Essa Pharma’s sole clinical-stage candidate was on track to fall short against Xtandi in a phase 2 prostate cancer trial, leading the biotech to terminate the study, abandon the candidate and “review strategic options.”
The trial was evaluating the androgen receptor inhibitor, called masofaniten, in combination with Pfizer and Astellas’ blockbuster prostate cancer drug Xtandi versus Xtandi alone among 120 patients in the U.S., Canada, Australia and France with a metastatic castration-resistant form of the cancer. The primary endpoint was the proportion of patients who achieved a 90% or greater reduction in prostate-specific antigen (PSA90), a key biomarker for prostate cancer.
But, in a post-market release Thursday, Essa said it had terminated the trial after observing a “much higher rate of PSA90 response” in patients who received Xtandi monotherapy “than were expected based upon historical data.”
There was “no clear efficacy benefit” for the masofaniten-Xtandi combo when compared to Xtandi alone, the biotech added.
With a futility analysis determining “a low likelihood of meeting” the endpoint, Essa has moved to not only end the specific trial but also to terminate its other studies of masofaniten. Those studies were focused on various criteria of prostate cancer, testing the drug as either a monotherapy or in combination with the likes of Johnson & Johnson’s approved androgen receptor inhibitor Erleada.
With Essa’s remaining two assets—both AR N-terminal domain inhibitors—having yet to make it into the clinic, the company’s senior management and directors are now “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," Richard Glickman, chairman of the biotech’s board, said in a statement.
It's an abrupt hand brake stop for a company that as recently as the summer had been promising a “stream of significant milestones throughout the next nine to 12 months.” Essa’s situation echoes that of Oncternal Therapeutics, which last month culled its dual-action androgen receptor inhibitor after the therapy fell short in a phase 1 prostate cancer study.
Essa, which ended September with net working capital of $124.3 million, saw its stock sink 65% to $1.82 in premarket trading Friday morning from a Thursday closing price of $5.20.