On April 28, 2025 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, reported data presented at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting supporting Actimab-A’s mutation agnostic antileukemic effect and backbone therapy potential in preclinical acute myeloid leukemia (AML) models (Press release, Actinium Pharmaceuticals, APR 28, 2025, View Source;302439223.html [SID1234652271]). The preclinical data demonstrate that the combination of Actimab-A with standard of care AML therapies including menin and FLT3 inhibitors and the hypomethylating agent (HMA) azacitidine resulted in significant antileukemic activity in AML cells lines with FLT3, NPM1, KMT2A and TP53 mutations. Additionally, in animal models, Actimab-A significantly enhanced tumor growth inhibition, prolonged the duration of response and survival when combined with the menin inhibitor revumenib (Syndax Pharmaceuticals, Inc.), and potentiated AML cell killing in combination with the FLT3 inhibitor gilteritinib (Astellas Pharma US, Inc.) and HMA azacitidine.
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Sandesh Seth, Actinium’s Chairman and CEO, said, "In multiple clinical trials, Actimab-A has demonstrated potent single agent activity, synergy with other therapeutic modalities and efficacy in patients with high-risk features such as a TP53 mutation. To our knowledge, Actimab-A is the only AML therapy to achieve all of these outcomes, which we attribute to its mutation agnostic, backbone therapy profile. The data presented at AACR (Free AACR Whitepaper) further support Actimab-A’s mutation agnostic mechanism of action across several of the most commonly expressed mutations and synergy with the targeted therapies approved for patients with these mutations. With multiple clinical trials underway and being planned across the AML treatment settings, we are focused on generating strong clinical outcomes starting in the second half of this year and committed to realizing Actimab-A’s potential for patients who have significant unmet needs."
Actimab-A is Actinium’s lead radiotherapy that delivers Actinium-225, a potent alpha-emitter radioisotope payload that can produce lethal double strand DNA breaks to kill targeted cells that express CD33. CD33 is expressed ubiquitously in AML and in other myeloid malignancies such as myeloid dysplastic syndromes (MDS), which Actinium estimates to be an addressable market of over 100,000 patients in the U.S. and EU5. Actimab-A is also being advanced into a pivotal Phase 2/3 trial in combination with the chemotherapy regimen CLAG-M in patients with relapsed or refractory AML and in newly diagnosed AML in combination with Venetoclax and ASTX-727 (Taiho Oncology, an Otsuka holdings company) an oral hypomethylating agent (HMA) under a cooperative research and development agreement (CRADA) with the National Cancer Institute (NCI). Actimab-A has demonstrated a mutation agnostic profile with positive clinical results in high-risk relapsed and refractory (r/r) AML patients including those with a TP53 gene mutation, prior Venetoclax treatment and prior bone marrow transplant (BMT).
The Actimab-A AACR (Free AACR Whitepaper) presentation is available for viewing on the Presentations& Webinars page of Actinium’s website HERE.
Title: Actimab-A (Lintuzumab-Ac-225) has potent mutation agnostic antileukemic activity in preclinical models of AML
Abstract Number: 594