Potent and Orally Bioavailable Inverse Agonists of RORγt Resulting from Structure-Based Design

Abstract

Retinoic acid receptor related orphan receptor γt (RORγt), has been identified as the master regulator of T17-cell function and development, making it an attractive target for the treatment of autoimmune diseases by a small-molecule approach. Herein, we describe our investigations on a series of 4-aryl-thienyl acetamides, which were guided by insights from X-ray cocrystal structures. Efforts in targeting the cofactor-recruitment site from the 4-aryl group on the thiophene led to a series of potent binders with nanomolar activity in a primary human-T17-cell assay. The observation of a DMSO molecule binding in a subpocket outside the LBD inspired the introduction of an acetamide into the benzylic position of these compounds. Hereby, a hydrogen-bond interaction of the introduced acetamide oxygen with the backbone amide of Glu379 was established. This greatly enhanced the cellular activity of previously weakly cell-active compounds. The best compounds combined potent inhibition of IL-17 release with favorable PK in rodents, with compound 32 representing a promising starting point for future investigations.

Atomistic simulations shed new light on the activation mechanisms of RORγ and classify it as Type III nuclear hormone receptor regarding ligand-binding paths

“…Thus, our simulations strongly support the binding of ligands for RORγ-LBD is type III, involving the backdoor path and clearly differentiates it from that of Type II members such as AR, MR or GR. Finally, this finding is further supported by very recent publications by AstraZeneca on the development of potent RORγ 4-aryl-thienylacetamide inverse agonists 15 . Their previous fragment-based efforts 16 discovered DMSO molecules binding on the rim of the “backdoor”.…”

RORγ Structural Plasticity and Druggability

“…For the Mode III pocket (RMSDs: 3-5 Å ), in addition to the displaced helices alike to Mode II, part of H11 turns into a loop, where His 479 is situated (Figure 6c,f). This dramatic change impairs the lock [35,36]. We also compared the conformations of orthosteric pockets in 69 LBD-inverse agonist complexes from crystal structures ( Supplementary Table S2).…”

“…For the Mode III pocket (RMSDs: 3–5 Å), in addition to the displaced helices alike to Mode II, part of H11 turns into a loop, where His 479 is situated ( Figure 6 c,f). This dramatic change impairs the lock [ 35 , 36 ].…”

RORγ Structural Plasticity and Druggability

“…For the Mode III pocket (RMSDs: 3 -5 Å), in addition to the displaced helices alike to Mode II, part of H11 turns into a loop, where His 479 is situated (Figure 6c, f). This dramatic change impairs the lock [36,37]. These modes construct a noticeably plastic structure of the orthosteric pocket for accepting inverse agonists.…”