PDE4A and chronic bronchitis: Notably this effect was not observed in the budesonide group and was consistent with the results of the BIOMARKER study (Table 4) where tanimilast was given in COPD patients with chronic bronchitis on top of triple therapy, indicating a specific effect of inhaled PDE4 inhibition irrespective of the study population and the background therapy (Singh et al., 2019; 2020c).