Instead, British and French experts say that healthy HIV carriers should be discouraged from taking AZT until they develop symptoms of Aids.
The scientists argue that viral resistance to AZT - which is linked to how long the drug is used - is an important factor in deciding if a patient should take it early. Resistance to the drug is a worrying problem as long as AZT remains the leading treatment for the full-blown disease.
The long-awaited conclusions of the Anglo-French Concorde trial, a three-year study of almost 1,740 HIV-positive individuals which will be published in the Lancet tomorrow, confirm that AZT does not ultimately improve survival or slow the disease in healthy HIV-positive people. They do report a 'an early but transient' clinical benefit.
Preliminary findings published a year ago suggested that it was unlikely AZT would be improve the outcome for healthy HIV positives, but Wellcome, which makes the drug under the brand name Retrovir, had criticised interpretation of this data as 'preliminary and incomplete', and said that its conclusions were misleading.
AZT accounts for about 12 per cent of Wellcome's pounds 2bn sales annually, and is a key contributor to its profits. In August 1989, the initial results of an American study suggested that the drug could delay the onset of Aids, and the company's share price leapt by one-third in a day.
Sir Dai Rees, chief executive of the Medical Research Council, which organised the trial with the French National Aids agency, said yesterday that since the preliminary report the data had been updated and more detailed analysis carried out.
'Although there are minor differences between the figures as a result of new information and clarification, these do not affect the original conclusions in any way,' he said.
Dr Trevor Jones, Wellcome's director of research, development and medical (UK), said that the study would 'rekindle' the debate as to the optimal time for HIV carriers to begin treatment. He said all trials had agreed that AZT delays disease progression, although there is disagreement as to how long this benefit lasts.
Concorde ran between October 1988 and October 1991, and HIV-infected patients were either given AZT immediately or when they developed Aids, or a related illness known as ARC, or if they had persistently low white blood-cell counts. The researchers concluded that there were no significant differences in survival after three years, or in progression of disease between the groups.
'The results of Concorde do not encourage the early use of zidovudine (AZT) as a monotherapy (single treatment) in symptom-free adults . . . The optimum time to start AZT remains unclear,' the scientists concluded.
'Any limited benefit in disease progression has to be balanced against toxicity and the impact of the long-term use of such drugs on quality of life.' A long-term follow-up of the patients in the Concorde trial is continuing.Reuse content