Current state on development of neuroprotective agents for cerebral ischemia

Abstract

The improvement of decreased cerebral blood flow using thrombolytic agents, anti-thrombin drugs, and antiplatelet drugs has been essential for acute ischemic stroke. Edaravone, a free radical scavenger, has been commercially available as a novel neuroprotective agent for ischemic stroke in Japan from 2001. The appearance of a neuroprotective agent implies that therapeutic strategy can be expanded through a combination with thrombolysis. In the previous development, several cases have reported that neuroprotective compounds failed in clinical trials. However, recent studies have clarified that the cerebral ischemia induced the neuronal cell death by mediating multiple mechanisms with necrosis and/or apoptosis. The cytotoxicity derived from the NO/peroxynitrite/free radical generating system, one of intracellular Ca2+ signaling, is a typical event in ischemic injury, which is protected by edaravone. Furthermore, it is suggested that suppression of excessively activated voltage-dependent Na+ and Ca2+ channels is effective as a strategy for neuroprotection, since abnormal excitatory stimuli in the neuronal network result in the cerebral infarction. The development of several compounds having different mechanisms of action for acute stroke is in progress. It is therefore prospected that the various novel neuroprotective agents will be provided for assuring the option of therapeutic strategy, since the reinforcement of medical stroke care including diagnosis contributes to the prolongation of the therapeutic time window.