Fusion announces presentation of data from Phase 2 TATCIST clinical trial

Fusion Pharmaceuticals announced the presentation of interim efficacy and safety data from the Phase 2 TATCIST open-label clinical trial evaluating FPI-2265, at the American Association for Cancer Research, or AACR, Annual Meeting 2024 being held April 5-10 in San Diego, California. Results demonstrate that FPI-2265 is active in heavily pretreated patients with progressive metastatic castrate-resistant prostate cancer, mCRPC, including patients who received prior lutetium-based RCs. Safety, tolerability and clinical activity data were generally consistent with other published studies of small molecule-based 225Ac-PSMA RCs. The results are being presented at the AACR 2024 Annual Meeting in a poster presentation titled, “Preliminary efficacy and safety results from the TATCIST trial: A PSMA-directed targeted alpha therapy with FPI-2265 for the treatment of metastatic castration-resistant prostate cancer (mCRPC).” As of the March 1 data cutoff, 35 patients received at least one dose of FPI-2265, with 25 patients having at least 12 weeks of follow-up. The analysis included 25 patients for safety evaluation and 20 patients for assessing prostate-specific antigen, or PSA, response. Four participants were identified as superscan patients and were excluded from the efficacy analyses and reported separately in the safety analysis. One participant was not included in the efficacy analysis due to uninterpretable PSA response. Patients in the study were pretreated with a median of four prior lines of anticancer therapy, with 20 out of 25 receiving prior chemotherapy, including 10 patients who received at least two prior lines of taxanes. Nine out of 25 patients received a prior 177Lu-based PSMA RC. From the efficacy-evaluable patient population, PSA50 response was achieved in 10 out of 20 patients regardless of prior lutetium treatment. PSA50 was achieved in 61% of lutetium-naive participants and 42% of lutetium-treated participants. In an exploratory subset analysis of 13 patients, including six patients who received prior 177Lu-based PSMA RC treatment, with baseline PSMA Mean Standardized Uptake Value greater than6, PSA50 response was observed in nine patients.