The virological efficacy of ibalizumab has been clearly demonstrated in multiple clinical trials. This study will expand ibalizumab's clinical data set and allow a better understanding of the virologic response durability on ARV regimens with or without ibalizumab in a heterogeneous real-world patient population. Additional data on the efficacy and safety of ibalizumab and its impact on patient reported outcomes will be captured until study end. Primary Objective: To evaluate the long-term efficacy, safety, and durability of ibalizumab in combination with other ARVs by comparing the virologic, immunologic and clinical outcomes of patients receiving ibalizumab treatment versus patients not receiving ibalizumab. Secondary Objective: To assess the efficacy of ibalizumab in combination with other antiretrovirals by comparing the virologic, immunologic, clinical and patient reported outcomes of patients before and after they receive ibalizumab treatment. To assess the long-term safety and tolerability of ibalizumab. Other Objectives: To assess risk factors/predictors of virologic and immunologic response. To assess efficacy and safety in special populations that enroll.