An inhibitor of cathepsin K with potential anti-osteoporotic activity. Odanacatib selectively binds to and inhibits the activity of cathepsin K, which may result in a reduction in bone resorption, improvement of bone mineral density, and a reversal in osteoporotic changes. Cathepsin K, a tissue-specific cysteine protease that catalyzes degradation of bone matrix proteins such as collagen I/II, elastin, and osteonectin plays an important role in osteoclast function and bone resorption.