Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California.
Department of Pathology, University of California San Diego, La Jolla, California.
Mol Cancer Ther. 2020 Jan;19(1):157-167. doi: 10.1158/1535-7163.MCT-18-1302. Epub 2019 Oct 9.
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 G-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.
最成功的局部晚期癌症治疗策略仍然是将几十年前的经典放射增敏化疗与放射治疗相结合。分子靶向放射增敏剂有可能通过增加肿瘤特异性杀伤而最小化药物输送和对周围正常组织的毒性来提高治疗比率。auristatins 是一种有效的抗微管蛋白药物,可使细胞对电离辐射损伤敏感,并且在化学上适合与抗体偶联。为了实现肿瘤选择性放射增敏,我们合成并测试了两种 auristatin 衍生物与电离辐射的抗 HER2 抗体-药物偶联物。单甲基 auristatin E(MMAE)和单甲基 auristatin F(MMAF)通过可裂解接头连接到抗 HER2 抗体曲妥珠单抗和帕妥珠单抗上。虽然 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,导致细胞毒性和放射增敏作用减弱。然而,当连接到曲妥珠单抗或帕妥珠单抗上时,MMAF 在阻止 G-M 中表达 HER2 的肿瘤细胞方面与 MMAE 一样有效。此外,MMAF 抗 HER2 缀合物选择性地杀死和放射增敏 HER2 丰富的肿瘤细胞。重要的是,与 MMAE 相比,当与靶向抗体偶联时,MMAF 具有减少旁观者和脱靶效应的优势。在小鼠异种移植模型中,与 MMAE 相比,MMAF 抗 HER2 抗体缀合物在肿瘤周围正常组织中积累的药物较少。在治疗方面,系统注射的 MMAF 抗 HER2 缀合物与焦点电离辐射相结合,增加了富含 HER2 的肿瘤异种移植小鼠的肿瘤控制并提高了生存率。总之,我们的结果表明,细胞不可渗透的放射增敏弹头通过利用抗体-药物偶联物技术有可能提高放射治疗的治疗比率。