A follow-up single-institutional Phase I study of a modified CD22/4-1BB CAR construct, utilizing a shorter scFv linker, in 17 children with CD19-negative relapse of B-ALL following CD19-directed therapy showed a high CR rate of 77%, 77% of whom were MRD-negative (NCT02650414). The gene discussed is CD19; the disease is acute lymphoblastic leukemia.