Novel Benzo[4,5]imidazo[1,2-a]pyrimidine derivatives as selective Cyclooxygenase-2 Inhibitors: Design, synthesis, docking studies, and biological evaluation

The present study was aimed at the synthesis and evaluation of a new series of benzo[4,5]imidazo[1,2- a ]pyrimidine having a methylsulfonyl group as COX-2 (cyclooxygenase-2) inhibitor pharmacophore. Molecular modeling studies were performed using the Autodock program, and the results demonstrated that methylsulfonyl pharmacophore was adequately placed into the COX-2 active site. The in vitro and in vivo COX-2 inhibitory effects were also evaluated. In the in vitro assay, all newly synthesized compounds showed moderate to good selectivity for the inhibition of the COX-2 enzyme. However, compound 2-(4-(methylsulfonyl) phenyl)-4-phenylbenzo[4,5]imidazo[1,2- a ]pyrimidine ( 5a ) showed the highest COX-2 inhibitory effect (IC 50 : 0.05 μM) even more than celecoxib as the reference drug (IC 50 : 0.06 μM). For the in vivo study, the writing reflex test was used, and the results indicated that all synthesized compounds had well dose-dependent anti-nociceptive activity. The in vivo evaluation also showed that compound 2-(4-(methylsulfonyl)phenyl)-4-( p -tolyl)benzo[4,5]imidazo[1,2- a ]pyrimidine ( 5d ) had the highest activity in the writing reflex test (ED 50 : 5.75 mg/kg). In addition, the cytotoxicity effects of the synthesized compounds were tested on MCF-7 breast cancer cells, and all compounds showed considerable inhibitory results.