The European Commission this week granted marketing approval for the protease inhibitor Reyataz (atazanavir) boosted with ritonavir as a once-daily option for first-line therapy in the European Union.
Atazanavir is already approved in Europe for use after the failure of first-line treatment in combination with other antiretrovirals, and has been approved for first-line use in the United States since May 2003.
European approval for first-line treatment was delayed because regulators wanted to see results from a large, randomised study in which atazanavir, boosted with ritonavir, was compared with twice-daily lopinavir/ritonavir (Kaletra).
Forty-eight week results from the Castle study were presented earlier this year at the Fifteenth Conference on Retroviruses and Opportunistic Infections in Boston. This study showed that atazanavir, boosted with ritonavir, was non-inferior to Kaletra (i.e. showed similar potency): 78% of those who started treatment with atazanavir had a viral load below 50 copies/ml at week 48, compared to 76% of those who started treatment with Kaletra.
Reyataz was also better tolerated in some respects, with a trend towards less diarrhoea and fewer cholesterol and triglyceride increases among those who received the drug. However 34% of those who received atazanavir developed hyperbilirubinemia, a harmless elevation of bilirubin levels in the blood that can lead to yellowing of the skin (jaundice). Three out of 438 patients who received atazanavir in the study discontinued the drug because of this side-effect.
The daily dose of atazanavir is now available in a single 300mg capsule in Europe that can be combined with a single 100mg ritonavir capsule.