Proteases (also sometimes referred to as proteolytic enzymes or peptidases) are in use, or have been proposed or tried, for a number of purposes related to medicine or surgery. Some preparations involving protease have undergone successful clinical trials and have regulatory authorization; and some further ones have shown apparently useful effects in experimental medical studies. Proteases have also been used by proponents of alternative therapies, or identified in materials of traditional or folk medicine. A serine protease of human origin, activated protein C, was produced in recombinant form and marketed as Drotrecogin alfa (also known as Xigris (TM)) and licensed for intensive-care treatment of severe sepsis. It was voluntarily withdrawn by the manufacturer in 2011 after being shown to be ineffective. Some of these uses rely directly on the proteolytic activity: others rely on observations of anti-inflammatory activity. Medical and surgical applications Treatment of blood clots in ischemic stroke Tissue plasminogen activator (TPA) is a serine protease occurring in animals including humans. Human-identical TPA (produced industrially by genetically recombinant microorganisms) has an established medical use in the treatment of ischemic stroke: by its proteolytic activity it enables the action of another enzyme (plasmin), which breaks down the protein (fibrin) of blood clots. Venombin A from snake venom were used in stokes to deplete fibrinogen by forming very weak clots that can be easily dissolved. Available evidence does not support any benefit in such usage. Wound debridement Debridement involves the removal of dead or damaged tissue from wounds in order to assist healing. Much of the debris to be removed is proteinaceous, and proteolytic enzymes have been applied to this purpose. Papain is a protease obtained from the latex of the fruit of the papaya tree. It has been used (without regulation) for wound debridement for many years, but in the US in 2008 it was brought under regulation by the U.S. Food and Drug Administration and removed from sale for this purpose, following reports of adverse effects. On the other hand, recent research has been exploring new ways of administering papain for wound debridement. Papain as well as other proteases, including bromelain, collagenase, trypsin and thermolysin, have also been tried or used according to other reports on the use of proteases for debridement of wounds and burns without damaging healthy tissue. Maggot therapy for wound debridement is a traditional therapy which was in recent years approved by the FDA. It