Relugolix, an oral gonadotropin-releasing hormone (GnRH) receptor antagonist, in women with endometriosis-associated pain: phase 2 safety and efficacy 24-week results.

Background: Relugolix is a once-daily, oral, nonpeptide, gonadotropin-releasing hormone receptor antagonist. The aim of this study was to evaluate safety of relugolix over 24 weeks in women with endometriosis-associated pain.

Methods: This phase 2, randomized, open-label, parallel-group extension study was conducted in 101 clinics in Japan. Patients (premenopausal females ≥ 20 years) who completed the preceding 12-week relugolix phase 2 study continued to receive relugolix (10 mg, 20 mg, or 40 mg), placebo, or leuprorelin (3.75 mg) for an additional 12 weeks. Relugolix was administered orally once daily, and leuprorelin subcutaneously once every 4 weeks. The primary outcome was safety, including bone mineral density (BMD) and treatment-emergent adverse events (TEAEs). Secondary endpoints included visual analog scale (VAS) scores for endometriosis-associated pain. Analysis sets were defined as all patients who were administered the study drug.

Results: Of 487 randomized patients in the preceding study, 397 enrolled in this extension study and continued to receive placebo (n = 77), relugolix 10 mg (n = 84), relugolix 20 mg (n = 78), relugolix 40 mg (n = 89), or leuprorelin (n = 69). Baseline characteristics were similar between extension study patients and patients in the preceding study. Frequency of TEAEs including metrorrhagia, menorrhagia, and hot flush was similar in the relugolix 40-mg and leuprorelin groups. Mean (SD) change in BMD from baseline at Week 24 was - 0.2 (1.99)% for placebo;  - 1.6 (2.34)%,  - 2.6 (2.94)%, and  - 4.9 (2.91)% for the relugolix 10-mg, 20-mg, and 40-mg groups, respectively; and - 4.4 (2.16)% for leuprorelin. Mean ± SD change from baseline in mean VAS score (mm) for pelvic pain at end of treatment was - 3.2 ± 12.16 for placebo; - 6.8 ± 10.56, - 9.0 ± 11.84, and - 11.9 ± 11.26 for the relugolix 10-mg, 20-mg, and 40-mg groups, respectively; and - 12.7 ± 12.57 for leuprorelin. Estradiol levels decreased with increasing relugolix dose and remained below postmenopausal levels throughout the 24-week relugolix 40-mg treatment period.

Conclusions: Treatment with relugolix for 24 weeks was generally well tolerated and demonstrated similar pain reduction to leuprorelin in women with endometriosis. The dose-dependent loss in BMD observed with relugolix treatment was expected due to an induced hypoestrogenic state. Relugolix demonstrated a similar benefit/risk profile to injectable therapy in this phase 2 study. Trial registration NCT01452685 (ClinicalTrials.gov, registered 17/10/2011).