Aptevo says mipletamig triplet posts 93% clinical benefit rate in frontline TP53-mutated AML trial

Aptevo Therapeutics reported new interim results from the RAINIER study testing mipletamig with standard low-intensity therapy in frontline AML.

Responses in difficult-to-treat TP53-mutated patients were stronger than historical outcomes for the current standard regimen, supporting a potential differentiation case.

The update covers 14 evaluable patients, including two from a prior dose-expansion cohort, with most showing meaningful disease control.

Dose optimization remains ongoing, with completion targeted by year-end; regulatory interaction is planned in 1H27 to set next steps.

Results have already been presented in this announcement, not flagged for a future medical meeting disclosure.