Dec. 12 at 5:10 PM
Actinium Pharmaceuticals presented new preclinical data for its breast-cancer candidate ATNM-400 at the 2025 San Antonio Breast Cancer Symposium. The Actinium-225–based radioimmunoconjugate showed strong antitumor activity across multiple breast-cancer models—including hormone-receptor–positive, triple-negative, and treatment-resistant tumors—by targeting an antigen highly overexpressed in resistant cells.
ATNM-400 produced significant tumor-growth inhibition with a favorable tolerability profile, driven by the therapy’s alpha-emitter payload, which induced irreversible DNA double-strand breaks and offered focused tumor killing with reduced off-target toxicity compared with traditional antibody-drug conjugates. Actinium is positioning the therapy as a potential pan-tumor targeted radiotherapy that could address hard-to-treat breast-cancer subtypes, with prior data also supporting potential in prostate and non-small-cell lung cancer.
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