ONO-2506 is an enantiomeric, three carbon atom homolog of valproic acid under development by ONO Pharmaceutical for the potential treatment of stroke, as well as Alzheimer's and Parkinson's disease. The injectable formulation (Proglia) is undergoing phase II trials in the US and Japan for acute-phase cerebral infarction, and the oral formulation (Cereact) is in phase I trials in the UK for Alzheimer's disease (AD) and Parkinson's disease (PD). Japanese and European phase I trials for AD, PD and amyotropic lateral sclerosis (ALS) had commenced by March 2002 and phase II trials for ALS are underway in Europe.