The protease known as "Tissue Plasminogen Activator" or TPA has been available for around ten years and is the main subject studied by Professor Denis Vivien's group. It has allowed major advances to be made in the management of Stroke, significantly reducing mortality rates. Strokes are caused by obstruction of a cerebral artery by a blood clot. Large areas of the brain are then deprived of nutrients, oxygen and glucose, resulting in death of the area of the brain. The role of TPA is to disperse clots. However, it does have disadvantages which have been studied for several years.