Do spiroindolines have the potential to replace vesamicol as lead compound for the development of radioligands targeting the vesicular acetylcholine transporter?

Publication date: Available online 18 March 2017
Source:Bioorganic & Medicinal Chemistry
Author(s): Marcel Lindemann, Winnie Deuther-Conrad, Rares Moldovan, Kondapalli Venkata Gowri Chandra Sekhar, Peter Brust, Barbara Wenzel
The vesicular acetylcholine transporter (VAChT) is an important target for in vivo imaging of neurodegenerative processes using positron-emission-tomography (PET). So far the development of VAChT PET radioligands is based on the single known lead compound vesamicol. In this study we investigated a recently published spiroindoline based compound class (Sluder et al. 2012), which was suggested to have potential in the development of VAChT ligands. Therefore, we synthesized a small series of N,N-substituted spiro[indoline-3,4'-piperidine] derivatives and determined their in vitro binding affinities toward the VAChT. In order to investigate the selectivity, the off-target binding toward σ1 and σ2 receptors were determined. The compounds possessed VAChT affinities with Ki values in the range of 39 to 376 nM. Binding affinities toward the σ1 and σ2 receptors are in a similar range indicating that the strong structural difference between the spiroindolines and vesamicol did not improve the selectivity. The observed potential to additionally bind to σ receptors let us assume that the herein investigated spiroindolines are not suitable to replace vesamicol as lead compound for the development of VAChT ligands.

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