CD22 and acute lymphoblastic leukemia: The heterogeneity of ALL in adults indicates that improved outcomes could be obtained by incorporating targeted therapy into frontline treatment such as nelarabine, clofarabine, rituximab, the antibody-drug conjugate inotuzumab ozogamicin (anti-CD22 bound to the antitumor antibiotic calicheamicin), blinatumomab (a bispecific CD3 anti CD19 T cell engager, that links and directs endogenous CD3 T cells against CD19 B cells, inducing apoptosis-BiTE), the first and only FDA-approved BiTE, chimeric antigen receptor T cells and offering enrollment into clinical trials [14,56,57,58,59].