The death of a 78-year-old man with a rare blood cancer in an early trial of Cellectis SA's gene-edited chimeric antigen receptor T-cell (CAR T) therapy, UCART-123, triggered an FDA clinical hold on the study and a second test of the experimental treatment. Following closely on last week's FDA approval of Novartis AG's CAR T immunotherapy, Kymriah (tisagenlecleucel), the fatality offered a stark reminder of the risks faced by both companies and patients participating in efforts to advance new gene-edited T-cell-based treatments.