Possible use of monoclonal antibodies to standardize the production and use of human urokinase.

Urokinase, a plasminogen activator found in urine is used in the treatment of pulmonary embolism, and is supplied commercially by several companies in Europe, U.S.A. and Japan. It exists in two forms, of molecular weights 50-55 000 and 33 000 daltons, which may differ in their therapeutic efficiency. A variety of assay systems exist to measure plasminogen activator activity--clot lysis, casein hydrolysis, amidolytic cleavage of synthetic peptide substrates. These assays are time-consuming, relatively insensitive, and cannot accurately assess the amount of the two molecular species in any preparation of urokinase. Standardization therefore presents a problem to manufacturers, control agencies, and clinicians. We have prepared a variety of monoclonal antibodies to human urokinase and have assessed their value as standardizing different commercial preparations of urokinase and measurement of urokinase for therapeutic monitoring.