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

Author(s)

Burk, Oliver ^{[1, 2]} ; Kronenberger, Thales ^{[3, 4, 5]} ; Keminer, Oliver ^[3] ; Lee, Serene M. L. ^[6] ; Schiergens, Tobias S. ^[6] ; Schwab, Matthias ^{[1, 7, 2, 8]} ; Windshuegel, Bjoern ^{[3, 9]}

Affiliation

^[1] Univ Tubingen, Tubingen - Germany

^[2] Dr Margarete Fischer Bosch Inst Clin Pharmacol, Auerbachstr 112, D-70376 Stuttgart - Germany

^[3] Fraunhofer Inst Mol Biol & Appl Ecol IME, ScreeningPort, Schnackenburgallee 114, D-22525 Hamburg - Germany

^[4] Univ Hosp Tubingen, Dept Internal Med 3, Tubingen - Germany

^[5] Univ Eastern Finland, Sch Pharm, Kuopio - Finland

^[6] Ludwig Maximilians Univ Munchen, Univ Hosp, Dept Gen Visceral & Transplant Surg, Munich - Germany

^[7] Univ Tubingen, Dept Pharm & Biochem, Tubingen - Germany

^[8] Univ Tubingen, Dept Clin Pharmacol, Tubingen - Germany

^[9] Univ Hamburg, Inst Biochem & Mol Biol, Dept Chem, Hamburg - Germany

• Document type: Journal article
• Source: MOLECULAR PHARMACOLOGY; v. 99, n. 3, p. 184+, MAR 1 2021.
• Web of Science Citations: 0

Abstract

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-tert-butylamide (M8) on PXR to elucidate the underlying molecular mechanism. Molecular docking suggested direct binding to the PXR ligand-binding domain, which was confirmed experimentally by limited proteolytic digestion and competitive ligand-binding assays. Concentration-response analyses using cellular transactivation assays identified nelfinavir and M8 as partial agonists with EC50 values of 0.9 and 7.3 mu M and competitive antagonists of rifannpin-dependent induction with IC50 values of 7.5 and 25.3 mu M, respectively. Antagonism exclusively resulted from binding into the PXR ligand-binding pocket. Impaired coactivator recruitment by nelfinavir as compared with the full agonist rifampin proved to be the underlying mechanism of both effects on PXR. Physiologic relevance of nelfinavir-dependent modulation of PXR activity was investigated in respectively treated primary human hepatocytes, which showed differential induction of PXR target genes and antagonism of rifampin-induced ABCB1 and CYP3A4 gene expression. In conclusion, we elucidate here the molecular mechanism of nelfinavir interaction with PXR. It is hypothesized that modulation of PXR activity may impact the anticancer effects of nelfinavir. SIGNIFICANCE STATEMENT Nelfinavir, which is being investigated for repurposing as an anticancer medication, is shown here to directly bind to human pregnane X receptor (PXR) and thereby act as a partial agonist and competitive antagonist. Its major metabolite nelfinavir hydroxy-tert-butylamide exerts the same effects, which are based on impaired coactivator recruitment. Nelfinavir anticancer activity may involve modulation of PXR, which itself is discussed as a therapeutic target in cancer therapy and for the reversal of chemoresistance. (AU)

• FAPESP's process: 14/03644-9 - Targeting alternative ligand-binding sites in nuclear receptors using computational and experimental screening
• Grantee: Thales Kronenberger
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/27313-1 - Targeting alternative ligand-binding sites in nuclear receptors using computational and experimental screening
• Grantee: Thales Kronenberger
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate