Molecular targets versus models for new antiepileptic drug discovery.

Animal models have played a key role in the discovery and characterization of all marketed antiepileptic drugs (AED). The conventional wisdom is that the standard animal screening models are becoming obsolete because they fail to identify compounds that act in mechanistically new ways and as a result do not offer therapeutic advantages over presently available agents. In fact, far from only detecting me-too drugs, the models often uncover compounds with distinctive profiles of activity in various types of epilepsy and in addition have unexpected efficacy in non-epilepsy conditions, such as neuropathic pain, bipolar disorder, and migraine. Moreover, the animal models-because they are unbiased with respect to mechanism-provide an opportunity to uncover drugs that act in new ways and through new targets, such as alpha2delta and SV2A. In vitro testing is not likely to replace screening in animal models because in vitro systems cannot model the specific pharmacodynamic actions required for seizure protection, and do not assess bioavailability and brain accessibility.