X0202 SCHEDULE 13G/A 0001778071 XXXXXXXX LIVE 1 Common Stock, $0.001 par value per share 06/30/2026 0002012593 Rapport Therapeutics, Inc. 75383L102 1325 Boylston Street Suite 401 Boston MA 02215 Rule 13d-1(d) Third Rock Ventures V, L.P. b DE 0 6280525 0 6280525 6280525 N 13.1 PN (1) The percent of class was calculated based on 47,978,286 shares of common stock issued and outstanding as of August 3, 2026, as disclosed in the Issuer's 10-Q filed with the Securities and Exchange Commission on August 5, 2026. Third Rock Ventures GP V, L.P. b DE 0 6280525 0 6280525 6280525 N 13.1 PN TRV GP V, LLC b DE 0 6280525 0 6280525 6280525 N 13.1 OO Third Rock Ventures VI, L.P. b DE 0 969218 0 969218 969218 N 2.0 PN Third Rock Ventures GP VI, L.P. b DE 0 969218 0 969218 969218 N 2.0 PN TRV GP VI, LLC b DE 0 969218 0 969218 969218 N 2.0 OO Rapport Therapeutics, Inc. 1325 Boylston Street, Suite 401 Boston, MA 02215 (i) Third Rock Ventures V, L.P. ("TRV V"); (ii) Third Rock Ventures GP V, L.P. ("TRV GP V"), which is the sole general partner of TRV V; (iii) TRV GP V, LLC ("TRV GP V LLC"), which is the sole general partner of TRV GP V; (iv) Third Rock Ventures VI, L.P. ("TRV VI"); (v) Third Rock Ventures GP VI, L.P. ("TRV GP VI"), which is the sole general partner of TRV VI; and (vi) TRV GP VI, LLC ("TRV GP VI LLC"), which is the sole general partner of TRV GP VI. The address of the principal business office of each of the Reporting Persons is Third Rock Ventures, LLC, 201 Brookline Ave, Suite 1401, Boston, MA 02215. Each of TRV V, TRV GP V, TRV VI and TRV GP VI is a Delaware limited partnership. Each of TRV GP V LLC and TRV GP VI LLC is a Delaware limited liability company. Y (i) TRV V directly owns 6,280,525 shares of Common Stock (the "V Shares"). (ii) TRV GP V is the general partner of TRV V and may be deemed to beneficially own the V Shares. (iii) TRV GP V LLC is the general partner of TRV GP V and may be deemed to beneficially own the V Shares. (iv) TRV VI directly owns 969,218 shares of Common Stock (the "VI Shares"). (v) TRV GP VI is the general partner of TRV VI and may be deemed to beneficially own the VI Shares. (vi) TRV GP VI LLC is the general partner of TRV GP VI and may be deemed to beneficially own the VI Shares. Each of TRV V, TRV GP V, and TRV GP V LLC, on the one hand, and TRV VI, TRV GP VI and TRV GP VI LLC, on the other hand, disclaim the existence of a "group" for purposes of Rule 13d-5 of the Securities Exchange Act of 1934, as amended, and nothing contained in this report shall be deemed an admission that any such group exists or may exist. The V shares represent approximately 13.1% of the outstanding shares of Common Stock. The VI shares represent approximately 2.0% of the outstanding shares of Common Stock. The percent of class was calculated based on 47,978,286 shares of common stock issued and outstanding as of August 3, 2026, as disclosed in the Issuer's 10-Q filed with the Securities and Exchange Commission on August 5, 2026. TRV V - 0 TRV GP V - 0 TRV GP V LLC - 0 TRV VI - 0 TRV GP VI - 0 TRV GP VI LLC - 0 TRV V - 6,280,525 TRV GP V - 6,280,525 TRV GP V LLC - 6,280,525 TRV VI - 969,218 TRV GP VI - 969,218 TRV GP VI LLC - 969,218 TRV V - 0 TRV GP V - 0 TRV GP V LLC - 0 TRV VI - 0 TRV GP VI - 0 TRV GP VI LLC - 0 TRV V - 6,280,525 TRV GP V - 6,280,525 TRV GP V LLC - 6,280,525 TRV VI - 969,218 TRV GP VI - 969,218 TRV GP VI LLC - 969,218 Y Y Y Y Y Y Third Rock Ventures V, L.P. By: THIRD ROCK VENTURES GP V, L.P., General Partner, By: TRV GP V, LLC, General Partner, By: /s/ Kevin Gillis 08/14/2026 Third Rock Ventures GP V, L.P. By: TRV GP V, LLC, General Partner, By: /s/ Kevin Gillis 08/14/2026 TRV GP V, LLC By: /s/ Kevin Gillis 08/14/2026 Third Rock Ventures VI, L.P. By: THIRD ROCK VENTURES GP VI, L.P., General Partner, By: TRV GP VI, LLC, General Partner, By: /s/ Kevin Gillis 08/14/2026 Third Rock Ventures GP VI, L.P. By: TRV GP VI, LLC, General Partner, By: /s/ Kevin Gillis 08/14/2026 TRV GP VI, LLC By: /s/ Kevin Gillis 08/14/2026