Checkmate Pharmaceuticals (CMPI) 10-Q 18 Sep 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2020	Sep. 18, 2020
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Entity Registrant Name	Checkmate Pharmaceuticals, Inc.
Entity Central Index Key	0001651431
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	No
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Incorporation, State or Country Code	DE
Entity Address, State or Province	DE
Entity Address, Country	MA
Title of 12(b) Security	Common Stock
Trading Symbol	CMPI
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		21,546,591

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 80,289	$ 4,185
Restricted cash	20	20
Prepaid expenses and other current assets	3,147	921
Total current assets	83,456	5,126
Total assets	83,456	5,126
Current Liabilities:
Accounts payable	3,249	2,234
Accrued expenses	3,736	3,100
Series B preferred stock tranche right liability		300
Total current liabilities	6,985	5,634
Total liabilities	6,985	5,634
Commitments and Contingencies (Note 10)
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	194,268	96,928
Stockholders' Deficit:
Common stock, $0.0001 par value; 146,000,000 and 76,000,000 shares authorized as of June 30, 2020 and December 31, 2019, respectively; 1,488,489 shares issued and outstanding as of June 30, 2020 and December 31, 2019;	1	1
Additional paid-in capital
Accumulated deficit	(117,798)	(97,437)
Total stockholders' deficit	(117,797)	(97,436)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	83,456	5,126
Series A Redeemable Convertible Preferred Stock [Member]
Current Liabilities:
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	33,479	32,482
Series B Redeemable Convertible Preferred Stock [Member]
Current Liabilities:
Series B preferred stock tranche right liability	300
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	75,314	$ 64,446
Series C Redeemable Convertible Preferred Stock [Member]
Current Liabilities:
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 85,475

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Temporary equity number of shares issued	108,096,207	51,283,386
Temporary equity number of shares outstanding	108,096,207	51,283,386
Temporary equity liquidation preference	$ 193,968	$ 96,928
Common stock par value per share	$ 0.0001	$ 0.0001
Common stock number of shares authorised	146,000,000	76,000,000
Common stock number of shares issued	1,488,489	1,488,489
Common stock number of shares outstanding	1,488,489	1,488,489
Series A Redeemable Convertible Preferred Stock [Member]
Temporary equity par value per share	$ 0.0001	$ 0.0001
Temporary equity number of shares authorised	25,000,000	25,000,000
Temporary equity number of shares issued	25,000,000	25,000,000
Temporary equity number of shares outstanding	25,000,000	25,000,000
Temporary equity liquidation preference	$ 33,479	$ 32,482
Series B Redeemable Convertible Preferred Stock [Member]
Temporary equity par value per share	$ 0.0001	$ 0.0001
Temporary equity number of shares authorised	29,972,284	29,972,284
Temporary equity number of shares issued	29,972,284	26,283,386
Temporary equity number of shares outstanding	29,972,284	26,283,386
Temporary equity liquidation preference	$ 75,014	$ 64,446
Series C Redeemable Convertible Preferred Stock [Member]
Temporary equity par value per share	$ 0.0001	$ 0.0001
Temporary equity number of shares authorised	62,489,557
Temporary equity number of shares issued	53,123,923
Temporary equity number of shares outstanding	53,123,923
Temporary equity liquidation preference	$ 85,475

Condensed Statements of Operati

Condensed Statements of Operations And Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 6,476	$ 5,849	$ 12,789	$ 12,049
General and administrative	1,795	1,107	3,305	2,157
Total operating expenses	8,271	6,956	16,094	14,206
Loss from operations	(8,271)	(6,956)	(16,094)	(14,206)
Other income (expense), net:
Interest income	6	59	28	116
Change in fair value of convertible loan notes	(83)		(83)
Total other income (expense), net	(77)	59	(55)	116
Net loss and comprehensive loss	(8,348)	(6,897)	(16,149)	(14,090)
Net loss	(8,348)	(6,897)	(16,149)	(14,090)
Accretion of issuance costs on redeemable convertible preferred stock	(429)	(33)	(456)	(51)
Accrued dividends on redeemable convertible preferred stock	(2,187)	(1,476)	(3,957)	(2,728)
Net loss attributable to common stockholders	$ (10,964)	$ (8,406)	$ (20,562)	$ (16,869)
Weighted-average common shares outstanding—basic and diluted	1,488,489	1,429,484	1,488,489	1,413,935
Net loss per share attributable to common stockholders—basic and diluted	$ (7.37)	$ (5.88)	$ (13.81)	$ (11.93)

Condensed Statements of Redeema

Condensed Statements of Redeemable Convertible Preferred Stock And Stockholders' Deficit - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Series A Redeemable Convertible Preferred Stock [Member]	Series A Redeemable Convertible Preferred Stock [Member]Preferred Stock [Member]	Series B Redeemable Convertible Preferred Stock [Member]	Series B Redeemable Convertible Preferred Stock [Member]Preferred Stock [Member]	Series C Redeemable Convertible Preferred Stock [Member]	Series C Redeemable Convertible Preferred Stock [Member]Preferred Stock [Member]
Beginning balance at Dec. 31, 2018							$ 30,482		$ 41,491
Beginning balance, shares at Dec. 31, 2018							25,000,000		17,522,259
Beginning balance at Dec. 31, 2018	$ (62,801)		$ 1		$ (62,802)
Beginning balance, shares at Dec. 31, 2018			1,394,961
Issuance of series redeemable convertible preferred, shares									5,072,232
Issuance of series redeemable convertible preferred									$ 10,949
Accretion of issuance costs related to redeemable convertible preferred stock	(51)				(51)				51
Exercise of stock options	74			$ 74
Exercise of stock options, shares			77,876
Exercise of series B preferred stock tranche right	0
Vesting of restricted stock awards, shares			10,276
Stock-based compensation expense	157			157
Accrued dividends on redeemable convertible preferred stock	(2,728)			(231)	(2,497)		$ 992		1,736
Net loss	(14,090)				(14,090)
Ending balance at Jun. 30, 2019							$ 31,474		$ 54,227
Ending balance, shares at Jun. 30, 2019							25,000,000		22,594,491
Ending balance at Jun. 30, 2019	(79,439)		$ 1		(79,440)
Ending balance, shares at Jun. 30, 2019			1,483,113
Beginning balance at Mar. 31, 2019							$ 30,975		$ 53,250
Beginning balance, shares at Mar. 31, 2019							25,000,000		22,594,491
Beginning balance at Mar. 31, 2019	(71,185)		$ 1		(71,186)
Beginning balance, shares at Mar. 31, 2019			1,400,099
Issuance of series redeemable convertible preferred									$ 33
Conversion of convertible loan notes into redeemable preferred stock									(33)
Accretion of issuance costs related to redeemable convertible preferred stock	(33)				(33)
Exercise of stock options	74			74
Exercise of stock options, shares			77,876
Vesting of restricted stock awards, shares			5,138
Stock-based compensation expense	78			78
Accrued dividends on redeemable convertible preferred stock	(1,476)			(152)	(1,324)		$ 499		977
Net loss	(6,897)				(6,897)
Ending balance at Jun. 30, 2019							$ 31,474		$ 54,227
Ending balance, shares at Jun. 30, 2019							25,000,000		22,594,491
Ending balance at Jun. 30, 2019	(79,439)		$ 1		(79,440)
Ending balance, shares at Jun. 30, 2019			1,483,113
Beginning balance at Dec. 31, 2019	$ 96,928					$ 32,482	$ 32,482	$ 64,446	$ 64,446
Beginning balance, shares at Dec. 31, 2019	51,283,386					25,000,000	25,000,000	26,283,386	26,283,386
Beginning balance at Dec. 31, 2019	$ (97,436)		$ 1		(97,437)
Beginning balance, shares at Dec. 31, 2019			1,488,489
Issuance of series redeemable convertible preferred, shares									3,688,898		46,828,167
Issuance of series redeemable convertible preferred									$ 7,973		$ 74,571
Conversion of convertible loan notes into redeemable preferred stock											$ 10,083
Conversion of convertible loan notes into redeemable preferred stock, shares											6,295,756
Accretion of issuance costs related to redeemable convertible preferred stock	$ (456)				(456)				27		$ 429
Exercise of stock options, shares	0
Exercise of series B preferred stock tranche right	$ 300								300
Stock-based compensation expense	201			201
Accrued dividends on redeemable convertible preferred stock	(3,957)			(201)	(3,756)		$ 997		2,568		392
Net loss	(16,149)				(16,149)
Ending balance at Jun. 30, 2020	$ 194,268					$ 33,479	$ 33,479	$ 75,314	$ 75,314	$ 85,475	$ 85,475
Ending balance, shares at Jun. 30, 2020	108,096,207	53,123,923				25,000,000	25,000,000	29,972,284	29,972,284	53,123,923	53,123,923
Ending balance at Jun. 30, 2020	$ (117,797)		$ 1		(117,798)
Ending balance, shares at Jun. 30, 2020			1,488,489
Beginning balance at Mar. 31, 2020							$ 32,980		$ 74,018
Beginning balance, shares at Mar. 31, 2020							25,000,000		29,972,284
Beginning balance at Mar. 31, 2020	(106,933)		$ 1		(106,934)
Beginning balance, shares at Mar. 31, 2020			1,488,489
Issuance of series redeemable convertible preferred, shares											46,828,167
Issuance of series redeemable convertible preferred											$ 74,571
Conversion of convertible loan notes into redeemable preferred stock											$ 10,083
Conversion of convertible loan notes into redeemable preferred stock, shares											6,295,756
Accretion of issuance costs related to redeemable convertible preferred stock	(429)				(429)						$ 429
Stock-based compensation expense	100			100
Accrued dividends on redeemable convertible preferred stock	(2,187)			$ (100)	(2,087)		$ 499		$ 1,296		392
Net loss	(8,348)				(8,348)
Ending balance at Jun. 30, 2020	$ 194,268					$ 33,479	$ 33,479	$ 75,314	$ 75,314	$ 85,475	$ 85,475
Ending balance, shares at Jun. 30, 2020	108,096,207	53,123,923				25,000,000	25,000,000	29,972,284	29,972,284	53,123,923	53,123,923
Ending balance at Jun. 30, 2020	$ (117,797)		$ 1		$ (117,798)
Ending balance, shares at Jun. 30, 2020			1,488,489

Condensed Statements of Redee_2

Condensed Statements of Redeemable Convertible Preferred Stock And Stockholders' Deficit (Parenthetical) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)$ / shares	Jun. 30, 2019USD ($)$ / shares
Cash paid for redeemable convertible preferred stock issuance	$ 398	$ 0
Series B Redeemable Convertible Preferred Stock [Member]
Shares Issued, Price Per Share | $ / shares	$ 2.1687	$ 2.1687
Cash paid for redeemable convertible preferred stock issuance	$ 27	$ 51
Series C Redeemable Convertible Preferred Stock [Member]
Shares Issued, Price Per Share | $ / shares	$ 1.6016
Cash paid for redeemable convertible preferred stock issuance	$ 429

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (16,149)	$ (14,090)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock based compensation	201	157
Change in fair value of notes payable	83	0
Change in operating assets and liabilities:
Prepaid expenses and other current assets	(610)	(207)
Accounts payable	(31)	(192)
Accrued expenses	464	(373)
Net cash used in operating activities	(16,042)	(14,705)
Cash flows from financing activities
Cash received from stock option exercise	0	74
Cash paid for initial public offering costs	(398)	0
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	82,544	10,949
Proceeds from issuance of convertible loan notes	10,000	0
Net cash provided by financing activities	92,146	11,023
Net increase (decrease) in cash, cash equivalents and restricted cash	76,104	(3,682)
Cash, cash equivalents and restricted cash at beginning of period	4,205	12,079
Cash, cash equivalents and restricted cash at end of period	80,309	8,397
Supplemental disclosure of non-cash financing activities:
Accretion of issuance costs to redeemable convertible preferred stock	456	51
Exercise of series B preferred stock tranche right	300	0
Accrued dividends on redeemable convertible preferred stock	3,957	2,728
Deferred offering costs included in prepaid expenses and other current assets and accounts payable or accrued expenses	1,217	0
Series C Redeemable Convertible Preferred Stock [Member]
Cash flows from financing activities
Cash paid for initial public offering costs	(429)
Supplemental disclosure of non-cash financing activities:
Conversion of convertible loan notes into series C preferred stock	$ 10,083	$ 0

Nature of Business And Basics o

Nature of Business And Basics of Presentation	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business And Basics of Presentation	1 – N ATURE OF USINESS AND ASIS OF RESENTATION Nature of Business Checkmate Pharmaceuticals, Inc., or Checkmate or the Company, headquartered non-clinical Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, and include the accounts of the Company. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. The Company’s significant accounting policies are disclosed in the audited financial statements for the year ended December 31, 2019, included in the Company’s registration statement on Form S-1 No. 333-239932) Initial Public Offering On August 11 closed at which time August 11, 2020 all convertible preferred stock converted into shares of common stock. Th e unaudited condensed financial statements, including share and per share amounts, do not give effect to the IPO or the related conversion of securities into shares of common stock. On September 3, 2020 the underwriters of the IPO exercised a portion of their overallotment option by purchasing an additional 109,861 shares from the Company at the IPO price, resulting in an additional $1.5 million in net proceeds after deducting the underwriting discounts and commissions. On July 31, 2020, the Company effected a one-for-7.4771 was unaudited Risks and Uncertainties The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, the outcome of clinical trials, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, ability to secure additional capital to fund operations, and risks associated with the COVID-19 its As of May 13, 2020, the issuance date of the Company’ s audited financial statements for the year ended December 31, 2019, the Company concluded that there was substantial doubt about its ability to continue as a going concern for one year after the date that those financial statements were issued. Subsequent to the issuance of those financial statements, the Company received net and unaudited condensed financial statements, the Company expects its cash and cash equivalents of $80.3 million as of June 30, 2020, together with the net unaudited condensed financial statements. The Company may seek additional funding through private or public equity financings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing agreements. If the Company is unable to obtain additional funding, the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. Unaudited interim financial information The accompanying interim unaudited condensed financial statements and related disclosures are unaudited and have been prepared in accordance with GAAP for interim financial information and the instructions to Form 10-Q S-X.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2 – S UMMARY OF IGNIFICANT CCOUNTING OLICIES The Company’s significant accounting policies are described in Note 3, Summary of Significant Accounting Policies December 31, 2019 in the Registration Statement. There six-month Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity additional paid-in capital. Fair Value Option As permitted under ASC 825, Financial Instruments, or ASC 825, the Company has elected the fair value option to account for its convertible loan notes. In accordance with ASC 825, the Company records these convertible loan notes at fair value with changes in fair value recorded as a component of other income (expense), net in the condensed statements non-contingent Recently adopted accounting pronouncements In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 2019-12. 2019-12 2019-12 In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 2018-18 In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. ASU No. 2018-13 ASU No. 2018-13 2018-13 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, or ASU 2017-11 . ASU 2017-11 2017-11 2017-11

Fair Value Measurement

Fair Value Measurement	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurement	3 – F AIR ALUE EASUREMENT The following tables set forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy that are measured at fair value on a recurring basis: June 30, 2020 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 80,045 $ — $ — $ 80,045 Total assets $ 80,045 $ — $ — $ 80,045 December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 4,003 $ — $ — $ 4,003 Total assets $ 4,003 $ — $ — $ 4,003 Liabilities: Series B preferred stock tranche right liability $ — $ — $ 300 $ 300 Total liabilities $ — $ — $ 300 $ 300 V ALUATION OF ERIES REFERRED TOCK RANCHE IGHT IABILITY The series B preferred stock tranche right liability at December 31, 2019 is composed of the fair value of rights to purchase series B redeemable convertible preferred stock, or Series B. The fair value of the series B preferred stock tranche right liability was determined based on significant inputs not observable in the market, which represent a Level 3 measurement within the fair value hierarchy. The fair value of the preferred stock tranche right liability was determined using a binomial model, which considered as inputs the value of the Series B, the expected return of the underlying Series B during the period between the valuation date and the expected event date, the probability and timing of achieving the specified milestones as of each valuation date and a discount rate. The most significant assumption in the binomial model impacting the fair value of the series B preferred stock tranche right liability is the fair value of the Company’s Series B as of each measurement date. The Company determines the fair value per share of the underlying Series B by taking into consideration the most recent sales of its Series B, results obtained from third-party valuations and additional factors the Company deems relevant. At December 31, 2019, the fair value of each share of Series B was $2.20 per share. The series B preferred stock tranche right was exercised on January 14, 2020. The change in fair value of the series B preferred stock tranche right liability from December 31, 2019 to January 14, 2020 was not material. The following table provides a roll-forward of the aggregate fair value of the Company’s series B preferred stock tranche right liability, for which fair value is determined using Level 3 inputs: Series B Preferred (in thousands) Balance as of December 31, 2019 $ 300 Exercise of series B preferred stock tranche right (300 ) Balance as of June 30, 2020 $ — VALUATION OF CONVERTIBLE LOAN NOTES The Company elected the fair value option to account for its convertible loan notes issued during April 2020. The fair value of the convertible loan notes was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of the initial closing of the Company’s convertible loan notes in April 2020 was determined to be equal to the proceeds of $10.0 million on issuance. The fair value of the convertible loan at the time of conversion into the Series C preferred stock in June 2020 was determined to be equal to $1.6016 per share, the value of the Company’s Series C preferred stock into which the convertible loan notes were converted . The change in fair value of the convertible notes prior to close of the Series C preferred stock financing of $0.1 million primarily related to the accrued interest earned on the convertible loan notes prior to such financing . The following table presents a roll-forward of the aggregate fair values of the Company’s convertible loan notes (Note 5) for which fair value is determined by Level 3 inputs: Convertible Loan (in thousands) Balance as of December 31, 2019 Initial fair value $ 10,000 Change in fair value plus accrued interest 83 Settlement of convertible loan note s (10,083 ) Balance as of June 30, 2020 $ —

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2020
Payables and Accruals [Abstract]
Accrued Expenses	4 – A CCRUED XPENSES Accrued expenses consist of the following: June 30, December 31, 2020 2019 (in thousands) Payroll and employee related expenses $ 837 $ 1,051 External research and development 2,572 1,969 Other accrued expenses 327 80 Total accrued expenses $ 3,736 $ 3,100

Convertible Loan Notes

Convertible Loan Notes	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Convertible Loan Notes	5 – C ONVERTIBLE OAN OTES On April 21, 2020, the Company entered into a note purchase agreement pursuant to which the Company issued unsecured convertible loan notes to investors for a total of $10.0 million in principal. The Company will pay simple interest on the outstanding principal amount to the extent not converted at the rate of 8% per annum. No repayment of principal or interest was due until maturity, which occurs 12 months after issuance of the convertible loan notes. Under the agreement, the convertible loan notes outstanding principal and unpaid accrued interest automatically convert upon a Qualified Financing. If the Qualified Financing is consummated within (i) three months after the date of the agreement, the conversion price shall be equal to 90% of the per share price paid by the investors; (ii) if consummated more than three months after the date of the agreement, but within six months, the conversion price shall be equal to 80% of the per share price paid by the investors; and (iii) is consummated more than six months after the date of the agreement, the conversion price shall be equal to 70% of the price per share paid by the investors. On June 2, 2020, upon the series C preferred stock financing (Note 6), the outstanding principal and unpaid accrued interest of the convertible notes of $10.1 million converted into 6,295,756 shares of series C preferred stock. Upon execution of the series C preferred stock, the noteholder investors waived their right to the 90% conversion price and converted the notes at 100% of the per share price paid by the investors in the Qualified Financing. The Company elected the fair value option to account for the convertible loan notes. The Company recorded the convertible loan notes at fair value and subsequently remeasured them to fair value upon settlement of the convertible loan notes. Changes in fair value were recognized as a component of other income (expense), net in the condensed statements of operations and comprehensive loss. The Company recognized a loss in the condensed statements of operations and comprehensive loss of $0.1 million as change in fair value of the convertible notes during the three and six months ended June 30, 2020.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	6 Months Ended
	Jun. 30, 2020
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	6 – R EDEEMABLE ONVERTIBLE REFERRED TOCK As of each balance sheet date, the Preferred Stock consisted of the following: June 30, 2020 Issued and Carrying Liquidation Common (dollars in thousands) Series A 25,000,000 $ 33,479 $ 33,479 3,343,542 Series B 29,972,284 75,314 75,014 4,499,824 Series C 53,123,923 85,475 85,475 7,104,883 108,096,207 $ 194,268 $ 193,968 14,948,249 December 31, 2019 Issued and Carrying Liquidation Common (dollars in thousands) Series A 25,000,000 $ 32,482 $ 32,482 3,343,542 Series B 26,283,386 64,446 64,446 3,946,001 51,283,386 $ 96,928 $ 96,928 7,289,543 Preferred stock is classified outside of stockholders’ deficit because the shares contain redemption features that are not solely within the control of the Company. Series C Preferred Stock Financing In June 2020, the Company entered into the Series C Preferred Stock Purchase Agreement, or the Series C Agreement, pursuant to which the Company was authorized to issue 62,489,557 shares of Series C convertible preferred stock (Series C), at a price of $1.6016 per share. As part of the closing, the Company issued 46,828,167 shares of Series C at $1.6016 per share for consideration of $75.0 million and an additional 6,295,756 shares of Series C in satisfaction of the conversion of $10.0 million convertible loan notes and $0.1 million of accrued interest. The aggregate purchase price of the Series C was $85.1 million and the Company incurred issuance costs of $0.4 million, which was recorded as a reduction to the Series C carrying value. Series B Preferred Stock Financing In January 2020, the Company issued 3,688,898 of Series B at a price of $2.16867 per share, resulting in net proceeds received of $8.0 million. The rights and preferences of the Series B issued in January 2020 are identical to Series B issued in prior periods. As a result of the issuance, the fair value of the associated outstanding series B tranche right liability of $0.3 million was reclassified to Series B. In connection with the Series C financing, the conversion price of the Series B was decreased from $16.21536 to $14.4451 such that the rate at which shares of Series B may be converted into shares of common stock was adjusted from 1:1 to 0.15013:1. Dividends Preferred stock accrues dividends on a cumulative basis at $0.08 per share per annum for Series A, $0.17349 per share per annum for Series B and $0.128128 per share per annum for Series C, to be calculated daily and is payable when and if declared by the Company’s board of directors . No dividends may be paid to common stockholders until all dividends to preferred stockholders are paid in full, except stock dividends paid to common stockholders. Cumulative dividends were as follows: June 30, December 31, 2020 2019 (in thousands) Series A $ 8,479 $ 7,482 Series B $ 10,014 $ 7,446 Series C $ 392 $ — Through June 30, 2020, no dividends have been declared or paid by the Company.

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Common Stock	7 – C OMMON TOCK The voting, dividend and liquidation rights of the common stockholders are subject to and qualified by the rights, powers and preferences of the preferred stock. The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders. Common stockholders are entitled to receive dividends declared out of funds legally available, subject to the payment in full of all preferential dividends to which the holders of preferred stock are entitled. In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, after the payment or provision for payment of all debts and liabilities of the Company and all preferential amounts to which the holders of preferred stock are entitled, if any, the common stockholders and preferred stockholders (on an as-converted The Company’s common stock available for future issuance as of June 30, 2020 is summarized as follows: Common stock authorized 146,000,000 Common stock authorized, issued and outstanding 1,488,489 Common stock authorized and reserved for future issuance: Common stock reserved for the conversion of Series A 3,343,542 Common stock reserved for the conversion of Series B 4,499,824 Common stock reserved for the conversion of Series C 7,104,883 Common stock reserved for future exercises of stock option awards 1,073,044 Common stock reserved for future share-based 729,575 Total common stock authorized and reserved for future issuance 18,239,357 Unreserved common stock available for future issuance 127,760,643

Stock based compensation

Stock based compensation	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock based compensation	8 – S TOCK ASED OMPENSATION Stock Options In August 2015, the Company’s board of directors approved the Checkmate Pharmaceuticals, Inc. 2015 Stock Option and Grant Plan, or 2015 Plan, to encourage and enable the officers, employees, directors, consultants 2015 d non-statutory board of directors shares of 2015 was were The Company estimates the fair value of stock option awards on the grant date using the Black-Scholes option valuation model with the following weighted-average assumptions: Three and Six Months Ended June 30, 2020 2019 Risk-free interest rate N/A 1.30 % Expected term (in years) N/A 5.75 Expected volatility N/A 70.0 % Dividend yield N/A — There were no stock options granted during the three and six months ended June 30, 2020. The per share weighted average grant date fair value of stock options granted during the three and six months ended June 30, 2019 was $1.61. As of June 30, 2020, total unrecognized compensation expense related to stock options totaled $0.95 million, which is expected to be recognized over a weighted average period of 2.6 years. The following table summarizes the activity under the Company’s stock option plan during the six months ended June 30, 2020: Number of Options Weighted- Average Exercise Price Weighted- Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2019 1,073,044 $ 2.45 8.7 $ 906 Granted — $ — Forfeited — $ — Exercised — $ — Outstanding at June 30, 2020 1,073,044 $ 2.45 8.2 $ 906 Vested and expected to vest at June 30, 2020 1,073,044 $ 2.45 8.2 $ 906 Exercisable at June 30, 2020 426,980 $ 2.23 7.6 $ 468 The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. There were no options exercised during the six months ended June 30, 2020. Restricted Stock The Company did not grant restricted stock during the six months ended June 30, 2020. All previously granted restricted stock was fully vested as of December 31, 2019. Stock-based Compensation Expense Total stock-based compensation expense was classified in the accompanying condensed statements of operations and comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 ( in thousands) (in thousands) Research and development $ 39 $ 25 $ 78 $ 49 General and administrative 61 53 123 108 Total stock-based compensation expense $ 100 $ 78 $ 201 $ 157

Income taxes

Income taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income taxes	9 – I NCOME AXES The Company incurred federal and state net operating losses and recorded a full valuation allowance against net deferred assets for all periods presented. Accordingly, the Company has not recorded a provision for federal or state income taxes. The Coronavirus Aid, Relief, and Economic Security Act, or CARES Act, signed into United States law on March 27, 2020 modifies certain provisions of the Tax Cuts and Jobs Act, or TCJA with respect to net operating losses. Under the CARES Act, the limitation on the deduction of net operating losses to 80% of annual taxable income is removed for taxable years beginning before January 1, 2021. The CARES Act did not have a material impact on the unaudited condensed financial statements.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share	10 – N ET OSS ER HARE Net Loss Per Share Attributable To Common Stockholders Because the Company reports a net loss attributable to common stockholders, basic and diluted net loss per share attributable to common stockholders are the same for both years presented. All preferred stock, unvested restricted stock, and stock options have been excluded from the computation of diluted weighted-average shares outstanding because such securities would have an antidilutive impact. Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 (in thousands, except share (in thousands, except share Numerator Net loss $ (8,348 ) $ (6,897 ) $ (16,149 ) $ (14,090 ) Accretion of issuance costs on redeemable convertible preferred stock (429 ) (33 ) (456 ) (51 ) Accrued dividends on redeemable convertible preferred stock (2,187 ) (1,476 ) (3,957 ) (2,728 ) Net Loss attributable to common stockholders $ (10,964 ) $ (8,406 ) $ (20,562 ) $ (16,869 ) Denominator: Weighted-average common shares outstanding—basic and diluted 1,488,489 1,429,484 1,488,489 1,413,935 Net loss per share attributable to common stockholders—basic and diluted $ (7.37 ) $ (5.88 ) $ (13.81 ) $ (11.93 ) The following common stock equivalents outstanding at June 30, 2020 and 2019 have been excluded from the calculation of diluted net loss per share because their inclusion would have been antidilutive: June 30, 2020 2019 Options to purchase common stock 1,073,044 812,539 Unvested restricted common stock — 5,376 Redeemable convertible preferred stock 14,948,249 6,365,368

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	11 – C OMMITMENTS AND ONTINGENCIES Operating Lease The Company has a month-to-month months ended June 30, 2020 and 2019 was $0.1 million and $0.1 million, respectively. Rent expense for the , Clinical Trial Collaboration and Supply Agreement On August 22, 2018, the Company entered into the Clinical Trial Collaboration and Supply Agreement, or CTCSA Agreement, with an affiliate of Merck KgaA, or Merck, and Pfizer Inc., or Pfizer, (Merck and Pfizer together are referred to herein as the “Alliance”). Pursuant to the CTCSA, the Company, and the Alliance will each provide compound drug product that will be dosed concurrently or in combination in a clinical trial sponsored by Pfizer. This agreement was amended on March 4, 2019. In addition to providing a compound drug product to be used in the clinical trial, the Company will reimburse Pfizer for each patient dosed in the study using the Company’s compound at a specified rate outlined in the CTCSA Agreement. In no event will the amount of costs due by the Company to Pfizer exceed $4.0 million over the term of the CTCSA Agreement. The costs of services performed and material used in connection with the research and development activities of the CTCSA Agreement, including reimbursements due to Pfizer, are included in research and development costs and expensed as incurred. The Company incurred $0.5 million and $0.1 million of expense during the three and six months ended June 30, 2020, respectively, and no expense relating to the Pfizer reimbursement during the three and six months ended June 30, 2019. License Agreement In June 2015, the Company entered into an exclusive license agreement with Cytos Biotechnology LTD (now Kuros Biosciences AG or Kuros) as amended in August 2017 and as further amended in January 2018 (the Kuros License Agreement). Pursuant to the Kuros License Agreement, in return for payments made, the Company was granted an exclusive, royalty-bearing, sublicensable, worldwide license, under all of Kuros’s intellectual property rights, including any intellectual property rights arising during the term of the agreement, to commercially develop, manufacture, use, distribute, and sell certain therapeutic products, including CMP-001, CMP-001 CMP-001. As of June 30, 20 20 Other Contingencies During the ordinary course of its operations, the Company may become a party to contractual disputes, litigation, and potential claims. The Company does not believe that the resolution of any of these matters, if any, will have a material adverse effect on its financial position or results of operations.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	12 – S UBSEQUENT VENTS In August 2020 , Company’s board of directors and stockholders adopted and approved Plan, or the 2020 Plan. non-employee directors consultants 2020 % Plan In August 2020 , the b d the Checkmate Pharmaceuticals, Inc. 2020 Employee Stock Purchase Plan, or 2020 ESPP . The 2020 ESPP was created to provide eligible employees of the Company and other qualified participants to purchase the Company’s common stock at 85% of the fair market value of the common stock on the offering date or the exercise date, whichever is for up to 15% of such employee’s compensation for each pay period. The Company reserved 267,119 shares of common stock for the 2020 ESPP. The 2020 ESPP provides for an annual increase in the number of shares of common stock to be reserved for future issuance under the 2020 ESPP .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Nature of Business	Nature of Business Checkmate Pharmaceuticals, Inc., or Checkmate or the Company, headquartered non-clinical
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, and include the accounts of the Company. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. The Company’s significant accounting policies are disclosed in the audited financial statements for the year ended December 31, 2019, included in the Company’s registration statement on Form S-1 No. 333-239932)
Initial Public Offering	Initial Public Offering On August 11 closed at which time August 11, 2020 all convertible preferred stock converted into shares of common stock. Th e unaudited condensed financial statements, including share and per share amounts, do not give effect to the IPO or the related conversion of securities into shares of common stock. On September 3, 2020 the underwriters of the IPO exercised a portion of their overallotment option by purchasing an additional 109,861 shares from the Company at the IPO price, resulting in an additional $1.5 million in net proceeds after deducting the underwriting discounts and commissions. On July 31, 2020, the Company effected a one-for-7.4771 was unaudited
Risks and Uncertainties	Risks and Uncertainties The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, the outcome of clinical trials, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, ability to secure additional capital to fund operations, and risks associated with the COVID-19 its As of May 13, 2020, the issuance date of the Company’ s audited financial statements for the year ended December 31, 2019, the Company concluded that there was substantial doubt about its ability to continue as a going concern for one year after the date that those financial statements were issued. Subsequent to the issuance of those financial statements, the Company received net and unaudited condensed financial statements, the Company expects its cash and cash equivalents of $80.3 million as of June 30, 2020, together with the net unaudited condensed financial statements. The Company may seek additional funding through private or public equity financings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing agreements. If the Company is unable to obtain additional funding, the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.
Unaudited interim financial information	Unaudited interim financial information The accompanying interim unaudited condensed financial statements and related disclosures are unaudited and have been prepared in accordance with GAAP for interim financial information and the instructions to Form 10-Q S-X.
Deferred offering costs	Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity additional paid-in capital.
Fair Value Option	Fair Value Option As permitted under ASC 825, Financial Instruments, or ASC 825, the Company has elected the fair value option to account for its convertible loan notes. In accordance with ASC 825, the Company records these convertible loan notes at fair value with changes in fair value recorded as a component of other income (expense), net in the condensed statements non-contingent
Recently adopted accounting pronouncements	Recently adopted accounting pronouncements In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 2019-12. 2019-12 2019-12 In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 2018-18 In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. ASU No. 2018-13 ASU No. 2018-13 2018-13 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, or ASU 2017-11 . ASU 2017-11 2017-11 2017-11

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis	June 30, 2020 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 80,045 $ — $ — $ 80,045 Total assets $ 80,045 $ — $ — $ 80,045 December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 4,003 $ — $ — $ 4,003 Total assets $ 4,003 $ — $ — $ 4,003 Liabilities: Series B preferred stock tranche right liability $ — $ — $ 300 $ 300 Total liabilities $ — $ — $ 300 $ 300
Schedule of Aggregate Fair Value of The Company's Series B Preferred Stock Tranche Right Liability	The following table provides a roll-forward of the aggregate fair value of the Company’s series B preferred stock tranche right liability, for which fair value is determined using Level 3 inputs: Series B Preferred (in thousands) Balance as of December 31, 2019 $ 300 Exercise of series B preferred stock tranche right (300 ) Balance as of June 30, 2020 $ —
Schedule of Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following table presents a roll-forward of the aggregate fair values of the Company’s convertible loan notes (Note 5) for which fair value is determined by Level 3 inputs: Convertible Loan (in thousands) Balance as of December 31, 2019 Initial fair value $ 10,000 Change in fair value plus accrued interest 83 Settlement of convertible loan note s (10,083 ) Balance as of June 30, 2020 $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2020
Payables and Accruals [Abstract]
Accrued Expenses	Accrued expenses consist of the following: June 30, December 31, 2020 2019 (in thousands) Payroll and employee related expenses $ 837 $ 1,051 External research and development 2,572 1,969 Other accrued expenses 327 80 Total accrued expenses $ 3,736 $ 3,100

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	6 Months Ended
	Jun. 30, 2020
Temporary Equity Disclosure [Abstract]
Schedule of Redeemable Convertible Preferred Stock	As of each balance sheet date, the Preferred Stock consisted of the following: June 30, 2020 Issued and Carrying Liquidation Common (dollars in thousands) Series A 25,000,000 $ 33,479 $ 33,479 3,343,542 Series B 29,972,284 75,314 75,014 4,499,824 Series C 53,123,923 85,475 85,475 7,104,883 108,096,207 $ 194,268 $ 193,968 14,948,249 December 31, 2019 Issued and Carrying Liquidation Common (dollars in thousands) Series A 25,000,000 $ 32,482 $ 32,482 3,343,542 Series B 26,283,386 64,446 64,446 3,946,001 51,283,386 $ 96,928 $ 96,928 7,289,543
Schedule of Cumulative Dividends	Cumulative dividends were as follows: June 30, December 31, 2020 2019 (in thousands) Series A $ 8,479 $ 7,482 Series B $ 10,014 $ 7,446 Series C $ 392 $ —

Common Stock (Tables)

Common Stock (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Summary of Common Stock Available for Future Issuance	The Company’s common stock available for future issuance as of June 30, 2020 is summarized as follows: Common stock authorized 146,000,000 Common stock authorized, issued and outstanding 1,488,489 Common stock authorized and reserved for future issuance: Common stock reserved for the conversion of Series A 3,343,542 Common stock reserved for the conversion of Series B 4,499,824 Common stock reserved for the conversion of Series C 7,104,883 Common stock reserved for future exercises of stock option awards 1,073,044 Common stock reserved for future share-based 729,575 Total common stock authorized and reserved for future issuance 18,239,357 Unreserved common stock available for future issuance 127,760,643

Stock based compensation - (Ta

Stock based compensation - (Tables)	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of fair value of stock option awards on the grant date using the black-scholes option valuation model	The Company estimates the fair value of stock option awards on the grant date using the Black-Scholes option valuation model with the following weighted-average assumptions: Three and Six Months Ended June 30, 2020 2019 Risk-free interest rate N/A 1.30 % Expected term (in years) N/A 5.75 Expected volatility N/A 70.0 % Dividend yield N/A —
Summary of activity under the company's stock option plan	The following table summarizes the activity under the Company’s stock option plan during the six months ended June 30, 2020: Number of Options Weighted- Average Exercise Price Weighted- Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2019 1,073,044 $ 2.45 8.7 $ 906 Granted — $ — Forfeited — $ — Exercised — $ — Outstanding at June 30, 2020 1,073,044 $ 2.45 8.2 $ 906 Vested and expected to vest at June 30, 2020 1,073,044 $ 2.45 8.2 $ 906 Exercisable at June 30, 2020 426,980 $ 2.23 7.6 $ 468
Summary of total stock-based compensation expense	Total stock-based compensation expense was classified in the accompanying condensed statements of operations and comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 ( in thousands) (in thousands) Research and development $ 39 $ 25 $ 78 $ 49 General and administrative 61 53 123 108 Total stock-based compensation expense $ 100 $ 78 $ 201 $ 157

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Summary of Basic And Diluted Net Loss Per Share Attributable To Common Stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 (in thousands, except share (in thousands, except share Numerator Net loss $ (8,348 ) $ (6,897 ) $ (16,149 ) $ (14,090 ) Accretion of issuance costs on redeemable convertible preferred stock (429 ) (33 ) (456 ) (51 ) Accrued dividends on redeemable convertible preferred stock (2,187 ) (1,476 ) (3,957 ) (2,728 ) Net Loss attributable to common stockholders $ (10,964 ) $ (8,406 ) $ (20,562 ) $ (16,869 ) Denominator: Weighted-average common shares outstanding—basic and diluted 1,488,489 1,429,484 1,488,489 1,413,935 Net loss per share attributable to common stockholders—basic and diluted $ (7.37 ) $ (5.88 ) $ (13.81 ) $ (11.93 )
Summary of Potentially Dilutive Shares Excluded From The Calculation of Diluted Net Loss	The following common stock equivalents outstanding at June 30, 2020 and 2019 have been excluded from the calculation of diluted net loss per share because their inclusion would have been antidilutive: June 30, 2020 2019 Options to purchase common stock 1,073,046 812,539 Unvested restricted common stock — 5,376 Redeemable convertible preferred stock 14,948,249 6,365,368

Nature of Business And Basics_2

Nature of Business And Basics of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands	Sep. 03, 2020USD ($)shares	Aug. 31, 2020USD ($)	Aug. 11, 2020USD ($)$ / sharesshares	Jul. 31, 2020	Jun. 30, 2020USD ($)$ / shares	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs					$ 82,544	$ 10,949
Cash and cash equivalents					$ 80,289		$ 4,185
Series C Redeemable Convertible Preferred Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Shares Issued, Price Per Share | $ / shares					$ 1.6016
Proceeds from initial public offering gross					$ 75,000
Common Stock [Member] | Subsequent Event [Member]
Subsidiary, Sale of Stock [Line Items]
Reverse stock split, conversion ratio				7.4771
Description of the reverse stock split arrangement				On July 31, 2020, the Company effected a one-for-7.4771 reverse stock split of its common stock. Upon the effectiveness of the reverse stock split, (i) all shares of outstanding common stock were adjusted; (ii) the number of shares of common stock for which each outstanding option to purchase common stock is exercisable were adjusted; and (iii) the exercise price of each outstanding option to purchase common stock were adjusted. All of the outstanding common stock share numbers (including shares of common stock subject to the Company's options and as converted for the outstanding convertible preferred stock shares), share prices, exercise prices and per share amounts contained in the interim unaudited condensed financial statements have been retroactively adjusted in the interim condensed financial statements to reflect this reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock were not adjusted as a result of the reverse stock split. The reverse stock split resulted in an adjustment to the redeemable convertible preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion.
Proceeds from initial public offering			$ 67,000
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		$ 68,500
IPO [Member] | Common Stock [Member] | Subsequent Event [Member]
Subsidiary, Sale of Stock [Line Items]
Shares Issued During Period | shares			5,000,000
Shares Issued, Price Per Share | $ / shares			$ 15
Over-Allotment Option [Member] | Common Stock [Member] | Subsequent Event [Member]
Subsidiary, Sale of Stock [Line Items]
Shares Issued During Period | shares	109,861
Sale of stock consideration received on the transaction	$ 1,500

Fair Value Measurement - Schedu

Fair Value Measurement - Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Assets, Fair Value Disclosure	$ 80,045	$ 4,003
Liabilities:
Financial Liabilities Fair Value Disclosure		300
Money Market Funds [Member]
Assets:
Assets, Fair Value Disclosure	80,045	4,003
Series B Preferred Stock Tranche Right Liability [Member]
Liabilities:
Financial Liabilities Fair Value Disclosure		300
Fair Value, Inputs, Level 1 [Member]
Assets:
Assets, Fair Value Disclosure	80,045	4,003
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets:
Assets, Fair Value Disclosure	$ 80,045	4,003
Fair Value, Inputs, Level 3 [Member]
Liabilities:
Financial Liabilities Fair Value Disclosure		300
Fair Value, Inputs, Level 3 [Member] | Series B Preferred Stock Tranche Right Liability [Member]
Liabilities:
Financial Liabilities Fair Value Disclosure		$ 300

Fair Value Measurement - Sche_2

Fair Value Measurement - Schedule of Aggregate Fair Value of The Company's Series B Preferred Stock Tranche Right Liability (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Schedule Of Aggregate fair value of the Companys series B preferred stock tranche right liability [Line Items]
Balance as of December 31, 2019	$ 300
Exercise of series B preferred stock tranche right	300	$ 0
Series B Redeemable Convertible Preferred Stock [Member]
Schedule Of Aggregate fair value of the Companys series B preferred stock tranche right liability [Line Items]
Balance as of June 30, 2020	300
Series B Redeemable Convertible Preferred Stock [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule Of Aggregate fair value of the Companys series B preferred stock tranche right liability [Line Items]
Balance as of December 31, 2019	300
Exercise of series B preferred stock tranche right	(300)
Balance as of June 30, 2020	$ 0

Fair Value Measurement - Sche_3

Fair Value Measurement - Schedule of Fair Value, Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Initial fair value	$ 10,000	$ 0
Convertible Notes Payable [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Initial fair value	10,000
Change in fair value plus accrued interest	83
Settlement of convertible loan notes	(10,083)
Ending balance	$ 0

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Apr. 01, 2020
Fair Value Disclosures [Line Items]
Proceeds from convertible loan notes			$ 10,000	$ 0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Disclosures [Line Items]
Proceeds from convertible loan notes		$ 10,000
Series B Redeemable Convertible Preferred Stock [Member]
Fair Value Disclosures [Line Items]
Fair value per share			$ 2.20
Exercise date of preferred stock tranche right	Jan. 14, 2020
Series C Redeemable Convertible Preferred Stock [Member]
Fair Value Disclosures [Line Items]
Debt instrument conversion price					$ 1.6016
Series C Redeemable Convertible Preferred Stock [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Disclosures [Line Items]
Change in fair value of convertible notes			$ 100

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Payroll and employee related expenses	$ 837	$ 1,051
External research and development	2,572	1,969
Other accrued expenses	327	80
Total accrued expenses	$ 3,736	$ 3,100

Convertible Loan Notes - Additi

Convertible Loan Notes - Additional Information (Detail) - USD ($) $ in Millions	Jun. 02, 2020	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2020	Apr. 30, 2020	Apr. 21, 2020
Convertible Notes Payable [Member]
Disclosure of Convertible Loan Notes [Line Items]
Debt Face Amount						$ 10
Debt Instrument Interest Rate					8.00%
Convertible Notes Payable [Member] | Fair Value, Inputs, Level 3 [Member]
Disclosure of Convertible Loan Notes [Line Items]
Gain loss on change in fair value of convertible notes			$ 0.1	$ 0.1
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage One [Member]
Disclosure of Convertible Loan Notes [Line Items]
Debt instrument conversion price as a percentage of share price		90.00%	90.00%	90.00%
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage One [Member] | Qualified Financing Period One [Member] | Maximum [Member]
Disclosure of Convertible Loan Notes [Line Items]
Term of qualified financing from the date of agreement for conversion price eligibility		3 months
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage Two [Member]
Disclosure of Convertible Loan Notes [Line Items]
Debt instrument conversion price as a percentage of share price		80.00%	80.00%	80.00%
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage Two [Member] | Qualified Financing Period Two [Member] | Maximum [Member]
Disclosure of Convertible Loan Notes [Line Items]
Term of qualified financing from the date of agreement for conversion price eligibility		6 months
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage Two [Member] | Qualified Financing Period Two [Member] | Minimum [Member]
Disclosure of Convertible Loan Notes [Line Items]
Term of qualified financing from the date of agreement for conversion price eligibility		3 months
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage Three [Member]
Disclosure of Convertible Loan Notes [Line Items]
Debt instrument conversion price as a percentage of share price		70.00%	70.00%	70.00%
Convertible Notes Payable [Member] | Debt Instrument Conversion Price Percentage Three [Member] | Qualified Financing Period Three [Member]
Disclosure of Convertible Loan Notes [Line Items]
Term of qualified financing from the date of agreement for conversion price eligibility		6 months
Series C Redeemable Convertible Preferred Stock [Member]
Disclosure of Convertible Loan Notes [Line Items]
Debt conversion, shares issued				6,295,756
Series C Redeemable Convertible Preferred Stock [Member] | Convertible Notes Payable [Member]
Disclosure of Convertible Loan Notes [Line Items]
Debt Instrument benenficial conversion feature	$ 10.1
Conversion price as a percentage of share price waived	90.00%
Conversion price as a percentage of share price into which the debt instrument is converted	100.00%

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock - Schedule of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Temporary equity number of shares issued	108,096,207	51,283,386
Temporary equity number of shares outstanding	108,096,207	51,283,386
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 194,268	$ 96,928
Temporary equity liquidation preference	$ 193,968	$ 96,928
Common stock issuable upon conversion	14,948,249	7,289,543
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity number of shares issued	25,000,000	25,000,000
Temporary equity number of shares outstanding	25,000,000	25,000,000
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 33,479	$ 32,482
Temporary equity liquidation preference	$ 33,479	$ 32,482
Common stock issuable upon conversion	3,343,542	3,343,542
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity number of shares issued	29,972,284	26,283,386
Temporary equity number of shares outstanding	29,972,284	26,283,386
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 75,314	$ 64,446
Temporary equity liquidation preference	$ 75,014	$ 64,446
Common stock issuable upon conversion	4,499,824	3,946,001
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity number of shares issued	53,123,923
Temporary equity number of shares outstanding	53,123,923
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 85,475
Temporary equity liquidation preference	$ 85,475
Common stock issuable upon conversion	7,104,883

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock - Schedule of Cumulative Dividends (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock amount of cumulative dividend	$ 8,479	$ 7,482
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock amount of cumulative dividend	10,014	$ 7,446
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock amount of cumulative dividend	$ 392

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Stock - Additional Information (Detail)	1 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares	Jan. 31, 2020$ / sharesshares	Jun. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)shares
Temporary Equity [Line Items]
Gross Proceeds from temporary equity			$ 82,544,000	$ 10,949,000
Preferred stock tranche right liability current					$ 300,000
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock per share amount of cumulative dividend | $ / shares			$ 0.08
Preferred stock dividend declared			$ 0
Temporary equity shares authorised | shares	25,000,000		25,000,000		25,000,000
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity issue price per share | $ / shares		$ 2.16867
Net proceeds from temporary equity	$ 8,000,000
Preferred stock per share amount of cumulative dividend | $ / shares			$ 0.17349
Preferred stock dividend declared			$ 0
Preferred stock tranche right liability current	$ 300,000		$ 300,000
Temporary equity shares authorised | shares	29,972,284		29,972,284		29,972,284
Temporary equity shares issued during the period | shares		3,688,898
Series B Redeemable Convertible Preferred Stock [Member] | Conversion Ratio One [Member]
Temporary Equity [Line Items]
Conversion ratio of redeemable covertible preferred stock into common stock	1		1
Series B Redeemable Convertible Preferred Stock [Member] | Conversion Ratio Two [Member]
Temporary Equity [Line Items]
Conversion ratio of redeemable covertible preferred stock into common stock	0.15013		0.15013
Series B Redeemable Convertible Preferred Stock [Member] | Conversion Price One [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock conversion price | $ / shares	$ 16.21536		$ 16.21536
Series B Redeemable Convertible Preferred Stock [Member] | Conversion Price Two [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock conversion price | $ / shares	14.4451		14.4451
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity issue price per share | $ / shares	$ 1.6016		1.6016
Preferred stock per share amount of cumulative dividend | $ / shares			$ 0.128128
Preferred stock dividend declared			$ 0
Temporary equity shares authorised | shares	62,489,557		62,489,557
Series C Redeemable Convertible Preferred Stock [Member] | Series C Preferred Stock Purchase Agreement [Member]
Temporary Equity [Line Items]
Temporary equity issue price per share | $ / shares	$ 1.6016		$ 1.6016
Gross Proceeds from temporary equity			$ 75,000,000
Temporary equity shares authorised | shares	62,489,557		62,489,557
Temporary equity shares issued during the period | shares	46,828,167
Temporary equity unamortised stock issuance costs	$ 400,000		$ 400,000
Series C Redeemable Convertible Preferred Stock [Member] | Series C Preferred Stock Purchase Agreement [Member] | Convertible Notes Payable [Member] | Unsecured Debt [Member]
Temporary Equity [Line Items]
Temporary equity shares issued during the period | shares			6,295,756
Debt instrument converted value In excess of principal			$ 100,000
Debt conversion original debt amount	10,000,000
Temporary equity shares issued during the period	$ 85,100,000

Common Stock - Summary of Commo

Common Stock - Summary of Common Stock Available for Future Issuance (Detail) - shares	Jun. 30, 2020	Dec. 31, 2019
Disclosure of Common Stock Summary of Outstanding and Reserved for Future Issuance [Line Items]
Common stock authorized	146,000,000	76,000,000
Common stock issued	1,488,489	1,488,489
Common stock outstanding	1,488,489	1,488,489
Common stock authorized and reserved for future issuance	14,948,249	7,289,543
Total common stock authorized and reserved for future issuance	18,239,357
Unreserved common stock available for future issuance	127,760,643
Employee Stock Option [Member]
Disclosure of Common Stock Summary of Outstanding and Reserved for Future Issuance [Line Items]
Common stock authorized and reserved for future issuance	1,073,044
Share-based Payment Arrangement [Member]
Disclosure of Common Stock Summary of Outstanding and Reserved for Future Issuance [Line Items]
Common stock authorized and reserved for future issuance	729,575
Series A Redeemable Convertible Preferred Stock [Member]
Disclosure of Common Stock Summary of Outstanding and Reserved for Future Issuance [Line Items]
Common stock authorized and reserved for future issuance	3,343,542	3,343,542
Series B Redeemable Convertible Preferred Stock [Member]
Disclosure of Common Stock Summary of Outstanding and Reserved for Future Issuance [Line Items]
Common stock authorized and reserved for future issuance	4,499,824	3,946,001
Series C Redeemable Convertible Preferred Stock [Member]
Disclosure of Common Stock Summary of Outstanding and Reserved for Future Issuance [Line Items]
Common stock authorized and reserved for future issuance	7,104,883

Stock based compensation - Sche

Stock based compensation - Schedule of fair value of stock option awards on the grant date using the Black-Scholes option valuation model (Detail)	6 Months Ended
	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.30%
Expected term (in years)	5 years 9 months
Expected volatility	70.00%
Dividend yield	0.00%

Stock based compensation - Summ

Stock based compensation - Summary the activity under the Company's stock option plan (Detail) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Share-based Payment Arrangement [Abstract]
Outstanding Number, Beginning balance | shares	1,073,044
Outstanding Number, Granted | shares	0
Outstanding Number, Forfeited | shares	0
Outstanding Number ,Exercised | shares	0
Outstanding Number , Ending balance | shares	1,073,044	1,073,044
Outstanding Number, Vested and expected to vest | shares	1,073,044
Outstanding Number, Exercisable | shares	426,980
Weighted Average Exercise price, Beginning balance | $ / shares	$ 2.45
Weighted Average Exercise price, Granted | $ / shares	0
Weighted Average Exercise price, Forfeited | $ / shares	0
Weighted Average Exercise price, Exercised | $ / shares	0
Weighted Average Exercise price, Ending balance | $ / shares	2.45	$ 2.45
Weighted Average Exercise price, Vested and expected to vest | $ / shares	2.45
Weighted Average Exercise price, Exercisable | $ / shares	$ 2.23
Weighted-Average Remaining Contractual Term	8 years 2 months 12 days	8 years 8 months 12 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	8 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Exercisable	7 years 7 months 6 days
Aggregate Intrinsic Value | $	$ 906	$ 906
Aggregate Intrinsic Value, Vested and expected to vest | $	906	$ 906
Aggregate Intrinsic Value, Exercisable | $	$ 468

Stock based compensation - Su_2

Stock based compensation - Summary of total stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 100	$ 78	$ 201	$ 157
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	39	25	78	49
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 61	$ 53	$ 123	$ 108

Stock based compensation - Add

Stock based compensation - Additional information (Detail) - USD ($)	Aug. 31, 2015	Jun. 30, 2020	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised			0
Stock options granted gross			0
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU's granted			0
RSU's vested			0
Two Thousand And Fifteen Stock Option And Grant Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards, vesting period	4 years
Share-based Payment Award, Number of Shares Available for Issuance		729,575	729,575
Unrecognized compensation expense related to stock option		$ 0.95	$ 0.95
Unrecognized compensation expense expected to be recognized, Weighted average period			2 years 7 months 6 days
Options exercised			0
Stock options granted gross		0	0
Weighted average grant date fair value of stock options granted, fair value		$ 1.61	$ 1.61
Two Thousand And Fifteen Stock Option And Grant Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Number of Shares Authorized for Issuance	2,025,764

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2020
Taxable Years Beginning After January 2021 [Member]
Income Tax Disclosure [Line Items]
Percentage of net operating losses eligible for deduction	80.00%

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Basic And Diluted Net Loss Per Share Attributable To Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net loss	$ (8,348)	$ (6,897)	$ (16,149)	$ (14,090)
Accretion of issuance costs related to redeemable convertible preferred stock	(429)	(33)	(456)	(51)
Accrued dividends on redeemable convertible preferred stock	(2,187)	(1,476)	(3,957)	(2,728)
Net loss attributable to common stockholders	$ (10,964)	$ (8,406)	$ (20,562)	$ (16,869)
Weighted-average common shares outstanding—basic and diluted	1,488,489	1,429,484	1,488,489	1,413,935
Net loss per share attributable to common stockholders—basic and diluted	$ (7.37)	$ (5.88)	$ (13.81)	$ (11.93)

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of Potentially Dilutive Shares Excluded From The Calculation of Diluted Net Loss (Detail) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,073,044	812,539
Unvested restricted common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		5,376
Redeemable convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	14,948,249	6,365,368

Commitments And Contingencies -

Commitments And Contingencies - Additional information (Detail) - USD ($) $ in Thousands	Mar. 04, 2019	Jun. 30, 2015	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2016	Jun. 30, 2015
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised			$ 6,476	$ 5,849	$ 12,789	$ 12,049
Operating lease rental expenses			100	$ 100	300	$ 200
CTSA Agreement [Member] | Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
CTCSA agreement, commitment amount	$ 4,000
Research and development costs and expenses Incurred			500		100
Kuros Agreement commitment amount	$ 4,000
CTSA Agreement [Member] | Research and Development Arrangement [Member] | Pfizer [Member]
Long-term Purchase Commitment [Line Items]
Research and development costs and expenses Incurred			$ 0		0
Kuros License Agreement [Member]
Long-term Purchase Commitment [Line Items]
CTCSA agreement, commitment amount		$ 56,000
Kuros Agreement commitment amount		56,000
Milestone Payments Paid									$ 2,300
Kuros License Agreement [Member] | Phase one Trail [Member]
Long-term Purchase Commitment [Line Items]
CTCSA agreement, commitment amount		2,000
Kuros Agreement commitment amount		2,000
Kuros License Agreement [Member] | Phase Two Trial [Member]
Long-term Purchase Commitment [Line Items]
CTCSA agreement, commitment amount		4,000
Kuros Agreement commitment amount		$ 4,000
Kuros License Agreement [Member] | License [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised									$ 1,000
Kuros License Agreement [Member] | Technology Service [Member] | Phase one Trail [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised								$ 1,000
Kuros License Second Amendment Agreement [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised					$ 0
Kuros License Second Amendment Agreement [Member] | License [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised							$ 300

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - shares	Jan. 01, 2021	Aug. 31, 2020	Jun. 30, 2020	Dec. 31, 2019	Aug. 31, 2015
Shares of common stock reserved for issuance under 2015 plan			14,948,249	7,289,543
2015 Stock Option and Grant Plan [Member]
Share-based Payment Award, Number of Shares Available for Issuance			729,575
Maximum [Member] | 2015 Stock Option and Grant Plan [Member]
Share-based Payment Award, Number of Shares Authorized for Issuance					2,025,764
Subsequent Event [Member] | 2020 Stock Option and Grant Plan [Member]
Share-based Payment Award, Number of Shares Available for Issuance		3,205,430
Share-based Payment Award, Percentage of Outstanding Stock Maximum	4.00%
Subsequent Event [Member] | 2015 Stock Option and Grant Plan [Member]
Share-based Payment Award, Number of Shares Available for Issuance		729,575
Subsequent Event [Member] | 2020 Employee Stock Purchase Plan [Member]
Discount on purchase		85.00%
Shares of common stock reserved for issuance under 2015 plan		267,119
Subsequent Event [Member] | Maximum [Member] | 2020 Stock Option and Grant Plan [Member]
Share-based Payment Award, Number of Shares Authorized for Issuance		3,935,005
Subsequent Event [Member] | Maximum [Member] | 2020 Employee Stock Purchase Plan [Member]
Discount on purchase		15.00%