This study will evaluate the steady-state pharmacokinetics (PK) and confirm the dose of cobicistat-boosted atazanavir (ATV/co) or cobicistat-boosted darunavir (DRV/co) in HIV-1 infected antiretroviral treatment-experienced pediatric participants between the ages of 3 months to < 18 years of age.
It will also evaluate the safety, tolerability, and efficacy of ATV/co or DRV/co each co-administered with a background regimen (BR) through 48 weeks and during long-term treatment (total of 5 years).