X0508 4 2023-11-14 1 0001966494 CARGO Therapeutics, Inc. CRGX 0001778071 Third Rock Ventures V, L.P. C/O THIRD ROCK VENTURES, LLC 201 BROOKLINE AVE, SUITE 1401 BOSTON MA 02215 0 0 1 0 0001977498 Third Rock Ventures GP V, LP 201 BROOKLINE AVE, SUITE 1401 BOSTON MA 02215 0 0 1 0 0001990717 TRV GP V, LLC 201 BROOKLINE AVE, SUITE 1401 BOSTON MA 02215 0 0 1 0 0001931056 Third Rock Ventures VI, L.P. 201 BROOKLINE AVE, SUITE 1401 BOSTON MA 02215 0 0 1 0 0001977499 Third Rock Ventures GP VI, L.P. 201 BROOKLINE AVE, SUITE 1401 BOSTON MA 02215 0 0 1 0 0001990716 TRV GP VI, LLC 201 BROOKLINE AVE, SUITE 1401 BOSTON MA 02215 0 0 1 0 0 Common Stock 2023-11-14 4 C 0 1737216 A 1737216 D Common Stock 2023-11-14 4 C 0 473786 A 473786 I See Footnotes Common Stock 2023-11-14 4 P 0 1333333 15.00 A 1807119 I See Footnotes Series A-1 Preferred Stock 2023-11-14 4 C 0 23571429 0.00 D Common Stock 1737216 0 D Series A-1 Preferred Stock 2023-11-14 4 C 0 6428571 0.00 D Common Stock 473786 0 I See Footnotes Represents the total number of shares of Common Stock received by Third Rock Ventures V, L.P. ("TRV V") upon conversion of the preferred stock of the Issuer in connection with the closing of the Issuer's initial public offering. The Series A-1 Preferred Stock converted into Common Stock on a 13.5685-for-1 basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A-1 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 Series A-1 Preferred Stock had no expiration date. These shares are directly held by TRV V. The general partner of TRV V is Third Rock Ventures GP V, L.P. ("TRV GP V"). The general partner of TRV GP V is TRV GP V, LLC ("TRV GP V LLC"). Each of TRV GP V and TRV GP V LLC disclaims beneficial ownership of these shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares. Represents the total number of shares of Common Stock received by Third Rock Ventures VI, L.P. ("TRV VI") upon conversion of the preferred stock of the Issuer in connection with the closing of the Issuer's initial public offering. These shares are directly held by TRV VI. The general partner of TRV VI is Third Rock Ventures GP VI, L.P. ("TRV GP VI"). The general partner of TRV GP VI is TRV GP VI, LLC ("TRV GP VI LLC"). Each of TRV GP VI and TRV GP VI LLC disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares. Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV V related parties and the TRV VI related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties. /s/ Kevin Gillis, Chief Operating Officer of TRV GP V, LLC, general partner of Third Rock Ventures GP V, L.P., general partner of Third Rock Ventures V, L.P. 2023-11-14 /s/ Kevin Gillis, Chief Operating Officer of TRV GP V, LLC, general partner of Third Rock Ventures GP V, L.P. 2023-11-14 /s/ Kevin Gillis, Chief Operating Officer of TRV GP V, LLC 2023-11-14 /s/ Kevin Gillis, Chief Operating Officer of TRV GP VI, LLC, general partner of Third Rock Ventures GP VI, L.P., general partner of Third Rock Ventures VI, L.P. 2023-11-14 /s/ Kevin Gillis, Chief Operating Officer of TRV GP VI, LLC, general partner of Third Rock Ventures GP VI, L.P. 2023-11-14 /s/ Kevin Gillis, Chief Operating Officer of TRV GP VI, LLC 2023-11-14