新型蛋白精氨酸甲基转移酶PRMT5抑制剂的设计合成、构效关系及成药性研究

Protein arginine methyltransferase 5 (PRMT5) is an important regulation protein of epigenetics, which directly participates in the regualtion of expressions of a number of oncogenes. It has been thought as one of the most promising anti-cancer drug targets discovered in recent years. Unfortunately, to date, no specific PRMT5 inhibitor has been reported. Therefore, we carried out design and screening studies of PRMT5 inhibitors, and identified four new hit compounds, namely Cmpd-2, Cmpd-8, Cmpd-15, and Cmpd-36. However, their bioactivity and selectivity are poor and need to be further improved. In the proposed project, we shall perform structural optimization design to the four PRMT5 inhibitors by utilizing computer-aided lead optimization methods. The newly designed compounds will be synthesized and tested for their inhibitory activity against PRMT5 and selectivity using the isotope labelled method. Quantitative structure-activity relationship models will also be developed. Based on these models, further structural modifications will be conducted. To the most potent compounds at the enzymatic level, we shall investigate their anti-tumor activities both in vitro and in vivo, as well as the mechanisms of action of anti-tumor. To compounds that show potent in vitro and in vivo anti-tumor activities, further druggability evaluation and optimization will be carried out. It is expected to discover a new PRMT5 inhibitor with high potency and selectivity as well as good druggability to enter preclinical studies.

蛋白精氨酸甲基转移酶PRMT5是一种重要的表观遗传调控蛋白，直接参与多种癌基因的表达调控，被认为是近年来发现的最有前景的新型肿瘤治疗靶标之一。目前国内外尚无针对PRMT5特异性抑制剂的报道。为此，我们前期开展了PRMT5抑制剂的设计和筛选研究，发现了四个具有新型骨架结构的PRMT5抑制剂（即Cmpd-2，Cmpd-8，Cmpd-15和Cmpd-36），但其活性和选择性都有待提高。本项目将在前期研究基础上，应用计算机辅助药物分子设计方法，对上述四个抑制剂进行结构优化设计，合成这些新设计的化合物，采用同位素标记法测试其PRMT5抑制活性和选择性，并通过建立定量构效关系模型进行结构再优化。对酶水平活性高的化合物，研究其体内外抗肿瘤活性及作用机制。对具有良好体内外抗肿瘤活性的化合物进一步开展成药性评价和优化研究。期望发现一种新型高活性和特异性、并具有良好成药性的PRMT5抑制剂进入临床前研究。

PRMT5是一种重要的蛋白质精氨酸甲基转移酶，其主要作用是催化组蛋白或非组蛋白上的精氨酸残基的对称二甲基化。PRMT5被认为是肿瘤等疾病的潜在治疗靶标。目前PRMT5抑制剂报道还非常少。在本研究中，我们首先通过虚拟筛选商业化合物库（包括Specs、Chembridge、Enamine等），发现了6个活性化合物。然后对活性最高的化合物进行了进一步的结构优化，共合成了25个氨基脲衍生物，通过生物活性测试和构效关系研究，最后发现化合物P6的活性和选择性较好。该化合物对PRMT5的IC50为0.57μM，对其他测试的PRMT（PRMT1、PRMT3、PRMT4、PRMT6、PRTM7和PRMT8等精氨酸甲基转移酶）的活性较差。在针对36种不同癌细胞系的细胞活力抑制测试中，该化合物显示了对HT-29（结直肠癌细胞）、DLD-1（结直肠癌细胞）和HepG2（肝癌细胞）等三种细胞株具有良好的抑制活性，而对其它细胞则活性较低或无活性。Western Blot分析表明P6可有效抑制DLD-1细胞中H4R3和H3R8的对称二甲基化。总之，我们通过虚拟筛选和结构优化，获得了一个具有较高活性和选择性的新型PRMT5抑制剂，为针对PRMT5的小分子靶向药物研发提供了一个良好的先导化合物。

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