In-house automated synthesis of L-[11C]Glutamine with the use of a siemens H11CN Box.

2156 Objectives: Glutamine is a readily available nutrient used for energy in both normal and tumor cells [1]. L-[11C]glutamine takes advantage of various tumor metabolic pathways for when [18F]FDG is limited. There is therefore a need in the PET community for an automated synthesis of L-[11C]glutamine. We have developed a method for the routine automated production of L-[11C]glutamine. Methods: L-[11C]glutamine was prepared with the use of an in-house Glutamine Module attached to a Siemens H11CN(Cyanide)Box. [11C]CO2, produced from a Siemens Eclipse HP Cyclotron, is converted into H11CN with the use of nickel/platinum catalysts. Radioactive cyanide gas is trapped in reaction vessel 1 with the use of 18-crown-6/cesium hydrogen carbonate base in N,N-dimethylformamide. The glutamine precursor, (s)-tert-butyl 2-((tert-butoxycarbonyl)amine)-4- iodobutanoat, is then added and heated to 90 oC for 8 min. Trapping on a pre-conditioned t-C18 plus cartridge is achieved with the use of HPLC grade water. The radiolabeled intermediate is then released into reaction vessel 2 by way of acetonitrile. This is then dried at 120 oC over a stream of argon. This process is repeated with the use of acetonitrile. The dried intermediate is then deprotected with the use of (4:1) trifluoroacetic acid:sulfuric acid and heated to 90 oC for 5 min. Quenching with sterile water for injection and slowly passing through 5.0 g of Ag11 A-8 resin provided L-[11C]glutamine. Chemical identity, purity and L:D isomeric ratio of the labeled radioligand was determined by reversed-phase HPLC. Quality control (QC) conditions were tested and passed for each production of L-[11C]glutamine; these tests include radionuclidic purity, pH, chemical identity, ratio of L/D-glutamine isomer, excipients, half-life and sterility. An in vitro cell uptake assay was performed using a glioblastoma (GBM) cell line to evaluate the reactivity and specificity of L-[11C]glutamine. Excess L-glutamine was used to block control samples. SOPs and Batch Record were created prior to validation runs. Results: L-[11C]glutamine was successfully produced operating our automated in-house module connected to a Siemens H11CN Box. Routine production provided 17.5 - 32.5 mCi (n = 6) at end-of-synthesis (EOS), starting with approximately 1,400 mCi of [11C]CO2. The average radiochemical purity = 95 ± 1.6% with an average enantiomeric excess (e.e.) = 96 ± 1.8 % and a pH value ranging from 7.5 to 8.0. Total synthesis time ranges from 74 to 82 min. In in vitro assay, L-[11C]glutamine was taken up by GBM cells and was inhibited by ~65% when blocked with excess cold L-glutamine, indicating binding specificity. Conclusions: A method for the automated production of L-[11C]glutamine was achieved with the use of an in-house module attached to a Siemens H11CN module. Specificity and reactivity of the produced L-[11C]glutamine was validated in vitro using a glioblastoma cell line. This provides a platform for consistent-routine production of L-[11C]glutamine which can be used as a potential PET imaging agent. References: [1] L. Zhu, et. al. J. Nucl. Med. 2017, 58, 533-537.