Actinium presents preclinical data for ATNM-400

Actinium Pharmaceuticals (ATNM) highlighted new preclinical data for ATNM-400, its novel, first-in-class antibody radioconjugate armed with the potent alpha-emitter Actinium-225, or Ac-225, at the 32nd Annual Prostate Cancer Foundation, or PCF, Scientific Retreat being held October 23 – 25, 2025 in Carlsbad, CA. ATNM-400, which targets a non-PSMA antigen associated with prostate cancer progression and treatment resistance, demonstrated superior tumor control and improved overall survival compared with the active agents in key standard-of-care therapies including enzalutamide, the active agent in Xtandi and 177Lu-PSMA-617, the active agent in Pluvicto, as well as 225Ac-PSMA-617 across multiple preclinical prostate cancer models. These data further reinforce ATNM-400’s potential as a paradigm changing, PSMA-independent Ac-225 alpha radiotherapy, offering opportunities for use as a monotherapy, in combination regimens, and in patients relapsing after ARPI or PSMA-directed treatments. ATNM-400 data has now been presented at the American Association for Cancer Research, Society for Nuclear Medicine and Molecular Imaging and PCF annual conferences in 2025 demonstrating its growing potential in various treatment settings in prostate cancer. In addition, data highlighting its potential in non-small cell lung cancer will be presented at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics on Saturday, October 25. Key Findings in Prostate Cancer Treatment Setting include: Potent and Durable Tumor Control, Increased Overall Survival and Synergistic Activity in Enzalutamide Resistant Prostate Cancer; ATNM-400 demonstrated superior and 5-times more durable anti-tumor efficacy extending to 100 days compared to approximately 20 days with enzalutamide alone. Given that ARPI therapies like enzalutamide are known to increase the ATNM-400 target antigen expression, combination treatment with ATNM-400 and enzalutamide was synergistic, resulting in complete tumor eradication in 40% of treated animals and significantly prolonged survival, whereas enzalutamide alone provided no durable disease control.