A Phase 3 trial evaluating Myovant Sciences’ relugolix as a treatment for advanced prostate cancer patients who are sensitive to androgen deprivation treatments has completed patient enrollment, the company announced.

The randomized trial, called HERO (NCT03085095), is examining if relugolix is better than standard treatment leuprolide acetate (marketed under the brand names Eligard and Lupron) at lowering testosterone levels to castrate levels — less than 50 nanograms per microliter.

It enrolled 934 patients at more than 180 clinical centers across North and South America, Europe, and the Asia-Pacific region.

“Completion of enrollment in HERO is a critical milestone for our prostate cancer program,” Lynn Seely, MD, president and CEO of Myovant, said in a press release. “We look forward to reporting top-line efficacy and safety data for HERO in the fourth quarter of 2019.”

Relugolix is an oral inhibitor of the gonadotropin-releasing hormone (GnRH) receptor that works to prevent the amount of sex hormones in circulation — estrogen in women and testosterone in men. It is being tested in women with uterine fibroids and endometriosis and in men with prostate cancer.

In two prior randomized Phase 2 trials (NCT02083185 and NCT02135445) that included 228 men with advanced prostate cancer, the treatment was able to lower testosterone levels to castrate levels and decrease prostate-specific antigen (PSA) levels.

Now researchers are testing the treatment in a larger Phase 3 trial.

In HERO, patients have been randomly assigned daily relugolix or leuprolide acetate, given into the muscle or under the skin every three months for up to 48 weeks.

In addition to measures of serum testosterone, researchers will also examine the treatment’s safety, conducting regular examinations of vital signs, physical and clinical tests, and electrocardiograms.

In the future, researchers are hoping that HERO’s results will provide the basis for relugolix’s approvals in the U.S., European Union, and Japan. If approved, it will become the first oral GnRH receptor antagonist approved to treat men with advanced prostate cancer.

In fact, according to Seely, “relugolix is the only oral gonadotropin-releasing hormone, or GnRH, receptor antagonist in development to lower testosterone and prostate-specific antigen, or PSA, in men with prostate cancer.”