Where cone snails and spiders meet: design of small cyclic sodium-channel inhibitors

A13 aa residue voltage-gated sodium channel (NaV) inhibitor peptide, Pn, containing 2 disulfide bridges was designedby using a chimeric approach. This approach was based on a common pharmacophore deduced from sequenceandsecondary structural homology of 2NaV inhibitors:Conus kinoshitai toxinIIIA, a14 residue conesnail peptidewith 3 disulfide bonds, and Phoneutria nigriventer toxin 1, a 78 residue spider toxinwith 7 disulfide bonds. As with the parent peptides, this novel NaV channel inhibitor was active on NaV1.2. Through the generation of 3 series of peptide mutants, we investigated the role of key residues and cyclization and their influence on NaV inhibition and subtype selectivity. Cyclic PnCS1, a 10 residue peptide cyclized via a disulfide bond, exhibited increased inhibitory activity toward therapeutically relevant NaV channel subtypes, including NaV1.7 and NaV1.9, while displaying remarkable serumstability. These peptides represent the first and the smallest cyclic peptideNaV modulators to date and are promising templates for the development of toxin-based therapeutic agents.