Galactosylated antibodies and antibody‐enzyme conjugates in antibody‐directed enzyme prodrug therapy

Antibody directed enzyme prodrug therapy (ADEPT) has been studied as a two- and three-phase system in which an antibody to a tumor-associated antigen has been used to deliver an enzyme to tumor sites where it can convert a relatively nontoxic prodrug to a cytotoxic agent. In such a system, it is necessary to allow the enzyme activity to clear from the blood before prodrug injection to avoid toxicity caused by prodrug activation in plasma. To accelerate plasma clearance of enzyme activity, two approaches have been studied. The studies have been performed with a monoclonal anticarcinoembryonic-antigen antibody fragment A5B7-F(ab') 2 conjugated to a bacterial enzyme, carboxypeptidase G2 (CPG2), in LS174T xenografted mice