Effect of novel N-cyano-tetrahydro-pyridazine compounds, a class of cathepsin K inhibitors, on the bone resorptive activity of mature osteoclasts.

Cathepsin K is the key regulator in the osteoclast-mediated bone resorption. Here, we found the correlation between the inhibitory activities of carbonitrile derivatives in the enzymatic activity of cathepsin K and their binding scores predicted using FlexX-Pharm docking program. The binding pattern of [1-(2-cyano-tetrahydro-pyridazine-1-carbonyl)-2-methy-propyl]-carbamic acid benzyl ester (8), one member of this series, was similar to that of the reference. In a bone pit formation assay, compound 8 was shown to dose-dependently inhibit the bone resorptive activity of mature osteoclasts.