October 26, 2008
A study presented at the joint 2008 ICAAC / IDSA meeting in Washington, DC found that people who switched from Combivir (zidovudine/AZT + lamivudine/3TC) to Truvada (tenofovir + emtricitabine/FTC) maintained their control of HIV replication, had improvements in blood lipids, but did not see improvements in limb fat.
The poster presentation showed results from a 48-week continuation of the earlier 934 study. That study lasted 144 weeks and compared Combivir to Truvada, both taken with Sustiva (efavirenz). In 934, people taking Combivir had the option of switching to Truvada or staying on Combivir after 144 weeks.
After 48 weeks, similar proportions of people in both groups had HIV levels below 50: 94% for Truvada and 90% for Combivir. On average, people who switched to Truvada gained 9 CD4 cells compared to an average loss of 6 for those who stayed on Combivir.
People who switched to Truvada experienced small improvements in their measures of blood fats. While HDL levels (good cholesterol) remained virtually unchanged in both groups, levels of LDL (bad cholesterol) and triglycerides declined more in people who switched.
Unfortunately, people who switched did not regain lost limb fat. In the first phase of the study, significantly more people taking Combivir lost limb fat, compared to those on Truvada. However, 48 weeks after the switch, there were no significant changes in either group.
This study supports other data showing that Truvada is superior to Combivir. Combivir was downgraded from preferred to alternative in the Federal Guidelines, in part due to the earlier results from 934. This continuation study shows that when people switch from Combivir to Truvada they are likely to maintain undetectable levels of HIV, might experience small benefits in blood fats, but are unlikely to see improvement in lost limb fat.