RO2959 hydrochloride is a potent and selective CRAC channel inhibitor with an IC50 of 402 nM. RO2959 hydrochloride is a potent blocker of store operated calcium entry (SOCE) mediated by Orai1/Stim1 channels with an IC50 of 25 nM. RO2959 hydrochloride is also a potent inhibitor of human IL-2 production, and potently blocks T cell receptor triggered gene expression and T cell functional pathways.