ESSA Pharma has terminated the Phase II clinical trial of masofaniten, a new prostate cancer treatment.
Masofaniten, previously known as EPI-7386, is an investigational oral, small-molecule androgen receptor (AR) inhibitor.
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The decision to halt the trial, which was assessing masofaniten in combination with enzalutamide versus enzalutamide alone in patients with metastatic castration-resistant prostate cancer (mCRPC), was based on an interim review.
Agreed upon by the board of directors and senior management, the review indicated a higher-than-expected PSA90 response in patients treated solely with enzalutamide.
The Phase II trial was an open-label, two-arm, 2:1 randomised study which planned to enrol 120 patients.
At the time of the interim analysis, 52 patients had been enrolled and had at least one prostate-specific antigen (PSA) measurement post-baseline, with 41 patients having completed a minimum of three months follow-up.
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By GlobalDataAdditionally, no clear efficacy benefit was observed when masofaniten was combined with enzalutamide. A futility analysis suggested a low probability of achieving the prespecified primary endpoint.
ESSA Pharma president and CEO David Parkinson said: “We designed this randomised study to rigorously evaluate the clinical benefit of adding masofaniten to enzalutamide.
“We made the difficult decision to terminate this Phase II study following the interim analysis because we concluded that the emerging efficacy profile of masofaniten combined with enzalutamide would not likely meet the primary endpoint of the study, nor our internal requirements for a prostate cancer therapy candidate.
“We would like to thank our partners, investigators, employees, and most importantly, the patients and their families involved in our clinical trials.”
The trial included clinical sites in the US, Canada, Australia, and France. Its primary endpoint was the proportion of patients achieving a PSA90 response, with additional PSA-based secondary endpoints. However, the time-to-event parameters had not matured at the interim analysis.
Despite the trial’s termination, the combination of masofaniten and enzalutamide was found to be tolerated well, with a safety profile compatible with Phase I studies.
