said Tuesday after market close that a phase IIb study of an investigational osteoperosis drug showed dose-dependent increases in bone mineral density. Merck is initiating phase III studies.
The study used 10-, 25- and 50-mg doses of odanactib and involved 399 postmenopausal women with low bone mineral density. At the 50-milligram, once-weekly dose, odanactib increased lumbar spine bone mineral density (the primary endpoint) at 12 months by a significant 3.4% compared to baseline values, Merck said. In the placebo, the same metric decreased by 0.1% relative to baseline.
Odanactib is a highly selective inhibitor of the cathepsin K enzyme, which the company said is believed to play a role in osteoclastic bone resorption and in degrading the protein component of bone, and it is a different mechanism of action than currently approved treatments.
Shares closed Tuesday's regular session up $1.16, or 2.4%, at $50.57, but they fell 28 cents, or 0.6%, to $50.29 in after-hours trading.