Investigational new drugs for focal epilepsy.

For more than 30 years, antiepileptic drug development has been based on specific assumptions regarding the neurobiology of epilepsy but all marketed drugs have not changed the proportion of drug refractory patients. It is, therefore, evident that new molecular targets need to be identified. Advances in neurobiology and molecular pharmacology are bringing into the epilepsy field new neurochemical functions such as those modulated by cannabinoid, serotonin, melatonin and galanin receptors. Among all the different compounds, the melatonin type 3 receptor agonist beprodone and cannabidiol are those at the more advanced stage of development. Interestingly, despite the structural analogies with tetrahydrocannabinol, the anticonvulsant activity of cannabidiol is not mediated by an interaction with cannabinoid receptors. Neurosteroids represent another remarkable class of drugs, and among them, ganaxolone is at the most advanced stage of development. Furthermore, for the first time, potential disease-modifying agents and techniques are entering the epilepsy market. Rapalogues such as everolimus and the antibiotic minocycline are currently under development for specific epileptic syndromes like tuberous sclerosis or Angelman syndrome. Finally, optogenetics, though still at an early stage of development, represents a futuristic therapeutic strategy for drug-refractory epilepsy.