Targeted alpha therapy with astatine-211-labeled anti-PSCA A11 minibody shows antitumor efficacy in prostate cancer xenografts and bone microtumors.

Evaluating fractionated α-RIT with 211At-labeled anti-PSCA A11 minibody, we found clear growth inhibition on both macrotumors and intratibial microtumors. For mice treated with multiple fractions, we also observed radiotoxicity manifested by progressive loss in body weight at 30 to 90 days after treatment. Our findings are conceptually promising for a systemic TAT of mCRPC and warrant further investigations of 211At-labeled PSCA-directed vectors. Such studies should include methods to improve the therapeutic window, e.g., by implementing a pretargeted regimen of α-RIT or by altering the size of the targeting vector.