The New York Times - July 10, 2004
Donald G. McNeil Jr.

The drugs, nevirapine and AZT, are relatively cheap and widely available in generic form. The studies, which will be published in The New England Journal of Medicine next week, were released yesterday because they will be presented at an international AIDS conference in Bangkok.

The World Health Organization, aware of the promising results beforehand, has begun to recommend the use of the two drugs together.

Most poor countries that have programs to protect the newborns of infected mothers have used either drug alone. One dose of nevirapine, also known by the brand name Viramune, is given to the mother during labor and one to the child before it is three days old. The whole treatment costs less than $5.

Treatment with AZT, also known as ziduvodine or Retrovir, usually begins weeks earlier for the mother, lasts days or weeks for the child and costs about $40.

With use of the two together, the virus is transmitted in only about 2 percent of births. That success rate is "near those seen with the current, more complex and expensive treatments used in the U.S.," said Dr. Lynne Mofenson, chief of the pediatric AIDS branch of the National Institute of Child Health and Human Development, part of the National Institutes of Health, which helped pay for the studies.

Mothers who are not treated at all have a 25 to 50 percent chance of infecting their children at birth or through breast-feeding. About 700,000 children were infected that way last year, the W.H.O. estimated, 90 percent of them in Africa.

The results of the new studies were "great news," said Dr. Heather Watts, a medical officer at the child health institute. Such low transmission rates "are phenomenal, better than we expected," she added.

But one of the two studies also found that even a single dose of nevirapine seemed to raise the chance that a mother would develop a nevirapine-resistant strain of the AIDS virus. That worrisome result "needs further study," Dr. Watts said.

AIDS experts in South Africa, where the nevirapine-only approach is widely used, have raised medical and moral questions about it. It does save the lives of many babies, they noted, but leaves them orphans because it does nothing to save the mother and may also raise the chance that she will develop a drug-resistant virus. Later, if the mother is lucky enough to go on daily antiretroviral triple therapy, it will be harder to save her life.

The new studies involved the same group of 1,800 pregnant women in Thailand who were followed from January 2001 to March 2003. One study assessed how readily women on different drug combinations infected their children, the second followed women with weak immune systems.

The follow-up study found that women given even one dose of nevirapine alone had low levels of the drug in their blood for up to three weeks. That kills strains of the virus susceptible to nevirapine, leaving resistant strains to survive and multiply. The danger is that nevirapine and all the other drugs in its class, the non-nucleoside reverse transcriptase inhibitors, may become useless for treating the women who received it and the sexual partners they subsequently pass the strain on to.

Only a single mutation in the virus gene is needed to create resistance to the non-nucleosides. Resistance to AZT, when it is misused, usually takes weeks to develop.

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