Treatment with the CDK2/9 inhibitor fadraciclib led to significant response and an overall survival benefit in temozolomide-resistant Th-MYCN tumors and allografts generated from these resistant tumours. These findings demonstrate the utility of genetically-engineered mouse models as platforms to dissect the evolution of chemoresistance in neuroblastoma and they provide a mechanistic rationale to support the evaluation of fadraciclib in ongoing paediatric phase I studies of chemotherapy combined with temozolomide in relapsed, treatment refractory neuroblastoma patients.