Lysosomotropism of basic cathepsin K inhibitors contributes to increased cellular potencies against off-target cathepsins and reduced functional selectivity.
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.
Falgueyret
Jean-Pierre
JP
Department of Biochemistry, Merck Frosst Centre for Therapeutic Research, Kirkland, Quebec, Canada.
Desmarais
Sylvie
S
Oballa
Renata
R
Black
W Cameron
WC
Cromlish
Wanda
W
Khougaz
Karine
K
Lamontagne
Sonia
S
Massé
Frederic
F
Riendeau
Denis
D
Toulmond
Sylvie
S
Percival
M David
MD
D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects; D001345:Autoradiography; D001549:Benzamides / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D050071:Bone Density Conservation Agents / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D002401:Cathepsin B / Q000037:antagonists & inhibitors; D056657:Cathepsin K; D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors*; D002460:Cell Line; D003546:Cysteine Endopeptidases; D005260:Female; D006801:Humans; D008247:Lysosomes / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D009025:Morpholines / Q000737:chemistry / Q000494:pharmacology*; D010879:Piperazines / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D014018:Tissue Distribution
D001549:Benzamides; D050071:Bone Density Conservation Agents; C507712:CRA 013783; D009025:Morpholines; D010879:Piperazines; D013844:Thiazoles; C529767:balicatib; D002403:Cathepsins; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L; C534278:Ctsl protein, mouse; C534280:Ctsl protein, rat; C028217:cathepsin S; C534130:CTSK protein, human; D056657:Cathepsin K; C534132:Ctsk protein, mouse; C534133:Ctsk protein, rat