[Synthesis and platelet aggregation inhibitory activity of 6-substituted dihydropyridazinones]

In order to develop more potent and less toxic antithrombotic agents, ten 6-(4-substituted piperazinyl acetyl aminophenyl)-4,5-dihydro-3(2H)-pyridazinones were synthesized. The title compounds were tested in vitro for platelet aggregation inhibitory activity with ADP-induced rat platelets and PAF-induced rabbit platelets. Preliminary tests showed that all of the pyridazinones could inhibit ADP-induced rat platelet aggregation. I7, I8, I9 were more potent than the control compound CI 930. I9 was the most potent compound with IC50 of 0.99 mumol/L. Pertaining to PAF-induced rabbit platelet aggregation, I9 was the most potent inhibitor with IC50 of 3.7 mumol/L.