CD47 is overexpressed on the surface of many types of cancer cells, including T-cell acute lymphoblastic leukemia (T-ALL) cells. In this study, we have developed a diphtheria toxin (DT)–based bivalent anti-human CD47 immunotoxin (bi-CD47-IT) for the targeted therapy of CD47+ cancers using a unique DT-resistant yeast Pichia pastoris expression system. Bi-CD47-IT demonstrated compelling in vivo efficacy in multiple T-ALL cell line–derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. Bi-CD47-IT significantly prolonged the median survival of the tumor-bearing mice and highly effectively depleted the T-ALL blast cells in the peripheral blood, spleen, liver, bone marrow, brain, and spinal cord in the T-ALL CDX and PDX mouse models. Bi-CD47-IT cured 60% of tumor-bearing mice in a T-ALL Molt-4 CDX mouse model. Because CD47 is also expressed on normal tissues, including red blood cells and lymphocytes, specificity is a concern. We thus analyzed the in vitro binding avidity and hemagglutination of bi-CD47-IT in human red blood cells, finding no binding or hemagglutination. We further performed a toxicity study of bi-CD47-IT in humanized mice, which showed that bi-CD47-IT transiently depleted the human lymphocytes for ∼4 weeks after the 10-day treatment. No clinical adverse events were observed. As a result, bi-CD47-IT appears to possess the “optimal” binding avidity, with effective binding to human CD47+ T-ALL tumor cells, no binding to human red blood cells, and weak binding to human lymphocytes. We believe that bi-CD47-IT is a promising and safe therapeutic drug candidate for the targeted therapy of CD47+ cancers.

中文翻译：

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二价 CD47 免疫毒素靶向治疗 T 细胞急性淋巴细胞白血病


CD47 在许多类型的癌细胞表面过表达，包括 T 细胞急性淋巴细胞白血病 （T-ALL） 细胞。在这项研究中，我们开发了一种基于白喉毒素 （DT） 的二价抗人 CD47 免疫毒素 （bi-CD47-IT），用于使用独特的 DT 抗性酵母 Pichia pastoris 表达系统靶向治疗 CD47 + 癌症。Bi-CD47-IT 在多个 T-ALL 细胞系来源的异种移植物 （CDX） 和患者来源的异种移植物 （PDX） 小鼠模型中显示出令人信服的体内疗效。在 T-ALL CDX 和 PDX 小鼠模型中，Bi-CD47-IT 显着延长了荷瘤小鼠的中位生存期，并高效消耗了外周血、脾脏、肝脏、骨髓、脑和脊髓中的 T-ALL 原始细胞。Bi-CD47-IT 在 T-ALL Molt-4 CDX 小鼠模型中治愈了 60% 的荷瘤小鼠。由于 CD47 也在正常组织（包括红细胞和淋巴细胞）上表达，因此特异性是一个问题。因此，我们分析了 bi-CD47-IT 在人红细胞中的体外结合亲和力和血凝反应，发现没有结合或血凝反应。我们进一步在人源化小鼠中进行了 bi-CD47-IT 的毒性研究，结果表明 bi-CD47-IT 在治疗 10 天后 ∼ 4 周内瞬时耗尽了人类淋巴细胞。未观察到临床不良事件。因此，bi-CD47-IT 似乎具有“最佳”结合亲和力，与人 CD47+ T-ALL 肿瘤细胞有效结合，与人红细胞不结合，与人淋巴细胞结合较弱。我们相信 bi-CD47-IT 是一种有前途且安全的靶向治疗 CD47+ 癌症的候选治疗药物。