Long-term Effect of Elagolix on Bone Mineral Density in Women with Endometriosis-Associated Pain [38G]

INTRODUCTION: To evaluate the long-term effect of elagolix, an oral, non-peptide GnRH antagonist, on bone mineral density (BMD) in two 6-month (M) extension studies (Elaris EM-III and IV) of the pivotal, 6M, phase 3 studies (12M overall treatment with 150mg once daily [QD] or 200mg twice daily [BID]). METHODS: Women with moderate/severe endometriosis-associated pain and a baseline BMD Z-score >-1.5 were randomized to receive elagolix in the pivotal studies and continued elagolix treatment in the extension studies (treated: Elaris EM-III, n=287; Elaris EM-IV, n=282). Total hip BMD was measured by dual energy X-ray absorptiometry and reviewed/evaluated by a blinded central reader. Baseline was before dosing in pivotal studies. RESULTS: After 6M of elagolix treatment in the pivotal studies, the proportion of women with a decrease in total hip BMD ≥8% ranged 0–1.1% across doses/studies; these women were not eligible for extension study. Following 12M treatment, the proportion of women with a total hip BMD decrease from baseline ≥8% was 1.8% (n=2) at 150mg QD and 0.9% (n=1) at 200mg BID in Elaris EM-III and 0% (n=0) at 150mg QD and 4.6% (n=5) at 200mg BID in Elaris EM-IV. For total hip, the mean BMD Z-score at extension-M6 was within the normal range of -2.0 to +2.0 across doses/studies; no women had a total hip BMD Z-score ≤-2. CONCLUSION: In women with endometriosis-associated pain, long-term elagolix treatment was associated with decreases in total hip BMD, while the mean total hip BMD Z-score was within the normal range and no women had a total hip BMD Z-score ≤-2.