ISSN 2052-1219 (online)

Bone Abstracts (2016) 5 OC3.1 | DOI: 10.1530/boneabs.5.OC3.1

Effect of odanacatib on bone density and estimated bone strength in postmenopausal women: a CT-based sub-study of the phase 3 long-term odanacatib fracture trial (LOFT)

Bente Langdahl1, Tobias De Villiers2, Tony M Keaveny3, Klaus Engelke4, Harry Genant5, Shabana Ather6, Hilde Giezek6, Antonio Lombardi6, Albert Leung7 & Anne de Papp6

1Aarhus University Hospital, Aarhus, Denmark; 2Mediclinic Panorama and Department of Obestetrics & Gynaecology, University of Stellenbosch, Cape Town, South Africa; 3University of California & O.N Diagnostics, Berkeley, California, USA; 4Bioclinica-Synarc Germany, Hamburg, Germany; 5University of California, San Francisco, California, USA; 6Merck & Co., Inc., Kenilworth, New Jersey, USA; 7Formerly Merck & Co., Inc., Kenilworth, New Jersey, USA.

Odanacatib (ODN), a selective oral inhibitor of cathepsin K, is in development for the treatment of osteoporosis. In the Phase 3, Long-Term ODN Fracture Trial (LOFT; NCT00529373), ODN significantly reduced fracture risk. This imaging sub-study primarily investigated the effect of ODN on volumetric BMD (vBMD) of the lumbar spine (LS) and total hip (TH) using quantitative computed tomography (QCT).

Women aged ≥65 without baseline radiographic vertebral fracture (VFx) and TH or femoral neck (FN) BMD T-score <−2.5, or with prior VFx and TH or FN T-score <−1.5 and TH and FN T-score >−4.0, were randomised (1:1) to ODN 50 mg/week or placebo. All received vitamin D3 (5600 IU/week), and calcium. Endpoints included % change from baseline in LS trabecular vBMD (primary) and TH cortical vBMD (secondary) at 24 months. Additional QCT endpoints included % change from baseline in LS and TH trabecular, cortical and integral vBMD, integral TH BMC, and estimated whole-bone strength by finite element analysis (FEA) at 24 months.

In this sub-study, 164 women (78 ODN, 86 placebo) were enrolled. Treatment with ODN increased vBMD and BMC versus placebo at all sites, including LS trabecular vBMD (treatment difference [95% CI] 8.9 [3.9, 13.9]; P<0.001), TH cortical vBMD (2.8 [1.4, 4.1]; P<0.001), integral vBMD at LS (8.5 [5.7, 11.4]; P<0.001) and TH (5.3 [3.7, 7.0]; P<0.001), and TH integral BMC (5.1 [3.3, 6.8]) at 24 months. ODN numerically increased whole-bone estimated strength versus placebo at the L1 vertebra (mean % change from baseline [95% CI] 9.0 [6.0, 12.0] vs −0.8 [−4.2, 2.6]) and proximal femur (3.8 [2.3, 5.3] vs −3.1 [−4.4, −1.8]) at 24 months.

In postmenopausal women with osteoporosis, ODN compared with placebo increased trabecular, cortical and integral vBMD in the LS and TH, integral TH BMC, and whole-bone estimated strength at the spine and hip.