Efficacy and safety of ASP1707 for endometriosis-associated pelvic pain: the phase II randomized controlled TERRA study

STUDY QUESTION: Does the GnRH antagonist, ASP1707, reduce endometriosis-associated pelvic pain? SUMMARY ANSWER: ASP1707 significantly reduced endometriosis-associated pelvic pain in a dose-related manner WHAT IS KNOWN ALREADY: GnRH agonists are an effective therapeutic option for endometriosis that is refractory to non-steroidal anti-inflammatory drugs, oral contraceptives, and progestins. However, GnRH agonists cause complete suppression of estradiol (E2), resulting in hypoestrogenic side-effects such as bone loss that may increase the future risk of osteoporotic fractures. STUDY DESIGN, SIZE, DURATION: This was a Phase II, multicenter, double-blind, randomized, parallel-group, placebo-controlled study conducted in 540 women from 04 December 2012 to 30 July 2015 in Europe and Japan. A sample size of 504 (84 subjects per group) was calculated to provide >= 80% power to detect a dose-related treatment effect among placebo and ASP1707 doses in change from baseline in pelvic pain, assuming different dose-response curves after 12 weeks of treatment. PARTICIPANTS/MATERIALS, SETTING, METHODS: Of 912 women with endometriosis-associated pelvic pain screened, 540 were enrolled, and 532 received = 1 dose of study drug (placebo, n = 88; ASP1707 3 mg, n = 86; ASP1707 5 mg, n = 91; ASP1707 10 mg, n = 90; ASP1707 15 mg, n = 88; leuprorelin, n = 89) for 24 weeks. MAIN RESULTS AND THE ROLE OF CHANCE: After 12 weeks of treatment with ASP1707, the mean (95% CI) changes in numeric rating score (NRS) for overall pelvic pain (OPP) were -1.56 (-1.91, -1.21), -1.63 (-1.99, -1.27), -1.93 (-2.27, -1.60), -2.29 (-2.64, -1.94), and -2.13 (-2.47, -1.79) for placebo, ASP1707 3 mg, ASP1707 5 mg, ASP1707 10 mg, and ASP1707 15 mg, respectively. Mean (95% CI) changes in NRS for dysmenorrhea were -1.50 (-2.00, -1.00), -2.72 (-3.22, -2.21), -2.85 (-3.33, -2.38), -3.97 (-4.46, -3.48), and -4.18 (-4.66, -3.70), respectively. Mean (95% CI) changes in NRS for non-menstrual pelvic pain (NMPP) were -1.53 (-1.88, -1.19), -1.51 (-1.87, -1.16), -1.80 (-2.14, -1.47), -2.03 (-2.37, -1.68), and -1.86 (-2.20, -1.52), respectively. Statistically significant dose-related treatment effects in reduction in NRS for OPP (P = 0.001), dysmenorrhea (P < 0.001), and NMPP (P = 0.029) were observed after 12 weeks among ASP1707 doses and were maintained through 24 weeks. Serum estradiol and bone mineral density decreased dose dependently with ASP1707 through 24 weeks, however, to a lesser extent than with leuprorelin. LIMITATIONS, REASON FOR CAUTION: This study was not powered for pairwise comparison of each ASP1707 group versus placebo. WIDER IMPLICATIONS OF THE FINDINGS: All doses of ASP1707 reduced serum E2 levels to within the target range and to a lesser extent than leuprorelin. ASP1707 is a potential alternative treatment to leuprorelin for endometriosis-associated pelvic pain with lower impact on bone health.