Inclusion Criteria:

• Males and females who are between 18 years (or the legal age of consent, whichever is older) and 65 years of age. Females may be enrolled following a negative pregnancy test if:

  a) they are documented to be surgically sterile or post-menopausal [amenorrhea >1 year and FSH >30mU/mL]; --OR-- b) they are using a hormonal birth control method (oral contraceptives, contraceptive implants); --OR-- c) they are using a barrier method of contraception (male or female condoms, diaphragm, cervical cap) with a spermicide.

• Subjects with a positive history of HIV-infection, documented by a licensed HIV antibody ELISA assay and confirmed either by Western blot, positive HIV blood culture, positive HIV serum antigen or plasma viremia.
• Subjects currently on an accepted, stable HAART regimen that includes lamivudine for at least 60 days prior to screening.
• Subjects who, in the opinion of the investigator, are failing their current HAART regimen.
• Subjects who have an HIV-RNA copy number of ≥ 2000 copies/mL as determined by FDA-approved, Roche PCR assay (Amplicor HIV-1 Monitor® Test, v1.5 – Quantitative).
• Subjects who have a CD4-lymphocyte count ≥ 50 cells/mm3.
• Subjects who have the M184V HIV mutation, as determined by the FDA-approved Bayer assay, TRUGENE® HIV-1 Genotyping Kit and the OpenGene® DNA Sequencing System.
• Subjects who are able and willing to provide written, informed consent.
• Subjects who are able and willing to comply with the requirements of this study.

Exclusion Criteria:

• Subjects who have a current or recent (< 30 days) opportunistic infection characteristic of AIDS (Category C according to the CDC Classification System for HIV-1 Infection, 1993 Revised Version).
• Subjects currently on a (-)-FTC regimen.
• Subjects with Q151M mutation.
• Subjects with T69S insertions.
• Female subjects who are pregnant or breastfeeding.
• Subjects enrolled in other investigational drug protocols or subjects who have received other investigational agents within 30 days prior to the first dose of study medication. For investigational drugs with an elimination half-life greater than 15 days, this will be extended to 60 days.
• Subjects with malabsorption syndromes possibly affecting drug absorption (e.g. Crohn’s disease, chronic pancreatitis, etc).
• Subjects with acute hepatitis B and/or C, except for subjects who, at the discretion of the investigator, have a chronic, but stable hepatitis infection.
• Subjects with the following laboratory parameters within 30 days prior to the first dose of study medication: *Hemoglobin <10.0 g/dL; *Absolute neutrophil count (ANC) <1000/mm3; *Platelet count <100,000/mm3; *AST or ALT >5 times the upper limit of normal, without the presence of an underlying illness, other than HIV or acute hepatitis, judged by the investigator to likely cause such chronic enzyme abnormalities; *Pancreatic amylase >1.5 times the upper limit of normal.
• Subjects who have received an HIV vaccination within 6 months prior to the first dose of study medication.
• Subjects who have received radiation therapy or cytotoxic chemotherapeutic agents within 30 days prior to the first dose of study medication.
• Subjects who, in the opinion of the investigator, are unable to comply with the dosing schedule and protocol evaluations.