Mosunetuzumab (BCT-4465A) is a humanized antibody based on immunoglobulin G1 that targets CD20 (B cells) and CD3 (T cells). Mosunetuzumab redirects T cells to engage and eliminate malignant B cells and can be used to study relapsed or refractory (R/R) B-cell non-Hodgkin lymphoma (B-NHL) and refractory follicular lymphoma.