X0306 4 2021-08-23 0 0001789972 Cullinan Oncology, Inc. CGEM 0001691428 UBS Oncology Impact Fund L.P. C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001721036 Oncology Impact Fund (Cayman) Management L.P. C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001721035 MPM Oncology Impact Management GP LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001687078 MPM Oncology Impact Management LP C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 Common Stock 2021-08-23 4 S 0 53359 29.11 D 7858018 D Common Stock 2021-08-24 4 S 0 50822 29.48 D 7807196 D Common Stock 2021-08-25 4 S 0 1713 29.09 D 7805483 D Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 on June 23, 2021. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.00 to $29.41 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. These securities are owned directly by UBS Oncology Impact Fund LP ("OIF"). The general partner of OIF is Oncology Impact Fund (Cayman) Management L.P. ("OIF GP"). The general partner of OIF GP is MPM Oncology Impact Management L.P. The general partner of MPM Oncology Impact Management L.P. is MPM Oncology Impact Management GP LLC. Dr. Ansbert Gadicke is a member of the Issuer's board of directors and is a managing member and the managing director of MPM Oncology Impact Management GP LLC. Each of the Reporting Persons disclaims beneficial ownership of the securities except to the extent of its pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.15 to $29.715 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 price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.01 to $29.47 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. /s/ Ansbert Gadicke, managing director of MPM Oncology Impact Management GP LLC, the general partner of MPM Oncology Impact Management LP, the general partner of Oncology Impact Fund (Cayman) Management L.P., the GP of UBS Oncology Impact Fund L.P 2021-08-25 /s/ Ansbert Gadicke, managing director of MPM Oncology Impact Management GP LLC, the general partner of MPM Oncology Impact Management LP, the general partner of Oncology Impact Fund (Cayman) Management L.P. 2021-08-25 /s/ Ansbert Gadicke, managing director of MPM Oncology Impact Management GP LLC 2021-08-25 /s/ Ansbert Gadicke, managing director of MPM Oncology Impact Management GP LLC, the general partner of MPM Oncology Impact Management LP 2021-08-25