Treatment Substitution With PRO 140 Monotherapy in Adult Subjects With HIV-1 Infection

This study is a Phase 2b, multi-center study designed to evaluate the efficacy, safety, and tolerability of PRO 140 monotherapy for the maintenance of viral suppression in patients who are stable on combination antiretroviral therapy. Patient enrollment will be staggered in this study to facilitate adequate safety monitoring. A lead cohort will include 12 subjects. Enrollment of additional 28 subjects will not be initiated until it is approved by the independent Data Monitoring Committee (DMC). Consenting patients will be shifted from combination antiretroviral regimen to PRO 140 monotherapy for 12 weeks. Total treatment duration with PRO 140 will be up to 14 weeks with the one week overlap of existing retroviral regimen and PRO 140 at the beginning of the study treatment and also one week overlap at the end of the treatment in subjects who do not experience Virologic Failure. PRO 140 will be administered as a 350 mg subcutaneous injection weekly for up to 14 weeks. Study participants will be monitored for viral rebound on a weekly basis following initiation of PRO 140 monotherapy and will re-initiate their previous antiretroviral regimen if plasma HIV-1 RNA levels rise above 400 copies/ml on two consecutive blood draws at least 3 days apart. The study will have three phases: Screening Phase, Treatment Phase and Follow-up Phase. The primary objective is to assess efficacy of PRO 140 monotherapy for the maintenance of viral suppression following substitution of antiretroviral therapy in patients who are stable on combination antiretroviral therapy. The secondary objective of the trial is to assess the clinical safety and tolerability parameters following substitution of antiretroviral therapy in patients who are stable on combination antiretroviral therapy.