Imazodan, a small molecule compound with positive inotropic activity, is a selective type III phosphodiesterase inhibitor and can be used to study heart failure.

Dipyridamole (Persantine) is a phosphodiesterase inhibitor that blocks uptake and metabolism of adenosine by erythrocytes and vascular endothelial cells.

Nerandomilast (BI 1015550) is an orally active PDE4B inhibitor with IC50 of 7.2 nM. BI 1015550 has potential applications in inflammation, allergic diseases, pulmonary fibrosis and chronic obstructive pulmonary disease (COPD) with a good safety profile.