X0306 4 2020-06-23 1 0001808158 Repare Therapeutics Inc. RPTX 0001609492 MPM BioVentures 2014, L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001609495 MPM Asset Management Investors BV2014 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001609493 MPM BioVentures 2014 (B), L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001765021 MPM BioVentures 2014 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001765091 MPM BioVentures 2014 GP LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001134657 EVNIN LUKE C/O MPM CAPITAL 450 KENDAL STREET CAMBRIDGE MA 02142 0 0 1 0 Common Shares 2020-06-23 4 C 0 1801581 A 1801581 I See Footnote Common Shares 2020-06-23 4 C 0 952191 A 2753772 I See Footnote Common Shares 2020-06-23 4 P 0 250000 20.00 A 3003772 I See Footnote Class A Preferred Shares 2020-06-23 4 C 0 1801581 0.00 D Common Shares 1801581 0 I See Footnote Class B Preferred Shares 2020-06-23 4 C 0 952191 0.00 D Common Shares 952191 0 I See Footnote All series of convertible preferred shares converted into the number of shares of the Issuer's common shares on a 1-for-1 basis, for no additional consideration, immediately prior to the closing of the Issuer's initial public offering and had no expiration date. The shares are held as follows: 1,636,136 by MPM BioVentures 2014, L.P. ("BV 2014"), 109,128 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)") and 56,317 by MPM Asset Management Investors BV2014 LLC ("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). Luke Evnin, Ansbert Gadicke and Todd Foley are the managing directors of BV LLC and members of AM BV2014. The Reporting Persons disclaim beneficial ownership of the securities except to the extent of his or its respective pecuniary interest therein. The shares are held as follows: 2,500,885 by BV 2014, 166,805 by BV 2014(B) and 86,082 by AM BV2014. The shares were purchased as follows: 227,042 by BV 2014, 15,143 by BV 2014(B) and 7,815 by AM BV2014. The shares are held as follows: 2,727,927 by BV 2014, 181,948 by BV 2014(B) and 93,897 by AM BV2014. No securities held by the Reporting Persons. /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC, the general partner of MPM BioVentures 2014, L.P. 2020-06-25 /s/ Howard Rubin, director of MPM Asset Management Investors BV2014 LLC 2020-06-25 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC, the general partner of MPM BioVentures 2014 (B), L.P. 2020-06-25 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC 2020-06-25 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC 2020-06-25 /s/ Luke Evnin 2020-06-25