P159 PHENOTYPIC CHARACTERIZATION OF INFLAMMATORY BOWEL DISEASE BIOPSIES REVEAL THAT MAST CELLS ARE SIGNIFICANTLY ELEVATED AND ACTIVATED IN PATIENTS WITH ULCERATIVE COLITIS

Abstract

Accumulation and activation of mast cells and eosinophils have been implicated in the pathogenesis of several chronic inflammatory gastrointestinal (GI) diseases, including eosinophilic gastrointestinal diseases (EGIDs) and inflammatory bowel disease (IBD). Despite the strong association of mast cell and eosinophil numbers and activation with the pathogenesis of IBD, no further characterization of these cells has been performed. Current treatment options for IBD include aminosalicylates, antibiotics, immunomodulators, biologic agents and small molecules. These therapies are only moderately effective. A significant proportion of patients fail to respond, do not fully respond, or lose response over time. Therefore, there is significant need for more selective and effective therapy options. Siglec-8 is an inhibitory receptor selectively expressed on human eosinophils and mast cells and represents a novel target for the treatment of IBD with the anti-Siglec-8 mAb, antolimab (AK002). We aimed to quantify and evaluate the activation state of mast cells and eosinophils in colonic tissue from IBD or non-diseased patients. In addition, we quantified the production of TNFa from human colon tissue mast cells and evaluated the inhibitory activity of antolimab (AK002) on these cells.