Actinium Pharmaceuticals presents preclinical data for ATNM-400 breast cancer treatment.

Actinium Pharmaceuticals announced preclinical data for ATNM-400, a targeted radiotherapy, in hormone receptor positive, HER2 positive and triple-negative breast cancer. The data showed that ATNM-400 overcomes HER2 therapy resistance and has the potential to avoid off-target toxicities such as ILD. ATNM-400 also demonstrated the ability to overcome resistance to first-line tamoxifen endocrine therapy. The data will be presented at the San Antonio Breast Cancer Symposium on December 11, 2025.