MEASUREMENT OF KINETIC BINDING CONSTANTS OF A PANEL OF ANTI-SAPORIN ANTIBODIES USING A RESONANT MIRROR BIOSENSOR

We have used a resonant mirror biosensor to determine the kinetics of binding of four antibodies, and their Fab' fragments, to their antigen , the plant-derived ribosome-inactivating protein (RIP) saporin. The a nalysis of the affinity of the antibodies was in reasonable agreement with values obtained by conventional techniques. However, the kinetic data showed that all four antibodies have a high dissociation rate con stant (k(diss)). These antibodies have been used in the construction o f bispecific antibodies used to deliver saporin to tumour cells, and i t is highly probable that the in vivo efficacy of the bispecific antib odies is limited by the high rate of dissociation of antibody-toxin co mplexes.