A) Relative inhibitory activity for EPAC1-mediated Rap1b-bGDP exchange. B) Relative inhibitory activity for EPAC2-mediated Rap1b-bGDP exchange. Dose-dependent inhibition of EPAC1/2 GEF activity by compounds 5, 6, 14, and 31, in the presence of 20 μM cAMP. Relative GEF activity were presented as normalized reaction rate constant (means ± SEM, n =3) described in the method.