Extensive prolongation of rabbit kidney allograft survival after short-term cyclosporin-A treatment.

The fungal metabolite cyclosporin A has been administered daily at 25 mg/kg to nephrectomised rabbit recipients of a single renal allograft. After only 4 weeks of daily administration, rejection was prevented for long periods without the need for other immunosuppressive therapy. Renal function has been excellent in all cases, rejection episodes have not been encountered except in a small percentage of animals, and the surviving recipients are still in excellent health 3-6 months after transplantation. The possiblity that clones of responding lymphocytes might be selectively killed by this agent was suggested from earlier experiments and prompted this study. If toxicity is not encountered in man cyclosporin A may prove valuable in preventing rejection of organ and bone-marrow allografts and might be useful in treating some leukaemias of lymphoid origin.