Stroke afflicts nearly 800,000 Americans each year and often results in cognitive impairment or death, leading to over $35 billion in annual healthcare costs in the United States. Neurexis Therapeutics is developing a neuroprotective drug, tatCN19o, for the prevention of brain damage following stroke. TatCN19o is a cell-penetrating peptide that inhibits the Ca2+/calmodulin(CaM)-dependent kinase, CaMKII. In the brain, CaMKII undergoes finely-tuned regulation to support cognition, learning, and memory1. CaMKII also mediates neuronal cell death after conditions of ischemia2 (reduced oxygen supply by reduced blood flow). TatCN19o belongs to a class of CN inhibitors derived from a naturally occurring CaMKIIinhibitory protein, CaM-KIIN. Like endogenous CaM-KIIN, tatCN19o inhibits CaMKII activity and competes with binding to NMDA-type glutamate receptors3-6. These mechanisms mediate neuroprotection by tatCN19o, in rodent5,7 and large animal6 models of cerebral ischemia. Compared to the inhibitory region of CaM-KIIN, tatCN19o is nearly 1000x more potent, with an in vitro Ki of ~0.1 nM5 and in vivo neuroprotection following cerebral ischemia achieved by doses as low as 0.01 mg/kg5.

TatCN19o is comprised of two domains: a tat leader sequence to enable cell- and brain- penetration and the CN19o efficacious region. CN19o was tested for effects on other CaM kinase family members (CaMKIV, DAPK1, AMPK) and other basophilic multifunctional kinases (PKA, PKC). Even at >10,000x IC50 for CaMKII (5 uM), CN19o did not significantly affect the activity of these other kinases8. Autonomous CaMKII activity can be generated by T286 autophosphorylation and is thought to be of special importance for ischemic neuronal damage5. CN19o inhibits both Ca2+/CaM-stimulated and autonomous CaMKII equally well9. It also inhibits rodent and human CaMKII equally well.The binding site for tatCN19o on CaMKII only becomes accessible upon CaMKII activation, making the drug an “active kinase inhibitor.” Together, these properties make tatCN19o an ideal CaMKII inhibitor for targeting cerebral ischemia, including stroke.




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