X0306 4 2020-10-06 0 0001671818 Oncorus, Inc. ONCR 0001609492 MPM BioVentures 2014, L.P. C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001473930 Foley Todd C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001609493 MPM BioVentures 2014 (B), L.P. C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001609495 MPM Asset Management Investors BV2014 LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001765021 MPM BioVentures 2014 LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001765091 MPM BioVentures 2014 GP LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001263048 MPM ASSET MANAGEMENT LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 Common Stock 2020-10-06 4 C 0 1783879 A 1899702 I See footnote Common Stock 2020-10-06 4 C 0 775975 A 2675677 I See footnote Common Stock 2020-10-06 4 P 0 173776 15.00 A 2849453 I See footnote Series A-1 Preferred Stock 2020-10-06 4 C 0 1783879 0.00 D Common Stock 1783879 0 I See footnote Series B Preferred Stock 2020-10-06 4 C 0 775975 0.00 D Common Stock 775975 0 I See footnote Each share of Series A-1 Preferred and Series B Preferred Stock automatically converted into shares of Common Stock upon the closing of the Issuer's initial public offering for no additional consideration, on a one-for-one basis, and had no expiration date. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. The shares are held as follows: 1,382,943 by MPM BioVentures 2014, L.P. ("BV 2014"), 92,239 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 50,164 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 224,924 by MPM Sunstates Fund, L.P. ("MPM SunStates"), 33,609 by MPM Asset Management Investors Sunstates Fund LLC ("AM SunStates") and 115,823 by MPM Asset Management LLC ("AM LLC"). 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. MPM SunStates Fund GP LLC and MPM SunStates GP Managing Member LLC ("SunStates GP") are the direct and indirect general partners of MPM SunStates. SunStates GP is the manager of AM SunStates. Luke Evnin, Ansbert Gadicke and Todd Foley are the managing directors of BV LLC, Luke Evnin and Anbsert Gadicke are the members of AM LLC and Ansbert Gadicke is a member of SunStates GP. The shares are held as follows: 2,018,001 by BV 2014, 134,595 by BV 2014(B), 73,199 by AM BV2014, 290,632 by MPM SunStates, 43,427 by AM SunStates and 115,823 by AM LLC. The shares are held as follows: 2,155,108 by BV 2014, 143,740 by BV 2014(B), 78,172 by AM BV2014, 310,251 by MPM SunStates, 46,359 by AM SunStates and 115,823 by AM LLC. The shares are held as follows: 1,382,943 by BV 2014, 92,239 by BV 2014(B), 50,164 by AM BV2014, 224,924 by MPM SunStates and 33,609 by AM SunStates. The shares are held as follows: 635,058 by BV 2014, 42,356 by BV 2014(B), 23,035 by AM BV2014, 65,708 by MPM SunStates and 9,818 by AM SunStates. See Form 4 for MPM SunStates Fund, L.P for additional members of this joint filing /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 2020-10-08 /s/ Todd Foley 2020-10-08 /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. 2020-10-08 Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the manager of MPM Asset Management Investors BV2014 LLC 2020-10-08 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC 2020-10-08 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC 2020-10-08 /s/ Ansbert Gadicke, member of MPM Asset Management LLC 2020-10-08