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A phase 2 study of MK-5442, a calcium-sensing receptor antagonist, in postmenopausal women with osteoporosis after long-term use of oral bisphosphonates.

Helen Hayes Hospital, West Haverstraw, NY, USA. cosmanf@helenhayeshosp.org. Department of Medicine, Columbia University, New York, NY, USA. cosmanf@helenhayeshosp.org. CGM Research Trust, The Princess Margaret Hospital Christchurch, Christchurch, New Zealand. Oregon Osteoporosis Center, Portland, OR, USA. Department of Orthopaedics, Hadassah Hebrew University Hospital, Jerusalem, Israel. Mediclinic Panorama, Cape Town, South Africa. Department of Obstetrics and Gynaecology, Faculty of Health, Sciences, Stellenbosch University, Stellenbosch, South Africa. Merck & Co, Inc., Kenilworth, NJ, USA.

Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA. 2016;(1):377-86
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Abstract

UNLABELLED In women with osteoporosis treated with alendronate for >12 months and oral bisphosphonates for >3 of the last 4 years, switching to MK-5442, a calcium receptor antagonist, stimulated endogenous parathyroid hormone (PTH) secretion and increased bone turnover marker levels, but produced a decline in bone mineral density (BMD) at all sites. INTRODUCTION This study assessed the effects of switching from long-term oral bisphosphonate therapy to the calcium-sensing receptor antagonist MK-5442 on BMD and bone turnover markers (BTMs) in post-menopausal women with osteoporosis. METHODS This randomized, active and placebo-controlled, dose-ranging study enrolled 526 postmenopausal women, who had taken alendronate (ALN) for ≥12 months preceding the trial and any oral bisphosphonate for ≥3 of the preceding 4 years and had spine or hip BMD T-scores ≤-2.5 or ≤-1.5 with ≥1 prior fragility fracture. Women were randomized to continue ALN 70 mg weekly or switch to MK-5442 (5, 7.5, 10, or 15 mg daily) or placebo. RESULTS Switching from ALN to MK-5442 produced a dose-dependent parathyroid hormone (PTH) pulse of threefold to sixfold above baseline at 1 h, with PTH levels that remained twofold to threefold above baseline at 4 h and returned to baseline by 24 h. Switching to MK-5442 or placebo increased BTM levels compared to baseline within 3 months and MK-5442 10 mg increased BTM levels compared to placebo by 6 months. With all MK-5442 doses and placebo, spine and hip BMD declined from baseline, and at 12 months, BMD levels were below those who continued ALN (all groups P < 0.05 vs ALN). There was also a dose-dependent increase in the incidence of hypercalcemia with MK-5442. CONCLUSION Switching from ALN to MK-5442 resulted in a pulsatile increase in PTH and increases in BTMs, but a decline in BMD compared with continued ALN. MK-5442 is not a viable option for the treatment of osteoporosis.

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