Suppression of well-established tumour xenografts by a hybrid-hybrid monoclonal antibody and vinblastine.

The hybrid-hybrid monoclonal antibody 28-19-8 has specificity for the tumour-associated antigen carcinoembryonic antigen and the vinca alkaloids. This bifunctional antibody has been used to target unmodified vinblastine sulphate to well-established MAWI human tumour xenografts implanted in nude mice. The highly significant suppression of tumour growth achieved throughout treatment has also been sustained for over 2 months after the withdrawal of treatment. Histological examination of excised tumours from treated animals has shown profound changes in their morphology when compared with tumours from control animals. Cells in tumours that had started to grow again after withdrawal of therapy were shown still to express carcinoembryonic antigen, the target antigen recognised by the bispecific antibody.