[11C]NS8880, a promising PET radiotracer targeting the norepinephrine transporter

Abstract Introduction Positron emission tomography (PET) imaging of the norepinephrine transporter (NET) is still hindered by the availability of useful PET imaging probes. The present study describes the radiosynthesis and pre-clinical evaluation of a new compound, exo-3-(6-methoxypyridin-2-yloxy)-8-H-8-azabicyclo[3.2.1]octane (NS8880), targeting NET. NS8880 has an in vitro binding profile comparable to desipramine and is structurally not related to reboxetine. Methods Labeling of NS8880 with [ 11 C] was achieved by a non-conventional technique: substitution of pyridinyl fluorine with [ 11 C]methanolate in a Boc-protected precursor. The isolated [ 11 C]NS8880 was evaluated pre-clinically both in a pig model (PET scanning) and in a rat model (μPET scanning) and compared to ( S,S )-[ 11 C]- O -methylreboxetine ([ 11 C]MeNER). Results The radiolabeling technique yielded [ 11 C]NS8880 in low ( in vivo evaluation in pig and rat revealed a rapid brain uptake of [ 11 C]NS8880 and fast obtaining of equilibrium. Highest binding was observed in thalamic and hypothalamic regions. Pretreatment with desipramine efficiently reduced binding of [ 11 C]NS8880. Conclusion Based on the pre-clinical results obtained so far [ 11 C]NS8880 displays promising properties for PET imaging of NET.