X0206 3/A 2021-02-03 2021-02-03 0 0001829802 Sensei Biotherapeutics, Inc. SNSE 0001594129 Pierce Robert Hamilton C/O SENSEI BIOTHERAPEUTICS, INC. 1405 RESEARCH BLVD, SUITE 125 ROCKVILLE MD 20850 0 1 0 0 Chief Scientific Officer Common Stock 95822 I By spouse These shares were omitted from the reporting person's original Form 3. The reporting person disclaims beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of the securities for purposes of Section 16 or for any other purpose. /s/ Mark Ballantyne, Attorney-in-Fact 2021-08-10