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TAT-10: Ac225-PSMA-617: PSMA Targeting Alpha-Radiation Therapy of Patients with mCRPC

Kanazawa, Japan (UroToday.com) A preliminary study was undertaken to establish the dosage and treatment intervals for Ac225-PSMA-617 treatment for metastatic castration resistant prostate cancer (mCRPC). Fourteen patients were recruited and all had previously received the standard care of androgen deprivation therapy and chemotherapy. Dosimetry estimates were computed from Lu177-PSMA-617 scans.

Maximum tumor uptake was observed after several hours and retained for several days—a good match to the Ac225 half life.  Treatment doses of Ac225-PSMA-617 ranged from 50-200 kBq/kg and dose intervals from 2-4 months. Treatment failure (death or rising PSA) was observed at the lowest dose and severe xerostomia was the limiting factor at higher doses. Based on these data, a standard treatment of 100 kBq/kg every two months was chosen for the second trial.

Twenty eight patients were recruited for the second phase. Eight of these dropped out early (5 due to xerostomia, 3 due to early progression). Of the 20 patients who completed the standard treatment, 19 showed a PSA drop at 8 weeks. Four patients showed complete remission. Based on these results, Ac225-PSMA-617 is a very promising potential therapy for mCRPC patients, especially if ways could be found to ameliorate the side effects to the salivary glands.

Presented By: Alfred Morgenstern from European Commission, Joint Research Center, Directorate for Nuclear Safety and Security, Karlsruhe, Germany

Written By: William Carithers, Lawrence Berkeley National Laboratory

at the 10th International Symposium on Targeted Alpha Therapy (TAT-10)  May 31 - June 1, 2017 - Kanazawa, Japan.