A Search for Synergy in the Binding Kinetics of Trastuzumab and Pertuzumab Whole and F(ab) to Her2

Lua WH, et al., doi:10.1038/npjbcancer.2015.12, npj Breast Cancer, 2015

It has been reported that the survival rate of Her2 overexpressing breast cancer patients can be improved significantly by combining the antibodies Trastuzumab and Pertuzumab in their treatments. However, the exact molecular mechanism underlying this clinical observation is not understood well. A recent molecular modeling study hypothesized colocalization of the two antibodies onto the extracellular domain of Her2 may lead to enhanced affinities. Reported in the current study are the efforts towards experimental characterization of the interaction between antibodies, Trastuzumab and Pertuzumab, their binding kinetics, and also the binding of their F(ab)s to the extracellular domain of Her2. Bio-Layer Interferometry (BLI) was used to assess the binding affinities. A Pall ForteBio BLItz instrument equipped with HIS-tagged Her2 captured Ni-NTA biosensor probes was used to perform BLI assays. Antibodies were successively loaded onto Biosensor tips in order to measure synergistic binding of whole antibodies and their F(ab)s. Kinetic parameters (ka, kd, and KD) were determined based on the binding curves. Overall results demonstrate that both Trastuzumab and Pertuzumab, whether it is the whole antibody or the fragments can bind simultaneously to Her2. However they do not enhance the binding of each other.

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