FPI-2265 Phase 2 TATCIST Trial Interim Results Presented at AACR 2024

Fusion Pharmaceuticals, a clinical-stage oncology firm, has reported promising interim data from its Phase 2 TATCIST clinical trial. The study is assessing the efficacy of FPI-2265, an actinium-225 based radioconjugate, in treating patients with metastatic castration-resistant prostate cancer (mCRPC). The drug has shown activity in heavily pretreated patients, including those previously administered with lutetium-based radioconjugates.

The Phase 2 TATCIST trial, which is open-label, aims to evaluate the safety and efficacy of FPI-2265 in mCRPC patients. The trial includes those who have not been treated with PSMA-targeted radioconjugates and those who have received 177Lu-based PSMA radioconjugates like PLUVICTO™. As of March 1, 2024, 35 patients have been administered FPI-2265, with 25 having completed at least 12 weeks of follow-up.

The interim results, presented at the AACR Annual Meeting in San Diego, California, indicate that FPI-2265 has achieved a PSA50 response (a reduction of at least 50% in prostate-specific antigen levels within 12 weeks of the initial treatment) in 50% of the 20 efficacy-evaluable patients. Notably, the drug has been well-tolerated, with most adverse events being Grade 1-2, such as dry mouth, thrombocytopenia, anemia, fatigue, and dry eyes.

John Valliant, Ph.D., CEO of Fusion Pharmaceuticals, highlighted the significance of these results, stating that they validate the development path for FPI-2265 in mCRPC patients who have progressed after treatment with lutetium-based radioconjugates. The company is poised to initiate the Phase 2 portion of its registrational program for FPI-2265 in the second quarter of 2024, with a Phase 3 global trial expected to follow in 2025.

FPI-2265 is an innovative actinium-225 based radioconjugate that targets the prostate specific membrane antigen (PSMA). The use of alpha particles emitted by actinium-225 is considered a next-generation approach in cancer treatment, offering the potential for more potent cell-killing effects with targeted delivery and minimal damage to surrounding healthy tissue.

Fusion Pharmaceuticals is dedicated to the development of next-generation radioconjugates as precision medicines, selectively delivering alpha-emitting payloads to tumors. The company's lead program, FPI-2265, is a testament to its commitment to advancing novel treatments for mCRPC and solid tumors.

The interim data from the TATCIST trial suggest that FPI-2265 could offer a valuable therapeutic option for mCRPC patients, particularly those who have not responded to or have progressed after treatment with other radioconjugates. The company will continue to monitor the long-term outcomes of the patients involved in the TATCIST trial and prioritize the enrollment in the upcoming Phase 2 portion of the registrational program.