2022 USD ($) Segment shares	Dec. 31, 2021 USD ($) shares	Jan. 01, 2022 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Proceeds from private placement financing, net of issuance costs							$ 75,215,000
Accumulated deficit						$ 211,791,000	141,736,000
Cash, cash equivalents and marketable securities						$ 52,500,000
Number of operating segment | Segment						1
Number of reportable segment | Segment						1
Long-lived assets						$ 0	6,792,000
Impairments of long-lived assets						11,729,000	0
Unrealized gain (loss) on marketable securities						12,000	(71,000)
Operating lease right-of-use asset						108,000
Operating lease, liability						138,000
Property and Equipment
Organization And Summary Of Significant Accounting Policies [Line Items]
Impairments of long-lived assets						6,700,000
Prepaid Expenses and Other Current Assets
Organization And Summary Of Significant Accounting Policies [Line Items]
Impairments of long-lived assets						2,200,000
Accrued and Other Current Liabilities
Organization And Summary Of Significant Accounting Policies [Line Items]
Impairments of long-lived assets						$ 2,800,000
Securities Purchase Agreement
Organization And Summary Of Significant Accounting Policies [Line Items]
Gross proceeds from issuance of common stock		$ 80,000,000
ASU 2016-02
Organization And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, ASU, adopted [true false]						true
Change in accounting principle, ASU, adoption date								Jan. 01, 2022
Change in accounting principle, ASU, immaterial effect [true false]						true
Operating lease right-of-use asset								$ 100,000
Operating lease, liability								$ 100,000
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets						3 years
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets						5 years
Unrealized gain (loss) on marketable securities						$ 100,000
United States
Organization And Summary Of Significant Accounting Policies [Line Items]
Long-lived assets							100,000
United Kingdom
Organization And Summary Of Significant Accounting Policies [Line Items]
Long-lived assets							$ 6,700,000
Common Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued | shares						1,538,461	14,084,507
Common Stock | Securities Purchase Agreement
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued | shares		14,084,507
Shares issued, price per share | $ / shares		$ 5.68
Proceeds from private placement financing, net of issuance costs				$ 75,200,000
Common Stock | SVB Securities LLC | At-the-Market Equity Offering
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued | shares			1,538,461
Gross proceeds from issuance of common stock			$ 9,700,000
Maximum aggregate gross expected sales proceeds					$ 50,000,000
Maximum compensation for services of gross proceeds					3%
Sale of stock, price per share | $ / shares			$ 6.50
Payments of Stock Issuance Costs			$ 300,000
Common Stock | Virtu Americas LLC | At-the-Market Equity Offering
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued | shares						0
Gross proceeds from issuance of common stock	$ 100,000,000
Common Stock | Maximum | Virtu Americas LLC | At-the-Market Equity Offering
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of compensation for services of gross proceeds of common shares	3%

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Measured and Recognized at Fair Value (Details) - Recurring - USD ($) $ in Thousands		Dec. 31, 2022	Dec. 31, 2021
Assets
Marketable Securities		$ 36,052	$ 79,935
Total fair value of assets		52,436	95,744
Marketable Securities Amortized Cost		36,082	79,977
Marketable Securities Gross Unrealized Gains		3
Marketable Securities Gross Unrealized Losses		(33)	(42)
Marketable Securities Estimate Fair Value		36,052	79,935
Amortized Cost		52,466	95,786
Gross Unrealized Gains		3
Gross Unrealized Losses		(33)	(42)
Estimate Fair Value		52,436	95,744
U.S. Government Bonds
Assets
Marketable Securities		18,703	4,667
Marketable Securities Amortized Cost		18,724	4,670
Marketable Securities Gross Unrealized Gains		2
Marketable Securities Gross Unrealized Losses		(23)	(3)
Marketable Securities Estimate Fair Value		18,703	4,667
Foreign Government Agency Bonds
Assets
Marketable Securities	[1]		6,526
Marketable Securities Amortized Cost	[1]		6,530
Marketable Securities Gross Unrealized Losses	[1]		(4)
Marketable Securities Estimate Fair Value	[1]		6,526
Corporate Bonds
Assets
Marketable Securities		16,941	49,989
Marketable Securities Amortized Cost		16,947	50,008
Marketable Securities Gross Unrealized Gains		1
Marketable Securities Gross Unrealized Losses		(7)	(19)
Marketable Securities Estimate Fair Value		16,941	49,989
Asset-backed Securities
Assets
Marketable Securities		408	18,753
Marketable Securities Amortized Cost		411	18,769
Marketable Securities Gross Unrealized Losses		(3)	(16)
Marketable Securities Estimate Fair Value		408	18,753
Money Market Funds
Assets
Money market funds	[2]	16,384	15,809
Amortized Cost	[2]	16,384	15,809
Estimate Fair Value	[2]	16,384	15,809
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Marketable Securities		18,703	4,667
Total fair value of assets		35,087	20,476
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government Bonds
Assets
Marketable Securities		18,703	4,667
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
Assets
Money market funds	[2]	16,384	15,809
Quoted Prices in Active Markets for Identical Assets (Level 2)
Assets
Marketable Securities		17,349	75,268
Total fair value of assets		17,349	75,268
Quoted Prices in Active Markets for Identical Assets (Level 2) | Foreign Government Agency Bonds
Assets
Marketable Securities	[1]		6,526
Quoted Prices in Active Markets for Identical Assets (Level 2) | Corporate Bonds
Assets
Marketable Securities		16,941	49,989
Quoted Prices in Active Markets for Identical Assets (Level 2) | Asset-backed Securities
Assets
Marketable Securities		$ 408	$ 18,753
[1] Consists of short-term agency bonds of Asian Development Bank and International Bank for Reconstruction and Development. Included in cash and cash equivalents on the balance sheet.

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial liabilities measured and recognized	$ 0	$ 0

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 7,414,000
Less: Accumulated depreciation		(622,000)
Property and equipment, net	$ 0	6,792,000
Minimum
Property Plant And Equipment [Line Items]
Property and equipment useful life	3 years
Maximum
Property Plant And Equipment [Line Items]
Property and equipment useful life	5 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 75,000
Furniture and Fixtures | Minimum
Property Plant And Equipment [Line Items]
Property and equipment useful life		3 years
Furniture and Fixtures | Maximum
Property Plant And Equipment [Line Items]
Property and equipment useful life		5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment useful life		Shorter of useful life or lease term
Property and equipment, gross		$ 62,000
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment useful life		6 years
Property and equipment, gross		$ 1,084,000
Tooling
Property Plant And Equipment [Line Items]
Property and equipment useful life		6 years
Property and equipment, gross		$ 974,000
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 5,219,000

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Balance Sheet Components [Line Items]
Depreciation expense	$ 510,000	$ 393,000
Impairments of long-lived assets	11,729,000	0
Property and equipment fair market value	0
Prepaid expenses and other current assets	2,328,000	$ 6,698,000
Non-cancelable future payments	2,800,000
Accrued impairment loss	2,765,000
Property and Equipment
Balance Sheet Components [Line Items]
Impairments of long-lived assets	6,700,000
Prepaid expenses and other current assets	2,200,000
Prepaid Expenses and Other Current Assets
Balance Sheet Components [Line Items]
Impairments of long-lived assets	2,200,000
Accrued and Other Current Liabilities
Balance Sheet Components [Line Items]
Impairments of long-lived assets	$ 2,800,000

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued salaries and benefits	$ 536	$ 2,117
Accrued research and development expenses	2,630	3,396
Accrued impairment loss	2,765
Accrued professional services	66	361
Other	69	69
Total	$ 6,066	$ 5,943

Debt - Additional Information (

Debt - Additional Information (Details) - Loan Agreement - Silicon Valley Bank - USD ($)			12 Months Ended
	May 03, 2022	Oct. 26, 2018	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity		$ 10,000,000
Debt instrument, floating interest rate percentage		6.50%
Debt instrument, interest rate increase percentage		5%
Debt instrument, maturity date		May 01, 2022
Repayments of obligation	$ 400,000
Long-term debt final payment	200,000
Outstanding loan amount	$ 200,000
Debt issuance cost final payment recognized as additional interest expense			$ 300,000
Accrued liabilities related to accretion of final payment included in debt				$ 200,000
Greater above Prime Rate
Debt Instrument [Line Items]
Debt instrument, floating interest rate percentage		1.50%
Term A Loan
Debt Instrument [Line Items]
Debt instrument, current borrowing capacity		$ 5,000,000
Debt issuance costs			$ 100,000
Term Loans
Debt Instrument [Line Items]
Debt instrument, remaining borrowing capacity, no longer available for draw		$ 5,000,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions			1 Months Ended				12 Months Ended
	Jul. 31, 2019	Jan. 09, 2018	Jan. 31, 2023	Oct. 31, 2022	Feb. 28, 2022	Oct. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Lessee Lease Description [Line Items]
Operating lease, expense								$ 0.3
Operating lease remaining term							7 months 6 days
Operating lease discount rate							4.90%
Cash paid included in operating lease liabilities							$ 0.1
Accrued and Other Current Liabilities | Maximum
Lessee Lease Description [Line Items]
Operating lease deferred rent								$ 0.1
California (USA)
Lessee Lease Description [Line Items]
Operating lease expiration date		Apr. 30, 2021		Apr. 30, 2023		Oct. 31, 2022
Operating lease, option to extend		extend it through October 31, 2021		extended the lease term through April 30, 2023.		extended the lease term through October 31, 2022
Operating Lease, existence of option to extend		true		true		true
North Carolina
Lessee Lease Description [Line Items]
Operating lease expiration date	Jul. 31, 2022				Jul. 31, 2025
Operating lease, option to extend					extend the lease term through July 31, 2025
Operating Lease, existence of option to extend					true
Operating lease, term of contract	3 years
Operating lease termination date					Jul. 31, 2023
Operating lease written notice date					Jan. 31, 2023
Description of terms and conditions of option to terminate							The Company had the right to terminate the lease agreement effective as of July 31, 2023 by providing landlord with a written notice on or before January 31, 2023, if the Company failed to achieve certain clinical milestones on or before January 31, 2023. For accounting purposes, the lease term is through July 31, 2023, as it is not reasonably certain that the Company will not exercise its termination option.
North Carolina | Subsequent Event
Lessee Lease Description [Line Items]
Operating lease expiration date			Oct. 31, 2023
Operating lease written notice date			Apr. 30, 2023

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Operating Lease Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 182
Short-term lease cost	139
Total lease cost	$ 321

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Operating Lease Liabilities Payments Due [Abstract]
2022		$ 201
Total minimum lease payments	$ 141	$ 201

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
2023	$ 141
Total minimum lease payments	141	$ 201
Less: imputed interest	3
Total operating lease liability	138
Operating lease liability	$ 138

Preferred Stock - Additional In

Preferred Stock - Additional Information (Details) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Equity [Abstract]
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Equity [Abstract]
Common stock, shares authorized	300,000,000	300,000,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, voting rights	one vote for each share

Common Stock - Schedule of Rese

Common Stock - Schedule of Reserved Common Stock on an as-Converted Basis for Future Issuance (Details) - shares	Dec. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Exercise of outstanding options	5,292,403	3,202,588
Total	6,682,561	5,173,757
2019 Incentive Award Plan
Class Of Stock [Line Items]
Shares of common stock available for grant	665,900	1,493,893
ESPP
Class Of Stock [Line Items]
Shares of common stock available for grant	724,258	477,276

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate		0%	0%
Common stock, shares reserved for issuance		6,682,561	5,173,757
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate		0%
2016 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options term		10 years
Options and restricted stock awards vesting period		4 years
Aggregate intrinsic value of options vested and expected to vest		$ 0	$ 2,200,000
Stock options exercised		0
Weighted average grant-date fair value of options granted		$ 2.76	$ 3.66
Unrecognized stock-based compensation expense		$ 9,800,000
Unrecognized stock-based compensation expense, weighted-average recognition period		2 years 6 months
Fair value of options vested		$ 5,000,000	$ 5,300,000
2016 Incentive Award Plan | Incentive Stock Options | 10% Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value shares date of grant, maximum		10%
2016 Incentive Award Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price, percent of estimated fair value of shares on date of grant		100%
2016 Incentive Award Plan | Minimum | Incentive Stock Options | 10% Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price, percent of estimated fair value of shares on date of grant		110%
2016 Incentive Award Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of options exercised			$ 100,000
2016 Incentive Award Plan | Maximum | 10% Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options term		5 years
2019 Incentive Award Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of common stock shares available for Issuance	1,326,099
2019 Employee Share Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate		0%	0%
Common stock, shares reserved for issuance		724,258		160,000
Maximum percentage of base compensation permitted to acquire common stock through payroll		15%
Maximum number of shares permitted to acquire through payroll		50,000
Maximum values of shares permitted to acquire through payroll		$ 25,000
Fair market value percentage available to employees		85%
Shares issued in first offering period		68,473	16,147
2019 Employee Share Purchase Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares reserved for issuance	331,524

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Activity Under 2019 Plan and 2016 Plan (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding Options, Number of Shares, Beginning Balance	3,202,588
Outstanding Options, Number of Shares, Ending Balance	5,292,403	3,202,588
2019 and 2016 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Beginning Balance	1,493,893	844,475
Shares Available for Grant, Additional shares authorized	1,261,822	697,479
Shares Available for Grant, Options granted	(2,154,500)	(129,000)
Shares Available for Grant, Options cancelled	64,685	80,939
Shares Available for Grant, Ending Balance	665,900	1,493,893	844,475
Outstanding Options, Number of Shares, Beginning Balance	3,202,588	3,162,459
Outstanding Options, Number of Shares, Options granted	2,154,500	129,000
Outstanding Options, Number of Shares, Options exercised		(7,932)
Outstanding Options, Number of Shares, Options cancelled	(64,685)	(80,939)
Outstanding Options, Number of Shares, Ending Balance	5,292,403	3,202,588	3,162,459
Outstanding Options, Number of Shares, Exercisable as of December 31, 2022	2,391,071
Outstanding Options, Number of Shares, Vested and expected to vest, December 31, 2022	5,292,403
Outstanding Options, Weighted Average Exercise Price, Beginning Balance	$ 9.14	$ 9.31
Outstanding Options, Weighted Average Exercise Price, Options granted	3.52	4.85
Outstanding Options, Weighted Average Exercise Price, Options exercised		1.04
Outstanding Options, Weighted Average Exercise Price, Options cancelled	10.21	9.77
Outstanding Options, Weighted Average Exercise Price, Ending Balance	6.84	$ 9.14	$ 9.31
Shares Available for Grant, Exercisable as of December 31, 2022	8.62
Shares Available for Grant, Vested and expected to vest, December 31, 2022	$ 6.84
Weighted Average Remaining Contractual Term, Balance	7 years 10 months 20 days	7 years 8 months 23 days	8 years 9 months 14 days
Weighted Average Remaining Contractual Term, Options granted	9 years 4 months 24 days	9 years 7 months 24 days
Weighted Average Remaining Contractual Term, Exercisable as of December 31, 2022	6 years 7 months 6 days
Weighted Average Remaining Contractual Term, Vested and expected to vest, December 31, 2022	7 years 10 months 20 days

Stock-based Compensation - Sc_2

Stock-based Compensation - Schedule of Fair Value Assumptions of Stock Options (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	95.20%	91.50%
Expected volatility, Maximum	98.20%	98.60%
Risk-free interest rate, Minimum	1.70%	0.60%
Risk-free interest rate, Maximum	3.40%	1.40%
Dividend yield	0%	0%
2019 Employee Share Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 months	6 months
Expected volatility, Minimum	60.20%
Expected volatility, Maximum	86.40%
Expected volatility		58.80%
Risk-free interest rate		0.50%
Risk-free interest rate, Minimum	0.10%
Risk-free interest rate, Maximum	2.20%
Dividend yield	0%	0%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 6 months	5 years 9 months 18 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years 1 month 6 days	6 years 1 month 6 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,705	$ 5,364
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	2,010	1,777
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 3,695	$ 3,587

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Based Compensation Expense Related to Equity Based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,705	$ 5,364
Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	5,662	5,338
ESPP
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 43	$ 26

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss attributable to common stockholders	$ (70,055)	$ (51,172)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic	32,024,991	29,174,386
Weighted-average shares used in computing net loss per share attributable to common stockholders, diluted	32,024,991	29,174,386
Net loss per share attributable to common stockholders, basic	$ (2.19)	$ (1.75)
Net loss per share attributable to common stockholders, diluted	$ (2.19)	$ (1.75)

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	5,292,403	3,235,791
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	5,292,403	3,202,588
Shares Committed Under ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding		33,203

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2017	Dec. 31, 2018
Income Taxes [Line Items]
Provision for income taxes	$ 0	$ 0
Percentage of cumulative ownership changes	50%
Unrecognized tax benefits	$ 1,228,000	$ 407,000	$ 156,000
Unrecognized tax benefits would affect the company's effective tax rate	0
Interest related to unrecognized tax benefits	0
Penalties related to unrecognized tax benefits	0
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	145,400,000			$ 4,700,000	$ 140,800,000
Operating loss carryforwards begin to expire				2036
Operating loss carryforwards offset of taxable income percentage				100%
Operating loss carryforwards limitation rate on taxable income			80%
Tax credit carryforwards	$ 5,100,000
Tax credit carryforward, expiration year	2036
Amortization period of R&E expenses	5 years
Federal | Research and Development
Income Taxes [Line Items]
Tax credit carryforwards	$ 1,200,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 3,300,000
Operating loss carryforwards begin to expire	2036
State | California (USA) | Research and Development
Income Taxes [Line Items]
Tax credit carryforwards	$ 900,000
Outside US
Income Taxes [Line Items]
Amortization period of R&E expenses	15 years

Income Taxes - Schedule of Stat

Income Taxes - Schedule of Statutory Tax Expense (Benefit) Rate and Effective Tax Expense (Benefit) Rate (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Tax at federal statutory income tax rate	$ (14,711,000)	$ (10,746,000)
Change in valuation allowance	14,748,000	12,877,000
Permanent differences	223,000	141,000
Research and development credits	(1,081,000)	(2,374,000)
State income taxes	(132,000)	(346,000)
Other	953,000	448,000
Tax at effective income tax rate	$ 0	$ 0

Income Taxes - Components of Ne

Income Taxes - Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 30,706	$ 27,511
Research and development credit carryforwards	4,676	3,514
Property and equipment	1,428
Capitalized research and experimentation expenses	8,352
Stock-based compensation	1,210	1,189
Operating lease liability	29
Accruals and other	688	432
Gross deferred tax assets	47,089	32,646
Less: Valuation allowance	(47,066)	(32,318)
Deferred tax assets, net of valuation allowance	23	328
Deferred tax liabilities:
Property and equipment		$ (328)
Operating lease right-of-use asset	$ (23)

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Beginning balance	$ 407	$ 156
Increase related to current year tax positions	958	213
Decrease related to prior year tax positions	(137)
Increase related to prior year tax positions		38
Ending balance	$ 1,228	$ 407

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) Stockholder shares	Dec. 31, 2021 USD ($)
Related Party Transaction [Line Items]
Issuance of common stock, net of issuance costs	$ 9,700	$ 75,215
Two Existing Stockholders Affiliated with Directors
Related Party Transaction [Line Items]
Number of existing stockholders of company affiliated directors purchased common stock | Stockholder	2
Share issued | shares	2,464,788
Issuance of common stock, net of issuance costs	$ 14,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ in Thousands	Mar. 27, 2023 USD ($) Employee	Mar. 10, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Subsequent Event [Line Items]
Cash and cash equivalents			$ 16,429	$ 15,835
Subsequent Event
Subsequent Event [Line Items]
Reduction in workforce | Employee	9
Reduction in workforce, percentage	36%
Workforce reduction charges	$ 1,300
Anticipated future cash expenditures related to severance payments	$ 200
Subsequent Event | Deposit and Money Market Accounts
Subsequent Event [Line Items]
Cash and cash equivalents		$ 900