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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Mar. 13, 2020	Jun. 28, 2019
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
Trading Symbol	CRTX
Entity Registrant Name	Cortexyme, Inc.
Entity Central Index Key	0001662774
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		29,402,240
Entity Public Float			$ 669.0
Entity File Number	001-38890
Entity Tax Identification Number	90-1024039
Entity Address, Address Line One	269 East Grand Ave.
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	910-5717
Document Annual Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, par value $0.001 per share
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Documents Incorporated by Reference	Part III incorporates by reference certain information from the registrant’s definitive proxy statement (the “Proxy Statement”) relating to its 2020 Annual Meeting of Stockholders. The Proxy Statement will be filed with the United States Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 51,214	$ 24,872
Short term investments	48,650	46,844
Prepaid expenses and other current assets	6,192	868
Total current assets	106,056	72,584
Property and equipment, net	709	283
Operating lease right-of-use assets, net	625
Long term investments	16,763
Other assets	217	10
Total assets	124,370	72,877
Current liabilities:
Accounts Payable	3,075	495
Accrued expenses and other current liabilities	5,817	962
Total current liabilities	8,892	1,457
Total liabilities	8,892	1,457
Commitments and contingencies (See Note 7)
Stockholders’ equity (deficit):
Preferred Stock, $0.001 par value, 10,000,000 authorized, no shares issued and outstanding December 31, 2019 and no shares authorized, issued and outstanding at December 31, 2018
Common stock, $0.001 par value, 100,000,000 and 24,794,114 shares authorized, 26,869,413 and 3,412,366 issued and outstanding as of December 31, 2019 and 2018, respectively	27	3
Additional paid in capital	185,196	245
Accumulated other comprehensive income (loss)	60	(49)
Accumulated deficit	(69,805)	(32,825)
Total stockholders’ equity (deficit)	115,478	(32,626)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	$ 124,370	72,877
Series A Redeemable Convertible Preferred Stock
Current liabilities:
Redeemable convertible preferred stock		17,178
Series B Redeemable Convertible Preferred Stock
Current liabilities:
Redeemable convertible preferred stock		$ 86,868

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	24,794,114
Common stock, shares issued	26,869,413	3,412,366
Common stock, shares outstanding	26,869,413	3,412,366
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	0	9,008,931
Redeemable convertible preferred stock, shares issued	0	9,008,919
Redeemable convertible preferred stock, shares outstanding	0	9,008,919
Redeemable convertible preferred stock, liquidation preference	$ 0	$ 17,178
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	0	9,430,145
Redeemable convertible preferred stock, shares issued	0	9,152,108
Redeemable convertible preferred stock, shares outstanding	0	9,152,108
Redeemable convertible preferred stock, liquidation preference	$ 0	$ 87,972

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 30,214	$ 10,085
General and administrative	8,954	2,034
Total operating expenses	39,168	12,119
Loss from operations	(39,168)	(12,119)
Interest income, net	2,188	806
Interest expense		(957)
Change in fair value of derivative liability		(206)
Net loss	(36,980)	(12,476)
Other comprehensive income (loss):
Unrealized gain (loss) on available for sales securities	109	(49)
Total comprehensive loss	$ (36,871)	$ (12,525)
Net loss per share - basic and diluted	$ (1.94)	$ (3.71)
Weighted average shares of common stock outstanding - basic and diluted	19,031,940	3,362,192

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid in Capital	Other Comprehensive Income / (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ (20,280)			$ 3	$ 66		$ (20,349)
Beginning balance, shares at Dec. 31, 2017		9,008,919
Beginning balance at Dec. 31, 2017		$ 17,178
Beginning balance, shares at Dec. 31, 2017				3,361,016
Issuance of Series B redeemable convertible preferred stock, net of issuance costs of $157			$ 75,688
Issuance of Series B redeemable convertible preferred stock, net of issuance costs, shares			7,890,466
Issuance of Series B redeemable convertible preferred stock in connection with the conversion of convertible promissory notes and accrued interest			$ 11,027
Issuance of Series B redeemable convertible preferred stock in connection with the conversion of convertible promissory notes and accrued interest, shares			1,147,205
Issuance of Series B redeemable convertible preferred stock in connection with the facility lease agreement, shares			114,437
Vesting of Series B redeemable convertible preferred stock in lieu of rent			$ 153
Exercise of stock options	24				24
Exercise of stock options, shares				51,350
Stock based compensation	155				155
Other Comprehensive Income (Loss)	(49)					$ (49)
Net loss	(12,476)						(12,476)
Beginning balance at Dec. 31, 2018	(32,626)			$ 3	245	(49)	(32,825)
Ending balance, shares at Dec. 31, 2018		9,008,919	9,152,108
Ending balance at Dec. 31, 2018		$ 17,178	$ 86,868
Ending balance, shares at Dec. 31, 2018				3,412,366
Conversion of redeemable convertiblepreferred stock to common stock	104,994			$ 18	104,976
Conversion of redeemable convertible preferred stock to common stock, shares		(9,008,919)	(9,152,108)
Conversion of redeemable convertible preferred stock to common stock		$ (17,178)	$ (87,816)
Conversion of redeemable convertible preferred stock to common stock, shares				18,161,027
Vesting of Series B redeemable convertible preferred stock in lieu of rent			$ 948
Initial public offering of common stock, netof issuance costs of $8,427	77,827			$ 5	77,822
Initial public offering of common stock, net of issuance costs, shares				5,073,800
Exercise of stock options	97			$ 1	96
Exercise of stock options, shares				194,279
Stock based compensation	2,056				2,056
Exercise of stock warrant	1				1
Exercise of stock warrant, shares				27,941
Other Comprehensive Income (Loss)	109					109
Net loss	(36,980)						(36,980)
Beginning balance at Dec. 31, 2019	$ 115,478			$ 27	$ 185,196	$ 60	$ (69,805)
Ending balance, shares at Dec. 31, 2019		0	0
Ending balance, shares at Dec. 31, 2019				26,869,413

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Series B Redeemable Convertible Preferred Stock
Stock issuance costs		$ 157
Common Stock
Stock issuance costs	$ 8,427

Statements of Cash Flows - USD ($)	12 Months Ended
Statements of Cash Flows - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net Loss	$ (36,980,000)	$ (12,476,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash interest expense related to convertible promissory notes		263,000
Non-cash rent expense	367,000	153,000
Stock based compensation	2,056,000	155,000
Depreciation and amortization	188,000	51,000
Accretion of discount on convertible promissory notes payable		694,000
Amortization of discount on available for sale investments	(812,000)	(351,000)
Change in fair value of derivative liability		206,000
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(5,324,000)	(690,000)
Other assets	(207,000)	50,000
Accounts payable	2,580,000	(23,000)
Accrued expenses and other current liabilities	4,855,000	273,000
Net cash used in operating activities	(33,277,000)	(11,695,000)
Cash flow from investing activities:
Purchase of investments	(135,415,000)	(55,242,000)
Proceeds from maturities of investments	117,723,000	8,700,000
Purchase of property and equipment	(55,000)	(212,000)
Net cash used in investing activities	(17,747,000)	(46,754,000)
Cash flows from financing activities:
Payments of finance leases	(559,000)
Proceeds from issuance of convertible promissory note payable		250,000
Proceeds from issuance of commons stock upon exercise of stock options	97,000	24,000
Proceeds from Series B redeemable convertible preferred stock, net of issuance costs		75,688,000
Proceeds from stock warrant exercise	1,000
Deferred initial public offering costs		(34,000)
Proceeds from initial public offering, net of stock offering costs	77,827,000
Net cash provided by financing activities	77,366,000	75,928,000
Net increase in cash and cash equivalents	26,342,000	17,479,000
Cash and cash equivalents at beginning of period	24,872,000	7,393,000
Cash and cash equivalents cash at end of period	51,214,000	24,872,000
Supplemental disclosures of non-cash information:
Right-of-use assets obtained in exchange for new operating lease liabilities	878,000
Series A Redeemable Convertible Preferred Stock
Supplemental disclosures of non-cash information:
Conversion of redeemable convertible preferred stock to common stock on initial public offering	17,178,000
Series B Redeemable Convertible Preferred Stock
Supplemental disclosures of non-cash information:
Conversion of redeemable convertible preferred stock to common stock on initial public offering	87,816,000
Acceleration of vesting of stock on initial public offering	$ 856,000
Issuance of stock in connection with conversion of convertible promissory notes and accrued interest		11,027,000
Issuance of stock for facility lease		$ 1,100,000

Organization

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization

Note 1. Organization

Description of Business

Cortexyme, Inc. (the “Company”) was incorporated in the State of Delaware in June 2012 and is headquartered in South San Francisco, California. The Company is a clinical stage biopharmaceutical company focused on developing therapeutics based on data supporting a new theory of the cause of Alzheimer’s disease and other degenerative disorders. Cortexyme is targeting a specific, infectious pathogen tied to neurodegeneration and chronic inflammation in humans and animal models.

Reverse Stock Split

On April 25, 2019, the Company’s Board of Directors approved a one-for-0.367647 reverse split of the Company’s issued and outstanding common stock, redeemable convertible preferred stock, and stock options. The par value of the common stock was not adjusted as a result of the reverse stock split. All share and per share amounts in the accompanying financial statements and notes to the financial statements have been retroactively adjusted for all periods presented to reflect the reverse stock split.

Initial Public Offering

On May 8, 2019, the Company’s registration statement on Form S-1 (File No. 333-230853) for its initial public offering of common stock (“IPO”) was declared effective by the Securities and Exchange Commission (“SEC”). On May 13, 2019, the Company closed its IPO with the sale of 5,073,800 shares of common stock, which included 661,800 shares of common stock issued upon the exercise in full of the underwriters’ option to purchase additional shares, at a public offering price of $17.00 per share, resulting in net proceeds of $77.8 million, after deducting underwriting discounts and commissions and estimated offering expenses paid by the Company.

In addition, in connection with the closing of the IPO, all of the Company’s outstanding shares of redeemable convertible preferred stock were automatically converted into 18,161,027 shares of common stock, and there are no shares of redeemable convertible preferred stock outstanding as of December 31, 2019.

Liquidity and Capital Resources

The Company has incurred losses and negative cash flows from operations since inception and expects to continue to generate operating losses for the foreseeable future. As of December 31, 2019, the Company had an accumulated deficit of $69.8 million. Since inception through December 31, 2019, the Company has funded operations primarily with the net proceeds from the issuance of convertible promissory notes, from the issuance of redeemable convertible preferred stock and from the net proceeds from the IPO. As of December 31, 2019, the Company had cash, cash equivalents, and short-term investments of $99.9 million, which it believes will be sufficient to fund its planned operations for a period of at least 12 months from the date of the issuance of the accompanying financial statements.

Management expects to incur additional losses in the future to fund its operations and conduct product research and development and may need to raise additional capital to fully implement its business plan. The Company may raise additional capital through the issuance of equity securities, debt financings or other sources in order to further implement its business plan. However, if such financing is not available when needed and at adequate levels, the Company will need to reevaluate its operating plan and may be required to delay the development of its product candidate.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements and the notes thereto have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) pursuant to the instructions of the SEC on Form 10-K through the rules and interpretive releases of the SEC under federal securities law.

Use of Estimates

The preparation of the Company’s financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and expenses, as well as related disclosure of contingent assets and liabilities. The most significant estimates used in the Company’s financial statements relate to the determination of the fair value of common stock prior to the initial public offering, stock-based awards and other issuances, valuation of derivative instruments, accruals for research and development costs, useful lives of long-lived assets, stock-based compensation and related assumptions, the incremental borrowing rate for leases and income tax uncertainties, including a valuation allowance for deferred tax assets; and contingencies. The Company bases its estimates on historical experience and on various other market specific and other relevant assumptions that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from the Company’s estimates.

Risk and Uncertainties

The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s potential drug candidates, uncertainty of market acceptance of the Company’s drug candidates, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. The Company’s drug candidate will require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any drug candidate will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any drug candidate, it could have a materially adverse impact on the Company.

Segments

The Company operates and manages its business as one reportable and operating segment, which is the business of developing and commercializing therapeutics. The Company’s chief executive officer, who is the chief operating decision makers, reviews financial information on an aggregate basis for purposes of allocating and evaluating financial performance. All long-lived assets are maintained in the United States of America.

Cash, Cash Equivalents and Investments

The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash equivalents include marketable securities. Management determines the appropriate classification of its investments in debt securities at the time of purchase and at the end of each reporting period. Investments with original maturities beyond three months at the date of purchase and which mature at, or less than twelve months from the balance sheet date are classified as short-term investments. Investments with a maturity beyond twelve months from the balance sheet date are classified as long-term investments. Collectively, cash equivalents, short-term investments and long-term investments are considered available-for-sale and are recorded at fair value. Unrealized gains and losses are recorded as a component of other comprehensive loss in the statement of operations and included as a separate component of redeemable convertible preferred stock and stockholders’ equity (deficit). Realized gains and losses are included in interest and other income, net in the statements of operations and comprehensive loss.

Premiums (discounts) are amortized (accreted) over the life of the related investment as an adjustment to yield using the straight-line interest method. Dividend and interest income are recognized when earned. These amounts are recorded in “Interest income, net” in the Statement of Operations.

Property and Equipment, Net

Property and equipment are stated at cost and reduced by accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful lives of the assets, generally five years. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. 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 operations in the period realized.

Concentration of Credit Risk

Cash equivalents short-term and long-term investments are financial instruments that potentially subject the Company to concentrations of credit risk. The Company invests in money market funds, repurchase agreements, treasury bills and notes, government bonds, commercial paper and corporate notes. The Company limits its credit risk associated with cash equivalents, short-term and long-term investments by placing them with banks and institutions it believes are highly credit worthy and in highly rated investments.

Impairment of Long-Lived Assets

The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment charge would be recorded when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. The Company did not recognize any impairment charges for the years ended December 31, 2019 and 2018.

Deferred Offering Costs

Deferred offering costs, consisting of direct legal, accounting, filing and other fees directly related to the Company’s initial public offering of its common stock (IPO), are capitalized. The deferred offering costs was reclassified to additional paid-in capital upon the closing of the IPO. The Company deferred $34,000 as of December 31, 2018, which is included in prepaid expense and other assets in the accompanying balance sheets.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development expenses consist primarily of personnel costs for the Company’s research and product development employees. Also included are non-personnel costs such as professional fees payable to third parties for preclinical and clinical studies and research services, laboratory supplies and equipment maintenance, product licenses, and other consulting costs. The Company estimates preclinical and clinical study and research expenses based on the services performed, pursuant to contracts with contract research organizations (“CROs”) that conduct and manage preclinical and clinical studies and research services on its behalf. Expenses related to clinical studies are based on estimates of the services received and efforts expended pursuant to contracts with many research institutions, clinical research organizations and other service providers that conduct and manage clinical studies on our behalf. The financial terms of these agreements are subject to negotiation and vary from contract to contract and may result in uneven payment flows. Generally, these agreements set forth the scope of work to be performed at a fixed fee or unit price. Payments under the contracts are mainly driven by time and materials incurred by these service providers. Payments made to third parties under these arrangements in advance of the performance of the related services by the third parties are recorded as prepaid expenses until the services are rendered. Expenses related to clinical studies are generally recorded based on the timing of when services that have been performed on the Company’s behalf by the service providers and in accordance with the contracts. The determination of timing involves reviewing open contracts and purchase orders, communicating with applicable personnel to identify the timing of when services that have been performed on the Company’s behalf and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of actual cost. The majority of service providers’ invoice at least monthly in arrears for services performed. The Company periodically confirms the accuracy of estimates with the service providers and makes adjustments if necessary. Examples of estimated clinical expenses include:

•

fees paid to Contract Research Organizations, or CROs, in connection with clinical studies;

•

fees paid to investigative sites in connection with clinical studies;

•

fees paid to contract manufacturers in connection with the production of clinical study materials; and

•

fees paid to vendors in connection with preclinical development activities.

If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the prepaid or accrual accordingly. 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 expensed as incurred.

Patent Costs

The Company has no historical data to support a probable future economic benefit for the arising patent applications, filing and prosecution costs. Therefore, patent costs are expensed as incurred.

Stock-Based Compensation

The Company accounts for stock-based compensation arrangements with employees in accordance with Accounting Standards Codification (“ASC”) 718, Compensation—Stock Compensation. Stock-based awards granted include stock options with time-based vesting. ASC 718 requires the recognition of compensation expense, using a fair value-based method, for costs related to all stock-based payments. The Company’s determination of the fair value of stock options with time-based vesting on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by its common stock price as well as other variables including: but not limited to, expected term that options will remain outstanding, expected common stock price volatility over the term of the option awards, risk-free interest rates and expected dividends. The fair value of a stock-based award is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period) on a straight-line basis. Stock-based compensation expense is recognized based on the fair value determined on the date of grant and is reduced for forfeitures as they occur.

Redeemable Convertible Preferred Stock

The Company recorded all shares of convertible preferred stock at their respective fair values less issuance costs on the dates of issuance. The convertible preferred stock was recorded outside of stockholders’ equity (deficit) because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of all the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders. Additionally, on or after May 23, 2025, 60% of the holders may have demanded redemption of the stock. In the event of a change of control of the Company, proceeds received from the sale of such shares would have been distributed in accordance with the liquidation preferences set forth in the Company’s Amended and Restated Certificate of Incorporation unless the holders of convertible preferred stock had converted their shares of convertible preferred stock into shares of common stock. The Company determined not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because of the uncertainty of whether or when such an event would occur. In connection with the closing of the IPO, all of the Company’s outstanding shares of redeemable convertible preferred stock were automatically converted into 18,161,027 shares of common stock, and there are no shares of redeemable convertible preferred stock outstanding as of December 31, 2019.

Fair Value of Warrants

Warrants were recorded either as equity instruments or derivative liabilities at their estimated fair value at the date of issuance. In the case of warrants recorded as liabilities, subsequent changes in estimated fair value were recorded in the Company’s statement of operations in each subsequent period. The warrants were measured at estimated fair value using the Black Scholes valuation model, which was based, in part, upon inputs for which there was little or no observable market data, requiring the Company to develop its own assumptions. Inherent in this model were assumptions related to expected stock price volatility, expected life, risk-free interest rate and dividend yield. The Company estimated the volatility of its common stock at the date of issuance, and at each subsequent reporting period, based on historical volatility that matched the expected remaining life of the warrants. The risk-free interest rate was based on the U.S. Treasury zero-coupon yield curve on the measurement date for a maturity similar to the expected remaining life of the warrants. The expected life of the warrants was assumed to be equivalent to their remaining contractual term. The dividend rate was based on the Company’s historical rate, which was at zero. The assumptions used in calculating the estimated fair value of the warrants represented the Company’s best estimates. However, these estimates involved inherent uncertainties and the application of management judgment. As a result, if factors changed and different assumptions were used, the warrant liability and the change in estimated fair value could be materially different. As of December 31, 2018, warrants to purchase 27,941 shares of common stock were outstanding and are recorded as equity instruments. In connection with the closing of the IPO, all the Company’s outstanding warrants were exercised. No warrants are outstanding as of December 31, 2019

Derivative Liability

ASC 815-15, Derivatives and Hedging: Embedded Derivatives, generally provides three criteria that, if met, require companies to bifurcate conversion options from their host instruments and account for them as free standing derivative financial instruments. These three criteria include circumstances in which (a) the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract, (b) the hybrid instrument that embodies both the embedded derivative instrument and the host contract is not re-measured at fair value under otherwise applicable generally accepted accounting principles with changes in fair value reported in earnings as they occur and (c) a separate instrument with the same terms as the embedded derivative instrument would be considered a derivative instrument subject to the requirement of ASC 815.

The Company issued certain convertible promissory notes in 2018 to current and new investors which contained an embedded derivative instrument, a share redemption feature that settles upon the next qualified preferred stock financing. This embedded put option was not considered clearly and closely related to the debt host and resulted in an embedded derivative that must be bifurcated and accounted for separately from the debt host. Accordingly, the Company recorded the bifurcated redemption feature as a derivative liability.

Derivative financial liabilities were initially recorded at fair value, with gains and losses arising for changes in fair value recognized in the statement of operations at each period end while such instruments were outstanding. In May 2018, the convertible promissory notes including the redemption premium were converted into Series B redeemable convertible preferred stock. See Note 10 for further discussion of the convertible promissory notes and the bifurcated derivative liability.

Income Taxes

The Company accounts for income taxes under the asset and liability method. Current income tax expense or benefit represents the amount of income taxes expected to be payable or refundable for the current year. Deferred income tax assets and liabilities are determined based on differences between the financial statement reporting and tax bases of assets and liabilities and net operating loss and credit carryforwards and are measured using the enacted tax rates and laws that will be in effect when such items are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized.

The Company accounts for uncertain tax positions in accordance with ASC 740-10, Accounting for Uncertainty in Income Taxes. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.

The Company includes any penalties and interest expense related to income taxes as a component of other expense and interest expense, net, as necessary.

Comprehensive Income (Loss)

The Company is required to report all components of comprehensive income (loss), including net loss, in the financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as a change in equity of a business enterprise during a period, resulting from transactions and other events and circumstances from non-owner sources. The Company had unrealized gain from its available-for-sale securities during the year ended December 31, 2019 and an unrealized loss from its available-for sale securities during the year ended December 31, 2018, which are considered other comprehensive income (loss).

Net Loss per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents of potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, redeemable convertible preferred stock, warrants and common stock options are considered to be potentially dilutive securities. Because the Company reported a net loss for the years ended December 31, 2019 and 2018, and the inclusion of the potentially dilutive securities would be antidilutive, diluted net loss per share is the same as basic net loss per share for both periods.

Recent Accounting Pronouncements

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. The new guidance changes disclosure requirements related to fair value measurements as part of the disclosure framework project. The disclosure framework project aims to improve the effectiveness of disclosures in the notes to the financial statements by focusing on requirements that clearly communicate the most important information to users of the financial statements. This guidance is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company does not believe this pronouncement will have a material impact on its financial statements or disclosures.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 requires companies to measure credit losses utilizing a methodology that reflects expected credit losses and requires a consideration of a broader range of reasonable and supportable information to inform credit loss estimates. For Smaller Reporting Companies as defined by the SEC, ASU 2016-13 is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is evaluating the impact of the guidance on its financial statements.

In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40)”: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”), which clarifies the accounting for implementation costs in cloud computing arrangements. ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company will adopt the standard prospectively on January 1, 2020. The Company does not expect the adoption of ASU 2018-15 to result in a material change to its financial statements.

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This ASU requires that substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. The ASU is effective for interim and annual periods beginning after December 15, 2018. Additionally, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, which offers an additional transition method whereby entities may apply the new leases standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings rather than application of the new leases standard at the beginning of the earliest period presented in the financial statements. The Company elected this transition method and adopted ASC 842 on January 1, 2019 and as a result, recorded a right-of-use asset of $0.9 million, a short-term lease liability of $0.3 million, and a long-term lease liability of $0.6 million and no cumulative effect adjustment was made to the retained earnings as of the adoption date. The Company has elected not to recognize a right-of-use asset and lease liability for short-term leases. A short-term lease is a lease with an expected lease term of 12 months or less and which does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise. The Company also elected the package of practical expedients under the transition guidance that will retain the historical lease classification and initial direct costs for any leases that exist prior to adoption of the new guidance and the practical expedient to not separate lease and nonlease components. See Note 6 for further disclosure.

In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815) I. Accounting for Certain Financial Instruments with Down Round Features II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). Part I applies to entities that issue financial instruments such as warrants, convertible debt or redeemable convertible preferred stock that contain down-round features. Part II replaces the indefinite deferral for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities contained within ASC Topic 480 with a scope exception and does not impact the accounting for these mandatorily redeemable instruments. For public entities, ASU 2017-11 is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. The adoption of ASU 2017-11 did not have any impact on the Company’s financial statements since the Company did not have any instruments subject to the scope of ASU 2017-11.

On December 18, 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. Most amendments within the standard are required to be applied on a prospective basis, while certain amendments must be applied on a retrospective or modified retrospective basis. The pronouncement is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company early adopted the new accounting standard effective January 1, 2019. The adoption did not have a material impact on the Company’s financial statements.

All other newly issued accounting pronouncements not yet effective have been deemed either immaterial or not applicable.

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 3. Fair Value Measurements

The fair value of our financial instruments reflects the amounts that we estimate we would receive in connection with the sale of an asset or pay in connection with the transfer of a liability in an orderly transaction between market participants at the measurement date (exit price). We disclose and recognize the fair value of our assets and liabilities using a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to valuations based upon unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to valuations based upon unobservable inputs that are significant to the valuation (Level 3 measurements). The guidance establishes three levels of the fair value hierarchy as follows:

Level 1 - Inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access at the measurement date;

Level 2 - Inputs other than quoted prices that are observable for the assets or liability either directly or indirectly, including inputs in markets that are not considered to be active;

Level 3 - Inputs that are unobservable. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

The carrying amounts of the Company’s financial instruments, which include cash, accounts payable and accrued liabilities and other current liabilities approximate their fair values due to their short maturities.

Our assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. During the years presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value using Level 3 inputs. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the years ended December 31, 2019 and 2018.

Financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements by major security type as of December 31, 2019 and December 31, 2018 are presented in the following tables (in thousands):

	Fair Value Measurements at December 31, 2019
	Total		Level 1		Level 2		Level 3
Money market funds	$	30,054	$	30,054	$	—	$	—
Certificates of Deposit		20,046		—		20,046		—
Repurchase Agreements		15,000		—		15,000		—
Corporate notes		38,783		—		38,783		—
Government notes		7,574		—		7,574		—
Commercial Paper		1,096		—		1,096		—
Total	$	112,553	$	30,054	$	82,499	$	—

	Fair Value Measurements at December 31, 2018
	Total		Level 1		Level 2		Level 3
Money market funds	$	11,815	$	11,815	$	—	$	—
Commercial Paper		14,360		—		14,360		—
Corporate notes		16,111		—		16,111		—
Government notes		8,979		—		8,979		—
Asset backed securities		9,192		—		9,192		—
Total	$	60,457	$	11,815	$	48,642	$	—

The change in the derivative liability is as follows (in thousands):

	December 31,
	2019		2018
Fair Value at beginning of period	$	—	$	1,886
Bifurcated derivative liability		—		113
Change in fair value		—		206
Conversion of promissory notes to Series B redeemable convertible preferred stock		—		(2,205	)
Fair value at end of period	$	—	$	—

See Note 10 for further discussion of the derivative liability.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Cash, Cash Equivalents and Investments

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Cash, Cash Equivalents and Investments

Note 4: Cash, cash equivalents and investments

The following tables categorize the fair values of cash, cash equivalents, and short-term investments measured at fair value on a recurring basis on our balance sheet (in thousands):

		December 31,
	2019			2018
Cash and cash equivalents:
Cash	$		4,074	$	11,259
Money market funds			30,054		11,815
Commercial paper			—		1,798
Certificate of deposits			985		—
Repurchase agreements			15,000		—
Corporate notes			1,101		—
Total cash and cash equivalents	$		51,214	$	24,872

Short-term investments:
Commercial paper			1,096		12,562
Corporate notes			24,552		16,111
Government notes			7,574		8,979
Certificate of deposits			15,428		9,192
Total short-term investments	$		48,650	$	46,844

Long-term investments:
Corporate notes			13,130		—
Certificate of deposits			3,633
Total long-term investments	$		16,763	$	—

The investments are classified as available-for-sale securities. At December 31, 2019 and 2018 the balance in the Company’s accumulated other comprehensive income (loss) was comprised solely of activity related to the Company’s available-for-sale securities. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities for the year ended December 31, 2019 or 2018 and as a result, the Company did not reclassify any amounts out of accumulated other comprehensive income for the year. The Company has a limited number of available-for-sale securities in insignificant loss positions as of December 31, 2019 and 2018, which the Company does not intend to sell and has concluded it will not be required to sell before recovery of the amortized cost for the investment at maturity.

The following table summarizes the available-for-sale securities (in thousands):

	Fair Value Measurements at December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	30,054	$	—	$	—		$	30,054
Certificates of Deposit		19,992		54		—			20,046
Repurchase Agreements		15,000		—		—			15,000
Corporate notes		38,788		—		(5	)		38,783
Government notes		7,563		11					7,574
Commercial Paper		1,096		—		—			1,096
Total cash equivalents and investments	$	112,493	$	65	$	(5	)	$	112,553

Classified as:
Cash equivalents (maturities within 90 days)								$	47,140
Short-term investments (maturities within one year)									48,650
Long-term investments (maturities beyond 1 year)									16,763
Total cash equivalents and investments								$	112,553

	Fair Value Measurements at December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	11,815	$	—	$	—		$	11,815
Commercial paper		14,362		—		(2	)		14,360
Corporate notes		16,129		—		(18	)		16,111
U.S. government notes		8,980		—		(1	)		8,979
Asset backed securities		9,220		—		(28	)		9,192
Total cash equivalents and investments	$	60,506	$	—	$	(49	)	$	60,457

Classified as:
Cash equivalents (maturities within 90 days)								$	13,613
Short-term investments (maturities within one year)									46,844
Total cash equivalents and investments								$	60,457

Balance Sheet Components

12 Months Ended

Dec. 31, 2019

Balance Sheet Components [Abstract]

Balance Sheet Components

Note 5: Balance Sheet Components

Prepaid expenses and other current assets

Prepaid expenses and other current assets consisted of the following (in thousands):

	December 31,
	2019		2018
Prepaid expenses	$	987	$	47
Prepaid research and development expenses		4,517		753
Other current assets		688		68
	$	6,192	$	868

Property and equipment, net

Property and equipment, net consisted of the following (in thousands):

	December 31,
	2019			2018
Computer Equipment	$	28		$	—
Lab Equipment		405			378
Finance lease right of use assets		559			—
Less: accumulated amortization and depreciation		(283	)		(95	)
Property and equipment, net	$	709		$	283

Depreciation expense for property and equipment was $188,000 and $51,000 for the years ended December 31, 2019 and 2018, respectively.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2019		2018
Personnel expense	$	1,261	$	483
Research and development expenses		4,410		380
Professional fees		96		75
Other		50		24
Total accrued liabilities	$	5,817	$	962

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

Note 6. Leases

As described in “Note 2 Summary of Significant Accounting Policies,” the Company adopted Topic 842 as of January 1, 2019. Prior period amounts have not been adjusted and continue to be reported in accordance with historic accounting under Topic 840.

Real Estate Operating Leases

In June 2018, the Company entered into a three-year lease agreement with no renewal options with a related party, one of the investors in the Series B redeemable convertible preferred stock. The lease began on July 16, 2018 and provides 3,185 square feet of office and laboratory space in South San Francisco, California. The Company issued 114,437 shares of its Series B redeemable convertible preferred stock with a fair value of $1.1 million in exchange for the leased facility. No other payments are due under the lease. The common area maintenance and other operating costs are included in the base rent. 100% of the issued shares were initially subject to a repurchase option. Pursuant to the terms of the lease, each month beginning on the one-month anniversary of the commencement date of the lease, 1/36^th of the total shares are released from the repurchase option until all shares are released over the lease period of three years. The scheduled release of shares ceased immediately upon the IPO which was a terminating event.

The Company completed its IPO on May 13, 2019 and as a result, pursuant to the terms of the lease agreement, all previously unvested shares were fully vested and as part of the IPO process, all outstanding shares of the Company’s redeemable convertible preferred stock including the Series B redeemable convertible preferred stock issued in connection with the lease agreement were converted into shares of the Company’s common stock on a 1-for-1 basis and the operating lease liability was extinguished as the entire lease became prepaid.

In May 2019 the Company entered into an amendment to the lease agreement to rent additional space in the same facility under the same terms as its existing facility lease except the terms of payment. Under the terms of the amendment, the Company paid a one-time fee of approximately $63,000 for the additional space and the lease agreement will terminate in July 2021. No other payments are due under the lease agreement and no renewal option is available. As the entire lease is prepaid, there is no associated lease liability.

The Company recognizes lease expense on a straight-line basis over the term of its operating lease. As of December 31, 2019, future rent expense of approximately $625,000 will be recognized over the remaining term of 19 months on a straight-line basis over the respective lease period.

Clinical Equipment Financing Lease

During the second quarter of 2019, the Company began using certain vendor supplied equipment in connection with its on-going clinical trial. The Company analyzed the agreements and determined that they contained embedded leases. Under the agreements, the Company has prepaid for the use of the equipment through the initial lease term of approximately three years. As a result, the Company has no lease liability associated with these right of use assets. The Company records the finance lease right of use assets in “Property and equipment, net” line on the Balance Sheet. The Company recognizes the amortization expense in research and development expenses in the statement of operations and recognizes expense on a straight-line basis starting when the equipment is placed into service until the end of the contract term. Equipment placed into service is amortized into expense over periods ranging from 28 to 34 months. Amortization expense of the financing lease right of use asset for the year ended December 31, 2019 was $107,000.

Operating and finance lease right of use asset amounts consist of the following as of December 31, 2019 (in thousands):

Operating lease right of use asset, net	$	625

Finance lease right of use asset		559
Finance lease accumulated amortization		(107	)
Total finance lease right of use asset, net	$	452

The Company determined its operating and finance lease liabilities for operating lease using a discount rate of 4.00% based on the rate that the Company would have to pay to borrow on a collateralized basis for a similar lease an amount equal to the lease payments in a similar economic environment. As of December 31, 2019, the weighted-average remaining lease term for the operating leases was 1.6 years. The weighted-average remaining lease term for the finance leases was 2.09 years.

Lease costs for the years ended December 31, 2019 was approximately:

Lease costs:
Finance lease amortization of right of use assets	$	107
Operating lease costs		374
Short-term lease costs		11
Total lease costs	$	492

For the year ended December 31, 2018, rent expense under operating leases computed under the previous accounting method, ASC 840, Leases, was approximately $387,000.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 7. Commitments and Contingencies

Legal Matters

The Company’s industry is characterized by frequent claims and litigation, including claims regarding intellectual property. As a result, the Company may be subject to various legal proceedings from time to time. The results of any future litigation cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors. Management is not aware of any pending or threatened litigation.

Indemnification

As permitted under Delaware law and in accordance with the Company’s bylaws, the Company is required to indemnify its officers and directors for certain events or occurrences while the officer or director is or was serving in such capacity. The Company is also party to indemnification agreements with its directors. The Company believes the fair value of the indemnification rights and agreements is minimal. Accordingly, the Company has not recorded any liabilities for these indemnification rights and agreements as of December 31, 2019.

Contingencies

From time to time, we may have certain contingent liabilities that arise in the ordinary course of our business activities. We accrue a liability for such matters when it is probable that future expenditures will be made, and such expenditures can be reasonably estimated.

Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)

Note 8. Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit)

Redeemable Convertible Preferred Stock

As of December 31, 2018, the outstanding redeemable convertible preferred stock was as follows (in thousands except for share and per share amounts):

Authorized

Shares Issued

and Outstanding

Issuance Price

per share

Liquidation

Preference

Carrying Value

Series A

9,008,931

9,008,919

1.9067

17,178

Series B

9,430,145

9,152,108

9.6122

87,972

86,868

On May 13, 2019 in connection with the closing of the IPO, these shares were automatically converted into 18,161,027 shares of common stock, and there are no shares of redeemable convertible preferred stock outstanding as of December 31, 2019.

Common Stock

As of December 31, 2019, the Company had reserved common stock for issuance as follows:

	December 31, 2019
Options issued and outstanding under the 2019 Stock Plan		2,393,934
Shares available for issuance under 2019 Stock Plan		2,439,779
Shares available for issuance under the Employee Stock Ownership Plan		268,295
Total		5,102,008

The Company is authorized to issue 100,000,000 shares of common stock with a par value of $0.001 per share. Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when and if declared by the board of directors, subject to the prior rights of holders of any preferred stock that may be outstanding at the time. The Company has never declared any dividends on common stock. As of December 31, 2019, and 2018, the Company had 26,869,413 and 3,412,366 shares of common stock issued and outstanding respectively.

Common Stock Warrant

In June 2014, in connection with a research grant and license agreement, the Company issued a warrant to purchase 27,941 shares of common stock at $0.03 per share. The grant date estimated fair value of such warrants was insignificant. The warrant was immediately exercisable and expires in June 2024. The warrant was fully exercised in May 2019.

Stock Option Plan

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Plan

Note 9. Stock Option Plan

On December 4, 2014, the Company’s stockholders approved the 2014 Stock Plan (“2014 Plan”), and most recently amended the 2014 Plan on April 25, 2019. The 2014 Plan was amended, restated and re-named the 2019 Equity Incentive Plan (the “2019 Plan”), which became effective as of May 7, 2019, the day prior to the effectiveness of the registration statement filed in connection with the IPO. The remaining shares available for issuance under the 2014 Plan were added to the shares reserved for issuance under the 2019 Plan.

The 2019 Plan provides for the grant of stock options (including incentive stock options and non-qualified stock options), stock appreciation rights, restricted stock, RSUs, performance units, and performance shares to the Company’s employees, directors, and consultants. The maximum aggregate number of shares that may be issued under the 2019 Plan is 5,131,549 shares of the Company’s common stock. In addition, the number of shares available for issuance under the 2019 Plan will be annually increased on the first day of each of its fiscal years beginning with fiscal 2020, by an amount equal to the least of (i) 2,146,354 shares of common stock; (ii) 4% of the outstanding shares of its common stock as of the last day of its immediately preceding fiscal year; and (iii) such other amount as the Company’s Board of Directors may determine.

The 2019 Plan may be amended, suspended or terminated by the Company’s Board of Directors at any time, provided such action does not impair the existing rights of any participant, subject to stockholder approval of any amendment to the 2019 Plan as required by applicable law or listing requirements. Unless sooner terminated by the Company’s Board of Directors, the 2019 Plan will automatically terminate on April 23, 2029.

As of December 31, 2019, the Company had 2,439,779 shares available for future issuance under the 2019 Plan.

In 2019 and 2018, the Company recognized $2,056,000 and $155,000 respectively, of stock-based compensation expense related to options granted to employees and non-employees. The compensation expense is allocated on a departmental basis, based on the classification of the option holder. No income tax benefits have been recognized in the statement of operations for stock-based compensation arrangements.

Future stock-based compensation for unvested employee and non-employee options granted and outstanding as of December 31, 2019 is $6.4 million to be recognized over a remaining weighted average requisite service period of 1.42 years.

Stock option activity under the 2019 Plan is as follows:

	Number of Options			Weighted Average Exercise Price			Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Balance at December 31, 2017		769,409		$	0.39		8.89				1,107,581
Options granted		1,316,342			2.08		—			—
Options exercised		(51,350	)		0.46		—			—
Options cancelled		(148,897	)		0.41		—			—
Balance at December 31, 2018		1,885,504			1.57		9.07				1,252,496
Options granted		932,639				15.87	—			—
Options exercised		(194,279	)			0.51	—			—
Options forfeited / expired		(229,930	)			21.09	—			—
Balance at December 31, 2019		2,393,934		$	5.35			8.62	$		121,592,682
Options vested and expected to vest to December 31, 2019		2,393,934		$	5.35			8.62	$		121,592,682
Options exercisable at December 31, 2019		751,334		$		2.59		7.96	$		40,235,852

Aggregate intrinsic value represents the difference between the Company’s estimated fair value of its common stock as of their respective balance sheet dates and the exercise price of outstanding options. The total intrinsic value of options exercised was $886,989 and $91,000 for the year ended December 31, 2019 and 2018, respectively. During the year ended December 31, 2019, the weighted-average grant-date fair value of the options vested was $2.35 per share. The weighted-average grant date fair value of options granted during the years ended December 31, 2019 and 2018 was $11.11 and $1.26 per share, respectively.

The following table summarizes employee and non-employee stock-based compensation expense for the years ended December 31, 2019 and 2018 and the allocation within the statements of operations and comprehensive loss (in thousands):

	2019		2018
General and administrative expense	$	1,378	$	78
Research and development expense		678		77
Total stock-based compensation		2,056		155

The Company estimates the fair value of stock-based compensation utilizing the Black-Scholes option pricing model, which is dependent upon several variables, such as expected term, volatility, risk-free interest rate, and expected dividends. Each of these inputs is subjective and generally requires significant judgment to determine. Stock-based compensation is measured at the grant date based on the fair value of the award and is recognized as expense, over the requisite service period, which is generally the vesting period of the respective award. The Company recognizes compensation on a straight-line basis over the requisite vesting period for each award. Forfeitures are recognized as they occur. The following weighted average assumptions were used to calculate the fair value of stock-based compensation as of December 31, 2019 and 2018:

	2019			2018
Expected volatility		80.19	%		69.6	%
Expected dividend yield		—	%		—	%
Expected term (in years)	6.25			6.25
Risk-free interest rate		1.90	%		2.91	%

Expected Term — The Company has opted to use the “simplified method” for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years).

Expected Volatility — Due to the Company’s limited operating history and a lack of company specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards.

Risk-Free Interest Rate — The risk-free rate assumption is based on the U.S. Treasury instruments with maturities similar to the expected term of the Company’s stock options.

Expected Dividend — The Company has not issued any dividends in its history and does not expect to issue dividends over the life of the options and therefore has estimated the dividend yield to be zero.

Fair value of Common Stock — The fair value of the shares of common stock underlying the stock-based awards has historically been determined by the board of directors, with input from management. Prior to the Company’s IPO, there has been no public market for the Company’s common stock, the board of directors determined the fair value of the common stock on the grant-date of the stock-based award by considering a number of objective and subjective factors, including enterprise valuations of the Company’s common stock performed by an unrelated third-party specialist, valuations of comparable companies, sales of the Company’s redeemable convertible preferred stock to unrelated third parties, operating and financial performance, the lack of liquidity of the Company’s capital stock, and general and industry-specific economic outlook. Subsequent to the IPO date, the board of directors uses the closing price of stock on the date of grant to determine the fair value. The board of directors intends all options granted to be exercisable at a price per share not less than the estimated per share fair value of common stock underlying those options on the date of grant.

As of December 31, 2019 and 2018, there was a total of $6.0 million and $1.57 million, respectively, of unrecognized employee and non-employee compensation costs related to non-vested stock option awards. The fair value of shares vested during the respective years was $1,193,000 and $102,000, respectively.

Employee Stock Purchase Plan

On April 24, 2019, the Company’s Board of Directors adopted its 2019 Employee Stock Purchase Plan (“2019 ESPP”), which was subsequently approved by the Company’s stockholders and became effective on May 7, 2019, the day immediately prior to the effectiveness of the registration statement filed in connection with the IPO. The 2019 ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Internal Revenue Code (the “Code”) for U.S. employees. In addition, the 2019 ESPP authorizes grants of purchase rights that do not comply with Section 423 of the Code under a separate non-423 component for non-U.S. employees and certain non-U.S. service providers. The Company has reserved 268,295 shares of common stock for issuance under the 2019 ESPP. In addition, the number of shares reserved for issuance under the 2019 ESPP will be increased automatically on the first day of each fiscal year for a period of up to ten years, starting with the 2020 fiscal year, by a number equal to the lesser of: (i) 536,589 shares; (ii) 1% of the shares of common stock outstanding on the last day of the prior fiscal year; or (iii) such lesser number of shares determined by the Company’s Board of Directors. The 2019 ESPP is expected to be implemented through a series of offerings under which participants are granted purchase rights to purchase shares of the Company’s common stock on specified dates during such offerings. The Company has not yet approved an offering under the 2019 ESPP.

Convertible Promissory Notes

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Convertible Promissory Notes

Note 10. Convertible Promissory Notes

In February 2017 the Company received $7.6 million from the issuance of convertible promissory notes to the Company’s current investors. In June 2017 the Company received an additional $150,000 from an issuance under the same note facility to a new investor. In January 2018 the Company received $250,000 from a new investor under the same note facility for a total of $8.0 million in principal value under the note facility. The notes accrue simple interest on the outstanding principal amount at the rate of 8% per annum and were set to mature on February 1, 2019.

The convertible promissory notes have conversion and repayment options as follows: (a) in the event that the Company has an equity financing event of at least $10 million to new investors on or before the maturity date, then the outstanding principal amount of this convertible promissory note and any unpaid accrued interest will automatically convert in whole into equity securities sold in the qualified financing at a conversion price equal to 80% of the cash price paid per share for equity securities by the investors in the qualified financing, or (b) the Company consummates a merger of the Company where it does not maintain majority voting power or conducts a sale, lease, transfer, exclusive license or other disposition of all or substantially all of its assets while the convertible promissory notes remain outstanding, the Company shall repay the holders in cash in an amount equal to 200% of the outstanding principal and accrued interest amount of the convertible promissory notes.

The Company evaluated its convertible notes and determined that the redemption premium feature qualified as a derivative liability to be separately accounted for in accordance with ASC 815. The convertible promissory notes contained put options as follows:

On or before the maturity date, the principal and accrued interest of the notes will automatically convert into equity securities issued and sold in the initial closing of the Company’s next qualified equity financing with gross proceeds of at least $10,000,000, exclusive of the conversion of the notes. The number of shares to be issued to the note holders will be equal to dividing the outstanding principal and any unpaid accrued interest by 80% of the price paid per share of the next equity security sold to investors. The discount in share price to note holders is not considered clearly and closely related to the debt host and results in an embedded derivative that must be bifurcated and accounted for separately from the debt host.

In the event of a merger or sale, lease, transfer, exclusive license or other disposition of all or substantially all of its assets prior to repayment, the outstanding principal and unpaid accrued interest will be repaid in cash, plus a repayment premium equal to 100% of the outstanding principal and accrued interest at the time of the merger or sale of assets. The premium to note holders is not considered clearly and closely related to the debt host and results in an embedded derivative that must be bifurcated and accounted for separately from the debt host.

Accordingly, upon the issuance of the February 2017 convertible promissory notes, the estimated fair value of the embedded derivative liability was determined using a bond plus option valuation model and assuming a probability of 80% that a qualified financing would occur and a zero probability that a merger or sale would occur. The Company recorded the estimated fair value of these put options (embedded derivatives) as a liability of $1.55 million with an offsetting amount recorded as debt discount, which offsets the carrying amount of the debt. The debt discount is amortized over the debt’s expected term. The derivative liability is revalued at the end of each reporting period and any change in fair value is recognized in other income.

Upon the issuance of the June 2017 convertible promissory notes, the estimated fair value of the embedded derivatives were determined using a bond plus option valuation model and assuming a probability of 80% that a qualified financing would occur and a zero probability that a sale or merger would occur. The Company recorded the estimated fair value of these put options (embedded derivatives) as a liability of $30,000 with an offsetting amount recorded as debt discount, which offsets the carrying amount of the debt.

Upon issuance of the January 2018 convertible promissory notes, the estimated fair value of the embedded derivatives was determined using a bond plus option valuation model and assuming a probability of 90% that a qualified financing would occur and a zero probability that a merger or sale would occur. The Company recorded the estimated fair value of these put options (embedded derivatives) as a liability of $56,250 with an offsetting amount recorded as debt discount, which offsets the carrying amount of the debt.

The derivative liability is revalued at the end of each reporting period and any change in fair value is recognized in “Change in fair value of redemption premium liability” in the Statement of Operations.

In May 2018, the notes converted into 1,147,205 shares of the Company’s Series B redeemable convertible preferred stock in conjunction with the Company’s Series B redeemable convertible preferred stock financing (the “Series B Financing”), which was considered a Qualified Financing under the terms of the notes. In conjunction with the closing, the holders of the notes also converted their accrued and unpaid interest of $0.8 million and the Company recorded a change in the fair value of the derivative liability of $206,000.

Related Party Transactions

12 Months Ended

Dec. 31, 2019

Related Party Transactions

Note 11. Related Party Transactions

In June 2014, the Company entered into a research grant and license agreement (the Agreement) with a stockholder of the Company. The Agreement requires the Company to pay royalties to the stockholder in the amount of 3% of gross revenues not to exceed $1.05 million. This agreement was amended in April 2019 and the royalty payment provision was removed.

As described in Note 6, the Company entered into a three-year lease agreement with a Series B redeemable preferred stock investor. The lease began on July 16, 2018 and provides 3,185 square feet of office space in South San Francisco, California. The Company issued 114,437 restricted shares of its Series B redeemable convertible preferred stock in exchange for the use of the leased facility. In May 2019, the Company entered into an amendment to the lease agreement to rent additional space in the same building for a one-time payment of approximately $63,000 on the same terms as the July 2018 agreement except rent.

Under the terms of the convertible promissory notes described in Note 10, certain board members provided $5.05 million in principal value in the note offering which accrued interest at 8% per annum. These board members received a total of $534,000 interest which converted per the terms of the promissory note into 69,465 shares of Series B redeemable convertible preferred stock on May 23, 2018.

As described in Note 1, the Company completed its IPO in May 2019. As a result of the IPO, in addition to the 229,453 shares of Series B redeemable convertible preferred stock held by the investor, an additional 82,649 shares of the Company’s Series B redeemable convertible preferred stock under issued pursuant the lease agreement fully vested and were converted into common stock of the Company on a one-to-one basis.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

Note 12. Income taxes

From inception through 2019, the Company has only generated pretax losses in the United States and has not generated any pretax income or loss outside of the United States. The Company did not record a provision (benefit) for income taxes for the years ended December 31, 2019 and 2018.

The provision for income taxes differs from the amount expected by applying the federal statutory rate to the loss before taxes as follows:

	Year ended December 31,
	2019				2018
Federal statutory income tax rate		21.00		%		21.00		%
State income taxes		(1.12	)	%	6.24			%
Income tax credits		3.67		%		—
Non-deductible expenses and others		(0.38	)	%		(1.02	)	%
Non-deductible expenses related to the convertible promissory notes		—		%		(1.96	)	%
Change in valuation allowance		(23.17	)	%		(24.26	)	%
		—		%		—		%

As of December 31, 2019 and 2018, the components of the Company’s deferred tax assets are as follows (in thousands):

	Year ended December 31,
	2019			2018
Deferred tax asset:
Federal and State net operating loss carryforwards	$	14,219		$	8,010
Stock based compensation		238			—
Other accruals and deferred expense		185			—
Tax credits		1,867			—
Total deferred tax asset		16,509			8,010
Deferred tax liabilities:
Property and equipment		(20	)		(70	)
Less valuation allowance		(16,489	)		(7,940	)
Net deferred tax assets	$	—		$	—

Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, and (b) operating losses and tax credit carryforwards.

The Company’s accounting for deferred taxes involves the evaluation of a number of factors concerning the realizability of its net deferred tax assets. The Company primarily considered such factors as its history of operating losses, the nature of the Company’s deferred tax assets, and the timing, likelihood and amount, if any, of future taxable income during the periods in which those temporary differences and carryforwards become deductible. At present, the Company does not believe that it is more likely than not that the deferred tax assets will be realized; accordingly, a full valuation allowance has been established and no deferred tax asset is shown in the accompanying balance sheets. The valuation allowance increased by approximately $8.5 million and $3.1 million respectively for the years ended December 31, 2019 and 2018.

At December 31, 2019, the Company has federal net operating loss carryforwards of approximately $62.3 million of which $46.4 million will not expire and $15.9 million begin expiring in 2034. The Company also has state net operating loss carryforwards of approximately $16.3 million which begin to expire in 2034. Additionally, the Company has federal and state tax credits of approximately $3.0 million which begin to expire in 2036.

Use of the net operating loss and credit carryforwards may be subject to a substantial annual limitation due to the ownership change provisions of U.S. tax law and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before use.

Uncertain Tax Positions

The Company follows the provisions of the FASB ASC 740-10, Accounting for Uncertainty in Income Taxes. ASC 740-10 prescribes a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of uncertain tax positions that have been taken or expected to be taken on a tax return. No liability related to uncertain tax positions is recorded in the financial statements.

The Company is subject to taxation in the United States. Because of the net operating loss and research credit carryforwards, all of the Company’s tax years, from 2013 to 2019, remain open to U.S. federal and California state tax examinations. There were no interest or penalties accrued at December 31, 2019 and December 31, 2018.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	Year ended December 31,
	2019		2018
Beginning balance	$	356	$	171
Additions for tax positions taken in a prior year		168	—
Additions for tax positions taken in a current year		535	185
Ending balance	$	1,059	$	356

Net Loss Per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

Note 13. Net Loss per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands except for share and per share amounts):

	December 31,
	2019			2018
Numerator:
Net loss	$	(36,980	)	$	(12,476	)
Denominator
Weighted average common shares outstanding		19,031,940			3,362,192
Net loss per share, basic and diluted	$	(1.94	)	$	(3.71	)

The following outstanding potentially dilutive securities were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive:

	December 31,
	2019		2018
Series A convertible preferred stock		—		9,008,919
Series B convertible preferred stock		—		9,152,108
Options issued and outstanding		2,393,934		1,885,504
Warrants		—		27,941
		2,393,934		20,074,472

Employee Benefit Plan

12 Months Ended

Dec. 31, 2019

Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract]

Employee Benefit Plan

Note 14. Employee Benefit Plan

The Company sponsors a 401(k) defined contribution plan for its employees. This plan provides for pre-tax and post-tax contributions for all employees. Employee contributions are voluntary. Employees may contribute up to 100% of their annual compensation to this plan, as limited by an annual maximum amount as determined by the Internal Revenue Service. The Company may match employee contributions, and may make profit sharing contributions, in amounts to be determined at the Company’s sole discretion. The Company made no contributions to the plan for the years ended December 31, 2019 and 2018.

Subsequent Events

12 Months Ended

Dec. 31, 2019

Subsequent Events [Abstract]

Subsequent Events

Note 15. Subsequent Events

Private Investment in Public Equity (“PIPE”)

On February 10, 2020, the Company sold and issued 2,500,000 shares of common stock in a private placement to a group of institutional investors and an entity affiliated with a member of the Company’s board of directors for aggregate gross proceeds of $125.0 million. Costs related to the offering were $7.4 million. In connection with the private placement, the Company is obligated to prepare and file with the SEC within 60 days of the closing date, a registration statement to register for resale the shares of common stock sold in the private placement.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Risk and Uncertainties

Segments

Cash, Cash Equivalents and Investments

Property and Equipment, Net

Concentration of Credit Risk

Impairment of Long-Lived Assets

Deferred Offering Costs

Research and Development Expenses

•

fees paid to Contract Research Organizations, or CROs, in connection with clinical studies;

•

fees paid to investigative sites in connection with clinical studies;

•

fees paid to contract manufacturers in connection with the production of clinical study materials; and

•

fees paid to vendors in connection with preclinical development activities.

Patents Costs

Patent Costs

The Company has no historical data to support a probable future economic benefit for the arising patent applications, filing and prosecution costs. Therefore, patent costs are expensed as incurred.

Stock-Based Compensation

Redeemable Convertible Preferred Stock

Fair Value of Warrants

Derivatives Liability

Derivative Liability

Income Taxes

The Company includes any penalties and interest expense related to income taxes as a component of other expense and interest expense, net, as necessary.

Comprehensive Income (Loss)

Net Loss per Share

Recent Accounting Pronouncements and Recently Adopted Accounting Pronouncements

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

All other newly issued accounting pronouncements not yet effective have been deemed either immaterial or not applicable.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities to Fair Value Measurements on Recurring Basis

	Fair Value Measurements at December 31, 2019
	Total		Level 1		Level 2		Level 3
Money market funds	$	30,054	$	30,054	$	—	$	—
Certificates of Deposit		20,046		—		20,046		—
Repurchase Agreements		15,000		—		15,000		—
Corporate notes		38,783		—		38,783		—
Government notes		7,574		—		7,574		—
Commercial Paper		1,096		—		1,096		—
Total	$	112,553	$	30,054	$	82,499	$	—

	Fair Value Measurements at December 31, 2018
	Total		Level 1		Level 2		Level 3
Money market funds	$	11,815	$	11,815	$	—	$	—
Commercial Paper		14,360		—		14,360		—
Corporate notes		16,111		—		16,111		—
Government notes		8,979		—		8,979		—
Asset backed securities		9,192		—		9,192		—
Total	$	60,457	$	11,815	$	48,642	$	—

Summary of Change in Derivative Liability

The change in the derivative liability is as follows (in thousands):

	December 31,
	2019		2018
Fair Value at beginning of period	$	—	$	1,886
Bifurcated derivative liability		—		113
Change in fair value		—		206
Conversion of promissory notes to Series B redeemable convertible preferred stock		—		(2,205	)
Fair value at end of period	$	—	$	—

Cash, Cash Equivalents and Investments (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Fair Values of Cash, Cash Equivalents, and Short-Term Investments Measured at Fair Value on Recurring Basis

The following tables categorize the fair values of cash, cash equivalents, and short-term investments measured at fair value on a recurring basis on our balance sheet (in thousands):

		December 31,
	2019			2018
Cash and cash equivalents:
Cash	$		4,074	$	11,259
Money market funds			30,054		11,815
Commercial paper			—		1,798
Certificate of deposits			985		—
Repurchase agreements			15,000		—
Corporate notes			1,101		—
Total cash and cash equivalents	$		51,214	$	24,872

Short-term investments:
Commercial paper			1,096		12,562
Corporate notes			24,552		16,111
Government notes			7,574		8,979
Certificate of deposits			15,428		9,192
Total short-term investments	$		48,650	$	46,844

Long-term investments:
Corporate notes			13,130		—
Certificate of deposits			3,633
Total long-term investments	$		16,763	$	—

Summary of Available-for-Sale Securities

The following table summarizes the available-for-sale securities (in thousands):

	Fair Value Measurements at December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	30,054	$	—	$	—		$	30,054
Certificates of Deposit		19,992		54		—			20,046
Repurchase Agreements		15,000		—		—			15,000
Corporate notes		38,788		—		(5	)		38,783
Government notes		7,563		11					7,574
Commercial Paper		1,096		—		—			1,096
Total cash equivalents and investments	$	112,493	$	65	$	(5	)	$	112,553

Classified as:
Cash equivalents (maturities within 90 days)								$	47,140
Short-term investments (maturities within one year)									48,650
Long-term investments (maturities beyond 1 year)									16,763
Total cash equivalents and investments								$	112,553

	Fair Value Measurements at December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	11,815	$	—	$	—		$	11,815
Commercial paper		14,362		—		(2	)		14,360
Corporate notes		16,129		—		(18	)		16,111
U.S. government notes		8,980		—		(1	)		8,979
Asset backed securities		9,220		—		(28	)		9,192
Total cash equivalents and investments	$	60,506	$	—	$	(49	)	$	60,457

Classified as:
Cash equivalents (maturities within 90 days)								$	13,613
Short-term investments (maturities within one year)									46,844
Total cash equivalents and investments								$	60,457

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2019

Balance Sheet Components [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):

	December 31,
	2019		2018
Prepaid expenses	$	987	$	47
Prepaid research and development expenses		4,517		753
Other current assets		688		68
	$	6,192	$	868

Schedule of Property and Equipment,Net

Property and equipment, net consisted of the following (in thousands):

	December 31,
	2019			2018
Computer Equipment	$	28		$	—
Lab Equipment		405			378
Finance lease right of use assets		559			—
Less: accumulated amortization and depreciation		(283	)		(95	)
Property and equipment, net	$	709		$	283

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2019		2018
Personnel expense	$	1,261	$	483
Research and development expenses		4,410		380
Professional fees		96		75
Other		50		24
Total accrued liabilities	$	5,817	$	962

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Summary of Operating Lease and Finance Lease Right of Use Asset

Operating and finance lease right of use asset amounts consist of the following as of December 31, 2019 (in thousands):

Operating lease right of use asset, net	$	625

Finance lease right of use asset		559
Finance lease accumulated amortization		(107	)
Total finance lease right of use asset, net	$	452

Summary of Lease Costs

Lease costs for the years ended December 31, 2019 was approximately:

Lease costs:
Finance lease amortization of right of use assets	$	107
Operating lease costs		374
Short-term lease costs		11
Total lease costs	$	492

Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Schedule of Outstanding Redeemable Convertible Preferred Stock

As of December 31, 2018, the outstanding redeemable convertible preferred stock was as follows (in thousands except for share and per share amounts):

Authorized

Shares Issued

and Outstanding

Issuance Price

per share

Liquidation

Preference

Carrying Value

Series A

9,008,931

9,008,919

1.9067

17,178

Series B

9,430,145

9,152,108

9.6122

87,972

86,868

Schedule of Reserved Common Stock for Issuance

As of December 31, 2019, the Company had reserved common stock for issuance as follows:

	December 31, 2019
Options issued and outstanding under the 2019 Stock Plan		2,393,934
Shares available for issuance under 2019 Stock Plan		2,439,779
Shares available for issuance under the Employee Stock Ownership Plan		268,295
Total		5,102,008

Stock Option Plan (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Options Activity

Stock option activity under the 2019 Plan is as follows:

	Number of Options			Weighted Average Exercise Price			Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Balance at December 31, 2017		769,409		$	0.39		8.89				1,107,581
Options granted		1,316,342			2.08		—			—
Options exercised		(51,350	)		0.46		—			—
Options cancelled		(148,897	)		0.41		—			—
Balance at December 31, 2018		1,885,504			1.57		9.07				1,252,496
Options granted		932,639				15.87	—			—
Options exercised		(194,279	)			0.51	—			—
Options forfeited / expired		(229,930	)			21.09	—			—
Balance at December 31, 2019		2,393,934		$	5.35			8.62	$		121,592,682
Options vested and expected to vest to December 31, 2019		2,393,934		$	5.35			8.62	$		121,592,682
Options exercisable at December 31, 2019		751,334		$		2.59		7.96	$		40,235,852

Summary of Employee and Non-Employee Stock-Based Compensation Expense

	2019		2018
General and administrative expense	$	1,378	$	78
Research and development expense		678		77
Total stock-based compensation		2,056		155

Summary of Weighted Average Assumptions to Calculate the Fair Value of Stock-Based Compensation

The following weighted average assumptions were used to calculate the fair value of stock-based compensation as of December 31, 2019 and 2018:

	2019			2018
Expected volatility		80.19	%		69.6	%
Expected dividend yield		—	%		—	%
Expected term (in years)	6.25			6.25
Risk-free interest rate		1.90	%		2.91	%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Provision for Income Taxes Differs From the Amount Expected by Applying the Federal Statutory Rate to Loss Before Taxes

The provision for income taxes differs from the amount expected by applying the federal statutory rate to the loss before taxes as follows:

	Year ended December 31,
	2019				2018
Federal statutory income tax rate		21.00		%		21.00		%
State income taxes		(1.12	)	%	6.24			%
Income tax credits		3.67		%		—
Non-deductible expenses and others		(0.38	)	%		(1.02	)	%
Non-deductible expenses related to the convertible promissory notes		—		%		(1.96	)	%
Change in valuation allowance		(23.17	)	%		(24.26	)	%
		—		%		—		%

Schedule of Components of Deferred Tax Assets

As of December 31, 2019 and 2018, the components of the Company’s deferred tax assets are as follows (in thousands):

	Year ended December 31,
	2019			2018
Deferred tax asset:
Federal and State net operating loss carryforwards	$	14,219		$	8,010
Stock based compensation		238			—
Other accruals and deferred expense		185			—
Tax credits		1,867			—
Total deferred tax asset		16,509			8,010
Deferred tax liabilities:
Property and equipment		(20	)		(70	)
Less valuation allowance		(16,489	)		(7,940	)
Net deferred tax assets	$	—		$	—

Schedule of Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	Year ended December 31,
	2019		2018
Beginning balance	$	356	$	171
Additions for tax positions taken in a prior year		168	—
Additions for tax positions taken in a current year		535	185
Ending balance	$	1,059	$	356

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands except for share and per share amounts):

	December 31,
	2019			2018
Numerator:
Net loss	$	(36,980	)	$	(12,476	)
Denominator
Weighted average common shares outstanding		19,031,940			3,362,192
Net loss per share, basic and diluted	$	(1.94	)	$	(3.71	)

Schedule of Outstanding Potentially Dilutive Ordinary Shares Excluded from Calculation of Diluted Net Loss Per Share

	December 31,
	2019		2018
Series A convertible preferred stock		—		9,008,919
Series B convertible preferred stock		—		9,152,108
Options issued and outstanding		2,393,934		1,885,504
Warrants		—		27,941
		2,393,934		20,074,472

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	May 13, 2019 USD ($) $ / shares shares	Apr. 25, 2019	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Entity incorporation date			2012-06
Description of reverse stock split		one-for-0.367647
Reverse stock split		0.367647
Proceeds from issuance of common stock, net of underwriting discounts and commissions and offering expenses \| $			$ 77,827
Accumulated deficit \| $			(69,805)	$ (32,825)
Cash, cash equivalents, and short-term investments \| $			$ 99,900
IPO
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Issuance of stock (in shares) \| shares	5,073,800
Public offering price per share \| $ / shares	$ 17
Proceeds from issuance of common stock, net of underwriting discounts and commissions and offering expenses \| $	$ 77,800
Conversion of redeemable convertible preferred stock to common stock \| shares	18,161,027		18,161,027
Redeemable convertible preferred stock, shares outstanding \| shares			0
Underwriters
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Issuance of stock (in shares) \| shares	661,800

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) Segment shares	May 13, 2019 shares	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($) shares
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segment \| Segment	1
Number of operating segment \| Segment	1
Property and Equipment Useful Life	5 years
Percentage of holders demanded on redemption of stock	60.00%
Warrants to purchase shares of common stock outstanding \| shares	0			27,941
Right-of-use asset	$ 625,000
Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Right-of-use asset			$ 900,000
Short-term lease liability			300,000
Long-term lease liability			600,000
Cumulative effect adjustment			$ 0
IPO
Summary Of Significant Accounting Policies [Line Items]
Conversion of redeemable convertible preferred stock to common stock \| shares	18,161,027	18,161,027
Redeemable convertible preferred stock, shares outstanding \| shares	0
Prepaid Expenses and Other Assets
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs				$ 34,000

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value assets level 1 to level 2	$ 0	$ 0
Fair value assets level 2 to level 1	0	0
Fair value assets transfers into level 3	0	0
Fair value assets transfers out of level 3	$ 0	$ 0

Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	$ 112,553	$ 60,457
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	30,054	11,815
Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	20,046
Repurchase Agreements
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	15,000
Corporate Notes
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	38,783	16,111
Government Notes
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	7,574	8,979
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	1,096	14,360
Asset Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities		9,192
Level 1
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	30,054	11,815
Level 1 \| Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	30,054	11,815
Level 2
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	82,499	48,642
Level 2 \| Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	20,046
Level 2 \| Repurchase Agreements
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	15,000
Level 2 \| Corporate Notes
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	38,783	16,111
Level 2 \| Government Notes
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	7,574	8,979
Level 2 \| Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities	$ 1,096	14,360
Level 2 \| Asset Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Financial assets and liabilities		$ 9,192

Fair Value Measurements - Summary of Change in Derivative Liability (Details) - Derivative Liability $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value at beginning of period	$ 1,886
Bifurcated derivative liability	113
Change in fair value	206
Conversion of promissory notes to Series B redeemable convertible preferred stock	$ (2,205)

Cash, Cash Equivalents and Investments - Summary of Fair Values of Cash, Cash Equivalents, and Short-Term Investments Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	$ 47,140	$ 13,613
Short term investments	48,650	46,844
Long term investments	16,763
Fair Value on Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	51,214	24,872
Short term investments	48,650	46,844
Long term investments	16,763
Fair Value on Recurring \| Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	4,074	11,259
Fair Value on Recurring \| Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	30,054	11,815
Fair Value on Recurring \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents		1,798
Short term investments	1,096	12,562
Fair Value on Recurring \| Certificates of Deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	985
Short term investments	15,428	9,192
Long term investments	3,633
Fair Value on Recurring \| Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	15,000
Fair Value on Recurring \| Corporate Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash and cash equivalents	1,101
Short term investments	24,552	16,111
Long term investments	13,130
Fair Value on Recurring \| Government Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short term investments	$ 7,574	$ 8,979

Cash, Cash Equivalents and Investments - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Realized gains or losses on the sale or maturity of available-for-sale securities	$ 0	$ 0
Amounts reclassify out of accumulated other comprehensive income	$ 0

Cash, Cash Equivalents and Investments - Summary of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 112,493	$ 60,506
Unrealized Gains	65
Unrealized Losses	(5)	(49)
Financial assets and liabilities	112,553	60,457
Cash equivalents (maturities within 90 days)	47,140	13,613
Short-term investments (maturities within one year)	48,650	46,844
Long-term investments (maturities beyond 1 year)	16,763
Total cash equivalents and investments	112,553	60,457
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	30,054	11,815
Financial assets and liabilities	30,054	11,815
Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	19,992
Unrealized Gains	54
Financial assets and liabilities	20,046
Repurchase Agreements
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	15,000
Financial assets and liabilities	15,000
Corporate Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	38,788	16,129
Unrealized Losses	(5)	(18)
Financial assets and liabilities	38,783	16,111
Government Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	7,563	8,980
Unrealized Gains	11
Unrealized Losses		(1)
Financial assets and liabilities	7,574	8,979
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,096	14,362
Unrealized Losses		(2)
Financial assets and liabilities	$ 1,096	14,360
Asset Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		9,220
Unrealized Losses		(28)
Financial assets and liabilities		$ 9,192

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Prepaid Expense And Other Assets Current [Abstract]
Prepaid expenses	$ 987	$ 47
Prepaid research and development expenses	4,517	753
Other current assets	688	68
Total prepaid expenses and other current assets	$ 6,192	$ 868

Balance Sheet Components - Schedule of Property and Equipment,Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Less: accumulated amortization and depreciation	$ (283)	$ (95)
Property and equipment, net	709	283
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment	28
Lab Equipment
Property Plant And Equipment [Line Items]
Property and equipment	405	$ 378
Finance Lease Right of Use Assets
Property Plant And Equipment [Line Items]
Property and equipment	$ 559

Balance Sheet Components - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Prepaid Expense And Other Assets Current [Abstract]
Depreciation	$ 188,000	$ 51,000

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Personnel expense	$ 1,261	$ 483
Research and development expenses	4,410	380
Professional fees	96	75
Other	50	24
Total accrued liabilities	$ 5,817	$ 962

Leases - Additional Information (Details)	1 Months Ended		12 Months Ended
Leases - Additional Information (Details)	May 31, 2019 USD ($)	Jun. 30, 2018 USD ($) ft² Investor shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	May 13, 2019	Jul. 16, 2018
Lessee Lease Description [Line Items]
Lease agreement period						3 years
Renewal options	false
Number of investors \| Investor		1
Operating lease payments	$ 0	$ 0
Repurchase option percentage		100.00%
Operating leases period		3 years
Operating lease payments paid for additional space	$ 63,000
Operating lease termination month and year	2021-07
Operating lease liability	$ 0
Future rent expense			$ 625,000
Operating lease remaining term on a straight-line basis			19 months
Term of clinical equipment financing lease			3 years
Finance lease liability			$ 0
Amortization expense of finance lease right-of-use asset			$ 107,000
Operating lease discount rate percent			4.00%
Operating lease discount rate term			1 year 7 months 6 days
Finance lease discount rate term			2 years 1 month 2 days
Operating lease rent expense				$ 387,000
Minimum
Lessee Lease Description [Line Items]
Finance lease amortized period on equipment service			28 months
Maximum
Lessee Lease Description [Line Items]
Finance lease amortized period on equipment service			34 months
Series B Redeemable Convertible Preferred Stock
Lessee Lease Description [Line Items]
Lease agreement period		3 years
Renewal options		false
Area under lease \| ft²		3,185
Redeemable convertible preferred stock, shares issued \| shares		114,437	0	9,152,108
Convertible preferred stock, fair value		$ 1,100,000
Series B Redeemable Convertible Preferred Stock \| IPO
Lessee Lease Description [Line Items]
Conversion of redeemable convertible preferred stock to common stock ratio	100.00%				100.00%

Leases - Summary of Operating Lease and Finance Lease Right of Use Assets (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease right-of-use assets, net	$ 625
Finance lease right of use asset	559
Finance lease accumulated amortization	(107)
Total finance lease right of use asset, net	$ 452

Leases - Summary of Lease Costs (Details) $ in Thousands	12 Months Ended
Leases - Summary of Lease Costs (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Lease costs:
Amortization expense of finance lease right-of-use asset	$ 107
Operating lease costs	374
Short-term lease costs	11
Total lease costs	$ 492

Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - Schedule of Outstanding Redeemable Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, Shares Authorized	0	9,008,931
Redeemable convertible preferred stock, Shares issued	0	9,008,919
Redeemable convertible preferred stock, Shares Outstanding	0	9,008,919		9,008,919
Redeemable convertible preferred stock, Issuance Price per share		$ 1.9067
Redeemable convertible preferred stock, Liquidation Preference	$ 0	$ 17,178
Redeemable convertible preferred stock, Carrying Value		$ 17,178		$ 17,178
Series B Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, Shares Authorized	0	9,430,145
Redeemable convertible preferred stock, Shares issued	0	9,152,108	114,437
Redeemable convertible preferred stock, Shares Outstanding	0	9,152,108
Redeemable convertible preferred stock, Issuance Price per share		$ 9.6122
Redeemable convertible preferred stock, Liquidation Preference	$ 0	$ 87,972
Redeemable convertible preferred stock, Carrying Value		$ 86,868

Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	May 13, 2019	Dec. 31, 2018	Jun. 30, 2014
Equity [Line Items]
Common stock, shares authorized	100,000,000		24,794,114
Common stock, par value	$ 0.001		$ 0.001
Common stock, shares issued	26,869,413		3,412,366
Common stock, shares outstanding	26,869,413		3,412,366
Common stock, voting rights	Each share of common stock is entitled to one vote.
Warrants to purchase common stock				27,941
Warrants to purchase common stock, per share				$ 0.03
Warrant expiration date	2024-06
Warrant exercised month and year	2019-05
IPO
Equity [Line Items]
Conversion of redeemable convertible preferred stock to common stock	18,161,027	18,161,027
Redeemable convertible preferred stock, shares outstanding	0

Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - Schedule of Reserved Common Stock for Issuance (Details)	Dec. 31, 2019 shares
Class Of Stock [Line Items]
Total	5,102,008
Options Issued And Outstanding Under The 2019 Stock Plan
Class Of Stock [Line Items]
Total	2,393,934
Shares Available for Issuance Under 2019 Stock Plan
Class Of Stock [Line Items]
Total	2,439,779
Shares Available for Issuance Under Employee Stock Ownership Plan
Class Of Stock [Line Items]
Total	268,295

Stock Option Plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	May 07, 2019	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	5,102,008
Income tax benefits recognized	$ 0
Unrecognized stock-based compensation cost	6,000,000	$ 1,570,000
Total intrinsic value of options exercised	$ 886,989	$ 91,000
Weighted average grant date fair value of options vested	$ 2.35
Weighted average grant date fair value of options granted	$ 11.11	$ 1.26
Expected term	6 years 3 months	6 years 3 months
Expected dividend yield	0.00%
Fair value of stock options vested	$ 1,193,000	$ 102,000
Arithmetic Average
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	10 years
Employees and Non-Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense related to options granted	$ 2,056,000	155,000
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum aggregate number of shares that may be issued under the plan			5,131,549
Increase in number of shares available for issuance as proportion of shares of common stock	2,146,354
Percentage of common stock outstanding	4.00%
Common stock reserved for issuance	2,439,779
Unrecognized stock-based compensation cost	$ 6,400,000
Unrecognized share-based compensation cost expected to be recognized, period	1 year 5 months 1 day
Total intrinsic value of options exercised	$ 121,592,682	$ 1,252,496		$ 1,107,581
2019 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares available for issuance as proportion of shares of common stock	536,589
Percentage of common stock outstanding	1.00%
Common stock reserved for issuance			268,295
Maximum period for common stock shares reserved for future issuance	10 years

Stock Option Plan - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate Intrinsic Value	$ 886,989	$ 91,000
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, beginning balance	1,885,504	769,409
Number of Options, granted	932,639	1,316,342
Number of Options, exercised	(194,279)	(51,350)
Number of Options, cancelled		(148,897)
Number of Options, forfeited / expired	(229,930)
Number of Options, ending balance	2,393,934	1,885,504	769,409
Number of Options, vested and expected to vest	2,393,934
Number of Options, exercisable	751,334
Weighted Average Exercise Price, beginning balance	$ 1.57	$ 0.39
Weighted Average Exercise Price, granted	15.87	2.08
Weighted Average Exercise Price, exercised	0.51	0.46
Weighted Average Exercise Price, cancelled		0.41
Weighted Average Exercise Price, forfeited / expired	21.09
Weighted Average Exercise Price, ending balance	5.35	$ 1.57	$ 0.39
Weighted Average Exercise Price, vested and expected to vest	5.35
Weighted Average Exercise Price, exercisable	$ 2.59
Weighted Average Remaining Contractual Life	8 years 7 months 13 days	9 years 25 days	8 years 10 months 20 days
Weighted Average Remaining Contractual Life, vested and expected to vest	8 years 7 months 13 days
Weighted Average Remaining Contractual Life, exercisable	7 years 11 months 15 days
Aggregate Intrinsic Value	$ 121,592,682	$ 1,252,496	$ 1,107,581
Aggregate Intrinsic Value, vested and expected to vest	121,592,682
Aggregate Intrinsic Value, exercisable	$ 40,235,852

Stock Option Plan - Summary of Employee and Non-Employee Stock-Based Compensation Expense (Details) - Employees and Non-Employees - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 2,056,000	$ 155,000
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	1,378,000	78,000
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 678,000	$ 77,000

Stock Option Plan - Summary of Weighted Average Assumptions to Calculate the Fair Value of Stock-Based Compensation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected volatility	80.19%	69.60%
Expected dividend yield	0.00%
Expected term (in years)	6 years 3 months	6 years 3 months
Risk-free interest rate	1.90%	2.91%

Convertible Promissory Notes - Additional Information (Details) - USD ($)	1 Months Ended				12 Months Ended	24 Months Ended
	May 31, 2018	Jan. 31, 2018	Jun. 30, 2017	Feb. 28, 2017	Dec. 31, 2018	Jan. 31, 2019
Debt Instrument [Line Items]
Proceeds from issuance of convertible promissory note payable		$ 250,000	$ 150,000	$ 7,600,000	$ 250,000
Convertible promissory notes, Principal amount						$ 8,000,000
Change in fair value of derivative liability					(206,000)
Series B Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Conversion of redeemable convertible preferred stock to common stock, shares	1,147,205
Issuance of stock in connection with conversion of convertible promissory notes and accrued interest	$ 800,000				$ 11,027,000
Change in fair value of derivative liability	$ 206,000
Convertible Promissory Notes
Debt Instrument [Line Items]
Convertible promissory notes interest rate						8.00%
Convertible promissory notes maturity date						Feb. 01, 2019
Minimum equity financing threshold for promissory note conversion into equity securities		$ 10,000,000
Conversion price percentage		80.00%				80.00%
Percentage of outstanding principle and accrued interest amount repayment		200.00%
Minimum gross proceeds equity financing threshold for promissory note conversion into equity securities						$ 10,000,000
Percentage of repayment premium equal to outstanding principle and accrued interest						100.00%
Debt instrument convertible conversion probability percentage in event of equity financing		90.00%	80.00%	80.00%
Debt instrument repayment probability percentage in event of merger or sale		0.00%	0.00%	0.00%
Estimated fair value of embedded derivatives liability		$ 56,250,000,000	$ 30,000,000,000	$ 1,550,000

Related Party Transactions - Additional Information (Detail)			1 Months Ended
	Jul. 16, 2018 ft² shares	May 23, 2018 USD ($) shares	May 31, 2019 USD ($) shares	May 31, 2018 shares	Jun. 30, 2014 USD ($)	Dec. 31, 2019 USD ($)	May 13, 2019	Jan. 31, 2019 USD ($)	Jun. 30, 2018
Related Party Transaction [Line Items]
Percentage of royalties payment to stockholders in amount of gross revenues					3.00%
Lease agreement period	3 years
Restricted stock shares issued \| shares	114,437
Operating lease payments paid for additional space \| $			$ 63,000
Convertible promissory notes \| $								$ 8,000,000
Series B Redeemable Convertible Preferred Stock
Related Party Transaction [Line Items]
Lease agreement period									3 years
Conversion of preferred stock into common stock \| shares				1,147,205
Series B Redeemable Convertible Preferred Stock \| IPO
Related Party Transaction [Line Items]
Conversion of preferred stock into common stock \| shares			82,649
Conversion of redeemable convertible preferred stock to common stock ratio			100.00%				100.00%
Board Of Directors
Related Party Transaction [Line Items]
Convertible promissory notes \| $		$ 5,050,000
Convertible promissory notes interest rate						8.00%
Interest payable to related party \| $						$ 534,000
Board Of Directors \| Series B Redeemable Convertible Preferred Stock
Related Party Transaction [Line Items]
Conversion of convertible promissory notes \| shares		69,465
Series B Redeemable Convertible Preferred Stock Investor \| Series B Redeemable Convertible Preferred Stock \| IPO
Related Party Transaction [Line Items]
Conversion of preferred stock into common stock \| shares			229,453
South San Francisco, California
Related Party Transaction [Line Items]
Area of lease office space \| ft²	3,185
Maximum
Related Party Transaction [Line Items]
Payment of royalties to stockholders \| $					$ 1,050,000

Income Taxes - Schedule of Provision for Income Taxes Differs From the Amount Expected by Applying the Federal Statutory Rate to Loss Before Taxes (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%
State income taxes	(1.12%)	6.24%
Income tax credits	3.67%
Non-deductible expenses and others	(0.38%)	(1.02%)
Non-deductible expenses related to the convertible promissory notes		(1.96%)
Change in valuation allowance	(23.17%)	(24.26%)

Income Taxes - Schedule of Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax asset:
Federal and State net operating loss carryforwards	$ 14,219	$ 8,010
Total deferred tax asset	16,509	8,010
Stock based compensation	238
Other accruals and deferred expense	185
Tax credits	1,867
Deferred tax liabilities:
Property and equipment	(20)	(70)
Less valuation allowance	$ (16,489)	$ (7,940)

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Deferred tax asset	$ 0
Valuation allowances increased	8,500,000	$ 3,100,000
Liability related to uncertain tax positions	0
Interest or penalties accrued	$ 0	$ 0
Earliest Tax Year \| U.S. Federal
Income Taxes [Line Items]
Open tax year	2013
Earliest Tax Year \| California State Tax Examinations
Income Taxes [Line Items]
Open tax year	2013
Latest Tax Year \| U.S. Federal
Income Taxes [Line Items]
Open tax year	2019
Latest Tax Year \| California State Tax Examinations
Income Taxes [Line Items]
Open tax year	2019
U.S. Federal
Income Taxes [Line Items]
Operating loss carryforwards	$ 62,300,000
Operating loss carryforwards begin to expire	2034
State
Income Taxes [Line Items]
Operating loss carryforwards	$ 16,300,000
Operating loss carryforwards begin to expire	2034
U.S. Federal and State
Income Taxes [Line Items]
Tax credit carryforwards	$ 3,000,000
Tax credits carryforwards begin to expire	2036

Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Beginning balance	$ 356	$ 171
Additions for tax positions taken in a prior year	168
Additions for tax positions taken in a current year	535	185
Ending balance	$ 1,059	$ 356

Net Loss Per Share - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (36,980)	$ (12,476)
Denominator
Weighted average common shares outstanding	19,031,940	3,362,192
Net loss per share - basic and diluted	$ (1.94)	$ (3.71)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss Per Share - Schedule of Outstanding Potentially Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount	2,393,934	20,074,472
Series A Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount		9,008,919
Series B Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount		9,152,108
Options Issued and Outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount	2,393,934	1,885,504
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount		27,941

Employee Benefit Plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract]
Percentage of employee contribution of their annual compensation	100.00%
Contributions	$ 0	$ 0
Defined contribution plan name	401(k)

Subsequent Events - Additional Information (Details) - Private Placement - Subsequent Event $ in Millions	Feb. 10, 2020 USD ($) shares
Subsequent Event [Line Items]
Agreement date	Feb. 10, 2020
Number of shares issued and sold \| shares	2,500,000
Proceeds from issuance of common stock	$ 125.0
Costs related to offering	$ 7.4