The most successful therapeutic strategies for locally advanced cancers continue to combine decades-old classical radiosensitizing chemotherapies with radiotherapy. Molecular targeted radiosensitizers offer the potential to improve the therapeutic ratio by increasing tumor-specific kill while minimizing drug delivery and toxicity to surrounding normal tissue. Auristatins are a potent class of anti-tubulins that sensitize cells to ionizing radiation damage and are chemically amenable to antibody conjugation. To achieve tumor-selective radiosensitization, we synthesized and tested anti-HER2 antibody-drug conjugates of two auristatin derivatives with ionizing radiation. Monomethyl auristatin E (MMAE) and monomethyl auristatin F (MMAF) were attached to the anti-HER2 antibodies trastuzumab and pertuzumab through a cleavable linker. While MMAE is cell permeable, MMAF has limited cell permeability as free drug resulting in diminished cytotoxicity and radiosensitization. However, when attached to trastuzumab or pertuzumab, MMAF was as efficacious as MMAE in blocking HER2-expressing tumor cells in G2-M. Moreover, MMAF anti-HER2 conjugates selectively killed and radiosensitized HER2-rich tumor cells. Importantly, when conjugated to targeting antibody, MMAF had the advantage of decreased bystander and off-target effects compared with MMAE. In murine xenograft models, MMAF anti-HER2 antibody conjugates had less drug accumulated in the normal tissue surrounding tumors compared with MMAE. Therapeutically, systemically injected MMAF anti-HER2 conjugates combined with focal ionizing radiation increased tumor control and improved survival of mice with HER2-rich tumor xenografts. In summary, our results demonstrate the potential of cell-impermeable radiosensitizing warheads to improve the therapeutic ratio of radiotherapy by leveraging antibody-drug conjugate technology.

中文翻译：

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使用Auristatin衍生物的抗体结合物降低细胞通透性，对HER2肿瘤进行精密化学放疗。

局部晚期癌症最成功的治疗策略仍是将数十年的经典放射增敏化学疗法与放射疗法相结合。分子靶向放射增敏剂有潜力通过增加肿瘤特异性杀伤率，同时最大程度地减少对周围正常组织的药物递送和毒性，从而提高治疗率。Auristatins是一类有效的抗微管蛋白，可使细胞对电离辐射损伤敏感，并且在化学上适合抗体结合。为了实现肿瘤选择性放射增敏，我们用电离辐射合成并测试了两种耳他汀衍生物的抗HER2抗体-药物偶联物。单甲基耳他汀E（MMAE）和单甲基耳他汀F（MMAF）通过可裂解的连接子与抗HER2抗体曲妥珠单抗和帕妥珠单抗相连。尽管MMAE具有细胞渗透性，但MMAF作为游离药物具有有限的细胞渗透性，从而降低了细胞毒性和放射增敏作用。但是，当附着于曲妥珠单抗或帕妥珠单抗时，MMAF在阻止G2-M中表达HER2的肿瘤细胞方面与MMAE一样有效。此外，MMAF抗-HER2共轭物选择性杀死并放射增敏的富含HER2的肿瘤细胞。重要的是，当与靶向抗体偶联时，与MMAE相比，MMAF具有减少旁观者和脱靶效应的优势。在鼠异种移植模型中，与MMAE相比，MMAF抗-HER2抗体偶联物在肿瘤周围正常组织中积累的药物较少。在治疗上，全身注射的MMAF抗-HER2共轭物与聚焦电离辐射相结合，可以增强肿瘤控制能力，并改善富含HER2的异种移植小鼠的存活率。