We report the first selective chemical probes for histone deacetylase 10 (HDAC10) with unprecedented selectivity over other HDAC isozymes. HDAC10 deacetylates polyamines and has a distinct substrate specificity, making it unique among the 11 zinc-dependent HDAC hydrolases. Taking inspiration from HDAC10 polyamine substrates, we systematically inserted an amino group (“aza-scan”) into the hexyl linker moiety of the approved drug Vorinostat (SAHA). This one atom replacement (C-->N) transformed SAHA from an unselective pan-HDAC inhibitor into a specific HDAC10 inhibitor. Optimization of the aza-SAHA structure yielded DKFZ-748, which has a double-digit nanomolar IC50 against HDAC10 in cells and >500-fold selectivity over the closest relative HDAC6 as well as the Class I enzymes (HDAC1, 2, 3, 8). Potency of our aza-SAHA derivatives is rationalized with HDAC10 co-crystal structures and demonstrated by cellular and biochemical target-engagement, as well as thermal-shift, assays. Treatment of cells with DKFZ-748, followed by quantification of selected polyamines, confirmed for the first time the suspected cellular function of HDAC10 as a poly-amine deacetylase. Selective HDAC10 chemical probes provide a valuable pharmacological tool for target validation and will enable further studies on the enigmatic biology of HDAC10 and acetylated polyamines. HDAC10-selective aza-SAHA derivatives are not cytotoxic, which opens the doors to novel therapeutic applications as immunomodulators or in combination cancer therapy.
Measurement of drug-target engagement in live cells by two-photon fluorescence anisotropy imaging