People on Sustiva Have Less Risk for Treatment Failure Than People on Kaletra

July 22, 2009

By David Evans

People taking a regimen containing efavirenz (found in Sustiva and Atripla) appear to have less chance of virologic failure on treatment than people on a regimen including lopinavir/ritonavir (Kaletra), no matter their initial CD4 count. The study was presented at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town by Heiner Bucher, MD, MPH, from the University Hospital Basel in Switzerland. The study and adds another voice to a chorus of conflicting previous studies comparing the two treatments.

One of those studies, ACTG 5142, was first presented in 2006 at the International AIDS Conference in Toronto. That study found that although the two treatments were comparable, people on lopinavir/ritonavir seemed to reach treatment failure more quickly but had greater CD4 cell increases than people on efavirenz.

In the current study, which had a longer follow-up period than ACTG 5142, researchers looked at the medical records of 1,201 people enrolled in the Swiss HIV Cohort Study. In that group, 660 patients took an efavirenz-based regimen and 541 took a lopinavir/ritonavir-based regimen. Although virologic failure rates were similar, people on lopinavir/ritonavir were more likely to experience virologic failure than people taking efavirenz. This result held up even when a person’s CD4 count before staring treatment was taken into account.

In terms of CD4 cell gains, people on efavirenz appeared more likely than those taking lopinavir/ritonavir to maintain a rate of CD4 cell increase consistent with data from the large international EuroSIDA Cohort Study. A difference between the two treatments in terms of CD4 gains, however, did not hold up when the researchers looked at people who started therapy with lower CD4 counts.

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