Satsuma Pharmaceuticals (STSA) 10-K25 Mar 212020 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2020	Mar. 04, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
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			$ 302
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		31,521,485
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement relating to the 2021 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, 2020.

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 36,326	$ 22,755
Short-term marketable securities	31,910	84,942
Prepaid expenses and other current assets	5,550	7,047
Total current assets	73,786	114,744
Property and equipment, net	6,473	832
Long-term marketable securities		10,203
Other non-current assets	774	497
Total assets	81,033	126,276
Liabilities
Accounts payable	3,381	4,282
Accrued and other current liabilities	2,675	1,710
Current portion of long-term debt	1,990	1,979
Total current liabilities	8,046	7,971
Long-term debt	1,042	2,951
Other noncurrent liabilities	9	19
Total liabilities	9,097	10,941
Commitments and Contingencies (Note 6)
Stockholders’ equity (deficit)
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of December 31, 2020 and December 31, 2019; no shares issued and outstanding as of December 31, 2020 and December 31, 2019
Common stock, $0.0001 par value, 300,000,000 shares authorized as of December 31, 2020 and December 31, 2019, respectively; 17,436,978 shares and 17,382,047 shares issued and outstanding as of December 31, 2020 and December 31, 2019	2	2
Additional paid-in-capital	162,469	158,317
Accumulated other comprehensive income	29	17
Accumulated deficit	(90,564)	(43,001)
Total stockholders’ equity	71,936	115,335
Total liabilities, preferred stock and stockholders' equity	$ 81,033	$ 126,276

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
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	17,436,978	17,382,047
Common stock, shares outstanding	17,436,978	17,382,047

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating expenses
Research and development	$ 36,270	$ 24,196
General and administrative	12,058	4,685
Total operating expenses	48,328	28,881
Loss from operations	(48,328)	(28,881)
Interest income	1,115	1,189
Interest expense	(350)	(482)
Other income (expense), net		(1)
Net loss	(47,563)	(28,175)
Unrealized gains on marketable securities	12	17
Comprehensive loss	$ (47,551)	$ (28,158)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.73)	$ (4.80)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	17,405,688	5,863,950

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Redeemable Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning balance at Dec. 31, 2018	$ (12,132)				$ 1	$ 2,693	$ (14,826)
Temporary equity, Beginning balance, Shares at Dec. 31, 2018		3,046,355
Temporary equity, Beginning balance at Dec. 31, 2018		$ 11,648
Beginning balance, Shares at Dec. 31, 2018					1,083,280
Conversion of redeemable convertible preferred stock into common stock	73,138				$ 1	73,137
Temporary Equity, Conversion of redeemable convertible preferred stock into common stock, Shares			(9,936,341)
Temporary Equity, Conversion of redeemable convertible preferred stock into common stock			$ (73,138)
Conversion of redeemable convertible preferred stock into common stock, Shares					9,936,341
Issuance of common stock upon initial public offering,net of issuance cost	81,435					81,435
Issuance of common stock upon initial public offering, net of issuance costs, Shares					6,052,116
Vesting of restricted stock, Shares					31,914
Issuance of Series B convertible preferred stock for cash, net of issuance costs, Shares				6,889,986
Issuance of Series B convertible preferred stock for cash, net of issuance costs				$ 61,490
Issuance of common stock upon exercise of stock options	305					305
Issuance of common stock upon exercise of stock options, Shares					273,595
Stock-based compensation	747					747
Issuance of common stock upon net exercise of common stock warrants, Shares					4,801
Other comprehensive income	17							$ 17
Net loss	(28,175)						(28,175)
Ending balance at Dec. 31, 2019	$ 115,335				$ 2	158,317	(43,001)	17
Temporary equity, Ending balance, Shares at Dec. 31, 2019	0
Ending Balance, Shares at Dec. 31, 2019					17,382,047
Issuance of common stock upon exercise of stock options	$ 82					82
Issuance of common stock upon exercise of stock options, Shares					35,265
Stock-based compensation	4,018					4,018
Issuance of common stock upon purchases under employee share purchase plan	52					52
Issuance of common stock upon purchases under employee share purchase plan, Shares					14,766
Issuance of common stock upon net exercise of common stock warrants, Shares					4,900
Other comprehensive income	12							12
Net loss	(47,563)						(47,563)
Ending balance at Dec. 31, 2020	$ 71,936				$ 2	$ 162,469	$ (90,564)	$ 29
Temporary equity, Ending balance, Shares at Dec. 31, 2020	0
Ending Balance, Shares at Dec. 31, 2020					17,436,978

Statements of Convertible Pre_2

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Series B Convertible Preferred Stock
Issuance of stock, net of issuance costs	$ 206

Statements of Cash Flows (Unaud

Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (47,563)	$ (28,175)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	239	141
Non-cash interest expense, and amortization of debt discount and issuance costs	102	132
Net amortization of premiums and accretion of discounts on marketable securities	83	(127)
Stock-based compensation	4,018	747
Loss on disposal of assets		3
Changes in assets and liabilities
Prepaid expenses and other assets	1,455	(6,489)
Accounts payable	(1,625)	3,984
Accrued and other current liabilities	974	203
Other non-current liabilities	(10)	(56)
Net cash used in operating activities	(42,327)	(29,637)
Cash flows from investing activities
Purchases of marketable securities	(34,008)	(99,855)
Proceeds from maturities of available-for-sale securities	97,172	4,530
Purchases of property and equipment	(5,165)	(551)
Net cash provided by (used in) investing activities	57,999	(95,876)
Cash flows from financing activities
Repayment of debt	(2,000)	(167)
Proceeds from issuance of convertible preferred stock, net of issuance costs		61,490
Proceeds from initial public offering		81,435
Payment of offering costs	(235)
Proceeds from issuance of common stock under employee plans	134	305
Net cash (used in) provided by financing activities	(2,101)	143,063
Net increase in cash and cash equivalents	13,571	17,550
Cash and cash equivalents
Cash and cash equivalents, at beginning of period	22,755	5,205
Cash and cash equivalents, at end of period	36,326	22,755
Supplemental disclosure of cash flow information:
Cash paid for income taxes		10
Cash paid for interest	259	347
Supplemental non-cash investing and financing activities:
Purchases of property and equipment in accounts payable and accrued and other current liabilities	$ 724	9
Conversion of redeemable convertible preferred stock into common stock		$ 73,138

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
Organization and Summary of Significant Accounting Policies	Dec. 31, 2020
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 clinical-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. Initial Public Offering On September 12, 2019, the Company’s registration statement on Form S-1 (File No. 333-233347) relating to its initial public offering (“IPO”) of common stock became effective. The IPO closed on September 17, 2019 at which time the Company issued 5,500,000 shares of its common stock at a price of $15.00 per share, which did not include the issuance of any shares in connection with the exercise by the underwriters of their option to purchase up to 825,000 additional shares. The Company received an aggregate of $82.5 million gross proceeds, before underwriting discounts, commissions and offering costs. 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”), 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 significant additional effort 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 $90.6 million as of December 31, 2020. The Company has historically financed its operations primarily through private placements of convertible preferred stock, a convertible promissory note, long-term debt and sale of common stock in the IPO. 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, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives. As of December 31, 2020, the Company had cash, cash equivalents and marketable securities of $68.2 million. The Company’s management believes that the Company’s current cash, cash equivalents and marketable securities will be sufficient to fund its planned operations for at least 12 months from the date of the issuance of these annual financial statements. 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”). Reverse Stock Split On September 11, 2019, the Company effected a 1-for-4.7 reverse stock split of the Company’s common stock and convertible preferred stock. All issued and outstanding common stock, convertible preferred stock, stock options and per share amounts contained in the accompanying financial statements and notes to the 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 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 As of December 31, 2019, As of December 31, 2020, of $1.5 million 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 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 short-term marketable securities. Substantially all the Company’s cash is held by one financial institution that management believes to be of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company invests its cash equivalents in marketable securities and money market funds. The Company has not experienced any credit losses on its deposits of cash or cash equivalents. 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. Deferred Offering Costs The Company capitalizes costs that are directly associated with in-process equity financings until such financings are consummated at which time such costs are recorded against the gross proceeds of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations and comprehensive loss. 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. 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. There have been no such impairments of long-lived assets during the years ended December 31, 2020 and December 31, Convertible Preferred Stock The Company records all shares of convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs, or residual value, if issued together with other instruments that are remeasured to fair value on a recurring basis. The convertible preferred stock is recorded outside of permanent equity because while it is not mandatorily redeemable, in certain events considered not solely within the Company’s control, such as a merger or acquisition or sale of all or substantially all of the Company’s assets (each, a “deemed liquidation event”), the convertible preferred stock will become redeemable at the option of the holders of at least a majority of the then outstanding shares of such preferred stock. All outstanding shares of convertible preferred stock converted into common stock upon effectiveness of the IPO. 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 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 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) is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. In each 2020 and 2019, the Company recorded unrealized gains on marketable securities of less than $0.1 million 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, obligation to issue additional common stock upon exercise of warrant and outstanding stock options are considered to be potentially dilutive securities. Basic and diluted net loss per share attributable to common stockholders is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The holders of convertible preferred stock do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted 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 On March 18, 2020, the Families First Coronavirus Response Act (“FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous tax-related provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. 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. The FFCR Act, CARES Act and Trailer Bill did not have a material impact on the Company’s audited financial statements as of December 31, 2020; however, the Company continues to examine the impacts the FFCR Act and CARES Act may have on its business, results of operations, financial condition and liquidity. Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) under its accounting standard codifications (“ASC”) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement New Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes. ASU 2019-12

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2020
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, 2020, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2020 Quoted Price in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets Corporate bonds $ — $ 31,910 $ — $ 31,910 Marketable securities — 31,910 — 31,910 Money market funds (1) 36,304 — — 36,304 Total fair value of assets $ 36,304 $ 31,910 $ — $ 68,214 Fair Value Measurements at December 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimate Fair Value Assets Corporate bonds $ 31,881 $ 30 $ (1 ) $ 31,910 Marketable securities 31,881 30 (1 ) 31,910 Money market funds (1) 36,304 — — 36,304 Total fair value of assets $ 68,185 $ 30 $ (1 ) $ 68,214 (1) Included in cash and cash equivalents on the balance sheet. As of December 31, 2019, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2019 Quoted Price in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets U.S. government bonds $ 10,063 $ — $ — $ 10,063 Overnight repurchase agreements (1) 14,000 — — 14,000 Corporate bonds — 64,295 — 64,295 Asset backed securities — 20,787 — 20,787 Marketable securities 24,063 85,082 — 109,145 Money market funds (1) 8,730 — — 8,730 Total fair value of assets $ 32,793 $ 85,082 $ — $ 117,875 Fair Value Measurements at December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimate Fair Value Assets U.S. government bonds $ 10,062 $ 1 $ — $ 10,063 Overnight repurchase agreements (1) 14,000 — — 14,000 Corporate bonds 64,285 17 (7 ) 64,295 Asset backed securities 20,781 7 (1 ) 20,787 Marketable securities 109,128 25 (8 ) 109,145 Money market funds (1) 8,730 — — 8,730 Total fair value of assets $ 117,858 $ 25 $ (8 ) $ 117,875 (1) Included in cash and cash equivalents on the balance sheet. 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, 2020 and 2019. As of December 31, 2020, the fair value of the Term Loan approximates the carrying amount of the loan

Balance Sheet Components

Balance Sheet Components	12 Months Ended
Balance Sheet Components	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	3. Balance Property and Equipment, Net Property and equipment consisted of the following (in thousands, except years): December 31, Useful Life (In Years) 2020 2019 Furniture and fixtures 3 $ 63 $ 58 Leasehold improvements Shorter of useful life or lease term 62 62 Machinery and equipment 3-5 933 805 Tooling 3-5 840 102 Construction in progress — 5,008 — 6,906 1,027 Less: Accumulated depreciation (433 ) (195 ) $ 6,473 $ 832 Depreciation is computed using the straight-line method. Depreciation expense was $0.2 million and $0.1 million

Accrued Liabilities and Other C

Accrued Liabilities and Other Current Liabilities	12 Months Ended
Accrued Liabilities and Other Current Liabilities	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued Liabilities and Other Current Liabilities	4. Accrued Liabilities and Other Current Liabilities Accrued liabilities consisted of the following (in thousands): December 31, 2020 2019 Accrued salaries and benefits $ 1,330 $ 1,145 Accrued research and development expenses 910 88 Accrued professional services 232 248 Accrued interest 16 27 Other 187 202 $ 2,675 $ 1,710

Long-Term Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Debt	5 . Long-Term Debt On October 26, 2018, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Silicon Valley Bank. The Loan Agreement provides 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 (the “Term B Loan” and together with the Term A Loan, the “Term Loans”) is available for draw down by the Company in $1.0 million increments. Interest on the loan advances is 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 will increase to 5.0% above the rate that is otherwise applicable. The maturity date of the loan advances is May 1, 2022. The effective interest rate of the Term Loan approximates its stated interest rates. Principal on the Term A Loan is repayable commencing on December 1, 2019 in 30 monthly payments through maturity, however if a Term B Loan advance is made, then the Term A Loan will be repayable in 24 monthly payments commencing on June 1, 2020. The Term B Loan, if drawn, will be repayable in 24 monthly payments commencing on June 1, 2020. In addition to regular monthly payments, a final payment equal to the original principal amount of the Term Loans multiplied by 5.0% is due on the earliest to occur of (a) May 1, 2020 or (b) the prepayment in full of the term loan advances. As of December 31, 2020, the Term A Loan advances, net of debt discount and debt issuance costs, were $3.0 million and are included in current portion of long-term debt and long-term debt on the Company’s balance sheet. As of December 31, 2020, the future contractual maturities of debt by fiscal year are as follows (in thousands): 2021 2,000 2022 833 Total future maturities of debt $ 2,833 In accordance with the terms of the Loan Agreement, on October 26, 2018, the Company issued warrants to purchase 10,232 shares of the Company’s common stock at an exercise price of $1.04 per share with a term of 10 years. The Company will be obligated to issue additional warrants to purchase up to a maximum aggregate amount of shares of the Company’s common stock equal to 0.15% of the Company’s fully-diluted capitalization in connection with drawdowns of the Term B Loan at an exercise price equal to the latest valuation of the Company’s common stock or if the Company’s common stock is publicly traded, the lower of the trailing 10-day average closing share price of the Company’s common stock prior to the first Term B Loan advance or the closing price per share on the day prior to the first Term B Loan advance (“Term B Warrants”). The Term B Warrants are considered issued and outstanding for accounting purposes on execution of the Loan Agreement. The warrants were accounted for and classified as equity at fair value using the following assumptions under the Option Pricing Model (“OPM”): October 26, 2018 (Issuance Date) Expected term (years) 10.0 Expected volatility 74.8 % Risk-free interest rate 3.1 % Dividend yield 0 % There were no common stock warrants outstanding as of December 31, 2020. The proceeds from the Term A Loan advance were allocated to the debt and the warrants based on their relative fair values. The resulting debt discount of less than $0.1 million is being recognized as interest expense over the term of the loan of 3.6 years using the effective interest method. The Company incurred debt issuance costs of $0.1 million, which is 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 is 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 and $0.1 million as of December 31, 2020 and December 31, 2019, respectively, included in long-term debt on the Company’s balance sheet.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6 . Commitments and 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 is through April 30, 2021. There is an option to renew for an additional three years. On December 8, 2018, the Company entered into an office lease agreement for office space in North Carolina. The lease commenced on January 2, 2019 and the lease term was through June 30, 2019. There was an option to renew for two additional periods of three months each. On March 14, 2019, the Company entered into an amendment to the lease agreement for the office space in North Carolina to lease additional workspace at the same address over the same lease term. The lease was terminated on September 30, 2019. In July 2019, the Company entered into a lease agreement to lease another office space in North Carolina. Тhe lease term for this office space is three years and the lease expires in July 2022. Rent expense was $0.3 million and $0.2 million for the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, 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 and other noncurrent liabilities on the Company’s balance sheet. Future minimum lease payments under non-cancelable operating leases as of December 31, 2020 were as follows (in thousands): Operating Leases 2021 208 2022 93 Total minimum lease payments $ 301 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, 2020 and 2019, 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

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
Convertible Preferred Stock	Dec. 31, 2020
Temporary Equity [Abstract]
Convertible Preferred Stock	7 . Convertible Preferred Stock In April 2019, the Company issued 6,889,986 shares of its Series B convertible preferred stock at $8.95444 per share to certain investors for gross proceeds of $61.7 million. Following the closing of the IPO, all outstanding shares of the redeemable convertible preferred stock converted into 9,936,341 shares of common stock and the related carrying value was reclassified to common stock and additional paid-in capital. There were no shares of redeemable convertible preferred stock outstanding as of December 31, 2020 and December 31, 2019.

Preferred Stock

Preferred Stock	12 Months Ended
Preferred Stock	Dec. 31, 2020
Equity [Abstract]
Preferred Stock	8. Preferred Stock As of December 31, 2020 and 2019, 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, 2020 and 2019, there were no shares of preferred stock issued and outstanding.

Common Stock

Common Stock	12 Months Ended
Common Stock	Dec. 31, 2020
Equity [Abstract]
Common Stock	9 . Common 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, 2020 2019 Exercise of common stock warrants — 5,116 Exercise of outstanding options 3,162,459 1,568,874 Shares of common stock available for grant under the 2019 Plan 844,475 1,778,044 Shares of common stock available for ESPP 319,054 160,000 Total 4,325,988 3,512,034

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
Stock-Based Compensation	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	1 0 . Stock-Based 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). 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 In January 2021, the number of shares of common stock available for issuance under the 2019 Plan was increased by 697,479 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 Available for Grant Number of Shares Weighted Average Exercise Price Weighted- Average Remaining Contractual Term (Years) Balance, January 1, 2019 114,905 829,775 $ 0.97 8.82 Additional shares authorized 2,675,833 Options granted (1,028,118 ) 1,028,118 $ 4.96 9.38 Options exercised — (273,595 ) $ 1.13 Options cancelled 15,424 (15,424 ) $ 1.04 Balance, December 31, 2019 1,778,044 1,568,874 $ 3.55 8.85 Additional shares authorized 695,281 Options granted (1,669,200 ) 1,669,200 $ 14.56 9.63 Options exercised — (35,265 ) $ 2.34 Options cancelled 40,350 (40,350 ) $ 8.83 Balance, December 31, 2020 844,475 3,162,459 $ 9.31 8.79 Exercisable as of December 31, 2020 862,640 $ 2.93 7.55 Vested and expected to vest, December 31, 2020 3,162,459 $ 9.31 8.79 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, 2020 and December 31, 2019. The aggregate intrinsic value of options vested and expected to vest as of December 31, 2020 and December 31, 2019 was $1.9 million and $7.8 million, respectively. The aggregate intrinsic value of stock options exercised during the years ended on December 31, 2020 and 2019 was $0.8 million and $1.0 million, respectively. The weighted-average grant-date fair value of options granted during the years ended December 31, 2020 and December 2019 was $9.62 and $3.44 per share, respectively. As of December 31, 2020, the total unrecognized stock-based compensation expense for stock options was $14.9 million, which is expected to be recognized over a weighted-average period of 2.9 years. The 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, 2020 2019 Expected term (years) 5.5 - 6.1 6.0 - 6.1 Expected volatility 71.2% - 92.5% 63.6% - 74.9% Risk-free interest rate 0.3% - 1.7% 1.4% - 2.5% 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 . 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 Prior to the IPO the fair value of the Company’s common stock underlying the stock options was determined by the Board of Directors with assistance from management and, in part, on input from an independent third-party valuation firm. The Board of Directors determined the fair value of common stock by considering a number of objective and subjective factors, including valuations of comparable companies, sales of convertible preferred stock, operating and financial performance, the lack of liquidity of the Company’s common stock and the general and industry-specific economic outlook. Subsequent to the Company’s IPO, the fair value of the Company’s common stock is determined based on its closing market price. Restricted Stock Activity with respect to restricted stock awards (“RSAs”) was as follows (in Number of Shares Underlying Outstanding RSAs Weighted Average Grant Date Fair Value Unvested, December 31, 2018 31,914 $ — Vested (31,914 ) $ — Unvested, December 31, 2019 — $ — Vested — $ — Unvested, December 31, 2020 — $ — 2019 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. In January 2020, the number of shares of common stock available for issuance under the ESPP was increased by 173,820 shares as a result of the automatic increase provision in 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 than 50,000 shares during 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 first offering period was for 6.5 months beginning from May 1, 2020 until November 15, 2020. The Company issued 14,766 shares under the ESPP for the year ended December 31, 2020. Shares authorized for future purchase under the ESPP were 319,054 at December 31, 2020. In January 2021, the number of shares of common stock available for issuance under the ESPP was increased by 174,369 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, 2020, 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. Year Ended December 31, 2020 Expected term (years) 0.5 Expected volatility 111.0% Risk-free interest rate 0.1% Dividend yield 0% As of December 31, 2020, there was no unrecognized compensation costs related to non-vested ESPP shares. Stock-Based Compensation Expense Total Year Ended December 31, 2020 2019 Research and development $ 1,290 $ 334 General and administrative 2,728 413 Total $ 4,018 $ 747 The above stock-based compensation expense related to the following equity-based awards: Year Ended December 31, 2020 2019 Stock options $ 3,989 $ 747 ESPP 29 — Total $ 4,018 $ 747

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
Net Loss Per Share Attributable to Common Stockholders	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	11. 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, 2020 2019 Numerator: Net loss attributable to common stockholders $ (47,563 ) $ (28,175 ) Denominator: Weighted-average shares outstanding 17,405,688 5,879,820 Less: weighted-average unvested restricted shares and shares subject to repurchase — (15,870 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 17,405,688 5,863,950 Net loss per share attributable to common stockholders, basic and diluted $ (2.73 ) $ (4.80 ) 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, 2020 2019 Options to purchase common stock 3,162,459 1,568,874 Warrants to purchase common stock — 5,116 Total 3,162,459 1,573,990

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	1 2 . Income Taxes No provision for income taxes was recorded for the years ended December 31, 2020 and December 31, 2019. 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, 2020 2019 Tax at federal statutory income tax rate $ (9,988 ) $ (5,917 ) Change in valuation allowance 9,950 6,708 Permanent differences (20 ) 124 Prior year true ups 341 6 Research and development credits (154 ) (873 ) State income taxes (128 ) 1 Other — (48 ) Tax at effective income tax rate $ 1 $ 1 Significant components of the Company’s net deferred tax assets are summarized as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 17,915 $ 8,250 Research and development credit carryforwards 847 1,118 Stock-based compensation 697 45 Accruals and other 286 236 Gross deferred tax assets 19,745 9,649 Less: Valuation allowance (19,441 ) (9,491 ) Deferred tax assets, net of valuation allowance 304 158 Deferred tax liabilities: Property and equipment (304 ) (158 ) Net deferred tax assets $ — $ — As of December 31, 2020, the Company had federal and state net operating loss carryforwards (“NOLs”) of $84.9 million and $1.7 million, respectively. The Company also has California state research and development (“R&D”) credit carryforwards of $0.4 million, which do not expire and Federal R&D credit carryforwards of $0.7 million which will begin to expire in 2037. The Company has not performed a formal study validating these credits claimed in the tax returns. Once a study is prepared, the amount of R&D tax credits available could vary from what was originally claimed on the tax returns. 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, 2020, the Company had converted $1.0 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. Uncertain Income Tax Positions The The following table summarizes the activity related to the Company’s unrecognized tax benefits: Balance as of January 1, 2019 $ 157 Increase related to current year tax positions 196 Decrease related to prior year tax positions (115 ) Balance as of December 31, 2019 $ 238 Increase related to current year tax positions 80 Decrease related to prior year tax positions (162 ) Balance as of December 31, 2020 $ 156 The Company’s policy is to account for interest and penalties as income tax expense. As of December 31, 2020, 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
Related Party Transaction	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	1 3 . Related Party Transactions with SNBL In April 2019, as part of the Company’s Series B Financing, SNBL purchased 307,110 shares of Series B convertible preferred stock with an aggregate purchase price of $2.7 million. In September 2019 The Company incurred expenses in connection with preclinical study services performed by SNBL of less than $0.1 million in each of the years ended December 31, 2020 and 2019, respectively, which are included in research and development expenses on the statement of operations and comprehensive loss. Amounts due to SNBL in connection with these expenses of less than $0.1 million are included in accrued and other current liabilities on the balance sheets as of December 31, 2019. As of December 31, 2020, the Company did not have any amounts due to SNBL. Transactions with Others Upon the closing of the IPO in September 2019, 3,887,668 shares of outstanding Series A and Series B convertible preferred stock owed by two shareholders of the Company, each owning more than 10% of the Company’s equity on an as-converted basis, converted into 3,887,668 shares of common stock. Upon the IPO these shareholders also purchased additional 2,633,333 shares of the Company’s common stock, with an aggregate purchase price of $39.5 million.

Quarterly Results of Operations

Quarterly Results of Operations Data (unaudited)	12 Months Ended
Quarterly Results of Operations Data (unaudited)	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations Data (unaudited)	1 4 . Quarterly Results of Operations Data (unaudited) The following table sets forth our unaudited statement of operations data for each of the eight quarters in the period ended December 31, Three months ended March 31, 2020 June 30, 2020 September 30, 2020 December 31, 2020 (In thousands, except per share amounts) Loss from operations $ (12,171 ) $ (11,500 ) $ (12,170 ) $ (12,487 ) Net loss $ (11,773 ) $ (11,269 ) $ (12,043 ) $ (12,478 ) Net loss per share attributable to common stockholders, basic and diluted $ (0.68 ) $ (0.65 ) $ (0.69 ) $ (0.72 ) Three months ended March 31, 2019 June 30, 2019 September 30, 2019 December 31, 2019 (In thousands, except per share amounts) Loss from operations $ (2,714 ) $ (6,422 ) $ (8,470 ) $ (11,275 ) Net loss $ (2,815 ) $ (6,291 ) $ (8,260 ) $ (10,809 ) Net loss per share attributable to common stockholders, basic and diluted $ (2.51 ) $ (5.48 ) $ (2.26 ) $ (0.62 )

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	1 5 . Subsequent Events In February 2021, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which it 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 aggregate gross proceeds of approximately $80.0 million.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Description of the Business	Description of the Business Satsuma Pharmaceuticals, Inc. (the “Company”) is a clinical-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.
Initial Public Offering	Initial Public Offering On September 12, 2019, the Company’s registration statement on Form S-1 (File No. 333-233347) relating to its initial public offering (“IPO”) of common stock became effective. The IPO closed on September 17, 2019 at which time the Company issued 5,500,000 shares of its common stock at a price of $15.00 per share, which did not include the issuance of any shares in connection with the exercise by the underwriters of their option to purchase up to 825,000 additional shares. The Company received an aggregate of $82.5 million gross proceeds, before underwriting discounts, commissions and offering costs.
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”), 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 significant additional effort 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 $90.6 million as of December 31, 2020. The Company has historically financed its operations primarily through private placements of convertible preferred stock, a convertible promissory note, long-term debt and sale of common stock in the IPO. 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, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives. As of December 31, 2020, the Company had cash, cash equivalents and marketable securities of $68.2 million. The Company’s management believes that the Company’s current cash, cash equivalents and marketable securities will be sufficient to fund its planned operations for at least 12 months from the date of the issuance of these annual financial statements.
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”).
Reverse Stock Split	Reverse Stock Split On September 11, 2019, the Company effected a 1-for-4.7 reverse stock split of the Company’s common stock and convertible preferred stock. All issued and outstanding common stock, convertible preferred stock, stock options and per share amounts contained in the accompanying financial statements and notes to the
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 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 As of December 31, 2019, As of December 31, 2020, of $1.5 million
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 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 short-term marketable securities. Substantially all the Company’s cash is held by one financial institution that management believes to be of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company invests its cash equivalents in marketable securities and money market funds. The Company has not experienced any credit losses on its deposits of cash or cash equivalents.
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.
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes costs that are directly associated with in-process equity financings until such financings are consummated at which time such costs are recorded against the gross proceeds of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations and comprehensive loss.
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.
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. There have been no such impairments of long-lived assets during the years ended December 31, 2020 and December 31,
Convertible Preferred Stock	Convertible Preferred Stock The Company records all shares of convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs, or residual value, if issued together with other instruments that are remeasured to fair value on a recurring basis. The convertible preferred stock is recorded outside of permanent equity because while it is not mandatorily redeemable, in certain events considered not solely within the Company’s control, such as a merger or acquisition or sale of all or substantially all of the Company’s assets (each, a “deemed liquidation event”), the convertible preferred stock will become redeemable at the option of the holders of at least a majority of the then outstanding shares of such preferred stock. All outstanding shares of convertible preferred stock converted into common stock upon effectiveness of the IPO.
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 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 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 income (loss) is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. In each 2020 and 2019, the Company recorded unrealized gains on marketable securities of less than $0.1 million 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, obligation to issue additional common stock upon exercise of warrant and outstanding stock options are considered to be potentially dilutive securities. Basic and diluted net loss per share attributable to common stockholders is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The holders of convertible preferred stock do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted
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 On March 18, 2020, the Families First Coronavirus Response Act (“FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous tax-related provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. 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. The FFCR Act, CARES Act and Trailer Bill did not have a material impact on the Company’s audited financial statements as of December 31, 2020; however, the Company continues to examine the impacts the FFCR Act and CARES Act may have on its business, results of operations, financial condition and liquidity.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) under its accounting standard codifications (“ASC”) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement New Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes. ASU 2019-12

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured and Recognized at Fair Value	As of December 31, 2020, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2020 Quoted Price in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets Corporate bonds $ — $ 31,910 $ — $ 31,910 Marketable securities — 31,910 — 31,910 Money market funds (1) 36,304 — — 36,304 Total fair value of assets $ 36,304 $ 31,910 $ — $ 68,214 Fair Value Measurements at December 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimate Fair Value Assets Corporate bonds $ 31,881 $ 30 $ (1 ) $ 31,910 Marketable securities 31,881 30 (1 ) 31,910 Money market funds (1) 36,304 — — 36,304 Total fair value of assets $ 68,185 $ 30 $ (1 ) $ 68,214 (1) Included in cash and cash equivalents on the balance sheet. As of December 31, 2019, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2019 Quoted Price in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets U.S. government bonds $ 10,063 $ — $ — $ 10,063 Overnight repurchase agreements (1) 14,000 — — 14,000 Corporate bonds — 64,295 — 64,295 Asset backed securities — 20,787 — 20,787 Marketable securities 24,063 85,082 — 109,145 Money market funds (1) 8,730 — — 8,730 Total fair value of assets $ 32,793 $ 85,082 $ — $ 117,875 Fair Value Measurements at December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimate Fair Value Assets U.S. government bonds $ 10,062 $ 1 $ — $ 10,063 Overnight repurchase agreements (1) 14,000 — — 14,000 Corporate bonds 64,285 17 (7 ) 64,295 Asset backed securities 20,781 7 (1 ) 20,787 Marketable securities 109,128 25 (8 ) 109,145 Money market funds (1) 8,730 — — 8,730 Total fair value of assets $ 117,858 $ 25 $ (8 ) $ 117,875 (1) Included in cash and cash equivalents on the balance sheet.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
Balance Sheet Components (Tables)	Dec. 31, 2020
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) 2020 2019 Furniture and fixtures 3 $ 63 $ 58 Leasehold improvements Shorter of useful life or lease term 62 62 Machinery and equipment 3-5 933 805 Tooling 3-5 840 102 Construction in progress — 5,008 — 6,906 1,027 Less: Accumulated depreciation (433 ) (195 ) $ 6,473 $ 832

Accrued Liabilities and Other_2

Accrued Liabilities and Other Current Liabilities (Tables)	12 Months Ended
Accrued Liabilities and Other Current Liabilities (Tables)	Dec. 31, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities and Other Current Liabilities	Accrued liabilities consisted of the following (in thousands): December 31, 2020 2019 Accrued salaries and benefits $ 1,330 $ 1,145 Accrued research and development expenses 910 88 Accrued professional services 232 248 Accrued interest 16 27 Other 187 202 $ 2,675 $ 1,710

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2020
Debt Disclosure [Abstract]
Summary of Future Contractual Maturities of Debt	As of December 31, 2020, the future contractual maturities of debt by fiscal year are as follows (in thousands): 2021 2,000 2022 833 Total future maturities of debt $ 2,833
Schedule of Assumptions Used for Classification of Warrants as Equity at Fair Value under Option Pricing Model	The warrants were accounted for and classified as equity at fair value using the following assumptions under the Option Pricing Model (“OPM”): October 26, 2018 (Issuance Date) Expected term (years) 10.0 Expected volatility 74.8 % Risk-free interest rate 3.1 % Dividend yield 0 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases	Future minimum lease payments under non-cancelable operating leases as of December 31, 2020 were as follows (in thousands): Operating Leases 2021 208 2022 93 Total minimum lease payments $ 301

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
Common Stock (Tables)	Dec. 31, 2020
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, 2020 2019 Exercise of common stock warrants — 5,116 Exercise of outstanding options 3,162,459 1,568,874 Shares of common stock available for grant under the 2019 Plan 844,475 1,778,044 Shares of common stock available for ESPP 319,054 160,000 Total 4,325,988 3,512,034

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Dec. 31, 2020
Schedule of Activity Under 2019 and 2016 Plan	Activity under the 2019 Plan and 2016 Plan is set forth below: Outstanding Options Shares Available for Grant Number of Shares Weighted Average Exercise Price Weighted- Average Remaining Contractual Term (Years) Balance, January 1, 2019 114,905 829,775 $ 0.97 8.82 Additional shares authorized 2,675,833 Options granted (1,028,118 ) 1,028,118 $ 4.96 9.38 Options exercised — (273,595 ) $ 1.13 Options cancelled 15,424 (15,424 ) $ 1.04 Balance, December 31, 2019 1,778,044 1,568,874 $ 3.55 8.85 Additional shares authorized 695,281 Options granted (1,669,200 ) 1,669,200 $ 14.56 9.63 Options exercised — (35,265 ) $ 2.34 Options cancelled 40,350 (40,350 ) $ 8.83 Balance, December 31, 2020 844,475 3,162,459 $ 9.31 8.79 Exercisable as of December 31, 2020 862,640 $ 2.93 7.55 Vested and expected to vest, December 31, 2020 3,162,459 $ 9.31 8.79
Schedule of Activity Under Restricted Stock Awards	Activity with respect to restricted stock awards (“RSAs”) was as follows (in Number of Shares Underlying Outstanding RSAs Weighted Average Grant Date Fair Value Unvested, December 31, 2018 31,914 $ — Vested (31,914 ) $ — Unvested, December 31, 2019 — $ — Vested — $ — Unvested, December 31, 2020 — $ —
Summary of Stock Based Compensation Expense	Total Year Ended December 31, 2020 2019 Research and development $ 1,290 $ 334 General and administrative 2,728 413 Total $ 4,018 $ 747 The above stock-based compensation expense related to the following equity-based awards: Year Ended December 31, 2020 2019 Stock options $ 3,989 $ 747 ESPP 29 — Total $ 4,018 $ 747
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, 2020 2019 Expected term (years) 5.5 - 6.1 6.0 - 6.1 Expected volatility 71.2% - 92.5% 63.6% - 74.9% Risk-free interest rate 0.3% - 1.7% 1.4% - 2.5% 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. Year Ended December 31, 2020 Expected term (years) 0.5 Expected volatility 111.0% Risk-free interest rate 0.1% Dividend yield 0%

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 Numerator: Net loss attributable to common stockholders $ (47,563 ) $ (28,175 ) Denominator: Weighted-average shares outstanding 17,405,688 5,879,820 Less: weighted-average unvested restricted shares and shares subject to repurchase — (15,870 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 17,405,688 5,863,950 Net loss per share attributable to common stockholders, basic and diluted $ (2.73 ) $ (4.80 )
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, 2020 2019 Options to purchase common stock 3,162,459 1,568,874 Warrants to purchase common stock — 5,116 Total 3,162,459 1,573,990

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2020
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, 2020 2019 Tax at federal statutory income tax rate $ (9,988 ) $ (5,917 ) Change in valuation allowance 9,950 6,708 Permanent differences (20 ) 124 Prior year true ups 341 6 Research and development credits (154 ) (873 ) State income taxes (128 ) 1 Other — (48 ) Tax at effective income tax rate $ 1 $ 1
Components of Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets are summarized as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 17,915 $ 8,250 Research and development credit carryforwards 847 1,118 Stock-based compensation 697 45 Accruals and other 286 236 Gross deferred tax assets 19,745 9,649 Less: Valuation allowance (19,441 ) (9,491 ) Deferred tax assets, net of valuation allowance 304 158 Deferred tax liabilities: Property and equipment (304 ) (158 ) 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, 2019 $ 157 Increase related to current year tax positions 196 Decrease related to prior year tax positions (115 ) Balance as of December 31, 2019 $ 238 Increase related to current year tax positions 80 Decrease related to prior year tax positions (162 ) Balance as of December 31, 2020 $ 156

Quarterly Results of Operatio_2

Quarterly Results of Operations Data (unaudited) (Tables)	12 Months Ended
Quarterly Results of Operations Data (unaudited) (Tables)	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Data	The following quarterly financial data should be read in conjunction with our audited financial statements and the related notes included elsewhere in this Annual Report on Form 10-K. Three months ended March 31, 2020 June 30, 2020 September 30, 2020 December 31, 2020 (In thousands, except per share amounts) Loss from operations $ (12,171 ) $ (11,500 ) $ (12,170 ) $ (12,487 ) Net loss $ (11,773 ) $ (11,269 ) $ (12,043 ) $ (12,478 ) Net loss per share attributable to common stockholders, basic and diluted $ (0.68 ) $ (0.65 ) $ (0.69 ) $ (0.72 ) Three months ended March 31, 2019 June 30, 2019 September 30, 2019 December 31, 2019 (In thousands, except per share amounts) Loss from operations $ (2,714 ) $ (6,422 ) $ (8,470 ) $ (11,275 ) Net loss $ (2,815 ) $ (6,291 ) $ (8,260 ) $ (10,809 ) Net loss per share attributable to common stockholders, basic and diluted $ (2.51 ) $ (5.48 ) $ (2.26 ) $ (0.62 )

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies - Additional Information (Details)	Sep. 17, 2019USD ($)$ / sharesshares	Sep. 11, 2019	Oct. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2020USD ($)segment$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Sep. 12, 2019$ / sharesshares
Organization And Summary Of Significant Accounting Policies [Line Items]
Aggregate gross proceeds from initial public offering	$ 82,500,000				$ 81,435,000
Common stock, shares authorized \| shares				300,000,000	300,000,000
Common stock, par value (in dollars per share) \| $ / shares				$ 0.0001	$ 0.0001
Preferred stock, shares authorized \| shares				10,000,000	10,000,000
Preferred stock, par value \| $ / shares				$ 0.0001	$ 0.0001
Common stock, shares issued \| shares				17,436,978	17,382,047
Accumulated deficit				$ 90,564,000	$ 43,001,000
Cash, cash equivalents and marketable securities				$ 68,200,000
Reverse stock split, conversion ratio		0.21
Number of operating segment \| segment				1
Number of reportable segment \| segment				1
Long-lived assets				$ 6,473,000	832,000
Impairments of long-lived assets				0	0
Unrealized gains on marketable securities				12,000	17,000
Other comprehensive income				$ 12,000	17,000
ASU No. 2018-13
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. 1, 2020
Change in accounting principle, ASU, immaterial effect [true false]				true
Accounting Standards Update [Extensible List]				ASU No. 2018-13
United States
Organization And Summary Of Significant Accounting Policies [Line Items]
Long-lived assets				$ 1,500,000
United Kingdom
Organization And Summary Of Significant Accounting Policies [Line Items]
Long-lived assets				$ 5,000,000
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets				5 years
Unrealized gains on marketable securities				$ 100,000	$ 100,000
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets				3 years
Common Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued \| shares					6,052,116
IPO \| Common Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued \| shares	5,500,000
Shares issued, price per share \| $ / shares	$ 15
Shares issued upon conversion \| shares	9,936,341
Common stock, shares authorized \| shares						300,000,000
Common stock, par value (in dollars per share) \| $ / shares						$ 0.0001
IPO \| Preferred Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Preferred stock, shares authorized \| shares						10,000,000
Preferred stock, par value \| $ / shares						$ 0.0001
Over-Allotment Option
Organization And Summary Of Significant Accounting Policies [Line Items]
Shares issued, price per share \| $ / shares			$ 15
Common stock, shares issued \| shares			552,116
Gross proceeds from issuance of common stock			$ 8,300,000
Over-Allotment Option \| Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Additional share issued period \| shares	825,000

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Measured and Recognized at Fair Value (Details) - Recurring - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Assets
Marketable Securities		$ 31,910	$ 109,145
Total fair value of assets		68,214	117,875
Marketable Securities Amortized Cost		31,881	109,128
Marketable Securities Gross Unrealized Gains		30	25
Marketable Securities Gross Unrealized Losses		(1)	(8)
Marketable Securities Estimate Fair Value		31,910	109,145
Amortized Cost		68,185	117,858
Gross Unrealized Gains		30	25
Gross Unrealized Losses		(1)	(8)
Estimate Fair Value		68,214	117,875
U.S. Government Bonds
Assets
Marketable Securities			10,063
Marketable Securities Amortized Cost			10,062
Marketable Securities Gross Unrealized Gains			1
Marketable Securities Estimate Fair Value			10,063
Overnight Repurchase Agreements
Assets
Marketable Securities	[1]		14,000
Marketable Securities Amortized Cost	[1]		14,000
Marketable Securities Estimate Fair Value	[1]		14,000
Corporate Bonds
Assets
Marketable Securities		31,910	64,295
Marketable Securities Amortized Cost		31,881	64,285
Marketable Securities Gross Unrealized Gains		30	17
Marketable Securities Gross Unrealized Losses		(1)	(7)
Marketable Securities Estimate Fair Value		31,910	64,295
Asset Backed Securities
Assets
Marketable Securities			20,787
Marketable Securities Amortized Cost			20,781
Marketable Securities Gross Unrealized Gains			7
Marketable Securities Gross Unrealized Losses			(1)
Marketable Securities Estimate Fair Value			20,787
Money Market Funds
Assets
Money market funds	[1]	36,304	8,730
Amortized Cost	[1]	36,304	8,730
Estimate Fair Value	[1]	36,304	8,730
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Marketable Securities			24,063
Total fair value of assets		36,304	32,793
Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. Government Bonds
Assets
Marketable Securities			10,063
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Overnight Repurchase Agreements
Assets
Marketable Securities	[1]		14,000
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money Market Funds
Assets
Money market funds	[1]	36,304	8,730
Significant Other Observable Inputs (Level 2)
Assets
Marketable Securities		31,910	85,082
Total fair value of assets		31,910	85,082
Significant Other Observable Inputs (Level 2) \| Corporate Bonds
Assets
Marketable Securities		$ 31,910	64,295
Significant Other Observable Inputs (Level 2) \| Asset Backed Securities
Assets
Marketable Securities			$ 20,787

[1]	Included in cash and cash equivalents on the balance sheet.

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - Recurring - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial liabilities measured and recognized	$ 0	$ 0
Fair value of financial assets transfers	0	0
Fair value of financial assets transfers	$ 0	$ 0

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6,906	$ 1,027
Less: Accumulated depreciation	(433)	(195)
Property and equipment, net	$ 6,473	$ 832
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 useful life	3 years	3 years
Property and equipment, gross	$ 63	$ 58
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment useful life	Shorter of useful life or lease term	Shorter of useful life or lease term
Property and equipment, gross	$ 62	$ 62
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 933	$ 805
Machinery and Equipment \| Minimum
Property Plant And Equipment [Line Items]
Property and equipment useful life	3 years	3 years
Machinery and Equipment \| Maximum
Property Plant And Equipment [Line Items]
Property and equipment useful life	5 years	5 years
Tooling
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 840	$ 102
Tooling \| Minimum
Property Plant And Equipment [Line Items]
Property and equipment useful life	3 years	3 years
Tooling \| Maximum
Property Plant And Equipment [Line Items]
Property and equipment useful life	5 years	5 years
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 5,008

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 239	$ 141

Accrued Liabilities and Other_3

Accrued Liabilities and Other Current Liabilities - Schedule of Accrued Liabilities and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued salaries and benefits	$ 1,330	$ 1,145
Accrued research and development expenses	910	88
Accrued professional services	232	248
Accrued interest	16	27
Other	187	202
Total	$ 2,675	$ 1,710

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details)	Oct. 26, 2018USD ($)$ / sharesshares	Dec. 31, 2020USD ($)Paymentshares	Dec. 31, 2019USD ($)shares
Debt Instrument [Line Items]
Long-term debt net of debt discount and issuance costs		$ 2,833,000
Number of shares to be called by warrants issued \| shares			5,116
Loan Agreement \| Silicon Valley Bank
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity	$ 10,000,000
Debt instrument, increments amount	$ 1,000,000
Debt instrument, floating interest rate percentage	6.50%
Debt instrument, interest rate increase percentage	5.00%
Debt instrument, maturity date	May 1, 2022
Debt instrument, final principal payment description		a final payment equal to the original principal amount of the Term Loans multiplied by 5.0% is due on the earliest to occur of (a) May 1, 2020 or (b) the prepayment in full of the term loan advances.
Debt instrument, final payment percentage of original principal		5.00%
Number of shares to be called by warrants issued \| shares	10,232
Warrants, exercise price \| $ / shares	$ 1.04
Warrants, term	10 years
Common stock warrants outstanding \| shares		0
Debt issuance cost final payment recognized as additional interest expense		$ 300,000
Accrued liabilities related to accretion of final payment included in long-term debt		$ 200,000	$ 100,000
Loan Agreement \| Silicon Valley Bank \| Term B Warrants
Debt Instrument [Line Items]
Maximum percentage of securities called by additional warrants	0.15%
Average closing share price, trailing period	10 days
Loan Agreement \| Silicon Valley Bank \| If Prepayment Made Prior to October 26, 2019
Debt Instrument [Line Items]
Debt instrument, percentage of prepayment premium		3.00%
Loan Agreement \| Silicon Valley Bank \| If Prepayment Made After October 26, 2019 But Before October 26, 2020
Debt Instrument [Line Items]
Debt instrument, percentage of prepayment premium		2.00%
Loan Agreement \| Silicon Valley Bank \| If Prepayment Made After October 26, 2020 But Before May 1, 2020
Debt Instrument [Line Items]
Debt instrument, percentage of prepayment premium		1.00%
Loan Agreement \| Silicon Valley Bank \| Greater above Prime Rate
Debt Instrument [Line Items]
Debt instrument, floating interest rate percentage	1.50%
Loan Agreement \| Silicon Valley Bank \| Term A Loan
Debt Instrument [Line Items]
Debt instrument, current borrowing capacity	$ 5,000,000
Debt instrument, principal repayments commencing date		Dec. 1, 2019
Debt instrument, number of monthly principal payments \| Payment		30
Long-term debt net of debt discount and issuance costs		$ 3,000,000
Debt instrument, term		3 years 7 months 6 days
Debt issuance costs		$ 100,000
Loan Agreement \| Silicon Valley Bank \| Term A Loan \| Maximum
Debt Instrument [Line Items]
Amortization of debt discount		$ 100,000
Loan Agreement \| Silicon Valley Bank \| Term A Loan \| If Term B Loan Advance Made
Debt Instrument [Line Items]
Debt instrument, principal repayments commencing date		Jun. 1, 2020
Debt instrument, number of monthly principal payments \| Payment		24
Loan Agreement \| Silicon Valley Bank \| Term Loans
Debt Instrument [Line Items]
Debt instrument, remaining borrowing capacity	$ 5,000,000
Loan Agreement \| Silicon Valley Bank \| Term B Loan
Debt Instrument [Line Items]
Debt instrument, principal repayments commencing date		Jun. 1, 2020
Debt instrument, number of monthly principal payments \| Payment		24

Long-Term Debt - Summary of Fut

Long-Term Debt - Summary of Future Contractual Maturities of Debt (Details) $ in Thousands	Dec. 31, 2020USD ($)
Debt Disclosure [Abstract]
2021	$ 2,000
2022	833
Total future maturities of debt	$ 2,833

Long-Term Debt - Schedule of As

Long-Term Debt - Schedule of Assumptions Used for Classification of Warrants as Equity at Fair Value under Option Pricing Model (Details) - Term B Warrants	Oct. 26, 2018
Expected Term (Years)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued and outstanding, expected term (years)	10 years
Expected Volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued and outstanding, measurement input	74.8
Risk-free Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued and outstanding, measurement input	3.1
Dividend Yield
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued and outstanding, measurement input	0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	Jul. 31, 2019	Dec. 08, 2018	Jan. 09, 2018	Dec. 31, 2020	Dec. 31, 2019
Lessee Lease Description [Line Items]
Operating lease, expense				$ 0.3	$ 0.2
Accrued and Other Current Liabilities \| Maximum
Lessee Lease Description [Line Items]
Operating lease deferred rent				0.1
Other Noncurrent Liabilities \| Maximum
Lessee Lease Description [Line Items]
Operating lease deferred rent				$ 0.1
California
Lessee Lease Description [Line Items]
Operating lease expiration date			Apr. 30, 2021
Operating lease, option to extend			There is an option to renew for an additional three years.
Operating Lease, existence of option to extend			true
Operating lease, renewal term			3 years
North Carolina
Lessee Lease Description [Line Items]
Operating lease expiration date	Jul. 31, 2022	Jun. 30, 2019
Operating lease, option to extend		There was an option to renew for two additional periods of three months each.
Operating Lease, existence of option to extend		true
Operating lease, renewal term		3 months
Operating lease commencement date		Jan. 2, 2019
Operating lease termination date				Sep. 30, 2019
Operating lease, term of contract	3 years

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) $ in Thousands	Dec. 31, 2020USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2021	$ 208
2022	93
Total minimum lease payments	$ 301

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 17, 2019	Apr. 30, 2019	Dec. 31, 2019	Dec. 31, 2020
Class Of Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock			$ 61,490
Redeemable convertible preferred stock outstanding, shares			0	0
Common Stock
Class Of Stock [Line Items]
Stock issued during period shares, conversion of convertible securities	9,936,341		9,936,341
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares issued		6,889,986
Shares issued price per share		$ 8.95444
Gross proceeds from issuance of convertible preferred stock		$ 61,700

Preferred Stock - Additional In

Preferred Stock - Additional Information (Details) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
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, 2020	Dec. 31, 2019
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, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Exercise of common stock warrants		5,116
Exercise of outstanding options	3,162,459	1,568,874
Total	4,325,988	3,512,034
2019 Incentive Award Plan
Class Of Stock [Line Items]
Shares of common stock available for grant	844,475	1,778,044
ESPP
Class Of Stock [Line Items]
Shares of common stock available for grant	319,054	160,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate			0.00%	0.00%
Common stock, shares reserved for issuance			4,325,988	3,512,034
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate			0.00%
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			$ 1,900,000	$ 7,800,000
Aggregate intrinsic value of options exercised			$ 800,000	$ 1,000,000
Weighted average grant-date fair value of options granted			$ 9.62	$ 3.44
Unrecognized stock-based compensation expense			$ 14,900,000
Unrecognized stock-based compensation expense, weighted-average recognition period			2 years 10 months 24 days
Fair value of options vested			$ 4,000,000	$ 700,000
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			10.00%
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			100.00%
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			110.00%
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	697,479
2019 Employee Share Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate			0.00%
Common stock, shares reserved for issuance		173,820	319,054		160,000
Maximum percentage of base compensation permitted to acquire common stock through payroll		15.00%
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		85.00%
Employee share purchase plan offering period			6 months 15 days
Shares issued in first offering period			14,766
Number of shares authorized for new offerings			0
Unrecognized compensation costs			$ 0
2019 Employee Share Purchase Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares reserved for issuance	174,369

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Activity Under 2019 Plan and 2016 Plan (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding Options, Number of Shares, Beginning Balance	1,568,874
Outstanding Options, Number of Shares, Ending Balance	3,162,459	1,568,874
2019 and 2016 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Beginning Balance	1,778,044	114,905
Shares Available for Grant, Additional shares authorized	695,281	2,675,833
Shares Available for Grant, Options granted	(1,669,200)	(1,028,118)
Shares Available for Grant, Options cancelled	40,350	15,424
Shares Available for Grant, Ending Balance	844,475	1,778,044	114,905
Outstanding Options, Number of Shares, Beginning Balance	1,568,874	829,775
Outstanding Options, Number of Shares, Options granted	1,669,200	1,028,118
Outstanding Options, Number of Shares, Options exercised	(35,265)	(273,595)
Outstanding Options, Number of Shares, Options cancelled	(40,350)	(15,424)
Outstanding Options, Number of Shares, Ending Balance	3,162,459	1,568,874	829,775
Outstanding Options, Number of Shares, Exercisable as of December 31, 2020	862,640
Outstanding Options, Number of Shares, Vested and expected to vest, December 31, 2020	3,162,459
Outstanding Options, Weighted Average Exercise Price, Beginning Balance	$ 3.55	$ 0.97
Outstanding Options, Weighted Average Exercise Price, Options granted	14.56	4.96
Outstanding Options, Weighted Average Exercise Price, Options exercised	2.34	1.13
Outstanding Options, Weighted Average Exercise Price, Options cancelled	8.83	1.04
Outstanding Options, Weighted Average Exercise Price, Ending Balance	9.31	$ 3.55	$ 0.97
Shares Available for Grant, Exercisable as of December 31, 2020	2.93
Shares Available for Grant, Vested and expected to vest, December 31, 2020	$ 9.31
Weighted Average Remaining Contractual Term, Balance	8 years 9 months 14 days	8 years 10 months 6 days	8 years 9 months 25 days
Weighted Average Remaining Contractual Term, Options granted	9 years 7 months 17 days	9 years 4 months 17 days
Weighted Average Remaining Contractual Term, Exercisable as of December 31, 2020	7 years 6 months 18 days
Weighted Average Remaining Contractual Term, Vested and expected to vest, December 31, 2020	8 years 9 months 14 days

Stock-based Compensation - Sc_2

Stock-based Compensation - Schedule of Fair Value Assumptions of Stock Options (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	71.20%	63.60%
Expected volatility, Maximum	92.50%	74.90%
Risk-free interest rate, Minimum	0.30%	1.40%
Risk-free interest rate, Maximum	1.70%	2.50%
Dividend yield	0.00%	0.00%
2019 Employee Share Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 months
Expected volatility	111.00%
Risk-free interest rate	0.10%
Dividend yield	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 6 months	6 years
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 - Sc_3

Stock-Based Compensation - Schedule of Activity Under Restricted Stock Awards (Details) - Restricted Stock Awards (“RSAs”)	12 Months Ended
	Dec. 31, 2019shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares underlying outstanding, unvested, beginning balance	31,914
Number of shares, vested in period	(31,914)

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,018	$ 747
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,290	334
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,728	$ 413

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, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,018	$ 747
Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	3,989	$ 747
ESPP
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 29

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	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss attributable to common stockholders	$ (12,478)	$ (12,043)	$ (11,269)	$ (11,773)	$ (10,809)	$ (8,260)	$ (6,291)	$ (2,815)	$ (47,563)	$ (28,175)
Denominator:
Weighted-average shares outstanding									17,405,688	5,879,820
Less: weighted-average unvested restricted shares and shares subject to repurchase										(15,870)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted									17,405,688	5,863,950
Net loss per share attributable to common stockholders, basic and diluted	$ (0.72)	$ (0.69)	$ (0.65)	$ (0.68)	$ (0.62)	$ (2.26)	$ (5.48)	$ (2.51)	$ (2.73)	$ (4.80)

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, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	3,162,459	1,573,990
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	3,162,459	1,568,874
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding		5,116

Income Taxes - Schedule of Stat

Income Taxes - Schedule of Statutory Tax Expense (Benefit) Rate and Effective Tax Expense (Benefit) Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax at federal statutory income tax rate	$ (9,988)	$ (5,917)
Change in valuation allowance	9,950	6,708
Permanent differences	(20)	124
Prior year true ups	341	6
Research and development credits	(154)	(873)
State income taxes	(128)	1
Other		(48)
Tax at effective income tax rate	$ 1	$ 1

Income Taxes - Components of Ne

Income Taxes - Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 17,915	$ 8,250
Research and development credit carryforwards	847	1,118
Stock-based compensation	697	45
Accruals and other	286	236
Gross deferred tax assets	19,745	9,649
Less: Valuation allowance	(19,441)	(9,491)
Deferred tax assets, net of valuation allowance	304	158
Deferred tax liabilities:
Property and equipment	$ (304)	$ (158)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
Income Taxes - Additional Information (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Percentage of cumulative ownership changes	50.00%
Unrecognized tax benefits	$ 156,000		$ 238,000	$ 157,000
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	$ 84,900,000	$ 4,700,000		$ 80,300,000
Operating loss carryforwards begin to expire		2036
Operating loss carryforwards offset of taxable income percentage		100.00%
Operating loss carryforwards limitation rate on taxable income	80.00%
Tax credit carryforwards	$ 700,000
Tax credit carryforward, expiration year	2037
Federal \| Research and Development
Income Taxes [Line Items]
Tax credit carryforwards	$ 1,000,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 1,700,000
Operating loss carryforwards begin to expire	2036
State \| California \| Research and Development
Income Taxes [Line Items]
Tax credit carryforwards	$ 400,000

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Beginning balance	$ 238	$ 157
Increase related to current year tax positions	80	196
Decrease related to prior year tax positions	(162)	(115)
Ending balance	$ 156	$ 238

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details)	Sep. 12, 2019USD ($)Owedshares	Sep. 30, 2019shares	Apr. 30, 2019USD ($)shares	Feb. 28, 2018shares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Related Party Transaction [Line Items]
Issuance of common stock, net of issuance costs \| $						$ 81,435,000
Series A And Series B Convertible Preferred Stock \| IPO
Related Party Transaction [Line Items]
Issuance of common stock, net of issuance costs, Shares \| shares	2,633,333
Issuance of common stock, net of issuance costs \| $	$ 39,500,000
Debt instrument converted, shares issued \| shares	3,887,668
Number of owed shareholders \| Owed	2
Percentage of minimum convertible preferred stock owning of equity on converted basis	10.00%
Shares issued upon conversion \| shares	3,887,668
SNBL
Related Party Transaction [Line Items]
Due to related party \| $					$ 0
SNBL \| IPO
Related Party Transaction [Line Items]
Issuance of common stock, net of issuance costs, Shares \| shares		233,333
SNBL \| Series B Convertible Preferred Stock
Related Party Transaction [Line Items]
Issuance of common stock, net of issuance costs, Shares \| shares			307,110
Issuance of common stock, net of issuance costs \| $			$ 2,700,000
SNBL \| Series A convertible preferred stock \| Convertible Note
Related Party Transaction [Line Items]
Debt instrument converted, shares issued \| shares				33,741
SNBL \| Maximum \| Accrued and Other Current Liabilities
Related Party Transaction [Line Items]
Due to related party \| $						100,000
SNBL \| Maximum \| Research and Development
Related Party Transaction [Line Items]
Preclinical study services expenses \| $					$ 100,000	$ 100,000

Quarterly Results of Operatio_3

Quarterly Results of Operations Data (unaudited) - Schedule of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Loss from operations	$ (12,487)	$ (12,170)	$ (11,500)	$ (12,171)	$ (11,275)	$ (8,470)	$ (6,422)	$ (2,714)	$ (48,328)	$ (28,881)
Net loss	$ (12,478)	$ (12,043)	$ (11,269)	$ (11,773)	$ (10,809)	$ (8,260)	$ (6,291)	$ (2,815)	$ (47,563)	$ (28,175)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.72)	$ (0.69)	$ (0.65)	$ (0.68)	$ (0.62)	$ (2.26)	$ (5.48)	$ (2.51)	$ (2.73)	$ (4.80)

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 26, 2021	Dec. 31, 2019
Common Stock
Subsequent Event [Line Items]
Issuance of common stock upon initial public offering, net of issuance costs, Shares		6,052,116
Subsequent Event \| Securities Purchase Agreement
Subsequent Event [Line Items]
Gross proceeds from issuance of common stock	$ 80
Subsequent Event \| Common Stock \| Securities Purchase Agreement
Subsequent Event [Line Items]
Issuance of common stock upon initial public offering, net of issuance costs, Shares	14,084,507
Shares issued, price per share	$ 5.68