Cyp3a Induction by N-hydroxyformamide Tumor Necrosis Factor- Converting Enzyme/matrix Metalloproteinase Inhibitors: Use of a Pregnane X Receptor Activation Assay and Primary Hepatocyte Culture for Assessing Induction Potential in Humans

A series of N-hydroxyformamide tumor necrosis factorconverting enzyme (TACE)/matrix metalloprotease (MMP) inhibitors were evaluated for their potential to induce human cytochrome P450 3A (CYP3A). Two in vitro assays were used: 1) a cell-based reporter gene assay for activation of the pregnane X receptor (PXR), and 2) a primary “sandwich” culture of human hepatocytes. Approximately 50 TACE/MMP inhibitors were evaluated in the human PXR assay. A range of PXR activation was observed, 0 to 150% of the activation of the known human CYP3A inducer rifampicin. Three TACE/MMP inhibitors were evaluated in rat and human hepatocytes. Significantly higher PXR activation/CYP3A induction was observed in PXR/hepatocyte models, respectively, for (2R,3S) 3-(formyl-hydroxyamino)-2(2-methyl-1-propyl)-4-methylpentanoic acid [(1S,2S)-2-methyl-1-(2pyridylcarbamoyl)-1-butyl]amide (GW3333) compared with (2R,3S)6,6,6-trifluoro-3-[formyl(hydroxy)amino]-2-isobutyl-N-{(1S,2R)-2methoxy-1-[(1,3-thiazol-2-ylamino)carbonyl]propyl}hexanamide (GW6495) and (2R)-N-{(1S)-2,2-dimethyl-1-[(methylamino)carbonyl]propyl}-2-{(1S)-1-[formyl(hydroxy)amino]ethyl}-5-phenylpentanamide (GI4023). The CYP3A induction level achieved with GW3333 at a concentration of approximately 10 M in human hepatocytes was comparable to that achieved with rifampicin at a concentration of 10 M. The extent of rodent CYP3A induction caused by GW3333 was confirmed in vivo after daily oral administration for 14 days to rats. In conclusion, GW3333 is a potential inducer of CYP3A expression in vivo in humans, but other N-hydroxyformamides are less likely to induce CYP3A. Dual inhibition of tumor necrosis factorconverting enzyme (TACE) and matrix metalloprotease (MMP) enzymes by N-hydroxyformamide compound GW3333 has recently been shown to reduce the symptoms of arthritis in vivo in animal models (Conway et al., 2001). No data are currently available regarding the safety of this potential drug candidate or this structural class of TACE/MMP inhibitors in