Exposure-Safety Analyses Identify Predictors of Change in Bone Mineral Density and Support Elagolix Labeling for Endometriosis-Associated Pain.

Elagolix is a novel oral gonadotropin releasing hormone receptor antagonist, that can suppress estradiol in a dose-dependent manner. It is indicated for management of moderate to severe pain associated with endometriosis. A population exposure-response model describing the relationship between elagolix exposure and changes in bone mineral density (BMD) was developed using data from four Phase 3 studies in premenopausal women with endometriosis-associated pain. Elagolix pharmacokinetic exposure-dependent changes in BMD were described by an indirect-response Emax model through stimulation of bone resorption. African American race, higher body mass index (BMI), and lower type-I collagen C-telopeptide concentrations were significantly associated with higher baseline BMD. Higher BMI was significantly associated with higher bone formation rates. Simulations using the final model demonstrated that elagolix 150 mg QD dosing for 24 months is predicted to result in -1.45% (-2.04, -0.814) decrease from baseline in BMD and were used to support corresponding dosing recommendations in the label.