Switch From Norvir-Boosted to Unboosted Reyataz Safe and Effective

July 27, 2009

By David Evans

People whose virus is well controlled by a regimen containing Norvir (ritonavir)–boosted Reyataz (atazanavir) and Epzicom (abacavir plus lamivudine) may be able to drop the Norvir—while increasing the Reyataz dose from 300 mg to 400 mg—without losing control of HIV, according to a study presented at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town.

Several Norvir-boosted protease inhibitors, including Reyataz, are recommended by the U.S. Department and Health and Human Services’ (DHHS) HIV treatment guidelines as preferred protease inhibitors to be included as part of a complete regimen. Though Reyataz was also approved as a once-daily unboosted regimen, it is not recommended as a preferred protease inhibitor when used this way. Researchers have found that boosted-protease inhibitors are superior to unboosted protease inhibitors in reducing virus to under 50 copies and keeping it there.

To determine whether it was safe and effective to switch to unboosted Reyataz after virus was well controlled, Kathleen Squires, MD, from the Thomas Jefferson University in Philadelphia, and her colleagues randomized 515 HIV-positive patients to initiate Norvir-boosted Reyataz (100 mg/300 mg) combined with Epzicom. After 36 weeks of that treatment, 419 of them were randomized to either stay on the boosted regimen of Norvir/Reyataz/Epzicom or switch to 400 mg of unboosted Reyataz with Epzicom. Roughly half of the patients in each arm started the study with a viral load over 100,000 copies or a CD4 count under 200.

Squires and her colleagues found that those who switched to the unboosted regimen over an additional 48 weeks of treatment did as well as those who stayed on a boosted-regimen. In fact, though the difference could have occurred by chance, people on the unboosted regimen did slightly better than those on the boosted regimen—86 percent had less than 50 copies of HIV in the unboosted arm, compared with 81 percent in the boosted arm. The two arms were also equivalent in terms of sustained viral load reductions even in people who started treatment with viral loads over 100,000.

In terms of safety, people who switched to the unboosted regimen had reductions in total cholesterol, LDL cholesterol (the “bad” one) and especially triglycerides.

The authors conclude that switching to an unboosted Reyataz regimen may have similar efficacy and result in a better cholesterol and triglyceride profile than Norvir-boosted Reyataz. It is important to note, however, that this finding doesn't apply to combinations involving Reyataz and Truvada (tenofovir and emtricitabline). Because tenofovir (also found in Viread and Atripla) can significantly reduce blood levels of Reyataz, drug combinations containing both Viread and tenofovir must be used—and continued—with Norvir boosting.

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