X0306 4 2020-08-11 0 0001651431 Checkmate Pharmaceuticals, Inc. CMPI 0001202793 POWELL MICHAEL C/O SOFINNOVA INVESTMENTS, INC. 3000 SAND HILL ROAD, BLDG. 4, SUITE 250 MENLO PARK CA 94025 1 0 1 0 0001612133 Sofinnova Venture Partners IX, L.P. C/O SOFINNOVA INVESTMENTS, INC. 3000 SAND HILL ROAD, BLDG. 4, SUITE 250 MENLO PARK CA 94025 0 0 1 0 0001612134 Sofinnova Management IX, L.L.C. C/O SOFINNOVA INVESTMENTS, INC. 3000 SAND HILL ROAD, BLDG. 4, SUITE 250 MENLO PARK CA 94025 0 0 1 0 0001245624 HEALY JAMES C/O SOFINNOVA INVESTMENTS, INC. 3000 SAND HILL ROAD, BLDG. 4, SUITE 250 MENLO PARK CA 94025 0 0 1 0 Common Stock 2020-08-11 4 C 0 3473374 A 3473374 I See footnote Common Stock 2020-08-11 4 P 0 133333 15.00 A 3606707 I See footnote Series A Preferred Stock 2020-08-11 4 C 0 12500000 0.00 D Common Stock 1671771 0 I See footnote Series B Preferred Stock 2020-08-11 4 C 0 8753350 0.00 D Common Stock 1314165 0 I See footnote Series C Preferred Stock 2020-08-11 4 C 0 3644624 0.00 D Common Stock 487438 0 I See footnote The Series A Preferred Stock and Series C Preferred Stock automatically converted into Common Stock at a rate of 1:7.4771 upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The shares had no expiration date. The Series B Preferred Stock automatically converted into Common Stock at a rate of 1.12256:7.4771 upon the closing of the Issuer's initial public offering without payment of consideration. The Series B Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The shares had no expiration date. The securities are held directly by Sofinnova Venture Partners IX, L.P. (the "Fund"). The general partner of the Fund is Sofinnova Management IX, L.L.C. (the "GP") and may be deemed to have sole voting, investment and dispositive power with respect to the securities held by the Fund. Dr. James I. Healy and Michael F. Powell, Ph.D. are the managing members of the GP and may be deemed to have shared voting, investment and dispositive power with respect to the securities held by the Fund. Each reporting person disclaims beneficial ownership of such securities, except to the extent of his or its proportionate pecuniary interest therein, if any. /s/ Nathalie Auber, attorney-in-fact for Sofinnova Venture Partners IX, L.P. 2020-08-12 /s/ Nathalie Auber, attorney-in-fact for Sofinnova Management IX, L.L.C. 2020-08-12 /s/ Nathalie Auber, attorney-in-fact for James I. Healy 2020-08-12 /s/ Nathalie Auber, attorney-in-fact for Michael F. Powell 2020-08-12