Many clinical trials of kinesin spindle protein (KSP) inhibitors have failed due to issues such as high toxicity and a short circulation half-life in vivo. To address the limitations of current KSP inhibitors and thus broad its use in antitumor therapy, this study applied antibody–drug conjugate (ADC) technology to the KSP inhibitor SB-743921, which was coupled with the HER2-specific antibody trastuzumab using a cathepsin B-dependent valine–alanine (Val–Ala, VA) dipeptide-type linker to generate H2-921. Ex vivo and in vivo analyses of H2-921 showed an increased half-life of SB-743921 and prolonged contact time with tumor cells. Furthermore, H2-921 induced apoptosis and incomplete autophagy in HER2-positive cells. In the in vivo analyses, H2-921 had significant tumor-targeting properties, and tumor inhibition by H2-921 was greater than that by traditional KSP inhibitors but similar to that by the positive control drug T-DM1. In conclusion, this study describes a novel application of ADC technology that enhances the antitumor effects of a KSP inhibitor and thus may effectively address the poor clinical efficacy of KSP inhibitors.

驱动蛋白纺锤体蛋白（KSP）抑制剂的许多临床试验因毒性高、体内循环半衰期短等问题而失败。为了解决当前 KSP 抑制剂的局限性，从而扩大其在抗肿瘤治疗中的应用，本研究将抗体药物偶联物 (ADC) 技术应用于 KSP 抑制剂 SB-743921，该抑制剂使用组织蛋白酶 B 与 HER2 特异性抗体曲妥珠单抗偶联依赖缬氨酸-丙氨酸 (Val-Ala, VA) 二肽型连接子生成 H2-921。H2-921 的体外和体内分析显示 SB-743921 的半衰期延长，并且与肿瘤细胞的接触时间延长。此外，H2-921 诱导 HER2 阳性细胞凋亡和不完全自噬。在体内分析中，H2-921具有显着的肿瘤靶向特性，H2-921的肿瘤抑制作用强于传统KSP抑制剂，但与阳性对照药物T-DM1相似。总之，本研究描述了ADC技术的一种新应用，可增强KSP抑制剂的抗肿瘤作用，从而可能有效解决KSP抑制剂临床疗效不佳的问题。