Safety and Efficacy of Switching From Stavudine or Zidovudine to Tenofovir DF in HIV-1 Infected Children

Major Inclusion Criteria:

- Documented laboratory diagnosis of HIV-1 infection

- Plasma HIV-1 RNA < 400 copies/mL

- Currently on a stable stavudine or zidovudine -containing antiretroviral therapy
regimen for at least 12 weeks

- Naive to tenofovir DF

Key Inclusion Criteria for the First 96-Week Extension

- Completed 48 weeks of treatment in Arm 1 or Arm 2 of the study

- <18 years of age (at the start of the extension)

- Participants initially randomized to Arm 2 will be given the option to replace
stavudine or zidovudine with tenofovir DF in the 96-week extension at the
investigator's discretion, if the investigator determines that tenofovir DF is safe
and beneficial for the participant.

Key Inclusion Criteria for the Second and Third 96-Week Extension and Fourth Open-Ended
Extension

- Completed of treatment with study drug in the first extension phase

- <18 years of age at the start of the extension. This inclusion criterion is not
applicable in those regions where tenofovir DF is not commercially available for
treatment of HIV-1 infection in adults.

Key Exclusion Criteria:

- Participants receiving ongoing therapy with any of the following

- Nephrotoxic agents

- Systemic chemotherapeutic agents

- Systemic corticosteroids

- Interleukin 2 (IL 2) and other immunomodulating agents

- Investigational agents

- Pregnant or lactating participants

- Evidence of a gastrointestinal malabsorption syndrome or chronic nausea or vomiting
which may confer an inability to receive an orally administered medication

- Current alcohol or substance abuse judged by the investigator to potentially interfere
with participant compliance

- Malignancy other than cutaneous Kaposi's sarcoma (KS) or basal cell carcinoma.

- Active, serious infections (other than HIV-1 infection) requiring parenteral
antibiotic therapy within 15 days prior to screening

- Prior history of significant renal disease (ie, nephrotic syndrome, renal dysgenesis,
polycystic kidney disease, congenital nephrosis)

- Prior history of significant bone disease (ie, osteomalacia, chronic osteomyelitis,
osteogenesis imperfecta, osteochondroses, multiple bone fractures)

Note: Other protocol defined Inclusion/ Exclusion criteria may apply.