X0306 4 2022-05-09 0001828522 eFFECTOR Therapeutics, Inc. EFTR 0001602744 Presidio Management Group X LLC 1460 EL CAMINO REAL, STE 100 MENLO PARK CA 94025 0 0 1 0 0001440514 US VENTURE PARTNERS X LP 1460 EL CAMINO REAL, STE 100 MENLO PARK CA 94025 0 0 1 0 0001453359 USVP X AFFILIATES LP 1460 EL CAMINO REAL, STE 100 MENLO PARK CA 94025 0 0 1 0 0001474322 Tansey Casey M 1460 EL CAMINO REAL SUITE 100 MENLO PARK CA 94025 0 0 1 0 0001225480 ROOT JONATHAN D 1460 EL CAMINO REAL SUITE 100 MENLO PARK CA 94025 0 0 1 0 Common Stock 2022-05-09 4 S 0 3876 2.536 D 4380425 I Directly owned by USVP X Common Stock 2022-05-09 4 S 0 124 2.537 D 140137 I Directly owned by AFF X Common Stock 2022-05-10 4 S 0 38743 2.413 D 4341682 I Directly owned by USVP X Common Stock 2022-05-10 4 S 0 1241 2.413 D 138896 I Directly owned by AFF X Common Stock 2022-05-11 4 S 0 4845 2.345 D 4336837 I Directly owned by USVP X Common Stock 2022-05-11 4 S 0 155 2.346 D 138741 I Directly owned by AFF X The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $2.43 to $2.61, inclusive for sales on 5/9/22; prices ranging from $2.40 to $2.45, inclusive for sales on 5/10/22; and prices ranging from $2.14 to $2.40, inclusive for sales on 5/11/22;. The reporting persons undertake to provide 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 ranges set forth in this footnote to this Form 4. Presidio Management Group X, L.L.C. ("PMG X"), the general partner of each of U.S. Venture Partners X, L.P. ("USVP X") and USVP X Affiliates L.P. ("AFF X") (together, the "USVP X Funds"), has sole voting and dispositive power with respect to the shares held by the USVP X Funds. Jonathan Root is a managing member of PMG X with additional rights with respect to the Issuer's securities, and may be deemed to have sole voting and dispositive power with respect to the shares. Casey Tansey is the sole managing partner of PMG X and may be deemed to have sole dispositive power over the reported securities held by the USVP X Funds and may be deemed to have shared voting power over the reported securities held by the USVP X Funds. Each of the foregoing persons disclaims beneficial ownership of such securities, except to the extent of any pecuniary interest therein. Dale Holladay, Attorney in Fact for each Reporting Person 2022-05-11