A study published last week in AIDS Patient Care and STDs found that Trizivir (zidovudine/lamivudine/abacavir) may help people with HIV simplify their long-term maintenance antiretroviral therapy (ART) routine, decreasing harmful side effects and making the drug regimen easier to follow.

However, the study authors caution that their results, which include only 48 weeks of trial data, are still preliminary. Longer follow-up periods will be necessary to ensure the regimen will be safe and effective long-term.

Currently, the standard treatment regimen for HIV includes at least three antiretroviral medications from two different drug classes, usually two nucleoside reverse transcriptase inhibitors (NRTIs), plus either a non-nucleoside reverse transcriptase inhibitor or a protease inhibitor (PI).

This combination therapy is generally successful in decreasing HIV replication, increasing healthy CD4 cell counts, and partially restoring the immune system.

However, there have been a number of short- and long-term harmful side effects reported in response to the current combination ART, especially with protease inhibitor-based therapy.

Some of the side effects include hyperlipidemia (elevation of lipids, such as cholesterol, in the blood), insulin resistance, lipodystrophy (abnormal fat redistribution), and an increased risk of heart problems.

As a result, researchers have explored simplified ART maintenance regimens that do not contain protease inhibitors as an alternative long-term drug option.

In this study, participants who had never received antiretroviral therapy were treated first with a standard dual NRTI/PI regimen, consisting of Combivir (zidovudine/lamivudine) plus Kaletra (lopinavir/ritonavir).

After achieving viral suppression (viral load, or amount of HIV virus in the blood, of less than 50 copies/milliliter), participants were randomly assigned to either continue the Combivir/Kaletra regimen, or switch to Trizivir.

Trizivir is a triple-NRTI regimen, and does not contain a protease inhibitor. Previous studies have shown Trizivir is associated with more favorable lipids and fewer drug interactions compared to regimens containing protease inhibitors.

The study showed that Trizivir was as good as Combivir/Kaletra at maintaining viral suppression halfway through the study, at 48 weeks. The trial will continue for an additional 48 weeks.

Additionally, researchers noted that the NRTI-only regimen, Trizivir, decreased participants’ pill burden from six or eight pills per day to two per day, which could improve adherence.

Adherence – taking medications as prescribed – is important to reduce HIV drug resistance and maintain virus suppression.

The researchers did note some limitations to the study, including a small sample size; only about 100 participants were analyzed. This was partly because the researchers were strict about allowing participants to continue, which could bias the study results toward a favorable outcome.

The study was also open-label, which means participants knew which medications they were taking.

Finally, the results only cover a fairly short duration, which means that it may be too early to predict the success of the treatment long-term.

Safety and effectiveness of the drug regimen will be studied after the full 96 weeks of the study are completed, which is expected to give more information on its long-term potential.

For more information, please see the study in AIDS Patient Care And STDs.