Discovery and Optimization of a Series of Sulfonamide Inverse Agonists for the Retinoic Acid Receptor-Related Orphan Receptor-α

Abstract

Background: Despite a massive industry endeavor to develop RORγ-modulators for autoimmune disorders, there has been no indication of efforts to target the close family member RORα for similar indications. This may be due to the misconception that RORα is redundant to RORγ, or the inherent difficulty in cultivating tractable starting points for RORα. RORα-selective modulators would be useful tools to interrogate the biology of this understudied orphan nuclear receptor.

Objective: The goal of this research effort was to identify and optimize synthetic ligands for RORα starting from the known LXR agonist T0901317.

Methods: Fourty-five analogs of the sulfonamide lead (1) were synthesized and evaluated for their ability to suppress the transcriptional activity of RORα, RORγ, and LXRα in cell-based assays. Analogs were characterized by 1H-NMR, 13C-NMR, and LC-MS analysis. The pharmacokinetic profile of the most selective RORα inverse agonist was evaluated in rats with intraperitoneal (i.p.) and per oral (p.o.)dosing.

Results: Structure-activity relationship studies led to potent dual RORα/RORγ inverse agonists as well as RORα-selective inverse agonists (20, 28). LXR activity could be reduced by removing the sulfonamide nitrogen substituent. Attempts to improve the potency of these selective leads by varying substitution patterns throughout the molecule proved challenging.

Conclusion: The synthetic RORα-selective inverse agonists identified (20, 28) can be utilized as chemical tools to probe the function of RORα in vitro and in vivo.

Keywords: Autoimmune disorder; Liver X Receptor (LXR); Nuclear Hormone Receptor (NR); Retinoic Acid Receptor-related Orphan Receptor (ROR); Structure-Activity Relationship (SAR); Th17 cells..