Atazanavir-Based Regimen Has Greater Risk of Treatment Failure Compared to Efavirenz-Based Combination: Presented at AIDS 2008

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Title: Atazanavir-Based Regimen Has Greater Risk of Treatment Failure Compared to Efavirenz-Based Combination: Presented at AIDS 2008
URL: http://www.pslgroup.com/dg/2278D2.htm
Doctor's Guide
August 8, 2008

By Ed Susman

MEXICO CITY -- August 8, 2008 -- A clinical trial has again demonstrated that the standard-of-care treatment for patients with human immunodeficiency virus (HIV) -- efavirenz, zidovudine, and lamivudine -- is a superior regimen, according to trial results presented here at the 17th International AIDS Conference (AIDS 2008).

The efavirenz-based treatment was shown to be "conclusively" better than a more complicated regimen of didanosine, emtricitabine, and atazanavir (all taken once daily), in a multinational trial supported by funds from the National Institutes of Health, Bethesda, Maryland. The trial enrolled 1,045 participants (547 men and 498 women) from 8 developing countries and the United States.

In a late-breaker oral presentation here on August 7, Thomas Campbell, MD, University of Colorado at Denver, Denver, Colorado, described why the atazanavir-based regimen was inferior to the efavirenz combination.

"The atazanavir regimen had significantly greater risk of treatment failure compared to the efavirenz therapy," Dr. Campbell said delivering the results of the PEARLS trial (Phase IV, Prospective, Randomized, Open-Label Evaluation of the Efficacy of Once-Daily Protease Inhibitor and Once-Daily Non-Nucleoside Reverse Transcriptase Inhibitor-Containing Therapy Combinations for Initial Treatment of HIV-1 Infected Individuals From Resource-Limited Settings).

Results from the third arm in the study -- containing efavirenz, emtricitabine, and tenofovir all taken once a day -- appeared so similar to those of the other efavirenz regimen that the organisers decided to use the zidovudine/lamivudine/efavirenz combination as the study control arm.

The inferiority conclusion for the atazanavir regimen was made following a review of the data by the study's data safety monitoring board. There were not enough data to determine anything about the comparison between the efavirenz regimens, so that part of the study remains blinded, Dr. Campbell explained. He added that the atazanavir patients are being switched to other regimens.

The primary endpoint of the study was treatment failure, defined as virological failure: either a viral load of greater than 1,000 copies/mL after 16 weeks of therapy; or a new AIDS-defining condition at least 12 weeks after starting therapy; or death from any cause.

When the data committee decided to unblind part of the study, those in the atazanavir arm had a significant 67% increase in the risk of treatment failure, compared with those in the control arm.

There was no significant difference between the arms in either AIDS progression or death, but those subjects taking atazanavir experienced a significant 77% increase in the risk of virological failure.

Dr. Campbell noted that 48-week and 96-week success rates of the atazanavir regimen were 84% and 76%, respectively.

[Presentation title: PEARLS (ACTG A5175): A Multinational Study of Didanosine-EC, Emtricitabine and Atazanavir vs Co-formulated Zidovudine/Lamivudine and Efavirenz for Initial Treatment of HIV-1 Infection. Abstract THAB0404]

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