The purpose of this study is research with the goal of evaluating the effect of TMC125 (a non-nucleoside reverse transcriptase inhibitor) on slowing down the growth of the HIV virus. The study will also investigate whether this new medication is well tolerated, and to further confirm that the medication is safe to be used.

This is a Phase III, randomized, double-blind, placebo-controlled trial to evaluate the long-term efficacy, tolerability, and safety of TMC125 as part of an antiretroviral therapy (ART) regimen containing TMC114/ritonavir (RTV) and an investigator-selected optimized background (OBR) in treatment-experienced HIV-1 infected patients. TMC125 is a non-nucleoside reverse transcriptase inhibitor (NNRTI). TMC114 is a protease inhibitor (PI). In this trial, TMC114 will be given with a low dose of ritonavir (RTV), a protease inhibitor commonly used with other, full dose protease inhibitors to improve activity. Additional assessment to be evaluated in this trial include: changes in the HIV-1 genotype, drug susceptibility, and the population pharmacokinetics of TMC125. A pharmacokinetic substudy will be performed at selected sites. Health-related quality of life will be assessed for patients receiving an antiretroviral therapy containing either TMC125 or placebo. Safety and tolerability will be documented throughout the trial. Six hundred HIV-1 infected patients on a stable but virologically failing regimen will be included in the trial. Patients should have at least 1 documented non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance-associated mutation (either at screening or from historical genotype reports), an HIV-1 plasma viral load > 5000 RNA copies/mL at screening, and at least 3 documented primary protease inhibitor (PI) mutations. Patients will be randomized in a 1:1 ratio to either TMC125 (200 mg twice daily) or to matching placebo; both in combination with TMC114/RTV (600/100 mg twice daily) and an investigator selected OBR of at least 2 antiretrovirals (ARVs), consisting of nucleoside reverse transcriptase inhibitor(s) (NRTI[s]) with or without enfuvirtide. The trial will involve a screening period of up to 6 weeks, a 48-week treatment period, and a 4-week follow-up period. Patients will take 200 mg oral doses of TMC125 tablets or placebo tablets; twice daily (administered as 2 tablets twice daily, with food) in combination with 600 mg oral doses of TMC114 tablets and 100 mg oral doses of ritonavir (administered as 2 tablets of TMC114 and 1 capsule of ritonavir twice daily, with food). The treatment period is 48 weeks.

Inclusion Criteria:

• Patient has 3 or more primary protease inhibitor mutations
• documented genotypic evidence of resistance to currently available NNRTIs by having at least 1 NNRTI (non-nucleoside reverse transcriptase inhibitors) resistance-associated mutation
• on a stable antiretroviral therapy for at least 8 weeks
• plasma viral load at screening visit > 5000 HIV-1 RNA copies/mL.

Exclusion Criteria:

• Active AIDS defining illnesses (except for stable, cutaneous Kaposi's Sarcoma or wasting syndrome)
• Any grade 3 or grade 4 toxicity according to the DAIDS grading scale
• Use of disallowed concurrent therapy
• Any active clinically significant disease