ESSA Pharma Announces Termination of Phase 2 Study Evaluating Masofaniten Combined with Enzalutamide in Patients with Metastatic Castration-Resistant Prostate Cancer

Efficacy signals observed will not achieve ESSA’s target product profile in patients with metastatic castration-resistant prostate cancer naïve to second-generation antiandrogens

A futility analysis conducted as part of a protocol-specified interim review of the safety, PK and efficacy data showed the single-agent enzalutamide control arm performing better than historical controls and similar to the combination of masofaniten and enzalutamide and therefore, unlikely to achieve the primary endpoint of the study 

Additional clinical studies with masofaniten including the combination study with abiraterone acetate and apalutamide as well as the remaining investigator sponsored trials will also be terminated and the IND and CTAs in different geographies will be withdrawn

Company will initiate a process to explore and review strategic options focused on maximizing shareholder value

Excerpt from the Press Release:

SOUTH SAN FRANCISCO, California and VANCOUVER, Canada, Oct. 31, 2024 /PRNewswire/ – ESSA Pharma Inc. (“ESSA”, or the “Company”) (NASDAQ: EPIX), a clinical-stage pharmaceutical company focused on developing novel therapies for the treatment of prostate cancer, today announced that it has made the decision to terminate the Phase 2 clinical trial evaluating in a 2:1 randomization masofaniten combined with enzalutamide versus enzalutamide single agent in patients with metastatic castration-resistant prostate cancer (“mCRPC”) naïve to second-generation antiandrogens. This decision, mutually agreed upon by both senior management and the board of directors, was based on a protocol-specified interim review of the safety, PK and efficacy data, which showed a much higher rate of PSA90 response in patients treated with enzalutamide monotherapy (which is standard of care for this patient population) than were expected based upon historical data. In addition, there was no clear efficacy benefit seen with the combination of masofaniten plus enzalutamide compared to enzalutamide single agent. A futility analysis determined a low likelihood of meeting the prespecified primary endpoint of the study. The combination of masofaniten plus enzalutamide was well-tolerated with no new safety signals and a safety profile similar to that seen in Phase 1 studies.

“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. We would like to thank our partners, investigators, employees, and most importantly, the patients and their families involved in our clinical trials.”

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.”

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