The present invention relates to compounds of alkylidene pyrazolidinedione derivatives, which are effective platelet ADP receptor antagonists that prevent platelet aggregation and thrombosis. Thus, the present invention also relates to pharmaceutical compositions that contain the compounds as well as methods of preventing or treating peripheral, visceral, hepatic, renal, cardio- and cerebro-vascular diseases and conditions that are associated with platelet aggregation, including thrombosis, in humans and other mammals. The present invention further provides a process for manufacturing the alkylidene pyrazolidinedione derivatives.