Results of Phase I Study Reach Primary End Point for mCRPC

Scott T. Tagawa, MD, MS, professor of Medicine and Urology, and medical director of Genitourinary Oncology Research Program at Weill Cornell Medicine, discusses a phase I dose-escalation study of actinium-225 (225Ac-J591) in patients with progressive metastatic castration-resistant prostate cancer who had previously received at least 1 pathway inhibitor (NCT03276572).

The investigators of this trial did not reach a maximum tolerated dose, according to Tagawa. The study had 7 cohorts, and in 6 out of the 7, 1 patient had grade 4 anemia and thrombocytopenia. In the next cohort, none of the 6 patients had dose-limiting toxicities (DLTs), which were defined as grade 4 hematologic toxicity or grade 3/4 non-hematologic toxicity. Since none of these patients had DLTs, the study authors concluded that there was no maximum tolerated dose defined for this therapy. That cohorts received 93.3 KBq/kg which is now the recommended phase II dose.

Some adverse events that were not DLTs occurred with this therapy, such as grade 3 anemia in 1 patient and the rest were grade 1 and 2 toxicities.

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