X0306 4 2020-12-22 0 0001651431 Checkmate Pharmaceuticals, Inc. CMPI 0001817587 Chaudhary Kleem C/O CHECKMATE PHARMACEUTICALS, INC. 245 MAIN STREET, 2ND FLOOR CAMBRIDGE MA 02142 0 1 0 0 Chief Business Officer Common Stock 2020-12-22 4 M 0 4000 2.62 A 4000 D Stock Option (right to buy) 2.62 2020-12-22 4 M 0 4000 0.00 D 2029-11-13 Common Stock 4000 101508 D 25% of the shares subject to such option vested and became exercisable on November 1, 2020 with the remainder to vest in substantially equal monthly installments for a period of 36 months thereafter, subject to the Reporting Person's continuous service to the Issuer on each such date. This option was initially for 105,508 shares and the Reporting Person has exercised his option to purchase 4,000 shares. /s/ Kleem Chaudhary 2020-12-23