FAPα靶向标记化合物^(131)I-FAPI-03的合成及初步体内外实验研究

Synthesis and Preliminary Evaluation of FAPα Targeted Tracer ^(131)I-FAPI-03

本研究以4-喹啉基-甘氨基-2-氰基吡咯烷为骨架,对连接基团进行碳链延长及羟基修饰成功合成FAPI衍生物ATE-FAPI-03;通过亲电取代反应实现其^(131)I标记,并对标记化合物^(131)I-FAPI-03的脂水分配比、体外稳定性等进行分析;开展细胞结合、内吞、流出等实验以评价^(131)I-FAPI-03的体外动力学特征;并考察了^(131)I-FAPI-03在荷胶质瘤小鼠体内的分布情况。结果表明:^(131)I-FAPI-03为亲脂性小分子,并具有良好的体外稳定性;与FAPα阳性细胞U87MG孵育10 min时的结合率为(22.00±0.35)%,且随着孵育时间的延长结合率有明显的上升趋势,而与FAPα阴性细胞MCF-7的结合率始终处于较低水平;通过竞争结合实验测得^(131)I-FAPI-03的IC50值为45.5 nM,表明其对FAPα具有较高的亲和力;大部分与U87MG细胞结合的^(131)I-FAPI-03可被细胞内吞,但其在细胞中的滞留能力偏低。^(131)I-FAPI-03在荷胶质瘤小鼠体内具有快速的肿瘤靶向能力:经尾静脉注射5 min后,肿瘤组织对^(131)I-FAPI-03的放射性摄取值为(14.90±3.21)%ID/g,注射2 h后,肿瘤/肌肉的放射性摄取比值达到(43.7±16.7)。上述结果为新型FAPα靶向药物的研发提供了重要的参考。

Using N-(4-quinolinoyl)-Gly-(2-cyanopyrrolidine)as scaffold,we prolonged the linker with serine to obtain a FAPI derivative ATE-FAPI-03,which was subsequently labeled with ^(131)I by electrophilic substitution.Then the in vitro stability,Log P value,binding affinity,targeting properties and biodistribution behavior of ^(131)I-FAPI-03 was evaluated.Results show that ^(131)I-FAPI-03 was lipophilic and stable in vitro,capable of specifically binding to FAPα-positive U87MG cells fast with a major proportion trapped intracellularly.After 10 min of incubation,^(131)I-FAPI-03 showed a specific binding rate of(22.00±0.35)%,and the binding rate increased with the incubation time,to a peak of(37.5±0.83)% at 180 min.However,the FAPα-negative MCF-7 cells exhibited very low uptake of ^(131)I-FAPI-03 at any time point.The IC50 measured by the competition assay indicated significant binding property of ^(131)I-FAPI-03.Biodistribution studies revealed that ^(131)I-FAPI-03 could rapidly accumulate in tumor sites with an uptake of(14.90±3.21)%ID/g at 5 min post injection.At 2 h post injection,^(131)I-FAPI-03 displayed the highest tumor-to-muscle ratio of 43.7±16.7.All above results provided important reference for the development of novel FAPα-targeting tracers.