Combination regimens trump monotherapy in fight against HIV transmission

By Piriya Mahendra

A two- or three-drug combination is more effective at reducing intrapartum HIV acquisition than zidovudine (AZT) monotherapy in babies who are at high risk for transmission, a study in The New England Journal of Medicine shows.

The randomized controlled study of 1684 formula-fed infants born to HIV-positive mothers also showed that the two-drug regimen, which comprised AZT and nevirapine, was less toxic to infants than the three-drug regimen with AZT, nelfinavir, and lamivudine.

The authors note that their findings are applicable only to babies whose mothers do not receive antiretroviral therapy during pregnancy and are therefore at high risk. They point out that babies born to HIV-positive women who are effectively treated with antiretrovirals throughout pregnancy already have less than a 1% chance of acquiring HIV.

In a press statement, Karin Nielsen-Saines (University of California, Los Angeles, USA) remarked: "Our research demonstrates that even in very high-risk situations where mothers are only identified as being HIV-positive when they give birth or shortly after birth, there is still an effective strategy that can be undertaken to prevent transmission of HIV to the baby."

Intrapartum HIV transmission occurred in 24 (4.8%) infants who received AZT only compared with 11 (2.2%) infants who received the two-drug regimen, and 12 (2.4%) infants who received the three-drug regimen.

"While giving AZT alone to the infant can reduce intrapartum transmission to some degree, our data demonstrate that with the use of two- or three-drug regimens to the baby, you can cut transmission to half of what can be achieved with AZT alone," Nielsen-Saines commented.

Multivariate analysis revealed that AZT monotherapy, a higher maternal viral load, and maternal use of illegal substances were significantly associated with a higher rate of transmission.

The results also showed that the rate of neutropenia was significantly higher in infants on the three-drug regimen than in those who received the two-drug regimen and those who received monotherapy, at 27.5% versus 14.9% and 16.4%.

The infants included in the study were from the USA, Brazil, Argentina, and South Africa. Within 48 hours of birth, they were randomly assigned to one of three groups: AZT monotherapy for 6 weeks (n=566), AZT for 6 weeks plus three nevirapine doses during the first 8 days of life (n=562), or AZT for 6 weeks plus nelfinavir and lamivudine for 2 weeks (n=556).

Overall, 140 were infected with HIV: 97 acquired the infection during pregnancy, and 43 acquired it during the birth process.

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