Bayer reports phase I results for prostate cancer therapy

Bayer announced results from its Phase I PAnTHa study evaluating ²²⁵Ac-PSMA-Trillium (BAY 3563254), an investigational targeted alpha therapy for patients with advanced metastatic castration-resistant prostate cancer.

The dose-escalation study identified an expansion dose, with at least 80% of patients achieving a PSA50 response at that dose level. Data were presented at the 2026 American Society of Clinical Oncology Genitourinary Cancers Symposium in San Francisco.

The study enrolled 50 patients across four dose levels, with 80% completing all four cycles of treatment administered intravenously every six weeks. No dose-limiting toxicities or treatment-related deaths occurred. Common treatment-emergent adverse events included dry mouth, fatigue and nausea.

Among patients with measurable disease at baseline, the overall response rate was 46% with a disease control rate of 83%. PSA50 and PSA90 response rates were 58% and 36% overall, and 83% and 58% respectively at the recommended dose for expansion.

²²⁵Ac-PSMA-Trillium is a targeted alpha therapy comprising a PSMA-targeting molecule with an albumin-binding component and actinium-225. The compound targets prostate-specific membrane antigen and is designed to increase tumor uptake.

Prostate cancer is the second most commonly diagnosed cancer in men, with median survival of less than three years among metastatic patients who have developed castration-resistance. The therapy represents part of Bayer's targeted alpha therapy development program.

The company stated the data support advancing the therapy to the next phase of clinical development, according to the press release.

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