| 16302795 |
Falgueyret JP, Desmarais S, Oballa R, Black WC, Cromlish W, Khougaz K, Lamontagne S, Masse F, Riendeau D, Toulmond S, Percival MD: Lysosomotropism of basic cathepsin K inhibitors contributes to increased cellular potencies against off-target cathepsins and reduced functional selectivity. J Med Chem. 2005 Dec 1;48(24):7535-43.
The lysosomal cysteine protease cathepsin K is a target for osteoporosis therapy. The aryl-piperazine-containing cathepsin K inhibitor CRA-013783/L-006235 (1) displays greater than 4000-fold selectivity against the lysosomal/endosomal antitargets cathepsin B, L, and S. However, 1 and other aryl-piperazine-containing analogues, including balicatib (10), are approximately 10-100-fold more potent in cell-based enzyme occupancy assays than against each purified enzyme. This phenomenon arises from their basic, lipophilic nature, which results in lysosomal trapping. Consistent with its lysosomotropic nature, 1 accumulates in cells and in rat tissues of high lysosome content. In contrast, nonbasic aryl-morpholino-containing analogues do not exhibit lysosomotropic properties. Increased off-target activities of basic cathepsin K inhibitors were observed in a cell-based cathepsin S antigen presentation assay. No potency increases of basic inhibitors in a functional cathepsin K bone resorption whole cell assay were detected. Therefore, basic cathepsin K inhibitors, such as 1, suffer from reduced functional selectivities compared to those predicted using purified enzyme assays. |
35(0,1,1,5) |