Percolation and binding of monoclonal antibody BW494 to pancreatic carcinoma tissues during high dose immunotherapy and consequences for future therapy modalities.

The distribution of the monoclonal antibody (MAb) BW494 in human pancreatic carcinoma biopsies during high dose intravenous immunotherapy was investigated. Using immunohistochemical techniques combined with anti-idiotypic, endothelial cell-specific and bispecific MAbs, it was shown that 3 days after onset of immunotherapy, MAb BW494 was bivalently bound to tumour cells in some highly vascularised areas near capillaries. No binding was observed in other highly vascularised tumour cell areas although the epitope detected by MAb BW494 was present. In contrast to our expectation the majority of the tumour cells were not yet saturated by the antibody, probably due to diffusion barriers in the solid tumour tissue.