A combination of two or more of the drugs, known as protease inhibitors, has shown 'positive' results, according to Dr Michael Saag, director of the Aids clinic at the University of Alabama, Birmingham, in the United States.
About a dozen pharmaceutical companies, including Abbott, Searle and Roche, are developing the drugs, which work by stopping the virus from 'splicing' up long protein strands which it needs to do if it is to replicate and infect more body cells.
Initial problems of viral resistance have been overcome with the newer inhibiting agents, Dr Saag told the 10th international conference on Aids in Yokohama, Japan, yesterday. However, he warned that progress would be slow: 'It's going to be a slow, evolutionary process. Under the best scenario, three years from now we may be getting excited by a certain combination of drugs.'
As prospects for a breakthrough in Aids research grow increasingly bleak, the focus is shifting to ways in which the immune system can be better protected. Dr David Barry, group director of research, development and medical affairs for Wellcome, which makes AZT, told the conference: 'Our goal is, through new drugs and new treatment strategies to create an assault on the virus which will restore the normal lifespan of the HIV-infected person.'
The company has five new drugs for HIV treatment in clinical development, including a protease inhibitor. Three of the drugs work in the same way as AZT, and the fourth is an 'immunomodulator' known as Tucaresol, which primes the immune system, according to preliminary studies.
Dr Barry said that test-tube studies with three drug combinations showed 'complete suppression of evidence of viral replication at concentrations of drug easily attainable in the blood'.
Peter Piot, director of Aids research at the World Health Organisation, said that women continued to bear the brunt of Aids and HIV, and other sexually transmitted diseases (STDs). Around 3,000 women are infected with HIV every day and 500 die from Aids, according to the United Nations. Persistently high levels of STDs in developing countries were due to failed health policies and lack of effective education programmes. This left millions of infected people, particularly women, untreated and at risk of complications.
'Basically, STDs have rarely been approached as a public health problem, but rather as a problem for a small group of blameworthy individuals,' Dr Piot said.
In many cultures, men believe they have the right to dominate sexual relationships, which is why many do not use condoms to protect their partners, the conference was told.