The NGF System and its interplay with endocannabinoid signalling, from peripheral sensory terminals to the brain: new targets for the development of next generation drugs for neuropathic pain

PAINCAGE will pursue the following specific S&T by a cross-disciplinary and modular work-program:

WP1 – Understand the role of the individual components of the NGF target system (NGF, proNGF, TrkA, p75NTR, sortilin) in the signaling and regulation of different forms of NP with the neurotrophic, neuropathic and inflammatory components including OA.
WP2 – Dissect endocannabinoid signaling (ligands and receptor systems) in relation to the NGF pain-related signaling pathways in NP.
WP3 – Validate the NGF involvement in NP by the development and pharmacological/behavioral characterization of insensitivity to pain in new transgenic, pain insensitive, mouse models (HSAN IV and V).
WP4 – Analyze epigenetic mechanisms in NP and OA by focusing on the long-term gene expression changes during NP onset and NGF-targeting analgesic treatments in NP and OA.
WP5 – Control NP and OA onset, progression and perception by pharmacological treatment with antiNGF, antiTrkA and p75-Fc (NGF scavenger) as well as painless NGFR100. Transgenic models will be used to define specific roles of CB1R, TRPV1, CB2R and sortilin in NP.
WP6 – Analyze the safety issues related to the antiNGF therapy and unwanted side effects.
WP7 – Optimize the structure of lead drug candidates for NP.
WP8 – Identify and validate pain related biomarkers and druggable targets in humans, to improve patient stratification.

PAINCAGE focuses on two molecular systems of emerging importance, the NGF and the EC system. Unifying the two systems and studying their functional interactions, at different levels of the pain transmission and perception pathways, is a highly innovative approach.

The input to the project is represented by:

  • a set of existing candidate targets (e.g. sortilin, TRPV1, CBRs) belonging to the NGF and the EC system,
  • a set of existing lead biological drugs (alfaD11 anti NGF, antiTrkAMNAC13, p75NTR-Fc),
  • extensive, and state-of-the-art knowledge, expertise, models and reagents on the NGF and EC systems, both of which are crucially involved in NP.

These inputs will be feed into the first block of Work packages (WP1, WP2 and WP3), that deal with improving the understanding of the NGF (WP1 and WP3) and the EC (WP2) systems in NP, with a particular focus on the interactions between the two.

This first block of WPs, whose activities will be completed by and large by the second year of the project, feeds into WP4, that is devoted to exploiting the understanding gained in the previous block of WPs, to identify and validate new NP- and OA-related targets. This target discovery activity will be particularly focussed on the epigenetic regulation of gene expression during long-lasting analgesic protocols induced by antiNGF and antiTrkA treatments.

WP4 will provide, as an output, new targets for future development, possibly related to the epigenetics regulation in pain, a theme of emerging importance, as well as a validation of sortilin as a target for NP and OA. As a second output, WP4 feeds into WP8, whose activities are also fuelled by the availability of large numbers of DNA, tissue or fluid samples, from NP-affected patients. WP8 is dedicated to the identification of biomarkers, and will provide, as an output, new candidate biomarkers for patient stratification. The bulk of WP8 activities will be therefore carried out in the second part of the project.

The information and results obtained in the first block of WPs (WP1, WP2 and WP3) will also feed a block of WPs (WP5, WP6 and WP7) centered on controlling pain. In particular, the efficacy of antiNGF, antiTrkA and p75NTR-FC in treating, as well as in preventing pain onset in NP and OA models will be compared (WP5). Also, combination treatments with compounds from the NGF and the EC system will be investigated. The same treatments will be assessed in terms of safety endpoints, with a particular focus on those endpoints that have emerged as critical in clinical antiNGF trials, or as potential liabilities of the NGF system as a target (such as liabilities related to possible neurological effects in the central nervous system). WP7 in this block will deal with the structural determination of complexes between NGF and antiNGF and of TrkAECD and antiTrkA, building on the available high resolution structures of the corresponding antibodies. The crystallographic structure of painless NGFR100 will also be determined. Results from WP7 will provide the necessary structural information for the optimization of these lead drug candidates and for the structural design (in future projects) of small-molecule drugs inhibiting NGF and TrkA.

The overall output from this block of WPs will be a set of well-characterized and validated lead therapeutic compounds (p75NTR-Fc and NGFR100) ready to enter clinical trials for NP and OA indications.