X0306 4 2021-06-14 0 0001808158 Repare Therapeutics Inc. RPTX 0001473930 Foley Todd C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 1 0 0 0 Common Shares 2021-06-14 4 S 0 881 33.09 D 2330102 I See Footnote Common Shares 2021-06-16 4 S 0 1862 33.33 D 2328240 I See Footnote Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 on 3/31/2021. The shares were sold as follows: 852 by MPM BioVentures 2014, L.P. ("BV 2014") and 29 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"). The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $32.95 to $33.57 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held as follows: 2,121,245 by BV 2014, 135,843 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)") and 73,014 by AM BV2014. MPM BioVentures 2014 GP LLC and MPM BioVentures 2014 LLC ("BV LLC") are the direct and indirect general partners of BV 2014 and BV 2014(B). BV LLC is the manager of AM BV2014. Todd Foley is a managing director of BV LLC. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein. The shares were sold as follows: 1,800 by BV 2014 and 62 by AM BV2014. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $32.95 to $33.66 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held as follows: 2,119,445 by BV 2014, 135,843 by BV 2014(B) and 72,952 by AM BV2014. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein. /s/ Todd Foley 2021-06-16