X0306 4 2021-07-30 0 0001829802 Sensei Biotherapeutics, Inc. SNSE 0001872280 Humer Kristian C/O SENSEI BIOTHERAPEUTICS, INC. 1405 RESEARCH BLVD., SUITE 125 ROCKVILLE MD 20850 1 0 0 0 Stock Option (Right to Buy) 7.89 2021-07-30 4 A 0 16667 0.00 A 2031-07-29 Common Stock 16667 16667 D One thirty-sixth (1/36th) of the shares underlying the option granted shall vest and become exercisable each month following July 30, 2021, over three years such that the options shall be 100% vested on July 30, 2024, subject to the grantee's Continuous Service (as defined in the Issuer's 2021 Equity Incentive Plan) through each such vesting date. /s/ Mark Ballantyne (Attorney-in-Fact) 2021-08-02