CD19 and B-cell chronic lymphocytic leukemia: A recent landmark clinical study compared the transcriptomes of CAR-T cells generated from CLL patients who respond well or do not respond to CD19 CAR-T therapy, and confirmed that CAR-T cells from responder expressed key regulators of early memory differentiation while CAR-T cells from non-responder exhibited elevated expression of key regulators of effector T cell differentiation and exhaustion, suggesting these factors are associated with therapeutic efficacy.