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.