CAR-T cell therapies are transforming the treatment of previously incurable blood cancers, but a large proportion of patients still responds only poorly or not at all to them, calling for new strategies to overcome this challenge. Now, a research team has developed a simple intervention in the form of a biodegradable scaffold material called ‘T-cell enhancing scaffolds’ (TES) that can be locally injected under the skin and used to restimulate CAR-T cells after their administration. This increased their therapeutic efficacy and significantly curbed tumor growth and prolonged animal survival in an aggressive mouse lymphoma model.