Background:

Balicatib is an inhibitor of cathepsin K with IC50 value of 1.4nM [1].

Balicatib is highly selective against cathepsin K over cathepsin B, L and S in the in vitro enzyme assay. However, the selectivity is not so high in cell-based enzyme assay. The lysosomotropic character of balicatib results in its accumulation in lysosomes and the subsequent nonselective off-target effects. The off-target effects also cause the skin adverse events of balicatib [1, 2].

As a cathepsin K inhibitor, balicatib is developed for osteoporosis. It has been reported to reduce the biochemical markers of bone resorption and increase bone mineral density in ovariectomized monkeys. In addition, balicatib shows benefits in new bone formation of postmenopausal women [2].

参考文献:
[1] Black WC. Peptidomimetic inhibitors of cathepsin K. 2010;10(7):745-51.
[2] Br?mme D, Lecaille F. Cathepsin K inhibitors for osteoporosis and potential off-target effects. Expert Opin Investig Drugs. 2009 May;18(5):585-600.