SW-100 is a highly potent and selective HDAC6 inhibitor. (a) Structures of compounds 6–12, and SW-100. (b) Heat map summary of HDAC activities. (c) Full HDAC potency table of 6–12, SW-100, TubA, and NexA. IC50 values are the mean of two experiments ± SD obtained from curve-fitting of a 10-point enzymatic assay starting from 30 μM with 3-fold serial dilution against all HDAC isoform; TSA was tested in singlet 10-dose IC50 mode with 3-fold serial dilution starting at a concentration of 10 μM against HDAC class I, IIb, and IV isoforms; TMP269, a selective HDAC class IIa inhibitor, was tested in singlet 10-dose IC50 mode with 3-fold serial dilution starting at a concentration of 10 μM against HDAC class IIa isoforms.