As the first in a new class of non-opioid drugs, ω-Conotoxin MVIIA was approved for the management of severe chronic pains in patients who are unresponsive to opioid therapy. Unfortunately, clinical application of MVIIA is severely limited due to its poor ability to penetrate the blood-brain barrier (BBB), reaching the central nervous system (CNS). In the present study, we have attempted to increase MVIIA’s ability to cross the BBB via a fusion protein strategy. Our results showed that when the TAT-transducing domain was fused to the MVIIA C-terminal with a linker of varied numbers of glycine, the MVIIA-TAT fusion peptide exhibited remarkable ability to cross the bio-membranes. Most importantly, both intravenous and intranasal administrations of MVIIA-TAT in vivo showed therapeutic efficacy of analgesia. Compared to the analgesic effects of intracerebral administration of the nascent MVIIA, these systemic administrations of MVIIA-TAT require higher doses, but have much prolonged effects. Taken together, our results showed that TAT conjugation of MVIIA not only enables its peripheral administration, but also maintains its analgesic efficiency with a prolonged effective time window. Intranasal administration also rendered the MVIIA-TAT advantages of easy applications with potentially reduced side effects. Our results may present an alternative strategy to improve the CNS accessibility for neural active peptides.

ω -Conotoxins inhibit N-type voltage-gated calcium (Ca V 2.2) channels and exhibit efficacy in attenuating neuropathic pain but have a low therapeutic index. Here, we synthesized and characterized a novel ω -conotoxin, Bu8 from Conus bullatus , which consists of 25 amino acid residues and three disulfide bridges. Bu8 selectively and potently inhibits depolarization-activated Ba 2+ currents mediated by rat Ca V 2.2 expressed in HEK293T cells (IC 50 = 89 nmol/L). Bu8 is two-fold more potent than ω -conotoxin MVIIA, a ω -conotoxin currently used for the treatment of severe chronic pain. It also displays potent analgesic activity in animal pain models of hot plate and acetic acid writhing but has fewer side effects on mouse motor function and lower toxicity in goldfish. Its lower side effects may be attributed to its faster binding rate and higher recovery ratios. The NMR structure demonstrates that Bu8 contains a small irregular triple β -strand. The structure–activity relationships of Bu8 Ala mutants and Bu8/MVIIA hybrid mutants demonstrate that the binding mode of Ca V 2.2 with the amino acid residues in loop 1 and loop 2 of Bu8 is different from that of MVIIA. This study characterizes a novel, more potent ω -conotoxin and provides new insights for designing Ca V 2.2 antagonists.