Developers of chimeric antigen receptor (CAR) T-cell therapies are working in a state of tempered optimism. As of September 2021, the US Food and Drug Administration has approved only five such products, two coming this year. Now that those approved products have demonstrated the viability of CAR-based immunotherapies, drug developers are trying to address significant limitations that have come to light with increases in available clinical data and bioprocess knowledge. One shortcoming concerns therapeutic efficacy. Blood cancer patients who have…