On January 25, 2023, Bradley L Radoff announced that he has sent an open letter to Sesen Bio Inc, reiterating his intention to vote against the proposed merger with Carisma Therapeutics Inc by the Company, mentioned the reasons for that, the amount of dividend paid by the Company, difference in proposed cash contribution from Company shareholders compared to Carisma stockholders, different corporate governance and stockholder feedback between the Company and Carisma Therapeutics. In addition, Bradley L Radoff made an offer to the Company, for paid advisory roles and cash reimbursement of his expenses incurred in relation to his opposition to the proposed merger in exchange for his agreement to vote his shares in favor of the merger.