Checkmate Pharmaceuticals (CMPI) 10-Q 12 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 11, 2021
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
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	Yes
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	MA
Title of 12(b) Security	Common Stock
Trading Symbol	CMPI
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		21,625,891
Entity File Number	001-39425
Entity Address, Address Line One	245 Main Street
Entity Address, Address Line Two	2nd Floor
Entity Address, City or Town	Cambridge
Entity Address, Postal Zip Code	02142
Entity Tax Identification Number	36-4813934
City Area Code	617
Local Phone Number	682-3625

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 63,110	$ 43,055
Restricted cash	20	20
Short-term investments	22,240	51,831
Prepaid expenses and other current assets	5,704	7,195
Total current assets	91,074	102,101
Investments, non-current	10,240	30,973
Machinery and equipment, net	367
Total assets	101,681	133,074
Current Liabilities:
Accounts payable	2,198	2,297
Accrued expenses	4,504	5,578
Total current liabilities	6,702	7,875
Total liabilities	6,702	7,875
Commitments and Contingencies (Note 9)
Stockholders' Equity (Deficit):
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of June 30, 2021 and December 31, 2020; no shares outstanding as of June 30, 2021 and December 31, 2020
Common stock, $0.0001 par value; 300,000,000 authorized as of June 30, 2021 and December 31, 2020; 21,625,891 and 21,560,398 shares issued and outstanding as of June 30, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	268,179	265,342
Accumulated other comprehensive gain (loss)	(33)	(74)
Accumulated deficit	(173,169)	(140,071)
Total stockholders' equity	94,979	125,199
Total liabilities and stockholders' equity	$ 101,681	$ 133,074

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Common stock par value per share	$ 0.0001	$ 0.0001
Common stock number of shares authorised	300,000,000	300,000,000
Common stock number of shares issued	21,625,891	21,560,398
Common stock number of shares outstanding	21,625,891	21,560,398
Preferred stock par value per share	$ 0.0001	$ 0.0001
Preferred stock number of shares authorised	10,000,000	10,000,000
Preferred stock number of shares outstanding	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations And Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development	$ 14,865	$ 6,476	$ 25,243	$ 12,789
General and administrative	4,090	1,795	7,893	3,305
Total operating expenses	18,955	8,271	33,136	16,094
Loss from operations	(18,955)	(8,271)	(33,136)	(16,094)
Other income (expense), net:
Interest income	20	6	73	28
Loss on sale of available-for-sale investments	(35)		(35)
Change in fair value of convertible loan notes		(83)		(83)
Total other income (expense), net	(15)	(77)	38	(55)
Net loss	(18,970)	(8,348)	(33,098)	(16,149)
Net loss	(18,970)	(8,348)	(33,098)	(16,149)
Accretion of issuance costs on redeemable convertible preferred stock		(429)		(456)
Accrued dividends on redeemable convertible preferred stock		(2,187)		(3,957)
Net loss attributable to common stockholders	$ (18,970)	$ (10,964)	$ (33,098)	$ (20,562)
Weighted-average common shares outstanding—basic and diluted	21,624,568	1,488,489	21,603,563	1,488,489
Net loss per share attributable to common stockholders—basic and diluted	$ (0.88)	$ (7.37)	$ (1.53)	$ (13.81)
Comprehensive loss:
Net loss	$ (18,970)	$ (8,348)	$ (33,098)	$ (16,149)
Unrealized gain on available-for-sale investments	50		41
Comprehensive loss	$ (18,920)	$ (8,348)	$ (33,057)	$ (16,149)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock And Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Gain/(Loss) [Member]	Series A Redeemable Convertible Preferred Stock [Member]Preferred Stock [Member]	Series B Redeemable Convertible Preferred Stock [Member]Preferred Stock [Member]	Series C Redeemable Convertible Preferred Stock [Member]Preferred Stock [Member]
Beginning balance at Dec. 31, 2019						$ 32,482	$ 64,446
Beginning balance, shares at Dec. 31, 2019						25,000,000	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 stock, net of issuance costs, shares							3,688,898
Issuance of series redeemable convertible preferred stock, net of issuance costs							$ 7,973
Exercise of series B preferred stock tranche right							300
Accretion of issuance costs related to redeemable convertible preferred stock	(27)			(27)			27
Stock-based compensation expense	101		$ 101
Accrued dividends on redeemable convertible preferred stock	(1,770)		(101)	(1,669)		$ 498	1,272
Net loss	(7,801)			(7,801)
Ending balance at Mar. 31, 2020						$ 32,980	$ 74,018
Ending balance, shares at Mar. 31, 2020						25,000,000	29,972,284
Ending balance at Mar. 31, 2020	(106,933)	$ 1		(106,934)
Ending balance, shares at Mar. 31, 2020		1,488,489
Beginning balance at Dec. 31, 2019						$ 32,482	$ 64,446
Beginning balance, shares at Dec. 31, 2019						25,000,000	26,283,386
Beginning balance at Dec. 31, 2019	(97,436)	$ 1		(97,437)
Beginning balance, shares at Dec. 31, 2019		1,488,489
Exercise of series B preferred stock tranche right	300
Accrued dividends on redeemable convertible preferred stock	(3,957)
Net loss	(16,149)
Ending balance at Jun. 30, 2020						$ 33,479	$ 75,314	$ 85,475
Ending balance, shares at Jun. 30, 2020						25,000,000	29,972,284	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 stock, net of issuance costs, shares								46,828,167
Issuance of series redeemable convertible preferred stock, net of issuance costs								$ 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						$ 33,479	$ 75,314	$ 85,475
Ending balance, shares at Jun. 30, 2020						25,000,000	29,972,284	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 Dec. 31, 2020	125,199	$ 2	265,342	(140,071)	$ (74)
Beginning balance, shares at Dec. 31, 2020		21,560,398
Exercise of stock options	118		118
Exercise of stock options, shares		59,225
Stock-based compensation expense	1,216		1,216
Unrealized gains (losses) on available-for-sale investments	(9)				(9)
Net loss	(14,128)			(14,128)
Ending balance at Mar. 31, 2021	112,396	$ 2	266,676	(154,199)	(83)
Ending balance, shares at Mar. 31, 2021		21,619,623
Beginning balance at Dec. 31, 2020	125,199	$ 2	265,342	(140,071)	(74)
Beginning balance, shares at Dec. 31, 2020		21,560,398
Unrealized gains (losses) on available-for-sale investments	41
Net loss	(33,098)
Ending balance at Jun. 30, 2021	94,979	$ 2	268,179	(173,169)	(33)
Ending balance, shares at Jun. 30, 2021		21,625,891
Beginning balance at Mar. 31, 2021	112,396	$ 2	266,676	(154,199)	(83)
Beginning balance, shares at Mar. 31, 2021		21,619,623
Exercise of stock options	16		16
Exercise of stock options, shares		6,268
Stock-based compensation expense	1,487		1,487
Unrealized gains (losses) on available-for-sale investments	50				50
Net loss	(18,970)			(18,970)
Ending balance at Jun. 30, 2021	$ 94,979	$ 2	$ 268,179	$ (173,169)	$ (33)
Ending balance, shares at Jun. 30, 2021		21,625,891

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock And Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2020USD ($)$ / shares	Mar. 31, 2020USD ($)$ / shares
Series B Redeemable Convertible Preferred Stock [Member]
Shares Issued, Price Per Share | $ / shares		$ 2.1687
Cash paid for redeemable convertible preferred stock issuance | $		$ 27
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 Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net loss	$ (8,348)	$ (33,098)	$ (16,149)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock based compensation		2,703	201
Depreciation		11
Change in fair value of notes payable	83		83
Amortization/accretion of investments		370
Change in operating assets and liabilities:
Prepaid expenses and other current assets		1,491	(610)
Accounts payable		(98)	(31)
Accrued expenses		(1,075)	464
Net cash used in operating activities		(29,696)	(16,042)
Cash flows from investing activities
Purchases of investments		(10,197)
Maturities of investments		29,500
Sale of investments		30,692
Purchase of machinery and equipment		(378)
Net cash provided by investing activities		49,617
Cash flows from financing activities
Proceeds from stock option exercises		134
Cash paid for initial public offering costs			(398)
Proceeds from issuance of convertible preferred stock, net of issuance costs			82,544
Proceeds from issuance of convertible loan notes			10,000
Net cash provided by financing activities		134	92,146
Net increase in cash, cash equivalents and restricted cash		20,055	76,104
Cash, cash equivalents and restricted cash at beginning of period		43,075	4,205
Cash, cash equivalents and restricted cash at end of period	80,309	$ 63,130	80,309
Supplemental disclosure of non-cash financing activities:
Accretion of issuance costs related to redeemable convertible preferred stock			456
Exercise of Series B preferred stock tranche right			300
Accrued dividends on redeemable convertible preferred stock	$ 2,187		3,957
Conversion of loan notes into series C preferred stock			10,083
Deferred offering costs included in prepaid expenses and other current assets and accounts payable or accrued expenses			$ 1,217

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	1 – N ATURE OF USINESS Nature of Business Checkmate Pharmaceuticals e non-clinical Initial Public Offering On August 11, 2020, the Company closed its initial public offering (“IPO”), at which time the Company issued and sold 5,000,000 shares of its common stock, at a price to the public of $15.00 per share. 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. The Company received approximately $67.7 million in net proceeds, inclusive of the over-allotment exercise and after deducting underwriting discounts and commissions and other offering expenses payable by the Compan y In On July 31, 2020, the Company effected a one-for-7.4771 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 therapeutics and 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 ongoing COVID-19 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 may 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 will The Company expects that its cash, cash equivalents and available-for-sale million as of June 30, 2021 will be sufficient to fund its operating expenses and capital requirements for at least 12 months beyond the date of issuance of these condensed consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
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 2, Summary of Significant Accounting Policies 10-K. six-month Basis of Presentation The accompanying condensed consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiary Checkmate Pharmaceuticals Security Corporation. Any reference in these notes to applicable guidance is meant to refer to the authoritative accounting principles generally accepted in the United States as found in the Accounting Standard Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). Unaudited interim financial information The accompanying interim condensed consolidated 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 10-K. Use of estimates The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses and the valuation of stock-based awards before the Company’s IPO. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions. Machinery and equipment Machinery and equipment is recorded at cost less accumulated depreciation. Depreciation is recognized using the straight-line method over the estimated useful life of five years for each asset. Accumulated depreciation at June 30, 2021 was $11,000. Recently issued accounting pronouncement In June 2016, the FASB issued ASU 2016-13, 2016-13 No. 2019-05, No. 2019-11 No. 2016-13,

Investments And Fair Value Meas

Investments And Fair Value Measurement	6 Months Ended
	Jun. 30, 2021
Investments, Fair Value Disclosure [Abstract]
Investments And Fair Value Measurement	3 – I NVESTMENTS AND AIR ALUE EASUREMENT T available-for-sale As of June 30, 2021 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term Investments, non-current (in thousands) Commercial paper $ 2,991 $ — $ — $ 2,991 $ 2,991 $ — Corporate debt securities 29,522 — (33 ) 29,489 19,249 10,240 Total $ 32,513 $ — $ (33 ) $ 32,480 $ 22,240 $ 10,240 As of December 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term Investments, non-current (in thousands) Commercial paper $ 42,709 $ 8 $ (16 ) $ 42,701 $ 42,701 $ — Corporate debt securities 41,169 — (66 ) 41,103 10,130 30,973 Total $ 83,878 $ 8 $ (82 ) $ 83,804 $ 52,831 $ 30,973 The amortized cost and estimated fair value of investments by contractual maturity at June 30, 2021 are as follows: Estimated Amortized Fair Cost Value (in thousands) Due in one year or less $ 22,258 $ 22,240 Due after one year through two years 10,255 10,240 $ 32,513 $ 32,480 At June 30, 2021 , were no available-for-sale o available-for-sale 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, 2021 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money markets funds (included in cash equivalents) $ 61,907 $ — $ — $ 61,907 Commercial paper — 2,991 — 2,991 Corporate debt securities — 29,489 — 29,489 Total assets $ 61,907 $ 32,480 $ — $ 94,387 December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money markets funds (included in cash equivalents) $ 7,839 $ — $ — $ 7,839 Commercial paper — 42,701 — 42,701 Corporate debt securities — 41,103 — 41,103 Total assets $ 7,839 $ 83,804 $ — $ 91,643 Investments classified as Level 2 within the valuation hierarchy consist of commercial paper and corporate debt securities. The Company estimates the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Accrued Expenses	4 – A CCRUED XPENSES Accrued expenses consist of the following: June 30, December 31, 2021 2020 (in thousands) Payroll and employee related expenses $ 1,677 $ 1,555 External research and development 2,077 3,633 Other accrued expenses 750 390 Total accrued expenses $ 4,504 $ 5,578

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	6 Months Ended
	Jun. 30, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	5 – R EDEEMABLE ONVERTIBLE REFERRED TOCK On August 11, 2020, in connection with the closing of the IPO, all outstanding shares of the Company’s preferred stock were converted into 14,948,241 shares of common stock. As a r e paid-in-capital

Equity

Equity	6 Months Ended
	Jun. 30, 2021
Stockholders' Equity Note [Abstract]
Equity	6 – E QUITY 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. On August 11, 2020, the Company fil e Also on August 11, 2020, the Company completed its IPO, pursuant to which it issued and sold 5,109,861 shares of common stock, inclusive of 109,861 shares sold by the Company pursuant to the full exercise of the underwriters’ option to purchase additional shares. The aggregate net proceeds received by the Company from the IPO were $67.7 million, after deducting underwriting discounts and commissions and other offering costs

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	7 – S TOCK ASED OMPENSATION Total stock-based compensation expense was classified in the accompanying condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) (in thousands) Research and development $ 608 $ 39 $ 1,094 $ 78 General and administrative 879 61 1,609 123 Total stock-based compensation expense $ 1,487 $ 100 $ 2,703 $ 201 During the six months ended June 30, 2021, the Company granted options with service-based vesting conditions for the purchase of 862,350 shares of common stock with a weighted average exercise price of $12.70 per share and a weighted average grant-date fair value of $8.85 per share.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	8 – 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 and stock options have been excluded from the computation of diluted weighted-average shares outstanding because such securities would have an antidilutive impact. The following common stock equivalents outstanding at June 30, 2021 and 2020 have been excluded from the calculation of diluted net loss per share because their inclusion would have been antidilutive: June 30, 2021 2020 Options to purchase common stock 3,284,323 1,073,044 Redeemable convertible preferred stock — 14,948,249

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	9 – C OMMITMENTS AND ONTINGENCIES Operating Lease The Company has a month-to-month Clinical Trial Collaboration and Supply Agreements On May 10, 2021, the Company entered into a Supply and Non-Exclusive anti-PD-1 anti-PD-1 and anti-PD-1 non-exclusive On December 7, 2020, the Company entered into the Master Clinical Trial Collaboration Agreement (“MCTCA”) with Bristol-Myers Squibb Company (“BMS”). The MCTCA dictates the general terms that govern specific collaborative studies between the companies, including the Company’s Phase 2 refractory melanoma study and Phase 2 front-line melanoma study (collectively, the “collaborative studies”). Pursuant to the MCTCA, BMS agreed to provide nivolumab, a drug to be used in combination with vidutolimod in the collaborative studies, at its own expense. As part of the MCTCA, the parties granted each other non-exclusive On August 22, 2018, the Company entered into the Clinical Trial Collaboration and Supply Agreement (“CTCSA”) with an affiliate of Merck KGaA (“Merck”) and Pfizer Inc. (“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. In no event will the amount of costs due by the Company to Pfizer exceed $4.0 million over the term of the CTCSA. The costs of services performed, and material used in connection with the research and development activities of the CTCSA, including reimbursements due to Pfizer, are included in research and development costs and expensed as incurred. The Company incurred $1.0 million and $0.5 million of expense during the years ended December 31, 2020 and 2019, respectively. By mutual agreement of the Company and the Alliance, the clinical trial was discontinued in 2020, and the Company does not expect to incur any further costs in connection with the CTCS A. 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 Kuro’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 vidutolimod, (the “Licensed Products”) for the diagnosis, treatment and prevention of all indications in humans and animals. Under the terms of the Kuros License Agreement, the Company is required to use commercially reasonable efforts to develop at least one Licensed Product. Under the Kuros License Agreement, the Company agreed to make payments to Kuros for each product that achieves certain development and regulatory milestones, including payments of up to $56.0 million for the Company’s current oncology programs. As of June 30, 2021, the Company has incurred license fees and milestone payments totaling $8.3 million pursuant to the Kuros License Agreement. These payments are comprised of: (i) a license fee of $1.0 million which was recognized in research and development expense in 2015, (ii) a $1.0 million milestone payment in connection with the dosing of the first patient in our first Phase 1 clinical trial, which was recognized in research and development expense in 2016, (iii) a $0.3 million license amendment fee in connection with the signing of the second amendment to the Kuros License Agreement, which was recognized in research and development expense in 2018, (iv) a $2.0 million milestone payment in connection with the dosing of the first patient in the Phase 2 first-line melanoma trial for vidutolimod, which was recognized in the statement of operations for the three months ended March 31, 2021 and (v) a $4.0 million milestone payment in connection with the dosing in a Phase 2 trial intended to assess the efficacy and safety of vidutolimod in combination with nivolumab for the treatment of patients with anti-PD-1 The Company is also required to pay tiered royalties of high single-digit to low teens percentages on annual net sales of Licensed Products that are covered by a licensed patent, as well as royalties at 50% of the foregoing amounts with respect to sales of Licensed Products that are not covered by a licensed patent, but are covered by licensed know-how. the last-to-expire royalty days’ written notice to Kuros. 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 .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiary Checkmate Pharmaceuticals Security Corporation. Any reference in these notes to applicable guidance is meant to refer to the authoritative accounting principles generally accepted in the United States as found in the Accounting Standard Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB).
Unaudited interim financial information	Unaudited interim financial information The accompanying interim condensed consolidated 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 10-K.
Use of Estimates	Use of estimates The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses and the valuation of stock-based awards before the Company’s IPO. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions.
Machinery and equipment	Machinery and equipment Machinery and equipment is recorded at cost less accumulated depreciation. Depreciation is recognized using the straight-line method over the estimated useful life of five years for each asset. Accumulated depreciation at June 30, 2021 was $11,000.
Recently issued accounting pronouncement	Recently issued accounting pronouncement In June 2016, the FASB issued ASU 2016-13, 2016-13 No. 2019-05, No. 2019-11 No. 2016-13,

Investments And Fair Value Me_2

Investments And Fair Value Measurement (Tables)	6 Months Ended
	Jun. 30, 2021
Investments, Fair Value Disclosure [Abstract]
Summary of Amortized cost and estimated fair value of investments	T available-for-sale As of June 30, 2021 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term Investments, non-current (in thousands) Commercial paper $ 2,991 $ — $ — $ 2,991 $ 2,991 $ — Corporate debt securities 29,522 — (33 ) 29,489 19,249 10,240 Total $ 32,513 $ — $ (33 ) $ 32,480 $ 22,240 $ 10,240 As of December 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term Investments, non-current (in thousands) Commercial paper $ 42,709 $ 8 $ (16 ) $ 42,701 $ 42,701 $ — Corporate debt securities 41,169 — (66 ) 41,103 10,130 30,973 Total $ 83,878 $ 8 $ (82 ) $ 83,804 $ 52,831 $ 30,973
Summary of Amortized cost and estimated fair value of investments by contractual maturity	The amortized cost and estimated fair value of investments by contractual maturity at June 30, 2021 are as follows: Estimated Amortized Fair Cost Value (in thousands) Due in one year or less $ 22,258 $ 22,240 Due after one year through two years 10,255 10,240 $ 32,513 $ 32,480
Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis	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, 2021 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money markets funds (included in cash equivalents) $ 61,907 $ — $ — $ 61,907 Commercial paper — 2,991 — 2,991 Corporate debt securities — 29,489 — 29,489 Total assets $ 61,907 $ 32,480 $ — $ 94,387 December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money markets funds (included in cash equivalents) $ 7,839 $ — $ — $ 7,839 Commercial paper — 42,701 — 42,701 Corporate debt securities — 41,103 — 41,103 Total assets $ 7,839 $ 83,804 $ — $ 91,643

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Accrued Expenses	Accrued expenses consist of the following: June 30, December 31, 2021 2020 (in thousands) Payroll and employee related expenses $ 1,677 $ 1,555 External research and development 2,077 3,633 Other accrued expenses 750 390 Total accrued expenses $ 4,504 $ 5,578

Stock-Based Compensation - (Ta

Stock-Based Compensation - (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Summary of Total Stock-Based Compensation Expense	Total stock-based compensation expense was classified in the accompanying condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) (in thousands) Research and development $ 608 $ 39 $ 1,094 $ 78 General and administrative 879 61 1,609 123 Total stock-based compensation expense $ 1,487 $ 100 $ 2,703 $ 201

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Summary of Potentially Dilutive Shares Excluded From The Calculation of Diluted Net Loss	The following common stock equivalents outstanding at June 30, 2021 and 2020 have been excluded from the calculation of diluted net loss per share because their inclusion would have been antidilutive: June 30, 2021 2020 Options to purchase common stock 3,284,323 1,073,044 Redeemable convertible preferred stock — 14,948,249

Nature of Business - Additional

Nature of Business - Additional Information (Detail) $ / shares in Units, $ in Millions	Sep. 03, 2020shares	Aug. 11, 2020USD ($)$ / sharesshares	Jul. 31, 2020	Jun. 30, 2021USD ($)
Subsidiary, Sale of Stock [Line Items]
Proceeds from initial public offering of common stock, net of underwriting discounts, commissions and issuance costs | $		$ 67.7
Cash and cash equivalrents and short term investments | $				$ 95.6
Common Stock [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. All shares, stock options, warrants, redeemable convertible preferred stock conversion prices, ratios and per share information presented in the condensed consolidated financial statements have been adjusted to reflect the reverse stock split on a retroactive basis 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.
Convertible Preferred Stock, Shares Issued upon Conversion		14,948,241
IPO [Member]
Subsidiary, Sale of Stock [Line Items]
Shares Issued During Period		5,109,861
Proceeds from initial public offering of common stock, net of underwriting discounts, commissions and issuance costs | $		$ 67.7
IPO [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Shares Issued During Period		5,000,000
Shares Issued, Price Per Share | $ / shares		$ 15
Over-Allotment Option [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Shares Issued During Period	109,861

Summary of Significant Accoun_3

Summary of Significant Accounting Policies -Additional Information (Detail) - Machinery and Equipment [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 11,000
Property, Plant and Equipment, Depreciation Methods	straight-line method

Investments And Fair Value Me_3

Investments And Fair Value Measurement - Summary Of Amortized Cost And Estimated Fair Value Of Investment (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 32,513	$ 83,878
Debt Securities, Available-for-sale, Unrealized Gain	0	8
Debt Securities, Available-for-sale, Unrealized Loss	(33)	(82)
Debt Securities, Available-for-sale, Fair Value	32,480	83,804
Debt Securities, Available-for-sale, Short-term Investments	22,240	52,831
Debt Securities, Available-for-sale, Investments, non-current	10,240	30,973
Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,991	42,709
Debt Securities, Available-for-sale, Unrealized Gain	0	8
Debt Securities, Available-for-sale, Unrealized Loss		(16)
Debt Securities, Available-for-sale, Fair Value	2,991	42,701
Debt Securities, Available-for-sale, Short-term Investments	2,991	42,701
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	29,522	41,169
Debt Securities, Available-for-sale, Unrealized Gain	0
Debt Securities, Available-for-sale, Unrealized Loss	(33)	(66)
Debt Securities, Available-for-sale, Fair Value	29,489	41,103
Debt Securities, Available-for-sale, Short-term Investments	19,249	10,130
Debt Securities, Available-for-sale, Investments, non-current	$ 10,240	$ 30,973

Investments And Fair Value Me_4

Investments And Fair Value Measurement - Summary Of Amortized Cost And Estimated Fair Value Of Investments By Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 32,513	$ 83,878
Estimated Fair Value	32,480	$ 83,804
Due in one year or less
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22,258
Estimated Fair Value	22,240
Due after one year through two years
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,255
Estimated Fair Value	$ 10,240

Investments And Fair Value Me_5

Investments And Fair Value Measurement - Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Assets, Fair Value Disclosure	$ 94,387	$ 91,643
Money Markets Funds [Member]
Assets:
Assets, Fair Value Disclosure	61,907	7,839
Commercial Paper [Member]
Assets:
Assets, Fair Value Disclosure	2,991	42,701
Corporate Debt Securities [Member]
Assets:
Assets, Fair Value Disclosure	29,489	41,103
Fair Value, Inputs, Level 1 [Member]
Assets:
Assets, Fair Value Disclosure	61,907	7,839
Fair Value, Inputs, Level 1 [Member] | Money Markets Funds [Member]
Assets:
Assets, Fair Value Disclosure	61,907	7,839
Fair Value, Inputs, Level 2 [Member]
Assets:
Assets, Fair Value Disclosure	32,480	83,804
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Assets:
Assets, Fair Value Disclosure	2,991	42,701
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Assets:
Assets, Fair Value Disclosure	$ 29,489	$ 41,103

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Payroll and employee related expenses	$ 1,677	$ 1,555
External research and development	2,077	3,633
Other accrued expenses	750	390
Total accrued expenses	$ 4,504	$ 5,578

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	Aug. 11, 2020
Temporary Equity [Line Items]
Convertible Preferred Stock	$ 0	$ 0
Common Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion			14,948,241

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Aug. 11, 2020	Jun. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock shares authorized		300,000,000	300,000,000
Common stock par value per share		$ 0.0001	$ 0.0001
Preferred stock shares authorized		10,000,000	10,000,000
Preferred stock par value per share		$ 0.0001	$ 0.0001
Proceeds from issuance of initial public offering	$ 67.7
IPO [Member]
Class of Stock [Line Items]
Stock issued during the period, new issues	5,109,861
Sale of Stock to underwritters option to purchase additional shares	109,861
Proceeds from issuance of initial public offering	$ 67.7
Common Stock [Member]
Class of Stock [Line Items]
Common stock shares authorized	300,000,000
Common stock par value per share	$ 0.0001
Common Stock [Member] | IPO [Member]
Class of Stock [Line Items]
Stock issued during the period, new issues	5,000,000
Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock shares authorized	10,000,000
Preferred stock par value per share	$ 0.0001
Maximum [Member]
Class of Stock [Line Items]
Common stock shares authorized	310,000,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Total Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,487	$ 100	$ 2,703	$ 201
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	608	39	1,094	78
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 879	$ 61	$ 1,609	$ 123

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted | shares	862,350
Weighted average exercise price, granted	$ 12.70
Weighted average grant date fair value of stock options granted, Per share	$ 8.85

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Potentially Dilutive Shares Excluded From The Calculation of Diluted Net Loss (Detail) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
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	3,284,323	1,073,044
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

Commitments And Contingencies -

Commitments And Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 04, 2019	Jun. 30, 2015	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised			$ 14,865	$ 6,476	$ 25,243	$ 12,789
Operating lease rental expenses			$ 200	100	$ 300	$ 300
No of days that agreement to be terminated by both parties					60 days
No of days that agreement to be Voluntary terminated by company					90 days
CTSA Agreement [Member] | Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Long-term Agreement commitment amount	$ 4,000
Research and development costs and expenses Incurred							$ 1,000	$ 500
Kuros License Agreement [Member]
Long-term Purchase Commitment [Line Items]
Long-term Agreement commitment amount		$ 56,000
Milestone Payments Paid					$ 8,300
Percentage of royalities on licensed knowhow					50.00%
Kuros License Agreement [Member] | Research And Development Expense Two Thousand Fifteen [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised					$ 1,000
Kuros License Agreement [Member] | Research And Development Expense Two Thousand Sixteen [Member] | Phase One Trail [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised					1,000
Kuros License Agreement [Member] | Research And Development Expense Two Thousand Sixteen [Member] | Phase Two Trial [member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised				$ 4,000
Kuros License Agreement [Member] | Research And Development Expense Two Thousand Twenty One [Member] | Phase Two Trial [member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised					2,000
Kuros License Second Amendment Agreement [Member] | Research And Development Expense Two Thousand Eighteen [Member]
Long-term Purchase Commitment [Line Items]
Research and development expenses recognised					$ 300