Abstract
1187
Objectives Somaotstatin receptors are over expressed on neuroendocrine tumors (NET). Ga-68 DOTATATE (t1/2-68 min;energy-1.92 MeV) is a molecular probe for PET imaging of NETs. Ga-68 directly bound to a chelating agent DOTA (pH 4-4.5; 95°C) attached to peptide. Quality control parameters of Ga-68 DOTATATE were studied.
Methods A manual synthesis module fitted with electric heater was used. Peptide in acetate buffer was transferred to the preheated reactor (95°C). Ga-68 from generator was eluted with 0.05N HCl directly to reactor. The solution was heated for 10 min & then transferred to the waste vial after passing through the C-18 cartridge, preconditioned with ethanol and water. The labeled peptide from C-18 cartridge was eluted with 30% ethanol & delivered to a product vial after passing through a 0.22μ filter. The total synthesis time was 15 min. pH of each batch and waste was checked. Radiochemical purity was checked with ITLC using Na-citrate as mobile phase. Twenty five samples (n=25) of Ga-68 DOTATATE were randomly selected for other quality control parameters. The half-life (t1/2) was determined by recording radioactivity after every 10 minute & multichannel analyzer. The chemical purity was checked by gas chromatography using ethanol (4000 ppm) as a standard. All the samples were incubated in RCM broth at 37°C for 7 days to determine the sterility. Bacterial endotoxin test (BET) was performed by LAL kit.
Results The t1/2 of Ga-68 in Ga-68 DOTATATE & waste samples were 68 minutes. The radiochemical purity of Ga-68 DOTATATE samples were 100% as single peak was observed with Rf ~ 0.243. pH of all samples was between 6 & 6.5. Spectra of Ga-68 DOTATATE did not show Ge-68 peak. The concentration of ethanol in Ga-68 DOTATATE was 242±52 ppm. The samples did not demonstrate formation of gel in BET thus indicating that the samples were free from pyrogens. The samples were sterile & no growth was observed after seven days incubation in RCM broth.
Conclusions Manual synthesis module is cost effective. Ga-68 DOTATATE synthesis is quick and safe for patients’ use.