Background.Atazanavir is a once‐daily protease inhibitor (PI) for the treatment of human immunodeficiency virus (HIV) infection that has previously been studied in cohorts of treatment‐naive and treatment‐experienced patients. Limited data are available on the usefulness of switching from a PI‐based regimen to a regimen based on a different PI, such as atazanavir, in HIV‐infected patients experiencing virologic suppression but seeking regimen simplification.

Methods.The Switch to Another Protease Inhibitor (SWAN) study was a 48‐week, open‐label trial involving HIV‐positive patients with virologic suppression who were receiving stable PI‐based regimens (with or without ritonavir). Patients were randomized 2:1 to switch to atazanavir (400 mg per day)—or, if they were receiving tenofovir, to atazanavir‐ritonavir (300/100 mg per day)—or to continue to receive their existing PI. The proportion of patients who experienced virologic rebound (defined as an HIV RNA load 50 copies/mL) was compared through study week 48.

Results.Patients either received an atazanavir‐containing regimen (278 patients) or continued to receive a comparator PI‐containing regimen (141 patients). The proportion of patients who experienced virologic rebound was significantly lower among those who switched to an atazanavir‐containing regimen (19 [7%] of 278) than it was among those who continued to receive a comparator PI regimen (22 [16%] of 141; ). Patients who switched to atazanavir therapy experienced significantly fewer total cholesterol, fasting triglyceride, and non–high density lipoprotein cholesterol elevations than did patients in the comparator PI group ( ); patients receiving atazanavir had comparable rates of adverse event–related discontinuation and serious adverse events.

Conclusions.In patients with virologic suppression who were receiving other PIs, switching to a once‐per‐day regimen containing atazanavir provided better maintenance of virologic suppression (as demonstrated by significantly lower rates of virologic rebound and treatment failure than those observed with continued unmodified therapy), a comparable safety profile, and improved lipid parameters, compared with those for patients who continued their prior PI‐based regimen through 48 weeks.