A-9758 is a RORγ ligand and a potent, selective RORγt inverse agonist ( IC 50 =5 nM), and exhibits robust potency against IL-17A release. A-9758 is effective in suppressing both Th17 differentiation and Th17 effector function. A-9758 significantly attenuates IL-23 driven psoriasiform dermatitis and is effective in blocking skin and joint inflammation.