MPT0G211 mesylate is a potent, orally active and selective HDAC6 inhibitor ( IC 50 =0.291 nM). MPT0G211 mesylate displays >1000-fold selective for HDAC6 over other HDAC isoforms. MPT0G211 mesylate can penetrate the blood-brain barrier. MPT0G211 mesylate ameliorates tau phosphorylation and cognitive deficits in an Alzheimer’s disease model. MPT0G211 mesylate has anti-metastatic and neuroprotective effects. Anticancer activities.