A novel solution phase PAI-1/uPA-biotin complex assay for the measurement of active PAI-1 in plasma

Abstract We devised a new assay procedure to use biotinylated uPA to trace the active PAI-1 levels in the plasma. We show here that the potency of inhibitory monoclonal antibody 33B8 measured with the new assay is consistent with its in vivo efficacy in PAI-1 inactivation. We also found that among the three monoclonal antibodies tested, the traditional solid phase assay caused mechanism dependent significant right shift of IC 50 values. As our new assay avoids the use of non-physiological large quantities of uPA, we conclude that it is a better measure of pharmacodynamic effects of anti-PAI-1 antibodies in vivo .