The outcome of acute myeloid leukemia (AML) remains poor, and immunotherapy has the potential to improve this. T cells expressing chimeric antigen receptors (CARs) or bispecific T cell engagers targeting CD123 are actively being explored in preclinical and/or early phase clinical studies. We have shown that T cells expressing CD123-specific bispecific T cell engagers (CD123.ENG T cells) have anti-AML activity. However, like CAR T cells, their effector function diminishes rapidly once they are repeatedly exposed to antigenpositive target cells. Here we sought to improve the effector function of CD123.ENG T cells by expressing inducible costimulatory molecules consisting of MyD88 and CD40 (iMC), MyD88 (iM), or CD40 (iC), which are activated by a chemical inducer of dimerization (CID). CD123.ENG T cells expressing iMC, iM, or iC maintained their antigen specificity in the presence of CID as judged by cytokine production (IFNc, IL-2) and their cytolytic activity. In repeat stimulation assays, activating iMC and iM, in contrast to iC, enabled CD123.ENG T cells to secrete cytokines, expand, and kill CD123-positive target cells repeatedly. Activating iMC in CD123.ENG T cells consistently improved anti-tumor activity in an AML xenograft model. This translated into a significant survival advantage in comparison to mice that received CD123.ENG or CD123.ENG.iC T cells. In contrast, activation of only iM in CD123.ENG T cells resulted in donor-dependent antitumor activity. Our work highlights the need for both toll-like receptor (TLR) pathway activation via MyD88 and provision of costimulation via CD40 to consistently enhance the antitumor activity of CD123.ENG T cells.

中文翻译：

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通过 MyD88 和 CD40 共刺激提高 CD123 特异性 Engager T 细胞的抗急性髓性白血病活性。

急性髓性白血病 (AML) 的预后仍然很差，而免疫疗法有可能改善这一状况。表达嵌合抗原受体 (CAR) 的 T 细胞或靶向 CD123 的双特异性 T 细胞参与物正在临床前和/或早期临床研究中积极探索。我们已经证明表达 CD123 特异性双特异性 T 细胞接合器的 T 细胞（CD123.ENG T 细胞）具有抗 AML 活性。然而，与 CAR T 细胞一样，一旦它们反复暴露于抗原阳性靶细胞，它们的效应功能就会迅速减弱。在这里，我们试图通过表达由 MyD88 和 CD40 (iMC)、MyD88 (iM) 或 CD40 (iC) 组成的诱导型共刺激分子来改善 CD123.ENG T 细胞的效应功能，这些分子由二聚化化学诱导剂 (CID) 激活). 表达 iMC、iM、或 iC 在 CID 存在的情况下保持其抗原特异性，如通过细胞因子产生（IFNc、IL-2）及其细胞溶解活性所判断的。在重复刺激试验中，与 iC 相比，激活 iMC 和 iM 使 CD123.ENG T 细胞能够反复分泌细胞因子、扩增和杀死 CD123 阳性靶细胞。在 CD123.ENG T 细胞中激活 iMC 持续改善 AML 异种移植模型中的抗肿瘤活性。与接受 CD123.ENG 或 CD123.ENG.iC T 细胞的小鼠相比，这转化为显着的生存优势。相反，CD123.ENG T 细胞中仅激活 iM 会导致供体依赖性抗肿瘤活性。我们的工作强调了通过 MyD88 激活 toll 样受体 (TLR) 通路和通过 CD40 提供共刺激以持续增强 CD123.ENG T 细胞的抗肿瘤活性的必要性。