Although loss of TET2 led to increased persistence of CAR T cells and complete remission in a patient with chronic lymphocytic leukemia, clonal expansion of TET2-deficient CAR T cells is antigen independent and the cells are prone to obtain additional somatic mutations.4 Therefore, future studies should explore whether CARD11-PIK3R3 gene fusion would be a safer approach compared to TET2-editing. This evidence concerns the gene TET2 and B-cell chronic lymphocytic leukemia.