A Nanobody–Bioorthogonal Catalyst Conjugate Triggers Spatially Confined Prodrug Activation for Combinational Chemo-immunotherapy

Checkpoint inhibitors have been used with chemotherapy to improve antitumor efficacy. However, overcoming the immunosuppressive effect of chemotherapeutics remains a challenge. We report a nanobody–catalyst conjugate Ru-PD-L1 by fusing a ruthenium catalyst to an anti-PD-L1 nanobody. After administration of Ru-PD-L1 and a doxorubicin (DOX) prodrug, Ru-PD-L1 disrupts the PD-L1/PD-1 interaction and catalyzes the uncaging of the DOX prodrug. The spatially confined release of DOX reduces its systemic toxicity and leads to immunogenic cell death (ICD). The induced ICD triggers antitumor immune responses, which are further amplified by PD-L1 blockade to elicit synergistic chemo-immunotherapy, substantially increasing the number of tumor-infiltrating T-cells by 49.7% compared with the controls, thereby exhibiting high antitumor activity and low cytotoxicity in murine models. The combinational treatment could inhibit the growth of mice tumors by 67.7% compared to the control group. This combinational approach circumvents the negative immunogenic effects of chemotherapeutics and provides a potential chemo-immunotherapy strategy for human cancer treatment.免疫检查点抑制剂（Checkpoint inhibitors）常与化疗联用以提升抗肿瘤疗效，但如何克服化疗药物的免疫抑制作用仍是一项亟待解决的挑战。本研究报道了一种通过将钌催化剂与抗PD-L1纳米抗体融合制备得到的纳米抗体-催化剂偶联物Ru-PD-L1。在给予Ru-PD-L1与阿霉素（doxorubicin，DOX）前药后，Ru-PD-L1可阻断PD-L1/PD-1的相互作用，并催化阿霉素前药的脱笼反应。阿霉素的空间限制性释放可降低其全身毒性，并诱导免疫原性细胞死亡（immunogenic cell death，ICD）。所诱导的免疫原性细胞死亡可触发抗肿瘤免疫应答，而PD-L1阻断可进一步放大该应答，从而实现协同化学免疫治疗：与对照组相比，该疗法可使肿瘤浸润T细胞数量提升49.7%，在小鼠模型中展现出优异的抗肿瘤活性与极低的细胞毒性。与对照组相比，联合治疗可抑制小鼠肿瘤生长达67.7%。该联合疗法可规避化疗药物带来的负面免疫原性效应，为人类癌症治疗提供了一种极具潜力的化学免疫治疗策略。