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Relugolix Meets Goals for Treating Advanced Prostate Cancer

Myovant’s drug would offer a new oral, once-daily treatment option

Relugolix met all key goals for treating advanced prostate cancer in the phase 3 HERO trial, setting up a 2020 FDA application by developer Myovant Sciences.

 Relugolix is a once-daily, oral gonadotropin-releasing hormone (GnRH) receptor antagonist that reduces testicular production of testosterone, the hormone mainly responsible for stimulating prostate cancer. If approved, relugolix would become the first oral GnRH antagonist for men with advanced prostate cancer.

Myovant said 96.7% of men receiving relugolix achieved sustained testosterone suppression to castrate levels (the primary endpoint). Responders achieved and maintained testosterone suppression to no more than 50 ng/dL from week 5 through week 48.

Five key secondary endpoints demonstrated superiority to leuprolide acetate, including rapid suppression of testosterone at day 4 and day 15, profound suppression of testosterone at day 15, rapid suppression of prostate-specific antigen at day 15, and suppression of follicle-stimulating hormone at week 24. In addition, relugolix demonstrated noninferiority to leuprolide acetate on sustained testosterone suppression through 48 weeks (96.7% versus 88.8%, respectively), the primary endpoint required for regulatory submissions outside the U.S. Pharmacodynamic results showed no testosterone flare after initiation of relugolix, and mean testosterone levels returned to normal within 90 days of treatment discontinuation.

The overall incidence of adverse events in the relugolix and leuprolide acetate groups was comparable (92.9% versus 93.5%, respectively). In the relugolix group, 3.5% of men discontinued the study early due to adverse events compared with 2.6% of men in the leuprolide acetate group. The most frequent adverse events were hot flashes, fatigue, constipation, diarrhea, and arthralgia. Unadjudicated major adverse cardiovascular events were reported in 2.9% of men with relugolix and 6.2% of men with leuprolide acetate.

HERO is a randomized, open-label, parallel-group, multinational clinical study designed to evaluate relugolix in men with androgen-sensitive advanced prostate cancer who require at least one year of continuous androgen deprivation therapy. Patients were randomized 2:1 to receive a single loading dose of relugolix 360 mg followed by relugolix 120 mg once daily, or to treatment with leuprolide acetate three-month depot injection.

Relugolix also reduces ovarian production of estradiol, a hormone known to stimulate the growth of uterine fibroids and endometriosis. Myovant is developing a combination tablet (relugolix 40 mg, estradiol 1.0 mg, and norethindrone acetate 0.5 mg) for women with heavy menstrual bleeding associated with uterine fibroids and for women with endometriosis-associated pain.

Source: Myovant Sciences, November 19, 2019

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