Myovant's relugolix falls short in metastatic prostate cancer with FDA verdict looming

Last fall, Myovant’s prostate cancer drug outshone the standard of care at keeping patients’ testosterone levels down, a phase 3 showing that teed up an FDA filing. Now, as the agency ponders the case, the company is unveiling data for patients with metastatic disease—and they’re not so rosy.

The company pitted the drug, relugolix, against the standard of care, leuprolide, in 934 patients with advanced prostate cancer. Nearly all patients taking relugolix (97%) kept their testosterone levels down over 48 weeks, compared with 89% of patients taking leuprolide, Myovant reported last November. However, the drug staved off cancer progression at about the same rate as the incumbent in a subgroup of patients whose cancer had spread beyond the prostate, the new data show.

After 48 months, 74% of metastatic patients on relugolix were castration resistance-free, compared with 75% of patients on leuprolide. Prostate cancer that is castration-resistant keeps growing even when the amount of testosterone in the patient’s body is at very low levels. According to the National Cancer Institute, many early-stage prostate cancers need testosterone to grow, but castration-resistant cancers do not.

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Despite the disappointing showing in patients with metastatic disease, Myovant thinks relugolix could still unseat leuprolide in the broader population.

“We believe the totality of data–including previously reported data from the Phase 3 HERO program, published in the New England Journal of Medicine–presents compelling evidence for the potential use of relugolix in men with advanced prostate cancer,” Myovant CEO Lynn Seely, M.D., said in a statement Tuesday. “With our New Drug Application under Priority Review by the FDA, we look forward to our target action date in December 2020 and hope to advance our commitment to redefining care by bringing once-daily, oral relugolix to men with prostate cancer.”

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The FDA expects to decide relugolix’s fate by Dec. 20. Although it’s a pill that must be taken every day—unlike leuprolide, which is injected every three months—patients may prefer a drug they can get in the mail, versus having to travel to a hospital or clinic for treatment, Seely said in a previous interview.

Beyond prostate cancer, Myovant is seeking approval for relugolix as a treatment for uterine fibroids and endometriosis.