Today's Cardiovascular Drug Development

T hrough evolution, several animal species have been endowed with salivary anticoagulants, presumably to secure their nutritional requirements for fluid blood from their prey. It has been known for centuries that the bites of leeches, certain snakes, insects, and vampire bats can result in local and systemic bleeding. The use of the medicinal leech, Hirudo medicinalis, for therapeutic bloodletting goes back to the middle ages. The major anticoagulant from the saliva of the medicinal leech, hirudin, was purified two decades ago and found to be a highly specific inhibitor of thrombin.' The complementary DNA for hirudin was later cloned and expressed,2 and recombinant hirudin has emerged today as an interesting candidate to replace heparin in acute anticoagulant therapy.