Covalent Occlusion of the RORγt Ligand Binding Pocket Allows Unambiguous Targeting of an Allosteric Site

The nuclear receptor ROR gamma t is a key positive regulator in the differentiation and proliferation of T helper 17 (Th17) cells and the production of proinflammatory cytokines like IL-17a. Dysregulation of this pathway can result in the development of various autoimmune diseases, and inhibition of ROR gamma t with small molecules thus holds great potential as a therapeutic strategy. ROR gamma t has a unique allosteric ligand binding site in the ligand binding domain, which is distinct from the canonical, orthosteric binding site. Allosteric modulation of ROR gamma t shows high potential, but the targeted discovery of novel allosteric ligands is highly challenging via currently available methods. Here, we introduce covalent, orthosteric chemical probes for ROR gamma t that occlude the binding of canonical, orthosteric ligands but still allow allosteric ligand binding. Ultimately, these probes could be used to underpin screening approaches for the unambiguous and rapid identification of novel allosteric ROR gamma t ligands.