Topoisomerase I (TOP1) Inhibitors constitute an emerging payload class to engineer Antibody-Drug-Conjugates (ADCs) as next-generation biopharmaceutical for cancer treatment. Existing ADCs are utilizing camptothecin payloads with lower potency and suffer from limited stability in circulation. With this study, we introduce a novel camptothecin-based linker-payload platform based on the highly potent camptothecin derivative exatecan. First, we describe general challenges that arise from the hydrophobic combination of exatecan and established dipeptidyl p-aminobenzyl-carbamate (PAB) cleavage sites such as reduced antibody conjugation yields and ADC aggregation. After evaluating several linker-payload structures we identified ethynyl-phosphonamidates in combination with a discrete PEG24 chain to compensate for the hydrophobic PAB-exatecan moiety. Furthermore, we demonstrate that the identified linker-payload structure enables the construction of highly loaded DAR8 ADCs with excellent solubility properties. Head-to-head comparison to Enhertu, an approved camptothecin-based ADC, revealed improved target-mediated killing of tumor cells, excellent bystander killing, drastically improved linker stability in vitro and in vivo and superior in vivo efficacy over four tested dose levels in a xenograft model. Moreover, we show that ADCs based on the novel exatecan linker-payload platform exhibit antibody-like pharmacokinetic properties, even when the ADCs are highly loaded with eight drug molecules per antibody. This ADC platform constitutes a new and general solution to deliver TOP1-inhibitors with highest efficiency to the site of the tumor, independent of the antibody and its target, and is thereby broadly applicable to various cancer indications.

中文翻译：

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用于高负载、稳定和有效的抗体药物缀合物的膦酰胺连接的 exatecan 构建体的设计和评估

拓扑异构酶 I (TOP1) 抑制剂构成了一种新兴的有效负载类别，可将抗体药物偶联物 (ADC) 设计为用于癌症治疗的下一代生物制药。现有的 ADC 使用效力较低的喜树碱有效负载，并且循环稳定性有限。通过这项研究，我们介绍了一种基于高效喜树碱衍生物 exatecan 的新型基于喜树碱的连接器有效负载平台。首先，我们描述了 exatecan 和已建立的二肽基对氨基苄基氨基甲酸酯 (PAB) 切割位点的疏水性组合所带来的一般挑战，例如抗体缀合产量降低和 ADC 聚集。在评估了几种接头-有效负载结构后，我们确定了乙炔基-膦酰胺酯与离散的 PEG24 链的组合，以补偿疏水性 PAB-exatecan 部分。此外，我们证明所确定的接头-有效负载结构能够构建具有优异溶解特性的高负载 DAR8 ADC。与 Enhertu（一种已批准的基于喜树碱的 ADC）进行头对头比较，结果显示，靶点介导的肿瘤细胞杀伤能力得到改善，旁观者杀伤效果优异，体外和体内接头稳定性显着提高，体内疗效优于四种测试剂量水平。异种移植模型。此外，我们还表明，基于新型 exatecan 连接器-有效负载平台的 ADC 表现出类似抗体的药代动力学特性，即使每个抗体高度负载 8 个药物分子。该 ADC 平台构成了一种新的通用解决方案，能够以最高效率将 TOP1 抑制剂递送至肿瘤部位，而与抗体及其靶点无关，因此广泛适用于各种癌症适应症。