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

Participants will enroll into one of two study cohorts. Cohort 1 will provide continued administration of IV ibalizumab for patients completing a prior ibalizumab clinical trial (TaiMed-sponsored or Investigator-Sponsored). Patients will continue to receive IV infusions of ibalizumab at the dosage assigned in the previous study - either 800 mg once every two weeks, or 2000 mg once every four weeks. Cohort 2 will provide IV ibalizumab, 800 mg once every two weeks, for qualifying patients with multi-drug resistant HIV-1 and limited treatment options who have never previously received ibalizumab. Participants may continue in this study for 48 weeks, or until ibalizumab becomes commercially available, whichever occurs first.