Tumor-derived extracellular vesicles (EVs) carry potent immunosuppressive factors that affect the antitumor activities of immune cells. A significant part of the immunoinhibitory activity of EVs is attributable to CD73, a GPI-anchored ecto-5′-nucleotidase involved in the conversion of tumor-derived proinflammatory extracellular ATP (eATP) to immunosuppressive adenosine (ADO). The CD73-antagonist antibody oleclumab inhibits cell surface-exposed CD73 and is currently undergoing clinical testing for cancer immunotherapy. However, a strategy to selectively inhibit CD73 exposed on EVs is not available. Here, we present a novel bispecific antibody (bsAb) CD73xEpCAM designed to bind with high affinity the common EV surface marker EpCAM and concurrently inhibit CD73. Unlike oleclumab, bsAb CD73xEpCAM potently inhibited the immunosuppressive activity of EVs from CD73^pos/EpCAM^pos carcinoma cell lines and patient-derived colorectal cancer cells. Taken together, selective blockade of EV-exposed CD73 by bsAb CD73xEpCAM may be useful as an alternate or complementary targeted approach in cancer immunotherapy.

肿瘤来源的细胞外囊泡（EV）携带有效的免疫抑制因子，影响免疫细胞的抗肿瘤活性。 EV 的免疫抑制活性的一个重要部分可归因于 CD73，CD73 是一种 GPI 锚定的 5′-核酸外切酶，参与将肿瘤源性促炎细胞外 ATP (eATP) 转化为免疫抑制腺苷 (ADO)。 CD73拮抗剂抗体oleclumab可抑制细胞表面暴露的CD73，目前正在进行癌症免疫治疗的临床测试。然而，尚无选择性抑制 EV 上暴露的 CD73 的策略。在这里，我们提出了一种新型双特异性抗体 (bsAb) CD73xEpCAM，旨在以高亲和力结合常见的 EV 表面标记 EpCAM，同时抑制 CD73。与 oleclumab 不同，bsAb CD73xEpCAM 有效抑制来自 CD73 ^pos /EpCAM ^pos癌细胞系和患者来源的结直肠癌细胞的 EV 的免疫抑制活性。综上所述，bsAb CD73xEpCAM 选择性阻断 EV 暴露的 CD73 可能可作为癌症免疫治疗中的替代或补充靶向方法。