ancrod therapy. Chemistry Ancrod was originally isolated from the venom of the Malayan pit viper (Calloselasma rhodostoma, formerly Agkistrodon rhodostoma) and is a serine protease. It is one of the Venombin A enzymes. Two genes encoding for such enzymes have been found in the viper genome. The form used in clinical trials was not made recombinantly, but was purified from harvested venom. History Under the brand name Arwin, ancrod was marketed for several decades in Germany and Austria, until it was withdrawn in the 1980s. Arwin was a brand name of Knoll Pharma. In 2001 Knoll was acquired by Abbott Laboratories, and in 2002 Abbott licensed the rights to ancrod to Empire Pharmaceuticals, a startup that included a Knoll employee who had worked on ancrod. In 2004 Empire was acquired by Neurobiological Technologies. NTI also acquired a lot of unpurified venom in the acquisition, and had that purified for use in its clinical trials. The failure of ancrod in the 6-hour window for ischemic stroke trial in 2008 led to cuts in staff, an effort to sell off the company's assets, and finally to the dissolution of NTI in August 2009. Society and culture Viprinex is not currently approved or available. Research For the treatment of established deep vein thrombosis; central retinal and branch vein thrombosis; priapism; pulmonary hypertension of embolic origin; embolism after insertion of prosthetic cardiac valves; rethrombosis after thrombolytic therapy and rethrombosis after vascular surgery. It is also indicated for the prevention of deep venous thrombosis after repair of the fractured neck of a femur. For the treatment of moderate and severe chronic circulatory disorders of peripheral arteries (e.g., arteriosclerosis obliterans, thromboangiitis obliterans, diabetic microangiopathy and Raynaud's phenomenon). Ancrod has been shown to be useful for maintaining anticoagulation in the presence of Heparin-induced thrombocytopenia (HIT) and thrombosis. A small study compared to ancrod to heparin in preventing thrombosis when given to people undergoing arterial graft surgery to treat peripheral arterial disease and found little difference between the two agents. Ancrod was intensively studied in ischemic stroke, starting at least by the early 1990s. An RCT called "STAT" was published in 2000; it included 500 subjects and ancrod or placebo was administered within three hours of the stroke. Ancrod showed modest benefits but a trend toward increased intracranial haemorrhage. A clinical trial published in 2006 found no benefit if ancrod was given within a wider 6 hour treatment