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Voltage-gated sodium (Na V) channels play crucial roles in a range of (patho)physiological processes. Much interest has arisen within the pharmaceutical industry to pursue these channels as analgesic targets following overwhelming evidence that Na V channel subtypes Na V 1.7–Na V 1.9 are involved in nociception. More recently, Na V 1.1, Na V 1.3 and Na V 1.6 have also been identified to be involved in pain pathways. Venom-derived disulfide-rich peptide toxins, isolated from spiders and cone snails, have been used extensively as probes to investigate these channels and have attracted much interest as drug leads. However, few peptide-based leads have made it as drugs due to unfavourable physiochemical attributes including poor in vivo pharmacokinetics and limited oral bioavailability. The present work aims to bridge the gap in the development pipeline between drug leads and drug candidates by downsizing these larger venom-derived Na V inhibitors into smaller, more "drug-like" molecules. Here, we use molecular engineering of small cyclic peptides to aid in the determination of what drives subtype selectivity and molecular interactions of these downsized inhibitors across Na V subtypes. We designed a series of small, stable and novel Na V probes displaying Na V subtype selectivity and potency in vitro coupled with potent in vivo analgesic activity, involving yet to be elucidated analgesic pathways in addition to Na V subtype modulation. [ABSTRACT FROM AUTHOR]