Characterization of A Novel CRAC Inhibitor that Potently Blocks Human T cell Activation and Effector Functions

Store operated calcium entry (SOCE) downstream of T cell receptor (TCR) activation in T lymphocytes has been shown to be mediated mainly through the Calcium Release Activated Calcium (CRAC) channel. Here, we compared the effects of a novel, potent and selective CRAC inhibitor, 2,6-Difluoro-N-{5-[4-methyl-1-(5-methyl-thiazol-2-yl)-1,2,5,6-tetrahydro-pyridin-3-yl]-pyrazin-2-yl}-benzamide (RO2959), on T cell effector functions with that of a previously reported CRAC channel inhibitor, YM-58483, and a calcineurin inhibitor Cyclosporin A (CsA). Using both electrophysiological and calcium-based fluorescence measurements, we showed that RO2959 is a potent SOCE inhibitor that blocked an IP3-dependent current in CRAC-expressing RBL-2H3 cells and CHO cells stably expressing human Orai1 and Stim1, as well as SOCE in human primary CD4+ T cells triggered by either TCR stimulation or thapsigargin treatment. Furthermore, we demonstrated that RO2959 completely inhibited cytokine production as well as T cell proliferation mediated by TCR stimulation or MLR (Mixed Lymphocyte Reaction). Lastly, we showed by gene expression array analysis that RO2959 potently blocked TCR triggered gene expression and T cell functional pathways similar to CsA and FK506. Thus, both from a functional and transcriptional level, our data provide evidence that RO2959 is a novel and selective CRAC inhibitor that potently inhibits human T cell functions.

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Chen G, Panicker S, Lau KY, Apparsundaram S, Patel VA, Chen SL, Soto R, Jung JK, Ravindran P, Okuhara D, Bohnert G, Che Q, Rao PE, Allard JD, Badi L, Bitter HM, Nunn PA, Narula SK, DeMartino JA