Development of Novel Nuclear Receptor Ligands Based on Receptor-Folding Inhibition Hypothesis

Abstract

Nuclear receptors are ligand-inducible transcriptional factors, and regulate various significant biological phenomena such as cell differentiation, proliferation, metabolism, and homeostasis. By the elucidation of the physiological functions of nuclear receptors, they have become one of the most significant molecular targets for drug discovery in the fields of cancer, autoimmune diseases, and metabolic syndrome. In this study, several novel nuclear receptor ligands have been developed, based on the receptor-folding inhibition hypothesis is discussed. In this hypothesis, the antagonists for nuclear receptors are classified into two types, the misfolding inducers and the folding inhibitors, related to the helix 12 (AF-2 region) conformation of the receptor that is significant for the receptor activation. Then, in order to overcome the resistance in the treatment of prostate tumors with androgen antagonists, the novel folding-inhibitor type antagonists such as isoxazole and pyrrolecarboxamide derivatives were designed and synthesized. Some of them exhibited the androgen antagonistic activities in LNCaP cells with mutated androgen receptor in which conventional antagonists such as flutamide and RU56187 were inactive. The folding-inhibitor type vitamin D3 antagonists (DLAM series) are similarly developed. Further, novel non-seco-steroidal vitamin D3 analogs were designed and synthesized by using a 3,3-diphenylpropane derivative, LG190178 as lead compound. The aza analogs exhibited both potent vitamin D agonistic and androgen antagonistic activities. The results indicate the drug design based on the receptor-folding inhibition hypothesis is efficient in medicinal chemistry of nuclear receptors.