Bone Density, Turnover, and Estimated Strength in Postmenopausal Women Treated With Odanacatib: A Randomized Trial

Context: Odanacatib, a cathepsin K inhibitor, increases spine and hip areal bone mineral density (BMD) in postmenopausal women with low BMD and cortical thickness in ovariectomized monkeys. Objective: The objective of the study was to examine the impact of odanacatib on the trabecular and cortical bone compartments and estimated strength at the hip and spine. Design: This was a randomized, double-blind, 2-year trial. Setting: The study was conducted at a private or institutional practice. Participants: Participants included 214 postmenopausal women with low areal BMD. Intervention: The intervention included odanacatib 50 mg or placebo weekly. Main Outcome Measures: Changes in areal BMD by dual-energy x-ray absorptiometry (primary end point, 1 year areal BMD change at lumbar spine), bone turnover markers, volumetric BMD by quantitative computed tomography (QCT), and bone strength estimated by finite element analysis were measured. Results: Year 1 lumbar spine areal BMD percent change from baseline was 3.5% greater with odanacatib than placebo (P < .001). Bone-resorption marker C-telopeptide of type 1 collagen was significantly lower with odanacatib vs placebo at 6 months and 2 years (P < .001). Bone-formation marker procollagen I N-terminal peptide initially decreased with odanacatib but by 2 years did not differ from placebo. After 6 months, odanacatib-treated women had greater increases in trabecular volumetric BMD and estimated compressive strength at the spine and integral and trabecular volumetric BMD and estimated strength at the hip (P < .001). At the cortical envelope of the femoral neck, bone mineral content, thickness, volume, and cross-sectional area also increased from baseline with odanacatib vs placebo (P < .001 at 24 months). Adverse experiences were similar between groups. Conclusions: Over 2 years, odanacatib decreased bone resorption, maintained bone formation, increased areal and volumetric BMD, and increased estimated bone strength at both the hip and spine.