Selective inhibitor of class II (IIa) histone deacetylase (HDAC). Exhibits tissue-selective inhibition between members of class II acetylases in vivo, particularly in skeletal muscle and the heart. Arrests myogenesis through the stabilization of myocyte enhancer factor 2D (MEF2D)-HDAC3/4 complex. Displays no inhibition of class I HDAC activity or expression.