This is an open-label, randomized and multi-center study to compare the efficacy and safety of continued enfuvirtide (Fuzeon) plus (+) OB therapy versus OB alone in participants with HIV-1 infection. Participants will receive an initial 28 week induction treatment with enfuvirtide + OB. After 28 weeks participants with a plasma viral load less than or equal to (\

Inclusion Criteria:

• Participants with HIV-1 infection
• Female participants without any risk of pregnancy
• Participants previously treated with drugs of 2 or 3 different antiretroviral classes
• Participants currently on highly active antiretroviral treatment (HAART) for more than 4 weeks and with a plasma viral load between 1,000 and 300,000 copies of HIV-1 ribonucleic acid per milliliter (RNA/mL)
• Participants with the possibility of potentially effective OB without enfuvirtide, consisting to 2 to 5 drugs, at least two of which are active from at least two different antiretroviral classes
• Cluster of differentiation 4 (CD4) cell count greater than (>) 50 cells/cubic millimeter (mm^3) at screening
• Participants in whom resistance mutations have been detected in reverse transcriptase and/or protease genes
• Enfuvirtide-naive participants

Exclusion Criteria:

• Women of childbearing age not using effective mechanical contraception
• Pregnant or breastfeeding women
• Presence of HIV-2 coinfection
• Participants participating or having participated to another clinical trial during the 30 days prior to selection for this trial
• Participants having previously been treated with enfuvirtide
• Presence active opportunistic infection within 1 month of study entry
• Existence of Grade 4 clinical or laboratory abnormalities
• Cirrhosis or severe hepatic failure
• Uncontrolled diabetes or requiring insulin
• Consumption of alcohol and/or narcotics and/or other substances