Testing the effects of a selective calpain-2 inhibitor on spontaneous recurrent seizures in mouse models of epilepsy

Abstract Epilepsy is the most prevalent neurological diseases after migraines. Current antiepileptic drug treatments mainly attempt to reduce excitation or enhance inhibition in order to control seizures. Unfortunately, such therapeutics result in a number of undesirable side-effects, and demonstrate limited efficacy against drug- resistant cases of epilepsy. So far, no treatment has been developed as an anti-epileptogenic agent, in part because of the limited understanding of the processes involved in the development of epilepsy. It is generally accepted that up to 50% of all epileptic patients become epileptic as a result of a triggering initial injury such as status epilepticus, stroke or traumatic brain injury. This initial triggering injury has been postulated to activate a cascade of events leading to further seizures, increased brain damage and self-propagation. Intranasal delivery of a variety of anti-epileptic drugs is increasingly used, as it provides significant advantages over traditional delivery routes. These include increased efficacy, decreased side-effects and increased patient compliance, suggesting that novel treatments could benefit from this mode of administration. Calpains are a family of soluble calcium-dependent proteases, which have been implicated in epilepsy since they are activated by seizures and participate in neuronal damage. Recent studies have also indicated that during early epileptogenesis, seizure occurrence, calpain activity and neuronal damage are correlated, and that treatment with a non-selective calpain inhibitor reduces the development of spontaneous recurrent seizures (SRSs) in the pilocarpine model of epilepsy in rats. Our laboratory has demonstrated that calpain-1 and calpain- 2, two of the major calpain isoforms in the brain, have opposite functions in the brain. We have also found that calpain-2 conditional knock-out mice with calpain-2 deletion in excitatory neurons from the forebrain show normal seizure activity following injections of repeated low doses of kainic acid (KA) but exhibit no brain inflammation, degeneration and impairment in hippocampus-dependent learning 7 days after seizures. Similar protective results were obtained when wild-type mice were treated daily and for seven days after seizures with a selective calpain-2 inhibitor, NA-112. These results strongly support the novel hypothesis that calpain-2 might represent a potential therapeutic target to prevent various pathological consequences of seizures. This Phase I STTR is directed at determining whether intranasal administration of NA-112, can prevent the appearance of SRSs or reduce their frequency as well as prevent the various manifestations of neuropathology (brain inflammation, neurodegeneration and cognitive impairment) in two mouse models of epilepsy, the repeated low doses of kainic acid (KA) or of pilocarpine models. In Phase II of this STTR, we will further pursue the development of intranasal delivery of NA-112 as an anti-epileptogenic drug. NeurAegis is a small biotech company focusing on the development of selective calpain-2 inhibitors for the treatment of acute neuronal injury, including traumatic brain injury and repeated concussions. This proposal is directed at expanding the potential applications of these calpain-2 inhibitors by determining whether they could also be developed as potential therapeutic treatment for epilepsy.