Aptevo Therapeutics Inc

Aptevo Therapeutics announced a 93% clinical benefit rate with its mipletamig triplet in evaluable frontline acute myeloid leukemia patients with TP53 mutations, a difficult-to-treat population. Of 14 evaluable patients treated with mipletamig plus venetoclax and azacitidine, 13 experienced clinical benefit, including 11 achieving complete remission or complete remission with incomplete hematologic recovery, a 79% rate that nearly doubles the published 41% composite remission rate for venetoclax plus azacitidine alone in similar patients. The RAINIER study, a Phase 1b/2 dose optimization trial evaluating the triplet in frontline AML patients unfit for intensive chemotherapy, is expected to complete this phase by year-end, with regulatory interaction planned for the first half of 2027. Aptevo's lead candidate mipletamig is designed to target CD123 and has orphan drug designation for AML.