Randomized, Double-Blind Study Comparing Dexelvucitabine (DFC) to Lamivudine (3TC) in Subjects With Resistance to NRTIs, PIs, and NNRTIs

The study will compare the safety and efficacy of an investigation nucleoside analog reverse transcriptase inhibitor (NRTI), dexelvucitabine (DFC), to an approved NRTI, lamivudine (3TC) in HIV treatment-experienced patients who are resistant to 3 classes of antiretroviral therapies (NRTIs, PIs and NNRTIs). Patients meeting eligibility requirements will have a new \'optimized\' background regimen (OBR) selected for them by their investigator based on prior ARV treatment history and the results of HIV genotype and phenotype tests performed during the screening period. In addition to treatment with the new OBR, patients will be randomized to receive treatment with either DFC or 3TC in a blinded fashion. There is a 50 percent chance a patient will receive DFC or 3TC. Treatment in the study may continue for up to 96 weeks. Patients with an inadequate response to therapy after 16 weeks will have the option to change their OBR and the option to switch to receive the other study medication (i.e., DFC to 3TC or 3TC to DFC).