Histone deacetylase inhibitor

Histone deacetylase inhibitors (HDAC inhibitors, HDACi, HDIs) are chemical compounds that inhibit histone deacetylases. Since deacetylation of histones produces transcriptionally silenced heterochromatin, HDIs can render chromatin more transcriptionally active and induce epigenomic changes.

Source: Wikipedia — Histone deacetylase inhibitor (CC BY-SA 4.0)