Anti-HDAC6 (N-terminal) polyclonal antibody

Disease-modifying therapies are needed for Fragile X Syndrome (FXS), as at present there are no effective treatments or cures. Herein, we report on a tetrahydroquinoline-based selective histone deacetylase 6 (HDAC6) inhibitor SW-100, its pharmacological and ADMET properties, and its ability to improve upon memory performance in a mouse model of FXS, Fmr1-1- mice. This small molecule demonstrates good brain penetrance, low-nanomolar potency for the inhibition of HDAC6 (IC50 = 2.3 nM), with at least a thousand-fold selectivity over all other class I, II, and IV HDAC isoforms. Moreover, through its inhibition of the alpha-tubulin deacetylase domain of HDAC6 (CD2), in cells SW-100 upregulates alpha-tubulin acetylation with no effect on histone acetylation and selectively restores the impaired acetylated alpha-tubulin levels in the hippocampus of Fmr1(-/-) mice. Lastly, SW-100 ameliorates several memory and learning impairments in Fmr1(-/-) mice, thus modeling the intellectual deficiencies associated with FXS, and hence providing a strong rationale for pursuing HDAC6-based therapies for the treatment of this rare disease.

Isoxazole is a five-membered heterocycle that is widely used in drug discovery endeavors. Here, we report the design, synthesis, and structural and biological characterization of SS-208, a novel HDAC6-selective inhibitor containing the isoxazole-3-hydroxamate moiety as a zinc-binding group as well as a hydrophobic linker. A crystal structure of the Danio rerio HDAC6/SS-208 complex reveals a bidentate coordination of the active-site zinc ion that differs from the preferred monodentate coordination observed for HDAC6 complexes with phenylhydroxamate-based inhibitors. While SS-208 has minimal effects on the viability of murine SM1 melanoma cells in vitro, it significantly reduced in vivo tumor growth in a murine SM1 syngeneic melanoma mouse model. These findings suggest that the antitumor activity of SS-208 is mainly mediated by immune-related antitumor activity as evidenced by the increased infiltration of CD8+ and NK+ T cells and the enhanced ratio of M1 and M2 macrophages in the tumor microenvironment.