Safety and Efficacy of the Cathepsin K Inhibitor ONO-5334 in Postmenopausal Osteoporosis: The OCEAN Study

Osteoporosis occurs when there is an imbalance between resorption and formation of bone, with resorption predominating. Inhibitors of cathepsin K may rebalance this condition. This is the first efficacy study of a new cathepsin K inhibitor, ONO-5334. The objective of the study was to investigate the efficacy and safety of ONO-5334 in postmenopausal osteoporosis. This was a 12-month, randomized, double-blind, placebo-and active-controlled parallel-group study conducted in 13 centers in 6 European countries. Subjects included 285 postmenopausal women aged 55 to 75 years with osteoporosis. Subjects were randomized into one of five treatment arms: placebo; 50mg twice daily, 100mg once daily, or 300mg once daily of ONO-5334; or alendronate 70mg once weekly. Lumbar spine, total hip, and femoral neck BMD values were obtained along with biochemical markers of bone turnover and standard safety assessments. All ONO-5334 doses and alendronate showed a significant increase in BMD for lumbar spine, total hip ( except 100mg once daily), and femoral neck BMD. There was little or no suppression of ONO-5334 on bone-formation markers compared with alendronate, although the suppressive effects on bone-resorption markers were similar. There were no clinically relevant safety concerns. With a significant increase in BMD, ONO-5334 also demonstrated a new mode of action as a potential agent for treating osteoporosis. Further clinical studies are warranted to investigate long-term efficacy as well as safety of ONO-5334. (C) 2011 American Society for Bone and Mineral Research.