As filed with the Securities and Exchange Commission on March 29, 2022

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

Under

The Securities Act of 1933

CHECKMATE PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

245 Main Street, 2^nd Floor

Cambridge, MA 02142

(617) 682-3625

(Address, including zip code and telephone number, including area code, of Registrant’s principal executive offices)

Checkmate Pharmaceuticals, Inc. 2020 Stock Option and Incentive Plan

(Full title of the plans)

Robert Dolski

Chief Financial Officer

245 Main Street, 2^nd Floor

Cambridge, MA 02142

(617) 682-3625

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Mitchell Bloom, Esq.

Benjamin Marsh, Esq.

Goodwin Procter LLP

100 Northern Avenue

Boston, MA 02210

(617) 570-1000

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

EXPLANATORY NOTE

REGISTRATION OF ADDITIONAL SHARES PURSUANT TO GENERAL INSTRUCTION E

This Registration Statement has been filed by Checkmate Pharmaceuticals, Inc. to register 865,223 additional shares of common stock, par value $0.0001 per share (“Common Stock”) available for issuance under the Checkmate Pharmaceuticals, Inc. 2020 Stock Option and Incentive Plan (the “2020 Plan”). This Registration Statement relates to securities of the same class as those that were previously registered by the registrant on a Registration Statement on Form S-8  filed with the Securities and Exchange Commission on August 11, 2020 (File. No. 333-244375) (the “2020 Registration Statement”).

Pursuant to General Instruction E to Form S-8 regarding registration of additional securities, the entire contents of the 2020 Registration Statement are incorporated herein by reference, except to the extent supplemented, amended or superseded by the information set forth herein.

Part II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8. Exhibits.

Refer to the Exhibit Index for a list of exhibits filed as part of this registration statement, which Exhibit Index is incorporated herein by reference.

EXHIBIT INDEX

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Cambridge, State of Massachusetts, on this 29th day of March 2022.

POWER OF ATTORNEY AND SIGNATURES

KNOW ALL BY THESE PRESENT, that each individual whose signature appears below hereby constitutes and appoints each of Alan Bash and Robert Dolski, as such person’s true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for such person in such person’s name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement on Form S-8, and to file the same, with all exhibits thereto, and all documents in connection therewith, with the Securities and Exchange Commission granting unto each said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as such person might or could do in person, hereby ratifying and confirming all that any said attorney-in-fact and agent, or any substitute or substitutes of any of them, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following person in the capacities and on the date indicated.

Exhibit 5.1

March 29, 2022

Checkmate Pharmaceuticals, Inc.

245 Main Street, 2nd Floor

Cambridge, MA 02142

Re: Securities Being Registered under Registration Statement on Form S-8

We have acted as counsel to you in connection with your filing of a Registration Statement on Form S-8 (the “Registration Statement”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), on or about the date hereof relating to an aggregate of 865,223 shares (the “Shares”) of Common Stock, $0.0001 par value per share (“Common Stock”), of Checkmate Pharmaceuticals, Inc., a Delaware corporation (the “Company”), that may be issued pursuant to the Company’s 2020 Stock Option and Incentive Plan (the “Plan”). We have reviewed such documents and made such examination of law as we have deemed appropriate to give the opinions set forth below. We have relied, without independent verification, on certificates of public officials and, as to matters of fact material to the opinion set forth below, on certificates of officers of the Company. The opinion set forth below is limited to the Delaware General Corporation Law.

For purposes of the opinion set forth below, we have assumed that no event occurs that causes the number of authorized shares of Common Stock available for issuance by the Company to be less than the number of then unissued Shares.

Based on the foregoing, we are of the opinion that the Shares have been duly authorized and, upon issuance and delivery against payment therefor in accordance with the terms of the Plan, will be validly issued, fully paid and nonassessable.

We hereby consent to the inclusion of this opinion as Exhibit 5.1 to the Registration Statement. In giving our consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations thereunder.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the use of our report dated March 29, 2022, with respect to the consolidated financial statements of Checkmate Pharmaceuticals, Inc. and subsidiary, incorporated herein by reference.

/s/ KPMG LLP

Boston, Massachusetts

March 29, 2022

Exhibit 107

Calculation of Filing Fee Table

Form S-8

(Form Type)

Checkmate Pharmaceuticals, Inc.

(Exact Name of Registrant as Specified in its Charter)

Table 1: Newly Registered Securities