title: Inhibition of hepatobiliary transporters by a novel kinase inhibitor contributes to hepatotoxicity in beagle dogs.
abstract: PF-022 (1) is a novel polycyclic benzothiophene kinase inhibitor selective for mitogen-activated protein kinase-activated protein kinase 2 (MK2). Compound 1 emerged as an inhibitor bearing submicromolar potency against MK2 (IC50 5 nM) and demonstrated projected human pharmacokinetics sufficient for oral dosing. However, following a single, oral administration of 1 to beagle dogs, animals experienced an acute liver injury characterized by increases in biomarkers associated with hepatotoxicity; particularly noteworthy was the reversible elevation in bile salts and total bilirubin. Accompanying this observation was an ADME appraisal which included hepatic bioactivation of 1 in multiple species and the in vitro inhibition of P-glycoprotein (P-gp; IC50 21 μM). Simply attenuating the bioactivation via structural modification proved ineffective in improving the in vivo tolerability of this polycyclic scaffold. Hence, disruption of hepatobiliary transporters by the compound series was hypothesized as the likely mechanism contributing to the acute hepatotoxicity. Indeed, closer in vitro examination employing transporter gene overexpressing MDCK cell lines and membrane vesicles revealed potent compound-dependent inhibition of human multi-drug resistance-associated protein 2 (MRP2/ABCC2; IC50 38 μM) and bile salt export pump (BSEP/ABCB11; IC50 10 μM), two crucial hepatobiliary transport proteins accountable for bilirubin and bile salt homeostasis, respectively. Subsequent introduction of pKa-altering modifications to a second generation compound PF029 proved successful in reducing its affinity for these key efflux transporters (MRP2 IC50 >>80 μM; BSEP IC50 > 70 μM; P-gp > 90 μM), consequently mitigating this overt organ toxicity in dogs.
authors.forename: John Scott
authors.initials: JS
authors.lastname: Daniels
authors.forename: Yurong
authors.initials: Y
authors.lastname: Lai
authors.forename: Sarah
authors.initials: S
authors.lastname: South
authors.forename: Po-Chang
authors.initials: PC
authors.lastname: Chiang
authors.forename: Daniel
authors.initials: D
authors.lastname: Walker
authors.forename: Bo
authors.initials: B
authors.lastname: Feng
authors.forename: Rouchelle
authors.initials: R
authors.lastname: Mireles
authors.forename: Laurence O
authors.initials: LO
authors.lastname: Whiteley
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: McKenzie
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Stevens
authors.forename: Robert
authors.initials: R
authors.lastname: Mourey
authors.forename: David
authors.initials: D
authors.lastname: Anderson
authors.affiliation: Drug Metabolism and Pharmacokinetics, Vanderbilt Center for Neuroscience Drug Discovery, Dept. of Pharmacology, Vanderbilt University Medical School, Nashville, TN 37232, USA. scott.daniels@vanderbilt.edu.
authors.forename: John W
authors.initials: JW
authors.lastname: Davis Ii
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D019540:Area Under Curve; D001646:Bile / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D002460:Cell Line; D056486:Chemical and Drug Induced Liver Injury / Q000473:pathology*; D004285:Dogs; D018432:Drug Resistance, Multiple; D005452:Fluoresceins / Q000493:pharmacokinetics; D005456:Fluorescent Dyes; D008099:Liver / Q000378:metabolism*; D008297:Male; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000633:toxicity*; D013656:Taurocholic Acid / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D005452:Fluoresceins; D005456:Fluorescent Dyes; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D047428:Protein Kinase Inhibitors; D013656:Taurocholic Acid; C000715087:ABCC2 protein, human; C085925:calcein AM