Exploration of hydrazine-based small molecules as metal chelators for KDM4 inhibition†

Hydrazines and related moieties are frequently employed in inhibitory compounds targeting iron-dependent dioxygenases such as the histone lysine demethylases (KDMs), which are promising targets in targeted epigenetic cancer therapies. Four compound libraries consisting of 81 compounds were synthesized and screened for inhibitory activity against KDM4A in an optimised AlphaScreen assay. Slight inhibition was observed for the series of 3-((2-benzoylhydrazono)methyl)benzoic acids that constituted library 1, with compounds 16, 17, 24, 28, and 38 exhibiting the most significant reductions in KDM4A activity at a screening concentration of 20 μM. Removal of the hydrazide carbonyl to generate a series of 3-((2-hydrazono)methyl)benzoic acids in library 2 proved detrimental to inhibitory activity except for compound 46. Evaluation of a series of 2-((2-benzoylhydrazono)methyl)benzoic acids and 2-((2-hydrazono)methyl)benzoic acids in library 3 revealed varied trends compared to matched library 1 and 2 counterparts, however, generally poor activity was observed for most compounds in this library. Masking of the carboxylic acid moiety with a methyl ester was explored in library 4 and resulted in overall reduced KDM4 inhibition compared to matched free acid counterparts in libraries 1, 2, and 3, however, compounds 70 and 72 exhibited markedly improved inhibitory activity with 72 being the most active analogue reported herein at <40% residual KDM4A activity at a screening concentration of 20 μM. Binding poses generated using MOE indicate effective metal chelation by either the carboxylic acid or hydrazine moiety in these compounds consistent with the observed inhibitory activity.