Preparation and Preliminary Biological Evaluation of c-Gluc-Lys(Fe¹⁸FNOTA)-TOCA

Somatostatin analogues can specificially bind with somatostatin receptor (SSTR) which is usually over-expressed on many tumor cells. So it may have important significance to use ¹⁸F labeled somatostatin analogues as the tumor probes for the diagnosis, the clinical staging and evaluation of therapeutic effect of SSTR positive tumor. In order to explore a novel PET probe for diagnosis of SSTR positive tumors, the c-Gluc-Lys(Fe¹⁸FNOTA)-TOCA was radio-synthesized fast and efficiently using the chelation reaction with Fe¹⁸F complex and c-Gluc-Lys(NOTA)-TOCA which was a glycosylated somatostatin analogues combined with 1,4,7-triazacyclononane-1,4,7 triacetic acid (NOTA). The labeling efficiency of c-Gluc-Lys(Fe¹⁸FNOTA)-TOCA is 40% and the total synthesis time is 25-30 min. The radiochemical purity is over 95% after HLB column purification. The hydrophily of the probe is high (lg P＝-4.18±0.15), the stability in vitro is poor. Biodistribution studies in normal mice show that c-Gluc-Lys(Fe¹⁸FNOTA)-TOCA is excluded by kidneys, the uptake in liver is low, the uptake in SSTR expressed pancreas is high, the background of blood and muscle are low, the uptake in bone is high. These preliminary results provide some experimental basis for further study of ¹⁸F metal complex labeled somatostatin analogues as the tumor probes for the diagnosis of SSTR-positive tumor.