A combination of two drugs taken over a period of more than two years led to a fall in death rates of nearly 40 per cent. It is the first Aids drug trial to show a significant, long-term benefit in extending a patient's life expectancy.
Medical researchers con-ducting the effort, which involved 3,000 patients in eight European countries, claimed yesterday that the results were the most important to emerge in nearly a decade of research into Aids treatment.
Britain's Medical Research Council, which took a lead in the investigation, will announce the results today at a scientific meeting in Copenhagen. It has already recommended that Aids patients should begin taking a combination of at least two anti-HIV drugs.
The drugs in question are compounds known to interfere with the ability of HIV to replicate. One of them, AZT, made by the British company Wellcome, has been used since 1986 but was partially discredited as a single-drug therapy after it was shown in 1993 not to prevent healthy HIV-positive people from developing Aids.
However, the so-called Delta trial used AZT together with one of two other antiviral drugs - ddI and ddC, made respectively by Bristol Myers Squibb of the United States and Roche of Switzerland. "The reduction in death rate over the course of the trial was 38 per cent for patients who took two drugs compared with those who took AZT alone," the MRC said.
Brian Gazzard, clinical director of the Aids unit at the Chelsea and Westminster Hospital in London and Britain's main investigator on the Delta trial, said: "It's the first trial to show an improvement in long- term survival of Aids patients."
Although the trial does not resolve the issue of when is the best time to begin treatment - whether with healthy HIV-positive people or those showing signs of Aids - Dr Gazzard said the advantages of taking two drugs were clear: "If you're thinking of starting treatment, you should start with combination therapy, not AZT alone."
Dr Gazzard said it would cost between pounds 3,000 and pounds 5,000 a year to treat an Aids patient with two antiviral drugs.
The best improvements in survival occurred in patients who had not previously taken AZT by itself. The Medical Research Council said it was "too early to say whether or not those who have already taken AZT may benefit from combination therapy".
Nevertheless, patients on the trial taking AZT alone have now been offered the chance of having it in combination with ddI or ddC because scientists considered it unethical to continue single-drug treatment in the light of the Delta results.
Tim Peto, a consultant in infectious diseases at the John Radcliffe Hospital in Oxford, said yesterday that the research was the most significant in anti-Aids drugs since 1986, when it was found that AZT gave a short-term benefit for Aids patients. "We're not trying to say `this is it', we're saying it's a significant clinical advance," he said.
Nick Partridge, chief executive of the Terrence Higgins Trust, an Aids charity, said the Delta results were "good news" after two years of disappointments and setbacks. "Although we are a long way from a cure, these results renew hope, improve current treatment and encourage researchers looking at other combinations of drugs."
Mr Partridge stressed that the trial did not provide all the answers. "While these drug combinations can slow progression to Aids they do not prevent it, and the increase in life expectancy is still quite small. Delta does not clarify when to start treatment, how long to take the drugs, or which combination is most effective," he said.