Further progress in the engineering of monoclonal antibodies lead to the development of BITE® or bispecific T cell engager; the first BITE® to reach the market was blinatunomab that targets CD19 and is indicated for the treatment of relapsed/refractory (r/r) adult acute lymphoblastic leukemia (ALL) since 2015. Here, CD19 is linked to acute lymphoblastic leukemia.