Several oxime containing molecules, characterized by a SAHA-like structure,
were explored to select a potentially new biasing binding element for the zinc in
HDAC catalytic site. All compounds were evaluated for their in vitro inhibitory activity
against the 11 human HDACs isoforms. After identification of a “hit” molecule, a
programmed variation at the cap group and at the linker was carried out in order to
increase HDAC inhibition and/or paralogue selectivity. Some of the new derivatives
showed increased activity against a number ofHDACisoforms, even if their overall activity
range is still far from the inhibition values reported for SAHA. Moreover, different from
what was reported for their hydroxamic acid analogues the new R-oxime amide derivatives
do not select between class I and class II HDACs; rather they target specific isoforms in
each class. These somehow contradictory results were finally rationalized by a computational
assisted SAR, which gave us the chance to understand how the oxime derivatives interact with the catalytic site and justify the
observed activity profile.