UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 14, 2020

CHECKMATE PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Checkmate Pharmaceuticals, Inc.

245 Main Street, 2^nd Floor

Cambridge, MA 02142

(Address of principal executive offices, including zip code)

(617) 682-3625

(Registrant’s telephone number, including area code)

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

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 13(a) of the Exchange Act. ☐

On October 15, 2020, Checkmate Pharmaceuticals, Inc. (the “Company”) issued a press release announcing new data presentations evaluating CMP-001, the Company’s Toll-like receptor 9 (TLR9) agonist, to be presented at the 35th Annual Meeting of the Society for Immunotherapy of Cancer (“SITC”). The Company also reported that on October 14, 2020, the abstracts for these presentations were inadvertently made publicly available on SITC’s website, in violation of SITC’s disclosure embargo, for a period of time prior to their intended release on November 9, 2020. During this time, investors and other interested parties may have accessed and downloaded such abstracts. The press release, which contains copies of such abstracts as submitted to SITC, is furnished hereto as Exhibit 99.1 and is incorporated herein by reference. The Company undertakes no obligation to update, supplement or amend the materials attached hereto.

The information herein and in the exhibit hereto is being furnished and shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liability of that section, nor shall such information be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

(d) Exhibit

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.