Optimized production, quality control and biological assessment of 68-Ga-bleomycin as a possible PET imaging agent

Recently, several diagnostic radiopharmaceuticals including bleomycin (BLM) derivatives have been developed. Due to the suitable physical and chemical characteristics of 68Ga as a radionuclide for PET imaging, in this study, optimized production, quality control and preclinical evaluation of 68Ga-BLM as a new PET imaging agent is reported for the first time.

Labeling of BLM with 68Ga was performed using 68Ge/68Ga generator. Experiments were carried out by changing BLM concentration, temperature and pH of the reaction to determine the optimum parameters while the radiochemical purity was checked by radio thin layer chromatography at different times post labeling.  Stability of the radiolabeled complex was studied at room temperature and in human serum at 37 °C. Biodistribution of the complex in BALB/c mice was assessed after intravenous injection and by counting the activity of each organ. Also, images were acquired up to 120 min by dual-head SPECT system.

The purity of this complex >96% (ITLC). At the optimized conditions for preparation of 68Ga-BLM (pH= 3.5-4, temperature = 90 ºC, reaction time = 15 minutes and ligand concentration of 1 mg/ml) , the special activity of the labeled BLM reached to around 17.5 GBq/mmol. Biodistribution study showed significant accumulation of radioactivity in lung and bladder that was different pharmacokinetic compared to free 68Ga cation.

Results show that 68Ga-BLM can be prepared in high radiochemical purity and high special activity only in 15 minutes and totally can be considered as a high potential agent for PET imaging.