title: Peptide aldehyde inhibitors of cathepsin K inhibit bone resorption both in vitro and in vivo.
abstract: We have shown previously that cathepsin K, a recently identified member of the papain superfamily of cysteine proteases, is expressed selectively in osteoclasts and is the predominant cysteine protease in these cells. Based upon its abundant cell type-selective expression, potent endoprotease activity at low pH and cellular localization at the bone interface, cathepsin K has been proposed to play a specialized role in osteoclast-mediated bone resorption. In this study, we evaluated a series of peptide aldehydes and demonstrated that they are potent cathepsin K inhibitors. These compounds inhibited osteoclast-mediated bone resorption in fetal rat long bone (FRLB) organ cultures in vitro in a concentration-dependent manner. Selected compounds were also shown to inhibit bone resorption in a human osteoclast-mediated assay in vitro. Chz-Leu-Leu-Leu-H (in vitro enzyme inhibition Ki,app = 1.4 nM) inhibited parathyroid hormone (PTH)-stimulated resorption in the FRLB assay with an IC-50 of 20 nM and inhibited resorption by isolated human osteoclasts cultured on bovine cortical bone slices with an IC-50 of 100 nM. In the adjuvant-arthritic (AA) rat model, in situ hybridization studies demonstrated high levels of cathepsin K expression in osteoclasts at sites of extensive bone loss in the distal tibia. Cbz-Leu-Leu-Leu-H (30 mg/kg, intraperitoneally) significantly reduced this bone loss, as well as the associated hind paw edema. In the thyroparathyriodectomized rat model, Cbz-Leu-Leu-Leu-H inhibited the increase in blood ionized calcium induced by a 6 h infusion of PTH. These data indicate that inhibitors of cathepsin K are effective at reducing osteoclast-mediated bone resorption and may have therapeutic potential in diseases of excessive bone resorption such as rheumatoid arthritis or osteoporosis.
authors.affiliation: Department of Cellular Biochemistry, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Votta
authors.forename: M A
authors.initials: MA
authors.lastname: Levy
authors.forename: A
authors.initials: A
authors.lastname: Badger
authors.forename: J
authors.initials: J
authors.lastname: Bradbeer
authors.forename: R A
authors.initials: RA
authors.lastname: Dodds
authors.forename: I E
authors.initials: IE
authors.lastname: James
authors.forename: S
authors.initials: S
authors.lastname: Thompson
authors.forename: M J
authors.initials: MJ
authors.lastname: Bossard
authors.forename: T
authors.initials: T
authors.lastname: Carr
authors.forename: J R
authors.initials: JR
authors.lastname: Connor
authors.forename: T A
authors.initials: TA
authors.lastname: Tomaszek
authors.forename: L
authors.initials: L
authors.lastname: Szewczuk
authors.forename: F H
authors.initials: FH
authors.lastname: Drake
authors.forename: D F
authors.initials: DF
authors.lastname: Veber
authors.forename: M
authors.initials: M
authors.lastname: Gowen
mesh_terms: D000447:Aldehydes / Q000494:pharmacology*; D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism; D001862:Bone Resorption; D002118:Calcium / Q000097:blood; D056657:Cathepsin K; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000235:genetics; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology*; D010281:Parathyroid Hormone / Q000494:pharmacology; D016105:Parathyroidectomy; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D013965:Thyroidectomy; D014407:Tumor Cells, Cultured
chemical_list: D000447:Aldehydes; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D010281:Parathyroid Hormone; D012333:RNA, Messenger; D011994:Recombinant Proteins; D002403:Cathepsins; C534130:CTSK protein, human; D056657:Cathepsin K; C534133:Ctsk protein, rat; D002118:Calcium