99mTc通过双功能螯合剂HYNIC间接标记depreotide的临床评价研究

Objectives: Technetium-99m or 99mTc is widely used for labeling peptide in nuclear medicine. Somatostatin and its analogu can inhibit tumor cell growth after biding with its receptor. This research was to study the preclinical effect of a new 99mTc-HYNIC-depreotide, indirect 99mTc labeling of depreotide using HYNIC as bifunctional chelator. Methods: The cyclopeptide , cyclo-(N-Me) Phe-Tyr-D-Trp-Lys-Val-Hcy ] , the linear peptide , and ClCH2-CO.β-Dap-Lys-Cys-Lys. amide ] were synthesised by Fmoc solid-phase synthesis. The cyclopeptide and the linear peptide were linked by liquid-phase synthesis. The product depreotide was isolated and purified by high performance liquid chromatography and was confirmed by mass spectrography. Depreotide was labeled with 99mTc through a direct labeling method, using HYNIC as bifunctional chelator. Used the paper chromatography method to calculate labeling rate, and through the comparative analysis selected the best mark conditions. The new 99mTc-HYNIC-depreotide was tested by high-performance liquid chromatography (HPLC). The internalization and externalization rates of the new 99mTc-HYNIC-depreotide were studied in A549 cells. Furthermore, biodistribution of the radiopeptide was studied in nude mice, bearing tumors from human lung carcinoma cells SPC-A1. Results: The molecular of synthesize depreotide was 1358, and the purity of it was 95.29%. The labeling efficient of 99mTc-HYNIC-depreotide was highest in PH 6.0 and 15°C, about 70.95%±0.84%. The labeling rate of the new 99mTc-HYNIC-depreotide rose to a peak of 20.75 ± 0.48% at 60 min in A549 cells at 37 °C and just slightly decreased later, while it elevated gradually during time course at 4 °C and 25 °C. The internalization rate of the new 99mTc-HYNIC-depreotide at 37 °C increased gradually and reached the peak of 84.4% in 120 min, while the externalization rate of the new 99mTc-HYNIC-depreotide was always less than 20%. In mice bearing the experimental SPC-A1 tumor, the new 99mTc-HYNIC-depreotide demonstrated a high tumor uptake of 4.05 ± 0.04% ID/g at 1.5 hpi and a remained high one of 2.51 ± 0.06% ID/g at 4 hpi. The tumor-to-lung activity concentration ratio (T/Lu) was very high for the new 99mTc-HYNIC-depreotide at all time points. So did the tumor-to-muscle activity (T/Mu) and tumor-to-blood activity concentration ratio (T/Bl). Conclusion: The findings suggested that the new 99mTc-HYNIC-depreotide might be a promising candidate radiopharmaceutical for imaging SSTR positive lung cancer. Keywords: Technetium-99m; HYNIC; depreotide; lung carcinoma;

Preclinical evaluation of a new indirectly labeled 99mTc-depreotide with HYNIC as bifunctional chelator