Dataset Information

Radiosynthesis of the anticancer nucleoside analogue Trifluridine using an automated 18F-trifluoromethylation procedure.

ABSTRACT: Trifluoromethyl groups are widespread in medicinal chemistry, yet there are limited 18F-radiochemistry techniques available for the production of the complementary PET agents. Herein, we report the first radiosynthesis of the anticancer nucleoside analogue trifluridine, using a fully automated, clinically-applicable 18F-trifluoromethylation procedure. [18F]Trifluridine was obtained after two synthetic steps in <2 hours. The isolated radiochemical yield was 3% ± 0.44 (n = 5), with a radiochemical purity >99%, and a molar activity of 0.4 GBq ?mol-1 ± 0.05. Biodistribution and PET-imaging data using HCT116 tumour-bearing mice showed a 2.5 %ID g-1 tumour uptake of [18F]trifluridine at 60 minutes post-injection, with bone uptake becoming a prominent feature thereafter. In vivo metabolite analysis of selected tissues revealed the presence of the original radiolabelled nucleoside analogue, together with deglycosylated and phosphorylated [18F]trifluridine as the main metabolites. Our findings suggest a potential role for [18F]trifluridine as a PET radiotracer for elucidation of drug mechanism of action.

SUBMITTER: King A

PROVIDER: S-EPMC5944245 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Radiosynthesis of the anticancer nucleoside analogue Trifluridine using an automated <sup>18</sup>F-trifluoromethylation procedure.

King Alice A Doepner Andreas A Turton David D Ciobota Daniela M DM Da Pieve Chiara C Wong Te Fong Anne-Christine AC Kramer-Marek Gabriela G Chung Yuen-Li YL Smith Graham G

Organic & biomolecular chemistry 20180401 16

Trifluoromethyl groups are widespread in medicinal chemistry, yet there are limited 18F-radiochemistry techniques available for the production of the complementary PET agents. Herein, we report the first radiosynthesis of the anticancer nucleoside analogue trifluridine, using a fully automated, clinically-applicable 18F-trifluoromethylation procedure. [18F]Trifluridine was obtained after two synthetic steps in <2 hours. The isolated radiochemical yield was 3% ± 0.44 (n = 5), with a radiochemical ...[more]

PMID: 29629716

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Project description:Access to diverse PET tracers for preclinical and clinical research remains a major obstacle to research in cancer and other disease research. The prohibitive cost and limited availability of tracers could be alleviated by microfluidic radiosynthesis technologies combined with a high-yield microscale radiosynthetic method. In this report, we demonstrate the multistep synthesis of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) with high yield on an electrowetting-on-dielectric (EWOD) microfluidic radiosynthesizer, previously developed in our group. We have identified and established several parameters that are most critical in the microscale radiosynthesis, such as the reaction time, reagent concentration, and molar ratios, to successfully synthesize (18)F-FLT in this compact platform.(18)F-FLT was synthesized from the 3-N-Boc-1-[5-O-(4,4'-dimethoxytrityl)-3-O-nosyl-2-deoxy-?-D-lyxofuranosyl] thymine precursor on the EWOD chip starting from the first solvent exchange and (18)F-fluoride ion activation step to the final deprotection step. The fluorination reaction was performed in a mixture of thexyl alcohol and dimethyl sulfoxide. The crude product after deprotection was collected from the chip and purified on a custom-made solid-phase extraction cartridge and subjected to quality control testing. The purified (18)F-FLT was suitable for small-animal PET studies in multiple nude mice xenografted with the A431 carcinoma cell line.(18)F-FLT was successfully synthesized on the EWOD microdevice coupled with an off-chip solid-phase extraction purification with a decayed-corrected radiochemical yield of 63% ± 5% (n = 5) and passed all of the quality control tests required by the U.S. Pharmacopeia for radiotracers to be injected into humans. We have successfully demonstrated the synthesis of several batches of (18)F-FLT on EWOD, starting with approximately 333 MBq of radioactivity and obtained up to 52 MBq (non-decay-corrected) of (18)F-FLT on cartridge purification. The specific activity of 2 representative preparations of (18)F-FLT synthesized on the EWOD chip were measured to be 1,800 and 2,400 GBq/?mol.The EWOD microchip and optimized synthesis method in combination represent an effective platform for synthesizing (18)F-FLT with high yield and of good quality for imaging. This compact platform, with configurable synthesis steps, could potentially form the basis of a stand-alone system that decouples PET probe production from the cyclotron and specialized radiochemistry facilities and increases diversity and flexibility in probe production.

Project description:INTRODUCTION:Our previous work demonstrated that the 99mTc renal tracer, 99mTc(CO)3(FEDA) (99mTc-1), has a rapid clearance comparable in rats to that of 131I-OIH, the radioactive gold standard for the measurement of effective renal plasma flow. The uncharged fluoroethyl pendant group of 99mTc-1 provides a route to the synthesis of a structurally analogous rhenium-tricarbonyl 18F renal imaging agent, Re(CO)3([18F]FEDA) (18F-1). Our goal was to develop an efficient one-step method for the preparation of 18F-1 and to compare its pharmacokinetic properties with those of 131I-OIH in rats. METHODS:18F-1 was prepared by the nucleophilic 18F-fluorination of its tosyl precursor. The labeled compound was isolated by HPLC and subsequently evaluated in Sprague-Dawley rats using 131I-OIH as an internal control and by dynamic PET/CT imaging. Plasma protein binding (PPB) and erythrocyte uptake (RCB) were determined and the urine was analyzed for metabolites. RESULTS:18F-1 was efficiently prepared as a single species with high radiochemical purity (>99%) and it displayed high radiochemical stability in vitro and in vivo. PPB was 87% and RCB was 21%. Biodistribution studies confirmed rapid renal extraction and high specificity for renal excretion, comparable to that of 131I-OIH, with minimal hepatic/gastrointestinal elimination. The activity in the urine, as a percentage of 131I-OIH, was 92% and 95% at 10 and 60 min, respectively. All other organs (heart, spleen, lungs) showed a negligible tracer uptake (<0.4% ID). Dynamic microPET/CT imaging demonstrated rapid transit of 18F-1 through the kidneys and into the bladder; there was no demonstrable activity in bone verifying the absence of free [18F]fluoride. CONCLUSIONS:18F-1 exhibited a high specificity for the kidney, rapid renal excretion comparable to that of 131I-OIH and high in vivo radiochemical stability. Not only is 18F-1 a promising PET renal tracer, but it provides a route to the development of a pair of analogous 18F/99mTc renal imaging agents with almost identical structures and comparable pharmacokinetic properties. These promising in vivo results warrant subsequent evaluation in humans.

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Dataset Information

Radiosynthesis of the anticancer nucleoside analogue Trifluridine using an automated 18F-trifluoromethylation procedure.

Publications

Radiosynthesis of the anticancer nucleoside analogue Trifluridine using an automated <sup>18</sup>F-trifluoromethylation procedure.

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