Actinium Pharmaceuticals announces preclinical data for ATNM-400

Actinium Pharmaceuticals (ATNM) announced preclinical data for ATNM-400, a first-in-class Actinium-225 antibody radioconjugate, in hormone receptor positive, HER2 positive and triple-negative breast cancer that will be presented at the San Antonio Breast Cancer Symposium, SABCS, being held December10-14, 2025 in SanAntonio, Texas. The data demonstrates significant anti-tumor activity in breast cancer models resistant to standard-of-care therapies including endocrine therapy tamoxifen and HER2-targeted therapy trastuzumab as well as potent tumor growth inhibition in TNBC models. The data highlight ATNM-400’s potential to address critical unmet needs in patients who have exhausted treatment options following endocrine therapy or HER2-targeted therapy failure. These data add to ATNM-400’s robust preclinical data package that also encompasses metastatic castrate-resistant prostate cancer and non-small cell lung cancer.