Currently, oral PDE4 inhibitors are used as an add-on therapy for treating chronic respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD) (Parikh and Chakraborti, 2016; Zhang et al., 2018; Al-Sajee et al., 2019; Zuo et al., 2019). The gene discussed is PDE4A; the disease is chronic obstructive pulmonary disease.