Small molecules bearing hydroxamic acid as the zinc binding group (ZBG) have
been the most effective histone deacetylase inhibitors (HDACi) to date. However, concerns
about the pharmacokinetic liabilities of the hydroxamic acid moiety have stimulated research
efforts aimed at finding alternative nonhydroxamate ZBGs. We have identified 3-hydroxypyridin-
2-thione (3-HPT) as a novel ZBG that is compatible with HDAC inhibition. 3-HPT inhibits
HDAC 6 and HDAC 8 with an IC50 of 681 and 3675 nM, respectively. Remarkably, 3-HPT gives
no inhibition of HDAC 1. Subsequent optimization led to several novel 3HPT-based HDACi that
are selective for HDAC 6 and HDAC 8. Furthermore, a subset of these inhibitors induces
apoptosis in various cancer cell lines.