title: P-glycoprotein plays a role in the oral absorption of BMS-387032, a potent cyclin-dependent kinase 2 inhibitor, in rats.
abstract: OBJECTIVE
  BMS-387032, a novel cyclin-dependent kinase 2 inhibitor, is currently in phase I clinical trials for anticancer therapy. The oral bioavailability of BMS-387032 has been found to be about 31% in rats. Absorption and first-pass metabolism were evaluated as possible reasons for the incomplete oral bioavailability in rats.
  
  
  METHODS
  Male Sprague-Dawley rats were given single doses of BMS-387032 intraarterially (9.1 mg/kg), orally (9.1 mg/kg), or intraportally (10 mg/kg). The routes of excretion of BMS-387032 after intravenous dosing were investigated in bile-duct-cannulated rats. The rate of metabolism of BMS-387032 was investigated in liver microsomes. The permeability of BMS-387032 was evaluated using Caco-2 cells, an in vitro model of the intestinal epithelium. To determine if BMS-387032 was a P-glycoprotein substrate, brain uptake studies were conducted in P-glycoprotein knockout versus wildtype mice.
  
  
  RESULTS
  The exposure in rats after an intraportal dose was similar to that after an intraarterial dose, indicating that absorption may play a greater role than liver first-pass metabolism in the low oral bioavailability seen in rats. After an intravenous dose, the percent of dose excreted unchanged in the urine and bile over a 9-h period was 28% and 11%, respectively. In vitro studies in rat liver microsomes showed low rates of metabolism of BMS-387032. The Caco-2 cell permeability of BMS-387032 was <15 nm/s in the apical to basolateral direction, and 161 nm/s in the basolateral to apical direction, indicating that it may be a substrate for an intestinal efflux transporter. A P-glycoprotein binding assay showed that BMS-387032 might be a P-glycoprotein modulator. Brain penetration studies in mice showed brain levels of BMS-387032 about 3.5-fold higher in P-glycoprotein knockout mice than in wildtype mice, providing evidence of BMS-387032 being a P-glycoprotein substrate.
  
  
  CONCLUSIONS
  Poor absorption may be playing a greater role than extensive first-pass metabolism in the incomplete oral bioavailability of BMS-387032 seen in rats. The efflux transporter, P-glycoprotein, may be responsible for limiting absorption, as BMS-387032 appears to be a substrate of P-glycoprotein.
authors.affiliation: Department of Metabolism and Pharmacokinetics, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543, USA. amrita.kamath@bms.com
authors.forename: Amrita V
authors.initials: AV
authors.lastname: Kamath
authors.forename: Saeho
authors.initials: S
authors.lastname: Chong
authors.forename: Ming
authors.initials: M
authors.lastname: Chang
authors.forename: Punit H
authors.initials: PH
authors.lastname: Marathe
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology*; D000042:Absorption; D000818:Animals; D001682:Biological Availability; D001921:Brain / Q000378:metabolism; D018938:Caco-2 Cells; D018797:Cell Cycle Proteins / Q000493:pharmacokinetics*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004285:Dogs; D006801:Humans; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D010080:Oxazoles / Q000493:pharmacokinetics*; D019920:Photoaffinity Labels; D051381:Rats; D017207:Rats, Sprague-Dawley; D013844:Thiazoles / Q000493:pharmacokinetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; C493958:Cdkn1a protein, rat; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C484864:N-(5-(((5-(1,1-dimethylethyl)-2-oxazolyl)methyl)thio)-2-thiazolyl)-4-piperidinecarboxamide; D010080:Oxazoles; D019920:Photoaffinity Labels; D013844:Thiazoles