X0508 4 2023-09-09 0 0001828522 eFFECTOR Therapeutics, Inc. EFTR 0001367451 Loewy Caroline M C/O EFFECTOR THERAPEUTICS, INC. 142 NORTH CEDROS AVENUE, SUITE B SOLANA BEACH CA 92075 1 0 0 0 0 Stock Option (Right to Buy) 0.646 2023-09-09 4 A 0 40000 0.00 A 2033-09-08 Common Stock 40000 40000 D The shares subject to the option will vest in substantially equal monthly installments over three years, commencing on September 9, 2023, subject to the Reporting Person's continued service with the Issuer through each vesting date. /s/ Michael Byrnes, Attorney-in-Fact for Caroline M. Loewy 2023-09-11