Identifying antagonist drugs for TRPM8 ion channel as candidates for repurposing

Even though it is confirmed that ion channels are at the centre of many diseases, approved drugs are only available for small percentage of these proteins, and yet many pathologically important ion channels like transient receptor potential (TRP) cation channels remain without approved drugs. One reason could be the time-consuming and expensive process in drug discovery. Which has high possibility of failure in any step even after approval and marketing. Therefore, repurposing approved drugs might be considered as a solution and may offer an accelerated procedure in finding new treatments for patients. For the present research we selected TRPM8 ion channel as a neglected target despite growing number of studies regarding its association with numerous diseases. In this project we have first identified potent antagonists for TRPM8 ion channel among approved drugs, by using mainly the automated patch clamp device IonFlux 16. Such device allowed us to screen blocking potency of drugs against TRPM8 ion channel in time efficient way. Our approach consisted of using ligand-based virtual screening method, to optimize our screening by identifying candidates for further screening. We also studied possible interactions of identified drugs with antagonist binding site on TRPM8 channel by molecular docking. Furthermore, we have evaluated the effects of identified antagonists against different types of pancreatic ductal adenocarcinoma (PDAC) cells. We were able to identify four drugs with IC50 lower than 50 µM including propranolol, propafenone, carvedilol and nebivolol. Among them nebivolol with IC50 = 0.97± 0.15 µM and carvedilol with IC50 = 9.1 ± 0.6 µM were the most potent blockers. Studying the interactions of identified drugs with known binding site of TRPM8 by molecular docking, revealed high possibility of direct binding of nebivolol to binding site of TRPM8. Nebivolol was the most cytotoxic drug against PDACs, but it was also toxic against non-cancerous HEK-293 cells. While carvedilol had cytotoxic against PDACs, interestingly it wasn’t cytotoxic against HEK-293 cells. Result of these study will provide promising candidates for drug repurposing and will propose promising lead compound in drug discovery for new antagonists of TRPM8 ion channel. Also, our method of approach for identifying candidate drugs as agonist or antagonist could be applied for other ion channels.