title: P450-mediated O-demethylated metabolite is responsible for rat hepatobiliary toxicity of pyridyltriazine-containing PI3K inhibitors.
abstract: The dysregulation of phosphatidylinositol 3-kinase (PI3K)-dependent pathways is implicated in several human cancers making it an attractive target for small molecule PI3K inhibitors. A series of potent pyridyltriazine-containing inhibitors of class Ia PI3Ks were synthesized and a subset of compounds was evaluated in exploratory repeat-dose rat toxicology studies. Daily oral dosing of compound 1: in Sprague Dawley rats for four consecutive days was associated with hepatobiliary toxicity that included biliary epithelial hyperplasia and hypertrophy, periductular edema, biliary stasis, and acute peribiliary inflammatory infiltrates. These histological changes were associated with clinical pathology changes that included increased serum liver enzymes, total bile acids, and bilirubin. The predominant clearance pathway of 1: was shown in vitro and in a bile-duct cannulated rat (14)C-ADME study to be P450-mediated oxidative metabolism. An O-demethylated pyridine metabolite, M3: , was identified as a candidate proximal metabolite that caused the hepatotoxicity. Co-administration of the pan-P450 inhibitor 1-aminobenzotriazole with 1: to rats significantly reduced the formation of M3: and prevented liver toxicity, whereas direct administration of M3: reproduced the toxicity. Structural changes were introduced to 1: to make the methoxypyridine ring less susceptible to P450 oxidation (compound 2: ), and addition of a methyl group to the benzylic carbon (compound 3: ) improved the pharmacokinetic profile. These changes culminated in the successful design of a clinical candidate 3: (AMG 511) that was devoid of liver toxicity in a 14-day rat toxicity study. Herein, we describe how a metabolism-based structure-activity relationship analysis allowed for the successful identification of a PI3K inhibitor devoid of off-target toxicity.
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320 rajus@amgen.com.
authors.forename: Raju
authors.initials: R
authors.lastname: Subramanian
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Divesh
authors.initials: D
authors.lastname: Aidasani
authors.affiliation: Comparative Biology and Safety Sciences, Amgen Inc., Seattle, Washington 98119 rajus@amgen.com.
authors.forename: Keith
authors.initials: K
authors.lastname: Bailey
authors.affiliation: Comparative Biology and Safety Sciences, Amgen Inc., Seattle, Washington 98119.
authors.forename: Dan
authors.initials: D
authors.lastname: Branstetter
authors.affiliation: Comparative Biology and Safety Sciences, Amgen Inc., Seattle, Washington 98119.
authors.forename: Nancy
authors.initials: N
authors.lastname: Everds
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Jian
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Medicinal Chemistry, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Norman
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Ronya
authors.initials: R
authors.lastname: Primack
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Gary L
authors.initials: GL
authors.lastname: Skiles
authors.affiliation: Comparative Biology and Safety Sciences, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Irene
authors.initials: I
authors.lastname: Soto
authors.affiliation: Medicinal Chemistry, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Markian M
authors.initials: MM
authors.lastname: Stec
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Mylo
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Pharmaceutics and Pre-formulation, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Tian
authors.initials: T
authors.lastname: Wu
authors.affiliation: Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, California 91320.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Comparative Biology and Safety Sciences, Amgen Inc., Seattle, Washington 98119.
authors.forename: Hervé
authors.initials: H
authors.lastname: Lebrec
mesh_terms: D000818:Animals; D001659:Biliary Tract / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology / Q000209:etiology* / Q000473:pathology; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D013058:Mass Spectrometry; D008657:Metabolic Clearance Rate; D008745:Methylation; D015394:Molecular Structure; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity*; D017207:Rats, Sprague-Dawley; D054852:Small Molecule Libraries / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity*; D014018:Tissue Distribution; D018675:Toxicity Tests; D014227:Triazines / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines; D054852:Small Molecule Libraries; D014227:Triazines; D003577:Cytochrome P-450 Enzyme System
keywords: P450 mediated metabolite; PI3K inhibitors; hepatotoxicity; mechanistic ADME