title: Heterotropic activation of the midazolam hydroxylase activity of CYP3A by a positive allosteric modulator of mGlu5: in vitro to in vivo translation and potential impact on clinically relevant drug-drug interactions.
abstract: Allosteric modulation of G protein-coupled receptors has gained considerable attention in the drug discovery arena because it opens avenues to achieve greater selectivity over orthosteric ligands. We recently identified a series of positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu(5)) for the treatment of schizophrenia that exhibited robust heterotropic activation of CYP3A4 enzymatic activity. The prototypical compound from this series, 5-(4-fluorobenzyl)-2-((3-fluorophenoxy)methyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine (VU0448187), was found to activate CYP3A4 to >100% of its baseline intrinsic midazolam (MDZ) hydroxylase activity in vitro; activation was CYP3A substrate specific and mGlu(5) PAM dependent. Additional studies revealed the concentration-dependence of CYP3A activation by VU0448187 in multispecies hepatic and intestinal microsomes and hepatocytes, as well as a diminished effect observed in the presence of ketoconazole. Kinetic analyses of the effect of VU0448187 on MDZ metabolism in recombinant P450 or human liver microsomes resulted in a significant increase in V(max) (minimal change in K(m)) and required the presence of cytochrome b5. The atypical kinetics translated in vivo, as rats receiving an intraperitoneal administration of VU0448187 prior to MDZ treatment demonstrated a significant increase in circulating 1- and 4-hydroxy- midazolam (1-OH-MDZ, 4-OH-MDZ) levels compared with rats administered MDZ alone. The discovery of a potent substrate-selective activator of rodent CYP3A with an in vitro to in vivo translation serves to illuminate the impact of increasing intrinsic enzymatic activity of hepatic and extrahepatic CYP3A in rodents, and presents the basis to build models capable of framing the clinical relevance of substrate-dependent heterotropic activation.
authors.affiliation: Drug Metabolism and Pharmacokinetics Laboratory (A.L.B., T.M.B., F.W.B., R.D.M., J.S.D.), Medicinal Chemistry Laboratory (M.L.T., M.E.M., C.W.L., S.R.S.), and Molecular Pharmacology Laboratory (C.K.J., C.M.N., P.J.C.), Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, Tennessee; CREATe ADME/Tox, (C.M.), and Neuroscience (H.L., G.J.M., T.S.), Janssen Research and Development, Beerse, Belgium; and Jarama 75, Toledo, Spain (J.M.B.).
authors.forename: Anna L
authors.initials: AL
authors.lastname: Blobaum
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Bridges
authors.forename: Frank W
authors.initials: FW
authors.lastname: Byers
authors.forename: Mark L
authors.initials: ML
authors.lastname: Turlington
authors.forename: Margrith E
authors.initials: ME
authors.lastname: Mattmann
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Morrison
authors.forename: Claire
authors.initials: C
authors.lastname: Mackie
authors.forename: Hilde
authors.initials: H
authors.lastname: Lavreysen
authors.forename: José M
authors.initials: JM
authors.lastname: Bartolomé
authors.forename: Gregor J
authors.initials: GJ
authors.lastname: Macdonald
authors.forename: Thomas
authors.initials: T
authors.lastname: Steckler
authors.forename: Carrie K
authors.initials: CK
authors.lastname: Jones
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Niswender
authors.forename: P Jeffrey
authors.initials: PJ
authors.lastname: Conn
authors.forename: Craig W
authors.initials: CW
authors.lastname: Lindsley
authors.forename: Shaun R
authors.initials: SR
authors.lastname: Stauffer
authors.forename: J Scott
authors.initials: JS
authors.lastname: Daniels
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology*; D000818:Animals; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D004347:Drug Interactions / Q000502:physiology*; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000201:enzymology; D007654:Ketoconazole / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D008874:Midazolam / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D006899:Mixed Function Oxygenases; D051544:Cytochrome P-450 CYP3A; D008874:Midazolam; D007654:Ketoconazole