Switch to Atazanavir and Brachial Artery Reactivity (SABAR) Study

• Percentage Change in Brachial Artery Flow Mediated (FMD) Vasodilation Between Arms From Baseline to Week 24 [ Time Frame: Baseline to week 24 ] [ Designated as safety issue: No ]
  Brachial artery reactivity assessed by noninvasively measuring brachial artery diameter and flow velocities in response to overinflated blood pressure cuff (Flow mediated dilation (FMD))in subjects switching to atazanavir and in subjects continuing on a stable antiretroviral regimen
  
  

• Change in Total Cholesterol Levels From Baseline to Week 24 [ Time Frame: Baseline to 24 weeks ] [ Designated as safety issue: No ]
  Total cholesterol level changes within and between arms
  
  
• Changes in LDL Particle Number From Baseline to Week 24 [ Time Frame: Baseline to 24 weeks ] [ Designated as safety issue: No ]
  Change in LDL particle number
  
  

HIV-infected subjects on a stable protease inhibitor (PI) containing antiretroviral regimen with plasma HIV RNA <500 copies/mL, who have LDL cholesterol levels >130 mg/dL or fasting triglycerides levels >200 mg/dL, will be randomized (1:1) to continue their current antiretroviral regimen or to switch the PI to atazanavir (ATV). Brachial artery reactivity will be measured before (at entry) and 12 and 24 weeks after subjects are randomized.

ARM A: Switch current PI to atazanavir 400 mg once daily plus current > 2 nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) for 24 weeks.

Subjects currently on ritonavir (RTV) (400 mg BID or greater) or RTV-boosted PI (<400 mg/day) , or tenofovir (TDF) as backbone NRTI therapy, will switch to ATV 300 mg boosted with RTV 100mg once daily.

ARM B: Continue current antiretroviral regimen (single or RTV-boosted PI plus > 2 NRTIs) for 24 weeks

Brachial artery reactivity in response to two vasoactive stimuli (increased forearm blood flow and nitroglycerin) will be assessed by measuring brachial artery diameter.