DOI: 10.1007/s00259-018-4119-8Pages: 1-11

Quantifying SV2A density and drug occupancy in the human brain using [11C]UCB-J PET imaging and subcortical white matter as reference tissue

1. KU Leuven, Department of Nuclear Medicine and Molecular Imaging

2. UCB Pharma

Correspondence to:
Michel Koole
Tel: + 32 16-341242
Email: michel.koole@kuleuven.be

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Abstract

Purpose

A [11C]UCB-J blocking study was performed in healthy volunteers to validate simplified, non-invasive measures for quantifying presynaptic SV2A expression using subcortical white matter as reference tissue.

Methods

Ninety minutes dynamic [11C]UCB-J PET scanning with arterial blood sampling was performed in 10 healthy volunteers (8 M/2F; age 27.6 ± 10.0 yrs), before and after administration of a novel chemical entity with selective affinity for SV2A. The centrum semi-ovale (SO) was validated as reference region by comparing baseline and post treatment distribution volume (VT). Using SO as reference tissue, Binding Potential (BPSO) using a Simplified Reference Tissue Model (SRTM, down to 60 min acquisition) and Standardized Uptake Value Ratios (60-90 min post injection - SUVRSO,60-90min) were compared with regional distribution volume ratios (DVR). Next, SV2A occupancy values based on SRTM BPSO and SUVRSO,60-90min were compared to occupancy estimates using regional VT values and a Lassen plot.

Results

After pretreatment, regional VT values were reduced significantly except for SO. Highly significant correlations were found between DVR, SRTM BPSO and SUVRSO,60–90min. Compared to DVR, baseline SRTM BPSO showed a small bias (≤ 6.1%) with lower precision for shorter acquisition times, while SUVRSO,60-90min showed 3.5% bias with similar precision. Differences between SV2A occupancy values based on SUVRSO,60-90min and occupancy estimates using VT and a Lassen plot were small but significant, while negligible bias was found for SRTM based occupancy estimates (at least 70 min acquisition).

Conclusion

This [11C]UCB-J blocking study validated SO as a suitable reference region for non-invasive quantification of SV2A availability and drug occupancy in the human brain. Accurate quantification can be achieved by using either SUVRSO,60-90min with a 60–90 min PET acquisition or SRTM BPSOwith at least 70 min dynamic PET acquisition.

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  • Accepted: Jul 30, 2018
  • Online: Aug 18, 2018

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