Relugolix, an oral gonadotropin-releasing hormone receptor antagonist, reduces endometriosis-associated pain compared with leuprorelin in Japanese women: a phase 3, randomized, double-blind, noninferiority study

OBJECTIVE: To evaluate the efficacy and safety of 40-mg relugolix (REL) compared with those of leuprorelin (LEU) in women with endometriosis-associated pain. DESIGN: Phase 3, multicenter, randomized, double-blind, double-dummy, active-controlled study in Japanese patients. SETTING: Hospitals and clinics. PATIENT(S): Women aged ≥20 years with regular menstrual cycles (25-38 days) experiencing endometriosis or ovarian endometrioma and reporting pelvic pain. INTERVENTION(S): In the REL group, 40 mg of REL was orally administered once a day for 24 weeks. In the LEU group, 3.75 or 1.88 mg of LEU was subcutaneously injected every 4 weeks for 24 weeks. MAIN OUTCOME MEASURE(S): The primary endpoint was the change in the maximum visual analog scale score for pelvic pain from baseline until 28 days before the end of treatment. RESULT(S): Changes in the maximum visual analog scale score were -52.6 ± 1.3 for REL and -57.5 ± 1.4 for LEU. Ovarian endometrioma decreased by 12.26 ± 17.52 cm3 for REL and 14.10 ± 18.81 cm3 for LEU. Drug-related treatment emergent adverse events with an incidence of >10% for both groups were hot flush, metrorrhagia, headache, and genital hemorrhage. Discontinuations from treatment emergent adverse events were 2.9% for REL and 4.3% for LEU. CONCLUSION(S): Relugolix was noninferior to LEU for treating endometriosis-associated pelvic pain. Safety profiles of both medications were comparable, although menses returned earlier in patients taking REL, a huge benefit for women who plan to conceive after treatment. CLINICAL TRIAL REGISTRATION NUMBER: ClinicalTrials.gov: NCT03931915.