The purpose of this phase II study is to evaluate the safety, tolerability and efficacy of two multi-dose regimens of UB-421 monotherapy in replacement of HAART in HIV-1 infected adults with virological suppression.

This is an open-label, Phase II study to evaluate the safety, tolerability and efficacy of two multi-dose regimens of UB-421 monotherapy in replacement of HAART in HIV-1 infected adults with virological suppression. In this study, approximately 29 subjects will be enrolled to receive one of the two UB-421 regimens as the monotherapy in replacement of HARRT treatment. Subjects assigned to Cohort 1 will receive UB-421 infusion at 10 mg/kg weekly for 8 weeks; subjects assigned to Cohort 2 will receive UB-421 infusion at 25 mg/kg bi-weekly for 16 weeks.

Inclusion Criteria:

• HIV-1 sero-positive
• Aged 20 years or older
• Have received HAART treatment
• CD4+ T cell count ≧ 350 cells/mm3
• HIV-1 plasma RNA level remains below the limit of
• Were not breastfeeding for women
• Subjects with a negative serum pregnancy test result at screening visit for women of childbearing potential
• Subjects agree on using birth control barrier (female or male condom) during the entire study period
• Subjects sign the informed consent before undergoing any study procedures

Exclusion Criteria:

• Any active infection except for HIV, and required immediate therapy
• Any active AIDS-defining illness per Category B and Category C conditions according to the U.S. Centers for Disease Control and Prevention (CDC) Classification System for HIV Infection
• Any documented CD4+ T cell count < 200 cells/mm3 within the past 12 weeks before screening visit
• Any significant diseases (other than HIV-1 infection) or clinically significant findings, including psychiatric and behavioral problems, determined from screening, medical history, and/or physical examination that, in the investigator's opinion, would preclude the subject from participating in this study
• Any vaccination within 8 weeks prior to the first dose of study drug
• Any immunomodulating therapy (including interferon and steroid) or systemic chemotherapy within 12 weeks prior to the first dose of study drug
• Any illicit intravenous drugs within 12 weeks prior to the first dose of study drug
• Any current alcohol or illicit drug use that, in the investigator's opinion, will interfere with the subject's ability to comply with the dosing, visit schedules and protocol evaluations
• More than one change of HAART regimen because of virologic failure