HDAC9 and amyotrophic lateral sclerosis: For example, Na-4-phenylbutyrate, a brain-penetrant pan HDAC inhibitor, increased cell viability in PR-expressing U-2 OS cells [87], prolonged the survival and regulated the expression of anti-apoptotic genes in transgenic ALS mice [88], and has been investigated as a therapeutic in conjunction with taurursodial for ALS in a recent clinical trial (NCT03127514) [89].