The Histone Deacetylase Inhibitors segmentation by Types classifies compounds based on chemical structure and mechanism. Key subtypes include Short-Chain Fatty Acids (SCFAs), Hydroxamic Acids, Benzamides, and Cyclopeptides. SCFAs, like sodium butyrate, lead the market (~40%) due to their established epigenetic modulation in cancer therapy. Hydroxamic acids (~35%), such as vorinostat, dominate due to broad-spectrum HDAC inhibition and regulatory approvals. Benzamides (~15%), including entinostat, are emerging in hormone-sensitive cancers, while cyclopeptides (~10%), like romidepsin, target specific HDAC isoforms in hematological malignancies. This structural diversity underpins competitive differentiation, with hydroxamic acids and SCFAs currently driving market share, while newer classes offer innovation pipelines for long-term growth.