Screening Protocol To Determine Eligibility For Studies Of The Chemokine Coreceptor 5 (CCR5) Antagonist GW873140

Inclusion Criteria: * HIV-infected. * Screening viral load at least 5000copies/mL. * Total prior antiretroviral experience of at least 3 months and documented resistance to at least one drug in each of the following classes: nucleoside reverse transcriptase inhibitors (NRTI), non-nucleoside reverse transcriptase inhibitors (NNRTI), and protease inhibitors (PI), stable antiretroviral regimen (or no antiretroviral treatment) for at least 4 weeks before screening. * Able to receive a ritonavir-boosted protease inhibitor during treatment studies. * Women of childbearing potential must use specific forms of contraception. Exclusion criteria: * Acute laboratory abnormalities. * History of pancreatitis or hepatitis, hepatitis B or hepatitis C coinfection, or any chronic liver disease. Screening liver function tests will be used to determine eligibility. * Changes to antiretroviral therapy from 4 weeks prior to screening until Day 1 of treatment or observational studies. * Pregnancy or breastfeeding women. * Recent participation in an experimental drug trial. * Prior use of a CCR5 or CXCR4 antagonist. * Significant ECG abnormalities or significant history of active pancreatitis, hepatitis, opportunistic infections, malabsorption disorders, cancer, or severe illness. * Current use of certain medications may exclude participation in this study. * Additional qualifying criteria and laboratory test requirements to be assessed by study physician.