Switching from a ritonavir-boosted protease inhibitor (PI/r) to atazanavir/ritonavir (ATV/r) did not improve abdominal fat in a 96-week randomized trial. But people who switched to atazanavir/ritonavir lost less limb fat and had a sharp reduction in lipids compared with the PI/r group.

Atazanavir has gained popularity as a first- and second-line PI because of its generally mild effect on lipids associated with cardiovascular risk. Its effect on body fat abnormalities compared with other ritonavir-boosted PIs is less well understood.

This multicenter, open-label trial randomized 201 patients with a viral load below 50 copies/mL while taking another PI/r to maintain that PI/r or to switch to atazanavir/ritonavir. Nucleoside reverse transcriptase inhibitors were unchanged during the trial. Researchers measured body fat changes with DEXA scans and abdominal CT scans.

While 131 people switched to atazanavir/ritonavir, 70 continued their current PI/r. Similar proportions switching to atazanavir/ritonavir (93%) and maintaining their current PI (89%) kept their viral load below 50 copies/mL through 96 weeks.

Average changes in trunk-to-limb fat ratio were similar in the two treatment arms, but more people who maintained their original PI/r had a 20% or greater decrease in limb fat through 96 weeks. Compared with people who maintained their initial PI/r, those who switched to atazanavir/ritonavir had significantly greater reductions in lipids associated with atherogenesis.

Both regimens were well tolerated. The incidence of grade 3 or 4 clinical adverse events was higher among people who switched to atazanavir/ritonavir (34%) than among those who stayed with their initial PI/r (4%). That finding is not surprising since study participants had already demonstrated tolerance of their PI/r by the time they entered the trial.

By Mark Mascolini

Source: Graeme J Moyle, Jaime Andrade-Villanueva, Pierre-Marie Girard, Andrea Antinori, Patricia Salvato, Johannes R Bogner, Phillip Hay, Jesús Santos, Ludovic Astier, Miranda Pans, Agnes Balogh, Sophie Biguenet, the ReAL Study Team. A randomized comparative 96-week trial of boosted atazanavir versus continued boosted protease inhibitor in HIV-1 patients with abdominal adiposity. Antiviral Therapy. 2012; 17: 689-700.

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