**Core Concept**
GpIIb/IIIa inhibitors are antiplatelet agents that block the final common pathway of platelet aggregation by inhibiting the GPIIb/IIIa receptor on platelets. These drugs prevent platelet activation and aggregation, thereby reducing thrombotic risk in acute coronary syndromes and percutaneous coronary interventions.

**Why the Correct Answer is Right**
Abciximab, eptifibatide, and tirofiban are all direct or indirect antagonists of the GPIIb/IIIa receptor. Abciximab is a monoclonal antibody fragment, while eptifibatide and tirofiban are small molecule antagonists that bind to the GPIIb/IIIa receptor. Prasugrel, however, is a **P2Y12 receptor inhibitor**, not a GPIIb/IIIa inhibitor. It blocks ADP-induced platelet activation via the P2Y12 receptor, acting upstream in the platelet activation pathway.

**Why Each Wrong Option is Incorrect**
Option A: Abciximab is a monoclonal antibody that binds to GPIIb/IIIa and is a potent inhibitor of platelet aggregation.
Option B: Eptifibatide is a small molecule that competitively inhibits GPIIb/IIIa receptor.
Option C: Tirofiban is a synthetic peptide that binds to GPIIb/IIIa, preventing platelet aggregation.
Option D: Prasugrel is **not** a GPIIb/IIIa inhibitor — it is a P2Y12 inhibitor, making it the correct choice for "all except".

**Clinical Pearl / High-Yield Fact**
Remember: **GPIIb/IIIa inhibitors (like abciximab, eptifibatide, tirofiban)** work at the final platelet aggregation step, while **P2Y12 inhibitors (like prasugrel)** act earlier by blocking ADP signaling. Never confuse the two pathways — this is a classic exam trap.

✓ Correct Answer: D. Prasugrel