The purpose of this study is to determine the effectiveness, safety, and tolerability (how well the body stands the drug) of an investigational protease inhibitor (PI) called TMC114 given with low dose ritonavir.

A phase II randomized, controlled, partially blinded, trial to investigate dose response of TMC114/RTV in HIV-1 infected patients who have previously received all three licensed classes of HIV antiviral drugs (known as nucleoside reverse transcriptase inhibitors (NRTI), nonnucleoside reverse transcriptase inhibitors (NNRTI) and protease inhibitors (PI)), and who are on a stable PI-containing regimen not including an NNRTI may be eligible to participate. Four doses of TMC-114/ritonavir will be studied. 300 patients in the United States and Puerto Rico will participate. The duration of the study is 96 weeks. Randomize to one of 4 treatment groups (TMC114/RTV: 400/100 mg qd; 800/100mg qd; 400/100mg bid; 600/100 bid) or control arm for 24 to 48 wks. Optimal dose (TMC114/RTV 600/100mg bid) open label portion of the study. The trial was extended to include 144Wks of treatment.

Inclusion Criteria:

• Male or female, age 18 years or older
• Documented HIV-1 infection
• Stable PI regimen for at least 8 weeks prior to screening
• Plasma viral load at screening above 1000 HIV-1 RNA copies/ml
• Prior use of more than 1 NRTI for at least 3 months
• Prior use of one or more NNRTIs as part of a failing regimen
• At least 1 primary PI mutation as defined by the IAS guidelines
• Treatment with at least 1 PI for a total of at least 3 months
• Patient has given informed consent

Exclusion Criteria:

• Presence of any currently active AIDS defining illness except stable cutaneous Kaposi's Sarcoma and Wasting syndrome due to HIV infection
• Current or past history of alcohol and/or drug abuse which, in the investigator's opinion, would compromise the subject's safety or compliance to the study protocol procedures
• NNRTI as part of therapy at screening
• Patients on a treatment interruption at screening
• Patients for whom an investigational antiretroviral therapy is part of the regimen at screening or the use of any non-antiretroviral investigational agents 90 days prior to screening
• Hepatitis A, B, or C.