Our group aims to study α-particle RIT of human epidermal growth factor receptor-2 (HER2)-positive breast cancer (BC), particularly treatment of brain metastases (BM) by delivering trastuzumab (Herceptin) linked to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) complexed to 225Ac ([225Ac]Ac-DOTA-trastuzumab) to the brain. The gene discussed is ERBB2; the disease is breast cancer.