Peripheral blood eosinophilia and eosinophilic lung inflammation are common in a 
variety of pulmonary conditions, including eosinophilic pneumonia and asthma, 
hypereosinophilic syndrome and Churg-Strauss syndrome. Therapy in most of these 
clinical entities consists of long-term treatment with systemic corticosteroids, 
which is not always successful and has substantial side-effects. Interest has 
increased considerably regarding alternative corticosteroid-sparing "smart" 
regimens in these diseases that target IL-5, an important regulator of 
eosinophilic development and function. To date, two humanized monoclonal 
antibodies, mepolizumab and reslizumab, have been developed that bind to human 
IL-5. In addition a new monoclonal antibody (MEDI-563) has been recently 
developed targeting the IL-5 receptor. This review will investigate the current 
status on IL-5 targeted therapy and related patents regarding eosinophil-driven 
respiratory diseases, primarily eosinophilic asthma but also CSS and HES. Recent 
advances and information from clinical trials will be presented in a way that 
will allow the reader to approach the role of the eosinophil in the lung 
diseases presented in this review.