Title
Synthesis and preclinical evaluation of an <tex>$^{18}F$</tex> labeled PDE7 inhibitor for PET neuroimaging Synthesis and preclinical evaluation of an <tex>$^{18}F$</tex> labeled PDE7 inhibitor for PET neuroimaging
Author
Faculty/Department
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
Faculty of Medicine and Health Sciences
Publication type
article
Publication
Subject
Human medicine
Computer. Automation
Source (journal)
Nuclear medicine and biology
Volume/pages
42(2015) :12 , p. 975-981
ISSN
0969-8086
0969-8051
ISI
000366149500010
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
Introduction Phosphodiesterase 7 (PDE7) hydrolyzes selectively cyclic adenosine monophosphate (cAMP) which is an intracellular second messenger. PDE7 is expressed by 2 genes which are both present in the brain. To date there is no radiotracer for PDE7 imaging described and detection of PDE7 has only been performed by ex vivo techniques. In this report we describe the radiosynthesis of a novel fluorine-18 labeled radiotracer for PDE7 as well as the in vivo evaluation in mice to verify whether it has potential for imaging of PDE7 in the brain. Methods We have synthesized a potent fluorinated PDE7 inhibitor, [18F]MICA-003 (PDE7 IC50 = 17 nM) and the corresponding tosylate precursor for radiolabeling. [18F]MICA-003 was injected in C57BL/6 J mice (n = 5) and in vivo images were acquired by μPET imaging. Radiometabolite analysis in plasma and brain was performed to determine the stability of the radioligand. Results [18F]MICA-003 was synthesized by direct fluorination of the tosylate and produced in high decay corrected radiochemical yield (40%), high radiochemical purity (> 98%) and high specific activity (86497 GBq/μmol). μPET imaging revealed that [18F]MICA-003 crosses the blood brain barrier and has a homogenous distribution over the brain which washes out after the initial peak uptake. [18F]MICA-003 was quickly metabolized in plasma with 8.9% ± 0.59% of intact [18F]MICA-003 remaining at 5 min post injection. We observed the formation of three distinct radiometabolites of which the main radiometabolite was also detected in the brain in a proportion of 25.7 ± 2.57% at this same time point. Conclusion We have described the synthesis and in vivo evaluation of a novel radioligand for PDE7 imaging. Despite high uptake in the brain and favorable kinetics in vivo, the presence of a brain penetrant radiometabolite makes [18F]MICA-003 unfavorable for the accurate quantification of PDE7 and more stable spiroquinazolinones analogs are in development.
E-info
https://repository.uantwerpen.be/docman/iruaauth/4e353a/9c6d691222e.pdf
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000366149500010&DestLinkType=RelatedRecords&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000366149500010&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000366149500010&DestLinkType=CitingArticles&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848
Handle