Pilot Study of Adding Raltegravir (MK-0518) to Antiretroviral Therapy in Patients With Low Level Viremia

This is a non-randomized, non-comparative, single center trial of antiretroviral therapy intensification using the investigational integrase inhibitor MK-0518 and an investigational viral load assay to measure response to additional antiviral therapy. Eighteen patients will receive open-label MK-0518 400 mg P.O. every 12 hours for 28 days in addition to their prescribed antiretroviral therapy. Patients will take their doses of MK-0518 without regard to food. The study will enroll patients on antiretroviral therapy regimens with Cluster of Differentiation 4 (CD4) counts greater than 200 cells/ul, HIV-1 RNA levels \<50 copies RNA/ml plasma using a commercial assay(conventional Amplicor) and with detectable plasma virus (viral loads ≥ 1 copies RNA/ml plasma, Single copy assay, "SCA"). Acceptable antiretroviral regimens will include those on Nucleoside reverse transcriptase inhibitors ("NRTIs") + protease inhibitor (PI)I, NRTIs + non-nucleoside reverse transcriptase inhibitors (NNRTIs), + PI, or NRTIs + NNRTI-containing regimens. Patients cannot have prior evidence of resistance to antiretroviral drugs. Patients will be screened for intensification by history, physical exam, and laboratory evaluations (see below). Patients who are eligible and who agree to participate will intensify their antiretroviral therapy for 28 days with MK-0518 400 mg by mouth twice a day. During the 28- day drug addition, patients will have samples drawn for SCA assay at entry and on days 7, 14, 21, and 28 (+/- 1 d), with the last day of intensification as day 28. Patients will have additional phlebotomy after intensification on days 29, 30, 35, 42, 49 and 58 (+/- 1 day). The intensification period is followed by a post- intensification period to determine whether removal of the drug resulted in viral RNA changes.