Dataset Information

[11 C]Fluoroform, a Breakthrough for Versatile Labeling of PET Radiotracer Trifluoromethyl Groups in High Molar Activity.

ABSTRACT: Positron-emission tomography (PET) is an immensely important imaging modality in biomedical research and drug development but must use selective radiotracers to achieve biochemical specificity. Such radiotracers are usually labeled with carbon-11 (t1/2 =20?min) or fluorine-18 (t1/2 =110?min), but these are only available from cyclotrons in a few simple chemical forms. [18 F]Fluoroform has emerged for labeling tracers in trifluoromethyl groups but is severely limited in utility by low radioactivity per mass (low molar activity). Here, the synthesis of [11 C]fluoroform is described, based on CoF3 -mediated fluorination of cyclotron-produced [11 C]methane. This process is efficient and repetitively reliable. [11 C]Fluoroform shows versatility for labeling small molecules in very high molar activity (>200?GBq??mol-1 ), far exceeding that possible by using [18 F]fluoroform. Therefore, [11 C]fluoroform represents a major breakthrough for labeling prospective PET tracers in trifluoromethyl groups at high molar activity.

SUBMITTER: Haskali MB

PROVIDER: S-EPMC5801743 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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[11 C]Fluoroform, a Breakthrough for Versatile Labeling of PET Radiotracer Trifluoromethyl Groups in High Molar Activity.

Haskali Mohammad B MB Pike Victor W VW

Chemistry (Weinheim an der Bergstrasse, Germany) 20170517 34

Positron-emission tomography (PET) is an immensely important imaging modality in biomedical research and drug development but must use selective radiotracers to achieve biochemical specificity. Such radiotracers are usually labeled with carbon-11 (t1/2 =20 min) or fluorine-18 (t1/2 =110 min), but these are only available from cyclotrons in a few simple chemical forms. [18 F]Fluoroform has emerged for labeling tracers in trifluoromethyl groups but is severely limi ...[more]

PMID: 28514059

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Project description:This was a first-in-human study of the PET radiotracer 11C-LSN3172176 for the muscarinic acetylcholine receptor subtype M1. The objectives of the study were to determine the appropriate kinetic model to quantify binding of the tracer to M1 receptors, and the reliability of the chosen quantification method. Methods: Six healthy subjects completed the test-retest protocol, and 5 healthy subjects completed the baseline-scopolamine blocking protocol. Multiple modeling methods were applied to calculate total distribution volume (V T) and nondisplaceable binding potential (BP ND) in various brain regions. The reference region was selected from the blocking study. The occupancy plot was applied to compute receptor occupancy by scopolamine and nondisplaceable distribution volume. Results: Tracer uptake was highest in the striatum, followed by neocortical regions and white matter, and lowest in the cerebellum. Regional time-activity curves were fitted well by all models. The 2-tissue-compartment (2TC) model fits were good, but the 2TC parameters often could not be reliably estimated. Because V T correlated well between the 2TC and 1-tissue-compartment (1TC) models after exclusion of unreliable estimates, the 1TC model was chosen as the most appropriate. The cerebellum showed the lowest V T, consistent with preclinical studies showing little to no specific binding in the region. Further, cerebellar V T did not change between baseline and blocking scans, indicating that the cerebellum is a suitable reference region. The simplified reference tissue model (SRTM) slightly underestimated 1TC BP ND, and the simplified reference tissue model 2 (SRTM2) improved BP ND estimation. An 80-min scan was sufficient to quantify V T and BP ND The test-retest study showed excellent absolute test-retest variability for 1TC V T (≤5%) and BP ND (≤10%). In the baseline and blocking studies, occupancy values were lower in the striatum than in nonstriatal regions, as may be attributed to differences in regional acetylcholine concentrations. Conclusion: The 1TC and SRTM2 models are appropriate for quantitative analysis of 11C-LSN3172176 imaging data. 11C-LSN3172176 displayed excellent test-retest reproducibility and is a highly promising ligand to quantify M1 receptors in the human brain.

Dataset Information

[11 C]Fluoroform, a Breakthrough for Versatile Labeling of PET Radiotracer Trifluoromethyl Groups in High Molar Activity.

Publications

[<sup>11</sup> C]Fluoroform, a Breakthrough for Versatile Labeling of PET Radiotracer Trifluoromethyl Groups in High Molar Activity.

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