122-LB: In Vitro Pharmacodynamic Studies of IDG-16177, a Potent GPR40 Agonist, for the Treatment of Type 2 Diabetes

G-protein-coupled receptor 40 (GPR40/FFA1/FFAR1), a clinically validated anti-diabetes target, enhances insulin secretion in type 2 diabetes. It is known that the effect of glucose-stimulated insulin secretion (GSIS) in pancreatic β cells is mediated primarily through Gq. However, in a recent study, it was found that GPR40 plays a role in both G protein-mediated and β-arrestin-mediated mechanisms, and fasiglifam (TAK-875), a partial GPR40 agonist discontinued in phase 3 clinical trials, induces insulin secretion by mediating β-arrestin rather than Gq. Therefore, by using stable GPR40 cell lines and β cells, we tried to confirm the signaling mechanism and efficacy of IDG-16177, which is being developed by Ildong Pharma in first-in-human study, as a GPR40 agonist. In cells expressing recombinant human, rat, and cynomolgus monkey GPR40, IDG-16177 dose-dependently increases intracellular free Ca²⁺ level, with EC₅₀ of 114.3, 103.9, and 758.8 nM, respectively, showing no significant differences between human and rat (fasiglifam EC₅₀= 75.2, 140.4, and 906.2 nM). IDG-16177 enhances β-arrestin recruitment, which has been shown to contribute to GPR40-mediated GSIS, with an EC₅₀ of 68.0 nM and Emax of 99.4%, and is more efficacious and potent than fasiglifam (EC₅₀= 154.0 nM; Emax= 88.0%). IDG-16177 exhibits EC₅₀ of 0.8 nM and 110.6 nM, in inositol phosphate 1 (IP1) accumulation assay and extracellular signal-regulated kinase (ERK) activation assay, respectively. Although IDG-16177 shows no signal at the cAMP pathway like fasiglifam, IDG-16177 (0.1~3 μM)-treated group enhances more insulin secretion than fasiglifam (1~10 μM) in HIT-T15 β cells. These studies support the potential utility of IDG-16177 for the treatment of type 2 diabetes.