Targeting microglia CB2 Receptors with novel multisite ligands: a multidisciplinary and translational study for the identification of an innovative multiple sclerosis therapy

Multiple sclerosis (MS) is a highly disabling chronic inflammatory disease that causes demyelination and axonal damage, leading to neurodegeneration and axonal loss. Current MS therapy, based on the use of immunomodulatory and anti-inflammatory agents, is unable to prevent disease progression and worsening of symptoms. A dysregulation of the cannabinoid system has been reported to occur in MS and the approval of nabiximols, a mixture of Δ9-tetrahydrocannabinol (THC), a cannabinoid receptor 1 (CB1) and CB2 agonist, and cannabidiol (CBD), a non-psychotropic cannabinoid, for the treatment of spasticity and neuropathic pain in MS, have brought cannabinoid-based therapeutics into the limelight. However, undesirable central effects resulting from CB1 activation limit the clinical use of CB1 agonists. Recent studies showed an increased CB2-immunoreactive microglia in MS patients, raising new possibilities for CB2 targeting as a safer and efficient therapeutic perspective. Thus, the aim of this research project is to restore the cannabinoid signaling by identifying novel CB2 modulators to simultaneously interact with orthosteric and allosteric binding sites within the CB2 pocket. This innovative intervention, by exploiting the intertwining and multidisciplinary nature of the research units, would be aimed at attenuating both MS-associated symptomatology and disease progression. Different approaches, based on combination or multisite interventions, will be investigated. Combinations of CBD with a CB2-selective agonist (CB2ago) of natural (cannabis-derived terpene) or synthetic origin will be tested and screened for anti-neuroinflammatory and neuroprotective activity by functional and cell biology assays, then tested for efficacy on relieving disability and pain in an MS animal model. The intranasal delivery will be used to take advantage of the nose-to-brain pathway to foster brain penetration. The best performing CBD/CB2ago combination will be used for the in silico generation of a tridimensional pharmacophoric model, useful for the virtual screening of CB2 multisite modulators (CB2ms) from libraries of drug-like compounds and drugs approved for clinical use. This drug repurposing approach will allow for short-term clinical use, increasing the possible application potentiality. In parallel, this study will also assess the role of microglial CB2 as a key event in the pathogenesis of MS. Extracellular vesicles (EVs) of microglial origin will be isolated from blood samples of MS patients to detect changes in CB2 expression related to disability levels, thus improving the current knowledges on central alteration associated with MS. The most promising CBD/CB2ago and CB2ms will be tested on EVs to define their potential clinical value. This multidisciplinary research will promote a novel intervention to slow disease progression further to palliate symptoms by multisite CB2 modulation with a view to increasingly effective and safe MS therapy.