A potent and selective inhibitor of HDAC6 (IC₅₀ = 0.002 nM, as compared with 271, 252, 0.42, 6851, and 90.7 nM for HDAC1, 2, 3, 8, and 10, respectively); prevents the growth of several pancreatic cancer cell lines (IC₅₀ = 0.1-1 μM).