Chimeric antigen receptor (CAR) T cell immunotherapies targeting CD19 or CD22 induce remissions in the majority of patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL), although relapse due to target antigen loss or downregulation has emerged as a major clinical dilemma. Accordingly, great interest exists in developing CAR T cells directed against alternative leukemia cell surface antigens that may help to overcome immunotherapeutic resistance. The fms-like tyrosine kinase 3 receptor (FLT3) is constitutively activated via FLT3 mutation in acute myeloid leukemia (AML) or wild-type FLT3 overexpression in KMT2A (lysine-specific methyltransferase 2A)-rearranged B-acute lymphoblastic leukemia (ALL), which are associated with poor clinical outcomes in children and adults. We developed monovalent FLT3-targeted CAR T cells (FLT3CART) and bispecific CD19xFLT3CART and assessed their anti-leukemia activity in preclinical models of FLT3-mutant AML and KMT2Arearranged infant ALL. We report robust in vitro FLT3CART-induced cytokine production and cytotoxicity against AML and ALL cell lines with minimal cross-reactivity against normal hematopoietic and non-hematopoietic tissues. We also observed potent in vivo inhibition of leukemia proliferation in xenograft models of both FLT3-mutant AML and KMT2A-rearranged ALL, including a post-tisagenlecleucel ALL-to-AML lineage switch patient-derived xenograft model pairing. We further demonstrate significant in vitro and in vivo activity of bispecific CD19xFLT3CART against KMT2A-rearranged ALL and posit that this additional approach might also diminish potential antigen escape in these high-risk leukemias. Our preclinical data credential FLT3CART as a highly effective immunotherapeutic strategy for both FLT3-mutant AML and KMT2A-R ALL that is poised for further investigation and clinical translation.

中文翻译：

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FLT3定向嵌合抗原受体T细胞免疫疗法针对FLT3突变型急性髓系白血病和KMT2A重排急性淋巴细胞白血病具有有效的临床前活性。


靶向 CD19 或 CD22 的嵌合抗原受体 (CAR) T 细胞免疫疗法可诱导大多数复发/难治性 B 细胞急性淋巴细胞白血病 (B-ALL) 患者的缓解，尽管由于靶抗原丢失或下调导致的复发已成为主要的原因。临床困境。因此，人们对开发针对替代性白血病细胞表面抗原的 CAR T 细胞抱有极大兴趣，这可能有助于克服免疫治疗耐药性。 fms 样酪氨酸激酶 3 受体 (FLT3) 通过急性髓系白血病 (AML) 中的 FLT3 突变或 KMT2A（赖氨酸特异性甲基转移酶 2A）重排 B 急性淋巴细胞白血病 (ALL) 中野生型 FLT3 过度表达而被组成型激活，这与儿童和成人不良的临床结果有关。我们开发了单价 FLT3 靶向 CAR T 细胞 (FLT3CART) 和双特异性 CD19xFLT3CART，并评估了它们在 FLT3 突变 AML 和 KMT2Arranged 婴儿 ALL 临床前模型中的抗白血病活性。我们报告了体外 FLT3CART 诱导的针对 AML 和 ALL 细胞系的细胞因子产生和细胞毒性，与正常造血和非造血组织的交叉反应性最小。我们还在 FLT3 突变 AML 和 KMT2A 重排 ALL 异种移植模型中观察到对白血病增殖的有效体内抑制，包括 tisagenlecleucel 后 ALL 至 AML 谱系转换患者来源的异种移植模型配对。我们进一步证明了双特异性 CD19xFLT3CART 针对 KMT2A 重排 ALL 的显着体外和体内活性，并假设这种额外的方法也可能减少这些高危白血病中潜在的抗原逃逸。 我们的临床前数据证明 FLT3CART 作为针对 FLT3 突变 AML 和 KMT2A-R ALL 的高效免疫治疗策略，准备进行进一步研究和临床转化。