X0306 4 2021-06-16 0 0001651431 Checkmate Pharmaceuticals, Inc. CMPI 0001819620 Colabuono Peter C/O CHECKMATE PHARMACEUTICALS, INC. 245 MAIN STREET, 2ND FLOOR CAMBRIDGE MA 02142 1 0 0 0 Stock Option (Right to Buy) 6.27 2021-06-16 4 A 0 10030 0.00 A 2031-06-16 Common Stock 10030 10030 D This option was granted on June 16, 2021 with respect to 10,030 shares of the Issuer's common stock and vests in full on the earlier to occur of (a) the first anniversary of the grant date or (b) the date of the next annual meeting of stockholders following the grant date. /s/ Kleem Chaudhary, attorney-in-fact 2021-06-21