A novel molecular imaging probe 99m Tc-HYNIC-FAPI targeting cancer- associated fibroblasts

Abstract Background Fibroblast activation protein (FAP) is higher expressed on cancer-associated fibroblasts (CAFs) in most malignant epithelial neoplasms, which is lower expressed in normal tissues. As a promising small molecular probe, FAP inhibitor (FAPI) shows the specific binding to FAP. This study aimed to explore a novel molecular probe 99mTc-HYNIC-FAPI targeting CAFs. The in vitro characteristics of the probe were also evaluated. Methods The FAPI targeting to FAP was designed, synthesized and conjugated with the chelator 6-hidrazinylnicotinic acid (HYNIC) for radiolabeling with 99mTc. The radiolabeling yield, radiochemical purity and stability were evaluated by Instant thin-layer chromatography (ITLC) and High performance liquid chromatography (HPLC). The binding and migration ability of the probe were assessed using the tumour cell line. Results The radiolabeling yield of 99mTc-HYNIC-FAPI were (97.29 ± 0.46) %. The radiochemical purity was more than 90% and keep stable until 6 h. In vitro experiments, the results indicated that the probe showed binding properties, and inhibited the migration ability of tumor cells. Conclusion The novel 99mTc-HYNIC-FAPI probe was successfully radiosynthesized and exhibited good radiochemical purity, stability and in vitro biding ability to tumor cells. The 99mTc-HYNIC-FAPI will be a promising SPECT/CT imaging probe.