Data presented at the 2nd International AIDS Society Conference on HIV Pathogenesis and Treatment, held in Paris in July, demonstrated that a treatment regimen combining the new drug Reyataz (Bristol-Myers Squibb Co.), boosted with low-dose ritonavir, provided antiviral effect comparable to a standard-of-care protease inhibitor regimen containing the ritonavir-boosted PI lopinavir (Kaletra, Abbott Laboratories) in highly treatment-experienced HIV patients after 24 weeks of treatment. Reyataz is the first once-daily PI approved by FDA.

"More and more physicians are prescribing multiple protease inhibitor-containing regimens in treatment-experienced patients and this early evidence that Reyataz, when boosted with ritonavir, is comparable to Kaletra is very encouraging," said Bonaventura Clotet, PhD, director of the Retrovirology Laboratory and HIV Unit at Hospital Universitari Germans Trias I Pujol and associate professor of medicine at Universitat Autonoma de Barcelona, Spain.

The 24-week interim analysis of the 48-week study examined 358 randomized patients who had failed two or more HAART regimens, including at least one agent from each class of oral HAART. The primary objective of the three-pronged study was to compare the degree of plasma HIV RNA reduction from baseline of a regimen containing once-daily Reyataz 300 mg boosted with 100 mg of ritonavir to a regimen containing twice-daily Kaletra and a regimen containing once-daily Reyataz 400 mg with 1200 mg of saquinavir, all in combination with once-daily tenofovir (an NtRTI) 300 mg and one NRTI.

The study's secondary objectives included examining the effect of each regimen on the proportion of patients with HIV RNA levels below 400 copies/mL and 50 copies/mL, CD4 cell count changes from baseline, serum lipid changes from baseline, and safety and tolerability.

Results through week 24 showed the ritonavir-boosted Reyataz regimen had comparable antiviral activity to the regimen containing Kaletra. The dual-PI combination of Reyataz and saquinavir showed less antiviral activity than the other two regimens at the interim analysis.

Both boosted regimens resulted in similar decreases from baseline in HIV RNA, with mean changes of -1.86 log10 copies/mL for the ritonavir-boosted Reyataz regimen and -1.89 log10 copies/mL for the Kaletra regimen. The Reyataz/saquinavir treatment produced less of a decrease, with a mean change of -1.52 log10 copies/mL. The proportion of patients with HIV RNA levels below 400 copies/mL and 50 copies/mL using an intent-to-treat analysis were similar for Reyataz/ritonavir and Kaletra but lower with Reyataz/saquinavir. Mean increases from baseline CD4 cell counts at interim analysis were similar between the Reyataz and Kaletra regimens but lower for Reyataz/saquinavir.

Data suggest regimens containing Reyataz, compared to the Kaletra regimen, show more favorable lipid changes as assessed by mean percent changes from baseline in total cholesterol, fasting LDL cholesterol, and fasting serum triglyceride concentrations. The mean percent change from baseline in HDL cholesterol decreased slightly in the Reyataz regimens and did not change in the Kaletra regimen.

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