DM243

DM243 is an EPAC1 activator and STAT3 modulator with a pIC50 of 4.769. It increases the levels of GTP-bound Rap1 in cells expressing EPAC1 without activating EPAC2 or PKA. DM243 reduces STAT3 phosphorylation levels in endothelial cells induced by IL-6/IL-6Rα. This compound inhibits the transformation of fibroblasts into myofibroblasts induced by TGF-β1, thereby decreasing the levels of α-smooth muscle actin and type I collagen in pulmonary fibroblasts. DM243 exhibits very low cytotoxicity in normal human lung fibroblasts.

DM243 binds to the cyclic nucleotide-binding domains of EPAC1 and EPAC2, showing a slight preference for EPAC1 with pIC50 values of 4.769 and 4.436, respectively, over a log concentration range for 4 hours. At a concentration of 100 μM, DM243 effectively activates the EPAC1-Rap1 signaling pathway in U2OS cells transfected with EPAC1, significantly increasing Rap1-GTP levels. When applied at 1 μM, it markedly inhibits IL-6/IL-6Rα-induced STAT3 phosphorylation in human umbilical vein endothelial cells, demonstrating a greater reduction in normalized phosphorylated STAT3 signal compared to other tested analogs. DM243, within a logarithmic concentration range, following a 1-hour pretreatment and a subsequent 72-hour exposure, moderately inhibits TGF-β1-induced differentiation of normal human lung fibroblasts into myofibroblasts, with pIC50 values of 4.34 for αSMA and 4.40 for type I collagen. In a 72-hour exposure, DM243 shows minimal cytotoxicity to normal human lung fibroblasts at concentrations effective in inhibiting TGF-β1-induced fibroblast differentiation, with only a slight decrease in nuclear count observed throughout the tested concentration range. Additionally, DM243 at 1 μM does not activate PKA in EPAC1-transfected U2OS cells, as confirmed by the absence of phosphorylated VASP (Ser157) signaling.