Satsuma Pharmaceuticals (STSA) 10-K 10 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 29, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
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	$ 177.4
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
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		17,382,047
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement relating to the 2020 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, 2019.

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 22,755	$ 5,205
Short-term marketable securities	84,942
Prepaid expenses and other current assets	7,047	199
Total current assets	114,744	5,404
Property and equipment, net	832	445
Long-term marketable securities	10,203
Other non-current assets	497	532
Total assets	126,276	6,381
Liabilities
Accounts payable	4,282	327
Accrued and other current liabilities	1,710	1,497
Current portion of long-term debt	1,979	141
Total current liabilities	7,971	1,965
Long-term debt	2,951	4,824
Other noncurrent liabilities	19	76
Total liabilities	10,941	6,865
Commitments and Contingencies (Note 8)
Series A convertible preferred stock, $0.0001 par value, 10,000,000 shares authorized as of December 31, 2019 and 3,191,489 shares authorized as of December 31, 2018; no shares issued and outstanding as of December 31, 2019 and 3,046,355 shares issued and outstanding as of December 31, 2018; liquidation value of $0 as of December 31, 2019 and $12,134 as of December 31, 2018		11,648
Stockholders’ equity (deficit)
Common stock, $0.0001 par value, 300,000,000 shares and 5,319,148 shares authorized as of December 31, 2019 and December 31, 2018, respectively; 17,382,047 shares and 1,083,280 shares issued and outstanding as of December 31, 2019 and December 31, 2018	2	1
Additional paid-in-capital	158,317	2,693
Accumulated other comprehensive income	17
Accumulated deficit	(43,001)	(14,826)
Total stockholders’ equity (deficit)	115,335	(12,132)
Total liabilities, convertible preferred stock and stockholders equity (deficit)	$ 126,276	6,381
Series A Preferred Stock
Liabilities
Series A convertible preferred stock, $0.0001 par value, 10,000,000 shares authorized as of December 31, 2019 and 3,191,489 shares authorized as of December 31, 2018; no shares issued and outstanding as of December 31, 2019 and 3,046,355 shares issued and outstanding as of December 31, 2018; liquidation value of $0 as of December 31, 2019 and $12,134 as of December 31, 2018		$ 11,648

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized	10,000,000	3,191,489
Convertible preferred stock, issued	0	3,046,355
Convertible preferred stock, outstanding	0	3,046,355
Convertible preferred stock, liquidation value	$ 0	$ 12,134
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	5,319,148
Common stock, shares issued	17,382,047	1,083,280
Common stock, shares outstanding	17,382,047	1,083,280

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses
Research and development	$ 24,196	$ 6,433	$ 4,193
General and administrative	4,685	1,082	754
Total operating expenses	28,881	7,515	4,947
Loss from operations	(28,881)	(7,515)	(4,947)
Interest income	1,189	72	30
Interest expense	(482)	(90)	(15)
Other income (expense), net	(1)	187	(240)
Net loss	(28,175)	(7,346)	(5,172)
Unrealized gains on marketable securities	17
Comprehensive loss	$ (28,158)	$ (7,346)	$ (5,172)
Net loss per share attributable to common stockholders, basic and diluted	$ (4.80)	$ (7.15)	$ (9.26)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	5,863,950	1,026,905	558,597

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)	Total	Convertible Preferred Stock	Redeemable Convertible Preferred Stock	Series A 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, 2016	$ (326,000)						$ 1,982,000	$ (2,308,000)
Temporary equity, Beginning balance, Shares at Dec. 31, 2016		1,506,307
Temporary equity, Beginning balance at Dec. 31, 2016		$ 5,528,000
Beginning balance, Shares at Dec. 31, 2016						542,553
Vesting of restricted stock, Shares						31,915
Stock-based compensation	66,000						66,000
Net loss	(5,172,000)							(5,172,000)
Other comprehensive income	0
Ending balance at Dec. 31, 2017	(5,432,000)						2,048,000	(7,480,000)
Temporary equity, Ending balance, Shares at Dec. 31, 2017		1,506,307
Temporary equity, Ending balance at Dec. 31, 2017		$ 5,528,000
Ending Balance, Shares at Dec. 31, 2017						574,468
Vesting of restricted stock, Shares						31,915
Issuance of common stock on settlement of obligation to issue additional common stock	472,000					$ 1,000	471,000
Issuance of common stock on settlement of obligation to issue additional common stock, Shares						476,897
Common stock warrants issued in connection with long-term debt	4,000						4,000
Issuance of convertible preferred stock for cash, net of issuance costs, Shares				1,506,307
Issuance of convertible preferred stock for cash, net of issuance costs				$ 5,986,000
Conversion of convertible note into Series A convertible preferred stock, Shares		33,741
Conversion of convertible note into Series A convertible preferred stock, including interest of $8 adjusted for derivative liability of $27		$ 134,000
Stock-based compensation	170,000						170,000
Net loss	(7,346,000)							(7,346,000)
Other comprehensive income	0
Ending balance at Dec. 31, 2018	$ (12,132,000)					$ 1,000	2,693,000	(14,826,000)
Temporary equity, Ending balance, Shares at Dec. 31, 2018	3,046,355	3,046,355		3,046,355
Temporary equity, Ending balance at Dec. 31, 2018	$ 11,648,000	$ 11,648,000		$ 11,648,000
Ending Balance, Shares at Dec. 31, 2018						1,083,280
Conversion of redeemable convertible preferred stock into common stock	73,138,000					$ 1,000	73,137,000
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			$ (73,138,000)
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	81,435,000						81,435,000
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 convertible preferred stock for cash, net of issuance costs, Shares					6,889,986
Issuance of convertible preferred stock for cash, net of issuance costs					$ 61,490,000
Stock-based compensation	747,000						747,000
Net loss	(28,175,000)							(28,175,000)
Issuance of common stock upon exercise of stock options	305,000						305,000
Issuance of common stock upon exercise of stock options, Shares						273,595
Other comprehensive income	17,000								$ 17,000
Issuance of common stock upon net exercise of common stock warrants, Shares						4,801
Ending balance at Dec. 31, 2019	$ 115,335,000					$ 2,000	$ 158,317,000	$ (43,001,000)	$ 17,000
Temporary equity, Ending balance, Shares at Dec. 31, 2019	0
Ending Balance, Shares at Dec. 31, 2019						17,382,047

Statements of Convertible Pre_2

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Series A Convertible Preferred Stock
Issuance of stock, net of issuance costs		$ 14
Conversion of convertible note interest		8
Conversion of convertible note derivative liability		$ 27
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, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (28,175)	$ (7,346)	$ (5,172)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	141	57	10
Non-cash interest expense, and amortization of debt discount and issuance costs	132	28	15
Net amortization of premiums and accretion of discounts on marketable securities	(127)
Stock-based compensation	747	170	66
Loss on disposal of assets	3
Change in fair value of derivative liability		1	7
Change in fair value of obligation to issue additional common stock		101	232
Change in fair value of convertible preferred stock tranche liability		(291)
Loss on extinguishment of convertible note		4
Changes in assets and liabilities
Prepaid expenses and other assets	(6,489)	(475)	(254)
Accounts payable	3,984	(177)	363
Accrued and other current liabilities	203	924	412
Other non-current liabilities	(56)	23
Net cash used in operating activities	(29,637)	(6,981)	(4,321)
Cash flows from investing activities
Purchases of marketable securities	(99,855)
Proceeds from maturities of available-for-sale securities	4,530
Purchases of property and equipment	(551)	(402)	(58)
Net cash used in investing activities	(95,876)	(402)	(58)
Cash flows from financing activities
Borrowings, net of issuance costs		4,944
Repayment of debt	(167)
Proceeds from issuance of convertible preferred stock, net of issuance costs	61,490	5,986
Proceeds from initial public offering	81,435
Proceeds from exercise of common stock options	305
Net cash provided by financing activities	143,063	10,930
Net increase (decrease) in cash and cash equivalents	17,550	3,547	(4,379)
Cash and cash equivalents
Cash and cash equivalents, at beginning of period	5,205	1,658	6,037
Cash and cash equivalents, at end of period	22,755	5,205	1,658
Supplemental disclosure of cash flow information:
Cash paid for income taxes	10	4	1
Cash paid for interest	347	34
Supplemental non-cash investing and financing activities:
Purchases of property and equipment in accounts payable and accrued and other current liabilities	9	29	$ 22
Issuance of common stock warrants in connection with long-term debt		4
Conversion of redeemable convertible preferred stock into common stock	$ 73,138
Conversion of convertible note and accrued interest into preferred stock		134
Issuance of common stock to settle liability for obligation to issue additional common stock		$ 471

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
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 currently under development and will require significant additional development efforts as the Company continues the development of, and seek regulatory approvals for, STS101 and begin to commercialize it, if approved. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting. There can be no assurance that the Company’s development of STS101 will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained or maintained, that STS101 will obtain necessary government regulatory approval or that STS101 will be commercially viable, if approved. Even if STS101 development efforts are successful, it is uncertain when, if ever, the Company will generate revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biopharmaceutical companies. In addition, the Company is dependent upon the services of its employees, consultants and other third parties. The Company has incurred significant losses and negative cash flows from operations in all periods since its inception and had an accumulated deficit of $43.0 million as of December 31, 2019. 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, 2019, the Company had cash, cash equivalents and marketable securities of $117.9 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, valuation of the convertible preferred stock tranche liability, obligation to issue additional common stock, deferred tax assets, 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 and adjust those estimates and assumptions when facts and circumstances dictate. Actual results could differ 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 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 reevaluate 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. Other income (expense), net, 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 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. The carrying amounts of the convertible preferred stock tranche liability and the obligation to issue additional common stock represent their fair value. 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, 2019 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. Convertible Preferred Stock Tranche Liability The Company was obligated to issue additional shares of Series A convertible preferred stock at future dates pursuant to the Series A convertible preferred stock purchase agreement. This obligation was determined to be a freestanding instrument that should be accounted for as a liability. At initial recognition, the Company recorded the convertible preferred stock tranche liability on the balance sheet at its fair value. The liability was subject to remeasurement at each balance sheet date, with changes in fair value recognized as a component of other income (expense), net in the statements of operations and comprehensive loss until it was extinguished upon issuance of Series A convertible preferred stock in February 2018 (see Note 7). Obligation to Issue Additional Common Stock The obligation to issue additional common stock to Shin Nippon Biomedical Laboratories, Ltd., or SNBL, pursuant to the Series A convertible preferred stock financing documents (the “SNBL Grant”), was accounted and classified as a liability as it was not indexed to the Company’s stock, specifically because the settlement amount of the SNBL Grant could be affected by future issuance of equity shares or potential equity shares. Therefore, the obligation to issue additional shares of common stock to SNBL was initially measured at fair value and subsequently remeasured at fair value at each reporting date until it was extinguished upon issuance of common stock in February 2018, with changes in fair value recognized as a component of other income (expense), net in the statements of operations and comprehensive loss. 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 in accrued 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 2019, the Company recorded unrealized gains on marketable securities of less than $0.1 million in other comprehensive income (loss). In 2018 and 2017, there were no components of other comprehensive income (loss) or accumulated comprehensive income (loss) and the net loss was equal to the comprehensive 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, convertible preferred stock, convertible preferred stock tranche liability, obligation to issue additional common stock, convertible note, stock options and common stock subject to repurchase related to unvested restricted stock awards 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 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. New Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASC 842”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. ASC 842 provides a lessee with an option to not account for leases with a term of 12 month or less as leases in the scope of the new standard. ASC 842 supersedes the previous leases standard, ASC 840 Leases. For public business entities, this ASU is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, and should be applied through a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. For all other entities, this ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within fiscal years beginning after December 15, 2021. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU No. 2016-02 is effective for the Company for the year ended December 31, 2021, and all interim periods within. The Company will adopt this ASU on January 1, 2021. In July 2018, the FASB issued supplemental adoption guidance and clarification to ASC 842 within ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements. ASU No. 2018-11 provides another transition method in addition to the existing modified retrospective transition method by allowing entities to initially apply the new leasing standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842) Codification Improvements, which further clarifies the determination of fair value of the underlying asset by lessors that are not manufacturers or dealers and modifies transition disclosure requirements for changes in accounting principles and other technical updates. In November 2019, the FASB issued ASU 2019-10, which delays the adoption dates for ASU 2016-02 for non-public entities. The Company is currently evaluating the impact the adoption of these ASUs will have on its financial statements and related disclosures. The Company expects to recognize a right-of-use asset and corresponding lease liability for its real estate operating leases upon adoption. See Note 8 for more information related to the Company’s lease obligations, which are presented on an undiscounted basis therein. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326), to provide financial statement users with more useful information about expected credit losses, which was subsequently updated by ASU 2019-04, Codification Improvements to Topic 326, Financial Instrument - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, and ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an In August 2018, the FASB issued ASU No.2018-13 (Topic 820), Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements on fair value measurement in Topic 820. For public entities, ASU 2018-013 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company will adopt this ASU on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company’s financial statements.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
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, 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 $ 10,062 $ — $ — $ 10,062 Overnight repurchase agreements (1) 14,000 — — 14,000 Corporate bonds — 64,285 — 64,285 Asset backed securities — 20,781 — 20,781 Marketable securities 24,062 85,066 — 109,128 Money market funds (1) 8,730 — — 8,730 Total fair value of assets $ 32,792 $ 85,066 $ — $ 117,858 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. As of December 31, 2018, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2018 Quoted Price in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets Money market funds (1) $ 5,184 $ — $ — $ 5,184 Total fair value of assets $ 5,184 $ — $ — $ 5,184 (1) Included in cash and cash equivalents on the balance sheet. The following tables set forth the changes in the fair value of Level 3 financial liabilities (in thousands): Convertible Preferred Stock Tranche Liability Obligation to Issue Additional Common Stock Fair value at January 1, 2017 $ 291 $ 138 Change in fair value included in other income (expense), net — 232 Fair value as of December 31, 2017 $ 291 $ 370 Change in fair value included in other income (expense), net (291 ) 102 Settlement of obligation — (472 ) Fair value as of December 31, 2018 $ — $ — The Company used the Black-Scholes option pricing model to estimate the fair value of the convertible preferred stock tranche liability (see Note 7). The Company used the fair value of the Company’s common stock to estimate the fair value of the obligation to issue additional common stock (see Note 14).

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2019
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) 2019 2018 Furniture and fixtures 3 $ 58 $ 13 Leasehold improvements Shorter of useful life or lease term 62 7 Machinery and equipment 3-5 805 375 Tooling 3-5 102 117 1,027 512 Less: Accumulated depreciation (195 ) (67 ) $ 832 $ 445 Depreciation is computed using the straight-line method. Depreciation expense was $0.1 million, $0.1 million and less than $0.1 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Accrued Liabilities and Other C

Accrued Liabilities and Other Current Liabilities	12 Months Ended
	Dec. 31, 2019
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, December 31, 2019 2018 Accrued salaries and benefits $ 1,145 $ 553 Accrued research and development expenses 88 772 Accrued professional services 248 85 Accrued interest 27 29 Other 202 58 $ 1,710 $ 1,497

Convertible Note

Convertible Note	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Convertible Note	5 . Convertible Note On August 1, 2016, the Company issued a $0.1 million convertible promissory note (the “Convertible Note”) to one of its founders and existing shareholders (see Note 14) bearing simple interest at 5.0% per annum. The outstanding amount was due and payable upon the earlier of (i) a demand made by the investor after the two-year anniversary of the initial issuance, or (ii) the continued occurrence of an event of default when declared due and payable by the investor. The Convertible Note was amended on December 16, 2016 to redefine the automatic conversion trigger from a qualified financing before the maturity date of $7.0 million to the occurrence of the subsequent closing as defined in the Series A Preferred Stock Purchase Agreement dated December 16, 2016. The Convertible Note included an embedded derivative that was required to be bifurcated and accounted for separately as a derivative liability. The derivative instrument was measured at fair value and recorded as a discount to the Convertible Note. The discount was amortized to interest expense over the term of the Convertible Note using the effective interest rate and the derivative liability was remeasured at each reporting period, with changes in value recorded to other income (expense), net on the Company’s statements of operations and comprehensive loss. The estimated fair value of the derivative instrument was immaterial as of the issuance date and December 31, 2017, due to the probability of occurrence of the underlying events being remote. Upon the subsequent financing, which occurred in February 2018 (see Note 9), the Convertible Note, including all accrued interest of less than $0.1 million at the date of the subsequent financing, converted into 33,741 shares of Series A preferred stock at $3.187 per share, which was equal to 80.0% of the price per share paid by the cash purchasers. The conversion of the Convertible Note was accounted for as an extinguishment with the loss on extinguishment of the Convertible Note of less than $0.1 million recorded in other income (expense), net on the Company’s statements of operations and comprehensive loss. Total interest expense for each of the years ended December 31, 2017 and December 31, 2018 was less than $0.1 million. At December 31, 2017, accrued interest expense of less than $0.1 million was included in accrued liabilities on the Company’s balance sheet. Amortization of debt discount for each of the years ended December 31, 2017 and December 31, 2018 was less than $0.1 million and was accounted for as interest expense on the Company’s statements of operations and comprehensive loss. Loss on revaluation of derivative liability for each of the years ended December 31, 2017 and December 31, 2018 was less than $0.1 million.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Long-Term Debt	6. 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. 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, 2019, the term loan advances, net of debt discount and debt issuance costs, were $4.9 million and are included in current portion of long-term debt and long-term debt on the Company’s balance sheet. In December 2019, the Company repaid $0.2 million of term loan. As of December 31, 2019, the future contractual maturities of debt by fiscal year are as follows (in thousands): 2020 $ 2,000 2021 2,000 2022 833 Total future maturities of debt $ 4,833 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”): Year Ended December 31, 2018 Expected term (years) 10.0 Expected volatility 74.8 % Risk-free interest rate 3.1 % Dividend yield 0 % 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.

Convertible Preferred Stock Tra

Convertible Preferred Stock Tranche Liability	12 Months Ended
	Dec. 31, 2019
Convertible Preferred Stock Tranche Liability [Abstract]
Convertible Preferred Stock Tranche Liability	7. Convertible Preferred Stock Tranche Liability In December 2016, the Company executed a Series A Preferred Stock Purchase Agreement to sell shares of Series A convertible preferred stock. The Series A convertible preferred stock issuance was structured in two tranches: (i) 1,506,307 shares at $3.9833 per share (the “First Tranche”) and (ii) 1,506,307 shares at $3.9833 per share on achieving a certain development milestone by the Company or at the option of First Tranche investors at any time before such milestone is achieved (the “Second Tranche”). In December 2016, the Company recognized a convertible preferred stock tranche liability for the First Tranche investors’ right to purchase from the Company, on the same terms, additional shares of Series A convertible preferred stock. The convertible preferred stock tranche liability was valued using the OPM, which resulted in an initial fair value of $0.3 million for the Company’s obligation to sell the convertible preferred stock related to the Second Tranche. On December 31, 2017, the convertible preferred stock tranche liability was revalued, and the Company recorded a gain of less than $0.1 million in other income (expense), net for the year then ended. On February 1, 2018, the Company issued an additional 1,506,307 shares of Series A convertible preferred stock at $3.9833 per share thereby extinguishing the convertible preferred stock tranche liability for the Second Tranche. Immediately prior to the closing of the Second Tranche, the Company remeasured the convertible preferred stock tranche liability to its then fair value of $0 and recorded a gain of $0.3 million in other income (expense), net.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8 . Commitments and Operating Leases The Company entered into a one-year lease agreement for office space in South San Francisco, California. Total rent payment under the agreement, which ran from January 1, 2017 to December 31, 2017, was $0.1 million. 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 $0.2 million, $0.1 million and $0.1 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, 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, 2019 were as follows (in thousands): Operating Leases 2020 $ 299 2021 195 2022 83 Total minimum lease payments $ 577 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, 2019, December 31, 2018 and December 31, 2017, 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
	Dec. 31, 2019
Equity [Abstract]
Convertible Preferred Stock	9. Convertible Preferred Stock The Company has authorized 10,000,000 shares of convertible preferred stock, $0.0001 par value. In December 2016, the Company issued 1,506,307 shares of its Series A convertible preferred stock at $3.9833 per share to existing investors for proceeds of $5.8 million which was net of issuance costs of $0.2 million. In February 2018, the Company issued 1,506,307 shares of its Series A convertible preferred stock at $3.9833 per share to existing investors for proceeds of $6.0 million, which was net of issuance costs of less than $0.1 million. The Convertible Note was exchanged for 33,741 shares of Series A convertible preferred stock at $3.187 per share, reflecting accrued interest of less than $0.1 million and a 20% discount to the purchase price per share paid by the cash investors. 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. Upon the closing of the IPO in September 2019, 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 was no issued and outstanding redeemable convertible preferred stock as of December 31, 2019. Issued and outstanding redeemable convertible preferred stock and its principal terms as of December 31, 2018 were as follows (in thousands, except share and per share amounts): Redeemable Convertible Preferred Stock Liquidation Carrying Original Authorized Outstanding Value Amount Issue Price Series A convertible preferred stock 3,191,489 3,046,355 $ 12,134 $ 11,648 $ 3.9833 3,191,489 3,046,355 $ 12,134 $ 11,648 The holders of the convertible preferred stock have various rights and preferences as follows: Liquidation Preference In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, or a deemed liquidation event, the holders of the convertible preferred stock were entitled to receive, prior and in preference to any distribution of any of the assets of the Company to the holders of the common stock by reason of their ownership of such stock, an amount per share for each share of convertible preferred stock held by them equal to the greater of (i) $3.9833 per share (subject to adjustment from time to time for recapitalization), plus all declared but unpaid dividends (if any) on such share of convertible preferred stock, or (ii) such amount per share as would have been payable had all shares of convertible preferred stock been converted into common stock immediately prior to such liquidation. If available assets were insufficient to pay the full liquidation preference of the series of convertible preferred stock, the assets available for distribution to holders of such preferred stock would be distributed among such holders on a pro rata basis. Any remaining funds and assets of the Company legally available for distribution would have been distributed pro rata to the common shareholders in proportion to the number of shares of common stock held by them. Shares of convertible preferred stock were not entitled to convert into shares of common stock in order to participate in any distribution, as shares of common stock, without first foregoing participation in the distribution as shares of convertible preferred Conversion Each share of convertible preferred stock was convertible, at the option of the holder thereof, at any time and from time to time, and without the payment of additional consideration by the holder. The conversion price was determined by dividing the original issuance price applicable to each series of convertible preferred stock, adjusted for any anti-dilution adjustments, by the applicable conversion price for such series. The Company’s convertible preferred stock was convertible into the Company’s shares of common stock on a one-for-one basis. The shares were to automatically convert into fully-paid non-assessable shares of common stock at the conversion rate (a) immediately prior to the closing of a firm commitment underwritten initial public offering pursuant to an effective registration statement filed under the Securities Act of 1933, as amended (the “Securities Act”) provided that the aggregate gross proceeds to the Company are not less than $25.0 million and the per share price is at least three times the original issuance price (a “Qualified IPO”), or (b) at the time upon the receipt of a written request for conversion from the holders of at least a majority of the convertible preferred stock outstanding. Dividends In any calendar year, the holders of outstanding shares of convertible preferred stock were entitled to receive dividends, when, as and if declared by the Company’s board of directors (the “Board of Directors”), at a rate of $0.32 per share, in preference and priority to any declaration, set aside or payment of any distribution on common stock of the Company. The right to receive dividends on shares of convertible preferred stock was not cumulative, and no right to dividends accrued to holders of preferred stock unless dividends were declared. Voting The holders of convertible preferred stock had one vote for each full share of common stock into which their respective shares of convertible preferred stock could then be converted. Redemption and Balance Sheet Classification The convertible preferred stock was recorded as temporary equity because while it was not mandatorily redeemable, it would become redeemable at the option of the stockholders upon the occurrence of certain deemed liquidation events that were considered not solely within the Company’s control.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Common Stock	10. 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, 2019 2018 Conversion of Series A convertible preferred stock — 3,046,355 Exercise of common stock warrants 5,116 10,232 Exercise of outstanding options 1,568,874 829,775 Shares of common stock available for grant under the 2019 Plan 1,778,044 — Shares of common stock available for grant under the 2016 Plan — 114,905 Total 3,352,034 4,001,267

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	11. 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 2020, the number of shares of common stock available for issuance under the 2019 Plan was increased by 695,281 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, 2017 408,510 Additional shares authorized 127,659 Options granted (429,781 ) 429,781 $ 0.89 9.32 Balance, December 31, 2017 106,388 429,781 $ 0.89 Additional shares authorized 408,511 Options granted (402,121 ) 402,121 $ 1.04 9.32 Options cancelled 2,127 (2,127 ) $ 0.90 Balance, December 31, 2018 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 Exercisable as of December 31, 2019 433,396 Vested and expected to vest, December 31, 2019 1,568,874 The weighted-average grant-date fair value of options granted during the years ended December 31, 2019, December 2018 and December 31, 2017 was $3.44, $0.66 and $0.56 per share, respectively. As of December 31, 2019, the total unrecognized stock-based compensation expense for stock options was $3.0 million, which is expected to be recognized over a weighted-average period of 2.8 years. The less than The Company accounts for forfeitures as they occur. The following table summarizes information about stock options outstanding as of December 31, 2019 (in thousands, except share and per share data): Options Outstanding Option Vested and Exercisable Weighted Average Weighted Remaining Aggregate Average Number Contractual Number Intrinsic Exercise Exercise Price Outstanding Term (Years) Exercisable Value Price $ 0.90 261,684 7.34 176,444 $ 3,314 $ 0.90 $ 1.04 402,920 8.55 165,016 $ 3,076 $ 1.04 $ 4.56 781,036 9.37 90,874 $ 1,374 $ 4.56 $ 5.55 51,278 9.60 — $ — $ — $ 13.93 6,000 9.95 — $ — $ — $ 15.00 65,956 9.69 1,062 $ 5 $ 15.00 1,568,874 433,396 $ 7,769 $ 1.76 The following table summarizes information about stock options outstanding as of December 31, 2018 (in thousands, except share and per share data): Options Outstanding Option Vested and Exercisable Weighted Average Weighted Remaining Aggregate Average Number Contractual Number Intrinsic Exercise Exercise Price Outstanding Term (Years) Exercisable Value Price $ 0.90 427,654 8.32 247,880 $ 709 $ 0.90 $ 1.04 402,121 9.36 134,438 $ 366 $ 1.04 829,775 382,318 $ 1,075 $ 0.97 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, 2019 and December 31, 2018. Stock-Based Compensation Associated with Awards to Employees and Non-employees During the years ended December 31, 2019, December 31, 2018 and December 31, 2017, the Company granted stock options to employees to purchase 1,023,012, 402,121 and 427,654 shares of common stock, respectively. During the year ended December 31, 2019, December 31, 2018 and December 31, 2017 the Company granted 5,106, 0 and 2,127 stock options to its non-employees, respectively. The fair value of stock options was valued using the following assumptions: December 31, 2019 2018 2017 Expected term (years) 6.0 - 6.1 5.5 - 6.1 5.5 - 6.3 Expected volatility 63.6% - 74.9% 77.2% - 78.6% 65.2% - 67.8% Risk-free interest rate 1.4% - 2.5% 2.9% 1.8% - 2.3% Dividend yield 0% 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 did not have any 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, January 1, 2017 95,744 $ — Vested (31,915 ) $ — Unvested, December 31, 2017 63,829 $ — Vested (31,915 ) $ — Unvested, December 31, 2018 31,914 $ — Vested (31,914 ) $ — Unvested, December 31, 2019 — $ — 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. The offering period and purchase period will be determined by the board of directors. As of December 31, 2019, no offerings had been authorized. In January 2020, the number of shares of common stock available for issuance under the ESPP was increased by 173,280 shares as a result of the automatic increase provision in the ESPP. Stock-Based Compensation Expense Total Year Ended December 31, 2019 2018 2017 Research and development $ 334 $ 69 $ 13 General and administrative 413 101 53 $ 747 $ 170 $ 66

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	12. 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, 2019 2018 2017 Numerator: Net loss attributable to common stockholders $ (28,175 ) $ (7,346 ) $ (5,172 ) Denominator: Weighted-average shares outstanding 5,879,820 1,074,690 638,297 Less: weighted-average unvested restricted shares and shares subject to repurchase (15,870 ) (47,785 ) (79,700 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 5,863,950 1,026,905 558,597 Net loss per share attributable to common stockholders, basic and diluted $ (4.80 ) $ (7.15 ) $ (9.26 ) 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, 2019 2018 2017 Convertible preferred stock — 3,046,355 1,506,307 Convertible Note — — 33,603 Convertible preferred stock tranche liability — — 1,506,307 Options to purchase common stock 1,568,874 829,775 429,781 Unvested restricted common stock awards — 31,914 63,829 Obligation to issue additional common stock — — 374,695 Warrants to purchase common stock 5,116 10,232 — Total 1,573,990 3,918,276 3,914,522

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes No provision for income taxes was recorded for the years ended December 31, 2019, December 31, 2018 and December 31, 2017. 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, 2019 2018 2017 Tax at federal statutory income tax rate $ (5,917 ) $ (1,542 ) $ (1,758 ) Change in valuation allowance 6,708 1,527 1,099 Permanent differences 124 84 105 Prior year true ups 6 — (70 ) Research and development credits (873 ) (69 ) — State income taxes 1 1 — Federal tax rate change — — 625 Other (48 ) — — Tax at effective income tax rate $ 1 $ 1 $ 1 Significant components of the Company’s net deferred tax assets are summarized as follows (in thousands): December 31, 2019 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 8,250 $ 2,456 $ 995 Research and development credit carryforwards 1,118 188 54 Stock-based compensation 45 4 — Accruals and other 236 134 61 Gross deferred tax assets 9,649 2,782 1,110 Less: Valuation allowance (9,491 ) (2,696 ) (1,103 ) Deferred tax assets, net of valuation allowance 158 86 7 Deferred tax liabilities: Property and equipment (158 ) (86 ) (7 ) Net deferred tax assets $ — $ — $ — As of December 31, 2019, the Company had federal and state net operating loss carryforwards (“NOLs”) of $39.1 million and $0.4 million, respectively. The Company also has California state research and development (“R&D”) credit carryforwards of $0.3 million, which do not expire and Federal R&D credit carryforwards of $1.1 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, 2019, the Company had converted $0.7 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, 2017 $ — Increase related to current year tax positions 23 Balance as of December 31, 2017 $ 23 Increase related to current year tax positions 134 Balance as of December 31, 2018 $ 157 Increase related to current year tax positions 196 Decrease related to prior year tax positions (115 ) Balance as of December 31, 2019 $ 238 The Company’s policy is to account for interest and penalties as income tax expense. As of December 31, 2019, the Company had no interest related to unrecognized tax benefits. No amounts of penalties related to unrecognized tax benefits were recognized in the provision for income taxes. The Company does not anticipate any significant change within twelve months following the date of the filing of this Annual Report on Form 10-K The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. The Company is subject to U.S. federal and state income tax examination for calendar tax years beginning in 2016 due to net operating losses that are being carried forward for tax purposes.

Related Party Transaction

Related Party Transaction	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	14. Related Party Transactions with SNBL In June 2016, the Company and SNBL, entered into a licensing and assignment agreement (the “SNBL License”), which was amended and restated in December 2016 and further amended in January 2017, April 2017, and October 2017. Under the SNBL License, SNBL assigned to the Company certain patent rights other patent rights Under the SNBL License, the Company reimbursed SNBL for costs relating to its incorporation and prosecution and maintenance of the product-specific patents. The Company also agreed to make royalty payments based on a low single-digit percentage of worldwide net sales of DHE Products and DHE Combination Products, payable on a product-by-product and country-by-country basis until the latest of the expiration of the last-to-expire patent covering such product and the ten year anniversary of the first commercial sale of such product in such country. The royalty payments are subject to reductions based on royalties paid to any third party under a license to such third party’s patent rights. The Company has the sole right to control the prosecution and maintenance of, and to enforce, the patent rights that SNBL assigned to the Company. SNBL has the first right to control the prosecution and maintenance of the patent rights that SNBL licensed to the Company. The Company has step in rights if SNBL does not continue such prosecution and maintenance. The Company also have the first right to enforce such licensed patent rights with respect to certain infringing products. If the Company does not bring an action to enforce such patents against infringing activities that involve such infringing products, SNBL has the right to bring such an action. The SNBL License will continue on a country-by-country and product-by-product basis until the expiration of the obligation to pay royalties with respect such product and country. The Company may terminate the SNBL License in its entirety without cause on ninety days’ prior written notice. SNBL may terminate the SNBL License for our material breach that remains uncured for ninety days. SNBL may also terminate the SNBL License if the Company challenges the licensed patents, or if the Company assists any third party in challenging such patents. In addition, SNBL has the right to terminate the SNBL License upon the Company’s insolvency. There were no sales of products under the SNBL License during the years ended December 31, 2019, December 31, 2018 and December 31, 2017. In connection with the SNBL License, in July 2016, SNBL entered into a Common Stock Purchase Agreement with the Company to purchase of 510,638 shares of the Company’s common stock at its par price of $0.0001. The Company recorded the estimated fair value of the SNBL License of $0.7 million as of the SNBL License date as additional paid-in capital as contribution by SNBL for 510,638 shares of common stock purchased by SNBL. In August 2016, the Company signed the Convertible Note with SNBL for $0.1 million, which was later amended in December 2016 (Note 5). In February 2018, the Convertible Note and related accrued interest of less than $0.1 million converted into 33,741 shares of Company’s Series A convertible preferred stock. In December 2016, as part of the Series A convertible preferred stock financing, the Company granted to SNBL a right to obtain shares of Common Stock for no additional paid-in capital upon the occurrence of subsequent closings of the Company’s Series A convertible preferred stock financing such that SNBL’s percentage ownership of the fully-diluted capitalization of the Company following the SNBL Grant would be equal to 20% following the final closing of the Series A convertible preferred stock financing. In return, SNBL assigned product-specific know-how and patents relating to STS101 to the Company. The Company recorded an additional fair value of the SNBL License of $1.4 million in December 2016. The obligation to issue additional common stock to SNBL was accounted and classified for as a liability as it was not indexed to the Company’s own stock, specifically because the settlement amount of the SNBL Grant could be affected by future issuance of equity shares or potential equity shares. Therefore, the obligation to issue additional common stock to SNBL was initially measured at fair value and subsequently remeasured at fair value at each reporting date until it expires or is exercised. Upon the initial issuance, the Company recorded the obligation to issue additional common stock to SNBL at its estimated fair value of $0.1 million based on the estimated fair value of the Company’s common stock of $0.90 per share and estimated 0.3 million shares of the Company’s common stock to be issued to settle such obligation adjusted for the probability or the occurrence of the subsequent closing of the Series A convertible preferred stock financing. The difference between the additional fair value of the SNBL License and the estimated fair value of the obligation to issue additional common stock to SNBL, of $1.3 million was accounted as additional paid-in capital. On December 31, 2017, the obligation to issue additional common stock to SNBL was remeasured to its estimated fair value of $0.4 million and $0.2 million was recorded as a loss in other income (expense), net for the year ended December 31, 2017. In February 2018, the Company issued 476,897 shares of common stock for no consideration. Upon extinguishment of the obligation to issue additional common stock to SNBL, the obligation to issue additional common stock to SNBL was remeasured to its estimated fair value of $0.5 million and $0.1 million was recorded as a loss in other income (expense), net for the year ended December 31, 2018, and the estimated fair value of $0.5 million of the obligation to issue additional common stock to SNBL was reclassified to additional paid-in capital on the balance sheet. 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, less than $0.1 million and $0.2 million, which are included in research and development expenses on the statement of operations for the years ended December 31, 2019, 2018 and 2017, respectively. Amounts due to SNBL in connection with these expenses of less than $0.1 million are included in accrued liabilities on the balance sheets as of December 31, 2019 and 2018. 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 (see Note 9). 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
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations Data (unaudited)	15. 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, 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 ) Three months ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 (In thousands, except per share amounts) Loss from operations $ (1,409 ) $ (2,222 ) $ (1,600 ) $ (2,284 ) Net loss $ (1,212 ) $ (2,203 ) $ (1,587 ) $ (2,344 ) Net loss per share attributable to common stockholders, basic and diluted $ (1.36 ) $ (2.07 ) $ (1.48 ) $ (2.17 )

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
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 currently under development and will require significant additional development efforts as the Company continues the development of, and seek regulatory approvals for, STS101 and begin to commercialize it, if approved. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting. There can be no assurance that the Company’s development of STS101 will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained or maintained, that STS101 will obtain necessary government regulatory approval or that STS101 will be commercially viable, if approved. Even if STS101 development efforts are successful, it is uncertain when, if ever, the Company will generate revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biopharmaceutical companies. In addition, the Company is dependent upon the services of its employees, consultants and other third parties. The Company has incurred significant losses and negative cash flows from operations in all periods since its inception and had an accumulated deficit of $43.0 million as of December 31, 2019. 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, 2019, the Company had cash, cash equivalents and marketable securities of $117.9 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, valuation of the convertible preferred stock tranche liability, obligation to issue additional common stock, deferred tax assets, 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 and adjust those estimates and assumptions when facts and circumstances dictate. Actual results could differ 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
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 reevaluate 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. Other income (expense), net, 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
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. The carrying amounts of the convertible preferred stock tranche liability and the obligation to issue additional common stock represent their fair value.
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, 2019 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.
Convertible Preferred Stock Tranche Liability	Convertible Preferred Stock Tranche Liability The Company was obligated to issue additional shares of Series A convertible preferred stock at future dates pursuant to the Series A convertible preferred stock purchase agreement. This obligation was determined to be a freestanding instrument that should be accounted for as a liability. At initial recognition, the Company recorded the convertible preferred stock tranche liability on the balance sheet at its fair value. The liability was subject to remeasurement at each balance sheet date, with changes in fair value recognized as a component of other income (expense), net in the statements of operations and comprehensive loss until it was extinguished upon issuance of Series A convertible preferred stock in February 2018 (see Note 7).
Obligation to Issue Additional Common Stock	Obligation to Issue Additional Common Stock The obligation to issue additional common stock to Shin Nippon Biomedical Laboratories, Ltd., or SNBL, pursuant to the Series A convertible preferred stock financing documents (the “SNBL Grant”), was accounted and classified as a liability as it was not indexed to the Company’s stock, specifically because the settlement amount of the SNBL Grant could be affected by future issuance of equity shares or potential equity shares. Therefore, the obligation to issue additional shares of common stock to SNBL was initially measured at fair value and subsequently remeasured at fair value at each reporting date until it was extinguished upon issuance of common stock in February 2018, with changes in fair value recognized as a component of other income (expense), net in the statements of operations and comprehensive loss.
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 in accrued 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 2019, the Company recorded unrealized gains on marketable securities of less than $0.1 million in other comprehensive income (loss). In 2018 and 2017, there were no components of other comprehensive income (loss) or accumulated comprehensive income (loss) and the net loss was equal to the comprehensive 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, convertible preferred stock, convertible preferred stock tranche liability, obligation to issue additional common stock, convertible note, stock options and common stock subject to repurchase related to unvested restricted stock awards 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
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. New Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASC 842”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. ASC 842 provides a lessee with an option to not account for leases with a term of 12 month or less as leases in the scope of the new standard. ASC 842 supersedes the previous leases standard, ASC 840 Leases. For public business entities, this ASU is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, and should be applied through a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. For all other entities, this ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within fiscal years beginning after December 15, 2021. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU No. 2016-02 is effective for the Company for the year ended December 31, 2021, and all interim periods within. The Company will adopt this ASU on January 1, 2021. In July 2018, the FASB issued supplemental adoption guidance and clarification to ASC 842 within ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements. ASU No. 2018-11 provides another transition method in addition to the existing modified retrospective transition method by allowing entities to initially apply the new leasing standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842) Codification Improvements, which further clarifies the determination of fair value of the underlying asset by lessors that are not manufacturers or dealers and modifies transition disclosure requirements for changes in accounting principles and other technical updates. In November 2019, the FASB issued ASU 2019-10, which delays the adoption dates for ASU 2016-02 for non-public entities. The Company is currently evaluating the impact the adoption of these ASUs will have on its financial statements and related disclosures. The Company expects to recognize a right-of-use asset and corresponding lease liability for its real estate operating leases upon adoption. See Note 8 for more information related to the Company’s lease obligations, which are presented on an undiscounted basis therein. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326), to provide financial statement users with more useful information about expected credit losses, which was subsequently updated by ASU 2019-04, Codification Improvements to Topic 326, Financial Instrument - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, and ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an In August 2018, the FASB issued ASU No.2018-13 (Topic 820), Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements on fair value measurement in Topic 820. For public entities, ASU 2018-013 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company will adopt this ASU on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company’s financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured and Recognized at Fair Value	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 $ 10,062 $ — $ — $ 10,062 Overnight repurchase agreements (1) 14,000 — — 14,000 Corporate bonds — 64,285 — 64,285 Asset backed securities — 20,781 — 20,781 Marketable securities 24,062 85,066 — 109,128 Money market funds (1) 8,730 — — 8,730 Total fair value of assets $ 32,792 $ 85,066 $ — $ 117,858 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. As of December 31, 2018, financial assets measured and recognized at fair value were as follows (in thousands): Fair Value Measurements at December 31, 2018 Quoted Price in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets Money market funds (1) $ 5,184 $ — $ — $ 5,184 Total fair value of assets $ 5,184 $ — $ — $ 5,184 (1) Included in cash and cash equivalents on the balance sheet.
Schedule of Changes in the Fair Value of Level 3 Financial Liabilities	The following tables set forth the changes in the fair value of Level 3 financial liabilities (in thousands): Convertible Preferred Stock Tranche Liability Obligation to Issue Additional Common Stock Fair value at January 1, 2017 $ 291 $ 138 Change in fair value included in other income (expense), net — 232 Fair value as of December 31, 2017 $ 291 $ 370 Change in fair value included in other income (expense), net (291 ) 102 Settlement of obligation — (472 ) Fair value as of December 31, 2018 $ — $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2019
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) 2019 2018 Furniture and fixtures 3 $ 58 $ 13 Leasehold improvements Shorter of useful life or lease term 62 7 Machinery and equipment 3-5 805 375 Tooling 3-5 102 117 1,027 512 Less: Accumulated depreciation (195 ) (67 ) $ 832 $ 445

Accrued Liabilities and Other_2

Accrued Liabilities and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities and Other Current Liabilities	Accrued liabilities consisted of the following (in thousands): December 31, December 31, 2019 2018 Accrued salaries and benefits $ 1,145 $ 553 Accrued research and development expenses 88 772 Accrued professional services 248 85 Accrued interest 27 29 Other 202 58 $ 1,710 $ 1,497

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Summary of Future Contractual Maturities of Debt	As of December 31, 2019, the future contractual maturities of debt by fiscal year are as follows (in thousands): 2020 $ 2,000 2021 2,000 2022 833 Total future maturities of debt $ 4,833
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”): Year Ended December 31, 2018 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
	Dec. 31, 2019
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, 2019 were as follows (in thousands): Operating Leases 2020 $ 299 2021 195 2022 83 Total minimum lease payments $ 577

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Issued and Outstanding Redeemable Convertible Preferred Stock and Principal Terms	Issued and outstanding redeemable convertible preferred stock and its principal terms as of December 31, 2018 were as follows (in thousands, except share and per share amounts): Redeemable Convertible Preferred Stock Liquidation Carrying Original Authorized Outstanding Value Amount Issue Price Series A convertible preferred stock 3,191,489 3,046,355 $ 12,134 $ 11,648 $ 3.9833 3,191,489 3,046,355 $ 12,134 $ 11,648

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 2018 Conversion of Series A convertible preferred stock — 3,046,355 Exercise of common stock warrants 5,116 10,232 Exercise of outstanding options 1,568,874 829,775 Shares of common stock available for grant under the 2019 Plan 1,778,044 — Shares of common stock available for grant under the 2016 Plan — 114,905 Total 3,352,034 4,001,267

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
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, 2017 408,510 Additional shares authorized 127,659 Options granted (429,781 ) 429,781 $ 0.89 9.32 Balance, December 31, 2017 106,388 429,781 $ 0.89 Additional shares authorized 408,511 Options granted (402,121 ) 402,121 $ 1.04 9.32 Options cancelled 2,127 (2,127 ) $ 0.90 Balance, December 31, 2018 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 Exercisable as of December 31, 2019 433,396 Vested and expected to vest, December 31, 2019 1,568,874
Summary of Information about Stock Options Outstanding	The following table summarizes information about stock options outstanding as of December 31, 2019 (in thousands, except share and per share data): Options Outstanding Option Vested and Exercisable Weighted Average Weighted Remaining Aggregate Average Number Contractual Number Intrinsic Exercise Exercise Price Outstanding Term (Years) Exercisable Value Price $ 0.90 261,684 7.34 176,444 $ 3,314 $ 0.90 $ 1.04 402,920 8.55 165,016 $ 3,076 $ 1.04 $ 4.56 781,036 9.37 90,874 $ 1,374 $ 4.56 $ 5.55 51,278 9.60 — $ — $ — $ 13.93 6,000 9.95 — $ — $ — $ 15.00 65,956 9.69 1,062 $ 5 $ 15.00 1,568,874 433,396 $ 7,769 $ 1.76 The following table summarizes information about stock options outstanding as of December 31, 2018 (in thousands, except share and per share data): Options Outstanding Option Vested and Exercisable Weighted Average Weighted Remaining Aggregate Average Number Contractual Number Intrinsic Exercise Exercise Price Outstanding Term (Years) Exercisable Value Price $ 0.90 427,654 8.32 247,880 $ 709 $ 0.90 $ 1.04 402,121 9.36 134,438 $ 366 $ 1.04 829,775 382,318 $ 1,075 $ 0.97
Schedule of Fair Value Assumptions of Stock Options	The fair value of stock options was valued using the following assumptions: December 31, 2019 2018 2017 Expected term (years) 6.0 - 6.1 5.5 - 6.1 5.5 - 6.3 Expected volatility 63.6% - 74.9% 77.2% - 78.6% 65.2% - 67.8% Risk-free interest rate 1.4% - 2.5% 2.9% 1.8% - 2.3% Dividend yield 0% 0% 0%
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, January 1, 2017 95,744 $ — Vested (31,915 ) $ — Unvested, December 31, 2017 63,829 $ — Vested (31,915 ) $ — Unvested, December 31, 2018 31,914 $ — Vested (31,914 ) $ — Unvested, December 31, 2019 — $ —
Summary of Stock Based Compensation Expense	Total Year Ended December 31, 2019 2018 2017 Research and development $ 334 $ 69 $ 13 General and administrative 413 101 53 $ 747 $ 170 $ 66

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 2018 2017 Numerator: Net loss attributable to common stockholders $ (28,175 ) $ (7,346 ) $ (5,172 ) Denominator: Weighted-average shares outstanding 5,879,820 1,074,690 638,297 Less: weighted-average unvested restricted shares and shares subject to repurchase (15,870 ) (47,785 ) (79,700 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 5,863,950 1,026,905 558,597 Net loss per share attributable to common stockholders, basic and diluted $ (4.80 ) $ (7.15 ) $ (9.26 )
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, 2019 2018 2017 Convertible preferred stock — 3,046,355 1,506,307 Convertible Note — — 33,603 Convertible preferred stock tranche liability — — 1,506,307 Options to purchase common stock 1,568,874 829,775 429,781 Unvested restricted common stock awards — 31,914 63,829 Obligation to issue additional common stock — — 374,695 Warrants to purchase common stock 5,116 10,232 — Total 1,573,990 3,918,276 3,914,522

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 2018 2017 Tax at federal statutory income tax rate $ (5,917 ) $ (1,542 ) $ (1,758 ) Change in valuation allowance 6,708 1,527 1,099 Permanent differences 124 84 105 Prior year true ups 6 — (70 ) Research and development credits (873 ) (69 ) — State income taxes 1 1 — Federal tax rate change — — 625 Other (48 ) — — Tax at effective income tax rate $ 1 $ 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, 2019 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 8,250 $ 2,456 $ 995 Research and development credit carryforwards 1,118 188 54 Stock-based compensation 45 4 — Accruals and other 236 134 61 Gross deferred tax assets 9,649 2,782 1,110 Less: Valuation allowance (9,491 ) (2,696 ) (1,103 ) Deferred tax assets, net of valuation allowance 158 86 7 Deferred tax liabilities: Property and equipment (158 ) (86 ) (7 ) 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, 2017 $ — Increase related to current year tax positions 23 Balance as of December 31, 2017 $ 23 Increase related to current year tax positions 134 Balance as of December 31, 2018 $ 157 Increase related to current year tax positions 196 Decrease related to prior year tax positions (115 ) Balance as of December 31, 2019 $ 238

Quarterly Results of Operatio_2

Quarterly Results of Operations Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
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, 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 ) Three months ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 (In thousands, except per share amounts) Loss from operations $ (1,409 ) $ (2,222 ) $ (1,600 ) $ (2,284 ) Net loss $ (1,212 ) $ (2,203 ) $ (1,587 ) $ (2,344 ) Net loss per share attributable to common stockholders, basic and diluted $ (1.36 ) $ (2.07 ) $ (1.48 ) $ (2.17 )

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, 2019USD ($)segment$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Sep. 12, 2019$ / 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				300,000,000	5,319,148
Common stock, par value (in dollars per share) | $ / shares				$ 0.0001	$ 0.0001
Common stock, shares issued				17,382,047	1,083,280
Accumulated deficit | $				$ 43,001,000	$ 14,826,000
cash, cash equivalents and marketable securities | $				$ 117,900,000
Reverse stock split, conversion ratio		0.21
Number of operating segment | segment				1
Number of reportable segment | segment				1
Estimated useful lives of assets				three to five years
Impairments of long-lived assets | $				$ 0	0
Unrealized gains on marketable securities | $				17,000
Other comprehensive income | $				17,000	$ 0	$ 0
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Unrealized gains on marketable securities | $				$ 100,000
Common Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued				6,052,116
IPO | Common Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Share issued	5,500,000
Shares issued, price per share | $ / shares	$ 15
Shares issued upon conversion	9,936,341
Common stock, shares authorized							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							10,000,000
Preferred stock per 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			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	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, 2019	Dec. 31, 2018
Assets
Marketable securities		$ 109,128
Money market funds	[1]		$ 5,184
Total fair value of assets		117,858	5,184
Marketable Securities Amortized Cost		109,128
Marketable Securities Gross Unrealized Gains		25
Marketable Securities Gross Unrealized Losses		(8)
Marketable Securities Estimate Fair Value		109,145
Amortized Cost		117,858
Gross Unrealized Gains		25
Gross Unrealized Losses		(8)
Estimate Fair Value		117,875
U.S. Government Bonds
Assets
Marketable securities		10,062
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		64,285
Marketable Securities Amortized Cost		64,285
Marketable Securities Gross Unrealized Gains		17
Marketable Securities Gross Unrealized Losses		(7)
Marketable Securities Estimate Fair Value		64,295
Asset Backed Securities
Assets
Marketable securities		20,781
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]	8,730
Amortized Cost	[1]	8,730
Estimate Fair Value	[1]	8,730
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Marketable securities		24,062
Money market funds	[1]		5,184
Total fair value of assets		32,792	$ 5,184
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government Bonds
Assets
Marketable securities		10,062
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]	8,730
Significant Other Observable Inputs (Level 2)
Assets
Marketable securities		85,066
Total fair value of assets		85,066
Significant Other Observable Inputs (Level 2) | Corporate Bonds
Assets
Marketable securities		64,285
Significant Other Observable Inputs (Level 2) | Asset Backed Securities
Assets
Marketable securities		$ 20,781
[1]	Included in cash and cash equivalents on the balance sheet.

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Changes in the Fair Value of Level 3 Financial Liabilities (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Convertible Preferred Stock Tranche Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ 291	$ 291
Change in fair value included in other income (expense), net	$ (291)
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Income [Extensible List]	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Balance, end of period		$ 291
Obligation to Issue Additional Common Stock
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ 370	138
Change in fair value included in other income (expense), net	$ 102	$ 232
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Income [Extensible List]	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Settlement of obligation	$ (472)
Balance, end of period		$ 370

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,027	$ 512
Less: Accumulated depreciation	(195)	(67)
Property and equipment, net	$ 832	$ 445
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment useful life	3 years	3 years
Property and equipment, gross	$ 58	$ 13
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment useful life	Shorter of useful life or lease term	Shorter of usefullife or lease term
Property and equipment, gross	$ 62	$ 7
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 805	$ 375
Machinery and Equipment | Minimum [Member]
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	$ 102	$ 117
Tooling | Minimum [Member]
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

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Depreciation expense	$ 141,000	$ 57,000	$ 10,000
Maximum
Property Plant And Equipment [Line Items]
Depreciation expense			$ 100,000

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, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued salaries and benefits	$ 1,145	$ 553
Accrued research and development expenses	88	772
Accrued professional services	248	85
Accrued interest	27	29
Other	202	58
Total	$ 1,710	$ 1,497

Convertible Note - Additional I

Convertible Note - Additional Information (Details) - USD ($)	Dec. 16, 2016	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Aug. 01, 2016
Debt Instrument [Line Items]
Conversion of convertible note and accrued interest into preferred stock				$ 134,000
Loss on extinguishment of debt conversion				(4,000)
Total interest expense			$ 482,000	90,000	$ 15,000
Convertible Note
Debt Instrument [Line Items]
Debt instrument, face amount						$ 100,000
Debt instrument, interest rate						5.00%
Convertible note automatic conversion trigger from qualify financing	$ 7,000,000
Convertible Note | Maximum
Debt Instrument [Line Items]
Conversion of convertible note and accrued interest into preferred stock		$ 100,000
Total interest expense				100,000	100,000
Accrued interest expenses		100,000			100,000
Amortization of debt discount				100,000	100,000
Loss on revaluation of derivative liability				$ 100,000	$ 100,000
Convertible Note | Other Income (Expense), Net | Maximum
Debt Instrument [Line Items]
Loss on extinguishment of debt conversion		$ 100,000
Convertible Note | Series A Convertible Preferred Stock
Debt Instrument [Line Items]
Debt instrument converted, shares issued		33,741
Shares issued, price per share		$ 3.187
Debt instrument converted, price per share paid by cash purchasers		80.00%

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details)	Oct. 26, 2018USD ($)$ / sharesshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2019USD ($)Paymentshares	Dec. 31, 2018shares
Debt Instrument [Line Items]
Long-term debt net of debt discount and issuance costs		$ 4,833,000	$ 4,833,000
Term loan repaid			$ 167,000
Number of shares to be called by warrants issued | shares		5,116	5,116	10,232
Term Loan
Debt Instrument [Line Items]
Term loan repaid		$ 200,000
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%
Long-term debt net of debt discount and issuance costs		$ 4,900,000	$ 4,900,000
Number of shares to be called by warrants issued | shares	10,232
Warrants, exercise price | $ / shares	$ 1.04
Warrants, term	10 years
Debt issuance cost final payment recognized as additional interest expense			$ 300,000
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
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, 2019USD ($)
Debt Disclosure [Abstract]
2020	$ 2,000
2021	2,000
2022	833
Total future maturities of debt	$ 4,833

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	Dec. 31, 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

Convertible Preferred Stock T_2

Convertible Preferred Stock Tranche Liability - Additional Information (Details) $ / shares in Units, $ in Millions	Feb. 01, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2019shares	Dec. 31, 2018$ / sharesshares	Feb. 28, 2018$ / sharesshares	Dec. 31, 2016USD ($)Tranche$ / sharesshares
Convertible Preferred Stock Tranche Liability [Line Items]
Number of tranches | Tranche						2
Convertible preferred stock, issued			0	3,046,355
Series A Convertible Preferred Stock
Convertible Preferred Stock Tranche Liability [Line Items]
Convertible preferred stock, issued					1,506,307	1,506,307
Shares issued price per share | $ / shares				$ 3.9833	$ 3.9833	$ 3.9833
First Tranche | Series A Convertible Preferred Stock
Convertible Preferred Stock Tranche Liability [Line Items]
Convertible preferred stock, issued						1,506,307
Shares issued price per share | $ / shares						$ 3.9833
Second Tranche | Series A Convertible Preferred Stock
Convertible Preferred Stock Tranche Liability [Line Items]
Convertible preferred stock, issued	1,506,307
Shares issued price per share | $ / shares	$ 3.9833
Convertible Preferred Stock Tranche Liability | Second Tranche
Convertible Preferred Stock Tranche Liability [Line Items]
Fair value of tranche liability | $	$ 0					$ 0.3
Convertible Preferred Stock Tranche Liability | Second Tranche | Other Income (Expense), Net
Convertible Preferred Stock Tranche Liability [Line Items]
Gain on revaluation of tranche liability | $	$ 0.3
Convertible Preferred Stock Tranche Liability | Second Tranche | Other Income (Expense), Net | Maximum
Convertible Preferred Stock Tranche Liability [Line Items]
Gain on revaluation of tranche liability | $		$ 0.1

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	Jul. 31, 2019	Dec. 08, 2018	Jan. 09, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee Lease Description [Line Items]
Operating lease, expense				$ 0.2	$ 0.1	$ 0.1
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, term of contract						1 year
Operating lease commencement date						Jan. 1, 2017
Operating lease expiration date			Apr. 30, 2021			Dec. 31, 2017
Operating lease, rent payment						$ 0.1
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, term of contract	3 years
Operating lease commencement date		Jan. 2, 2019
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 termination date				Sep. 30, 2019

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) $ in Thousands	Dec. 31, 2019USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2020	$ 299
2021	195
2022	83
Total minimum lease payments	$ 577

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - USD ($)	1 Months Ended				12 Months Ended
	Sep. 30, 2019	Apr. 30, 2019	Feb. 28, 2018	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 17, 2019	Dec. 31, 2017
Class Of Stock [Line Items]
Preferred stock, shares authorized					10,000,000	3,191,489
Preferred stock, par value					$ 0.0001	$ 0.0001
Preferred stock, shares issued					0	3,046,355
Proceeds from issuance of convertible preferred stock, net of issuance costs					$ 61,490,000	$ 5,986,000
Minimum proceeds upon IPO, per preferred stock contract					$ 25,000,000
Share price upon qualified IPO description.					per share price is at least three times the original issuance price
Common stock, dividends per share, declared					$ 0.32
Common Stock
Class Of Stock [Line Items]
Conversion of redeemable convertible preferred stock into common stock, Shares					9,936,341
IPO | Common Stock
Class Of Stock [Line Items]
Preferred stock, shares issued					0
Shares issued price per share							$ 15
Conversion of redeemable convertible preferred stock into common stock, Shares	9,936,341
Redeemable convertible preferred stock outstanding, shares					0
Convertible Note | Maximum
Class Of Stock [Line Items]
Accrued interest expenses			$ 100,000					$ 100,000
Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized					10,000,000
Preferred stock, par value					$ 0.0001
Preferred stock, liquidation preference per share					$ 3.9833
Preferred stock, conversion basis					one-for-one basis
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized						3,191,489
Preferred stock, shares issued			1,506,307	1,506,307
Shares issued price per share			$ 3.9833	$ 3.9833		$ 3.9833
Proceeds from issuance of convertible preferred stock, net of issuance costs			$ 6,000,000	$ 5,800,000
Stock issuance cost				$ 200,000
Series A Convertible Preferred Stock | Maximum
Class Of Stock [Line Items]
Stock issuance cost			$ 100,000
Series A Convertible Preferred Stock | Convertible Note
Class Of Stock [Line Items]
Convertible preferred stock shares issued upon exchange of convertible note			33,741
Convertible note exchanged to shares price per share			$ 3.187
Percentage discount to purchase price per share			20.00%
Shares issued price per share			$ 3.187
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Proceeds from issuance of convertible preferred stock, net of issuance costs		$ 61,700,000
Preferred stock, shares issued		6,889,986
Shares issued price per share		$ 8.95444

Convertible Preferred Stock - S

Convertible Preferred Stock - Summary of Issued and Outstanding Redeemable Convertible Preferred Stock and Principal Terms (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Feb. 28, 2018	Dec. 31, 2016
Class Of Stock [Line Items]
Redeemable Convertible Preferred Stock, Authorized	10,000,000	3,191,489
Redeemable Convertible Preferred Stock, Outstanding	0	3,046,355
Liquidation Value	$ 0	$ 12,134
Carrying Amount		$ 11,648
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Redeemable Convertible Preferred Stock, Authorized		3,191,489
Redeemable Convertible Preferred Stock, Outstanding		3,046,355
Liquidation Value		$ 12,134
Carrying Amount		$ 11,648
Shares issued price per share		$ 3.9833	$ 3.9833	$ 3.9833

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Common stock, shares authorized	300,000,000	5,319,148
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, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Conversion of Series A convertible preferred stock	0	3,046,355
Exercise of common stock warrants	5,116	10,232
Exercise of outstanding options	1,568,874	829,775
Total	3,352,034	4,001,267
2019 Incentive Award Plan
Class Of Stock [Line Items]
Shares of common stock available for grant	1,778,044
2016 Incentive Award Plan
Class Of Stock [Line Items]
Shares of common stock available for grant		114,905
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of Series A convertible preferred stock		3,046,355

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend rate		0.00%	0.00%	0.00%
Common stock, shares reserved for issuance		3,352,034	4,001,267
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding Options, Number of Shares, Options granted		1,023,012	402,121	427,654
Expected dividend rate		0.00%
Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding Options, Number of Shares, Options granted		5,106	0	2,127
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
Weighted average grant-date fair value of options granted		$ 3.44	$ 0.66	$ 0.56
Unrecognized stock-based compensation expense		$ 3,000,000
Unrecognized stock-based compensation expense, weighted-average recognition period		2 years 9 months 18 days
Fair value of options vested		$ 700,000	$ 200,000
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 [Member]
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 [Member] | 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
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of options vested				$ 100,000
2016 Incentive Award Plan | Maximum | 10% Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options term		5 years
2019 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of common stock shares available for Issuance	695,281
2019 Employee Share Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares reserved for issuance					160,000
2019 Employee Share Purchase Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares reserved for issuance	173,280

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Activity Under 2019 Plan and 2016 Plan (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding Options, Number of Shares, Beginning Balance	829,775
Outstanding Options, Number of Shares, Ending Balance	1,568,874	829,775
2019 and 2016 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Beginning Balance	114,905	106,388	408,510
Shares Available for Grant, Additional shares authorized	2,675,833	408,511	127,659
Shares Available for Grant, Options granted	(1,028,118)	(402,121)	(429,781)
Shares Available for Grant, Options cancelled	15,424	2,127
Shares Available for Grant, Ending Balance	1,778,044	114,905	106,388
Shares Available for Grant, Exercisable as of December 31, 2019	433,396
Shares Available for Grant, Vested and expected to vest, December 31, 2019	1,568,874
Outstanding Options, Number of Shares, Beginning Balance	829,775	429,781
Outstanding Options, Number of Shares, Options granted	1,028,118	402,121	429,781
Outstanding Options, Number of Shares, Options exercised	(273,595)
Outstanding Options, Number of Shares, Options cancelled	(15,424)	(2,127)
Outstanding Options, Number of Shares, Ending Balance	1,568,874	829,775	429,781
Outstanding Options, Weighted Average Exercise Price, Beginning Balance	$ 0.97	$ 0.89
Outstanding Options, Weighted Average Exercise Price, Options granted	4.96	1.04	$ 0.89
Outstanding Options, Weighted Average Exercise Price, Options exercised	1.13
Outstanding Options, Weighted Average Exercise Price, Options cancelled	1.04	0.90
Outstanding Options, Weighted Average Exercise Price, Ending Balance	$ 3.55	$ 0.97	$ 0.89
Weighted Average Remaining Contractual Term, Options granted	9 years 4 months 17 days	9 years 3 months 25 days	9 years 3 months 25 days
Weighted Average Remaining Contractual Term, Balance	8 years 10 months 6 days	8 years 9 months 25 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Information about Stock Options Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Number	1,568,874	829,775
Option Vested and Exercisable, Number	433,396	382,318
Option Vested and Exercisable, Aggregate Intrinsic Value	$ 7,769	$ 1,075
Option Vested and Exercisable, Weighted Average Exercise Price	$ 1.76	$ 0.97
Exercise Price One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Exercise Price	$ 0.90	$ 0.90
Options Outstanding, Number	261,684	427,654
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	7 years 4 months 2 days	8 years 3 months 25 days
Option Vested and Exercisable, Number	176,444	247,880
Option Vested and Exercisable, Aggregate Intrinsic Value	$ 3,314	$ 709
Option Vested and Exercisable, Weighted Average Exercise Price	$ 0.90	$ 0.90
Exercise Price Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Exercise Price	$ 1.04	$ 1.04
Options Outstanding, Number	402,920	402,121
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	8 years 6 months 18 days	9 years 4 months 9 days
Option Vested and Exercisable, Number	165,016	134,438
Option Vested and Exercisable, Aggregate Intrinsic Value	$ 3,076	$ 366
Option Vested and Exercisable, Weighted Average Exercise Price	$ 1.04	$ 1.04
Exercise Price Three
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Exercise Price	$ 4.56
Options Outstanding, Number	781,036
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	9 years 4 months 13 days
Option Vested and Exercisable, Number	90,874
Option Vested and Exercisable, Aggregate Intrinsic Value	$ 1,374
Option Vested and Exercisable, Weighted Average Exercise Price	$ 4.56
Exercise Price Four
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Exercise Price	$ 5.55
Options Outstanding, Number	51,278
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	9 years 7 months 6 days
Exercise Price Five
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Exercise Price	$ 13.93
Options Outstanding, Number	6,000
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	9 years 11 months 12 days
Exercise Price Six
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Exercise Price	$ 15
Options Outstanding, Number	65,956
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	9 years 8 months 8 days
Option Vested and Exercisable, Number	1,062
Option Vested and Exercisable, Aggregate Intrinsic Value	$ 5
Option Vested and Exercisable, Weighted Average Exercise Price	$ 15

Stock-based Compensation - Sc_2

Stock-based Compensation - Schedule of Fair Value Assumptions of Stock Options (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	63.60%	77.20%	65.20%
Expected volatility, Maximum	74.90%	78.60%	67.80%
Risk-free interest rate		2.90%
Risk-free interest rate, Minimum	1.40%		1.80%
Risk-free interest rate, Maximum	2.50%		2.30%
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years	5 years 6 months	5 years 6 months
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	6 years 3 months 18 days

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Activity Under Restricted Stock Awards (Details) - Restricted Stock Awards (“RSAs”) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares underlying outstanding, unvested, beginning balance	31,914	63,829	95,744
Number of shares, vested in period	(31,914)	(31,915)	(31,915)
Number of shares underlying outstanding, unvested, ending balance		31,914	63,829

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 747	$ 170	$ 66
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	334	69	13
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 413	$ 101	$ 53

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss attributable to common stockholders	$ (10,809)	$ (8,260)	$ (6,291)	$ (2,815)	$ (2,344)	$ (1,587)	$ (2,203)	$ (1,212)	$ (28,175)	$ (7,346)	$ (5,172)
Denominator:
Weighted-average shares outstanding									5,879,820	1,074,690	638,297
Less: weighted-average unvested restricted shares and shares subject to repurchase									(15,870)	(47,785)	(79,700)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted									5,863,950	1,026,905	558,597
Net loss per share attributable to common stockholders, basic and diluted	$ (0.62)	$ (2.26)	$ (5.48)	$ (2.51)	$ (2.17)	$ (1.48)	$ (2.07)	$ (1.36)	$ (4.80)	$ (7.15)	$ (9.26)

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	1,573,990	3,918,276	3,914,522
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding		3,046,355	1,506,307
Convertible Note
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding			33,603
Convertible Preferred Stock Tranche Liability
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding			1,506,307
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	1,568,874	829,775	429,781
Unvested Restricted Common Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding		31,914	63,829
Obligation to Issue Additional Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding			374,695
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	5,116	10,232

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax at federal statutory income tax rate	$ (5,917)	$ (1,542)	$ (1,758)
Change in valuation allowance	6,708	1,527	1,099
Permanent differences	124	84	105
Prior year true ups	6		(70)
Research and development credits	(873)	(69)
State income taxes	1	1
Federal tax rate change			625
Other	(48)
Tax at effective income tax rate	$ 1	$ 1	$ 1

Income Taxes - Components of Ne

Income Taxes - Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 8,250	$ 2,456	$ 995
Research and development credit carryforwards	1,118	188	54
Stock-based compensation	45	4
Accruals and other	236	134	61
Gross deferred tax assets	9,649	2,782	1,110
Less: Valuation allowance	(9,491)	(2,696)	(1,103)
Deferred tax assets, net of valuation allowance	158	86	7
Deferred tax liabilities:
Property and equipment	$ (158)	$ (86)	$ (7)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Percentage of cumulative ownership changes	50.00%
Unrecognized tax benefits	$ 238,000	$ 157,000	$ 23,000
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	39,100,000	$ 34,500,000	$ 4,700,000
Operating loss carryforwards begin to expire			2037
Operating loss carryforwards offset of taxable income percentage			100.00%
Operating loss carryforwards limitation rate on taxable income		80.00%
Tax credit carryforwards	$ 1,100,000
Tax credit carryforward, expiration year	2037
Federal | Research and Development
Income Taxes [Line Items]
Tax credit carryforwards	$ 700,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 400,000
Operating loss carryforwards begin to expire	2037
State | California | Research and Development
Income Taxes [Line Items]
Tax credit carryforwards	$ 300,000

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Beginning balance	$ 157	$ 23
Increase related to current year tax positions	196	134	$ 23
Decrease related to prior year tax positions	(115)
Ending balance	$ 238	$ 157	$ 23

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details)

Sep. 17, 2019$ / sharesshares

Sep. 12, 2019USD ($)Owed$ / sharesshares

Sep. 30, 2019shares

Apr. 30, 2019USD ($)$ / sharesshares

Feb. 28, 2018USD ($)$ / sharesshares

Dec. 31, 2016USD ($)$ / sharesshares

Jul. 31, 2016USD ($)$ / sharesshares

Dec. 31, 2019USD ($)$ / sharesshares

Dec. 31, 2018USD ($)$ / shares

Dec. 31, 2017USD ($)

Aug. 31, 2016USD ($)

Aug. 01, 2016USD ($)

Related Party Transaction [Line Items]

Common stock, par price | $ / shares

$ 0.0001

$ 0.0001

Issuance of common stock, net of issuance costs

$ 81,435,000

Conversion of convertible note and accrued interest into preferred stock

$ 134,000

Series B Convertible Preferred Stock

Related Party Transaction [Line Items]

Shares issued, price per share | $ / shares

$ 8.95444

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

Convertible Note

Related Party Transaction [Line Items]

Debt instrument, face amount

$ 100,000

Convertible Note | Series A Convertible Preferred Stock

Related Party Transaction [Line Items]

Debt instrument converted, shares issued | shares

33,741

Shares issued, price per share | $ / shares

$ 3.187

Convertible Note | Maximum

Related Party Transaction [Line Items]

Conversion of convertible note and accrued interest into preferred stock

$ 100,000

Common Stock

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs, Shares | shares

6,052,116

Common Stock | IPO

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs, Shares | shares

5,500,000

Common stock, par price | $ / shares

$ 0.0001

Shares issued, price per share | $ / shares

$ 15

Shares issued upon conversion | shares

9,936,341

Additional Paid-in Capital

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs

$ 81,435,000

SNBL License

Related Party Transaction [Line Items]

Sale of products

0

0

$ 0

SNBL License | Series A Convertible Preferred Stock

Related Party Transaction [Line Items]

Estimated fair value of additional common stock

$ 1,400,000

SNBL License | Common Stock

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs, Shares | shares

510,638

Common stock, par price | $ / shares

$ 0.0001

SNBL License | Additional Paid-in Capital

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs

$ 700,000

SNBL

Related Party Transaction [Line Items]

Estimated fair value of additional common stock

$ 100,000

500,000

400,000

Estimated common stock issued to settle obligation, Share | shares

300,000

Additional paid-in capital

$ 1,300,000

Loss on change in fair value of common stock

200,000

Obligation to issue additional common stock reclassified to additional paid-in capital

500,000

SNBL | IPO

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs, Shares | shares

233,333

SNBL | Other Income, Net

Related Party Transaction [Line Items]

Loss on change in fair value of common stock

100,000

SNBL | Research and Development

Related Party Transaction [Line Items]

Preclinical study services expenses

$ 200,000

SNBL | Series A Convertible Preferred Stock

Related Party Transaction [Line Items]

Percentage of fully diluted common stock owned

20.00%

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 | Maximum | Accrued Liabilities

Related Party Transaction [Line Items]

Due to related party

100,000

100,000

SNBL | Maximum | Research and Development

Related Party Transaction [Line Items]

Preclinical study services expenses

$ 100,000

$ 100,000

SNBL | Convertible Note

Related Party Transaction [Line Items]

Debt instrument, face amount

$ 100,000

SNBL | Convertible Note | Series A Convertible Preferred Stock

Related Party Transaction [Line Items]

Debt instrument converted, shares issued | shares

33,741

SNBL | Convertible Note | Maximum

Related Party Transaction [Line Items]

Conversion of convertible note and accrued interest into preferred stock

$ 100,000

SNBL | Common Stock

Related Party Transaction [Line Items]

Issuance of common stock, net of issuance costs, Shares | shares

476,897

Shares issued, price per share | $ / shares

$ 0.90

Gross proceeds from issuance of common stock

$ 0

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Loss from operations	$ (11,275)	$ (8,470)	$ (6,422)	$ (2,714)	$ (2,284)	$ (1,600)	$ (2,222)	$ (1,409)	$ (28,881)	$ (7,515)	$ (4,947)
Net loss	$ (10,809)	$ (8,260)	$ (6,291)	$ (2,815)	$ (2,344)	$ (1,587)	$ (2,203)	$ (1,212)	$ (28,175)	$ (7,346)	$ (5,172)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.62)	$ (2.26)	$ (5.48)	$ (2.51)	$ (2.17)	$ (1.48)	$ (2.07)	$ (1.36)	$ (4.80)	$ (7.15)	$ (9.26)