Actinium Pharmaceuticals Inc. announced that new preclinical data for its lead antibody radioconjugate program, ATNM-400, will be presented at the 2025 San Antonio Breast Cancer Symposium (SABCS), scheduled for December 10-14, 2025. The data, to be presented in poster session 4 on December 11, will highlight the anti-tumor activity of ATNM-400 in tamoxifen- and trastuzumab-resistant breast cancer models. According to the company, preclinical results demonstrate efficacy of ATNM-400 as a monotherapy and in combination with standard-of-care therapies across breast cancer, prostate cancer, and non-small cell lung cancer models. The company states that these findings support further development of ATNM-400 in solid tumors, particularly in patient populations with resistance to current hormone and HER2-targeted therapies.