Abstract View

Purpose/Background

Measuring reactive oxygen and nitrogen species (RONS) in vivo remains challenging to date, thereby limiting the ability to monitor oxidative stress, and consequently, neurodegenerative disease progression effectively.[1] Current PET tracers developed to detect RONS face limitations in biological stability, blood-brain barrier permeability, and RONS specificity.[2, 3] Recently, a manual synthesis method for [¹⁸F]fluoroedaravone ([¹⁸F]FEDV), a PET imaging probe derived from edaravone, a broad-spectrum RONS scavenger approved for treating stroke and ALS, was reported.[4] The goal of this study was to develop and optimize a robust and reproducible automated method for the synthesis of [¹⁸F]FEDV on a commercially available Trasis AllinOne (AiO) radiosynthesizer for routine preclinical and clinical research use.

Methods

The [¹⁸F]FEDV synthesis was adapted from the manual method into a fully automated two-pot, three-step process on the Trasis AiO module. The synthesis scheme and the Trasis layout for [¹⁸F]FEDV synthesis are shown in Figure 1. The first step was the ¹⁸F-fluorination of a 4-((tert-butoxycarbonyl)diazenyl)-N,N,N-trimethylbenzenaminium trifluoromethanesulfonate precursor performed in MeCN. This was followed by cooling to 20°C, dilution with water containing sodium carbonate (pH 9.1), and trapping on a tC18 Sep-Pak cartridge. The intermediate was then eluted into a second reactor using glacial acetic acid for subsequent reduction, hydrolysis and condensation with zinc, conc. HCl, and ethyl acetoacetate, respectively. The crude mixture was diluted with sodium acetate buffer, purified via RP-HPLC and finally reformulated using a HLB light cartridge in ethanolic saline. Optimization included testing a range of precursor masses, ¹⁸F-fluorination times, temperatures, and dilution conditions, as well as SPE and HPLC purification and reformulation parameters. The [¹⁸F]FEDV intermediates and final products were analyzed by analytical RP-HPLC methods using non-radioactive standards.

Results

The highest yield of the ¹⁸F-intermediate (>97%) was obtained by reacting 2.5 mg of precursor dissolved in 0.4 mL of MeCN with dry F-18 at 85°C for 1 minute. Reactions conducted at higher temperatures or for longer durations resulted in a decreased yield (<50%). However, the intermediate was found to degrade upon dilution with water. As the compound remained stable on the column during HPLC analysis, we hypothesized that the extent of cooling may be the cause of degradation. We found that cooling to 20°C with basic water (Na₂CO₃, pH 9.0-9.1) and holding for at least 10 minutes resulted in an improved RCY of 70.3%, attributed to stabilization of the diazo intermediate under basic conditions. The intermediate optimization results are shown in Table 1. The semi-prep. RP-HPLC method (<15 min) used for purification yielded good separation of the [¹⁸F]FEDV product (Rt ~ 13.5 min) from unreacted components and impurities (Rt ~ 7-11 min). The optimized process was complete in 105 min and produced [¹⁸F]FEDV with RCY (non-decay corrected) of 6.14% (n=20), > 97% RCP, no detectable chemical impurities, 5.0 pH, and < 10% ethanol.

Conclusion

In summary, an automated method for the radiochemical synthesis of [¹⁸F]FEDV was developed and optimized on a Trasis AiO module and quality control testing results meet criteria for routine clinical research use.

References

1. Dash UC, Bhol NK, Swain SK, Samal RR, Nayak PK, Raina V, et al. Oxidative stress and inflammation in the pathogenesis of neurological disorders: Mechanisms and implications. Acta Pharm Sin B. 2025;15:15–34. doi:10.1016/j.apsb.2024.10.004.

2. Carroll V, Michel BW, Blecha J, VanBrocklin H, Keshari K, Wilson D, et al. A boronate-caged [(1)(8)F]FLT probe for hydrogen peroxide detection using positron emission tomography. J Am Chem Soc. 2014;136:14742–5. doi:10.1021/ja509198w.

3. Carroll VN, Truillet C, Shen B, Flavell RR, Shao X, Evans MJ, et al. [(11)C]Ascorbic and [(11)C]dehydroascorbic acid, an endogenous redox pair for sensing reactive oxygen species using positron emission tomography. Chem Commun (Camb). 2016;52:4888–90. doi:10.1039/c6cc00895j.

4. Wilde JH, Sun YY, Simpson SR, Hill ER, Fu Z, Bian EJ, et al. A positron emission tomography tracer for the imaging of oxidative stress in the central nervous system. Nat Biomed Eng. 2025;9:716–29. doi:10.1038/s41551-025-01362-3.