造血干细胞移植后复发急性B淋巴细胞白血病CD19 CAR-T细胞治疗后的维持治疗 Translated title: Maintenance therapy following CD19 CAR-T treatment for relapsed B-cell acute lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation

Abstract

目的

探讨异基因造血干细胞移植后复发急性B淋巴细胞白血病（B-ALL）CD19 CAR-T细胞治疗缓解后的维持治疗，观察单独输注供者造血干细胞和供者T淋巴细胞对CD19 CAR-T细胞扩增的影响。

方法

1例难治B-ALL患者，CD19 CAR-T（鼠源，克隆号：FMC63）细胞治疗后桥接同胞全相合异基因造血干细胞移植，后再次复发。接受CD19 CAR-T（可变区人源化的FMC63）细胞治疗再次缓解，缓解后先后接受单独输注供者造血干细胞、供者T淋巴细胞的维持治疗，期间监测患者细胞因子水平、CD19 CAR-T细胞比例、CD19 CAR的DNA表达变化，观察骨髓白血病细胞比例及供者嵌合情况。另外，通过制备小鼠CD19 CAR-T（FMC63）细胞，并将CAR-T细胞注射至同窝小鼠体内，14 d后，再次注射同窝小鼠的B淋巴细胞，在此过程中观察CAR-T细胞、B淋巴细胞比例以及CD19 CAR的DNA表达，以此来模拟临床治疗过程。

结果

①患者输注人源化CD19 CAR-T细胞后第14天，疗效评估达完全缓解（CR），供者嵌合率为99.76%，细胞因子释放综合征1级。②人源化CD19 CAR-T细胞治疗缓解后，单独输注供者造血干细胞维持治疗，输注后第24天出现移植物抗宿主病（GVHD），患者GVHD期间伴有外周血CD19 CAR-T细胞比例及CD19 CAR DNA水平的升高，并随GVHD缓解下降。过程中患者维持CR且供者嵌合率为99.69%。③随后单独输注供者T淋巴细胞维持治疗，回输后第12天患者出现GVHD，而患者外周血CD19 CAR-T细胞比例及CD19 CAR的DNA水平并未出现再次升高。过程中患者维持CR且供者嵌合率为99.87%。④C57小鼠体内试验证实，CAR-T细胞输注后小鼠体内CAR-T细胞扩增及DNA表达上调，同时CD19 ⁺ B淋巴细胞耗竭。之后输注CD19 ⁺ B淋巴细胞，CD19 CAR-T细胞扩增和CD19 CAR的DNA表达再度上调。

结论

供者造血干细胞、供者T淋巴细胞的单独输注，可作为异基因造血干细胞移植后复发B-ALL接受CD19 CAR-T治疗缓解后的维持治疗手段，且输注供者造血干细胞诱发GVHD同时出现CD19 CAR-T细胞和CD19 CAR的DNA表达上调，有可能进一步清除残留灶。

Translated abstract

Objective

This study aimed to evaluate the maintenance therapy following an anti-CD19-CAR T-cell therapy for a B-cell acute lymphoblastic leukemia (ALL) patient who relapsed after allogeneic hematopoietic cell transplantation (allo-HSCT) and investigate the effect of donor stem cells and donor T lymphocyte infusion on the amplification of CD19 CAR-T cells.

Methods

One refractory B-ALL patient relapsed after murine CD19 CAR-T cell therapy followed by a sibling allo-HSCT. He underwent a humanized CD19 CAR-T cell therapy followed by donor stem cell and donor T lymphocytes infusions as maintenance therapy in our hospital. The level of cytokines, the proportion of CD19 CAR-T cell, the level of CAR19 DNA expression in the peripheral blood, and the proportion of leukemia cells and donor chimerism in the bone marrow were detected. Correspondingly, T lymphocytes from the C57 spleen were separated to modify the CD19 CAR lentivirus and refused into C57 mice, and after 14 days, the B lymphocytes from C57 mice were separated and refused into the same C57 mice. The CD19 CAR T cells, B cells, and CD19 CAR gene counts in the peripheral blood were evaluated at different time points.

Results

①The patient achieved a complete response (CR) 14 days after a humanized CD19 CAR-T therapy with grade 1 cytokine release syndrome (CRS) and restored a donor chimerism to 99.76%. ② Following the remission from humanized CD19 CAR-T therapy, the patient received a maintenance therapy of donor stem cell infusion. Mild graft-versus-host disease (GVHD) manifested 24 days after infusion with an increased proportion of CD19 CAR-T cells and an increased level of CAR19 DNA expression in the peripheral blood. It fell with the remission of GVHD. The patient maintained CR and 99.69% donor chimerism during this period. ③ Throughout the subsequent donor T lymphocytes maintenance therapy, mild GVHD surfaced12 days after infusion without an increased proportion of CD19 CAR-T cells and an increased level of CAR19 DNA expression in the peripheral blood. The patient maintained CR and 99.87% donor chimerism during this period. ④ In vivo experiments on C57 mice confirmed that the proportion of CD19 CAR-T cells and the level of CAR19 DNA expression were upregulated in mice following CAR-T cell infusion, accompanied by depletion of CD19 ⁺ B lymphocyte. After infusion of CD19 ⁺ B lymphocyte cells, an increased proportion of CD19 CAR-T cells and an increased level of CAR19 DNA expression in the peripheral blood were observed again.

Conclusion

The infusion of donor stem cells and donor T lymphocytes could be used as a maintenance treatment after CD19 CAR-T cell therapy for B-ALL patients who relapsed after allo-HSCT. Infusion of donor stem cells induced an increased proportion of CD19 CAR-T cells and an increased level of CAR19 DNA expression with the occurrence of GVHD. It might lead to further elimination of minimal residual disease.