Bristol-Myers Squibb’s protease inhibitor Reyataz (atazanavir) boosted with low-dose Norvir (ritonavir) has been approved as a first-line protease inhibitor option in the European Union, according to AIDSmap. The European Commission delayed its approval because it was waiting on results from a large clinical trial comparing Norvir-boosted Reyataz with Kaletra (lopinavir/ritonavir) in HIV-positive individuals beginning treatment for the first time.

The European Union approval is based on the CASTLE study, which showed that Norvir-boosted Reyataz was comparable to Abbott Laboratories’ Kaletra (lopinavir/ritonavir). The study revealed that 78 percent who started treatment with once-daily Reyataz had a viral load below 50 copies/ml at week 48, compared with 76 percent who started treatment with twice-daily Kaletra.

Reyataz is already approved in Europe for use after the failure of first-line treatment involving other antiretrovirals, and it has been approved for first-time HIV  treatment takers in the United States since May 2003.