Achieving small molecule selectivity for ion channels can be challenging; therefore, peptide toxins have sparked considerable interest to advance both basic research and scaffold-based drug discovery. However, efficient isolation of the correctly folded peptide at a low cost is a current limitation. Recombinant expression of toxin peptides fused to a scaffold protein is an emerging strategy to overcome these production challenges, as well as enhancing in vivo stability of the toxin peptide. Here, using automated patch clamp technology, we evaluate the potency and selectivity of ten Nav1.7-selective arachnid peptide toxins, which have been fused to the C terminus (Fc region) of human IgG1. Most of the recombinant toxins tested retained potency against Nav1.7, but with reduced potency compared to the native, synthetic toxin. The four most potent recombinant toxins, which all inhibited Nav1.7 with an IC50 of 70–500 nM, were advanced to selectivity screening. Toxins were screened against a range of neuronal sodium channels (Nav1.1, Nav1.6, and Nav1.8) and cardiac sodium channel (Nav1.5). Fc-ProTx-II displayed >50-fold potency over the other tested Nav channels, as well as reproducible potency against Nav1.7 upon resynthesis and rescreening. Fc-ProTx-II demonstrated a robust reduction in excitability of mouse DRG neurons using current-clamp recordings. The recombinant toxins were generated efficiently and retained potency and selectivity against Nav1.7, substantiating this IgG1-fusion approach for producing functional antibody-toxin fusions. This approach could accelerate SAR studies, advance peptide research, and help generate new therapeutic strategies in the future.
Haworth et al. (Sun,) studied this question.