Kv7.2/7.3 Activators for the Treatment of Epilepsy Disorders

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Epilepsy is the oldest known and most common serious, chronic neurological disorder that is characterized by recurrent seizures. It currently affects 65 million people worldwide, including 2.3 million adults and nearly 470,000 children in the United States. People with epilepsy suffer from seizure-related disabilities, depression and anxiety and have increased mortality compared to the general population. Over the last few decades there has been considerable effort and success to bringing new anti-seizure drugs to market. Despite the availability of several newer medications, approximately 30% of patients are treatment-resistant. Furthermore, anti-seizure drug therapies are associated with significant adverse effects and often require careful titration to achieve efficacy while minimizing disabling side effects. Neuronal potassium channels play a key role in regulating neuronal activities. Kv7.1-7.5 channels are one family of voltage-gated potassium channels critical in maintaining the resting membrane potential of excitable cells and neuronal Kv7 channels act to dampen repetitive firing of neurons. Additional interest in Kv7.2 and Kv7.3 channels come from the discovery of mutations in the Kv7.2 or Kv7.3 genes found to be associated with some inherited forms of epilepsy. Thus small molecule drugs that activate the opening of Kv7.2 and Kv7.3 channels have potential to treat many neuronal hyperexcitability disorders, including epilepsy. A recently approved anti-seizure drug, ezogabine, acts primarily by opening Kv7.2-7.5 channels with activity on the GABAA system as well. However, in addition to tolerability issues, ezogabine use has been associated with serious adverse effects that have limited its utility, including retinal and skin discoloration that are likely linked to ezogabine’s chemical instability rather than its Kv7 activities. The goal of this Knopp Biosciences program is to design and develop a Kv7.2/7.3 activator that fully realizes the potential of this target to address the unmet medical need of treatment-resistant epilepsy patients and difficult-to-treat generalized epilepsy syndromes. Such a compound will possess a dramatically improved tolerability and safety profile over that of ezogabine not only via improved intrinsic chemical stability characteristics, but also due to reduced Kv7.4 activity so as to avoid side effects that may be caused by opening Kv7.4 channels present in blood vessels and smooth muscle. In addition, the next generation Kv7.2/7.3 activator will remove activity on the GABAA channels. To accomplish this, Knopp has developed a variety of in vitro screening assays using Kv7-expressing cell lines and primary neurons. These data, along with those generated from a battery of in vitro assays testing for metabolism and drug-like properties, will be used to select compounds for study in acute and chronic animal models of epilepsy. We will also evaluate the tolerability of compounds in animals to identify drug candidates that show the best therapeutic window for efficacy with minimal side effects.