– T-518 (T518) is a potent, highly selective, brain penetrant, oral HDAC6 inhibitor with IC50 of 36 nM.T-518 did not obviously inhibit human HDAC1, 4, or 7 at 10 uM, which belongs to Class I or Class IIa HDAC.T-518 showed brain penetration in an oral dose and blocked HDAC6-dependent tubulin deacetylation at Lys40 in mouse hippocampus.T-518 decreased RIPA-insoluble tau accumulation (3-month treatment, 1 and 3 mg/kg), restored impaired axonal transport and novel object recognition in the P301S tau Tg mouse (tauopathy model) by 2-week treatment with dose 1 and 3 mg/kg.