Coverage of CROI 2008 (Conference on Retroviruses and Opportunistic Infections)

February 4–6, 2008, Boston, MA

CASTLE study compares Reyataz to Kaletra

February 4, 2008

Results from a large head-to-head study of the Norvir (ritonavir)-boosted protease inhibitors—Reyataz (atazanavir) vs. Kaletra (lopinavir)—were presented today at CROI. For people taking HIV drugs for the first time, the CASTLE study found that Reyataz once a day was comparable to Kaletra twice a day, when each is taken with the fixed-dose combination pill Truvada (Viread/tenofovir + Emtriva/emtricitibine).
                 
CASTLE enrolled almost 900 people who randomly assigned to take took either 300mg Reyataz + 100mg Norvir once a day or 400mg Kaletra + 100mg Norvir twice a day. Both groups took one tablet of Truvada (300mg Viread/tenofovir + 200mg Emtriva/emtricitibine) once a day. Researchers compared these regimens in terms of lower HIV levels, higher CD4 counts, and various measures of fat metabolism.

After 48 weeks, similar numbers of people in both groups had HIV levels below 50 copies (78% for Reyataz vs. 76% for Kaletra). People taking Kaletra had slightly higher increases in CD4 counts (219 vs. 203), though it’s not clinically significant. The most significant difference between the regimens was in side effects. More people on Reyataz had higher levels of bilirubin (a protein produced by the liver) and jaundice. People on Kaletra had higher average levels of cholesterol and triglycerides.

This study confirms the growing body of evidence that most, though not all, boosted protease inhibitor regimens perform about the same in lowering HIV levels and raising CD4 counts. The most important differences are found in side effects, drug interactions and convenience. While Kaletra enjoyed a period alone at the top of the pile, the field is now quite crowded, which is a good thing for people with HIV who now have more choices for boosted protease inhibitor regimens than ever before.