Synthesis and biological evaluation of imidazo[1,2-a]pyridine derivatives as novel PI3 kinase p110 alpha inhibitors

3-{1-[(4-Fluorophenyl)sulfonyl]-1H-pyrazol-3-yl}-2-methylimidazo[1,2-a]pyridine, 2a, was discovered in our chemical library as a novel p110 alpha inhibitor with an IC50 of 0.67 mu M, through screening in a scintillation proximity assay. Optimization of the substituents of 2a increased the p110 alpha inhibitory activity by more than 300-fold (2g: IC50 = 0.0018 mu M). Further structural modification of 2g afforded thiazole derivative 12, which has potent p110 alpha inhibitory activity (IC50 of 0.0028 mu M) and is highly selective for p110 alpha over other PI3K isoforms. Compound 12 also inhibited serum-induced cell proliferation of A375 and HeLa cells in vitro with IC50 values of 0.14 mu M and 0.21 mu M, respectively, and suppressed tumor growth by 37% in a mouse HeLa xenograft model when dosed intraperitoneally at 25 mg/kg. These results suggest that selective p110 alpha inhibitors may have potential as cancer therapeutic agents. (c) 2006 Elsevier Ltd. All rights reserved.