Histone deacetylase 6
Histone deacetylase 6
Overview
Histone deacetylase 6 (HDAC6) is a cytoplasmic histone deacetylase and a member of the class IIb HDAC family. Unlike many other HDACs that primarily regulate chromatin in the nucleus, HDAC6 is best known for deacetylating non-histone substrates in the cytoplasm, thereby influencing processes such as protein quality control, intracellular transport, stress responses, and cell signaling. Because of these functions, HDAC6 has attracted substantial interest as a therapeutic target in cancer, neurodegenerative disease, inflammatory disorders, and metabolic disease.
Biologically, HDAC6 is often discussed as a regulator of proteostasis and cellular stress pathways. In recent research, it has been linked to stress granule biology through deacetylation of G3BP1, to neuronal and pain-related signaling in brain regions such as the central amygdala and parabrachial nuclei, and to disease-relevant pathways involving β-tubulin, B-cell lymphoma 2, and Prostaglandin-endoperoxide synthase 2. Its selective inhibition is being explored as a strategy to modulate disease phenotypes while potentially avoiding some of the broader effects associated with class I HDAC inhibition.
Focus of Latest Publications
Recent publications have continued to position histone deacetylase 6 (HDAC6) as a therapeutic target across cancer, neurodegeneration, pain, and inflammatory disease. Several studies focused on the design and optimization of selective HDAC6 inhibitors, including quinolone-based, thiazole-linked, diphenyl-1,2,4-oxadiazole, spirocyclic, indole-based, uracil-based, and other hydroxamate or heterocyclic scaffolds. These efforts generally aimed to improve HDAC6 potency and selectivity over other HDAC isoforms, with multiple compounds showing low-nanomolar HDAC6 inhibition and favorable target engagement in cellular assays. Structural and computational analyses were frequently used to rationalize binding, while biochemical and cell-based assays assessed downstream effects such as increased acetylation of α-tubulin and modulation of cell survival pathways.
In oncology, HDAC6 inhibition was linked to anti-proliferative and pro-apoptotic effects in several models. Taginostat, a quinolone-based HDAC6 inhibitor, restored apoptosis in chronic lymphocytic leukemia cells by enhancing p66Shc expression and activating STAT4, including increased STAT4 phosphorylation, nuclear translocation, and transcriptional activity; these effects were also reproduced by HDAC6 silencing, and the compound reduced leukemia burden in an Eμ-TCL1 mouse model. Other HDAC6-directed compounds showed activity in leukemia, prostate cancer, urothelial carcinoma, and melanoma models, where they promoted apoptosis, cell-cycle arrest, or tumor regression. In melanoma, the selective HDAC6 inhibitor WT-161 acted as a radiosensitizer by disrupting HDAC6 interactions with DNA damage repair proteins and suppressing DNA repair gene expression, thereby increasing irradiation-induced DNA damage. In some studies, HDAC6 inhibition was also associated with changes in apoptosis-related markers such as B-cell lymphoma 2 and p21.
A substantial portion of the recent literature examined HDAC6 in neurodegenerative and pain-related conditions. In Alzheimer’s disease-related work, dual COX-2/HDAC6 inhibitors were developed, and one lead compound enhanced α-tubulin acetylation, reduced inflammatory mediators including Prostaglandin-endoperoxide synthase 2, IL-1β, IL-6, and TNF-α, promoted amyloid-β clearance, reduced Tau hyperphosphorylation, and improved cognition in a scopolamine-induced mouse model. Another HDAC6-selective inhibitor increased Brain derived neurotrophic factor expression and improved memory performance in a scopolamine-treated mouse test. In amyotrophic lateral sclerosis and frontotemporal dementia models, the next-generation HDAC6 inhibitor EKZ-438 showed high selectivity, CNS penetrance, and oral bioavailability, and improved proteostasis, intracellular transport, motor performance, and neuronal survival in preclinical and human induced pluripotent stem cell-derived neuronal systems. In pain research, HDAC6 inhibition reduced inflammatory and neuropathic hypersensitivity, and in an irritable bowel syndrome-like rat model, intra-central amygdala administration of the selective inhibitor ACY-738 alleviated visceral pain and affective behaviors while reducing synaptic and neuroimmune alterations.
Additional studies extended HDAC6 biology to inflammatory signaling and autoimmune disease. A cGAS/HDAC dual inhibitor was reported to inhibit cGAS and modulate HDAC activity, with moderate activity against HDAC6, supporting the concept that HDACs can be leveraged in cGAS-STING pathway-related disorders. Across these publications, HDAC6 emerged as a target whose inhibition can alter acetylation-dependent signaling, proteostasis, DNA damage responses, neuroinflammation, and cell death programs, making it a recurring focus for the development of more selective and potentially safer therapeutic agents.