The purpose of this Phase I study is to determine whether the antibody (UB-421), targeting the HIV-1 receptor on the CD4 molecule (domain 1) of T-lymphocytes and monocytes, is safe and well tolerated when administered to asymptomatic HIV-1 infected adults by intravenous infusion and to assess pharmacokinetic parameters of the antibody in blood and on cells. The neutralizing activity of UB-421 blocks HIV-1 from binding to its receptor on CD4-positive cells; thus, UB-421 functions as an immunotherapeutic intervention to prevent HIV-1 infection.

Inclusion Criteria:

• Asymptomatic, treatment-naive, HIV-1 seropositive
• CD4+ T cell count >350 cells/cubic millimeter
• HIV-1 viral load >5,000 copies/mL
• Other inclusion criteria apply

Exclusion Criteria:

• Active infection requiring immediate therapy (except HIV-1)
• Prior participation in any HIV vaccine trial
• Previous exposure to a monoclonal antibody
• Use of immunomodulating drugs or systemic chemotherapy
• Other exclusion criteria apply