Chlorogenic Acid Derivatives: Novel Natural Agonists of RORα with Potential Therapeutic Applications

RORα is considered a tumor suppressor that is expressed at reduced levels in various tumor cell lines and tissues. Many researchers have attempted to discover potent, selective synthetic ligands for RORα to verify its importance in various biological systems and disease models. Although RORα is a promising target for circadian rhythm, cancer, and metabolic and immune diseases, there are currently no drugs that target RORα on the market. Several pharmaceutical companies are working to develop drugs using natural products as selective agonists of RORα. For example, GENFIT and BICOLL are developing neoruscogenin, the first potent bioavailable natural product identified as a specific agonist of RORα, as a therapeutic drug for autoimmune disorders in the preclinical stage. Therefore, the development of drugs targeting RORα in the future will be a significant achievement for treating related diseases.

We performed reverse docking using AlphaFold DB and Schrödinger's small molecule drug discovery platform to explore the conformational features of RORα and RORγ and the effects of chlorogenic acid and its derivatives on protein conformational binding. Our methods included molecular dynamics simulation, radius of rotation, calculation of binding free energy, hydrogen bond formation, and ligand-residue interaction network profiles. Our results showed that both systems were relatively stable throughout the simulation, and hydrophobic stacking contributed significantly to the binding free energy due to the large number of aromatic and hydrophobic rings in the active site residues. The energy decomposition analysis showed that electrostatic interactions were potentially important binding forces, while van der Waals forces contributed more prominently to the system. The RORα binding site amino acids GLN19 and ARG97 and the RORγ binding site amino acids GLN25, LbleEU26, ARG103, and ARG106 exhibited high hydrogen bond occupancy and therefore played an important role in protein stability, as verified by our point mutation and dual luciferase reporter experiments.

Our observations open up opportunities for designing natural modulators of RORs as possible therapeutic agents in metabolic and immune disorders. Recently, we performed a reverse docking study of chlorogenic acid derivatives and found them to be natural RORα agonists with a weak inverse agonistic effect on RORγ. By calculating the binding energy of protein ligands for stable trajectories, chlorogenic acid derivatives exhibited the ability to bind directly to RORs-LBD with high affinity and showed lower binding energy than endogenous ligands. This lays a foundation for subsequent studies on RORs and small molecule ligands to further understand the physiological functions of RORs.