Treatment of patients with human epidermal growth factor receptor 2 (HER2)–expressing tumors using the monoclonal antibody trastuzumab increases survival. The Affibody-based peptide nucleic acid (PNA)–mediated pretargeted radionuclide therapy has demonstrated efficacy against HER2-expressing xenografts in mice. Structural studies suggest that Affibody molecules and trastuzumab bind to different epitopes on HER2. The aim of this study was to test the hypothesis that a combination of PNA-mediated pretargeted radionuclide therapy and trastuzumab treatment of HER2-expressing xenografts can extend survival compared with monotherapies. Methods: Mutual interference of the primary pretargeting probe Z_HER2:342-SR-HP1 and trastuzumab in binding to HER2-expressing cell lines was investigated in vitro. Experimental therapy evaluated the survival of mice bearing HER2-expressing SKOV-3 xenografts after treatment with vehicle, trastuzumab only, pretargeting using Affibody-PNA chimera Z_HER2:342-SR-HP1 and complementary probe ¹⁷⁷Lu-HP2, and combination of trastuzumab and pretargeting. The ethical permit limited the study to 90 d. The animals’ weights were monitored during the study. After study termination, samples of liver and kidneys were evaluated by a veterinary pathologist for toxicity signs. Results: The presence of a large molar excess of trastuzumab had no influence on the affinity of Z_HER2:342-SR-HP1 binding to HER2-expressing cells in vitro. The affinity of trastuzumab was not affected by a large excess of Z_HER2:342-SR-HP1. The median survival of mice treated with trastuzumab (75.5 d) was significantly longer than the survival of mice treated with a vehicle (59.5 d). Median survival of mice treated with pretargeting was not reached by day 90. Six mice of 10 in this group survived, and 2 had complete remission. All mice in the combination treatment group survived, and tumors in 7 mice had disappeared at study termination. There was no significant difference between animal weights in the different treatment groups. No significant pathologic alterations were detected in livers and kidneys of treated animals. Conclusion: Treatment of mice bearing HER2-expressing xenografts with the combination of trastuzumab and Affibody-mediated PNA-based radionuclide pretargeting significantly increased survival compared with monotherapies. Cotreatment was not toxic for normal tissues.

使用单克隆抗体曲妥珠单抗治疗表达人表皮生长因子受体 2 (HER2) 的肿瘤患者可提高生存率。基于亲和体的肽核酸 (PNA) 介导的预靶向放射性核素疗法已证明对小鼠中表达 HER2 的异种移植物有效。结构研究表明 Affibody 分子和曲妥珠单抗结合 HER2 上的不同表位。本研究的目的是检验这样一个假设，即与单一疗法相比，PNA 介导的预靶向放射性核素疗法和曲妥珠单抗疗法联合治疗表达 HER2 的异种移植物可以延长生存期。方法：主要预靶向探针 Z _HER2:342 -SR- HP1的相互干扰在体外研究了曲妥珠单抗与 HER2 表达细胞系的结合。实验疗法评估了携带表达 HER2 的 SKOV-3 异种移植物的小鼠在使用载体、仅曲妥珠单抗、使用 Affibody-PNA 嵌合体 Z _HER2:342 -SR- HP1和互补探针¹⁷⁷ Lu - HP2以及曲妥珠单抗和曲妥珠单抗的组合进行预靶向治疗后的存活率预定位。伦理许可将研究限制为 90 天。在研究期间监测动物的体重。研究终止后，由兽医病理学家评估肝脏和肾脏样本的毒性迹象。结果：存在大量摩尔过量的曲妥珠单抗对 Z _HER2:342的亲和力没有影响-SR- HP1在体外与 HER2 表达细胞结合。曲妥珠单抗的亲和力不受大量过量的 Z _HER2:342 -SR- HP1的影响。用曲妥珠单抗治疗的小鼠的中位生存期（75.5 天）明显长于用载体治疗的小鼠的生存期（59.5 天）。到第 90 天时，接受预靶向治疗的小鼠的中位生存期未达到。该组中的 10 只小鼠中有 6 只存活下来，其中 2 只完全缓解。联合治疗组的所有小鼠均存活，7 只小鼠的肿瘤在研究结束时消失。不同处理组的动物体重之间没有显着差异。在接受治疗的动物的肝脏和肾脏中未检测到明显的病理改变。结论：与单一疗法相比，使用曲妥珠单抗和 Affibody 介导的基于 PNA 的放射性核素预靶向联合治疗携带 HER2 表达异种移植物的小鼠可显着提高存活率。共同治疗对正常组织没有毒性。