Discrepancy in interactions and conformational dynamics of pregnane X receptor (PXR) bound to an agonist and a novel competitive antagonist.

Pregnane X receptor (PXR) is a nuclear receptor with an essential role in regulating drug metabolism genes. While the mechanism of action for ligand-mediated PXR agonism is well-examined, its ligand-mediated inhibition or antagonism is poorly understood. Here we employ microsecond timescale all-atom molecular dynamics (MD) simulations to investigate how our newly identified dual kinase and PXR inhibitor, compound 100, acts as a competitive PXR antagonist and not as a full agonist.

Target Hopping from Protein Kinases to PXR: Identification of Small-Molecule Protein Kinase Inhibitors as Selective Modulators of Pregnane X Receptor from TüKIC Library.

Small-molecule protein kinase inhibitors are used for the treatment of cancer, but off-target effects hinder their clinical use. Especially off-target activation of the pregnane X receptor (PXR) has to be considered, as it not only governs drug metabolism and elimination, but also can promote tumor growth and cancer drug resistance. Consequently, PXR antagonism has been proposed for improving cancer drug therapy.

Development and Experimental Validation of Regularized Machine Learning Models Detecting New, Structurally Distinct Activators of PXR.

The pregnane X receptor (PXR) regulates the metabolism of many xenobiotic and endobiotic substances. In consequence, PXR decreases the efficacy of many small-molecule drugs and induces drug-drug interactions. The prediction of PXR activators with theoretical approaches such as machine learning (ML) proves challenging due to the ligand promiscuity of PXR, which is related to its large and flexible binding pocket.

Identification and characterization of novel splice variants of human farnesoid X receptor.

Farnesoid X receptor (FXR, NR1H4) is a ligand-activated nuclear receptor, which regulates bile acid, lipid and glucose metabolism. Due to these functions, FXR has been investigated as a potential drug target for the treatment of liver diseases, such as primary biliary cholangitis and non-alcoholic steatohepatitis. Based on the previously described four splice variants, it has been suggested that alternative promoter usage and splicing may have an impact on total FXR activity as a result of encoding functionally diverse variants.

Nelfinavir and Its Active Metabolite M8 Are Partial Agonists and Competitive Antagonists of the Human Pregnane X Receptor.

The HIV protease inhibitor nelfinavir is currently being analyzed for repurposing as an anticancer drug for many different cancers because it exerts manifold off-target protein interactions, finally resulting in cancer cell death. Xenosensing pregnane X receptor (PXR), which also participates in the control of cancer cell proliferation and apoptosis, was previously shown to be activated by nelfinavir; however, the exact molecular mechanism is still unknown. The present study addresses the effects of nelfinavir and its major and pharmacologically active metabolite nelfinavir hydroxy--butylamide (M8) on PXR to elucidate the underlying molecular mechanism.