title: Disposition and metabolism of the cathepsin K inhibitor odanacatib in humans.
abstract: Odanacatib is a selective inhibitor of the cathepsin K enzyme that is expressed in osteoclasts involved in the degradation of bone organic matrix, and is being developed as a novel treatment of osteoporosis. Odanacatib has demonstrated increases in bone mineral density in postmenopausal women and is undergoing a pivotal phase III trial. The absorption, metabolism, and excretion of [(14)C]odanacatib were studied in healthy male volunteers (n = 6) after a single oral dose of 25 mg (100 µCi). Plasma, urine, and fecal samples were collected at intervals up to 34 days postdose. The pharmacokinetics of odanacatib were characterized by slow absorption (mean time to achieve maximum plasma concentration of 14.2 hours) and long apparent elimination half-life (mean t1/2 96.7 hours); 74.5% of the dose was recovered in feces and 16.9% in urine, resulting in a total recovery of 91.4%. Seven metabolites were identified in urine; the major pathway (methyl hydroxylation producing M8 and its derivatives) was largely dependent on CYP3A. Metabolites and odanacatib accounted for 77% and 23% of urinary radioactivity, respectively. In fecal extracts, the only radioactive components identified were odanacatib (60.9%) and M8 (9.5%). The fraction of odanacatib in feces derived from absorbed drug was estimated using a bioavailability value obtained from the results of a separate intravenous study. Collectively, the data indicate that odanacatib has a long t1/2 on account of its low metabolic intrinsic clearance, and that metabolism (principally mediated by CYP3A) and excretion of intact parent compound account for ∼70% and ∼30% of the clearance of odanacatib in humans.
authors.affiliation: Merck Research Laboratories, West Point, Pennsylvania (K.Ka., I.M., K.Ko., L.S., J.E.T., S.Z.); Merck Research Laboratories, Rahway, New Jersey (D.L.M., S.A.S.); and Covance Clinical Research, Madison, Wisconsin (R.D.).
authors.forename: Kelem
authors.initials: K
authors.lastname: Kassahun
authors.forename: Ian
authors.initials: I
authors.lastname: McIntosh
authors.forename: Kenneth
authors.initials: K
authors.lastname: Koeplinger
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Talaty
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Miller
authors.forename: Russell
authors.initials: R
authors.lastname: Dixon
authors.forename: Stefan
authors.initials: S
authors.lastname: Zajic
authors.forename: S Aubrey
authors.initials: SA
authors.lastname: Stoch
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000818:Animals; D001711:Biotransformation; D001713:Biphenyl Compounds / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D050071:Bone Density Conservation Agents / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D056657:Cathepsin K / Q000037:antagonists & inhibitors*; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005243:Feces / Q000737:chemistry; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008875:Middle Aged; D051381:Rats; D013379:Substrate Specificity; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D001713:Biphenyl Compounds; D050071:Bone Density Conservation Agents; D003577:Cytochrome P-450 Enzyme System; C534130:CTSK protein, human; D056657:Cathepsin K; C527128:odanacatib