JAK2 is an important target in multiple processes associated with tumor growth. In this study, virtual screening was employed for hit compound identification with chemical libraries using SurflexDock. Subsequently, hit optimization for potent and selective candidate JAK2 inhibitors was performed through synthesis of diverse C-1 substituted quinazoline derivatives. A novel compound 5p, (6,7-dimethoxyquinazolin-4-yl)naphthalen-1-ylamine, was thus obtained. JAK2 inhibitory activity of 5p was 43% at 20μM and this was comparable to AG490, a representative JAK2 inhibitor. Moreover, 5p showed a positive correlation between JAK2 inhibition and cytotoxicity; 5p treatment in HT-29 cells strongly inhibited JAK2 activation and subsequent STAT3 phosphorylation, reduced anti-apoptotic protein levels, and finally induced apoptosis. This suggests that compound 5p is a candidate inhibitor of JAK2 and its downstream STAT3 signaling pathway for antitumor therapy. In the docking model, the quinazoline template of 5k, the lead compound, occupied a hydrophobic region such as Leu856, Leu855, Ala880, Leu932 and Gly935, and the highly conserved hydrogen bond was created by 6-OMe of the ring template, which binds to the NH of Arg980. Moreover, hydrophobic interactions were identified between morpholine moiety and the hydrophobic region formed by Leu855, Ala880, Tyr931, Val911 and Met929. Also, compound 5k more strongly inhibited JAK2 phosphorylation in mouse embryonic stem cells than AG490. Our study shows the successful application of virtual screening for lead discovery and we propose that the novel compound 5p can be an effective JAK2 inhibitor candidate for further antitumor agent research.
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