Sildenafil, the first PDE-5 inhibitor approved for the treatment of ED following its serendipitous discovery [95], has also been investigated as a treatment for COVID-19 patients; indeed, Sildenafil improves pulmonary hemodynamics, as shown in idiopathic pulmonary fibrosis [96], by reducing vascular resistance and remodeling in the pulmonary circulation [97]. Here, PDE5A is linked to COVID-19.