Celastrol Derivatives: Novel Targets and Mechanisms for Anti-Cancer and Anti-Inflammatory Effects

Celastrol (CSL) is a pentacyclic triterpenoid extracted from the root bark of Tripterygium wilfordii, which has shown great potential in anti-cancer and cerebral neurology. However, its toxicity has limited its clinical use. We have developed a series of derivatives with reduced toxicity and increased efficacy through biotransformation in the early stage. To discover the pharmacological activity of these derivatives, we used reverse docking with 23391 Homo sapiens proteins from AlphaFold DB and the Schrödinger platform Small Molecule Drug Discovery. We focused on the Retinoic Acid Related-Orphan Receptors (RORs) family, specifically RORα and RORγ, which are known targets for anti-inflammatory and anti-tumor effects. We filtered the derivatives through QikProp, docked for dynamics simulation, and calculated molecular mechanics-generalized born surface area (MMGBSA) binding energy. We also performed fluorescence polarization assay (FP assay), luciferase reporter gene assay, and the CCK8 assay. We found that CSL binds to GLN19, ARG97, ARG100 for RORα-Ligand binding domain (LBD) and GLN25, LEU26, ARG103, ARG106 for RORγ-LBD. We screened for the highest affinity derivatives and found that 2 μM 18-OH-CSL and 28-OH-CSL had the strongest agonistic effect on RORα-LBD, while 12-OH-CSL and a-ring aromatized 15-OH-CSL had the strongest inhibitory effect on RORγ-LBD. The positive and negative coulomb energy in MMGBSA supported these results.