X0306 4 2021-02-22 0 0001829802 Sensei Biotherapeutics, Inc. SNSE 0001797409 Cambrian BioPharma Inc 19 MORRIS AVE BROOKLYN NAVY YARD BUILDING, 128 BROOKLYN NY 11025 0 0 1 0 Common Stock 2021-02-22 4 P 0 9802 18.88 A 4712494 D The price reported is a weighted average sales price. These shares were purchased in multiple transactions at prices ranging from $18.55 to $19.50, inclusive. The Reporting Person undertakes to provide to 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 purchased at each separate price within the ranges set herein. These shares are held by Cambrian Biopharma, Inc., a Delaware corporation ("Cambrian"). The Chief Executive Officer of Cambrian, James Peyer, may direct the voting and disposition of the shares held by Cambrian, subject in certain instances to the approval of Cambrian's Board of Directors. Mr. Peyer disclaims beneficial ownership of such shares. Cambrian Biopharma, Inc. By: /s/ James Peyer 2021-02-24