In this regard, the anti-CD3/CD19 bispecific T cell engager, blinatumomab, a fusion protein of two single-chain Fv antibody fragments, received FDA approval in 2014 for the treatment of a rare form of ALL [12,13], and resulted in complete responses in 26 of 36 (72%) ALL patients [14]. This evidence concerns the gene CD19 and acute lymphoblastic leukemia.