Selective Mechanism-Based Inactivation of CYP3A4 by CYP3cide (PF-04981517) and Its Utility as an In Vitro Tool for Delineating the Relative Roles of CYP3A4 versus CYP3A5 in the Metabolism of Drugs

• DOI: 10.1124/dmd.112.045302
• Publication Date: 2012-05-30T02:57:34Z
• Authors: Robert L. Walsky; R. Scott Obach; Ruth Hyland; Ping Kang; Sue Zhou; Michael West; Kieran F. Geoghegan; Christopher J. Helal; Gregory S. Walker; Theunis C. Goosen; Michael A. Zientek
• Keywords: CYP3A; Enzyme Kinetics; Mechanism of Action

CYP3cide (PF-4981517; 1-methyl-3-[1-methyl-5-(4-methylphenyl)-1<i>H</i>-pyrazol-4-yl]-4-[(3<i>S</i>)-3-piperidin-1-ylpyrrolidin-1-yl]-1<i>H</i>-pyrazolo[3,4-<i>d</i>]pyrimidine) is a potent, efficient, and specific time-dependent inactivator of human CYP3A4. When investigating its inhibitory properties, an extreme metabolic inactivation efficiency (<i>k</i>_inact/<i>K</i>_I) 3300 to 3800 ml · min⁻¹ μmol⁻¹ was observed using liver microsomes from donors nonfunctioning CYP3A5 (CYP3A5 *3/*3). This equated apparent <i>K</i>_I between 420 480 nM with maximal rate (<i>k</i>_inact) equal 1.6 min⁻¹. Similar results were achieved testosterone, another CYP3A substrate, other sources the CYP3A4 enzyme. To further illustrate abilities CYP3cide, partition ratio determined recombinant These studies produced approaching unity, thus underscoring capacity CYP3cide. tested at concentration preincubation time completely inhibit in library genotyped polymorphic microsomes, correlation remaining midazolam 1′-hydroxylase activity abundance significant (<i>R</i>² value 0.51, <i>p</i> &lt;0.0001). The work presented here supports these findings by fully characterizing properties exploring CYP3cide9s mechanism action. aid researcher, multiple commercially available established, protocol developed quantitatively determine contribution metabolism investigational compound. Through establishment this evidence provided here, we believe that very useful tool for understanding relative roles versus impact genetic polymorphism on compound9s pharmacokinetics.