The British trial could have involved 50 to 100 hepatitis B patients.
Despite adherence to the rigorous procedures demanded by the American federal drug authority for the testing of new treatments, the drug, fialuridine, has caused liver failure. Doctors now believe that the reaction was caused by some unexpected cumulative effects of the drug in the body.
Fialuridine, an anti-viral drug produced by Eli Lilly & Company, had been heralded as the cure for hepatitis B, a viral disease which affects 300 million people world-wide and can cause liver failure and death.
World experts in liver disease are shocked that a drug on trial should have had such drastic consequences for patients and disappointed that it is now almost certainly lost to medical science.
The American trial, approved by the US Food and Drug Administration, involved 20 patients, 15 of them attending the National Institute of Health in Washington, the premier research centre in the US.
Dr Allan Weinstein, vice-president of Lilly Research Laboratories, Indianapolis, said that three patients had received liver transplants, of whom two had died. Three other patients might need transplants in the future, he said.
'Right now we have two goals: to make sure that the patients involved have the best possible care and then to accumulate all the data as quickly as we can. Then we may be able to understand what has been going on.'
Eleven of the patients involved had been given fialuridine as part of an earlier trial last year. All six patients belonged to this group.
Dr Roger Williams, director of the Liver Unit at King's College Hospital, south London, who attended an international meeting of liver experts in Washington last week, said that the adverse reaction appeared to be related to the dose.
'The patients affected developed a widespread toxicity involving the liver and the damage seems to be related to a cumulative effect. It has been a great shock to everyone involved,' he said.
Hepatitis B is an infectious disease which is usually passed by sexual or blood contact. Until blood was screened for hepatitis B, people became infected via transfusions. However, the infection is more commonly associated with the sharing of needles by drug addicts and with homosexual practice. It can persist for many years and can lead to chronic hepatitis, in which liver cells are destroyed, leading to cirrhosis of the liver.
There is no effective drug currently available for hepatitis B. The only treatment, used in severe cases, is interferon, which is only 30-40 per cent effective.