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

Abstract

Background: 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.

Methods: 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.

Findings: 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%).

Interpretation: 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).

Funding: 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.

Keywords: Multitarget CAR-T therapy; Paediatric B-Cell precursor acute lymphoblastic leukaemia; Tandem CD19/CD22 CAR-T; Translational research.

Fig. 1

Tandem anti-CD19/CD22 CAR T-cell therapy response. A) Schematic diagram of the tandem anti-CD19/CD22 CAR structure. B) Flow chart of the study. C) Swimmer plot showing clinical responses after tandem anti-CD19/CD22 CAR T-cell product infusion. D) PET-TC imaging of patient P9 before (A.1 and A.2) and 28 days after (B.1 and B.2) tandem anti-CD19/CD22 CAR T-cell infusion. E) Event free survival (EFS) Kaplan–Meier curve in all patients (n = 10). F) Overall survival (OS) Kaplan–Meier curve in all patients (n = 10). For E-F, black dots on the curve represent censored observations. HSCT, haematopoietic stem cell transplantation. MRD, minimal residual disease. EMR, extramedullary relapse. PD, progression of disease. ∗ For P6, 6 reinfusions were performed (every two weeks), the last with 3 doses. ∗∗P4 joined a clinical trial with carfilzomib after relapse, with PD shortly after.

Fig. 2

Tandem anti-CD19/CD22 CAR T-cell product immunophenotype and analysis. A) Tandem anti-CD19/CD22 CAR T-cell expansion in all products manufactured in the CliniMACS Prodigy closed system. B) CD19-CAR and CD22-CAR expression in all products manufactured by flow cytometry. C) CD4⁺ and CD8⁺ cell populations in all 10 products manufactured. D) PD-1 receptor expression on product cells. In C and D, graphs show box and whisker plots (vertical bars, min to max points; box, first to third quartile, with median as horizontal bar). E) Memory subpopulations determined by flow cytometry. Central memory cells (CD45RA⁻CD27⁺), effector memory cells (CD45RA⁻CD27⁻), naïve cells (CD45RA⁺CD27⁺) and TEMRA cells (CD45RA⁺CD27⁻) are represented. F) Specific-lysis by tandem anti-CD19/CD22 CAR T-cells against SEM cell line determined by 4-h Europium-BATDA assay at different E:T ratios. G) Degranulation assay against SEM cell line determined by CD107a expression after 4 h of co-culture at 1:1 or 1:2 E:T ratios (see Methods). A–D and F and G, in green, living patients; in purple, relapsed patient; in black, patients who died.

Fig. 3

Tandem anti-CD19/CD22 CAR T-cell persistence in patients after product infusion. A) Tandem anti-CD19/CD22 CAR expression was determined with anti-CD19 CAR gated on CD3⁺ cells. Left panel, absolute numbers of peripheral blood CAR T-cells per μl in infused patients detected by flow cytometry. Right panel, percentage of CAR ⁺ cells within the T cell compartment. B) Copies per ml as detected using real-time qPCR (see Methods) (16). C) IL-6 levels from serum after CAR T-cell infusion. D) Peak IL-6 levels were upregulated in patients with ICANS or severe CRS. Box and whisker plot shows all points (vertical bars, min to max points; box, first to third quartile, with median as horizontal bar). ^#No CRS group included patients with mild phenotype (I-II grade); CRS group included patients with III-IV grade. In green, living patients; in purple, relapsed patient; in black, patients who died.