Approved by the FDA in 2017, tisagenlecleucel is a genetically engineered product that forces a patient’s own T-cells to destroy acute lymphoblastic leukemia, or ALL. These chimeric antigen receptor cells, or CAR T-cells, work by targeting CD19, a surface protein most ALL cells express. The problem is that, in about half of relapsed cases, ALL cells mutate to lose CD19, leaving the CAR T-cells nothing to attach to. One potential solution is a CAR T-cell product that can seek another surface protein, CD22. Researchers at Children’s Hospital Colorado and the Gates Biomanufacturing Facility on the Anschutz Medical Campus are currently manufacturing a product that can target both proteins – and the clinical trial is enrolling.