PDE4A and asthma: Tanimilast was extremely potent in inhibiting eosinophil activation (Moretto et al., 2015; Sabogal Piñeros et al., 2020), a finding consistent with the notion that PDE4 is prominently expressed in eosinophils, which are key players in shaping the pathogenesis of asthma, and also appear to play a role in a subgroup of COPD patients (Agusti et al., 2018).