THE EFFICACY of azidothymidine (AZT) in delaying the onset of AIDS symptoms is in serious doubt following a three-year study in Europe, which indicates it makes little difference whether AZT treatment starts early or late.

The Anglo-French study, called Concorde, found 29 per cent of the volunteers who took AZT as soon as they knew they were HIV-infected developed full-blown AIDS. The figure for those who began AZT treatment much later was just 3 per cent more. The Concorde results contradict the findings of an American study that suggested AZT could benefit HIV-infected patients who had yet to develop AIDS symptoms.

AZT, produced by Burroughs Wellcome, was licensed for treating AIDS patients in 1987. Two years later, the drug's licence was expanded to treat HIV patients who have not developed AIDS symptoms. It is this category of HIV patients, numbering about 10 million worldwide, who will be hurt most by AZT's failure.

The Concorde study, first published in UK in The Lancet, has stirred a hornet's nest among AIDS researchers, HIV patients and drug manufacturers. Predictably, Burroughs Wellcome and some AIDS researchers have raised questions about Concorde and urged doctors not to accept the findings until the data is thoroughly analysed.

But other researchers seem convinced and New York-based AIDS researcher Mark Harrington commented, "It's a terrible result. It undermines the foundation for early AIDS care."

Rattled by the Concorde study, the AIDS community is now awaiting the findings of another major AZT trial being conducted by Australian and European researchers.