Discovery of (phenoxy-2-hydroxypropyl)piperidines as a novel class of voltage-gated sodium channel 1.7 inhibitors

N-Aryl Indoles as a Novel Class of Potent NaV1.7 Inhibitors

A novel class of potent NaV1.7 inhibitors has been discovered. The replacement of diaryl ether in compound I was investigated to enhance mouse NaV1.7 inhibitory activity, which resulted in the discovery of N-aryl indoles. The introduction of the 3-methyl group is crucial for high NaV1.7 in vitro potency. The adjustment of lipophilicity led to the discovery of 2e. Compound 2e (DS43260857) demonstrated high in vitro potencies against both human and mouse NaV1.7 with high selectivity over NaV1.1, NaV1.5, and hERG. In vivo evaluations revealed 2e demonstrating potent efficacy in PSL mice with excellent pharmacokinetics.

Inhibition of NaV1.7: the possibility of ideal analgesics

The selective inhibition of Na_V1.7 is a promising strategy for developing novel analgesic agents with fewer adverse effects. Although the potent selective inhibition of Na_V1.7 has been recently achieved, multiple Na_V1.7 inhibitors failed in clinical development. In this review, the relationship between preclinical in vivo efficacy and Na_V1.7 coverage among three types of voltage-gated sodium channel (VGSC) inhibitors, namely conventional VGSC inhibitors, sulphonamides and acyl sulphonamides, is discussed. By demonstrating the PK/PD discrepancy of preclinical studies versus in vivo models and clinical results, the potential reasons behind the disconnect between preclinical results and clinical outcomes are discussed together with strategies for developing ideal analgesic agents.

Chemical Synthesis, Proper Folding, Nav Channel Selectivity Profile and Analgesic Properties of the Spider Peptide Phlotoxin 1

Phlotoxin-1 (PhlTx1) is a peptide previously identified in tarantula venom (Phlogius species) that belongs to the inhibitory cysteine-knot (ICK) toxin family. Like many ICK-based spider toxins, the synthesis of PhlTx1 appears particularly challenging, mostly for obtaining appropriate folding and concomitant suitable disulfide bridge formation. Herein, we describe a procedure for the chemical synthesis and the directed sequential disulfide bridge formation of PhlTx1 that allows for a straightforward production of this challenging peptide. We also performed extensive functional testing of PhlTx1 on 31 ion channel types and identified the voltage-gated sodium (Na_v) channel Na_v1.7 as the main target of this toxin. Moreover, we compared PhlTx1 activity to 10 other spider toxin activities on an automated patch-clamp system with Chinese Hamster Ovary (CHO) cells expressing human Na_v1.7. Performing these analyses in reproducible conditions allowed for classification according to the potency of the best natural Na_v1.7 peptide blockers. Finally, subsequent in vivo testing revealed that intrathecal injection of PhlTx1 reduces the response of mice to formalin in both the acute pain and inflammation phase without signs of neurotoxicity. PhlTx1 is thus an interesting toxin to investigate Na_v1.7 involvement in cellular excitability and pain.