Mipletamig Shows Strong Clinical Activity in Frontline AML, With 85% Remission Rate and Favorable Safety Profile
DENVER, Colo., Jun 18, 2025 (247marketnews.com)- Aptevo Therapeutics (NASDAQ:APVO) announced compelling new data from its ongoing Phase 1b/2 RAINIER trial evaluating mipletamig, a novel CD123 x CD3 bispecific antibody, in combination with standard-of-care venetoclax and azacitidine (ven/aza) in newly diagnosed, unfit acute myeloid leukemia (AML) patients.
Across two ongoing studies, 85% of evaluable patients treated with the mipletamig-based triplet regimen have achieved remission — an encouraging outcome that exceeds historical benchmarks, including results from the VIALE-A trial, which evaluated ven/aza alone. Notably, no dose-limiting toxicities or CRS have been reported to date, highlighting mipletamig’s differentiated safety profile. The third dosing cohort, currently testing the highest dose level, is nearing full enrollment.
Marvin White, Aptevo’s President and CEO, commented, “These results deepen our conviction in mipletamig’s ability to elevate treatment outcomes for frontline AML patients who are not candidates for intensive chemotherapy. This outstanding remission rate, combined with a compelling safety profile-no CRS reported in the first two cohorts, reinforces mipletamig’s potential to meaningfully enhance the venetoclax/azacitidine backbone.
“We believe our success with mipletamig is a direct reflection of our unique CD3 engineering strategy. We are the only ones using the CRIS-7 binding domain. We did this purposefully, to mitigate cytokine-related toxicity while preserving anti-cancer activity. This innovation not only differentiates mipletamig but represents a core advantage we intend to carry forward across our CD3 pipeline, including with our preclinical candidate, APVO442, for prostate cancer.”
Mipletamig Enables Rare Transplant Path in Unfit AML
The latest data also highlight mipletamig’s potential to enable outcomes previously considered unachievable in this high-risk patient population. Among patients achieving remission:
- Three had poor prognostic indicators at baseline, including high-risk genetic markers
- One patient successfully proceeded to stem cell transplant, a rare but curative path typically inaccessible to unfit AML patients
- Another patient achieved MRD-negative complete remission despite harboring a TP53 mutation, which is typically linked to treatment resistance
Emerging as a Frontline Standard
AML is a fast-progressing and deadly blood cancer, particularly in older or medically unfit patients, where treatment choices are limited. The RAINIER trial continues to reinforce mipletamig’s potential as a best-in-class, highly targeted immunotherapy with a favorable safety and efficacy profile. Aptevo believes mipletamig could play a pivotal role in shaping the future standard of care for frontline AML.
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