In an effort to improve treatment convenience and adherence, researchers have studied various ways of simplifying antiretroviral therapy, including use of fixed-dose combinations that allow patients to take fewer pills per day.

As reported in a late-breaker session at the 4th International AIDS Society Conference on HIV Treatment, Pathogenesis and Prevention held last week in Sydney, Australia, investigators studied treatment outcomes in patients with fully suppressed HIV who switched to one of 2 fixed-dose combination pills:

• Truvada: tenofovir + emtricitabine
• Epzicom: abacavir + 3TC.

The open-label BICOMBO study included 335 participants in Spain with viral loads of less than 200 cells/mm3 who were receiving regimens containing 3TC (lamivudine, Epivir). Baseline characteristics were similar in the 2 arms. About 75% were men, the median age was 43 years, the median baseline CD4 cell count was about 500 cells/mm3, and about one-third were coinfected with hepatitis C virus.

Patients were randomly assigned to switch their current NRTIs to either Truvada or Epzicom, while staying on the same NNRTI or protease inhibitor. (Some subjects changed from individual drugs to the corresponding combinations pill, e.g., from separate emtricitabine + tenofovir to Truvada.) Subjects were not screened in advance for abacavir hypersensitivity.

Results

• After 48 weeks, significantly more patients in the Epzicom arm experienced treatment failure compared with the Truvada arm (19% vs 13%).

• Rates of virological failure were low in both arms: 2.4% of those taking Epzicom and none of those taking Truvada.

• CD4 cell counts increased more in the Epzicom arm (+44 cells/mm3) than in the Truvada arm (-3 cells/mm3).

• About twice as many patients in the Epzicom arm discontinued treatment early due to adverse events compared with the Truvada arm (10.2% vs 5.4%).

• In the Epzicom arm, 9 subjects had suspected abacavir hypersensitivity reactions.

• Patients taking Truvada had lower fasting triglyceride, total cholesterol, and low-density lipoprotein (LDL or "bad") cholesterol levels, but also had lower levels of high-density lipoprotein (HDL or "good") cholesterol.

• Among 47 patients who received DEXA fat measurements, there were no significant differences in limb fat changes in the 2 arms.

• Changes in creatinine and GFR (markers of kidney toxicity) were small and similar in both arms.

Conclusion

The researchers concluded that switching the NRTI component of an existing suppressive regimen to Epzicom was non-inferior to Truvada in terms of virological efficacy, but not in terms of overall treatment effectiveness.

The difference, they said, was "mainly driven by [Epzicom] interruptions due to suspected abacavir hypersensitivity." These data suggest that pre-screening patients using the new HLA-B*5071 genetic test might help select a subgroup of individuals who could benefit as much from Epzicom as from Truvada.

Hospital Clinic Universitari, Infectious Diseases, Barcelona, Spain; Principe Asturias, Medicina, Oviedo, Spain; Bellvitge, Infectious Diseases, Barcelona, Spainl; Vall d´Hebron, Infectious Diseases, Barcelona, Spain; Hospital del Mar, Infectious Diseases, Barcelona, Spain; Clinico San Carlos, Medicina, Madrid, Spain; Hospital de Elche, Medicina, Elche, Spain; Hospital Calella, Medicina, Calella, Spain; Fundacio IrsiCaixa, HIV, Barcelona, Spain; Mutua de Tarrasa, Medicina, Tarrasa, Spain; Hospital Clinic Universitari, Pharmacology, Barcelona, Spain; Hospital Clinic Universitari, Biostatistics, Barcelona, Spain.

07/31/07

Reference
E Martinez, JA Arranz, D Podzamczer, and others. Efficacy and safety of NRTIs switch to tenofovir plus emtricitabine (Truvada) vs. abacavir plus lamivudine (Kivexa) in patients with virologic suppression receiving a lamivudine containing HAART: the BICOMBO study. 4th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention. Sydney, Australia, July 22-25, 2007. Abstract WESS102.

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