Relative potencies of two monotherapy regimens (TDF alone vs. ABC alone) compared to the dual NRTI regimen of TDF+ABC as assessed by the short-term virologic response. (Change in HIV RNA copies/mL at baseline and day 7 for monotherapy, baseline and day 49 for dual therapy.)

At day 49 of Sequence 2 a 24-hour post dose plasma sample should be collected and processed. All 7 samples from the sparse PK (time 0, 30-min, 1-hr, 2-hr, 3-hr, 6-hr and 24-hr post dose) should be sent overnight to appropriate off-site lab for analysis. Since the patient is on dual therapy and the each drug is measured in separate labs each PBMC samples should be split at each time-point with half of the samples shipped to Gilead and half shipped to USC (two separate shipments). ALL plasma samples should be sent to USC. Since samples have to be split we will need to collect double the blood for the intracellular (PBMC) PK: Blood volume (PBMC-plasma): 40 mL - each draw Blood volume (plasma only): 3 mL - each draw Blood volume: 169 mL- over 2 days Plasma NRTI and intracellular ddNTP concentrations were measured 7 days after treatment with ABC or TDF alone and were compared to levels obtained after 7 days of treatment with both drugs

At day 49 of Sequence 2 a 24-hour post dose intracellular (PBMC) should be collected and processed. All 7 samples from the sparse PK (time 0, 30-min, 1-hr, 2-hr, 3-hr, 6-hr and 24-hr post dose) should be sent overnight to appropriate off-site lab for analysis. Since the patient is on dual therapy and the each drug is measured in separate labs each PBMC samples should be split at each time-point with half of the samples shipped to Gilead and half shipped to USC (two separate shipments). ALL intracellular (PBMC) samples should be sent to USC. Since samples have to be split we will need to collect double the blood for the intracellular (PBMC) PK: Blood volume (PBMC-plasma): 40 mL - each draw Blood volume (plasma only): 3 mL - each draw Blood volume: 169 mL- over 2 days Intracellular ddNTP concentrations were measured after 7 days on monotherapy and after 7 days on dual therapy