– Relacatib (SB-462795) is a novel, potent, and orally active inhibitor of human cathepsins K, L, and V, exhibiting high affinity with Ki values of 41 pM, 68 pM, and 53 pM, respectively. It effectively inhibits endogenous cathepsin K in situ in human osteoclasts and human osteoclast-mediated bone resorption with IC50 values of 45 nM and 70 nM, respectively. In vitro studies confirm its inhibitory effect on bone resorption in human tissue, and in vivo studies on cynomolgus monkeys validate its efficacy in reducing bone resorption.