Advances in the automated synthesis of 6-[18F]Fluoro-L-DOPA

Manufacturing 6-[18F]Fluoro-L-DOPA via Flow Chemistry-Enhanced Photoredox Radiofluorination

In this study, we introduce a practical methodology for the synthesis of PET probes by seamlessly combining flow chemistry with photoredox radiofluorination. The clinical PET tracer 6-[18F]FDOPA was smoothly prepared in a 24.3% non-decay-corrected yield with over 99.0% radiochemical purity (RCP) and enantiomeric excess (ee), notably by a simple cartridge-based purification. The flow chemistry-enhanced photolabeling method supplies an efficient and versatile solution for the synthesis of 6-[18F]FDOPA and for more PET tracer development.

Imaging of cardiac sympathetic dysfunction with 18F-FDOPA PET/CT in patients with heart failure: a pilot study

BACKGROUND

Routine use of cardiac sympathetic imaging in HF has been limited by the lower availability/sensitivity of radiotracers. This study was aimed to assess the feasibility of 18F-FDOPA (commonly available PET-radiotracer) in assessment of cardiac autonomic dysfunction.

METHODS

Twenty-four controls (46.5 ± 11.1 years, 16men) and 24 patients (43.5 ± 11.0 years, 18men) with diagnosed HF (Framingham-Criteria) underwent cardiac-PET/CT. Region(s) Of Interest were drawn over entire left ventricular myocardium (LV), individual walls, and mediastinum (M). Coefficient of Variation (CV) was calculated from individual wall counts.

RESULTS

HF patients had significantly lower myocardial 18F-FDOPA uptake (P < .001, independent t test) than controls [32.4% ± 9.5% global reduction; highest in apex (39.9% ± 7.0%)]. A cut-off of LV/M ≤ 1.68 could differentiate patients from controls with sensitivity and specificity of 100% and 95.8%, respectively. LV/M correlated positively with EF (Pearson coefficient = 0.460, P .031). During follow-up, 3 patients were lost to follow-up, 4 died (survival-20.5 ± 4 months), 2 worsened, and 15 remained stable/showed mild improvement. Patients who worsened/died during follow-up had higher CV than those with stable/improving symptoms [0.16 ± 0.05 vs 0.11 ± 0.05, P value .069 (independent t test); Cox regression P = .084].

CONCLUSION

Myocardial 18F-FDOPA uptake in patients with HF is significantly reduced. Higher reduction is seen in those with lower EF. CV, a maker of regional heterogeneity, is a potential prognostic marker.

HPLC-free and cassette-based nucleophilic production of [18F]FDOPA for clinical use

Radiotracer 3,4-dihydroxy-6-[¹⁸F]fluoro-L-phenylalanine (L-6-[¹⁸F]fluorodopa or [¹⁸F]FDOPA) is widely used for PET imaging of dopamine metabolism in several diseases including Parkinson's Disease, brain tumor, neuroendocrine tumors, and focal hyperinsulinism of infancy. In 2019, [¹⁸F]FDOPA was approved by US FDA for detection of dopaminergic nerve terminals in the striatum of adult patients with suspected Parkinsonian Syndromes. A convenient and reliable method is desired for fully automated production of [¹⁸F]FDOPA under cGMP compliance to meet the increasing clinical need. In this study, we reported a cassette-based automated production of [¹⁸F]FDOPA using a GE Fastlab 2 module and the quality control (QC) under fully cGMP compliant environment. Briefly, automated radiosynthesis of [¹⁸F]FDOPA was processed via nucleophilic radio-fluorination using FDOPA Fastlab cassette and solid phase extraction (SPE) purification. The QC tests of [¹⁸F]FDOPA, including appearance, pH, half-life, radiochemical purity and identity, enantiomeric purity, chemical impurities, molecular activity, radioactive concentration, filter integrity, endotoxin, and sterility, were conducted at the end of synthesis (EOS) and 8 h after EOS during the validation runs. Three consecutive productions of [¹⁸F]FDOPA were reliably achieved with desired radiochemical yield and high radiochemical/enantiomeric purities and molar activity. The uncorrected radiochemical yields of [¹⁸F]FDOPA were 9.3-9.8% with a total synthesis time of ~140 min. Both radiochemical and enantiomeric purities of [¹⁸F]FDOPA were >99.9% and the molar activities were 2.1-3.9 Ci/μmole at EOS. The full QC results at EOS and 8 h after EOS showed that the produced [¹⁸F]FDOPA met all release criteria for clinical use within 8 hours of expiration time. Three consecutive validation runs and QC results demonstrated the efficacy of cassette-based production of [¹⁸F]FDOPA for routine clinical use.