We are pleased to provide a link to our following published research with Janssen Pharmaceuticals. The story involves development of a peptide originally derived from the venom of the tarantula Haplopelma schmidti for potential treatment of chronic pain. This peptide toxin is known as Huwentoxin- IV (HwTX-IV) and is a relatively potent and somewhat selective modulator of the Nav1.7channel, a potential target for modulating chronic pain. Our recent publication in J. Biol. Chem. describes our efforts at improving the selectivity of this toxin towards this pain target. Please read the abstract below and/or click on the hyperlink to navigate to the article.
Pain is a significant public health burden in the United States and current treatment approaches rely heavily on opioids, which often have limited efficacy and can lead to addiction. In humans, functional loss of the voltage-gated sodium channel Nav1.7 leads to pain insensitivity without deficits in the central nervous system. Accordingly, discovery of a selective Nav1.7 antagonist should provide an analgesic without abuse liability and an improved side-effect profile. Huwentoxin-IV, a component of tarantula venom, potently blocks sodium channels and is an attractive scaffold for engineering a Nav1.7-selective molecule. To define the functional impact of alterations in huwentoxin-IV sequence we produced a library of 373 point mutants and tested them for Nav1.7 and Nav1.2 activity. We then combined favorable individual changes to produce combinatorial mutants that showed further improvements in Nav1.7 potency (Glu-1-Asn, Glu-4-Asp, Tyr-33-Trp, Gln-34-Ser – Nav1.7 pIC50 = 8.1 ± 0.08) and increased selectivity over other Nav isoforms (Glu-1-Asn, Arg-26-Lys, Gln-34-Ser, Gly-36-Ile, Nav1.7 pIC50 = 7.2 ± 0.1, Nav1.2 pIC50 = 6.1 ± 0.18, Nav1.3 pIC50 = 6.4 ± 1.0), Nav1.4 – Inactive at 3 µM, and Nav1.5 – Inactive at 10µM). We also substituted non-coded amino acids at select positions in huwentoxin-IV. Based on these results, we identify key determinants of huwentoxin’s Nav1.7 inhibition and propose a model for huwentoxin-IV’s interaction with Nav1.7. These findings uncover fundamental features of huwentoxin involved in Nav1.7 blockade, provide a foundation for additional optimization of this molecule, and offer a basis for the development of a safe and effective analgesic.