A new Science Immunology analysis of patients treated with Kite Pharma’s Yescarta (axi-cel) identified genetic signatures associated with toxicity risk. Led by Mark Leick of Massachusetts General Hospital, the study examined data from the Zuma-1 and Zuma-7 trials to link patient DNA features to CAR-T behavior. Researchers highlighted STXBP2 mutations as a standout marker in six Zuma-1 patients—each experiencing toxicity after treatment—while no similar relationship emerged in Zuma-7. The team is also exploring a gene tied to CAR-T cell replication capacity in the body. The findings support engineering strategies aimed at reducing variability in cytokine release–type toxicity across patients, using genomics to inform safer CAR-T designs.