Benzoxazepines Achieve Potent Suppression of IL-17 Release in Human T-Helper 17 (TH17) Cells through an Induced-Fit Binding Mode to the Nuclear Receptor RORγ

ROR gamma t, an isoform of the retinoic acid-related orphan receptor gamma (RORc, ROR gamma), has been identified as the master regulator of T-helper 17 (T(H)17) cell function and development, making it an attractive target for the treatment of autoimmune diseases. Validation for this target comes from antibodies targeting interleukin-17 (IL-17), the signature cytokine produced by T(H)17 cells, which have shown impressive results in clinical trials. Through focused screening of our compound collection, we identified a series of N-sulfonylated benzoxazepines, which displayed micromolar affinity for the ROR gamma ligand-binding domain (LBD) in a radioligand binding assay. Optimization of these initial hits resulted in potent binders, which dose-dependently decreased the ability of the ROR gamma-LBD to interact with a peptide derived from steroid receptor coactivator 1, and inhibited the release of IL-17 secretion from isolated and cultured human T(H)17 cells with nanomolar potency. A cocrystal structure of inverse agonist 15 (2-chloro-6-fluoro-N-(4-{[3-(trifluoromethyl) phenyl] sulfonyl}-2,3,4,5-tetrahydro-1,4-benzoxazepin-7-yl) benzamide) bound to the ROR gamma-LBD illustrated that both hydrophobic interactions, leading to an induced fit around the substituted benzamide moiety of 15, as well as a hydrogen bond from the amide NH to His479 seemed to be important for the mechanism of action. This structure is compared with the structure of agonist 25 (N-(2-fluorophenyl)-4[(4-fluorophenyl) sulfonyl]-2,3,4,5-tetrahydro-1,4-benzoxazepin6-amine) and structures of other known ROR gamma modulators.