Piclamilast

Piclamilast functions through the selective inhibition of the four PDE4 isoforms (PDE4A-D). It shows no inhibition of the other PDEs. The PDE4 isoforms are especially important to inflammatory and immunomodulatory cells. They are the most common PDE in inflammatory cells such as mast cells, neutrophils, basophils, eosinophils, T lymphocytes, macrophages, and structural cells such as sensory nerves and epithelial cells. PDE4 hydrolyzes cyclic adenosine monophosphate (cAMP) to inactive adenosine monophosphate (AMP). Inhibition of PDE4 blocks hydrolysis of cAMP thereby increasing levels of cAMP within cells. cAMP suppresses the activity of immune and inflammatory cells.

PDE4 inhibition in an induced chronic lung disease murine model was shown to have anti-inflammatory properties, attenuate pulmonary fibrin deposition and vascular alveolar leakage, and prolong survival in hyperoxia-induced neonatal lung injury. A study of PDE4 inhibition in a murine model of allergic asthma showed that piclamilast significantly improves the pulmonary function, airway inflammation and goblet cell hyperplasia.^[4][5]

Vomiting is the most commonly cited side effect of piclamilast. It has proven difficult to separate the emetic side effects from the therapeutic benefits of several PDE4 inhibitors, including piclamilast.^[6]