Abstract
2′-Deoxy-2′-[18F]fluoro-5-ethyl-1-β-d-arabinofuranosyluracil ([18F]FEAU) is a promising radiolabeled nucleoside designed to monitor Herpes Simplex Virus Type 1 thymidine kinase (HSV1-tk) reporter gene expression with positron emission tomography (PET). However, the challenging radiosynthesis creates problems for being able to provide [18F]FEAU routinely. We have developed a routine method using a commercial GE TRACERlab FX-FN radiosynthesis module with customized equipment to provide [18F]FEAU. All radiochemical yields are decay corrected to end-of-bombardment and reported as means ± SD. Radiofluorination (33 ± 8%; n = 4), bromination (85 ± 8%; n = 4), coupling reaction (83 ± 6%; n = 4), base hydrolysis steps, and subsequent high-performance liquid chromatography purification afforded purified [18F]FEAU β-anomer in 5 ± 1% overall yield (n = 3 runs) after ~5.5 h and a β/α-anomer ratio of 7.4. Radiochemical/chemical purities and specific activity exceeded 99% and 1.3 Ci/μmol (48 GBq/μmol), respectively. In cell culture, [18F]FEAU showed significantly (P < 0.05) higher accumulation in C6 cells expressing HSV1-tk/sr39tk as compared to wild-type C6 cells. Furthermore, [18F]FEAU showed slightly higher accumulation than 9-[4-[18F]fluoro-3-(hydroxymethyl)butylguanine ([18F]FHBG) in cells expressing HSV1-tk (P < 0.05), whereas [18F]FHBG showed significantly higher (P < 0.05) accumulation than [18F]FEAU in HSV1-sr39tk-expressing cells. micro-PET imaging of mice carrying tumor xenografts of C6 cells stably expressing HSV1-tk or HSV1-sr39tk are consistent with the cell uptake results. The [18F]FEAU mouse images also showed very low gastrointestinal signal with predominant renal clearance as compared to [18F]FHBG. The routine radiosynthesis of [18F]FEAU was successfully semiautomated using a commercial module along with customized equipment to provide the β-anomer in modest yields. Although further studies are needed, early results also suggest [18F]FEAU is a promising PET radiotracer for monitoring HSV1-tk reporter gene expression.
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References
Penuelas I, Gambhir SS (2005) Imaging studies for evaluating gene therapy in translational research. Drug Discov Today Technol 2:335–343
Min JJ, Gambhir SS (2004) Gene therapy progress and prospects. Noninvasive imaging of gene therapy in living subjects. Gene Therapy 11:115–125
Watanabe KA, Reichman U, Hirota K, Lopez C, Fox JJ (1979) Nucleosides. 110, synthesis and antiherpes virus activity of some 2′-fluoro-2′deoxyarabinofuranosylpyrimidine nucleosides. J Med Chem 22:21–24
Watanabe KA, Su TL, Klein RS, et al. (1983) Nucleosides. 123. Synthesis of antiviral nucleosides: 5-substituted of 1-(2-deoxy-2-halogeno-β-d-arabinofuranosyl)cytosines and-uracils. some structure–activity relationships. J Med Chem 26:152–156
Watanabe KA, Su TL, Reichman U, Greenberg N, Lopez C, Fox JJ (1984) Nucleosides. 129. Synthesis of antiviral nucleosides: 5-alkenyl-1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)uracils. J Med Chem 27:91–94
Perlman ME, Watanabe KA, Schinazi RF, Fox JJ (1985) Nucleosides. 133. Synthesis of 5-alkenyl-1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)cytosines and related pyrimidine nucleosides as potential antiviral agents. J Med Chem 28:741–748
Su TL, Watanabe KA, Shinazi RF, Fox JJ (1986) Nucleosides. 136. Synthesis and antiviral effects of several 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-5-alkyluracils. Some structure–activity relationships. J Med Chem 29:151–154
Kang KW, Min J-J, Chen X, Gambhir SS (2005) Comparison of [14C]FMAU, [3H]FEAU, [14C]FIAU, and [3H]PCV for monitoring reporter gene expression of wild type and mutant herpes simplex virus type 1 thymidine kinase in cell culture. Mol Imaging Biol 7:296–303
Buursma AR, Rutgers V, Hospers GAP, Mulder NH, Vaalburg W, de Vries EFJ (2006) [18F]FEAU as a radiotracer for herpes simplex virus thymidine kinase gene expression: in-vitro comparison with other PET tracers. Nucl Med Commun 27:25–30
Yaghoubi S, Barrio JR, Dahlbom M, et al. (2001) Human pharmacokinetic and dosimetry studies of [18F]FHBG: a reporter probe for imaging herpes simplex virus type-1 thymidine kinase reporter gene expression. J Nucl Med 42:1225–1234
Panuelas I, Mazzolini G, Boan JF, et al. (2005) Positron emission tomography imaging of adenoviral-mediated transgene expression in living cancer patients. Gastroenterology 128:1787–1795
Panuelas I, Haberkorn U, Yaghoubi S, Gambhir SS (2005) Gene therapy imaging in patients for oncological applications. Eur J Nucl Med Mol Imaging 32:S384–403
Yaghoubi S, Couto MA, Chen C, et al. (2006) Preclinical safety evaluation of 18F-FHBG: a PET reporter probe for imaging herpes simplex virus type 1 Thymidine Kinase (HSV1-tk) or mutant HSV1-sr39tk’s expression. J Nucl Med 47:706–715
Gambhir SS, Bauer E, Black ME, et al. (2000) A mutant herpes simplex virus type 1 thymidine kinase reporter gene shows improved sensitivity for imaging reporter gene expression with positron emission tomography. Proc Natl Acad Sci USA 97:2785–2790
Hajitou A, Trepel M, Lilley CE, et al. (2006) A hybrid vector for ligand-directed tumor targeting and molecular imaging. Cell 125:385–398
Alauddin MM, Conti PS, Fissekis JD (2002) Synthesis of [18F]-labeled 2′deoxy-2′fluoro-5-methyl-1-β-D-arabinofuranosyluracil ([18F]-FMAU). J Label Compd Radiopharm 45:583–590
Mangner TJ, Klecker RW, Anderson L, Shields AF (2003) Synthesis of 2′-deoxy-2′-fluoro-5-methyl-1-β-D-arabinofuranosyl nucleosides, [18F]FAU, [18F]FMAU, [18F]FBAU, and [18F]FIAU, as potential PET agents for imaging cellular proliferation. Nucl Med Biol 30:215–224
Alauddin MM, Conti PS, Fissekis JD (2003) A general synthesis of 2′-deoxy-2′-fluoro-5-methyl-1-β-D-arabinofuranosyluracil and its 5-substituted nucleosides. J Label Compd Radiopharm 46:285–289
Tann CH, Brodfuehrer PR, Brundidge SP, Sapino C, Howell HG (1985) Fluorocarbohydrates in synthesis. An efficient synthesis of 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-5-iodouracil (β-FIAU) and 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)thymine (β-FMAU). J Org Chem 50:3644–3647
Wilds CJ, Damha MJ (2000) 2′-Deoxy-2′-fluoro-β-D-arabinonucleosides and oligonucleotides (2′F-ANA): synthesis and physicochemical studies. Nucleic Acids Res 28:3625–3635
Mansuri MM, Ghazzouli I, Chen MS, et al. (1987) 1-(2-Deoxy-2-fluoro-.beta.-D-arabinofuranosyl)-5-ethyluracil. A highly selective antiherpes simplex agent. J Med Chem 30:867–871
Howell HG, Brodfuehrer PR, Brundidge SP, Benigni DA, Sapino C (1988) Antiviral nucleosides. A stereospecific, total synthesis of 2′-fluoro-2′-deoxy-beta-D-arabinofuranosyl nucleosides. J Org Chem 53:85–88
Ray P, Tsien R, Gambhir SS (2007) Construction and validation of improved triple fusion reporter gene vectors for molecular imaging of living subjects. Cancer Res 67:3085–3093
Hudson HM, Larkin RS (1994) Accelerated image reconstruction using ordered subsets of projection data. IEEE Trans Med Imaging 13:601–619
Loening AM, Gambhir SS (2003) AMIDE: a free software tool for multimodality medical image analysis. Mol Imaging 2:131–137
Min JJ, Iyer M, Gambhir SS (2003) Comparison of [18F]FHBG and [14C]FIAU for imaging of HSV1-tk reporter gene expression: adenoviral infection vs. stable transfection. Eur J Nucl Med Mol Imaging 30:1547–1560
Jacobs A, Tjuvajev JG, Dubrovin M, et al. (2001) Positron emission tomography-based Imaging of transgene expression mediated by replication-conditional, oncolytic Herpes Simplex Virus Type 1 mutant vectors in vivo. Cancer Res 61:2983–2995
Tjuvajev JG, Doubrovin M, Akhurst T, et al. (2002) Comparison of radiolabeled nucleoside probes (FIAU, FHBG, and FHPG) for PET imaging of HSV1-tk gene expression. J Nucl Med 43:1072–1083
Tjuvajev JG, Stockhammer G, Desai R, et al. (1995) Imaging the expression of transfected genes in vivo. Cancer Res 55:6126–6132
Tjuvajev JG, Finn R, Watanabe K, et al. (1996) Noninvasive imaging of herpes virus thymidine kinase gene transfer and expression: a potential method for monitoring clinical gene therapy. Cancer Res 56:4087–4095
Tjuvajev JG, Avril N, Oku T, et al. (1998) Imaging herpes virus thymidine kinase gene transfer and expression by positron emission tomography. Cancer Res 58:4333–4341
Tjuvajev JG, Chen SH, Joshi A, et al. (1999) Imaging adenoviral-mediated herpes virus thymidine kinase gene transfer and expression in vivo. Cancer Res 59:5186–5193
Watanabe KA, Su TL, Reichman U, Greenberg N, Lopez C, Fox JJ (1984) Nucleosides. 129. Synthesis of antiviral nucleosides: 5-alkenyl-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)uracils. J Med Chem 1:91–94
Perlman ME, Watanabe KA, Schinazi RF, Fox JJ (1985) Nucleosides. 133. Synthesis of 5-alkenyl-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) cytosines and related pyrimidine nucleosides as potential antiviral agents. J Med Chem 28:741–748
Kong XB, Vidal P, Tong WP, Chiang J, Gloff CA, Chou TC (1992) Preclinical pharmacology and pharmacokinetics of the anti-hepatitis virus agent 2′-fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil in mice and rats. Antimicrob Agents Chemother 36:1472–1477
Black ME, Newcomb TG, Wilson HM, Loeb LA (1996) Creation of drug-specific herpes simplex virus type 1 thymidine kinase mutants for gene therapy. Proc Natl Acad Sci USA 93:3525–3529
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This research was supported in part by ICMIC P50 (SSG) and NIH R05 CA 082214 (SSG).
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Chin, F.T., Namavari, M., Levi, J. et al. Semiautomated Radiosynthesis and Biological Evaluation of [18F]FEAU: A Novel PET Imaging Agent for HSV1-tk/sr39tk Reporter Gene Expression. Mol Imaging Biol 10, 82–91 (2008). https://doi.org/10.1007/s11307-007-0122-3
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DOI: https://doi.org/10.1007/s11307-007-0122-3