Ibalizumab Plus Optimized Background Regimen in Treatment-Experienced Patients With Multi-Drug Resistant HIV-1

Inclusion Criteria: (Cohort 1) * Currently receiving ibalizumab via other TaiMed-sponsored or investigator-Sponsored protocol * Are capable of understanding and have voluntarily signed the informed consent document (Cohort 2) * 18 years of age or older * Are capable of understanding and have voluntarily signed the informed consent document * Have documented HIV-1 infection by official, signed, written history (e.g., laboratory report), otherwise an HIV-antibody test will be performed * Are able and willing to comply with all protocol requirements and procedures * Have a viral load \>1,000 copies/mL and documented resistance to at least one antiretroviral medication from each of three classes of antiretroviral medications as measured by previous viral resistance testing (resistance testing is not provided by the study for qualification purposes) * Have a history of at least 6 months on antiretroviral treatment * Are receiving a failing antiretroviral regimen OR have failed and are off therapy * Have viral sensitivity/susceptibility to at least one antiretroviral agent, other than ibalizumab, as determined by previous resistance test performed within 6 months of screening and be willing and able to be treated with at least one agent to which the patient's viral isolate is fully sensitive/susceptible according to the resistance tests used for screening as a component of OBR * If sexually active, are willing to use an effective method of contraception during the study and for 30 days after the last administration of the study drug Exclusion Criteria: (Cohort 1) * There are no Exclusion Criteria for patients meeting the Inclusion Criteria for Cohort 1 (Cohort 2) * Eligible for participation in other TaiMed-sponsored clinical trials of ibalizumab * 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 patient from participating in this study * Any significant acute illness within 1 week before the first administration of investigational medication on this study * Any active infection secondary to HIV requiring acute therapy; however, patients that require maintenance therapy (i.e., secondary prophylaxis for opportunistic infections) will be eligible for the study. * Any immunomodulating therapy (including interferon), systemic steroids, or systemic chemotherapy within 4 weeks before Day 0 * Any prior exposure to ibalizumab (formerly TNX-355 and Hu5A8) * Any vaccination within 7 days before Day 0 * Any female patient who either is pregnant, intends to become pregnant, or is currently breastfeeding * Any current alcohol or illicit drug use that, in the investigator's opinion, will interfere with the patient's ability to comply with the study schedule and protocol evaluations * Any previous clinically significant allergy or hypersensitivity to any excipient in the ibalizumab formulation * Any radiation therapy during the 28 days before first administration of investigational medication on this study * Any clinically significant Grade 3 or 4 laboratory abnormality according to the Division of AIDS (DAIDS) grading scale, except for the following asymptomatic Grade 3 events: * triglyceride elevation * total cholesterol elevation