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Bis-(3-bromo-4-hydroxy)benzylidene cyclic compounds have been reported by us as epigenetic multiple ligands, but different substitutions at the two wings provided analogues with selective inhibition. Since the 1-benzyl-3,5-bis(( E )-3-bromobenzylidene)piperidin-4-one 3 displayed dual p300/EZH2 inhibition joined to cancer-selective cell death in a panel of tumor cells and in in vivo xenograft models, we prepared a series of bis(( E )-2-bromobenzylidene) cyclic compounds 4a - n to test in biochemical (p300, PCAF, SIRT1/2, EZH2, and CARM1) and cellular (NB4, U937, MCF-7, SH-SY5Y) assays. The majority of 4a - n exhibited potent dual p300 and CARM1 inhibition, sometimes reaching the submicromolar level, and induction of apoptosis mainly in the tested leukemia cell lines. The most effective compounds in both enzyme and cellular assays carried a 4-piperidone moiety and a methyl ( 4d ), benzyl ( 4e ), or acyl ( 4k - m ) substituent at N1 position. Elongation of the benzyl portion to 2-phenylethyl ( 4f ) and 3-phenylpropyl ( 4g ) decreased the potency of compounds at both the enzymatic and cellular levels, but the activity was promptly restored by introduction of a ketone group into the phenylalkyl substituent ( 4h - j ). Western blot analyses performed in NB4 and MCF-7 cells on selected compounds confirmed their inhibition of p300 and CARM1 through decrease of the levels of acetyl-H3 and acetyl-H4, marks for p300 inhibition, and of H3R17me2, mark for CARM1 inhibition.

After over 30 years of research, the development of HDAC inhibitors led to five FDA/Chinese FDA-approved drugs and many others under clinical or preclinical investigation to treat cancer and non-cancer diseases. Herein, based on our recent development of pyridine-based isomers as HDAC inhibitors, we report a series of novel 5-acylamino-2-pyridylacrylic- and -picolinic hydroxamates and 2′-aminoanilides 5 – 8 as anticancer agents. The hydroxamate 5d proved to be quite HDAC3/6-selective exhibiting IC 50 values of 80 and 11 nM, respectively, whereas the congener 5e behaved as inhibitor of HDAC1-3, −6, −8, and −10 (class I/IIb-selective inhibitor) at nanomolar level. Compound 5e provided a huge antiproliferative activity (nanomolar IC 50 values) against both haematological and solid cancer cell lines. In leukaemia U937 cells, the hydroxamate 5d and the 2′-aminoanilide 8f induced remarkable cell death after 48 h, with 76% and 100% pre-G1 phase arrest, respectively, showing a stronger effect with respect to SAHA and MS-275 used as reference compounds. In U937 cells, the highest dose- and time-dependent cytodifferentiation was obtained by the 2′-aminoanilide 8d (up to 35% of CD11c positive/propidium iodide negative cells at 5 μM for 48 h). The same 8d and the hydroxamates 5d and 5e were the most effective in inducing p21 protein expression in the same cell line. Mechanistically, 5d, 5e, 8d and 8f increased mRNA expression of p21, BAX and BAK, downregulated cyclin D1 and BCL-2 and modulated pro- and anti-apoptotic microRNAs towards apoptosis induction. Finally, 5e strongly arrested proliferation in nine different haematological cancer cell lines, with dual-digit nanomolar potency towards MV4-11, Kasumi-1, and NB4, being more potent than mocetinostat, used as reference drug. [Display omitted] • Novel Pyridine-Based Hydroxamates and 2′-Aminoanilides have been developed. • Compound 5d displayed HDAC3 and -6 selective nanomolar inhibition in vitro. • Compound 5d+5e strongly impaired cancer cells proliferation. • Compound 8d induced high U937 cell cytodifferentiation. • Compounds 5d, 5e, 8d+8f induced cell cycle arrest modulating cell cycle-/apoptosis-related miRNAs expression in U937 cells. [ABSTRACT FROM AUTHOR]