We use cookies to improve your experience. By continuing to browse this site, you accept our cookie policy.×

Fluorinated molecules in the diagnosis and treatment of neurodegenerative diseases

    Boyenoh Gaye

    Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences in Philadelphia, PA 19104, USA.

    &
    Adeboye Adejare

    † Author for correspondence

    Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences in Philadelphia, PA 19104, USA.

    Published Online:https://doi.org/10.4155/fmc.09.85

    The use of fluorinated molecules as drugs and imaging agents for CNS disorders has been studied extensively over the years. Incorporating a fluorine atom into the structure of a drug changes its physiochemical properties and can thereby lead to much more desirable pharmacokinetic and pharmacodynamic properties. This change can help to facilitate blood–brain barrier permeability, which is a critical matter for drugs intended for CNS activities. Fluorine incorporation into structures of drugs for the treatment of neurodegenerative diseases has been an attractive field for drug discovery. Such incorporation can greatly influence the physicochemical properties, metabolic stability and receptor binding affinity of the resulting molecule. Some studies have shown that when a proton was substituted with fluorine, the binding or inhibitory potency was greatly increased. The fluorine-18 isotope, 18F, is utilized in detection and diagnosis of neurodegenerative diseases, whereas 19F compounds are used in the treatment of these diseases and in MRI. 18F is widely used in PET imaging because it offers the advantage of a longer half-life compared with other radionuclides. It is used for imaging various receptors and transporters that have been linked to neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease and multiple system atrophy. Fluorine plays an important role in the diagnosis and treatment of many CNS diseases, including neurodegenerative disorders. The use of fluorine in the diagnosis and treatment of neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease, will be discussed in this review.

    Papers of special note have been highlighted as: ▪▪ of considerable interest

    Bibliography

    • Bars DL. Fluorine-18 and medical imaging: radiopharmaceuticals for positron emission tomography. J. Fluor. Chem.127,1488–1493 (2006).▪▪ 18F radioactive isotope has a half-life of 109 min, 97% positron decay and emits low positron energy of 635 keV. Owing to these advantages, 18F is the radionuclide of choice in PET.
    • Hagmann WK. The many roles for fluorine in medicinal chemistry. J. Med. Chem.51,4359–4369 (2008).▪▪ Fluorine substitution into structures of drug candidates greatly improves the desired physicochemical properties.
    • Shah P, Westwell AD. The role of fluorine in medicinal chemistry. J. Enzyme Inhib. Med. Chem.22,527–540 (2007).▪▪ Due to the small size, high electronegativity, greater C-F bond stability and increased lipophilicity, fluorine is the atom of choice for altering the physicochemical properties of drugs.
    • Adejare A, Shen J, Ogunbadeniyi AM. Halogens halt aromatic group migration in Baeyer–Billiger oxidation. J. Fluor. Chem.105,107–109 (2000).
    • Adejare A, Gusovsky F, Padgett W, Creveling JW, Daly KL. Syntheses and adrenergic activities of ring-fluorinated epinephrines. J. Med. Chem.31,1972–1977 (1988).
    • Adejare A, Nie JY, Hebel D et al. Effect of fluorine substitution on the adrenergic properties of 3-(tert-butylamino)-1-(3,4-dihydroxyphenoxy)-2-propanol. J. Med. Chem.34,1063–1068 (1991).
    • Adejare A, Sciberras SS. Synthesis and β-adrenergic activities of R-fluoronaphthyloxypropanolamine. Pharm. Res.14,533–536 (1997).
    • Adeniji A, Adejare A. Chemical and physical characterization of potential new chemical entity. Preclinical Development Handbook: ADME and Biopharmaceutical Properties. Cox S (Ed.). Wiley and Sons Inc, Hoboken, NJ, USA, 221–225 (2008).
    • Bass AS, Kohli JD, Adejare A, Kirk KL, Goldberg LI. Effect of ring fluorination of epinephrine on its cardiovascular adrenoceptor activities. Eur. J. Pharmacol.187,87–95 (1990).
    • 10  Clark MT, Adejare A, Shams G, Feller DR, Miller DD. 5-fluoro- and 8-fluorotrimetoquinol: selective β2-adrenoceptor agonists. J. Med. Chem.30,86–90 (1987).
    • 11  El-Gendy AM, Adejare A. Membrane permeability related physicochemical properties of a novel γ-secretase inhibitor. Int. J. Pharm.280,47–55 (2004).
    • 12  Nichols AJ, Hamada A, Adejare A, Miller DD, Patil PN, Ruffolo RR Jr. Effect of aromatic fluorine substitution on the α and β adrenoceptor-mediated effects of 3,4-dihydroxytolazoline in the pithed rat. J. Pharmacol. Exp. Ther.248,671–676 (1989).
    • 13  Ogunbadeniyi AM, Adejare A. Syntheses of fluorinated phenycyclidine analogs. J. Fluor. Chem.114,39–42 (2002).
    • 14  Sun S, Adejare A. Fluorinated molecules as drugs and imaging agents in the CNS. Curr. Top. Med. Chem.6,1457–1464 (2006).▪▪ The use of fluorine in drug discovery and development has been particularly advantageous due to its ability to enhance blood–brain barrier penetration, which is necessary for CNS drugs. 18F is also used in PET studies.
    • 15  Leopoldo M, Lacivita E, De Giorgio Contino M, Berardi F, Perrone R. Design, synthesis and binding affinities of potential positron emission tomography (PET) ligands with optimal lipophilicity for brain imaging of the dopamine D3 receptor. Part II. Bioorg. Med. Chem.17,758–766 (2009).
    • 16  Zeng F, Mun J, Jarkas N et al. Synthesis, radiosynthesis and biological evaluation of carbon-11 and fluorine-18 labeled reboxetine analogues: potential positron emission tomography radioligands for in vivo imaging of the norepinephrine transporter. J. Med. Chem.52,62–73 (2009).
    • 17  Wong DF, Tauscher J, Grunder G. The role of imaging in proof of concept for CNS drug discovery and development. Neuropsychopharmacol. Rev.34,187–203 (2009).▪▪ Neuroimaging (PET and MRI) has played a fundamental role in neuropharmacology. Radiolabeling of a drug that is a CNS agent may provide evidence for proof of concept of the target at which the drug candidate is being tested for receptor occupancy mechanism.
    • 18  Ryu EK, Chen X. Development of Alzheimer’s disease imaging agents for clinical studies. Front. Biosci.13,777–789 (2008).
    • 19  Higuchi M, Iwata N, Matsuba Y, Sato K, Sasamoto K, Saido TC. 19F and 1H MRI detection of amyloid β plaques in vivo. Nat. Neurosci.8,527–533 (2005).
    • 20  Stephenson KA, Chandra R, Zhuang ZP et al. Fluoro-pegylated (FPEG) imaging agents targeting Aβ aggregates. Bioconjug. Chem.18,238–246 (2007).
    • 21  Sonkusare SK, Kaul CL, Ramarao P. Dementia of Alzheimer’s disease and other neurodegenerative disorders – memantine, a new hope. Pharmacol. Res.51,1–17 (2005).
    • 22  Izumi Y, Sawada H, Yamamoto N et al. Novel neuroprotective mechanisms of pramipexole, an anti-Parkinson drug, against endogenous dopamine-mediated excitotoxicity. Eur. J. Pharmacol.557,132–140 (2007).
    • 23  Kirik D, Breysse N, Bjorklund T, Besret L, Hantraye P. Imaging in cell-based therapy for neurodegenerative diseases. Eur. J. Nucl. Med. Mol. Imaging32(Suppl. 2),S417–S434 (2005).
    • 24  Kwon KY, Choi CG, Kim JS, Lee MC, Chung SJ. Diagnostic value of brain MRI and 18F-FDG PET in the differentiation of Parkinsonian-type multiple system atrophy from Parkinson’s disease. Eur. J. Neurol.15,1043–1049 (2008).
    • 25  Bohnen NI, Frey KA. Imaging of cholinergic and monoaminergic neurochemical changes in neurodegenerative disorders. Mol. Imaging Biol.9,243–257 (2007).
    • 26  Paulsen JS. Functional imaging in Huntington’s disease. Exp. Neurol.216,272–277 (2009).
    • 27  Kirk KL. Fluorine in medicinal chemistry: Recent therapeutic applications of fluorinated small molecules. J. Fluor. Chem.127,1013–1029 (2006).▪▪ Advantages of using fluorinated drugs for the treatment of CNS and cardiovascular diseases, as well as obesity, are discussed. Many fluorinated compounds are also used as antibacterial and antifungal agents.
    • 28  Lund BW, Knapp AE, Piu F et al. Design, synthesis and structure-activity analysis of isoform-selective retinoic acid receptor β ligands. J. Med. Chem.52,1540–1545 (2009).
    • 29  Podichetty AK, Faust A, Kopka K et al. Fluorinated isatin derivatives. Part 1: synthesis of new N-substituted (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatins as potent caspase-3 and -7 inhibitors. Bioorg. Med. Chem.17,2680–2688 (2009).
    • 30  Saitoh M, Kunitomo J, Kimura E et al. Design, synthesis and structure-activity relationships of 1,3,4-oxadiazole derivatives as novel inhibitors of glycogen synthase kinase-3β. Bioorg. Med. Chem.17,2017–2029 (2009).
    • 31  Klunk WE, Mathis CA. The future of amyloid-β imaging: a tale of radionuclides and tracer proliferation. Curr. Opin. Neurol.21,683–687 (2008).
    • 32  Serdons K, Terwinghe C, Vermaelen P et al. Synthesis and evaluation of (18)F-labeled 2-phenylbenzothiazoles as positron emission tomography imaging agents for amyloid plaques in Alzheimer’s disease. J. Med. Chem.52,1428–1437 (2009).
    • 33  Zeng F, Southerland JA, Voll RJ et al. Synthesis and evaluation of two 18F-labeled imidazo[1,2-a]pyridine analogues as potential agents for imaging β-amyloid in Alzheimer’s disease. Bioorg. Med. Chem. Lett.16,3015–3018 (2006).
    • 34  Lee JH, Byeon SR, Kim Y et al. [18F]-labeled isoindol-1-one and isoindol-1,3-dione derivatives as potential PET imaging agents for detection of β-amyloid fibrils. Bioorg. Med. Chem. Lett.18,5701–5704 (2008).
    • 35  Qu W, Choi SR, Hou C et al. Synthesis and evaluation of indolinyl- and indolylphenylacetylenes as PET imaging agents for β-amyloid plaques. Bioorg. Med. Chem. Lett.18,4823–4827 (2008).
    • 36  Zhang W, Oya S, Kung MP, Hou C, Maier DL, Kung HF. F-18 Polyethyleneglycol stilbenes as PET imaging agents targeting Aβ aggregates in the brain. Nucl. Med. Biol.32,799–809 (2005).
    • 37  Ono M, Watanabe R, Kawashima H et al.18F-labeled flavones for in vivo imaging of β-amyloid plaques in Alzheimer’s brains. Bioorg. Med. Chem.17,2069–2076 (2009).
    • 38  Chandra R, Oya S, Kung MP, Hou C, Jin LW, Kung HF. New diphenylacetylenes as probes for positron emission tomographic imaging of amyloid plaques. J. Med. Chem.50,2415–2423 (2007).
    • 39  Li L, Sengupta A, Haque N, Grundke-Iqbal I, Iqbal K. Memantine inhibits and reverses the Alzheimer type abnormal hyperphosphorylation of tau and associated neurodegeneration. FEBS Lett.566,261–269 (2004).
    • 40  Ametamey SM, Bruehlmeier M, Kneifel S et al. PET studies of 18F-memantine in healthy volunteers. Nucl. Med. Biol.29,227–231 (2002).
    • 41  Elsinga PH, Hatano K, Ishiwata K. PET tracers for imaging of the dopaminergic system. Curr. Med. Chem.13,2139–2153 (2006).
    • 42  Hocke C, Prante O, Lober S, Hubner H, Gmeiner P, Kuwert T. Synthesis and evaluation of 18F-labeled dopamine D3 receptor ligands as potential PET imaging agents. Bioorg. Med. Chem. Lett.15,4819–4823 (2005).
    • 43  Nanni C, Fanti S, Rubello D. 18F-DOPA PET and PET/CT. J. Nucl. Med.48,1577–1579 (2007).
    • 44  Wuest F, Berndt M, Strobel K et al. Synthesis and radiopharmacological characterization of 2β-carbo-2´-[18F]fluoroethoxy-3β-(4-bromo-phenyl)tropane ([18F]MCL-322) as a PET radiotracer for imaging the dopamine transporter (DAT). Bioorg. Med. Chem.15,4511–4519 (2007).
    • 45  Chitneni SK, Garreau L, Cleynhens B et al. Improved synthesis and metabolic stability analysis of the dopamine transporter ligand [(18)F]FECT. Nucl. Med. Biol.35,75–82 (2008).
    • 46  Easwaramoorthy B, Pichika R, Collins D, Potkin SG, Leslie FM, Mukherjee J. Effect of acetylcholinesterase inhibitors on the binding of nicotinic a4b2 receptor P radiotracer ET, (18)F-nifene: a measure of acetylcholine competition. Synapse61,29–36 (2007).
    • 47  Kozikowski AP, Chellappan SK, Henderson D et al. Acetylenic pyridines for use in PET imaging of nicotinic receptors. ChemMedChem2,54–57 (2007).
    • 48  Pomper MG, Phillips E, Fan H et al. Synthesis and biodistribution of radiolabeled α 7 nicotinic acetylcholine receptor ligands. J. Nucl. Med.46,326–334 (2005).
    • 49  Roger G, Saba W, Valette H et al. Synthesis and radiosynthesis of [18F]FPhEP, a novel α4β2-selective, epibatidine-based antagonist for PET imaging of nicotinic acetylcholine receptors. Bioorg. Med. Chem.14,3848–3858 (2006).
    • 50  Deuther-Conrad W, Fischer S, Hiller A et al. Molecular imaging of α7 nicotinic acetylcholine receptors: design and evaluation of the potent radioligand [18F]NS10743. Eur. J. Nucl. Med. Mol. Imaging36,791–800 (2009).
    • 51  Huang Y, Zhu Z, Xiao Y, Laruelle M. Epibatidine analogues as selective ligands for the αxβ2-containing subtypes of nicotinic acetylcholine receptors. Bioorg. Med. Chem. Lett.15,4385–4388 (2005).
    • 52  Takano A, Gulyas B, Varrone A et al. Imaging the norepinephrine transporter with positron emission tomography: initial human studies with (S,S)-[18F]FMeNER-D2. Eur. J. Nucl. Med. Mol. Imaging35,153–157 (2008).
    • 53  Zeng F, Jarkas N, Stehouwer JS et al. Synthesis, in vitro characterization and radiolabeling of reboxetine analogs as potential PET radioligands for imaging the norepinephrine transporter. Bioorg. Med. Chem.16,783–793 (2008).
    • 54  Fookes CJ, Pham TQ, Mattner F et al. Synthesis and biological evaluation of substituted [18F]imidazo[1,2-a]pyridines and [18F]pyrazolo[1,5-α]pyrimidines for the study of the peripheral benzodiazepine receptor using positron emission tomography. J. Med. Chem.51,3700–3712 (2008).
    • 55  Yanamoto K, Kumata K, Yamasaki T et al. [18F]FEAC and [18F]FEDAC: lwo novel positron emission tomography ligands for peripheral-type benzodiazepine receptor in the brain. Bioorg. Med. Chem. Lett.19,1707–1710 (2009).
    • 56  Yu W, Wang E, Voll RJ, Miller AH, Goodman MM. Synthesis, fluorine-18 radiolabeling and in vitro characterization of 1-iodophenyl-N-methyl-N-fluoroalkyl-3-isoquinoline carboxamide derivatives as potential PET radioligands for imaging peripheral benzodiazepine receptor. Bioorg. Med. Chem.16,6145–6155 (2008).
    • 57  Zhang MR, Maeda J, Ogawa M et al. Development of a new radioligand N-(5-fluoro-2-phenoxyphenyl)-N-(2-[18F]fluoroethyl-5-methoxybenzyl)acetamide, for PET imaging of peripheral benzodiazepine receptor in primate brain. J. Med. Chem.47,2228–2235 (2004).
    • 58  Serdons K, Verduyckt T, Vanderghinste D et al. Synthesis of 18F-labelled 2-(4´-fluorophenyl)-1,3-benzothiazole and evaluation as amyloid imaging agent in comparison with [11C]PIB. Bioorg. Med. Chem. Lett.19,602–605 (2009).
    • 59  Goswami R, Ponde DE, Kung MP, Hou C, Kilbourn MR, Kung HF. Fluoroalkyl derivatives of dihydrotetrabenazine as positron emission tomography imaging agents targeting vesicular monoamine transporters. Nucl. Med. Biol.33,685–694 (2006).
    • 60  Kung MP, Hou C, Goswami R, Ponde DE, Kilbourn MR, Kung HF. Characterization of optically resolved 9-fluoropropyl-dihydrotetrabenazine as a potential PET imaging agent targeting vesicular monoamine transporters. Nucl. Med. Biol.34,239–246 (2007).
    • 61  Wilson AA, Garcia A, Parkes J et al. Radiosynthesis and initial evaluation of [18F]-FEPPA for PET imaging of peripheral benzodiazepine receptors. Nucl. Med. Biol.35,305–314 (2008).
    • 62  Reid DG, Murphy PS. Fluorine magnetic resonance in vivo: a powerful tool in the study of drug distribution and metabolism. Drug Discov. Today13,473–480 (2008).
    • 63  Flaherty DP, Walsh SM, Kiyota T, Dong Y, Ikezu T, Vennerstrom JL. Polyfluorinated bis-styrylbenzene β-amyloid plaque binding ligands. J. Med. Chem.50,4986–4992 (2007).
    • 64  Amatsubo T, Morikawa S, Inubushi T et al. Trifluoromethoxy-benzylated ligands improve amyloid detection in the brain using 19F magnetic resonance imaging. Neurosci. Res.63,76–81 (2009).