[18F]LW223 has low non-displaceable binding in murine brain, enabling high sensitivity TSPO PET imaging

Neuroinflammation is associated with a number of brain diseases, making it a common feature of cerebral pathology.
Among the best-known biomarkers for neuroinflammation in Positron Emission Tomography (PET) research is the
18 kDa translocator protein (TSPO). This study aims to investigate the binding kinetics of a novel TSPO PETradiotracer,
[18F]LW223, in mice and specifically assess its volume of non-displaceable binding (VND) in brain as well as investigate the
use of simplified analysis approaches for quantification of [18F]LW223 PET data. Adult male mice were injected with [18F]
LW223 and varying concentrations of LW223 (0.003–0.55 mg/kg) to estimate VND of [18F]LW223. Dynamic PET imaging
with arterial input function studies and radiometabolite studies were conducted. Simplified quantification methods,
standard uptake values (SUV) and apparent volume of distribution (VTapp), were investigated. [18F]LW223 had low
VND in the brain (<10% of total binding) and low radiometabolism ( 15–20%). The 2-tissue compartment model
provided the best fit for [18F]LW223 PET data, although its correlation with SUV90–120min or VTapp allowed for [18F]
LW223 brain PET data quantification in healthy animals while using simpler experimental and analytical approaches. [18F]
LW223 has the required properties to become a successful TSPO PET radiotracer.