Li Kuang F, et al. - In this retrospective analysis, predictors of response to mepolizumab in subjects with severe treatment-refractory hypereosinophilic syndromes (HES) were determined and long-term outcomes in these subjects were compared to HES subjects treated with conventional therapies. All of these subjects were followed at a single center. Mepolizumab was confirmed to be an effective and well-tolerated therapy for HES. Glucocorticoid (GC)-responsive subjects with idiopathic or overlap forms of HES appeared more likely to be responsive to mepolizumab. Attenuation of comorbidity ascribed to discontinuation or reduction of conventional HES therapies was reported as a primary benefit of treatment. The most benefit was seen in those who completely discontinued GC. Overall, high dose mepolizumab was found to be a safe and effective salvage therapy for severe, treatment-refractory HES.