Discovery and biological evaluation of 5-aryl-2-furfuramides, potent and selective blockers of the Nav1.8 sodium channel with efficacy in models of neuropathic and inflammatory pain

Subtype-selective targeting of voltage-gated sodium channels

Voltage-gated sodium channels are key to the initiation and propagation of action potentials in electrically excitable cells. Molecular characterization has shown there to be nine functional members of the family, with a high degree of sequence homology between the channels. This homology translates into similar biophysical and pharmacological properties. Confidence in some of the channels as drug targets has been boosted by the discovery of human mutations in the genes encoding a number of them, which give rise to clinical conditions commensurate with the changes predicted from the altered channel biophysics. As a result, they have received much attention for their therapeutic potential. Sodium channels represent well-precedented drug targets as antidysrhythmics, anticonvulsants and local anaesthetics provide good clinical efficacy, driven through pharmacology at these channels. However, electrophysiological characterization of clinically useful compounds in recombinant expression systems shows them to be weak, with poor selectivity between channel types. This has led to the search for subtype-selective modulators, which offer the promise of treatments with improved clinical efficacy and better toleration. Despite developments in high-throughput electrophysiology platforms, this has proven very challenging. Structural biology is beginning to offer us a greater understanding of the three-dimensional structure of voltage-gated ion channels, bringing with it the opportunity to do real structure-based drug design in the future. This discipline is still in its infancy, but developments with the expression and purification of prokaryotic sodium channels offer the promise of structure-based drug design in the not too distant future.

Sodium channel blockers for the treatment of neuropathic pain

Drugs that block voltage-gated sodium channels are efficacious in the management of neuropathic pain. Accordingly, this class of ion channels has been a major focus of analgesic research both in academia and in the pharmaceutical/biotechnology industry. In this article, we review the history of the use of sodium channel blockers, describe the current status of sodium channel drug discovery, highlight the challenges and hurdles to attain sodium channel subtype selectivity, and review the potential usefulness of selective sodium channel blockers in neuropathic pain.

Gene therapy for pain

BACKGROUND

Management of chronic pain remains a challenge in spite of the numerous drugs either approved or still in development. Apart from inadequacy of relief, there are concerns about adverse effects and addiction in the case of drugs such as opioids. Gene therapy is being investigated for improving management of pain.

OBJECTIVE

To addresses the rationale of gene therapy for treatment of pain and its advantages over drugs. The prospects of translation of these techniques from experimental animals to clinical use are discussed.

METHODS

The review is based on the available literature and is confined to experimental work, as there are no approved therapies in this category.

RESULTS/CONCLUSION

A number of promising gene therapies as well as antisense- and RNA interference-based approaches have been identified. These provide targeted approaches to delivery of antinociceptive molecules or interruption of pain pathways without subjecting the patient to systemic toxicity of drugs. Some of these approaches are aimed at correcting the underlying pathology of the diseases (e.g., treating degenerative joint diseases causing pain). Management of neuropathic pain is a challenge and a number of studies are addressing it. Overall the future of gene therapy for pain is promising.

Discovery of potent furan piperazine sodium channel blockers for treatment of neuropathic pain

The synthesis and pharmacological characterization of a novel furan-based class of voltage-gated sodium channel blockers is reported. Compounds were evaluated for their ability to block the tetrodotoxin-resistant sodium channel Na(v)1.8 (PN3) as well as the Na(v)1.2 and Na(v)1.5 subtypes. Benchmark compounds from this series possessed enhanced potency, oral bioavailability, and robust efficacy in a rodent model of neuropathic pain, together with improved CNS and cardiovascular safety profiles compared to the clinically used sodium channel blockers mexiletine and lamotrigine.