Blockade of CD47, the “do not eat me” signal, has limited effects in solid tumors despite its potent antitumor effects in hematopoietic malignancies. Taking advantage of the high expression of cytotoxic T lymphocyte–associated protein 4 (CTLA-4) on T_reg cells and abundant Fc receptor–expressing active phagocytes inside the tumor microenvironment (TME), we designed and tested a heterodimer combining an anti–CTLA-4 antibody, which targets T_reg cells, with the CD47 ligand, signal regulatory protein α (SIRPα), to selectively block CD47 on intratumoral T_reg cells. We hypothesized that heterodimer treatment would increase antibody-dependent cellular phagocytosis of the targeted T_reg cells. We found that anti–CTLA-4×SIRPα preferentially depleted ICOS^high immunosuppressive T_reg cells in the TME and enhanced immunity against solid tumors, including MC38 and CT26 murine colon cancers. Mechanistically, we found that CD47 expression on T_reg cells limited anti–CTLA-4–mediated depletion and Fc on the heterodimer-enhanced depletion. Furthermore, anti-human CTLA-4×SIRPα depleted tumor T_reg cells and exhibits less toxicity than anti-human CTLA-4 in a humanized mouse model. Collectively, these results demonstrate that simultaneously modulating both “eat me” and do not eat me signals induces T_reg cell depletion inside the TME and may be an effective strategy for treating solid tumors.

尽管 CD47 在造血系统恶性肿瘤中具有强大的抗肿瘤作用，但“不要吃我”信号 CD47 的阻断在实体瘤中的作用有限。利用 T _reg细胞上细胞毒性 T 淋巴细胞相关蛋白 4 (CTLA-4) 的高表达和肿瘤微环境 (TME) 内丰富的表达 Fc 受体的活性吞噬细胞，我们设计并测试了一种结合抗 CTLA 的异二聚体-4 抗体，靶向 T _reg细胞，与 CD47 配体信号调节蛋白 α (SIRPα) 选择性阻断肿瘤内 T _reg细胞上的 CD47。我们假设异二聚体治疗会增加靶向 T _{reg的抗体依赖性细胞吞噬作用}细胞。我们发现抗 CTLA-4×SIRPα 优先耗尽TME 中的ICOS^高免疫抑制性 T _{reg细胞，并增强对实体瘤（包括 MC38 和 CT26 小鼠结肠癌）的免疫力。}从机制上讲，我们发现 T _reg细胞上的 CD47 表达限制了抗 CTLA-4 介导的消耗和 Fc 对异二聚体增强的消耗。此外，抗人 CTLA-4×SIRPα 耗尽了肿瘤 T _reg细胞，并且在人源化小鼠模型中表现出比抗人 CTLA-4 更低的毒性。总的来说，这些结果表明，同时调节“吃我”和“不吃我”信号可诱导TME 内的T _{reg细胞耗竭，这可能是治疗实体瘤的有效策略。}