Altered biodistribution of an antibody--enzyme conjugate modified with polyethylene glycol

Polyethylene glycol modification of the antibody--enzyme conjugate, F(ab')2-A5B7-CPG2, extends its duration in the circulation of nude mice bearing human colonic cancer xenografts (LS174T). Increased concentration of modified conjugate is achieved in the tumour, but residual non-specific enzyme concentrations in normal tissue and blood demonstrate the fundamental requirement to remove or inactivate non-specifically held enzyme in this system.