Background Th17 cells play a key pro-inflammatory role in a variety of autoimmune diseases such as Arthritis, Inflammatory Bowel Disease, Psoriasis and Multiple Sclerosis. The nuclear hormone receptor RORγ controls the differentiation of Th17 cells and expression of IL-17. Antibodies against IL-17R (Brodalumab) and IL-17 (Ixekizumab) have demonstrated promising efficacy in clinical trials for psoriasis.
Objectives To identify novel and selective inverse agonists of RORγ, as well as to demonstrate efficacy in relevant disease models.
Methods Novel RORγ inverse agonists were designed using a combination of approaches including structure and knowledge based methods. Compounds were screened in a RORγ radio-ligand binding assay using 3H 25- Hydroxycholesterol, as well as in a cell based reporter assay to demonstrate inverse agonism (fusion of Gal4-DBD and RORγ-LBD in one vector, and UAS of Gal4 upstream of luciferase reporter in another vector). Selected compounds were screened against RORα to evaluate selectivity. Crystal structure of RORγ in complex with known inverse agonists as well as novel compounds, were solved. Th17 differentiation assay was developed using primary mouse CD4+ve T-cells to determine functional effect of the compounds. Pharmacokinetic profile in mice was determined for selected compounds with good ADME properties.
Results Novel hits from multiple structural classes have been identified, with IC50 in the range of 5 – 500 nM in binding assay. Compounds from the lead series demonstrated good activity (< 1 μM) in reporter assay. Co-crystal structure of novel compounds clearly showed the mode of binding. Several compounds demonstrated > 10 fold selectivity against RORα in a reporter assay. Compounds from multiple series have shown significant inhibition of IL-17 release from differentiated Th17 cells. Lead compounds have shown good pharmacokinetic properties in mice.
Conclusions We have identified novel and structurally diverse small molecule inverse agonists of RORγ. Selectivity against RORα and cell based activity has been demonstrated for compounds from multiple series. Relevant efficacy models have been established and profiling of lead compounds in these models in on-going.
Disclosure of Interest None Declared