The antiretroviral potency of DAPD varies among antiretroviral-experienced patients. In vitro studies indicate that the potency of DAPD can be markedly increased by the addition of MMF. Preliminary data indicate that MMF is well tolerated in patients with advanced HIV-1 disease. However, there is currently no clinical data on the activity of DAPD combined with MMF. This study will be the first to evaluate the addition of DAPD and MMF to a patient's current antiretroviral therapy.

At study entry, patients will be randomly assigned to one of two blinded treatment arms. Arm A receives DAPD plus MMF placebo in addition to their current regimen, while Arm B receives DAPD plus MMF in addition to their current regimen. All patients remain on their current antiretroviral regimen through Week 2. After Week 2, patients who virologically respond are encouraged to remain on blinded study treatment through Week 24. Patients who do not virologically respond are unblinded.

After unblinding, patients who were not receiving MMF may add it to their antiretroviral regimen. Response to the addition of open-label MMF is assessed after 2 weeks. Resistance to antiretroviral agents, including DAPD, will be assessed following any virologic failure occurring after Week 2. All patients have the option of optimizing their background antiretroviral regimen at Week 2, based on the results of a pre-entry resistance assay; enfuvirtide will be made available for background therapy optimization through Week 48.

Patients who are still receiving DAPD alone or DAPD plus MMF at Week 48 and who are still responding virologically may choose to continue the study drug(s) and be followed for up to an additional 48 weeks. Throughout the study, HIV-1 RNA levels, CD4 cell counts, and study drug levels will be monitored regularly. Eye exams will be done at several study visits. Only DAPD, MMF, and MMF placebo will be supplied by this study; patients must obtain the rest of their treatment regimen through their doctor. Patients who discontinue treatment before the end of study will need to come in for a follow-up visit 4 weeks after discontinuation and may need to attend future follow-up visits at 8-week intervals, as determined by the investigator.