September 15, 2003
This summer the results of ACTG 5095 were presented at The 2nd International AIDS Society Conference on HIV Pathogenesis and Treatment in Paris (click here for a summary), after being widely disseminated in the spring. ACTG 5095 showed that the combination medication Trizivir (containing abacavir [ABC, Ziagen], 3TC [lamivudine, Epivir] and AZT [zidovudine, Retrovir]) did not do as well as the two arms that contained efavirenz (EFV, Sustiva). These two arms were Trizivir plus efavirenz and Combivir (AZT and 3TC) plus efavirenz. The two efavirenz-containing arms at this point were not different, and that part of the study was allowed to continue, but the Trizivir arm was stopped.
ACTG 5095 was important in that it demonstrated clearly that the three-nucleoside regimen in Trizivir was not quite as potent as the efavirenz-containing regimens. Earlier studies showed that among patients with a high baseline viral load, Trizivir-like regimens were not as effective as some conventional HAART regimens, so this was not a huge surprise. That having been said, the effectiveness of the Trizivir in 5095 was not bad in overall terms. Thus, many still wonder what the role of this very simple, safe and easily tolerated regimen will be.
This study was an attempt to add more real-world data to the debate, by seeing how Trizivir compared to NNRTI-containing regimens in daily practice. The authors looked at 100 consecutive patients in their practice in Madrid who received either Trizivir or AZT and 3TC with either efavirenz or nevirapine (NVP, Viraume). The study was not randomized, meaning that the physicians and the patients chose the regimen based on clinical preferences and prejudices. While this is not the ideal scientific way to answer a question, it may test whether doctors can tailor a regimen to a patient so well that different results are seen than would be seen in a randomized, scientific trial.
Well, the real-world experience matched the clinical trial experience. Despite the lack of randomization, the two groups were fairly similar in baseline characteristics. After 24 weeks, the group on the NNRTI-containing regimens did considerably better with regard to reaching and maintaining a viral load below 50 copies. This was true when analyzed by intent-to-treat methods (counting people based on the initial regimen and considering a switch equivalent to failing): 51 percent versus 67 percent. This also holds true when looking at those who remained on their initial treatment (on treatment analysis): 78 percent versus 95 percent. Similar results were seen at 48 weeks and in multivariate analysis, in which the analysis was adjusted for baseline features.
Does this study give us any new information? Probably not. It confirms the results of ACTG 5095, both by showing that NNRTI regimens are more potent than Trizivir and that the overall results for Trizivir are not bad, compared to the regimens of a few years ago. However, we have regimens that can succeed in more than 90 percent of people who remain on therapy or more than 75 percent overall, and in general, those would seem to be better options. Still, the best medicine for a patient is the one they take, and there may be some patients for whom Trizivir is the most medicine they are willing and able to take. This debate is not over.
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