Synaptic vesicle protein 2 (SV2) is a membrane glycoprotein found only in the secretory vesicles of neural and endocrine cells. Three isoforms of this 90-kDa protein exist: SV2A, SV2B, and SV2C, of which, SV2A is the most widely distributed. The molecular mechanism by which these proteins regulate secretion is not clear[1]. Based on predicted structure and amino acid sequences, the SV2 proteins belong to the major facilitator superfamily of transporter proteins, with a high degree of homology with glucose transporters (GLUTs) and plasma membrane transporters for neurotransmitters[2]. Other studies demonstrated that SV2A deletion results in reduced action potential-dependent release of the inhibitory neurotransmitter GABA in the hippocampus. These observations have given rise to the hypothesis that SV2A dysfunction is associated with calcium accumulation during repeated action potential generation. The effect, in turn, leads to increased neurotransmitter release and a destabilization of neuronal circuits, facilitated by excitatory transmission and a concurrent attenuation of inhibition. It would explain why SV2A knockout mice have spontaneous seizures from birth and typically die within 3 weeks[3]. Similar studies also revealed that SV2A is the brain binding site of levetiracetam (Axon 1110), an antiepileptic drug with a unique activity profile in animal models of seizure and epilepsy[4].