Abstract
Human pregnane X receptor (hPXR) is a nuclear receptor that regulates the expression of phase I and phase II drug-metabolism enzymes, as well as that of drug transporters. hPXR is a "xenobiotics sensor" and can be activated by structurally diverse compounds. The activation of hPXR by its agonists increases the clearance of xenobiotics by increasing the expression of drug-metabolism enzymes and drug transporters, possibly leading to drug toxicity, drug resistance, and other adverse drug reactions. Therefore, hPXR antagonists might attenuate agonist-mediated activation of hPXR and reduce the risk of adverse drug reactions. Several hPXR antagonists have been reported, but none of them is specific for hPXR. In this study, we present the first large-scale, unbiased, cell-based high-throughput screen to identify specific hPXR antagonists. Among the 132,975 compounds screened, we identified the 1,4,5-substituted 1,2,3-triazole analogs as potent and specific hPXR antagonists by sequentially performing primary screening, retesting, and dose-response analysis using cell-based hPXR gene reporter and receptor binding assays, as well as receptor and promoter specificity assays. The compound SJ000076745-1 is the most potent and specific hPXR antagonist in the 1,4,5-substituted 1,2,3-triazole chemical class, having a cell-based hPXR antagonist 50% inhibitory concentration (IC50) value of 377 ± 16 nM and an hPXR binding inhibitory IC50 value of 563 ± 40 nM.