Publications & Reports

Reduction in the toxicity of aminopterin--monoclonal-antibody conjugates by leucovorin.

Rowland AJ, Pietersz GA
Austin Research Institute, Austin Hospital, Heidelberg, Vic, Australia.


Although aminopterin(AMN)-antibody drug conjugates have been demonstrated to have a greatly increased antitumor efficacy compared to the free drug, their use is limited by an increase in systemic toxicity manifested by weight loss and bone marrow suppression. Using a murine thymoma model (E3) in inbred mice, the toxicity of a sublethal dose of free AMN could be prevented by the administration of leucovorin 24 h following drug treatment, whilst maintaining the antitumour effect of the drug. The same rescue protocol completely abrogated the antitumour efficacy of AMN-antibody, although toxicity was also diminished. However, the later administration of leucovorin 48-72 h following a sublethal dose of AMN-antibody conjugates resulted in a maintenance of the anti-tumour efficacy of the immunoconjugates and a reduction in toxicity, with a mean percentage change in mouse weight not significantly different from that of the controls. These studies demonstrate that reversal of toxicity caused by AMN-antibody conjugates can be achieved by leucovorin while maintaining a powerful antitumour effect provided that the dose of leucovorin is administered 48-72 h after the conjugate.


  • Journal: Cancer Immunology, Immunotherapy
  • Published: 01/08/1994
  • Volume: 39
  • Issue: 2
  • Pagination: 135-139