All of the following are GpIIb/IIIa antagonist, except:

Clopidrogrel is an anti-thrombotic drug which interferes with the function of the platelets by binds and alters the surface receptors of platelets and inhibits ADP as well as the fibrinogen induced platelet aggregation. While the other three options are GpIIb/IIIa antagonists which on binding to the receptors inhibit the binding of platelet agonists (like collagen, thrombin, TXA2, ADP) thus in turn inhibit the platelet aggregation. Ref: K D Tripathi Textbook of Pharmacology, 5th Edition, Pages 571-73