肿瘤靶向IFNa打破固有和获得性PD-L1/PD-1抗体治疗耐受的策略及机制研究

PD-L1/PD-1(PD) blockade therapy demonstrated impressive results in clinic. However, most patients remain unresponsive to intensive PD therapy despite the presence of tumor-infiltrating lymphocytes. It is a critical task to overcome the tolerance to PD blockade therapy and increase the tumor clearance. We propose that impaired innate sensing might limit the complete activation of tumor-specific T cells after PD-1 blockade. Local delivery of type I interferon (IFN) restored antigen presentation but also upregulated PD-L1, dampening subsequent T-cell activation. Therefore, we armed anti-PD-L1 antibody with IFN (IFN-anti-PD-L1) targeting both PD-L1 blockade and IFN-alpha receptor (IFNAR) activation within tumor microenvironment, to reactivate the T cells and clear the tumor. In this study(1)through constructing cytokines-Ab fusion protein, ant-PD-L1 is used as a carrier to deliver the IFNα specifically to tumor tissues besides its PD signaling blocking function.(2)Targeting IFNαactivate the APC, and together with PD blockade activate tumor-specific T cells. Such a strategy may break the innate and adaptive resistance of tumor immunity to PD blockade. It will provide important guidance to help design the strategies and modalities to increase the response to PD blockade in clinic.

PD-L1/PD-1（PD）抗体阻断疗法在临床上展示了良好的治疗效果。然而大多数病人即使肿瘤内检测到淋巴细胞浸润，却不能对PD阻断产生积极的应答。怎样克服对PD阻断疗法的耐受，促进肿瘤的清除是现在十分迫切的任务。我们提出肿瘤内抗原递呈细胞（APC）活化缺陷可能限制了PD阻断介导的肿瘤特异性T细胞激活。局部注射I型干扰素可以恢复抗原递呈,但同时上调抑制性分子PD-L1。我们计划构建IFN-anti-PD-L1的融合蛋白，同时靶向PD-L1阻断和IFNAR信号通路活化，激活肿瘤特异性T细胞。该研究（1）拟通过构建融合蛋白，以anti-PD-L1作为载体将IFNα运输到肿瘤组织，解决细胞因子的肿瘤靶向问题。（2）利用IFNα活化肿瘤内APC，联合PD阻断充分激活T细胞，打破对PD阻断治疗的耐受。本研究将加深对PD阻断治疗耐受机制的理解，对于提高免疫检查点阻断治疗效果和临床应用具有重要的指导意义。

PD-L1/PD-1（PD）抗体阻断疗法在临床上展示了良好的治疗效果。然而大多数病人即使肿瘤内检测到淋巴细胞浸润，却不能对PD阻断产生积极的应答。我们提出肿瘤内抗原递呈细胞（APC）活化缺陷可能限制了PD阻断介导的肿瘤特异性T细胞激活。局部注射I型干扰素可以恢复抗原递呈,但同时上调抑制性分子PD-L1。我们构建了一种IFN-抗PD-L1抗体（IFN-anti-PD-L1）融合蛋白，其可以同时靶向PD-L1和IFN受体，在实验中观察到，IFN-anti-PD-L1融合蛋白能够在肿瘤组织聚集，显著增加抗原交叉提呈并克服PD-L1介导的免疫抑制。IFN-anti-PD-L1融合蛋白能够同时释放免疫抑制信号和提供共刺激信号来（重新）激活T细胞，可作为新一代的抗PD-L1抗体用于肿瘤疾病的治疗。. 此外，我们对研究内容进行了深入。IFNAR受体广泛表达在外周各个组织，IFNα-anti-PD-L1融合蛋白和外周组织IFNAR的结合会诱导外周毒性。为了降低on-target off-tumor导致的潜在的副效应同时保留有效的抗肿瘤能力，我们进一步构建了突变体 IFN(att)-anti-PD-L1 融合蛋白。突变体 IFN(att)-anti-PD-L1 融合蛋白相较于wt IFN保持较高的抗肿瘤活性。即使高剂量（100μg）治疗也不会导致明显体内毒性，体现在外周血血小板和淋巴细胞不会明显下降，外周血炎症细胞因子无明显升高，小鼠体重无明显变化。因此IFN(att)-anti-PD-L1 融合蛋白实现降低外周毒性的同时，保持较好的抗肿瘤效果，为其进一步临床应用奠定更好的基础。