It plans two trials that investigate the safety and effectiveness of relugolix, with or without supporting low-dose hormone treatment, in about 600 women. The studies will be called SPIRIT 1 and SPIRIT 2.
“Endometriosis is a very common and debilitating estrogen-driven disease that occurs in around 10 percent of pre-menopausal women,” Dr. Linda C. Giudice, a reproductive endocrinologist at the University of California, San Francisco School of Medicine, said in a press release.
“Women with moderate to severe endometriosis-associated pain are in great need of well-tolerated medicines to help ease their pain and provide a treatment alternative to invasive procedures such as laparoscopy and hysterectomy [surgery],” she added.
Earlier trials showed that relugolix lowers endometriosis pain. It reduces levels of the female hormone estrogen by blocking gonadotropin-releasing hormone (GnRH). Studies have linked high estrogen levels to endometriosis.
A Phase 2 trial reporting that relugolix reduced pelvic pain in women with endometriosis allowed relugolix to advance to Phase 3 studies.
Women aged 18 to 50 will be eligible to participate in the new trials, which will randomly assign participants to one of three treatment groups.
One will receive 40-mg tablets of relugolix once a day, together with low-dose hormone therapy: 1 mg of estradiol and 0.5 mg of norethindrone acetate. The treatment will last 24 weeks.
The second group will receive 40 mg of relugolix once a day without add-on hormone therapy for 12 weeks. Researchers will then add hormone treatment for 12 weeks. The third group will receive a placebo for 24 weeks.
Patients who complete the first stage of the study will be offered relugolix and hormone treatment for 28 weeks more. The total treatment period will then add up to 52 weeks.
While researchers will assess the effectiveness of the treatment after 24 weeks, the aim of the extension portion of the trials is to evaluate the drug’s safety longer term.
The team will explore if the treatment lowers both menstrual and non-menstrual pelvic pain. The two measurements make up the trials’ two primary objectives, or endpoints.
Because all estrogen-lowering drugs reduce the mineral content of bones, safety assessments will include bone mineral density measurements. Researchers will use a method called dual-energy x-ray absorptiometry to make the measurements.
“With the initiation of the SPIRIT program, Myovant will be running five ongoing Phase 3 trials for relugolix in three critical areas of unmet medical need,” said Dr. Lynn Seely, Myovant’s president and chief executive officer.
“I could not be prouder of the dedication and resourcefulness shown by our entire team in achieving our ambitious development timelines,” she added.
In addition to endometriosis-related pain, Myovant is evaluating relugolix as a pain-relieving medication in Phase 3 trials involving women with uterine fibroids and men with advanced prostate cancer.