Synthesis of 11 C-labeled DNA polymerase-β inhibitor 5-methoxyflavone and PET/CT imaging thereof

• Published in: Nuclear medicine and biology 2019-11, Vol.78-79, p.17
• Main Authors: Chen, Zude, Wang, Xiashuang, Xu, Yulong, Wang, Changning
• Format: Article
• Language: English
• ISSN: 1872-9614
• DOI: 10.1016/j.nucmedbio.2019.10.005

"Cell-cycle hypothesis" is emerging in recent years to suggest that aberrant cell cycle re-entry of differentiated neurons leads to a remarkable genetic disequilibrium which is likely to be the primary cause of neuronal apoptosis. DNA polymerase-β is involved in neuronal DNA replication during cell cycle re-entry, thus constituting a promising target for Alzheimer's disease treatment. Recently, 5-methoxyflavone was identified as a candidate molecule endowed with good biological activity and selectivity on the DNA pol-β in multiple in vitro AD models. In vivo assays, especially the brain uptake of 5-methoxyflavone, is need to be evaluated for further development for AD treatment. We report herein the synthesis of C-labeled 5-methoxyflavone, and the evaluation of in vivo properties of 5-[ C]methoxyflavone in rodents. The strategy for synthesis of 5-[ C]methoxyflavone was developed by treating precursor 5-hydroxyflavone with [ C]CH I and KOH in anhydrous DMF. 5-[ C]Methoxyflavone was purified, then evaluated in mice by using PET/CT imaging. The 5-[ C]methoxyflavone was synthesized conveniently in an average decay corrected yield of 22% (n = 3) with a radiochemical purity >99%. The average molar radioactivity of 5-[ C]methoxyflavone was 383 GBq/μmol. The average concentration was 0.107 μg/mL. PET/CT imaging in mice showed 5-[ C]methoxyflavone rapidly passed through the blood-brain barrier with 8.36 ± 0.61%ID/g at 2 min post injection, and the radioactivity accumulation in brain was still noticeable with 2.48 ± 0.59%ID/g at 28 min post injection. The clearance rate was 3.37 (brain /brain ratio). The blood and muscle uptakes were low. The lung displayed high initial uptake and subsequent rapid clearance, while the liver and kidney displayed a relatively slow clearance. Real-time imaging showed that 5-[ C]methoxyflavone accumulated immediately in the heart, then transferred to the liver and intestine, and was not observed in lower digestive tract. 5-[ C]Methoxyflavone was synthesized conveniently in one step. The results of PET/CT imaging in C57BL/6 mice suggested 5-[ C]methoxyflavone possesses appropriate pharmacokinetic properties and favorable brain uptake, thus being proved to be suitable for further development for AD treatment.