Chimeric antigen receptor T cells targeting CD7 in a child with high-risk T-cell acute lymphoblastic leukemia

Effective systemic treatments for relapsed or refractory T-cell acute lymphoblastic leukemia (T-ALL) are limited. Recent clinical application of chimeric antigen receptor (CAR) immunotherapy has demonstrated successful control of B-cell malignancies by CAR-T cells; however, designing CARs for T-ALL remains a challenge. CD7 overexpression in T-cell malignancies may be an attractive target for immunotherapy in T-ALL. This study aimed to describe the safe and effective use of autologous CD7-CAR T cells (4SCAR7) for the treatment of T-ALL with induction failure in an 11-year-old patient. Based on The Chinese Children's Cancer Group-ALL (CCCG-ALL) study protocol, minimal residual disease (MRD) by flow cytometry (FC) analysis was detected on days 19 and 46 of remission induction. At the end of remission-induction chemotherapy, the patient achieved morphologic complete remission, though with MRD 16.13% and RT-PCR of KMT2A-MLLT1 fusion positive, which indicated induction failure. The cerebrospinal fluid (CSF) was negative for blasts at diagnosed. CAR-T therapy and allogeneic transplant were recommended as the next treatment options. CD3⁺ lymphocytes were collected from the patient 18 days after the high-dose MTX chemotherapy through leukapheresis. The 4SCAR7 CD7-targeting CAR-T cells were generated thereafter. The patient received lymphodepleting chemotherapy prior to 4SCAR7 infusion. Oral administration of itraconazole and sulfamethoxazole was performed from day 0 after CAR-T cell infusion. The patient did not have hypotension, hypoxia, or serious biochemical change or abnormality, but had fever on day 9. Although grade 1 cytokine-release syndrome (CRS) was diagnosed, it was successfully treated with ibuprofen. Anti-CD7 CAR transgene copy numbers in peripheral blood were determined by qPCR, which showed effective expansion initially, then dropped quickly, and persisted at a low level. Although experienced cytopenia from days 14 to 21, the patient achieved remission on day 17. After complete remission, the patient received hematopoietic stem cell transplantation (HSCT) and has recovered well to thisdate. Overall, this report suggested that 4SCAR7 could be a safe and effective strategy for the treatment of pediatric patients with high-risk T-cell malignancies.