ESSA Pharma Inc. has announced the termination of its Phase 2 clinical trial evaluating masofaniten in combination with enzalutamide for patients with metastatic castration-resistant prostate cancer (mCRPC) who are naïve to second-generation antiandrogens. The decision, effective October 31, 2024, was prompted by an interim analysis that revealed the combination therapy was unlikely to meet the primary endpoint of the study.
The Phase 2 trial (NCT05075577) was designed as an open-label, two-arm randomized study, with a 2:1 randomization, planning to enroll 120 patients. The trial compared masofaniten combined with enzalutamide against enzalutamide alone. The primary endpoint was the proportion of patients achieving a PSA90 response. The interim analysis included 52 patients with at least one PSA measurement and 41 patients with at least three months of follow-up.
The interim results indicated that the enzalutamide monotherapy arm performed better than historical controls, showing a higher rate of PSA90 response than anticipated. Specifically, the PSA90 response rate was 73% in the enzalutamide arm compared to 64% in the combination arm. The combination of masofaniten and enzalutamide did not demonstrate a clear efficacy benefit over enzalutamide alone. Masofaniten combined with enzalutamide was well-tolerated with no new safety signals and a safety profile similar to that seen in Phase 1 studies.
Strategic Implications
"Providing a meaningful clinical benefit to patients in our clinical trials, along with a robust safety profile, is of utmost importance to us at ESSA," said David Parkinson, MD, President and CEO. "We designed this randomized study to rigorously evaluate the clinical benefit of adding masofaniten to enzalutamide. We made the difficult decision to terminate this Phase 2 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."
As a result of this decision, ESSA Pharma will also terminate other ongoing clinical studies involving masofaniten, including combination studies with abiraterone acetate and apalutamide, as well as investigator-sponsored trials. The company plans to withdraw Investigational New Drug (IND) and Clinical Trial Applications (CTAs) in various regions.
Financial Position
As of September 30, 2024, ESSA Pharma reported cash reserves and short-term investments of $126.8 million and net working capital of $124.3 million. The company has no long-term debt facilities. ESSA Pharma will initiate a process to explore and review strategic options focused on maximizing shareholder value.
Richard Glickman, LLD, Chairman of the Board of Directors of ESSA, commented, "Senior management, together with the board of directors, are actively focused on preserving capital and will initiate a strategic process to explore and review a range of strategic options focused on maximizing shareholder value."
