Inhibitors of histone deacetylases are a new class of cancer therapeutics with possibly broad applicability.
Combinations of HDAC inhibitors with the kinase inhibitor 1 (Imatinib) in recent studies showed additive
and synergistic effects. Here we present a new concept by combining inhibition of protein kinases and
HDACs, two independent pharmacological activities, in one synthetic small molecule. In general, the HDAC
inhibition profile, the potencies, and the probable binding modes to HDAC1 and HDAC6 were similar as
for 6 (SAHA). Inhibition of Abl kinase in biochemical assays was maintained for most compounds, but in
general the kinase selectivity profile differed from that of 1 with nearly equipotent inhibition of the wildtype
and the Imatinib resistant Abl T315I mutant. A potent cellular inhibition of PDGFR and cytotoxicity
toward EOL-1 cells, a model for idiopathic hypereosinophilic syndrome (HES), are restored or enhanced
for selected analogues (12b, 14b, and 18b). Cytotoxicity was evaluated by using a broad panel of tumor
cell lines, with selected analogues displaying mean IC50 values between 3.6 and 7.1 μM.