新型吲哚生物碱类IDO抑制剂的发现及其在肿瘤免疫治疗中的作用研究

Immune tolerance is a fundamental hallmark of tumor progression, and it is likely that successful immunotherapy will require the implementation of strategies to overcome this barrier through targeting of tolerogenic determinants protecting the tumor. One promising target for pharmacologic intervention in this regard is the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). Activation of IDO in cancer cells facilitates immune tolerance, small molecule inhibitors of IDO can be used to restore the capacity to stimulate an effective antitumor immune response and thus provide a method to treat malignant diseases in combination with chemotherapeutic agents and/or immunotherapy-based strategies. However, most known IDO inhibitors bear poor potency and only a few chemotypes are known to be efficient structural skeleton. Despite great efforts, only few IDO inhibitor has entered clinical trials. Neosartorya species are known to produce indole alkaloids with unique structural feature showing antitumor activities. Neosartorya species have not been extensively investigated for their secondary metabolites, the IDO inhibitory activity of Neosartorya species has been remained unclear. In our preliminary investigation, we found that the methanol extracts of three Neosartorya species fungi showed excellent IDO inhibitory activity, the main active constituents of indole alkaloids were concentrated in the ethyl acetate extracts, and an active indole alkaloid fiscalins B with IC50 of 1.34 μM was obtained. The present study will carry out the activity-guided purification of the effective fraction, the structure-activity analysis and the structure modification to obtain novel and efficient IDO inhibitors. In addition, using Lewis lung cancer (LLC) tumor-bearing mice, the therapeutic effects of the target compounds on tumor growth and immune system, and the potential mechanism will be investigated. The present study will offer new potent scientific basis and lead compound for cancer immunotherapy.

肿瘤细胞分泌免疫抑制因子，促进宿主免疫系统对肿瘤产生免疫耐受，是肿瘤免疫治疗的瓶颈。色氨酸代谢限速酶IDO的过度活化使淋巴T细胞增殖受抑是造成免疫耐受的重要原因，因此IDO抑制剂是潜在的肿瘤免疫治疗药物，但优良的IDO抑制剂匮乏。新萨托菌（Neosartorya）属真菌的次生代谢产物富含吲哚生物碱并具有抗肿瘤活性，大多数菌株的化学成分及生理活性未被系统研究，IDO抑制活性的研究也未见报道。申请者发现三种新萨托菌属菌株具备优良的IDO抑制活性，其活性成分主要是吲哚生物碱并集中在乙酸乙酯提取部位，并获得化合物fiscalins B（IC50 1.34 μM）。本项目拟对有效部位进行系统的化学分离，得到IDO抑制活性显著的化合物，确定结构、进行结构修饰、归纳构效关系；考查其对T细胞增殖及活性的影响；以及对荷瘤小鼠体内肿瘤生长及免疫系统的影响。在细胞、生体水平上研究其肿瘤免疫治疗作用及机制。

肿瘤细胞分泌免疫抑制因子，促进宿主免疫系统对肿瘤产生免疫耐受，是肿瘤免疫治疗的瓶颈。色氨酸代谢限速酶IDO的过度活化使淋巴T细胞增殖受抑是造成免疫耐受的重要原因，因此IDO抑制剂是潜在的肿瘤免疫治疗药物，但优良的IDO抑制剂匮乏。新萨托菌（Neosartorya）属真菌的次生代谢产物富含吲哚生物碱并具有抗肿瘤活性。大多数菌株的化学成分及生理活性未被系统研究，IDO抑制活性的研究也未见报道。申请者发现三种新萨托菌属菌株具备优良的IDO抑制活性，其活性成分主要是吲哚生物碱并集中在乙酸乙酯提取部位，并获得化合物fiscalins B（IC50 1.34 μM）。本项目对有效部位进行系统的化学分离，得到IDO抑制活性显著的化合物，确定结构、进行结构修饰、归纳构效关系；考查其对T细胞增殖及活性的影响；以及对荷瘤小鼠体内肿瘤生长及免疫系统的影响。在细胞、生体水平上研究其肿瘤免疫治疗作用及机制。完成研究目标，解决了三个关键问题：⑴锁定吲哚生物碱类色胺酮为IDO抑制剂的核心母核，为新型IDO抑制剂的研究提供了结构骨架和思路 ⑵建立人源IDO2的酶及细胞水平活性检测体系，进而补充完善了IDO活性检测系统；⑶发现吲哚生物碱类色胺酮具有IDO/IDO2/TDO多重抑制活性。发表SCI论文2篇，均为二区论文；发表中文核心期刊论文3篇；申请中国发明专利2项；先后获得中国药学会科学技术奖（省部级，2017年，三等，排名第一），上海市药学科技奖（2016年，一等，排名第一）；培养博士生1名，硕士研究生3名。