Abstract

Introduction. The neurotrophins including nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) regulate neuronal survival, differentiation and plasticity. Decreased NGF-signalling in the central nervous system (CNS) plays a role in Alzheimer’s disease (AD), whereas increased BDNF signalling improves synaptic plasticity. The large unmet medical need in AD strongly supports the development of positive modulators of neurotrophin signalling as cognitive enhancers for the treatment of AD. The role of NGF/TrkA in pain signalling is well validated. Targeting the TrkA receptor with a selective negative allosteric modulator (NAM) might offer a more selective way of disrupting the NGF-signalling than the existing analgesics.

 Methods. Active compounds were identified by screening a compound library using the PathHunter U2OS-hTrkA/SHC1-p75 cell line. Lead optimization of chemical series led to the discovery of novel positive or negative modulators.

Results. The Trk-PAM’s act by increasing the catalytic efficiency of the kinase. The optimization work led to the identification of potent and selective TrkA-modulators. The modulation of the Trk-receptors was, for both Trk-PAM’s and TrkA-NAM’s, dependent on the full-length receptor since no effect of the modulators were seen when using a biochemical Trk-kinase assay Conclusion. The PathHunter cell-based assay is a suitable assay for identifying compounds that act as allosteric modulators of Trk-receptors. The use of a biochemical kinase assay using the intracellular kinase domain could not replicate the findings from the cell-based assay, suggesting that correct modulation only could be obtained when using full-length receptors.