Indeed, the anti-CD19/CD3 bsAb Blinatumomab, first bsAb approved by the FDA, has shown remarkable success in treating a variety of B cell malignancies including MRD positive and relapsed/refractory B cell-acute lymphoblastic leukemia (B-ALL)9, although the therapy proved ineffective in some patients. This evidence concerns the gene CD19 and acute lymphoblastic leukemia.