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Response to anti-HIV therapy improved if treatment within 6 months after preventive regimen

January 11, 2007

Response to treatment diminished if treatment begins within 6 months of preventive regimen

A woman's response to HIV treatment with drug combinations that contain nevirapine is improved if at least six months have passed after she received the drug as a single dose during labor to prevent passing HIV on to her child. (The response to treatment is measured by the reduction of HIV in the blood.)

Conversely, the response to treatment with nevirapine-containing combinations is diminished if less than six months has passed since the preventive regimen.

These findings were reported by researchers funded in part by the National Institutes of Health and appear in the January 11 New England Journal of Medicine.

Nevirapine, given once during labor, alone or in combination with a short course of zidovudine (AZT) during pregnancy, provides an inexpensive, effective way to reduce the chances that a pregnant woman will pass HIV on to her child.

A single dose of nevirapine is a common preventive regimen given to pregnant women during labor in resource-poor countries where the standard, more expensive, multi-drug treatments are not widely available. Previous studies have indicated, however, that the single nevirapine dose could make the virus resistant to the drug, which may make it less likely that a woman will respond to nevirapine if she needs it later, as part of a multi-drug anti-HIV regimen, to safeguard her own health. The single dose of nevirapine eliminates most of the copies of HIV that infect a patient, except for a few mutant copies that are genetically resistant to the drug. Researchers were concerned that as these remaining mutants multiplied, mutant HIV would not respond to nevirapine when it was used later as part of a multi-drug regimen to treat HIV infection.

In many resource poor countries, nevirapine is a cornerstone of the three drug anti-retroviral therapy (ART) used to treat HIV disease in pregnant and non-pregnant women who need therapy for their own health. Typically, nevirapine is given in combination with AZT and lamivudine. In the United States and other developed countries, three drug combination therapy is also used to treat pregnant women and non-pregnant women who require therapy for their own health. However, in developed countries, the three-drug combinations usually include the more expensive protease inhibitors, instead of nevirapine.

"The findings show that single dose nevirapine during labor alone-or with short course AZT during pregnancy-remains a viable option in resource-poor settings for preventing the spread of HIV from mother to child among pregnant women who do not yet require anti-HIV treatment for their own health," said Duane Alexander, M.D., director of the National Institute of Child Health and Human Development. "The findings also underscore the importance of immediately beginning a multi-drug treatment regimen for pregnant women who require treatment for their own health, but which does not contain nevirapine."

The study findings are consistent with World Health Organization recommendations that all HIV-infected pregnant women be tested to identify those in immediate need of treatment, explained the NIH project officer for the study, Lynne Mofenson, M.D., Chief of the Pediatric, Adolescent and Maternal AIDS Branch at NICHD.

To conduct the current study, the researchers followed 218 women in Botswana, who volunteered for a prior study to test the effectiveness of nevirapine in combination with AZT in preventing the spread of HIV from mothers to their children. In the prior study, which enrolled 1,200 women and infants between March 2001 and October 2003, all women received a course of AZT from the 34th week of pregnancy to delivery. Women and their infants were randomized during the study. Women received a single dose of nevirapine given at the beginning of labor, or a placebo. Infants received a single dose of nevirapine at 48 to 72 hours after birth, or placebo.

Combination antiretroviral therapy, which included nevirapine, became available in Botswana starting in October 2002 for all pregnant or postpartum women who required treatment for their own health.

The current study enrolled volunteers from the earlier study who later needed multi-drug therapy for their own health after they had given birth. Of these volunteers, 112 women originally had been randomized to receive single dose nevirapine and another 106 women originally had been randomized to receive nevirapine placebo in the original study.

In the current study, 60 women required ART within six months after receiving either single dose nevirapine or placebo during labor. Of the women in the nevirapine group, 41.7 percent still had detectable HIV levels in the blood after receiving six months of ART, indicating that the ART was not effective. In the placebo group, none of the women receiving the nevirapine placebo had detectable HIV in the blood after six months of ART.

However, the rates of detection of HIV in the blood did not differ significantly among the other 158 women, who started treatment at least six months after receiving single dose nevirapine or placebo. Of these, 12 percent of the nevirapine group and 7.8 percent of the placebo group still had detectable HIV levels after receiving six months of ART, indicating equal effectiveness of ART in both groups.

The study authors wrote that their findings are consistent with observations that while nevirapine-resistant strains of HIV could be present after a single dose nevirapine regimen, these strains begin to fade with time and eventually make up a minor proportion of HIV strains in a patient.

The study authors concluded that nevirapine-based ART is an option for women who require therapy six months or more after receiving a single dose nevirapine preventive regimen. They also wrote that some women given single dose nevirapine will require ART treatment before six months have passed, and these women should receive ART that does not include nevirapine.

The authors added that "every effort should be made" to provide combination ART during pregnancy to women who need it for their own health, as these women are at highest risk for AIDS-related complications or death, for passing HIV on to their infants, and for developing nevirapine resistance after a single dose of the drug.

The researchers also evaluated the response of HIV in the blood to ART in a subgroup of infants from the prior study that had become infected despite preventive drugs and who later required ART. The researchers were able to follow 24 infants for six months, with 13 having received single dose nevirapine and 11 having received placebo; one infant in the placebo group, and 10 infants in the nevirapine group had HIV detectable in the blood after 6 months of ART.

The study authors noted, however, that it was difficult to draw firm conclusions from the small number of infants studied, and added that additional information from other studies would be helpful. A randomized, controlled clinical trial to evaluate the best treatment for infected infants with and without single dose nevirapine exposure is currently being conducted by the International Maternal, Pediatric, Adolescent AIDS Clinical Trials Group, sponsored by the NIH's National Institute of Allergy and Infectious Diseases and the NICHD.

NIH/National Institute of Child Health and Human Development