HJC0197 is a potent Epac1 (exchange protein directly activated by cAMP 1) and Epac2 (IC50=5.9 μM for Epac2) antagonist. HJC0197 selectively blocks cAMP-induced Epac activation. HJC0197 inhibits Epac1-mediated Rap1-GDP exchange activity at 25 μM in the presence of equal concentration of cAMP.