ABSTRACT:Gemfibrozil more potently inhibits CYP2C9 than CYP2C8 in vitro, and yet the opposite inhibitory potency is observed in the clinic. To investigate this apparent paradox, we evaluated both gemfibrozil and its major metabolite, an acyl-glucuronide (gemfibrozil 1-O-␤-glucuronide) as direct-acting and metabolism-dependent inhibitors of the major drug-metabolizing cytochrome P450 enzymes (CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4) in human liver microsomes. Gemfibrozil most potently inhibited CYP2C9 (IC 50 of 30 M), whereas gemfibrozil glucuronide most potently inhibited CYP2C8 (IC 50 of 24 M). Unexpectedly, gemfibrozil glucuronide, but not gemfibrozil, was found to be a metabolism-dependent inhibitor of CYP2C8 only. The IC 50 for inhibition of CYP2C8 by gemfibrozil glucuronide decreased from 24 M to 1.8 M after a 30-min incubation with human liver microsomes and NADPH. Inactivation of CYP2C8 by gemfibrozil glucuronide required NADPH, and proceeded with a K I (inhibitor concentration that supports half the maximal rate of enzyme inactivation) of 20 to 52 M and a k inact (maximal rate of inactivation) of 0.21 min ؊1. Potent inhibition of CYP2C8 was also achieved by first incubating gemfibrozil with alamethicin-activated human liver microsomes and UDP-glucuronic acid (to form gemfibrozil glucuronide), followed by a second incubation with NADPH. Liquid chromatography-tandem mass spectrometry analysis established that human liver microsomes and recombinant CYP2C8 both convert gemfibrozil glucuronide to a hydroxylated metabolite, with oxidative metabolism occurring on the dimethylphenoxy moiety (the group furthest from the glucuronide moiety). The results described have important implications for the mechanism of the clinical interaction reported between gemfibrozil and CYP2C8 substrates such as cerivastatin, repaglinide, rosiglitazone, and pioglitazone.There have been several reports of clinical interactions between gemfibrozil (e.g., Lopid, Parke-Davis) and CYP2C8 substrates such as cerivastatin, repaglinide, rosiglitazone, and pioglitazone Niemi et al., 2003a,b;Jaakkola et al., 2005). Reports on the in vitro inhibitory potential of gemfibrozil demonstrated that this lipid-lowering drug is a more potent inhibitor of CYP2C9 than of CYP2C8 (Wen et al., 2001;Wang et al., 2002;Fujino et al., 2003). However, in the clinic, gemfibrozil is a more potent inhibitor of CYP2C8 than of CYP2C9. Coadministration of gemfibrozil with the CYP2C9 substrate warfarin does not increase the plasma concentrations of either R-or S-warfarin (in fact, it actually decreases them) (Lilja et al., 2005). An important step in providing a potential explanation for why gemfibrozil is a more potent inhibitor of CYP2C9 than CYP2C8 in vitro but is a more potent inhibitor of CYP2C8 than CYP2C9 in vivo was provided by Shitara et al. (2004), who demonstrated that gemfibrozil 1-O-␤-glucuronide is a more potent inhibitor than gemfibrozil of CYP2C8. These same authors demonstrated that gemfibrozil 1-O-␤-glucuronide inhibits in vitro the CYP2C8-mediated...

ABSTRACT:(2S,3R,4R,5S,6R)-2-(3-(4-Ethoxybenzyl)-4-chlorophenyl)-6-hydroxymethyl-tetrahydro-2H-pyran-3,4,5-triol (dapagliflozin; BMS-512148) is a potent sodium-glucose cotransporter type II inhibitor in animals and humans and is currently under development for the treatment of type 2 diabetes. The preclinical characterization of dapagliflozin, to allow compound selection and prediction of pharmacological and dispositional behavior in the clinic, involved Caco-2 cell permeability studies, cytochrome P450 (P450) inhibition and induction studies, P450 reaction phenotyping, metabolite identification in hepatocytes, and pharmacokinetics in rats, dogs, and monkeys. Dapagliflozin was found to have good permeability across Caco-2 cell membranes. It was found to be a substrate for P-glycoprotein (P-gp) but not a significant P-gp inhibitor. Dapagliflozin was not found to be an inhibitor or an inducer of human P450 enzymes. The in vitro metabolic profiles of dapagliflozin after incubation with hepatocytes from mice, rats, dogs, monkeys, and humans were qualitatively similar. Rat hepatocyte incubations showed the highest turnover, and dapagliflozin was most stable in human hepatocytes. Prominent in vitro metabolic pathways observed were glucuronidation, hydroxylation, and O-deethylation. Pharmacokinetic parameters for dapagliflozin in preclinical species revealed a compound with adequate oral exposure, clearance, and elimination half-life, consistent with the potential for single daily dosing in humans. The pharmacokinetics in humans after a single dose of 50 mg of [ 14 C]dapagliflozin showed good exposure, low clearance, adequate half-life, and no metabolites with significant pharmacological activity or toxicological concern.

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The discovery of BMS-605339 (35), a tripeptidic inhibitor of the NS3/4A enzyme, is described. This compound incorporates a cyclopropylacylsulfonamide moiety that was designed to improve the potency of carboxylic acid prototypes through the introduction of favorable nonbonding interactions within the S1' site of the protease. The identification of 35 was enabled through the optimization and balance of critical properties including potency and pharmacokinetics (PK). This was achieved through modulation of the P2* subsite of the inhibitor which identified the isoquinoline ring system as a key template for improving PK properties with further optimization achieved through functionalization. A methoxy moiety at the C6 position of this isoquinoline ring system proved to be optimal with respect to potency and PK, thus providing the clinical compound 35 which demonstrated antiviral activity in HCV-infected patients.