The therapeutic potential of PDE4 inhibition in diseases such as chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and asthma, has long been appreciated, with PDE4B up-regulation in airway epithelial cells being implicated in COPD pathogenesis (Michalski et al., 2012). Here, PDE4A is linked to cystic fibrosis.