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11C-Labeling of a Potent Hydroxyethylamine BACE-1 Inhibitor and Evaluation in vitro and in vivo
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
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2014 (English)In: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 41, no 6, 536-543 p.Article in journal (Refereed) Published
Abstract [en]

Introduction: The enzyme beta-secretase 1 (BACE-1) is associated with the catalytic cleavage of amyloid precursor protein (APP) which leads to the production of amyloid-p, an amyloidogenic peptide that forms insoluble fibrils and is linked to neurodegeneration and Alzheimer's disease (AD). A PET-radioligand for the quantification of BACE-1 would be useful for the understanding of AD. In this report, we describe the synthesis and carbon-11 radiolabeling of a potent hydroxyethylamine BACE-1 enzyme inhibitor (BSI-IV) and its evaluation in vitro and in vivo. Methods: (11)[C]-N-1-((2S,3R)-4-(cyclopropylamino)-3-hydroxy-1-phenylbutan-2-y1)-5-(N-methylmethylsulfonamido)-N-3-((R)-1-phenylethyl)isophthalamide, a p-secretase inhibitor, denoted here as [C-11]BSIIV was synthesized through a palladium-mediated aminocarbonylation with an aryl halide precursor (I or Br) and [C-11]CO. The effect of different palladium/ligand-complexes on radiochemical yield in the carbonylative reaction was investigated. The binding of the labeled compound to BACE-1 enzyme was studied in vitro by frozen section autoradiography from brains of healthy rats. Dynamic small animal PET-CT studies and ex vivo biodistribution were performed in male rats. Results: The halide precursors were synthesized in six steps starting from methyl-3-nitrobenzoate with an overall yield of 21-26%. [C-11]BSI-IV was obtained in 29 +/- 12% decay corrected radiochemical yield (n = 12) with a specific activity of 790 +/- 155 GBq/umol at the end of synthesis with a radiochemical purity of >99%. The predinical studies showed that [C-11]BSI-IV has a rapid metabolism in rat with excretion to the small intestines. Conclusion: [C-11]BSI-IV was obtained in sufficient amount and purity to enable predinical investigation. The predinical studies showed low specific binding in vitro and fast clearance in vivo and a low uptake in the brain. These findings suggests that [C-11]BSI-IV has limited use as a PET-ligand for the study of BACE-1 or AD.

Place, publisher, year, edition, pages
2014. Vol. 41, no 6, 536-543 p.
National Category
Organic Chemistry Medicinal Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-213860DOI: 10.1016/j.nucmedbio.2014.03.024ISI: 000336946400014OAI: oai:DiVA.org:uu-213860DiVA: diva2:683587
Available from: 2014-01-05 Created: 2014-01-05 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Development of Palladium-Promoted 11C/12C-Carbonylations and Radiosynthesis of Amyloid PET Ligands
Open this publication in new window or tab >>Development of Palladium-Promoted 11C/12C-Carbonylations and Radiosynthesis of Amyloid PET Ligands
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the first part of this thesis, palladium(0)-catalyzed and -mediated carbonylations are discussed. Paper I describes a new method for the safe, efficient use of a solid carbon monoxide source in the synthesis of primary and secondary benzamides. In total, 35 benzamides were synthesized from aryl iodides (20 examples, 69-97% yield) and aryl bromides (15 examples, 32-93% yield). Reduction-prone groups were used successfully in the reactions. In paper II, the same protocol was adopted for the palladium(0)-catalyzed synthesis of N-cyanobenzamides from aryl iodides/bromides, carbon monoxide and cyanamide. In total, 22 N-cyanobenzamides were synthesized (42-88% yield). The radiosynthesis of [11C]N-cyanobenzamides is discussed in paper III. In total, 22 compounds were synthesized from various aryl halides in 28-79% decay corrected radiochemical yield. The protocol was then applied to the radiosynthesis of [11C]N-cyanobenzamide analogs of flufenamic acid and dazoxibene.

In the second part of this thesis, compounds of interest in relation to amyloid diseases are discussed. Paper IV describes the solid-phase synthesis of BACE-1 enzyme inhibitors containing secondary and tertiary hydroxyl as the transition state isostere. In total, 22 inhibitors were synthesized. The most potent compound (IC50= 0.19 µM) was co-crystallized at the active site of the enzyme to reveal a new binding mode. In paper V, the evaluation of a potent BACE-1 inhibitor as a potential radiotracer for use in PET is described. The radiolabeled [11C]BSI-IV was obtained in 29±12% decay corrected radiochemical yield by a three-component palladium(0)-mediated aminocarbonylation. Its properties as a potential PET tracer were investigated in vitro by autoradiography and in vivo in rats using small animal PET-CT. A new class of amyloid-binding PET ligands is described in paper VI. Three polythiophenes were labeled with carbon-11 or fluorine-18 (26-43% decay-corrected radiochemical yield). The in vitro studies showed that these ligands bind specifically to amyloid deposits. In vivo PET showed low uptake in the organs of interest in healthy rats and a monkey. These results suggest the labeled thiophenes derivatives could be useful as PET tracers for the study of amyloid diseases.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2014. 76 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 183
Keyword
Palladium, Carbonylation, Positron emission tomography, PET, Carbon-11, Fluor-18, Radiochemistry, Amyloidosis, Palladium, Karbonyleringar, Positronemissionstomografi, PET, Kol-11, Fluor-18, Radiokemi, Amyloidos
National Category
Pharmaceutical Chemistry Medicinal Chemistry
Research subject
Pharmaceutical Science; Chemistry with specialization in Organic Chemistry; Medicinal Chemistry
Identifiers
urn:nbn:se:uu:diva-213863 (URN)978-91-554-8843-7 (ISBN)
Public defence
2014-02-21, B21, BMC, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2014-01-30 Created: 2014-01-05 Last updated: 2014-02-10

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Nordeman, PatrikEstrada, SergioOdell, Luke RLarhed, MatsAntoni, Gunnar

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