Early assessment of treatment efficacy can be invaluable in cases of aggressive tumours, such as glioblastoma. Logun et al. generated glioblastoma organoids (GBOs) from patients participating in a chimeric antigen receptor (CAR) T cell clinical trial to monitor the therapeutic response in real time.

The authors obtained tumour specimens from six patients with glioblastoma enrolled in a phase 1 CAR T cell clinical trial. Using a previously reported protocol, they developed GBOs from the specimens in 2–3 weeks, which they then co-cultured with patient-matched CAR T cells. These GBOs displayed tumour cytolysis. After 6 days of co-culturing, Logun et al. collected the GBOs and analysed them for target antigen expression, which they found was reduced. Finally, they analysed CAR T cell–GBO co-culture media and found a continuous release of cytokines by the activated T cells, which presented similar temporal dynamics with the in vivo kinetics of CAR T cell activation in patients.