Across two trials, 9 of 10 frontline AML patients achieved remission when treated with mipletamig in combination with the standard of care

Triplet Combination with mipletamig continues to outperform doublet combination benchmark

No Cytokine Release Syndrome (CRS) has been observed in the RAINIER trial to date

Cohort 2 enrollment nears completion

SEATTLE, WA / ACCESS Newswire / March 20, 2025 / Aptevo Therapeutics ("Aptevo") (NASDAQ:APVO), a clinical-stage biotechnology company developing novel bispecific immuno-oncology therapeutics based on its proprietary ADAPTIR and ADAPTIR-FLEX platform technologies, today announced two additional frontline AML patients have achieved remission* within 30 days of treatment in the Company's RAINIER dose optimization trial evaluating mipletamig in combination with standard of care for patients unfit for intensive chemotherapy. In total, 9 of 10 frontline patients across two trials achieved remission* when receiving the triplet combination of mipletamig + venetoclax + azacitidine (ven/aza). Notably, no CRS has been reported in the RAINIER trial to date.

The data builds on previously reported favorable outcomes from RAINIER's Cohort 1 and the completed dose expansion trial where 100% of frontline patients achieved remission. Together with the addition of these interim Cohort 2 results, mipletamig has achieved a compelling overall remission rate of 90% among frontline patients. This outperforms the doublet remission* rate from a venetoclax + azacitidine only study, of 66%. Additionally, the frontline patient triplet therapy CR rate of 70% outperforms the CR rate from a venetoclax + azacitidine only study of 36% (Viale-A Pivotal trial).Thus far, all RAINIER patients who achieved remission remain in remission.

Cohort 2 will include six patients, dosed at the 18mcg level, the same dose used in combination with ven/aza in the completed expansion trial.

Three patients evaluable for efficacy achieved the following outcomes:

Two patients achieved remission withing 30 days of being dosed

One patient progressed after the first cycle and passed away for reasons unrelated to study drugs

Cohort 2 enrollment is nearing completion