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Mexican Study May Forecast Advanced Naives

By Paul Dalton

September 2008

Data from a study called the "Mexican 5142 study" were presented August 5 at the International AIDS Conference. The study, a head-to-head study of Sustiva (efavirenz) vs. Kaletra (lopinavir + ritonavir) in people with CD4 counts below 200 who start first line HIV therapy, showed Sustiva to be more potent than Kaletra in this group.

This study enrolled 189 people in several centers around Mexico. Everyone had CD4 counts below 200/mL and had never taken HIV treatment. The presenter, Dr. Sierra Madero, pointed out that in Mexico, and throughout Latin America, this is a common situation for first line HIV therapy.

Participants were randomly chosen to take either the older, soft gel Kaletra or Sustiva, along with the fixed-dose combination Combivir (zidovudine/AZT + lamivudine/3TC). The primary endpoint of the study was the proportion of people with HIV levels below 50 copies/mL after 48 weeks. They also looked at changes in CD4 counts. A total of 85% of the participants were male, and the average CD4 count at the start of the study was 64 for the Kaletra group and 52 for Sustiva.

After 48 weeks, 70% of people on Sustiva had HIV levels below 50 copies, compared to 54% on Kaletra. Interestingly people taking Kaletra had slightly larger gains in CD4 counts: 167 cells vs. 157. More people stopped their treatment in the Kaletra group: 34% vs. 27%. There were also greater increases in total cholesterol (62 vs. 53 mg/DL) and triglycerides (62 vs. 167 mg/DL) in people taking Kaletra compared to Sustiva.

It's important to point out that the older, soft gel formulation of Kaletra was used in this study. Some studies have shown higher rates of gastrointestinal side effects in people using the soft gel, compared to the newer hard capsule version. This might explain part of the differences seen in discontinuations and treatment failures.

This study is of similar design to the ACTG 5142 study, which also compared Sustiva to Kaletra as first line treatment. The major difference is that the people in this study had lower average CD4 counts and more advanced disease.

This study is interesting for several reasons. First, while US treatment guidelines recommend starting treatment well before it was started in this study, a growing number of people, both worldwide and in the US, are being diagnosed with HIV with low CD4 counts. Information on treatment outcomes for this group is particularly important.

Second, for many years it was commonly believed that boosted protease inhibitors, like Kaletra, were more potent than NNRTIs. This study suggests this may not be true.

Lastly, this study confirms the finding from many other studies that boosted protease inhibitors tend to lead to larger increases in CD4 cells than NNRTIs.

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