基于PD-L1抑制性多肽的响应性自组装纳米粒用于肿瘤光疗-免疫联合治疗的研究

Metastasis is the most intractable problem in cancer treatment, despite various robust therapies, which is the main cause for 90% of human cancer-related deaths. The checkpoint blockade-based immunotherapy has recently become a promising cancer therapy due to its excellent performance in the drug-resistant and metastatic cases, but the inefficient activation of antitumor immune response, severe side effects and extremely high cost usually hinder its clinical implementation. Phototherapy can ablate primary tumors and further promote the antitumor immune responses. Herein, a tumor microenvironment-responsive therapeutic platform is proposed for cancer treatment by uniting PD-L1 blockade peptide with phototherapy. We synthesized an amphiphilic peptide derivative, PS-DPPA-1, which integrates photosensitizer (PS) with an anti-PD-L1 peptide DPPA-1 via the reactive oxygen species (ROS)- and matrix metalloproteinase-2 (MMP-2)-responsive peptides sequentially, to realize a tumor microenvironment responsive synergistic effect. The PS-DPPA-1 peptide can self-assemble into nanoparticles, significantly increase the loading and delivery efficiency of the photosensitizer and anti-PD-L1 peptide, which finally achieve the synergistic phototherapy and immune therapy. The types of photosensitizers and the length of ROS-responsive sequence will be screened to control the assembly behavior of the PS-DPPA-1. In vivo and in vitro optical properties and the antitumor immune response will be investigated to evaluate the therapeutic effect and further to elucidate the antimetastatic mechanism. In our expectation, this carrier free PS-anti-PD-L1 peptide delivery system can eradicate both primary and metastasis tumors effectively, which may provide novel strategy for solving tumor metastasis clinically and benefit more cancer patients.

免疫检查点阻断疗法是一种极具前景的肿瘤治疗方法。然而，免疫检查点阻断抗体（如PD-L1抗体）存在治疗成本高、免疫应答率低等缺点，严重限制了其临床应用范围。由于光疗在杀伤原位肿瘤的同时，还可以诱导免疫原性细胞死亡，本项目拟将光疗和免疫检查点阻断疗法联用，以增强后者的免疫应答率。利用更为廉价易得的PD-L1抑制性多肽替代PD-L1抗体，构建肿瘤微环境基质金属蛋白酶-2和活性氧分子双重响应的光敏剂-PD-L1抑制性多肽两亲分子。此两亲分子可在溶液中自发组装成纳米粒，显著提高光敏剂和多肽的载药量以及体内递送效率，增强光疗和免疫治疗的疗效，是一类新颖的光疗-免疫联合治疗分子平台。通过研究光敏剂的种类、活性氧响应性序列的长短对组装行为的影响，筛选出最佳两亲分子；评价该两亲分子组装体的体内外光疗活性和抗肿瘤免疫效应，阐明该响应性平台的作用机制。本项目有望为克服肿瘤转移和复发提供新的策略，并降低治疗成本。

基于抑制程序性死亡受体1（PD-1）和程序性死亡配体1（PD-L1）通路的免疫检查点阻断（ICB）疗法已经在癌症免疫治疗中显现出具有良好的治疗效果和应用前景。然而，免疫检查点阻断抗体不仅存在治疗成本高、免疫应答率低等缺点，其潜在的免疫相关不良事件（irAE）风险也对纳米药物中抗PD-L1试剂的精确装载提出了更为严格的要求。在此，我们提出了一种分子工程策略，通过使用更为廉价易得的PD-L1抑制性多肽替代抗PD-L1抗体，将不同的光敏剂和PD-L1抑制性多肽通过化学键键合，以获得肿瘤微环境基质金属蛋白酶（MMP-2）响应的两亲分子；该类两亲分子需要能够自发组装成纳米粒，从而开发出一类可精确控制抗PD-L1试剂含量的纳米药物。通过研究光敏剂的种类对组装行为的影响，筛选出最佳两亲分子为IR780-PD-L1多肽；评价了该两亲分子组装体的体内、外光动力活性和抗肿瘤免疫效应，阐明了该响应性平台的作用机制。研究表明，该纳米药物可以实现PD-L1抑制性多肽的精确和高效负载（高达48.4 wt%），显著提高光敏剂和PD-L1抑制性多肽的体内递送效率，增强光疗和免疫治疗的疗效，是一类高效的光疗-免疫联合治疗分子平台。本项目为提高免疫检查点阻断疗法的治疗效果、拓宽其应用范围提供了一种新颖的平台，有望为克服肿瘤转移和复发提供新的策略。