Tandem CD19/CD22 CAR T-cells as potential therapy for children and young adults with high-risk r/r B-ALL

Chimeric antigen receptor (CAR) T-cells targeting CD19 have shown impressive outcomes in refractory/relapsed B-cell acute lymphoblastic leukaemia (r/r B-ALL); however, frequent relapse demands multi-targeted approaches. We report Spanish clinical data on the safety and efficacy of tandem anti-CD19/CD22 CAR T-cells administered on a compassionate use basis in a cohort of 10 heavily pretreated paediatric, adolescent, and young adult (AYA) patients with r/r B-ALL. Most (9/10) of the patients had relapsed B-ALL, 7 having received previous anti-CD19 CAR T-cell therapy and 6 haematopoietic stem cell transplantation (HSCT). Two patients had Down syndrome. Increased high-grade CRS/ICANS and proinflammatory markers (IL-6, LDH and ferritin) correlated with patients with a high tumour burden (TB) before lymphodepletion. Complete remission on day +28 post-infusion was achieved in 8/10 patients (7 with MRD-), and 5/7 patients received HSCT as consolidative therapy within three months post-infusion. Two patients with early relapse after tandem anti-CD19/CD22 CAR received rescue therapy and HSCT. At the 18-month follow up, overall survival (OS) was 70% (95% CI, 47%-100%). Tandem anti-CD19/CD22 CAR T-cell administration combined with consolidative HSCT is a promising therapeutic approach, though managing bridging therapy and reducing the TB prior to infusion remain key challenges (REALL_CART trial, NCT06709469, EudraCT 2023-509723-41-01). This work was supported by a grant from the Instituto de Salud Carlos III to APM PI22/01226, two grants from CRIS Cancer Foundation to Beat Cancer as part of the projects "Advanced Cell Therapy Unit Hospital Universitario La Paz" and JM "Proyecto Mateo: CAR T-cell therapy for juvenile myelomonocytic leukaemia" and "Terapia avanzada CAR-T CD19/CD22", Ayuda Nominativa de la Consejería de Investigación, Comunidad de Madrid, Spain. Work in MI lab was funded by a grant from the Spanish Ministry of Science and Innovation (PID2020-114148RB-I00). VGG was granted with Río Hortega (AES 2022 exp. Nº. CM22/00078) and Juan Rodés (AES 2024 exp. Nº. JR24/00003) contracts from the Carlos III Health Institute (ISCIII) through the European Funds of the Recovery, Transformation and Resilience Plan and financed by the European Union NextGenerationEU.