Synthesis and initial evaluation of [11C](R)-RWAY in monkey—a new, simply labeled antagonist radioligand for imaging brain 5-HT1A receptors with PET

  • Julie A. McCarron
  • Sami S. Zoghbi
  • H. Umesha Shetty
  • Eric S. Vermeulen
  • Håkan V. Wikström
  • Masanori Ichise
  • Fumihiko Yasuno
  • Christer Halldin
  • Robert B. Innis
  • Victor W. Pike
Original Article

Abstract

Purpose

We aimed to fulfill a need for a radioligand that may be simply labeled with carbon-11 for effective positron emission tomography (PET) imaging of brain 5-HT1A receptors.

Methods

Racemic RWAY (2,3,4,5,6,7-hexahydro-1-[4-[1-[4-(2-methoxyphenyl)piperazinyl]]-2-phenylbutyryl]-1H-azepine) has high affinity for 5-HT1A receptors. The enantiomers of RWAY and O-desmethyl-RWAY, synthesized from commercially available materials, were each labeled with carbon-11 by treating the respective O-desmethyl precursor with [11C]iodomethane, and injected into rhesus monkey for measurement of regional brain uptake. The 5-HT1A selectivity of (R)-[11C]RWAY was checked by administering WAY-100635, before and after radioligand administration. Radiometabolites of (R)-[11C]RWAY in blood and urine were analyzed by HPLC with partial elucidation of their structures by LC-MS-MS.

Results

(R)-[11C]RWAY was a 5-HT1A receptor antagonist exhibiting high brain uptake with regional distribution consistent with specific binding to 5-HT1A receptors. The similar affinity, (S)-[11C]RWAY was a weak partial agonist at 5-HT1A receptors exhibiting similar brain peak uptake with much less 5-HT1A receptor-specific binding. The maximal ratio in receptor-rich cingulate gyrus to receptor-devoid cerebellum reached 6.4 at 87.5 min after injection of (R)-[11C]RWAY. After treatment with WAY-100635 before or after (R)-[11C]RWAY administration, radioactivity levels in 5-HT1A receptor-rich regions were reduced almost to that in cerebellum. Blood and urine radiometabolites were less lipophilic than parent and were not due to hydrolysis but to ring hydroxylations, oxidation, and dephenylation.

Conclusion

(R)-[11C]RWAY is simply prepared and an effective antagonist for imaging brain 5-HT1A receptors. This radioligand resists hydrolysis in vivo, gives less lipophilic radiometabolites, and warrants further PET studies in human subjects.

Keywords

5-HT1A receptor PET Radioligand [11C](R)-RWAY Imaging 

Notes

Acknowledgements

This work was supported by the Intramural Research Program of the National Institutes of Health (National Institute of Mental Health; project # Z01-MH-002852-01). An early phase of this project was also supported by the Human Frontier Science Program Organization (grant # RG 235/98). We are grateful to the National Institute of Mental Health Psychoactive Drug Screening Program (Director Dr. Bryan L. Roth) for performing binding and functional assays, and to Mr Jinsoo Hong for assistance in radioligand production.

References

  1. 1.
    Pike VW, McCarron JA, Hume SP, Ashworth S, Opacka-Juffry J, Osman S, et al. Pre-clinical development of a radioligand for studies of central 5-HT1A receptors in vivo—[11C]WAY-100635. Med Chem Res 1994;5:208–27.Google Scholar
  2. 2.
    Farde L, Ginovart N, Ito H, Lundkvist C, Pike VW, McCarron JA, et al. PET-characterization of [carbonyl- 11C]WAY-100635 binding to 5-HT1A receptors in the primate brain. Psychopharmacology 1997;133:196–202.PubMedCrossRefGoogle Scholar
  3. 3.
    Pike VW, McCarron JA, Lammertsma AA, Osman S, Bench CJ, Grasby PM, et al. Exquisite delineation of 5-HT1A receptors in human brain with PET and [carbonyl-11C]WAY-100635. Eur J Pharmacol 1996;301:R5–7.PubMedCrossRefGoogle Scholar
  4. 4.
    Pike VW, Halldin C, Wikström HV. Radioligands for the study of 5-HT1A receptors in vivo. Progr Med Chem 2000;38:189–247.CrossRefGoogle Scholar
  5. 5.
    Andrée B, Halldin C, Thorberg S, Sandell J, Farde L. Use of PET and the radioligand [carbonyl-11C]WAY-100635 in psychotropic drug development. Nucl Med Biol 2000;27:515–21.PubMedCrossRefGoogle Scholar
  6. 6.
    Osman S, Lundkvist C, Pike VW, Halldin C, McCarron JA, Swahn CG, et al. Characterization of the radioactive metabolites of the 5-HT1A receptor radioligand, [O-methyl-11C]WAY-100635, in monkey and human plasma by HPLC: comparison of the behaviour of an identified radioactive metabolite with parent radioligand in monkey using PET. Nucl Med Biol 1996;23:627–34.PubMedCrossRefGoogle Scholar
  7. 7.
    Osman S, Lundkvist C, Pike VW, Halldin C, McCarron JA, Swahn CG, et al. Characterization of the appearance of radioactive metabolites in monkey and human plasma from the 5-HT1A receptor radioligand, [carbonyl-11C]WAY-100635—explanation of high signal contrast in PET and an aid to biomathematical modeling. Nucl Med Biol 1998;25:215–23.PubMedCrossRefGoogle Scholar
  8. 8.
    Mathis CA, Simpson NR, Mahmood K, Kinahan PE, Mintun MA. [11C]WAY-100635—a radioligand for imaging 5-HT1A receptors with positron emission tomography. Life Sci 1994;55:PL403–7.PubMedCrossRefGoogle Scholar
  9. 9.
    McCarron JA, Turton DR, Pike VW, Poole KG. Remotely-controlled production of the 5-HT1A receptor radioligand, [carbonyl-11C]WAY-100635, via 11C-carboxylation of an immobilized Grignard reagent. J Label Compd Radiopharm 1996;38:941–53.CrossRefGoogle Scholar
  10. 10.
    Hwang D-R, Simpson NR, Montoya J, Mann JJ. An improved one-pot procedure for the preparation of [11C-carbonyl]-WAY100635. Nucl Med Biol 1999;26:815–9.PubMedCrossRefGoogle Scholar
  11. 11.
    Andrée B, Olsson J, Halldin C, Pike VW, Farde L. The PET radioligand [carbonyl-11C]desmethyl-WAY-100635 binds selectively to 5-HT1A receptors and induces a higher radioactive signal than [carbonyl-11C]WAY-100635 in the living brain. J Nucl Med 2002;43:292–303.PubMedGoogle Scholar
  12. 12.
    Pike VW, Halldin C, McCarron JA, Lundkvist C, Hirani E, Olsson H, et al. [carbonyl-11C]Desmethyl-WAY-100635 (DWAY) is a potent and selective radioligand for central 5-HT1A receptors in vitro and in vivo. Eur J Nucl Med 1998;25:338–46.PubMedCrossRefGoogle Scholar
  13. 13.
    Itsenko O, Kihlberg T, Blom E, Långström B. One step synthesis of [carbonyl- 11C]WAY-100635. J Label Compd Radiopharm 2005:48;S135.Google Scholar
  14. 14.
    Carson RE, Toczek MT, Lang LX, Fraser C, Spanaki MV, Ma Y, et al. Human functional imaging with the 5-HT1A ligand 18F-FCWAY. J Nucl Med 2002;198(Suppl S):55P.Google Scholar
  15. 15.
    Passchier J, Van Waarde A, Pieterman RM, Elsinga PH, Pruim J, Hendrikse HN, et al. In vivo delineation of 5-HT1A receptors in human brain. J Nucl Med 2000;41:1830–5.PubMedGoogle Scholar
  16. 16.
    Passchier J, Van Waarde A, Vaalburg W, Willemsen ATM. On the quantification of [18F]MPPF binding to 5-HT1A receptors in the human brain. J Nucl Med 2001;42:1025–31.PubMedGoogle Scholar
  17. 17.
    Sanabria-Bohorquez SM, Biver F, Damhautr P, Wikler D, Veraart C, Goldman S. Quantification of 5-HT1A receptors in human brain using p-MPPF kinetic modeling and PET. Eur J Nucl Med Mol Imaging 2002;29:76–81.PubMedCrossRefGoogle Scholar
  18. 18.
    Tipre DN, Zoghbi SS, Liow JS, Green MV, Seidel J, Ichise M, et al. PET imaging of brain 5-HT1A receptors in rat in vivo with [18F]FCWAY and improvement by successful inhibition of radioligand defluorination with miconazole. J Nucl Med 2006;47:345–53.PubMedGoogle Scholar
  19. 19.
    Carson RE, Wu YJ, Lang LX, Ma Y, Der MG, Herscovitch P, et al. Brain uptake of the acid metabolites of 18F-labeled WAY 100635 analogs. J Cereb Blood Flow Metab 2003;23:249–60.PubMedCrossRefGoogle Scholar
  20. 20.
    Cliffe IA. Piperazine derivatives. EP 481744 A1, 1991.Google Scholar
  21. 21.
    Campiani G, Butini S, Trotta F, Fattorusso C, Catalanotti B, Aiello F, et al. Synthesis and pharmacological evaluation of potent and highly selective D3 receptor ligands: inhibition of cocaine-seeking behavior and the role of dopamine D3/D2 receptors. J Med Chem 2003;46:3822–39.PubMedCrossRefGoogle Scholar
  22. 22.
    Zhuang Z-P, Kung M-P, Mu M, Kung HF. Isoindol-1-one analogues of 4-(2′-methoxyphenyl)-1-[2′-[N-(2″-pyridyl)-p-iodobenzamido]ethyl]piperazine (p-MPPI) as 5-HT1A receptor ligands. J Med Chem 1998;41:157–66.PubMedCrossRefGoogle Scholar
  23. 23.
    Zoghbi SS, Baldwin RM, Seibyl J, Charney DS, Innis RB. A radiotracer technique for determining apparent pKa of receptor binding ligands. J Label Compd Radiopharm 1997;42:S136–8.Google Scholar
  24. 24.
    Clark JD, Baldwin RL, Bayne KA, Brown MJ, Gebhart GF, Gunder JC, et al. Guide for the care and use of laboratory animals. Washington, DC: National Academy Press, 1996.Google Scholar
  25. 25.
    Gandelman M, Baldwin RM, Zoghbi SS, Zea-Ponce Y, Innis RB. Evaluation of ultrafiltration for the free fraction determination of SPECT radiotracers: β-CIT, IBF and iomazenil. J Pharm Sci 1994;83L:1014–9.CrossRefGoogle Scholar
  26. 26.
    Shepherd RG. Process for the preparation of o-aryl-γ-butyrolactones. WO 94/12487. 1994.Google Scholar
  27. 27.
    Shuomingshu FZSG. Preparation of the known neurotransmitter antagonist 1-[4-[4-(methoxyphenyl)-1-piperazinyl]-4-phenylbutyryl]hexahydro-1H-azepine and its salts and enantiomers. CN 10766446. 1993.Google Scholar
  28. 28.
    Ashwell MA. Amide derivatives. WO 9408983.1994.Google Scholar
  29. 29.
    Lahti RA, Roberts RC, Cochrane EV, Primus RJ, Gallagher DW, Conley RR, et al. Direct determination of dopamine D4 receptors in normal and schizophrenic brain tissue: a [3H]NGD-94-1 study. Mol Psychiatry 1998;3:528–33.PubMedCrossRefGoogle Scholar
  30. 30.
    Scheperjans F, Palomero-Gallagher N, Grefkes C, Scheicher A, Zilles K. Transmitter receptors reveal segregation of cortical areas in the human superior parietal cortex :relations to visual and somatosensory regions. NeuroImage 2005;28:362–79.PubMedCrossRefGoogle Scholar
  31. 31.
    Quick M, Police S, He l, Di Monte DA, Langston JW. Expression of D(3) receptor messenger RNA and binding sites in monkey striatum and substantia nigra after nigrostriatal degeneration: effect of levodopa treatment. Neurosci 2000;98:263–73.CrossRefGoogle Scholar
  32. 32.
    Varnäs K, Halldin C, Hall H. Autoradiographic distribution of serotonin transporters and receptor subtypes in human brain. Human Brain Mapping 2004;22:246–60.PubMedCrossRefGoogle Scholar
  33. 33.
    Burnet PW, Eastwood SL, Harrison PJ. [3H]WAY-100635 for 5-HT1A receptor autoradiography in human brain; a comparison with [3H]8-OH-DPAT and demonstration of increased binding in the frontal cortex in schizophrenia. Neurochem Int 1997;30:565–74.PubMedCrossRefGoogle Scholar
  34. 34.
    Pike VW. Positron-emitting radioligands for studies in vivo–probes for human psychopharmacology. J Psychopharmacol 1993;7:139–58.CrossRefGoogle Scholar
  35. 35.
    Waterhouse RN. Determination of lipophilicity and its use as a predictor of blood-brain barrier penetration of molecular imaging agents. Mol Imaging Biol 2003;5:376–89.PubMedCrossRefGoogle Scholar
  36. 36.
    Farde L, Ginovart N, Itoh H, Lundkvist C, Pike VW, McCarron JA, et al. PET characterization of [carbonyl-11C]WAY-100635 binding to 5-HT1A receptors in the primate brain. Psychopharmacology 1997;133:196–202.PubMedCrossRefGoogle Scholar
  37. 37.
    Shetty HU, Zoghbi SS, McCarron JA, Liow J-S, Hong J, Pike VW. Characterization of in vivo rat metabolites of [O-methyl-11C]RWAY by LC-MS. J Label Compd Radiopharm 2005;48:S278.CrossRefGoogle Scholar
  38. 38.
    Yasuno F, Zoghbi SS, McCarron JA, Ichise M, Gladding RL, Brown AK, et al. Quantification of serotonin 5-HT1A receptors in monkey brain with [11C](–)-RWAY. Synapse 2006;60:510–20.PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Julie A. McCarron
    • 1
  • Sami S. Zoghbi
    • 1
  • H. Umesha Shetty
    • 1
  • Eric S. Vermeulen
    • 2
  • Håkan V. Wikström
    • 2
  • Masanori Ichise
    • 1
  • Fumihiko Yasuno
    • 1
  • Christer Halldin
    • 3
  • Robert B. Innis
    • 1
  • Victor W. Pike
    • 1
  1. 1.Molecular Imaging Branch, National Institute of Mental HealthNational Institutes of HealthBethesdaUSA
  2. 2.Department of Medicinal Chemistry, University Center for PharmacyUniversity of GroningenGroningenThe Netherlands
  3. 3.Department of Clinical Neuroscience, Psychiatry SectionKarolinska InstitutetStockholmSweden

Personalised recommendations