Biologic therapies for hypereosinophilic disorders: From tyrosine kinase inhibitors to monoclonal antibodies. Towards an increasingly customized management?

Hypereosinophilic syndromes (HES) encompass a wide range of disorders characterized by persistent peripheral blood hypereosinophilia (HE) (i.e., an eosinophil count ≥1.5 × 109/L and ≥ 10% eosinophils preferably with a minimal duration of 6 months if documentation is available) associated with organ damage and/or dysfunction attributable to tissue eosinophilic infiltrate and release of granule contents. In most cases, HE is associated with atopic conditions/allergies, parasitic infections, medications, autoimmune disorders and/or solid tumors in most cases. More rarely, it can be one of the dominant manifestations of an underlying myeloid/lymphoid neoplasm. With regard to hematological forms, in recent decades the advances in understanding the pathogenic aspects of HES have led to a growing interest in these diseases, and in the 2016 WHO classification multiple subgroups were defined according to the molecular profile with the aim of better characterizing these syndromes and establishing which patients will benefit from specific pharmacological targeted therapies. This review article will provide a comprehensive overview of possible therapeutic approaches for HES in the light of each specific molecular alteration, considering both tyrosine kinase inhibitors and monoclonal antibodies, either implemented in clinical practice or currently still under development.