Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is expressed on mast cells and eosinophils, but information about Siglec-8 expression and function in the lung is limited. A humanized antibody, antolimab (AK002), targeting Siglec-8 is undergoing development for treatment of diseases associated with mast cell and eosinophil-driven inflammation.
To characterize Siglec-8 expression in the airway in asthma and determine if antibodies that target Siglec-8 (S8mAbs) can decrease airway eosinophils in asthma or inhibit lung mast cell activation.
Gene expression profiling and flow cytometry were used to characterize Siglec-8 expression in sputum cells from stable asthma. An antibody-dependent cellular cytotoxicity (ADCC) assay was used to determine if an S8mAb can decrease eosinophils in sputum from asthma patients ex vivo. A mast cell activation assay was used to determine if an S8mAb can inhibit mast cell activation in human lung tissue ex vivo.
Gene expression for Siglec-8 is increased in sputum cells in asthma and correlates with gene expression for eosinophils and mast cells. Gene expression for Siglec-8 is inversely and significantly correlated with measures of airflow obstruction in asthma patients. Siglec-8 is prominently expressed on the surface of eosinophils and mast cells in sputum. S8mAbs decrease eosinophils in sputum from patients with asthma and inhibit FcεR1-activated mast cells in lung tissues.
Siglec-8 is highly expressed on eosinophils and mast cells in asthmatic sputum and targeting Siglec-8 with an antibody is a plausible strategy to decrease sputum eosinophils and inhibit lung mast cells in asthma.

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