Antiepileptic drug discovery: lessons from the past and future challenges

Historically, most antiepileptic drugs (AEDs) have been discovered either by serendipity, or the screening of compounds using acute seizure models. However, an increasing understanding of the molecular mechanisms underlying epileptogenesis has led to more rational approaches to drug discovery, which have focused on either enhancing inhibitory gamma-amino butyric acid (GABA)-ergic, or antagonizing excitatory glutamatergic, neurotransmission. Unfortunately, AEDs generated using such strategies have poor efficacy and safety profiles, as they interfere with normal cell processes, while ignoring the complex underlying pathophysiology of epilepsy. Recently, however, the use of new epilepsy models has led to the discovery of levetiracetam, an AED with a truly unique mechanism of action, devoid of anticonvulsant activity in normal animals, but with potent seizure suppression in genetic and kindled chronic epilepsy models, and an unusually high safety margin. The recent identification of brivaracetam and seletracetam, which optimize this unique mechanism of action, may further improve the medical management of epilepsy. The experience with levetiracetam, brivaracetam and seletracetam reveals that new experimental epilepsy models can detect AEDs possessing a unique mechanism of action and thereby target the future challenge of providing clinicians novel additions to the current armamentarium of AEDs.