Structure–Activity Relationship Study of Vitamin K Derivatives Yields Highly Potent Neuroprotective Agents

Historically known for its role in blood coagulation and bone formation, vitamin K (VK) has begun to emerge as an important nutrient for brain function. While VK involvement in the brain has not been fully explored, it is well-known that oxidative stress plays a critical role in neurodegenerative diseases. It was recently reported that VK protects neurons and oligodendrocytes from oxidative injury and rescues Drosophila from mitochondrial defects associated with Parkinson’s disease. In this study, we take a chemical approach to define the optimal and minimum pharmacophore responsible for the neuroprotective effects of VK. In doing so, we have developed a series of potent VK analogues with favorable drug characteristics that provide full protection at nanomolar concentrations in a well-defined model of neuronal oxidative stress. Additionally, we have characterized key cellular responses and biomarkers consistent with the compounds’ ability to rescue cells from oxidative stress induced cell death

Development of Allosteric Hydrazide-Containing Class I Histone Deacetylase Inhibitors for Use in Acute Myeloid Leukemia

One of the biggest hurdles yet to be overcome for the continued improvement of histone deacetylase (HDAC) inhibitors is finding alternative motifs equipotent to the classic and ubiquitously used hydroxamic acid. The <i>N</i>-hydroxyl group of this motif is highly subject to sulfation/glucoronidation-based inactivation in humans; compounds containing this motif require much higher dosing in clinic to achieve therapeutic concentrations. With the goal of developing a second generation of HDAC inhibitors lacking this hydroxamate, we designed a series of potent and selective class I HDAC inhibitors using a hydrazide motif. These inhibitors are impervious to glucuronidation and demonstrate allosteric inhibition. In vitro and ex vivo characterization of our lead analogues’ efficacy, selectivity, and toxicity profiles demonstrate that they possess low nanomolar activity against models of acute myeloid leukemia (AML) and are at least 100-fold more selective for AML than solid immortalized cells such as HEK293 or human peripheral blood mononuclear cells

Class I HDAC Inhibitors Display Different Antitumor Mechanism in Leukemia and Prostatic Cancer Cells Depending on Their p53 Status

Previously, we designed and synthesized a series of <i>o</i>-aminobenzamide-based histone deacetylase (HDAC) inhibitors, among which the representative compound <b>11a</b> exhibited potent inhibitory activity against class I HDACs. In this study, we report the development of more potent hydrazide-based class I selective HDAC inhibitors using <b>11a</b> as a lead. Representative compound <b>13b</b> showed a mixed, slow, and tight binding inhibition mechanism for HDAC1, 2, and 3. The most potent compound <b>13e</b> exhibited low nanomolar IC₅₀s toward HDAC1, 2, and 3 and could down-regulate HDAC6 in acute myeloid leukemia MV4-11 cells. The EC₅₀ of <b>13e</b> against MV4-11 cells was 34.7 nM, which is 26 times lower than its parent compound <b>11a</b>. <i>In vitro</i> responses to <b>13e</b> vary significantly and interestingly based on cell type: in p53 wild-type MV4-11 cells, <b>13e</b> induced cell death via apoptosis and G1/S cell cycle arrest, which is likely mediated by a p53-dependent pathway, while in p53-null PC-3 cells, <b>13e</b> caused G2/M arrest and inhibited cell proliferation without inducing caspase-3-dependent apoptosis

Discovery of the First <i>N</i>‑Hydroxycinnamamide-Based Histone Deacetylase 1/3 Dual Inhibitors with Potent Oral Antitumor Activity

In our previous study, we designed and synthesized a novel series of <i>N</i>-hydroxycinnamamide-based HDAC inhibitors (HDACIs), among which the representative compound <b>14a</b> exhibited promising HDACs inhibition and antitumor activity. In this current study, we report the development of a more potent class of <i>N</i>-hydroxycinnamamide-based HDACIs, using <b>14a</b> as lead, among which, compound <b>11r</b> gave IC₅₀ values of 11.8, 498.1, 3.9, 2000.8, 5700.4, 308.2, and 900.4 nM for the inhibition of HDAC1, HDAC2, HDAC3, HDAC8, HDAC4, HDAC6, and HDAC11, exhibiting dual HDAC1/3 selectivity. Compounds <b>11e</b>, <b>11r</b>, <b>11w</b>, and <b>11y</b> showed excellent growth inhibition in multiple tumor cell lines. In vivo antitumor assay in U937 xenograft model identified compound <b>11r</b> as a potent, orally active HDACI. To the best of our knowledge, this work constitutes the first report of oral active <i>N</i>-hydroxycinnamamide-based HDACIs with dual HDAC1/3 selectivity

Class I HDAC Inhibitors Display Different Antitumor Mechanism in Leukemia and Prostatic Cancer Cells Depending on Their p53 Status

Previously, we designed and synthesized a series of <i>o</i>-aminobenzamide-based histone deacetylase (HDAC) inhibitors, among which the representative compound <b>11a</b> exhibited potent inhibitory activity against class I HDACs. In this study, we report the development of more potent hydrazide-based class I selective HDAC inhibitors using <b>11a</b> as a lead. Representative compound <b>13b</b> showed a mixed, slow, and tight binding inhibition mechanism for HDAC1, 2, and 3. The most potent compound <b>13e</b> exhibited low nanomolar IC₅₀s toward HDAC1, 2, and 3 and could down-regulate HDAC6 in acute myeloid leukemia MV4-11 cells. The EC₅₀ of <b>13e</b> against MV4-11 cells was 34.7 nM, which is 26 times lower than its parent compound <b>11a</b>. <i>In vitro</i> responses to <b>13e</b> vary significantly and interestingly based on cell type: in p53 wild-type MV4-11 cells, <b>13e</b> induced cell death via apoptosis and G1/S cell cycle arrest, which is likely mediated by a p53-dependent pathway, while in p53-null PC-3 cells, <b>13e</b> caused G2/M arrest and inhibited cell proliferation without inducing caspase-3-dependent apoptosis

Design, Synthesis, and Antitumor Evaluation of Novel Histone Deacetylase Inhibitors Equipped with a Phenylsulfonylfuroxan Module as a Nitric Oxide Donor

On the basis of the strategy of creating multifunctional drugs, a novel series of phenylsulfonylfuroxan-based hydroxamates with histone deacetylase (HDAC) inhibitory and nitric oxide (NO) donating activities were designed, synthesized, and evaluated. The most potent NO donor–HDAC inhibitor (HDACI) hybrid, <b>5c</b>, exhibited a much greater in vitro antiproliferative activity against the human erythroleukemia (HEL) cell line than that of the approved drug SAHA (Vorinostat), and its antiproliferative activity was diminished by the NO scavenger hemoglobin in a dose-dependent manner. Further mechanism studies revealed that <b>5c</b> strongly induced cellular apoptosis and G1 phase arrest in HEL cells. Animal experiment identified <b>5c</b> as an orally active agent with potent antitumor activity in a HEL cell xenograft model. Interestingly, although compound <b>5c</b> was remarkably HDAC6-selective at the molecular level, it exhibited pan-HDAC inhibition in a western blot assay, which is likely due to class I HDACs inhibition caused by NO release at the cellular level

Comparison of the Deacylase and Deacetylase Activity of Zinc-Dependent HDACs

The acetylation status of lysine residues on histone proteins has long been attributed to a balance struck between the catalytic activity of histone acetyl transferases and histone deacetylases (HDAC). HDACs were identified as the sole removers of acetyl post-translational modifications (PTM) of histone lysine residues. Studies into the biological role of HDACs have also elucidated their role as removers of acetyl PTMs from lysine residues of nonhistone proteins. These findings, coupled with high-resolution mass spectrometry studies that revealed the presence of acyl-group PTMs on lysine residues of nonhistone proteins, brought forth the possibility of HDACs acting as removers of both acyl- and acetyl-based PTMs. We posited that HDACs fulfill this dual role and sought to investigate their specificity. Utilizing a fluorescence-based assay and biologically relevant acyl-substrates, the selectivities of zinc-dependent HDACs toward these acyl-based PTMs were identified. These findings were further validated using cellular models and molecular biology techniques. As a proof of principal, an HDAC3 selective inhibitor was designed using HDAC3’s substrate preference. This resulting inhibitor demonstrates nanomolar activity and >30 fold selectivity toward HDAC3 compared to the other class I HDACs. This inhibitor is capable of increasing p65 acetylation, attenuating NF-κB activation, and thereby preventing downstream nitric oxide signaling. Additionally, this selective HDAC3 inhibition allows for control of HMGB-1 secretion from activated macrophages without altering the acetylation status of histones or tubulin