Which drug among the following does not inhibit platelet aggregation?
The selective COX-2 inhibitor (celecoxib) act primarily by inhibiting the cyclooxygenase enzymes that catalyze the first step in prostanoid biosynthesis. This leads to decreased prostaglandin  synthesis with both ​beneficial  and  unwanted  effects. ​
Reference: Lippincott Illustrated Reviews: Pharmacology Wolters Kluwer Sixth Edition page no 451; ​
Aspirin
Celecoxib
Ibuprofen
Clopidogrel