Among the inhibitors of Na_v1.7, a 34-residue peptide cross-linked by three disulfide bridges, named GpTx-1 which was isolated from the venom of the tarantula spider Grammostola porteri, is a potential lead molecule for the development of a novel analgesic targeting Na_V1.7. Its analogue GpTx-1-71 of [Ala5,Phe6,Leu26,Arg28]-GpTx-1 (Figure 1) which was screened from hundreds of analogues by Amgen, exhibited exceptional Na_V1.7 IC₅₀ value of 1.6 nM and >1000x selectivity against Na_V1.4 and Na_V1.5.