Aptevo Reports 10 AML Patients Advanced To Stem Cell Transplant Following Treatment With Mipletamig In Combination With Venetoclax And Azacitidine

Ten patients initially deemed unfit for intensive chemotherapy proceeded to stem cell transplant

Transplant rate compares favorably with historical standard-of-care experience, adding to growing clinical evidence supporting mipletamig's potential to improve outcomes in frontline AML

Aptevo expects the RAINIER dose optimization trial to conclude by year-end, with FDA interaction and initiation of a Phase 2 clinical trial anticipated in the first half of 2027

SEATTLE, WA / ACCESS Newswire / October 26, 2026 / Aptevo Therapeutics Inc. (NASDAQ:APVO), a clinical-stage biotechnology company developing novel multispecific immuno-oncology therapeutics, today announced that ten patients with newly diagnosed acute myeloid leukemia (AML) have advanced to allogeneic stem cell transplant following treatment with mipletamig in combination with venetoclax and azacitidine. Stem cell transplant uses donor cells to replace a patient's blood-forming stem cells and can offer eligible patients the possibility of long-term remission or cure.

Notably, ten of 47 (21%) evaluable frontline patients treated with mipletamig in combination with venetoclax and azacitidine (VEN+AZA) proceeded to allogeneic stem cell transplantation, a potentially curative treatment option. This includes nine patients from the ongoing Phase 1b RAINIER trial and one patient from the previously completed dose expansion trial. This finding is particularly encouraging in a patient population initially deemed unfit for intensive induction chemotherapy, where advanced age, underlying health conditions and other factors can limit treatment options. The ability of these patients to proceed to transplant provides an additional encouraging indication of mipletamig's clinical activity in combination with the current standard of care.

The finding is also notable in the context of historical clinical experience with VEN+AZA alone. In the pivotal Phase 3 VIALE-A trial, three of 286 patients (0.7%) receiving VEN+AZA subsequently underwent stem cell transplantation* compared with (21%). Although cross-trial comparisons are limited by differences in patient populations, study design and follow-up, these observations add to the growing body of evidence supporting mipletamig's potential to improve treatment outcomes and help patients reach potentially curative treatment options. *Gangat N, et al. Venetoclax and hypomethylating agent therapy in newly diagnosed acute myeloid leukemia: A Mayo Clinic series and comparison with VIALE-A study. American Journal of Hematology. 2024.