Plasminogen

Plasminogen is a zymogen produced in the liver which, when cleaved into its active form, breaks down fibrin blood clots. This active form, called plasmin or fibrinolysin, is generated when tissue plasminogen activator (tPA) or urokinase-like plasminogen activator (uPA) cleave plasminogen to begin the fibrinolytic pathway. Blood clots are broken down by plasmin into soluble fibrin and fibrinogen degradation products when the clot is no longer needed.

Type 1 plasminogen deficiency, also called hypoplasminogenemia, is a congenital disorder in which patients are deficient in plasminogen. Interestingly, this disease does not increase the risk of clotting, but rather results in the formation of lignous pseudomembranous lesions on the mucous membranes of the body. Lesions range in location and severity but can lead to severe long-term consequences if left untreated. For example, lignous conjunctivitis, the most common manifestation of type 1 plasminogen deficiency, may lead to corneal tearing and blindness.

Human plasminogen is administered topically (e.g. in eye drops) or intravenously (i.e. Ryplazim (https://www.fda.gov/media/149806/download)) in order to temporarily increase local or serum levels of fibrinogen. When this therapy is administered every 2 to 4 days, it prevents the build-up of lignous lesions and allows existing lesions to be shed.