Abstract
μ-Conotoxin KIIIA, a selective blocker of sodium channels, has strong inhibitory activity against several Na(v) isoforms, including Na(v)1.7, and has potent analgesic effects, but it contains three pairs of disulfide bonds, making structural modification difficult and synthesis complex. To circumvent these difficulties, we designed and synthesized three KIIIA analogues with one disulfide bond deleted. The most active analogue, KIIIA-1, was further analyzed, and its binding pattern to hNa(v)1.7 was determined by molecular dynamics simulations. Guided by the molecular dynamics computational model, we designed and tested 32 second-generation and 6 third-generation analogues of KIIIA-1 on hNa(v)1.7 expressed in HEK293 cells. Several analogues showed significantly improved inhibitory activity on hNa(v)1.7, and the most potent peptide, 37, was approximately 4-fold more potent than the KIIIA Isomer I and 8-fold more potent than the wildtype (WT) KIIIA in inhibiting hNa(v)1.7 current. Intraperitoneally injected 37 exhibited potent in vivo analgesic activity in a formalin-induced inflammatory pain model, with activity reaching ∼350-fold of the positive control drug morphine. Overall, peptide 37 has a simplified disulfide-bond framework and exhibits potent in vivo analgesic effects and has promising potential for development as a pain therapy in the future.