Several CAR-T-cell therapies have been approved for hematological malignancies, and ongoing investigations are expanding CAR-T-cell therapy to solid tumors and other indications beyond cancer.1,2 However, extensive clinical applications have raised a series of safety concerns, including the risk for secondary T-cell malignancies following CD19-directed or BCMA-directed CAR-T-cell therapies, which may result from inaccurate transgene integration of the CAR. The gene discussed is CD19; the disease is cancer.