- Aptevo Therapeutics Inc. reported a **100% remission rate** in Cohort 3 of its Phase 1b/2 RAINIER trial evaluating **mipletamig** for newly diagnosed acute myeloid leukemia (AML) patients unfit for intensive chemotherapy.  **[1671584_0001193125-25-205107_apvo-20250916.htm:0]** **[1671584_0001193125-25-205107_apvo-ex99_1.htm:0]** 
- The trial has observed **no dose-limiting toxicities or cytokine release syndrome** to date, demonstrating a consistently favorable safety and tolerability profile for mipletamig.  **[1671584_0001193125-25-205107_apvo-ex99_1.htm:0]** 
- Additionally, **40% of patients** treated in the RAINIER trial have achieved minimal residual disease (MRD)-negative status, which is a critical marker associated with improved overall outcomes in AML.  **[1671584_0001193125-25-205107_apvo-ex99_1.htm:0]** 
- Cohort 3 enrollment is complete, and **Cohort 4 is actively enrolling patients** at the next dose level, with current findings anticipated to be presented at a major medical conference in Q4.  **[1671584_0001193125-25-205107_apvo-ex99_1.htm:0]**

Aptevo Therapeutics (APVO)