The only PDE4 inhibitor currently approved for treating pulmonary diseases is the orally administered roflumilast, which reduces exacerbation rates in patients with COPD (Sturton and Fitzgerald, 2002; Calverley et al., 2009; Rennard et al., 2011; Bardin et al., 2015; Martinez et al., 2015, 2016) and shows also evidence of clinical benefits in asthma (Giembycz and Newton, 2015) although it is not labeled for this indication. Here, PDE4A is linked to chronic obstructive pulmonary disease.