Mesothelin (MSLN) is a cell surface glycoprotein overexpressed in several solid malignancies, including gastric, lung, mesothelioma, pancreatic and ovarian cancers. While several MSLN-targeting therapeutic approaches are in development, only limited efficacy has been achieved in patients. A potential shortcoming of several described antibody-based approaches is that they target the membrane distal region of MSLN and, additionally, are known to be handicapped by the high levels of circulating soluble MSLN in patients. We show here, using monoclonal antibodies (mAbs) targeting different MSLN-spanning epitopes, that the membrane-proximal region resulted in more efficient killing of MSLN-positive tumor cells in antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Surprisingly, no augmented killing was observed in antibody-dependent cellular phagocytosis (ADCP) by mAbs targeting this membrane-proximal region. To further increase the ADCP potential, we, therefore, generated bispecific antibodies (bsAbs) coupling a high-affinity MSLN binding arm to a blocking CD47 arm. Here, targeting the membrane-proximal domain of MSLN demonstrated enhanced ADCP activity compared to membrane-distal domains when the bsAbs were used in in vitro phagocytosis killing assays. Importantly, the superior anti-tumor activity was also translated in xenograft tumor models. Furthermore, we show that the bsAb approach targeting the membrane-proximal epitope of MSLN optimized ADCC activity by augmenting FcγR-IIIA activation and enhanced ADCP via a more efficient blockade of the CD47/SIRPα axis.

中文翻译：

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在间皮素上靶向膜近端表位可增加阻断CD47的双特异性抗体对间皮素阳性肿瘤的杀伤活性。

间皮素（MSLN）是在几种实体恶性肿瘤中过表达的细胞表面糖蛋白，包括胃癌，肺癌，间皮瘤，胰腺癌和卵巢癌。尽管有几种针对MSLN的治疗方法正在开发中，但在患者中仅获得了有限的疗效。所描述的几种基于抗体的方法的潜在缺点是它们靶向MSLN的膜远端区域，此外，已知患者体内高水平的循环可溶性MSLN会妨碍这些方法。我们在这里显示，使用针对不同MSLN跨抗原决定簇的单克隆抗体（mAbs），膜近端区域在依赖抗体的细胞介导的细胞毒性（ADCC）分析中导致更有效地杀死MSLN阳性肿瘤细胞。出奇，在针对抗体的细胞吞噬作用（ADCP）中，未观察到针对该膜近端区域的单克隆抗体的杀伤作用增强。因此，为了进一步增加ADCP潜力，我们生成了双特异性抗体（bsAbs），将高亲和力MSLN结合臂与阻断性CD47臂偶联。在这里，与bsAbs用于体外吞噬细胞杀伤试验相比，靶向MSLN的膜近端域表现出增强的ADCP活性。重要的是，在异种移植肿瘤模型中也翻译了优异的抗肿瘤活性。此外，我们表明，针对bsAb的方法通过增强FcγR-IIIA激活和通过更有效地阻断CD47 /SIRPα轴来增强ADCP，从而针对MSLN的膜近表位优化了ADCC活性。