February 18, 2009
In a poster presentation at CROI 2009 in Montreal, Canada, data from the Australian STEAL study show Truvada (tenofovir + emtricitabine) is equal to Epzicom (abacavir + lamivudine) in their abilities to suppress viral loads. Each of the combination pills had unique side effects, which likely mark the major difference when deciding which therapy to choose.
STEAL enrolled 360 people on stable HIV regimens with 2 NRTIs plus either a NNRTI or protease inhibitor (PI). All had undetectable viral loads for at least 12 weeks at study entry. None were on unboosted Reyataz, had prior hypersensitivity to other HIV drugs, or were positive on an HLA-5701 test, which determines whether abacavir is likely to cause a severe allergic reaction.
Average age of the volunteers was 45 and the study included predominantly white (86%) men (97%). About 17% had been diagnosed with AIDS, length of time living with HIV averaged 10 years, and average CD4 count was around 620.
All continued either their NNRTI or PI, with half randomly assigned to take Truvada and the other half Epivir. The primary objective of the study was to look at failure to maintain an undetectable viral load. Researchers also gathered information on serious non-AIDS events, bone density levels (BMD), lipid levels and death.
Both Truvada and Epzicom were about equal at suppressing HIV levels. Epzicom was associated with more side effects in general than Truvada. Epzicom showed a higher risk of heart disease and more than double the risk for changes in lipid levels. However, Truvada showed a higher risk for changes in BMD with lower density scores found in the hip and spine. Though there were some cases of kidney and liver disease and diabetes in both groups, there were no significant differences between the two combination pills and their risks on these conditions.
Truvada and Epzicom suppress HIV levels and maintain CD4 counts at about the same rate. The decision to choose one over the other would likely come down to possible issues of side effect. Loss of BMD is a concern for many people living with HIV, so choosing Truvada may put a person more at risk for it. Truvada's side effects in general seem more tolerable than Epzicom's. On the other hand, Epzicom appears to cause more changes in blood fats and more heart disease, perhaps from the abacavir in it. Although abacavir has been implicated as a risk factor for heart disease, it's still unclear whether that's the case. Several studies presented at CROI 2009 show a connection though a few others do not.