Adding a fourth drug to an antiretroviral regimen for the initial treatment of HIV-1 did not offer any advantages in terms of reducing HIV levels in the blood, extending the time before viral levels started to climb, or delaying the onset of drug resistance, according to a three-year study.

While triple therapy is currently the standard of care for initial treatment of HIV, the researchers, led by Roy Gulick of Cornell University in New York, USA, wanted to see if there would be a benefit from adding in a fourth drug.

It has been suggested that additional drugs could improve outcomes, but this has had to be weighed against the increased complexity of treatment, the potential for toxicity, and higher costs.

Gulick et al’s study included 765 HIV-1–infected patients who had not previously received treatment for the infection, who were randomised to receive either nucleoside reverse transcriptase inhibitors zidovudine and lamivudine plus Bristol Myers Squibb’s non-nucleoside RTI Sustiva (efavirenz) or the same regimen with the addition of GlaxoSmithKline’s nucleoside RTI Ziagen (abacavir).

Overall, 26% of 382 patients receiving the three-drug regimen and 25% of 383 on the four-drug regimen reached protocol-defined virologic failure and the time to first virologic failure was not significantly different between the two study treatment groups.

80% of patients had HIV-1 RNA levels less than 50 copies/mL, the limits of detection, over the three-year trial. There were no significant differences between the groups in initial virologic response, time to virologic failure, CD4 cell counts, adverse events, adherence to therapy, resistance mutations at virologic failure, or treatment or study discontinuation rates," the authors write.

"The results support current guidelines recommending two nucleosides plus efavirenz for initial treatment of HIV-1 infection; adding abacavir as a fourth drug provided no additional benefit," they conclude.

The findings were presented at the International AIDS Conference in Toronto and published in the Journal of the American Medical Association (August 16).