According to Glaxo, a majority of patients suffering from human immunodeficiency virus, the precursor to full-blown Aids, saw levels of the virus drop to undetectable levels following four weeks of treatment with two new compounds under development by the drugs giant. There was also no sign of any resistance to the combined treatment, a problem which has dogged some other anti-Aids drugs.
The news, released at a Washington medical conference yesterday, came alongside encouraging results from trials involving a "triple cocktail" of drugs using Glaxo's existing Retrovir (AZT) and Epivir (3TC) anti-Aids products in association with drugs developed by Abbott Laboratories and Merck, two US rivals to Glaxo.
Those tests offered hope for children who had inherited the HIV virus from their parents, seeming to suggest a cocktail of the drugs administered early could stop HIV in its tracks. Again, researchers stressed that it was too early to know for certain whether the drugs were completely effective.
Separately, DuPont Merck, a joint venture between the Delaware-based chemicals company and Merck, said an experimental drug known as DMP-266 in conjunction with another Merck treatment, Crixivan, had shown a fall in HIV blood counts below detectable levels in 82 per cent of patients.
The results of the new Glaxo drug trials, which were carried out by the University of Colorado Health Sciences Center, were greeted with cautious optimism by the company. Richard Kent, director of world-wide clinical research, said: "While it would be extremely premature to draw any conclusions based on such early results in such a small number of patients, we are encouraged by these initial reports."
Larger trials involving a variety of types of patient and different drug combinations were continuing, he added, "and we are working as quickly as possible to learn what their optimal role in therapy will be".
The new compounds involved are part of a new generation of anti-Aids drugs following on from Retrovir and Epivir. One, a so-called reverse transcriptase inhibitor codenamed 1592U89, was developed by Wellcome before its takeover by Glaxo as a successor to Epivir. The other is a protease inhibitor coded 141W94, which was invented by a US biotechnology company, Vertex Pharmaceuticals, and has been licensed to Glaxo.
The latest findings on the drugs' effectiveness in combination were released at the Fourth National Conference on Retroviruses and Opportunistic Infections in Washington. Five out of seven patients in the trial showed positive results, with the amount of virus in their bloodstream dropping to below 400 detections per millilitre, while infection-fighting CD4 cells increased over the four-week period. The drugs were said to be "well tolerated", although nausea is clearly a problem, forcing one patient to discontinue the treatment.
Even so, analysts are expected to generally welcome the results as confirming the value of combination therapy in the battle against Aids. Anthony Colletta of Glaxo's own brokers, Hoare Govett, said on Friday: "There are no fears about Glaxo's position in the HIV market... even on the most bearish forecast it will still have 50 per cent of the market by the year 2000."
By then he expects the group's anti-Aids portfolio to be generating sales of pounds 1.15bn, out of the total of pounds 5.6bn forecast to be coming from new drugs launched between 1993 and 2000. Within that, the 1592 compound will be turning over pounds 112m, while 141W sales could be pounds 121m, he believes. The trials on children, conducted by the University of Massachusetts, are similar to a study by leading Aids researcher David Ho. In his study of newly-infected HIV adults, he found that a mixture of Abbott Laboratories' Norvir with Glaxo Wellcome's AZT and 3TC could reduce the level of HIV in patients' blood to below detectable levels.
It also appeared to stop the disease's reproduction in the lymphoid tissue and elsewhere in the body.
He found similar effects with a mix of Merck's Crixivan and 3TC and AZT.