Hirudin and derivatives were originally discovered in Hirudo medicinalis: Univalent DTIs include: Thrombin demonstrates a high level of allosteric regulation.
A recent patent review has shown that the general consensus among researchers is that allosteric inhibitors may provide a more regulatable anticoagulant.
Bivalent DTIs enjoy limited use in circumstances where heparin would be indicated such as the acute coronary syndrome ("unstable angina"), but cannot be used.
[1] Ximelagatran showed good efficacy compared with warfarin in several trials in prevention and treatment of deep vein thrombosis and as thromboprophylaxis in atrial fibrillation.
Dabigatran (Pradaxa) was found to be noninferior to Warfarin in prevention of ischemic stroke, as well as intracranial hemorrhage risk and overall mortality for non-valvular atrial fibrillation according to the RE-LY trial.