July 16, 2003
Considering body fat redistribution (lipodystrophy) rates is important when selecting an initial treatment. This study compared body fat redistribution among those starting therapy with either atazanavir (ATV, Reyataz) or efavirenz (EFV, Sustiva), each given in combination with Combivir (AZT [zidovudine, Retrovir] + 3TC [lamivudine, Epivir]). The data presented here helps both patients and clinicians determine which treatments are most favorable when it comes to minimizing alterations in body fat. As shown however, there was minimal change overall, and no difference between these two agents on any significant outcome at this time point.
This study was done with a subset (about a quarter) of the people who initiated treatment for the first time on a study called BMS 034. The primary results of this study have been presented previously at several conferences in the past year, and overall showed quite similar responses in terms of viral suppression rates.
One major reason for interest in this substudy result was that atazanavir has already distinguished itself as different from other protease inhibitors in that it does not have the lipid (cholesterol, etc.) disturbances that have been seen with several other protease inhibitors. Therefore there was some interest to see if this distinction would translate into this aspect of fat metabolism.
Measurements were obtained by both CT scans and DEXA scans, two different technologic assessments of fat distribution. Only results up to week 48 are available at this point. Based on the results from DEXA scanning, there were no significant differences in the overall changes observed in body fat in either arm, nor was there any significant difference between the two arms of the study. Focusing specifically on the CT results looking at the abdominal fat, there was a small increase in visceral fat in both arms of the study, and an even smaller increase in subcutaneous fat. These differences in change from baseline were very similar in the two regimens and may reflect in part improvements to lipoatrophy caused directly by the HIV virus.
There was slightly more weight gain noted on the atazanavir arm. Finally, the study results confirmed the lack of significant impact of atazanavir on blood lipids, and the minimal increase in most lipid values seen with efavirenz. Similarly, there was little impact on blood glucose and fasting insulin levels and no differences of any significance between these two regimens.
Overall, these results are encouraging with regards to the safety of these two regimens. That said, these results only reflect an early look at the data. Other studies have shown more impact from treatment in year two versus the first year.
However, based on these data, it is reasonable to conclude that the impact on lipids and lipodystrophy can be successfully reduced as we discover newer antivirals that are able to control HIV replication without the side effects that have been so common with the medications that we've used so far.