Discovery of a Novel Potent and Selective Calcium Release-Activated Calcium Channel Inhibitor: 2,6-Difluoro-N-(2'-methyl-3'-(4-methyl-5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)-[1,1'-biphenyl]-4-yl)benzamide. Structure-Activity Relationship and Preclinical Characterization.

The role of calcium release-activated calcium (CRAC) channels is well characterized and is of particular importance in T-cell function. CRAC channels are involved in the pathogenesis of several autoimmune diseases, making it an attractive therapeutic target for treating inflammatory diseases, like rheumatoid arthritis (RA). A systematic structure-activity relationship study with the goal of optimizing lipophilicity successfully yielded two lead compounds, 36 and 37. Both compounds showed decent potency and selectivity and a remarkable pharmacokinetic profile. Further characterization in in vivo RA models and subsequent histopathological evaluation of tissues led to the identification of 36 as a clinical candidate. Compound 36 displayed an excellent safety profile and had a sufficient safety margin to qualify it for use in human testing. Oral administration of 36 in Phase 1 clinical study in healthy volunteers established favorable safety, tolerability, and good target engagement as measured by levels of IL-2 and TNF-α.