US researchers administered the drug, bortezomib, to six patients whose immune systems were attacking transplanted kidneys and who did not respond to traditional anti-rejection treatments.

In each case, the drug promptly reversed the rejection, improved organ function, provided prolonged reductions in antibody levels and suppressed recurrent rejection for at least five months.

'This has significant implications for transplantation and auto immune disease,' said study co-author Steve Woodle, chief of transplant surgery at the University of Cincinnati in Ohio.

Dr Woodle's team is currently conducting four clinical trials to expand upon these preliminary findings.

The drug's side effects proved to be both predictable and manageable and toxicity levels were much less than those associated with other anti-cancer agents, the study found.

'We are pleased to see its toxicities are similar in transplant recipients suffering from treatment-resistant mixed organ rejection,' said study co-author Jason Everly, an oncology pharmacist at the University of Cincinnati.

'We hope it will be a viable therapeutic treatment option in this patient group.'

Previous studies had found that B-cells play a large role in organ rejection by making immune proteins that attack transplants.

The drug targets these antibody-producing plasma cells and had been shown to suppress transplant rejection in the laboratory before Dr Woodle and his team tested it on patients.

The study was published in the journal Transplantation. -- AFP