甲基六聚乙二醇衍生物修饰胸腺五肽的合成及其体外稳定性

Synthesis and in vitro stability of thymopentin modified by methyl hexaethylene glycol derivatives

目的为了解决胸腺五肽(thymopentin,TP5)易被降解,半衰期短的缺点,设计并合成了具有普遍适用性的新型单分散小分子聚乙二醇修饰剂,并探索其定点修饰TP5主链N端和赖氨酸(Lys)侧链氨基的新方法及稳定性评价。方法以六聚乙二醇单甲醚为起始原料经过两步反应得到修饰剂甲基六聚乙二醇脂肪酸。分别用于在固相合成中直接修饰到TP5的主链N端,和对TP5侧链Lys的定点修饰。对修饰肽进行了在兔血清中的稳定性测试,并对不同修饰位点和修饰剂中脂肪酸长度对修饰肽降解速度的影响进行了分析和讨论。结果与未修饰的TP5相比,修饰肽在血清中的原型保留率均显著上升,稳定性大幅度提高。修饰主链N端的TP5的稳定性高于修饰Lys侧链的TP5,增加脂肪酸长度会使降解速度加快。结论采用单分散小分子聚乙二醇修饰的方法可以提高胸腺五肽的稳定性,因此采用聚乙二醇修饰技术可能开发TP5的长效注射剂,以拓宽其临床应用。

Objective To overcome the disadvantages of thymopentin（ TP5 ）which is easily degraded in vivo, a series of novel micromolecular mono-dispersed PEG derivatives were designed and synthesized to modify TP5 on N-terminal or lysine residue, and the in vitro stability of the PEGylated peptides in rabbit serum were tested. Methods Methyl PEG acetic acid and methyl PEG hexanoic acid were synthesized taking methyl hexaethylene glycol as starting material. They were attached to the N-terminal or lysine residue of TP5 by solid phase peptide synthesis. The in vitro stability of the PEGylated peptides was determined in rabbit serum. Results The stabilities of modified TP5 by a series of PEG derivatives were improved. Modification of TP5 on N-terminal was more effective than that on side chain. Methyl PEG acetic acid conjugated TP5 were more stable than methyl PEG hexanoic acid. Conclusions PEGylation is an efficient method to improve the stability of TP5, thus it could be used to develop novel long-acting preparation of TP5 to expand its clinical application.