Metabolism-Based Drug Discovery: Novel Benzothiazepine-Containing HDAC6 Inhibitor as a Potential Neuroprotective Agent

Inhibition of histone deacetylase 6 (HDAC6) has become a promising therapeutic strategy for central nervous system diseases. To address the metabolic instability of our previously discovered brain-penetrant HDAC6 inhibitor <b>5</b>, herein the identification of metabolic sites and structural optimization based on <b>5</b> were carried out. The most potent compound, <b>8k</b>, potently and selectively inhibited HDAC6 (IC₅₀ = 4.0 nM; >176-fold selectivity) and exhibited a 2-fold longer half-life in rat liver microsomes (<i>T</i> _1/2 = 29.49 min) than <b>5</b>. It stabilized the HDAC6 complex in silico and increased the level of acetylated α-tubulin in SH-SY5Y cells. <i>In vivo</i>, <b>8k</b> significantly reduced cerebral infarction (from 32.87% to 13.13%) in the rat MCAO model. These results demonstrate that <b>8k</b> is a metabolically stable, highly selective HDAC6 inhibitor with compelling neuroprotective efficacy, warranting its further development for ischemic stroke.