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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Aug. 09, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
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 Current Reporting Status	Yes
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		26,841,149
Entity File Number	001-38890
Entity Tax Identification Number	901024039
Entity Address, Address Line One	269 East Grand Ave.
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	California
Entity Address, Country	UNITED STATES
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	910-5717
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 44,314	$ 24,872
Short term investments	83,974	46,844
Restricted cash	250
Prepaid expenses and other current assets	5,105	868
Total current assets	133,643	72,584
Property and equipment, net	265	283
Right-of-use assets	1,086
Long term investments	7,988
Other assets	260	10
Total assets	143,242	72,877
Current liabilities:
Accounts Payable	5,116	495
Accrued expenses and other current liabilities	1,909	962
Total current liabilities	7,025	1,457
Total liabilities	7,025	1,457
Commitments and contingencies (Note 6)
Stockholders’ deficit:
Preferred Stock, $0.001 par value, 10,000,000 authorized, no shares issued and outstanding June 30, 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, 26,841,149 and 3,412,366 issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	27	3
Additional paid in capital	183,678	245
Accumulated other comprehensive profit (loss)	80	(49)
Accumulated deficit	(47,568)	(32,825)
Total stockholders’ equity / (deficit)	136,217	(32,626)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity / (deficit)	$ 143,242	72,877
Series A Redeemable Convertible Preferred Stock
Current liabilities:
Series A redeemable convertible preferred stock, par value $0.001, no shares authorized, issued and outstanding as of June 30, 2019 and 9,008,931 shares authorized, 9,008,919 shares issued and outstanding December 31, 2018; liquidation preference of $0 and $17,178 at June 30, 2019 and December 31, 2018, respectively		17,178
Series B Redeemable Convertible Preferred Stock
Current liabilities:
Series A redeemable convertible preferred stock, par value $0.001, no shares authorized, issued and outstanding as of June 30, 2019 and 9,008,931 shares authorized, 9,008,919 shares issued and outstanding December 31, 2018; liquidation preference of $0 and $17,178 at June 30, 2019 and December 31, 2018, respectively		$ 86,868

Condensed Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Jun. 30, 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	26,841,149	3,412,366
Common stock, shares outstanding	26,841,149	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

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 7,109	$ 2,286	$ 11,934	$ 4,699
General and administrative	2,466	357	3,716	704
Total operating expenses	9,575	2,643	15,650	5,403
Loss from operations	(9,575)	(2,643)	(15,650)	(5,403)
Interest income	513	81	907	81
Interest expense		(358)		(957)
Change in fair value of derivative liability		(188)		(206)
Net loss	(9,062)	(3,108)	(14,743)	(6,485)
Other comprehensive loss:
Unrealized gain on available for sales securities	103		129
Total comprehensive loss	$ (8,959)	$ (3,108)	$ (14,614)	$ (6,485)
Net loss per share - basic and diluted	$ (0.57)	$ (0.93)	$ (1.52)	$ (1.93)
Weighted average shares of common stock outstanding - basic and diluted	15,849,189	3,360,109	9,719,173	3,360,049

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - 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
Stock based compensation	27				27
Proceeds from Series B redeemable convertible preferred stock, net of issuance costs, shares			7,890,466
Proceeds from Series B redeemable convertible preferred stock, net of issuance costs			$ 75,688
Conversion of convertible promissory notes to common stock, shares			1,147,205
Conversion of convertible promissory notes to common stock			$ 11,027
Net Loss	(6,485)						(6,485)
Ending balance at Jun. 30, 2018	(26,738)			$ 3	93		(26,834)
Ending balance, shares at Jun. 30, 2018		9,008,919	9,037,671
Ending balance at Jun. 30, 2018		$ 17,178	$ 86,715
Ending balance, shares at Jun. 30, 2018				3,361,016
Beginning balance at Mar. 31, 2018	(23,644)			$ 3	79		(23,726)
Beginning balance, shares at Mar. 31, 2018		9,008,919
Beginning balance at Mar. 31, 2018		$ 17,178
Beginning balance, shares at Mar. 31, 2018				3,361,016
Stock based compensation	14				14
Proceeds from Series B redeemable convertible preferred stock, net of issuance costs, shares			7,890,466
Proceeds from Series B redeemable convertible preferred stock, net of issuance costs			$ 75,688
Conversion of convertible promissory notes to common stock, shares			1,147,205
Conversion of convertible promissory notes to common stock			$ 11,027
Net Loss	(3,108)						(3,108)
Ending balance at Jun. 30, 2018	(26,738)			$ 3	93		(26,834)
Ending balance, shares at Jun. 30, 2018		9,008,919	9,037,671
Ending balance at Jun. 30, 2018		$ 17,178	$ 86,715
Ending balance, shares at Jun. 30, 2018				3,361,016
Beginning balance at Dec. 31, 2018	(32,626)			$ 3	245	$ (49)	(32,825)
Beginning balance, shares at Dec. 31, 2018		9,008,919	9,152,108
Beginning balance at Dec. 31, 2018		$ 17,178	$ 86,868
Beginning balance, shares at Dec. 31, 2018				3,412,366
Exercise of stock options	69			$ 1	68
Exercise of stock options, shares				166,015
Stock based compensation	567				567
Vesting of Series B redeemable convertible preferred stock in lieu of rent			$ 948
Conversion of redeemable convertible preferred 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
Initial public offering of common stock, net of issuance costs	77,827			$ 5	77,822
Initial public offering of common stock, net of issuance costs, shares				5,073,800
Exercise of stock warrant	0
Exercise of stock warrant, shares				27,941
Other Comprehensive Income (Loss)	129					129
Net Loss	(14,743)						(14,743)
Ending balance at Jun. 30, 2019	136,217			$ 27	183,678	80	(47,568)
Ending balance, shares at Jun. 30, 2019		0	0
Ending balance, shares at Jun. 30, 2019				26,841,149
Beginning balance at Mar. 31, 2019	(38,027)			$ 4	498	(23)	(38,506)
Beginning balance, shares at Mar. 31, 2019		9,008,919	9,152,108
Beginning balance at Mar. 31, 2019		$ 17,178	$ 86,960
Beginning balance, shares at Mar. 31, 2019				3,566,923
Exercise of stock options	5				5
Exercise of stock options, shares				11,458
Stock based compensation	377				377
Vesting of Series B redeemable convertible preferred stock in lieu of rent			$ 856
Conversion of redeemable convertible preferred 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
Initial public offering of common stock, net of issuance costs	77,827			$ 5	77,822
Initial public offering of common stock, net of issuance costs, shares				5,073,800
Exercise of stock warrant, shares				27,941
Other Comprehensive Income (Loss)	103					103
Net Loss	(9,062)						(9,062)
Ending balance at Jun. 30, 2019	$ 136,217			$ 27	$ 183,678	$ 80	$ (47,568)
Ending balance, shares at Jun. 30, 2019		0	0
Ending balance, shares at Jun. 30, 2019				26,841,149

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net Loss	$ (14,743)	$ (6,485)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash interest expense related to convertible promissory notes		262
Non-cash rent expense	184
Stock based compensation	567	27
Depreciation and amortization	53	17
Accretion of discount on convertible promissory notes payable		694
Amortization of discount on available for sale investments	(395)
Change in fair value of derivative liability		206
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(4,515)	(265)
Other assets	(250)
Accounts payable	4,621	(147)
Accrued expenses and other current liabilities	947	(106)
Net cash used in operating activities	(13,531)	(5,797)
Cash flow from investing activities:
Purchase of investments	(88,593)
Proceeds from maturities of investments	43,940
Purchase of property and equipment	(20)	(14)
Net cash provided by investing activities	(44,673)	(14)
Cash flows from financing activities:
Proceeds from issuance of convertible promissory note payable		250
Proceeds from issuance of commons stock upon exercise of stock options	69
Proceeds from Series B redeemable convertible preferred stock		75,688
Proceeds from initial public offering, net of stock offering costs	77,827
Net cash provided by financing activities	77,896	75,938
Net increase / (decrease) in cash, cash equivalents and restricted cash	19,692	70,127
Cash, cash equivalents and restricted cash at beginning of period	24,872	7,393
Cash, cash equivalents and restricted cash at end of period	44,564	$ 77,520
Supplemental disclosures of non-cash information:
Right-of-use assets obtained in exchange for new operating lease liabilities	878
Right-of-use assets obtained in exchange for new finance lease liabilities	278
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
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
Acceleration of vesting of stock on initial public offering	$ 856

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and pursuant to the instructions of the SEC on Form 10-Q and Article 10 of Regulation S-X of the SEC. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the management’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the results of operations and cash flows for the periods presented have been included.

The condensed balance sheet as of June 30, 2019, the condensed statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018, the condensed statements of stockholders’ deficit as of June 30, 2019 and 2018, the condensed statements of cash flows for the six months ended June 30, 2019 and 2018, and the financial data and other financial information disclosed in the notes to the condensed financial statements are unaudited. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2018 included in the Company’s final prospectus (the “Prospectus”) filed with the SEC on May 9, 2019. The results of operations for the three and six months ended June 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019, or for any other future annual or interim period.

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 and 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.

Significant Accounting Policies

There have been no significant changes to the accounting policies during the six months ended June 30, 2019, as compared to the significant accounting policies described in the Prospectus, dated May 8, 2019 and filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the “Securities Act”).

Cash, Cash Equivalents, and Restricted Cash

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash and cash equivalents. Cash equivalents, which consist of amounts invested in money market funds, are stated at fair value. There are no unrealized gains or losses on the money market funds for the periods presented.

Restricted cash as of June 30, 2019 relates to a compensating balance to secure a credit card facility.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that sum to the total of the same amounts shown in the condensed statements of cash flows (in thousands):

	Six Months Ended June 30,
	2019		2018
Cash and cash equivalents	$	44,314	$	77,470
Restricted cash		250		50
Total cash, cash equivalents and restricted cash	$	44,564	$	77,520

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.

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. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period.

Leases

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update, or ASU, No. 2016-02, Leases (Topic 842), to enhance the transparency and comparability of financial reporting related to leasing arrangements. The Company adopted the standard effective January 1, 2019.

The Company determines if an arrangement includes a lease at inception. Right-of-use assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. The right-of-use asset includes any lease payments made and excludes lease incentives. Incremental borrowing rate is used in determining the present value of future payments. The Company utilizes its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. The lease terms may include options to extend or terminate the lease. Lease expense for minimum lease payments is recognized on a straight-line basis over the non-cancelable lease term. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840, Leases (Topic 840).

Emerging Growth Company Status

The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to not use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies.

Recent Accounting Pronouncements adopted

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 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 5 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 the ASU.

Recent accounting pronouncements not yet adopted

The following are new accounting pronouncements that the Company is evaluating for future impacts on its financial statements:

Fair Value Measurement—Disclosure Framework: 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 is evaluating the provisions of the updated guidance and assessing the impact on its financial statements.

Financial Instruments—Credit Losses: In June 2016, the FASB issued new guidance which amends the principles around the recognition of credit losses by mandating entities incorporate an estimate of current expected credit losses when determining the value of certain assets. The guidance also amends reporting around allowances for credit losses on available-for-sale marketable securities. This guidance is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company is evaluating the impact of adopting this amendment to its financial statements.

In August 2018, the FASB issued Accounting Standards Update No. 2018-15, Intangibles – Goodwill and other – Internal-Use Software (Subtopic 350-40), which amended its guidance for costs of implementing a cloud computing service arrangement and aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. This new standard also requires customers to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. The guidance is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company is evaluating the impact of adopting this amendment to its financial statements.

Fair Value Measurements

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 3. Fair Value Measurements

The Company measures and reports its cash equivalents, restricted cash, and investments at fair value.

Money market funds are measured at fair value on a recurring basis using quoted prices and are classified as Level 1. Investments are measured at fair value based on inputs other than quoted prices that are derived from observable market data and are classified as Level 2 inputs.

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 June 30, 2019 and December 31, 2018 are presented in the following tables (in thousands):

	Fair Value Measurements at June 30, 2019
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	16,248	$	—	$	—		$	16,248
Certificates of Deposit	Level 2		24,700		34		—			24,734
Repurchase Agreements	Level 2		12,000		—		—			12,000
Corporate notes	Level 2		10,888		3		(9	)		10,882
U.S. government notes	Level 2		61,065		51		—			61,116
Asset backed securities	Level 2		5,445		1		—			5,446
Total cash equivalents and investments		$	130,346	$	89	$	(9	)	$	130,426

Classified as:
Cash equivalents									$	38,464
Short-term investments										83,974
Long-term investments										7,988
Total cash equivalents and investments									$	130,426

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

Classified as:
Cash equivalents									$	13,613
Short-term investments										46,844
Total cash equivalents and investments									$	60,457

As of June 30, 2019, the remaining contractual maturities of available-for-sale securities was approximately five months. There have been no significant realized losses on available-for-sale securities for the period presented. Based on the Company’s review of its available-for-sale securities, the Company believes it had no other-than-temporary impairments on these securities as of June 30, 2019, because the Company does not intend to sell these securities nor does the Company believe that it will be required to sell these securities before the recovery of their amortized cost basis.

For the three and six months ended June 30, 2018, the Company realized $188,000 and $206,000 of expenses, respectively for a redemption premium feature accounted for as embedded derivative liability in accordance with ASC 815. 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. This liability was extinguished in May, 2018 with the Series B redeemable preferred stock financing.

There were no transfers between Levels 1, 2 or 3 for the period presented.

- 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

Balance Sheet Components

6 Months Ended

Jun. 30, 2019

Balance Sheet Components [Abstract]

Balance Sheet Components

Note 4. Balance Sheet Components

Prepaid expenses and Other Current Assets

Prepaid expenses and Other Current Assets consist of the following (in thousands):

	June 30,		December 31,
	2019		2018
Prepaid expenses	$	150	$	47
Prepaid Insurance		2,042		—
Prepaid clinical trial expenses		2,328		587
Prepaid drug manufacturing		58		—
Prepaid research and development expenses		81		166
Other assets		446		68
Total prepaid expenses and other current assets	$	5,105	$	868

Property and Equipment

Property and Equipment consist of the following (in thousands):

	June 30,			December 31,
	2019			2018
Lab Equipment	$	398		$	378
Less: accumulated depreciation		(133	)		(95	)
Property and equipment, net	$	265		$	283

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	June 30,		December 31,
	2019		2018
Personnel expenses	$	535	$	483
Professional fees		155		75
Clinical trial expenses		327		—
Drug manufacturing expenses		670		—
Research and development expenses		196		380
Other		26		24
Total accrued liabilities	$	1,909	$	962

Leases

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Leases

Note 5. 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.

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 June 30, 2019, future rent expense of $822,000 will be recognized over the remaining term of 25 months on a straight-line basis over the respective lease period. Rent expense for the operating lease for the three months and six months ended June 30, 2019 was $92,000 and $184,000 respectively.

Clinical Equipment Financing Lease

During the second quarter, the Company began using certain vendor supplied equipment in connection with its on-going clinical trial. The Company analyzed the agreement and determined that it contained an embedded lease. Under the agreements, the Company has prepaid for the use of the equipment through the leases term of approximately 2.5 years. As a result, the Company has no lease liability associated with these right of use assets. The Company recognizes the lease expense research and development expenses in the statement of operations and recognizes expense on a straight-line basis over the lease term of approximately 2.5 years. Amortization expense of the financing lease right of use asset for the three and six months ended June 30, 2019 was $15,000 and $15,000 respectively.

Operating and finance lease right of use asset amounts consist of the following:

Right of use assets- operating lease	$	823
Right of use assets- financing lease		278
Less: accumulated depreciation		(15	)
Total right of use assets	$	1,086

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 June 30, 2019, the weighted-average remaining lease term for the operating leases was 2.1 years. The weighted-average remaining lease term for the finance lease was 2.5 years.

Stock-Based Compensation

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 6. Stock-Based Compensation

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 June 30, 2019, the Company had 2,591,031 shares available for future issuance under the 2019 Plan.

For the three months and six months ended June 30, 2019, the Company recognized $377,000 and $567,000 of stock-based compensation expense, respectively 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.

	Number of Options and Unvested Shares			Weighted Average Exercise Price		Weighted average remaining contractual life (years)		Aggregate intrinsic value
Balance at December 31, 2018		1,885,504			1.57		9.07	$	1,252,496
Options granted		617,637			9.33		9.69
Options exercised		(166,015	)		0.41
Options cancelled		(66,180	)		2.23
Balance at June 30, 2019		2,270,946			3.74		9.20		81,680,409
Options vested and expected to vest as of June 30, 2019		2,270,946			3.74		9.20		81,680,409
Options exercisable as of June 30, 2019		446,367			1.06		7.99	$	18,500,177

The total unrecognized share-based compensation cost at June 30, 2019 amounted to approximately $4,852,000 which is expected to be recognized over the next four years.

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 least 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 administrator has not yet approved an offering under the 2019 ESPP.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Significant Accounting Policies

Cash, Cash Equivalents, and Restricted Cash

Restricted cash as of June 30, 2019 relates to a compensating balance to secure a credit card facility.

	Six Months Ended June 30,
	2019		2018
Cash and cash equivalents	$	44,314	$	77,470
Restricted cash		250		50
Total cash, cash equivalents and restricted cash	$	44,564	$	77,520

Fair Value Measurements

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;

Leases

Emerging Growth Company Status

Recently Accounting Pronouncements adopted and Recent accounting pronouncements not yet adopted

Recent Accounting Pronouncements adopted

Recent accounting pronouncements not yet adopted

The following are new accounting pronouncements that the Company is evaluating for future impacts on its financial statements:

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

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

	Fair Value Measurements at June 30, 2019
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	16,248	$	—	$	—		$	16,248
Certificates of Deposit	Level 2		24,700		34		—			24,734
Repurchase Agreements	Level 2		12,000		—		—			12,000
Corporate notes	Level 2		10,888		3		(9	)		10,882
U.S. government notes	Level 2		61,065		51		—			61,116
Asset backed securities	Level 2		5,445		1		—			5,446
Total cash equivalents and investments		$	130,346	$	89	$	(9	)	$	130,426

Classified as:
Cash equivalents									$	38,464
Short-term investments										83,974
Long-term investments										7,988
Total cash equivalents and investments									$	130,426

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

Classified as:
Cash equivalents									$	13,613
Short-term investments										46,844
Total cash equivalents and investments									$	60,457

Balance Sheet Components (Tables)

6 Months Ended

Jun. 30, 2019

Balance Sheet Components [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and Other Current Assets consist of the following (in thousands):

	June 30,		December 31,
	2019		2018
Prepaid expenses	$	150	$	47
Prepaid Insurance		2,042		—
Prepaid clinical trial expenses		2,328		587
Prepaid drug manufacturing		58		—
Prepaid research and development expenses		81		166
Other assets		446		68
Total prepaid expenses and other current assets	$	5,105	$	868

Schedule of Property and Equipment

Property and Equipment consist of the following (in thousands):

	June 30,			December 31,
	2019			2018
Lab Equipment	$	398		$	378
Less: accumulated depreciation		(133	)		(95	)
Property and equipment, net	$	265		$	283

Schedule of Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	June 30,		December 31,
	2019		2018
Personnel expenses	$	535	$	483
Professional fees		155		75
Clinical trial expenses		327		—
Drug manufacturing expenses		670		—
Research and development expenses		196		380
Other		26		24
Total accrued liabilities	$	1,909	$	962

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Options Activity

	Number of Options and Unvested Shares			Weighted Average Exercise Price		Weighted average remaining contractual life (years)		Aggregate intrinsic value
Balance at December 31, 2018		1,885,504			1.57		9.07	$	1,252,496
Options granted		617,637			9.33		9.69
Options exercised		(166,015	)		0.41
Options cancelled		(66,180	)		2.23
Balance at June 30, 2019		2,270,946			3.74		9.20		81,680,409
Options vested and expected to vest as of June 30, 2019		2,270,946			3.74		9.20		81,680,409
Options exercisable as of June 30, 2019		446,367			1.06		7.99	$	18,500,177

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands			6 Months Ended
	May 13, 2019 USD ($) $ / shares shares	Apr. 25, 2019	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
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 \| $			(47,568)	$ (32,825)
Cash, cash equivalents, and short-term investments \| $			$ 128,300
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
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

Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 130,346	$ 60,506
Unrealized Gains	89
Unrealized Losses	(9)	(49)
Fair Value	130,426	60,457
Cash equivalents	38,464	13,613
Short term investments	83,974	46,844
Long term investments	7,988
Total cash equivalents and investments	130,426	60,457
Money Market Funds \| Level 1
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,248	11,815
Fair Value	16,248	11,815
Certificates of Deposit \| Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	24,700
Unrealized Gains	34
Fair Value	24,734
Repurchase Agreements \| Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	12,000
Fair Value	12,000
Commercial paper \| Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		14,362
Unrealized Losses		(2)
Fair Value		14,360
Corporate Notes \| Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	10,888	16,129
Unrealized Gains	3
Unrealized Losses	(9)	(18)
Fair Value	10,882	16,111
U.S. government notes \| Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	61,065	8,980
Unrealized Gains	51
Unrealized Losses		(1)
Fair Value	61,116	8,979
Asset Backed Securities \| Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,445	9,220
Unrealized Gains	1
Unrealized Losses		(28)
Fair Value	$ 5,446	$ 9,192

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Personnel expenses	$ 535	$ 483
Professional fees	155	75
Clinical trial expenses	327
Drug manufacturing expenses	670
Research and development expenses	196	380
Other	26	24
Total accrued liabilities	$ 1,909	$ 962

Leases - Additional Information (Details)	1 Months Ended		3 Months Ended	6 Months Ended
Leases - Additional Information (Details)	May 31, 2019 USD ($)	Jun. 30, 2018 USD ($) ft² Investor shares	Jun. 30, 2019 USD ($) shares	Jun. 30, 2019 USD ($) shares	May 13, 2019	Dec. 31, 2018 shares	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				$ 822,000
Operating lease remaining term on a straight-line basis				25 months
Operating lease rent expense			$ 92,000	$ 184,000
Term of clinical equipment financing lease			2 years 6 months	2 years 6 months
Finance lease liability			$ 0	$ 0
Finance lease remaining term on a straight-line basis			2 years 6 months
Amortization expense of finance lease right-of-use asset			$ 15,000	$ 15,000
Operating lease discount rate percent			4.00%	4.00%
Operating lease discount rate term			2 years 1 month 6 days	2 years 1 month 6 days
Finance lease discount rate term			2 years 6 months	2 years 6 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	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%

Stock-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	May 07, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Income tax benefits recognized	$ 0
Unrecognized share-based compensation cost	4,852,000	$ 4,852,000
Unrecognized share-based compensation cost expected to be recognized, period		4 years
Employees and Non-Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense related to options granted	$ 377,000	$ 567,000
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	2,146,354
Percentage of common stock outstanding		4.00%
Common stock reserved for issuance	2,591,031	2,591,031
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	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-Based Compensation - Summary of Stock Option Activity (Details) - 2019 Plan	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options and Unvested Shares, beginning balance \| shares	1,885,504
Number of Options and Unvested Shares, granted \| shares	617,637
Number of Options and Unvested Shares, exercised \| shares	(166,015)
Number of Options and Unvested Shares, cancelled \| shares	(66,180)
Number of Options and Unvested Shares, ending balance \| shares	2,270,946	1,885,504
Number of Options and Unvested Shares, vested and expected to vest \| shares	2,270,946
Number of Options and Unvested Shares, exercisable \| shares	446,367
Weighted Average Exercise Price, beginning balance \| $ / shares	$ 1.57
Weighted Average Exercise Price, granted \| $ / shares	9.33
Weighted Average Exercise Price, exercised \| $ / shares	0.41
Weighted Average Exercise Price, cancelled \| $ / shares	2.23
Weighted Average Exercise Price, ending balance \| $ / shares	3.74	$ 1.57
Weighted Average Exercise Price, vested and expected to vest \| $ / shares	3.74
Weighted Average Exercise Price, exercisable \| $ / shares	$ 1.06
Weighted average remaining contractual life	9 years 2 months 12 days	9 years 25 days
Weighted average remaining contractual life, granted	9 years 8 months 8 days
Weighted average remaining contractual life, vested and expected to vest	9 years 2 months 12 days
Weighted average remaining contractual life, exercisable	7 years 11 months 26 days
Aggregate intrinsic value \| $	$ 81,680,409	$ 1,252,496
Aggregate intrinsic value, vested and expected to vest \| $	81,680,409
Aggregate intrinsic value, exercisable \| $	$ 18,500,177

Related Party Transactions - Additional Information (Detail)		1 Months Ended
	Jul. 16, 2018 ft² shares	May 31, 2019 USD ($) shares	Jun. 30, 2014 USD ($)	May 13, 2019	Jun. 30, 2018
Related Party Transaction [Line Items]
Percentage of royalties payment to stockholders in amount of gross revenues			3.00%
Lease agreement term	3 years
Operating lease payments paid for additional space \| $		$ 63,000
South San Francisco, California
Related Party Transaction [Line Items]
Area of lease office space \| ft²	3,185
Series B Redeemable Convertible Preferred Stock
Related Party Transaction [Line Items]
Lease agreement term					3 years
Restricted stock shares issued	114,437
Series B Redeemable Convertible Preferred Stock \| IPO
Related Party Transaction [Line Items]
Conversion of preferred stock into common stock		82,649
Conversion of redeemable convertible preferred stock to common stock ratio		100.00%		100.00%
Series B Redeemable Convertible Preferred Stock \| IPO \| Series B Redeemable Convertible Preferred Stock Investor
Related Party Transaction [Line Items]
Conversion of preferred stock into common stock		229,453
Maximum
Related Party Transaction [Line Items]
Payment of royalties to stockholders \| $			$ 1,050,000

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Right-of-use asset	$ 823,000		$ 823,000
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
Money Market Funds
Summary Of Significant Accounting Policies [Line Items]
Unrealized gains or loss	$ 0	$ 0	$ 0	$ 0

Income Taxes - Additional Information (Details)	6 Months Ended
Income Taxes - Additional Information (Details)	Jun. 30, 2019 USD ($)
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 0

Net Loss Per Share - Schedule of Outstanding Potentially Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount	2,270,946	18,954,227
Series A Redeemable 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 Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount		9,037,671
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of earnings per share, amount		27,941
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	2,270,946	879,696

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 44,314	$ 24,872	$ 77,470
Restricted cash	250		50
Total cash, cash equivalents and restricted cash	$ 44,564	$ 24,872	$ 77,520	$ 7,393

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Prepaid Expense And Other Assets Current [Abstract]
Prepaid expenses	$ 150	$ 47
Prepaid Insurance	2,042
Prepaid clinical trial expenses	2,328	587
Prepaid drug manufacturing	58
Prepaid research and development expenses	81	166
Other assets	446	68
Total prepaid expenses and other current assets	$ 5,105	$ 868

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Lab Equipment	$ 398	$ 378
Less: accumulated depreciation	(133)	(95)
Property and equipment, net	$ 265	$ 283

Leases - Summary of Operating Lease and Finance Lease Right of Use Assets (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Leases [Abstract]
Right-of-use asset	$ 823
Right of use assets- financing lease	278
Less: accumulated depreciation	(15)
Total right of use assets	$ 1,086