Mipletamig
Mipletamig is currently being evaluated in the Phase 1b portion of the RAINIER Phase 1b/2 study in combination with standard-of-care venetoclax and azacitidine for the treatment of frontline acute myeloid leukemia (AML) patients who are unfit for intensive induction chemotherapy.
Progress across three clinical trials has been substantial and provide a credible path into Phase 2 development.
Where we are today
Across our clinical program, more than 120 patients have now been treated with mipletamig in three trials.
In our RAINIER study, we’ve seen a strong safety profile, with no cases of cytokine release syndrome through Cohort 5 and infusion-related reactions largely eliminated following refinements to the priming regimen.
On the efficacy side, the early results have been meaningful for patients, including high complete-response rates and, among frontline patients who achieved a complete response, a majority reaching MRD-negative status. Mipletamig has also been granted Orphan Drug status, an important recognition of its potential in a high-need patient population that has limited treatment options.
What’s ahead
Aptevo plans to enter Phase 2 clinical trials with mipletamig in combination therapy for frontline AML, in 1H27.
Monotherapy Data Supports Contribution to the Triplet
Monotherapy Dose Escalation Study in SoC Treatment Relapsed/Refractory Patients
49% clinical benefit rate (19 of 39 evaluable patients: CR, CRi, MLFS, PR or SD; started at a MABEL dose, incremental escalation)
36% of evaluable patients experienced substantial leukemia blast reduction to a clinical meaningful degree compared to baseline, proving the pharmacodynamic effect of the drug
2 complete remissions were observed at the 12 mcg and 18 mcg dose levels where the two largest % reductions in leukemia blast counts occurred
Most CRS cases were during infusion; low-grade & clinically manageable
Single agent leukemia blast reduction
Dose Expansion (monotherapy; cohort 3)
100% clinical benefit rate – of 4 evaluable patients who had AML and were treated with single agent, 1 patient achieved MLFS and 3 achieved SD as their best overall response indicating antileukemic activity.
CRS continued to be low-grade & clinically manageable
Monotherapy study CR = complete remission; Cri = CR with incomplete recovery; MLFS = morphologic leukemia-free state; PR = partial response; SD = stable disease
The results show that mipletamig delivers genuine single-agent activity against acute myeloid leukemia—reinforcing its role within the triplet and Aptevo’s continued advancement of the combination.
Dose exposure at the end of infusion
