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Ancrod (Viprinex®) is currently under evaluation as a drug to treat thromboses (for example strokes). This evaluation is currently in phase III of the drug discovery process. Before, ancrod was used under its commercial name Arvin® to treat blocked blood vessels due to heavy smoking. Arvin® has been used for some decades in Germany and Austria, but the licenses were withdrawn sometime in the eighties. Ancrod is a component isolated from the venom of the Malayan pitviper, Calloselasma rhodostoma, a species responsible for a lot of snakebites, often followed by amputations, in Asia. Ancrod can also be found in the venom of other venomous snakes (pitvipers, vipers and cobras), but the highest concentration can be found in the venom of the Malayan pitviper. This component takes fibrinogen, a protein involved in blood coagulation, out of the blood. Fibrinogen can often be found in elevated concentrations in clogged blood vessels. In Germany, two pharmaceutical companies (Neurobiological Technologies Inc. and Nordmark) acquired 1500 Malayan pitvipers last year for this research. The centre where these snakes are housed, cost around € 4.5 million and the snakes will be milked every month.
In the human body, blood clots can lead to a lot of trouble. They deprive certain parts of the body from oxygen, leading to possible necrosis. When this happens in the brain, this is called a stroke. In the US about 100.000 people per year suffer from blood clots in the legs. A common consequence hereof is amputation of the leg. The venom of the north-American copperhead (Agkistrodon contortrix), contains a component called fibrolase. This component may lead to degradation of blood clots. A US-based company, Nuvelo, reproduced this component using DNA recombination and patented it under the name alfimeprase. This company is currently examining this component to treat blood clots in the legs. Their goal is to inject alfimeprase locally, at the site of a blood clot, via a catheter, leading to its dissolution. Blood clots use the blood clotting factor fibrin, a threadlike protein. In a clot, fibrin proteins are attached to each other in threads. Alfimeprase works directly on the fibrin, which causes degradation of this blood clotting factor. It also works well on the place where it is injected, near the blood clot. Afterwards, it will be quickly inactivated by a protein in our blood called alpha-2 macroglobulin.