Lirimilast is representative of a new structural class of PDE4 inhibitors, the benzofurans. It it is highly selective type 4 cyclic nucleotide phosphodiesterase inhibitor. Lirimilast inhibited human inflammatory cell functions that previously were reported to be sensitive to PDE4 inhibitors. It showed some selectivity for neutrophil and eosinophil functions over those of monocytes and T lymphocytes when compared to cilomilast and other reference PDE4 inhibitors. Lirimilast exhibited a broad profile of anti-inflammatory activity in animal models of COPD and asthma. Lirimilast produced emesis in primates. 1 week of treatment with the selective PDE4 inhibitor lirimilast does not affect FEV1 and sputum cell numbers in patients with asthma or chronic obstructive pulmonary disease (COPD). However, such treatment does seem to reduce levels of albumin and eosinophil cationic protein in sputum samples obtained from patients with COPD.