CD19 and B-cell chronic lymphocytic leukemia: While CD19 is not a novel target, it remains the quintessential and ideal disease space for a single-arm study to test novel engineered modalities or new receptor designs given the well-established long-term outcome of CD19 CARs in lymphoma and potential applicability to other CD19 + lymphoid malignancies such as acute lymphoblastic leukemia and chronic lymphocytic leukemia where there are larger unmet needs12,19.