Jennifer R. Deuis 1 , Zoltan Dekan 1 , Joshua S. Wingerd 1 , Jennifer J. Smith 1 , Nehan R. Munasinghe 2 , Rebecca F. Bhola 2 , Wendy L. Imlach 2 , Volker Herzig 1 , David A. Armstrong 3 , K. Johan Rosengren 3 , Frank Bosmans 4 , Stephen G. Waxman 5 , Sulayman D. Dib-Hajj 5 , Pierre Escoubas 6 , Michael S. Minett 7 , Macdonald J. Christie 2 , Glenn F. King 1 , Paul F. Alewood 1 , Richard J. Lewis 1 , John N. Wood 7 , Irina Vetter a , 1 , 8
20 January 2017
Human genetic studies have implicated the voltage-gated sodium channel Na V1.7 as a therapeutic target for the treatment of pain. A novel peptide, μ-theraphotoxin-Pn3a, isolated from venom of the tarantula Pamphobeteus nigricolor, potently inhibits Na V1.7 (IC 50 0.9 nM) with at least 40–1000-fold selectivity over all other Na V subtypes. Despite on-target activity in small-diameter dorsal root ganglia, spinal slices, and in a mouse model of pain induced by Na V1.7 activation, Pn3a alone displayed no analgesic activity in formalin-, carrageenan- or FCA-induced pain in rodents when administered systemically. A broad lack of analgesic activity was also found for the selective Na V1.7 inhibitors PF-04856264 and phlotoxin 1. However, when administered with subtherapeutic doses of opioids or the enkephalinase inhibitor thiorphan, these subtype-selective Na V1.7 inhibitors produced profound analgesia. Our results suggest that in these inflammatory models, acute administration of peripherally restricted Na V1.7 inhibitors can only produce analgesia when administered in combination with an opioid.