Two Part Study to Evaluate Pharmacokinetics, Safety, and Antiviral Activity of Elvitegravir Administered With a PI/r Background Regimen for ARV Treatment-Experienced Pediatric Participants

The primary objectives of this study are to evaluate the safety, tolerability and steady-state PK and confirm the dose of EVG/r in HIV-1 infected, antiretroviral treatment-experienced children 4 weeks to \ 1,000 copies/mL only for participants in Cohort 2, Part A) to evaluate the steady state PK and confirm the dose of EVG. Part B will enroll participants who are failing a current ARV regimen (HIV-1 RNA \> 1,000 copies/mL) to evaluate the safety, tolerability, and antiviral activity of EVG. The study consists of 4 age cohorts with each cohort including 2 parts (Part A and Part B) with the exception of the adolescent age cohort (Cohort 1: 12 to \< 18 years old) containing Part B only.