• First‑in‑human Phase 1 study evaluates HER3‑targeted ATNM‑400 in metastatic castration‑resistant prostate cancer population, including patients with and without prior PSMA‑directed therapy
   
• HER3‑targeted alpha radiotherapy offers a differentiated approach through a target distinct from PSMA and the potential to address treatment resistance across multiple solid tumors

NEW YORK, Oct. 23, 2026 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE:ATNM) (Actinium or the Company), a pioneer in differentiated targeted radiotherapies with the potential to transform cancer treatment, today announced that the first‑in‑human Phase 1 study of ATNM‑400, a HER3-targeted, non-PSMA radiotherapy, in metastatic castration‑resistant prostate cancer (mCRPC) will be featured at the European Society for Medical Oncology (ESMO) Congress 2026, taking place October 23⁠–⁠27, 2026, in Madrid, Spain.

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