Alpha-Particle Emitting Atomic Generator (Actinium-225)-Labeled Trastuzumab (Herceptin) Targeting of Breast Cancer Spheroids

Abstract
Purpose: The humanized monoclonal antibody, trastuzumab (Herceptin), directed against HER2/neu, has been effective in the treatment of breast cancer malignancies. However, clinical activity has depended on HER2/neu expression. Radiolabeled trastuzumab has been considered previously as a potential agent for radioimmunotherapy. The objective of this study was to investigate the efficacy of trastuzumab labeled with the α-particle emitting atomic generator, actinium-225 (225Ac), against breast cancer spheroids with different HER2/neu expression levels. 225Ac has a 10-day half-life and a decay scheme yielding four α-particles.