CD19 and acute lymphoblastic leukemia: BsAbs are a form of immunotherapy for haematological cancers which have an anti-CD3 arm to engage CD3+ T-cells and a target antigen (e.g., anti-CD19, acute lymphoblastic leukaemia [ALL]; anti-CD269, myeloma; anti-CD20, non-Hodgkin’s lymphoma) arm to bind to target cells (27, 138, 139).