Poster Presentation The 46th Lorne Conference on Protein Structure and Function 2021

Engineering an optimized analgesic from the NaV1.7 selective tarantula venom peptide Pn3a (#406)

Alexander Mueller 1 , Quentin Kaas 1 , Zoltan Decan 1 , Jennifer Deuis 1 , Irina Vetter 1 2
  1. Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
  2. School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4102, Australia

Pain is the leading cause of disability in the developed world but remains poorly treated. Existing painkillers suffer from poor tolerability and lack of efficacy[1]. One of the most promising targets for pain treatment is the voltage-gated sodium channel (NaV) isoform NaV1.7. Genetic studies revealed a key role of NaV1.7 in pain with gain-of-function and loss-of-function mutations leading to pain syndromes and insensitivity to pain, respectively[2,3]. We identified the tarantula venom peptide μ-theraphotoxin-Pn3a (Pn3a) as promising NaV1.7 blocker with effective analgesic properties[4,5]. This project identifies the pharmacophore of Pn3a and led to Pn3a-analogues with improved analgesic activity in pre-clinical models of pain suitable as lead compounds for painkiller development.

Solid-phase peptide synthesis was used to produce Pn3a-analogues. Fluorescence imaging and patch-clamp experiments were performed to characterize potencies at hNaV1.1-hNaV1.8. Surface plasmon resonance was used to examine peptide-lipid bilayer interactions. Improved analogues were tested in mouse models of NaV1.7-mediated pain and post-surgical pain.

Mutations of some basic and hydrophobic residues decreased inhibition of NaV1.7 in vitro. Mutations of several acidic residues increased potency with two substitutions showing improved selectivity for NaV1.7 and higher membrane affinity. Particularly, Pn3a[D8N] was more potent and efficacious in vivo than Pn3a in both pain models, without causing side-effects.

Pn3a is a unique pharmacological tool to define the role of NaV1.7 in pain pathways due to its high subtype selectivity. The obtained information on the pharmacophore of Pn3a can be utilized to design Pn3a-analogues with desired pharmacodynamic and pharmacokinetic properties. Indeed, analogues with improved properties were identified with Pn3a[D8N] showing improved analgesic efficacy in vivo, making it a promising lead candidate for further drug development. These results will guide future rational design of potent and selective NaV1.7 inhibitors as more efficacious and safer painkillers.

  1. Gan, T.J., et al., Incidence, patient satisfaction, and perceptions of post-surgical pain: results from a US national survey. Curr Med Res Opin, 2014. 30(1): p. 149-60.
  2. Fertleman, C.R., et al., SCN9A mutations in paroxysmal extreme pain disorder: allelic variants underlie distinct channel defects and phenotypes. Neuron, 2006. 52(5): p. 767-74.
  3. Cox, J.J., et al., An SCN9A channelopathy causes congenital inability to experience pain. Nature, 2006. 444(7121): p. 894-8.
  4. Deuis, J.R., et al., Pharmacological characterisation of the highly NaV1.7 selective spider venom peptide Pn3a. Sci Rep, 2017. 7: p. 40883.
  5. Mueller, A., et al., Antiallodynic effects of the selective NaV1.7 inhibitor Pn3a in a mouse model of acute postsurgical pain: evidence for analgesic synergy with opioids and baclofen. Pain, 2019. 160(8):1766-80