title: Brain penetration of WEB 2086 (Apafant) and dantrolene in Mdr1a (P-glycoprotein) and Bcrp knockout rats.
abstract: Transporter gene knockout rat models are attracting increasing interest for mechanistic studies of new drugs as transporter substrates or inhibitors in vivo. However, limited data are available on the functional validity of such models at the blood-brain barrier. Therefore, the present study evaluated Mdr1a [P-glycoprotein (P-gp)], Bcrp, and combined Mdr1a/Bcrp knockout rat strains for the influence of P-gp and breast cancer resistance protein (BCRP) transport proteins on brain penetration of the selective test substrates [(14)C]WEB 2086 (3-[4-(2-chlorophenyl)-9-methyl-6H-thieno[3,2-f][1,2,4]triazolo-[4,3-a][1,4]-diazepin-2-yl]-1-(4-morpholinyl)-1-propanon) for P-gp and dantrolene for BCRP. Brain-to-plasma concentration ratios (BPR) were measured after intravenous coinfusions of 5.5 µmol/kg per hour [(14)C]WEB 2086 and 2 µmol/kg per hour dantrolene for 2 hours in groups of knockout or wild-type rats. Compared with wild-type controls, mean BPR of [(14)C]WEB 2086 increased 8-fold in Mdr1a knockouts, 9.5-fold in double Mdr1a/Bcrp knockouts, and 7.3-fold in zosuquidar-treated wild-type rats, but was unchanged in Bcrp knockout rats. Mean BPR of dantrolene increased 3.3-fold in Bcrp knockouts and 3.9-fold in double Mdr1a/Bcrp knockouts compared with wild type, but was unchanged in the Mdr1a knockouts. The human intestinal CaCo-2 cell bidirectional transport system in vitro confirmed the in vivo finding that [(14)C]WEB 2086 is a substrate of P-gp but not of BCRP. Therefore, Mdr1a, Bcrp, and combined Mdr1a/Bcrp knockout rats provide functional absence of these efflux transporters at the blood-brain barrier and are a suitable model for mechanistic studies on the brain penetration of drug candidates.
authors: Department of Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany (H.F., D.G.); Kobe Pharma Research Institute, Nippon Boehringer Ingelheim, Kobe, Japan (W.K., N.I.); and PKPharmaExpert, Laupheim, Germany (P.T.) holger.fuchs@boehringer-ingelheim.com.
authors: Holger
authors: H
authors: Fuchs
authors: Department of Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany (H.F., D.G.); Kobe Pharma Research Institute, Nippon Boehringer Ingelheim, Kobe, Japan (W.K., N.I.); and PKPharmaExpert, Laupheim, Germany (P.T.).
authors: Wataru
authors: W
authors: Kishimoto
authors: Department of Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany (H.F., D.G.); Kobe Pharma Research Institute, Nippon Boehringer Ingelheim, Kobe, Japan (W.K., N.I.); and PKPharmaExpert, Laupheim, Germany (P.T.).
authors: Dietmar
authors: D
authors: Gansser
authors: Department of Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany (H.F., D.G.); Kobe Pharma Research Institute, Nippon Boehringer Ingelheim, Kobe, Japan (W.K., N.I.); and PKPharmaExpert, Laupheim, Germany (P.T.).
authors: Paul
authors: P
authors: Tanswell
authors: Department of Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany (H.F., D.G.); Kobe Pharma Research Institute, Nippon Boehringer Ingelheim, Kobe, Japan (W.K., N.I.); and PKPharmaExpert, Laupheim, Germany (P.T.).
authors: Naoki
authors: N
authors: Ishiguro
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000172:deficiency* / Q000235:genetics; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000172:deficiency* / Q000235:genetics; D000818:Animals; D001381:Azepines / Q000097:blood / Q000493:pharmacokinetics*; D001921:Brain / Q000378:metabolism*; D018938:Caco-2 Cells; D003620:Dantrolene / Q000097:blood / Q000493:pharmacokinetics*; D003986:Dibenzocycloheptenes / Q000494:pharmacology; D055786:Gene Knockout Techniques; D006801:Humans; D008297:Male; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D014230:Triazoles / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C489249:Abcg2 protein, rat; D001381:Azepines; D003986:Dibenzocycloheptenes; D011804:Quinolines; D014230:Triazoles; C052518:WEB 2086; C095179:zosuquidar trihydrochloride; C095122:multidrug resistance protein 3; D003620:Dantrolene