P156 ALPN-101, A FIRST-IN-CLASS DUAL ICOS/CD28 ANTAGONIST, DEMONSTRATES EFFICACY IN PATIENT-DERIVED PBMC IN VITRO AND IN AN IN VIVO T CELL TRANSFER MODEL OF CHRONIC INFLAMMATORY BOWEL DISEASE (IBD)

T cell costimulation has been strongly implicated in the pathogenesis of IBD, yet CD28 costimulatory pathway inhibitors (e.g. abatacept, CTLA4-Fc) have not proven clinically efficacious, implicating an alternative costimulatory pathway. ICOS is a costimulatory receptor highly related to CD28, upregulated upon T cell activation and mediating costimulatory signals in post-activation T cells – suggesting ICOS may be more relevant in active disease. In contrast, CD28 predominates in naïve T cells and is less critical in activated, effector and/or memory T cells.