X0306 4 2022-03-08 0 0001829802 Sensei Biotherapeutics, Inc. SNSE 0001238325 RINGO WILLIAM R C/O SENSEI BIOTHERAPEUTICS, INC. 1405 RESEARCH BLVD., SUITE 125 ROCKVILLE MD 20850 1 0 0 0 Common Stock 2022-03-08 4 A 0 8933 0.00 A 8933 D Common Stock 2022-03-08 4 A 0 10000 0.00 A 18933 D Stock Option (Right to Buy) 3.08 2022-03-08 4 A 0 29100 0.00 A 2032-03-07 Common Stock 29100 29100 D These shares represent restricted stock units (the "RSUs"). Each RSU represents a contingent right to receive one share of the common stock of the Issuer. The shares underlying the RSUs vest in three equal annual installments on each of March 8, 2023, March 8, 2024, and March 8, 2025, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date. These shares represent RSUs. Each RSU represents a contingent right to receive one share of the common stock of the Issuer. The shares underlying the RSUs vest in full on the first anniversary of the date of grant, on March 8, 2023, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date. Includes 8,933 shares acquired by the Reporting Person as of March 8, 2022 as an RSU award. The shares subject to the option vest monthly over thirty-six (36) months from the vesting commencement date, March 8, 2022, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date. /s/ Mark Ballantyne, Attorney-in-Fact 2022-03-09