Martinostat hydrochloride is a potent and selective histone deacetylase (HDAC) inhibitor with nanomolar affinity toward Class I HDACs (HDAC1, HDAC2, HDAC3) and the Class IIb isoform HDAC6, exerting its pharmacological effects by blocking enzymatic deacetylation and consequently increasing global histone and non-histone protein acetylation, thereby modulating transcriptional programs and disrupting key survival pathways in pathological cells; Martinostat demonstrates exceptional brain penetrance compared with other hydroxamate HDAC inhibitors, enabling high-quality neuroepigenetic PET imaging with [11C]-labeled tracers to characterize altered HDAC availability in neurodegenerative disorders such as Alzheimer’s disease, while oncology studies show that Martinostat suppresses proliferation, induces apoptosis, and enhances the activity of tyrosine kinase inhibitors in both imatinib-sensitive and imatinib-resistant chronic myeloid leukemia models, highlighting its therapeutic potential for overcoming drug resistance.