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 It was voluntarily withdrawn by the manufacturer in 2011 after being shown to