Aptevo Therapeutics Presents Preliminary Results From Ongoing Phase 1b/2 RAINIER Study Evaluating Mipletamig In Combination With AZA/VEN For Newly Diagnosed AML Patients, At ASH Annual Meeting

100% of patients in Cohorts 1-3 remain free of cytokine release syndrome

CRIS-7-derived CD3 design underpins a controlled T-cell response, supporting the differentiated safety profile, combinability with standard of care

SEATTLE, WA / ACCESS Newswire / December 9, 2025 / Aptevo Therapeutics Inc. (NASDAQ:APVO), a clinical-stage biotechnology company focused on developing novel immune-oncology therapeutics based on its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies, presented preliminary results from its ongoing Phase 1b/2 RAINIER study evaluating mipletamig, a CD123 x CD3 bispecific molecule, in combination with azacitidine and venetoclax (AZA/VEN) for newly diagnosed acute myeloid leukemia (AML) patients who are unfit for intensive chemotherapy. The data were presented on December 8, 2025, in a poster session at the American Society of Hematology (ASH) Annual Meeting.

Across dose-optimization Cohorts 1-3, mipletamig combined with AZA/VEN demonstrated high remission rates and a compelling safety/tolerability profile, reinforcing the potential of T-cell engagement in frontline AML when safety can be effectively managed. Aptevo's proprietary use of the CRIS-7-derived CD3 binding domain differentiates mipletamig in the category.