Toxicity of diphtheria toxin for lymphoblastoid cells is increased by conjugation to antilymphocytic globulin

THERE is a pressing need in medicine for cytotoxic agents with tissue specificity. It may be possible to produce such agents by conjugating cytotoxic materials, themselves lacking inherent specificity, to antibodies directed against surface antigens peculiar to target cells. Various agents, including cytotoxic drugs^1-7, radioactive materials⁸, radiosensitising agents⁹ and enzymes^10-11 have been covalently coupled to antitumour antibodies in attempts to produce such antitumour agents but so far these have not consistently produced cures in tumour-bearing animals. We, like others^12-16, have chosen to use diphtheria toxin because we consider that the paucity of tumour-specific antigens, accentuated, perhaps, by their restricted accessibility in solid tumours, necessitates the use of the most potent cytotoxins available.