Bivalirudin

Bivalirudin is a 20-amino acid synthetic direct thrombin inhibitor (DTI) derived from hirudin, the natural anticoagulant found in medicinal leech saliva. FDA-approved under the brand name Angiomax, it is used as an anticoagulant during percutaneous coronary intervention (PCI) and in patients with or at risk for heparin-induced thrombocytopenia (HIT). Its reversible binding mechanism and short half-life allow predictable anticoagulation with rapid offset after cessation.

Bivalirudin specifically inhibits both circulating and clot-bound thrombin by bivalently binding to two distinct sites on the thrombin molecule: the catalytic active site and the anion-binding exosite 1 (fibrinogen recognition site). This dual binding differentiates bivalirudin from univalent inhibitors. Importantly, thrombin slowly cleaves bivalirudin at the Arg3-Pro4 bond, resulting in gradual recovery of thrombin activity — providing reversible inhibition proportional to drug concentration. Bivalirudin directly inhibits thrombin-catalyzed or induced reactions, including fibrin formation, coagulation factor V, VIII, and XIII activation, and platelet aggregation triggered by thrombin. The result is dose-dependent prolongation of activated clotting time (ACT), aPTT, and thrombin time.

The REPLACE-2 trial (n=6,010) demonstrated bivalirudin non-inferior to heparin plus GP IIb/IIIa inhibitor for composite ischemic endpoints during PCI, with significantly lower bleeding rates. The HORIZONS-AMI trial in ST-elevation MI patients showed bivalirudin reduced 30-day major bleeding by 40% versus heparin with GP IIb/IIIa inhibitors, and reduced cardiac mortality at 3 years. The EUROMAX and HEAT-PPCI trials provided additional evidence in primary PCI settings, though results varied on net clinical benefit. Meta-analyses confirm bivalirudin's consistent reduction in major bleeding with comparable ischemic outcomes versus heparin-based anticoagulation in interventional cardiology.