ESSA Pharma Inc. (EPIX) has made the difficult decision to discontinue its Phase 2 clinical trial evaluating the combination of masofaniten and enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC). This decision stems from an interim analysis of safety, pharmacokinetic (PK), and efficacy data, revealing a less-than-expected PSA90 response rate in patients receiving the combination therapy compared to those treated with enzalutamide alone.
The interim review, conducted according to the trial protocol, indicated that enzalutamide monotherapy, the standard of care for this patient population, resulted in a significantly higher PSA90 response rate than anticipated based on historical data. Furthermore, the analysis did not demonstrate a clear advantage in efficacy for the combination of masofaniten and enzalutamide over enzalutamide alone. A futility analysis also concluded that the trial had a low probability of achieving its primary endpoint.
While the combination therapy was well-tolerated and showed no new safety signals, with a safety profile similar to previous Phase 1 studies, the company believes that the observed efficacy profile of masofaniten combined with enzalutamide is unlikely to meet the trial’s primary endpoint or its internal requirements for a prostate cancer therapy candidate.
In a strategic move to prioritize its resources, ESSA Pharma is also terminating all remaining company-sponsored and investigator-sponsored clinical studies involving masofaniten, both as a single agent and in combination with other drugs.
As of September 30, 2024, ESSA Pharma had cash reserves and short-term investments of $126.8 million, along with net working capital of $124.3 million. This financial position will allow the company to focus on its remaining development programs and future strategic initiatives.
The news of the trial termination has had a significant impact on ESSA Pharma’s stock price, which plunged by 69.80% to $1.57 during the premarket session on Friday. This steep decline reflects the market’s disappointment with the trial’s outcome and its implications for the company’s future prospects.
