ATLANTA - A short course of oral zidovudine (AZT, Retrovir, Glaxo Wellcome) given late in pregnancy and during delivery reduced the rate of HIV transmission to infants of infected mothers by half, according to the Centers for Disease Control and Prevention (CDC).
A study done by the CDC and the Ministry of Public Health in Thailand, which began enrollment in 1996, provides the first conclusive scientific data on the preventive effectiveness of a short-course regimen of AZT. The regimen evaluated in Thailand was AZT started at 36 weeks gestation and continued for the rest of the pregnancy. The drug was administered orally to women twice daily and during labor, and was not given to the newborns.
Interim results of the trial showed that this shortened regimen of AZT lowered the risk of perinatal transmission by 51% (from 18.6% without AZT to 9.2% with AZT). Although this reduction is not equivalent to that observed in ACTG 076, the longer regimen used in developed countries, this short-course is more applicable and feasible in the developing world and can have a significant impact on perinatal transmission in those countries.
"We are fortunate in the United States and Europe to have been in a position to offer preventive therapy to HIV-infected pregnant women for several years, and thousands of infections in infants have been prevented as a direct result," said Health and Human Services Secretary Donna E. Shalala, PhD.
Prior to these findings, ACTG 076, the only AZT regimen proven effective for perinatal HIV prevention, was out of the reach for the countries in which more than 90% of HIV infections occur.
ACTG 076 is costly and requires several months of treatment for the mother and the infant and an intravenous dose that is not feasible in many developing countries. For policy makers in developing countries to provide HIV-infected women a preventive therapy, they urgently needed conclusive scientific evidence that there is a practical treatment regimen that is safe and more effective than what they have been able to provide, which, tragically for most, has been no preventive therapy at all.
"By using a much shorter course during pregnancy, an oral dose rather than an IV dose during delivery, and no infant dose, we evaluated a regimen that could be realistically implemented in developing nations," said Helene Gayle, MD, director of the CDC's National Center for HIV, STD and TBPrevention. "Now, that the regimen has been proven safe and effective in Thailand, these findings offer hope of extending perinatal prevention to HIV-infected women throughout the developing world."
The Thailand study was one of two CDC collaborative perinatal HIV prevention studies. The CDC studies, conducted with the Ministries of Health in Bangkok, Thailand and Abidjan, Côte d'Ivoire, were part of an international collaborative research effort coordinated by the Joint UNAIDS to help identify practical solutions for the developing world.
These trials had been placebo controlled. Because of this preliminary data, the placebo-control arm of the CDC's Abidjan study is no longer necessary. Therefore, the CDC and its collaborators have begun offering all pregnant women enrolled in the Abidjan study the short-course AZT regimen. Research collaborators worldwide are currently being notified of the findings.
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