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)

Abstract

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. ALPN-101 is an Fc fusion protein of a human inducible T cell costimulator ligand (ICOSL) variant immunoglobulin domain (vIgDTM) engineered to inhibit simultaneously the CD28 and ICOS pathways. It has been shown to have potent in vitro immunosuppressive activity and in vivo efficacy in models of disease for which implication of CD28 and ICOS has been reported (e.g. aGvHD, inflammatory arthritis, Sjögren’s, lupus, MS). Its safety, tolerability, and dose-dependent pharmacokinetics/dynamics are under study in a Ph1 healthy volunteer study. Here, we evaluate ALPN-101 in vitro using PBMC from Crohn’s and ulcerative colitis patients demonstrating superior suppression of T cell activation and cytokine release and show its efficacy to both prevent and treat disease in a mouse T cell transfer model of chronic colitis.