EHNA is a potent and selective dual inhibitor of cyclic nucleotide phosphodiesterase 2 (PDE2) (IC50 = 4 μM) and adenosine deaminase (ADA). It exhibits concentration-dependent inhibition of cGMP-stimulated PDE2 activity, with IC50 values of 0.8 μM in humans and 2 μM in porcine myocardium, but shows limited inhibition on unstimulated PDE2. EHNA is involved in modulating various pharmacological responses, such as antiviral, antitumor, and antiarrhythmic effects.