Preclinical In Vitro and In Vivo Characterization of Synaptic Vesicle 2A-Targeting Compounds Amenable to F-18 Labeling as Potential PET Radioligands for Imaging of Synapse Integrity.
Mol Imaging Biol
; 22(4): 832-841, 2020 08.
Article
em En
| MEDLINE
| ID: mdl-31728839
ABSTRACT
PURPOSE:
Current synaptic vesicle 2A (SV2A) positron emission tomography (PET) imaging agents include the nanomolar affinity probes [11C]UCB-J and [18F]UCB-H derived from the anti-epileptic drug levitaracetam (Keppra®). An industry-utilized "de-risking" approach was used to carry out initial pharmacological characterization and to assess potential next-generation candidates amenable to F-18 radiolabeling for preliminary evaluation. PROCEDURES Radioligand binding methods were employed in mammalian brain homogenates to determine the SV2A affinity (Kd) and maximal binding capacity (Bmax) of [3H]UCB-J. Novel leads were then screened to identify compounds minimally with comparable binding affinities with UCB-J in order to select a F-18-labeled candidate for subsequent in vivo assessment in rat. In parallel, mammalian brain tissue section autoradiography was performed to assess specific SV2A distribution.RESULTS:
[3H]UCB-J bound with high affinity to a single population of sites in the rat brain (Kd = 2.6 ± 0.25 nM; Bmax = 810 ± 25 fmol/mg protein) and control human cortex (Kd = 2.9 ± 0.54 nM; Bmax = 10,000 ± 640 fmol/mg protein). Distribution of specific SV2A binding was shown to be homogeneous throughout the rodent brain and primarily in gray matter regions of rodent and human brain sections. Analog screening identified MNI-1038, MNI-1126/SDM-8, and SDM-2 as having comparable binding affinities with the currently available PET ligands. Subsequent [18F]MNI-1126/[18F]SDM-8 dynamic micro-PET imaging in rats revealed in vivo uptake and accumulation in the brain with favorable kinetics. Chase studies using 30 mg/kg levetiracetam confirmed that in vivo brain uptake of [18F]MNI-1126/[18F]SDM-8 was reversible.CONCLUSIONS:
Taken together, these data suggest [18F]MNI-1126/[18F]SDM-8 (since renamed as [18F]SynVesT-1) characterized via an in vitro screening cascade provided a measurable in vivo SV2A specific signal in the rodent brain. This tracer as well as the close analog [18F]SDM-2 (since renamed as [18F]SynVesT-2) is currently undergoing further evaluation in preclinical and clinical studies.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Coloração e Rotulagem
/
Sinapses
/
Radioisótopos de Flúor
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Glicoproteínas de Membrana
/
Compostos Radiofarmacêuticos
/
Proteínas do Tecido Nervoso
Tipo de estudo:
Prognostic_studies
Limite:
Animals
/
Humans
Idioma:
En
Revista:
Mol Imaging Biol
Assunto da revista:
BIOLOGIA MOLECULAR
/
DIAGNOSTICO POR IMAGEM
Ano de publicação:
2020
Tipo de documento:
Article
País de afiliação:
Estados Unidos