Selective inhibitor of class IIa histone deacetylases (HDACs). Exhibits tissue-selective inhibition between members of class II deacetylases in vivo; inhibits HDAC4 and HDAC5 in skeletal muscle and the heart without affecting HDAC3 activity. Arrests myogenesis through the stabilization of myocyte enhancer factor 2D (MEF2D)-HDAC3/4 complex. Displays no inhibition of class I HDAC activity or expression. Purity 96%. MW (observed): 314.31