IC50: 0.25 nM

L-006235 is a potent and selective inhibitor of Cathepsin K.

In vitro: After dilution of L-006235 to 0.05 nM, the cathepsin K enzyme activity was initially inhibited, but slowly recovered with a first-order rate constant of 0.023 s-1. The final steady-state enzyme activity was 80-90% that of control, suggesting the complete reversibility of the L-006235-cathepsin K complex. L-006235 was found to be not a substrate for the nitrilase activity of Cat K [1].

In vivo: L-006235 was orally bioavailable in rats, with a terminal half-life of over 3 h. L-006235 was orally dosed in ovariectomized rhesus monkeys once per day for 7 days. Results showed that collagen breakdown products were dose-dependently reduced by up to 76%. Plasma concentrations of L-006235 above the bone resorption IC50 after 24 h indicated a correlation between functional cellular and in vivo assays. These findings suggested that the inhibition of collagen breakdown by cathepsin K inhibitors, such as L-006235, might be useful in osteoporosis and other indications involving bone resorption [1].

Clinical trial: N/A

Reference:
[1] Palmer JT,Bryant C,Wang DX et al.  Design and synthesis of tri-ring P3 benzamide-containing aminonitriles as potent, selective, orally effective inhibitors of cathepsin K. J Med Chem.2005 Dec 1;48(24):7520-34.