Dataset Information

Preparation and evaluation of tetrabenazine enantiomers and all eight stereoisomers of dihydrotetrabenazine as VMAT2 inhibitors.

ABSTRACT: Tetrabenazine (TBZ) ((±)-1) and dihydrotetrabenazines (DHTBZ) are potent inhibitors of VMAT2. Herein, a practical chemical resolution of (±)-1 and stereoselective synthesis of all eight DHTBZ stereoisomers are described. The result of VMAT2 binding assay revealed that (+)-1 (Ki=4.47 nM) was 8000-fold more potent than (-)-1 (Ki=36,400 nM). Among all eight DHTBZ stereoisomers, (2R,3R,11bR)-DHTBZ ((+)-2: Ki=3.96 nM) showed the greatest affinity for VMAT2. The (3R,11bR)-configuration appeared to play a key role for VMAT2 binding. In summary, (+)-1, (+)-2, and their derivatives warrant further studies in order to develop more potent and safer drugs for the treatment of chorea associated with Huntington's disease and other hyperkinetic disorders.

SUBMITTER: Yao Z

PROVIDER: S-EPMC6191844 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Preparation and evaluation of tetrabenazine enantiomers and all eight stereoisomers of dihydrotetrabenazine as VMAT2 inhibitors.

Yao Zhangyu Z Wei Xueying X Wu Xiaoming X Katz Jonathan L JL Kopajtic Theresa T Greig Nigel H NH Sun Hongbin H

European journal of medicinal chemistry 20110223 5

Tetrabenazine (TBZ) ((±)-1) and dihydrotetrabenazines (DHTBZ) are potent inhibitors of VMAT2. Herein, a practical chemical resolution of (±)-1 and stereoselective synthesis of all eight DHTBZ stereoisomers are described. The result of VMAT2 binding assay revealed that (+)-1 (Ki=4.47 nM) was 8000-fold more potent than (-)-1 (Ki=36,400 nM). Among all eight DHTBZ stereoisomers, (2R,3R,11bR)-DHTBZ ((+)-2: Ki=3.96 nM) showed the greatest affinity for VMAT2. The (3R,11bR)-configuration appeared to pla ...[more]

PMID: 21396745

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Project description:18F-Fluoropropyl-(+)-dihydrotetrabenazine (18F-FP-(+)-DTBZ) is a vesicular monoamine transporter type 2 (VMAT2) radiotracer for positron emission tomography (PET) imaging to quantify human ?-cell mass. Renal cortex and spleen have been suggested as reference regions, however, little is known about 18F-FP-(+)-DTBZ binding in these regions including the fraction of radiometabolite. We compared the kinetics of 18F-FP-(+)-DTBZ and its inactive enantiomer 18F-FP-(-)-DTBZ in baboons, estimated the non-displaceable binding (VND) of the tracers, and used ex vivo studies to measure radiometabolite fractions.PET scans were conducted for up to 4h with (+) and (-) enantiomers. Displacement experiments using unlabeled (+) and (-) enantiomers of FP-DTBZ and fluvoxamine (to evaluate sigma-1 receptor binding) were performed. SUV curves were used to calculate displacement values in the pancreas, renal cortex, and spleen. Distribution volumes (VT) were computed, and three approaches for calculation of VND were compared: (1) 18F-FP-(+)-DTBZ reference VT, (2) 18F-FP-(-)-DTBZ pancreatic VT, and (3) a scaled 18F-FP-(+)-DTBZ reference VT values. Ex vivo study was conducted to measure radiometabolite fraction in homogenized tissue samples from baboons at 90min post-injection.Spleen uptake was lowest for both tracers. Highest uptake was in the pancreas with 18F-FP-(+)-DTBZ and renal cortex with 18F-FP-(-)-DTBZ. Substantial displacement effect was observed only with unlabeled FP-(+)-DTBZ in the 18F-FP-(+)-DTBZ studies. Radiometabolite fraction was higher in the renal cortex than the spleen. Approaches (1) and (3) with spleen to estimate VND provided lowest inter-subject variability of BPND.VT differences among organs and between enantiomers indicated that scaling of reference region values is needed for quantification of VMAT2 binding in the pancreas with 18F-FP-(+)-DTBZ. Since the kidney PET signal has greater partial volume averaging and more radiometabolites, the spleen was considered a more practical candidate for use as a scaled-reference region in the quantification of 18F-FP-(+)-DTBZ in the pancreas.

Project description:PURPOSE:Previous studies demonstrated the utility of [18F]fluoropropyl-(+)-dihydrotetrabenazine ([18F]FP-(+)-DTBZ) as a positron emission tomography (PET) radiotracer for the vesicular monoamine transporter type 2 (VMAT2) to quantify beta cell mass in healthy control (HC) and type 1 diabetes mellitus (T1DM) groups. Quantification of specific binding requires measurement of non-displaceable uptake. Our goal was to identify a reference tissue (renal cortex or spleen) to quantify pancreatic non-specific binding of [18F]FP-(+)-DTBZ with the inactive enantiomer, [18F]FP-(-)-DTBZ. This was the first human study of [18F]FP-(-)-DTBZ. PROCEDURES:Six HCs and four T1DM patients were scanned on separate days after injection of [18F]FP-(+)-DTBZ or [18F]FP-(-)-DTBZ. Distribution volumes (VT) and standardized uptake values (SUVs) were compared between groups. Three methods for calculation of non-displaceable uptake (VND) or reference SUV were applied: (1) use of [18F]FP-(+)-DTBZ reference VT as VND, assuming VND is uniform across organs; (2) use of [18F]FP-(-)-DTBZ pancreatic VT as VND, assuming that VND is uniform between enantiomers in the pancreas; and (3) use of a scaled [18F]FP-(+)-DTBZ reference VT as VND, assuming that a ratio of non-displaceable uptake between organs is uniform between enantiomers. Group differences in VT (or SUV), binding potential (BPND), or SUV ratio (SUVR) were estimated using these three methods. RESULTS:[18F]FP-(-)-DTBZ VT values were different among organs, and VT(+) and VT(-) were also different in the renal cortex and spleen. Method 3 with the spleen to estimate VND (or reference SUV) gave the highest non-displaceable uptake and the largest HC vs. T1DM group differences. Significant group differences were also observed in VT (or SUV) with method 1 using spleen. SUV was affected by differences in the input function between groups and between enantiomers. CONCLUSIONS:Non-displaceable uptake was different among organs and between enantiomers. Use of scaled spleen VT values for VND is a suitable method for quantification of VMAT2 in the pancreas.

Dataset Information

Preparation and evaluation of tetrabenazine enantiomers and all eight stereoisomers of dihydrotetrabenazine as VMAT2 inhibitors.

Publications

Preparation and evaluation of tetrabenazine enantiomers and all eight stereoisomers of dihydrotetrabenazine as VMAT2 inhibitors.

Similar Datasets

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