In addition, antibodies such as Mepolizumab [8] and Reslizumab [9] against interleukin 5 (IL-5), and Benralizumab [10] against IL-5 receptors to block eosinophil production, activation, migration are appealing, and are undergoing clinical trials to prevent end-organ manifestations and improve the quality of life of HES/CEL patients. This evidence concerns the gene IL5 and hypereosinophilic syndrome.