[New Drug Discovery Targeting Iron in Bacterial Infectious Diseases].

Iron is necessary for all living organisms, and bacteria that cause infections in human hosts also need ferrous ions for their growth and proliferation. In the human body, most ferric ions (Fe3+) are tightly bound to iron-binding proteins such as hemoglobin, transferrin, lactoferrin, and ferritin. Pathogenic bacteria express highly specific iron uptake systems, including siderophores and specific receptors. Most bacteria secrete siderophores, which are low-molecular weight metal-chelating agents, to capture Fe3+ outside cell. Siderophores are mainly classified as either catecholate or hydroxamate. Vibrio vulnificus, a Gram-negative pathogenic bacterium, is responsible for serious infections in humans and requires iron for growth. A clinical isolate, V. vulnificus M2799, secretes a catecholate siderophore, vulnibactin, that captures ferric ions from the environment. In our study, we generated deletion mutants of the genes encoding proteins involved in the vulnibactin mediated iron-utilization system, such as ferric-vulnibactin receptor protein (VuuA), periplasmic ferric-vulnibactin binding protein (FatB), ferric-vulnibactin reductase (VuuB), and isochorismate synthase (ICS). ICS and VuuA are required under low-iron conditions for ferric-utilization in M2799, but the alternative proteins FatB and VuuB can function as a periplasmic binding protein and a ferric-chelate reductase, respectively. VatD, which functions as ferric-hydroxamate siderophores periplasmic binding protein, was shown to participate in the ferric-vulnibactin uptake system in the absence of FatB. Furthermore, the ferric-hydroxamate siderophore reductase IutB was observed to participate in ferric-vulnibactin reduction in the absence of VuuB. We propose that ferric-siderophore periplasmic binding proteins and ferric-chelate reductases represent potential targets for drug discovery in the context of infectious diseases.

Automatable downstream purification of the benzohydroxamic acid D-DIBOA from a biocatalytic synthesis.

Herbicides play a vital role in agriculture, contributing to increased crop productivity by minimizing weed growth, but their low degradability presents a threat to the environment and human health. Allelochemicals, such as DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4 H)-one), are secondary metabolites released by certain plants that affect the survival or growth of other organisms. Although these metabolites have an attractive potential for use as herbicides, their low natural production is a critical hurdle. Previously, the synthesis of the biologically active analog D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one) was achieved, using an engineered E. coli strain as a whole-cell biocatalyst, capable of transforming a precursor compound into D-DIBOA and exporting it into the culture medium, although it cannot be directly applied to crops. Here a chromatographic method to purify D-DIBOA from this cell culture medium without producing organic solvent wastes is described. The purification of D-DIBOA from a filtered culture medium to the pure compound could also be automated. Biological tests with the purified compound on weed models showed that it has virtually the same activity than the chemically synthesized D-DIBOA.

Ricolinostat promotes the generation of megakaryocyte progenitors from human hematopoietic stem and progenitor cells.

BACKGROUND: Ex vivo production of induced megakaryocytes (MKs) and platelets from stem cells is an alternative approach for supplying transfusible platelets. However, it is difficult to generate large numbers of MKs and platelets from hematopoietic stem cells and progenitor cells (HSPCs). METHODS: To optimize the differentiation efficiency of megakaryocytic cells from HSPCs, we first employed a platelet factor 4 (PF4)-promoter reporter and high-throughput screening strategy to screen for small molecules. We also investigated the effects and possible mechanisms of candidate small molecules on megakaryocytic differentiation of human HSPCs. RESULTS: The small molecule Ricolinostat remarkably promoted the expression of PF4-promoter reporter in the megakaryocytic cell line. Notably, Ricolinostat significantly enhanced the cell fate commitment of MK progenitors (MkPs) from cord blood HSPCs and promoted the proliferation of MkPs based on cell surface marker detection, colony-forming unit-MK assay, and quantitative real-time PCR analyses. MkPs generated from Ricolinostat-induced HSPCs differentiated into mature MKs and platelets. Mechanistically, we found that Ricolinostat enhanced MkP fate mainly by inhibiting the secretion of IL-8 and decreasing the expression of the IL-8 receptor CXCR2. CONCLUSION: The addition of Ricolinostat to the culture medium promoted MkP differentiation from HSPCs and enhanced the proliferation of MkPs mainly by suppressing the IL-8/CXCR2 pathway. Our results can help the development of manufacturing protocols for the efficient generation of MKs and platelets from stem cells in vitro.

Diversity in the Interaction of Amino Acid- and Peptide-Based Hydroxamic Acids with Some Platinum Group Metals in Solution.

Complexes that incorporate both ligand(s) and metal(s) exhibiting cytotoxic activity can especially be interesting to develop multifunctional drug molecules with desired activities. In this review, the limited number of solution results collected in our laboratory on the complexes of Pd(II) and two other platinum group metals-the half-sandwich type, [(η6-p-cym)Ru(H2O)3]2+, and [(η5-Cp*)Rh(H2O)3]2+-with hydroxamic acid derivatives of three amino acids, two imidazole analogues, and four small peptides are summarized and evaluated. Unlike the limited number of coordination sites of these metal ions (four and three for Pd(II) and the organometallic cations, respectively), the ligands discussed here offer a relatively high number of donor atoms as well as variation in their position within the ligands, resulting in a large versatility of the likely coordination modes. The review, besides presenting the solution equilibrium results, also discusses the main factors, such as (N,N) versus (O,O) chelate; size of chelate; amino-N versus imidazole-N; primary versus secondary hydroxamic function; differences between hydrolytic ability of the metal ions studied; and hydrolysis of the coordinated peptide hydroxamic acids in their Pd(II) complexes, which all determine the coordination modes present in the complexes formed in measurable concentrations in these systems. The options for the quantitative evaluation of metal binding effectivity and selectivity of the various ligands and the comparison with each other by using solution equilibrium data are also discussed.

TP0586532, a non-hydroxamate LpxC inhibitor, reduces LPS release and IL-6 production both in vitro and in vivo.

UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is an essential enzyme in the biosynthesis of Lipid A, an active component of lipopolysaccharide (LPS), from UDP-3-O-acyl-N-acetylglicosamine. LPS is a major component of the cell surface of Gram-negative bacteria. LPS is known to be one of causative factors of sepsis and has been associated with high mortality in septic shock. TP0586532 is a novel non-hydroxamate LpxC enzyme inhibitor. In this study, we examined the inhibitory effect of TP0586532 on the LPS release from Klebsiella pneumoniae both in vitro and in vivo. Our results confirmed the inhibitory effect of TP0586532 on LPS release from the pathogenic bacterial species. On the other hand, meropenem and ciprofloxacin increase the level of LPS release. Furthermore, the effects of TP0586532 on LPS release and interleukin (IL)-6 production in the lung were determined using a murine model of pneumonia caused by K. pneumoniae. As observed in the in vitro study, TP0586532 showed the marked inhibitory effect on LPS release in the lungs, whereas meropenem- and ciprofloxacin-treated mice showed higher levels of LPS release and IL-6 production in the lungs as compared to those in the lungs of vehicle-treated mice. Moreover, TP0586532 used in combination with meropenem and ciprofloxacin attenuated the LPS release and IL-6 production induced by meropenem and ciprofloxacin in the lung. These results indicate that the inhibitory effect of TP0586532 on LPS release from pathogenic bacteria might be of benefit in patients with sepsis.

N-Methylpropargylamine-Conjugated Hydroxamic Acids as Dual Inhibitors of Monoamine Oxidase A and Histone Deacetylase for Glioma Treatment.

Glioma treatment remains a challenge with a low survival rate due to the lack of effective therapeutics. Monoamine oxidase A (MAO A) plays a role in glioma development, and MAO A inhibitors reduce glioma growth. Histone deacetylase (HDAC) inhibition has emerged as a promising therapy for various malignancies including gliomas. We have synthesized and evaluated N-methylpropargylamine-conjugated hydroxamic acids as dual inhibitors of MAO A and HDAC. Compounds display potent MAO A inhibition with IC50 from 0.03 to <0.0001 µM and inhibit HDAC isoforms and cell growth in the micromolar to nanomolar IC50 range. These selective MAO A inhibitors increase histone H3 and α-tubulin acetylation and induce cell death via nonapoptotic mechanisms. Treatment with 15 reduced tumor size, reduced MAO A activity in brain and tumor tissues, and prolonged the survival. This first report on dual inhibitors of MAO A and HDAC establishes the basis of translational research for an improved treatment of glioma.

Histone deacetylase 6 inhibitors with blood-brain barrier penetration as a potential strategy for CNS-Disorders therapy.

Histone deacetylase 6 inhibitors (HDAC6is) have been applied to certain cancer diseases and more recently to central nervous system (CNS) disorders including Rett syndrome, Alzheimer's and Parkinson's diseases, and major depressive disorder. Brain penetrance is the major challenge for the development of HDAC6is as potential therapeutics for CNS disorders due in part to the polarity of hydroxamate ZBG. Hence, only a handful of brain-penetrant HDAC6is have been reported and a few display appropriate in vitro and in vivo activities in models of neurological diseases in last decades. This review summarizes the contemporary research being done on HADC6is with brain penetration both the biological pathways involved and the structural modification attempts.

Structure-based molecular insights into matrix metalloproteinase inhibitors in cancer treatments.

Protease inhibitors are of considerable interest as anticancer agents. Matrix metalloproteinases (MMPs) were the earliest type of proteases considered as anticancer targets. The developments of MMP inhibitors (MMPIs) by pharmaceutical companies can be dated from the early 1980s. Thus far, none of the over 50 MMPIs entering clinical trials have been approved. This work summarizes the reported studies on the structure of MMPs and complexes with ligands and inhibitors, based on which, the authors analyzed the clinical failures of MMPIs in a structural biological manner. Furthermore, MMPs were systematically compared with urokinase, a protease-generating plasmin, which plays similar pathological roles in cancer development; the reasons for the clinical successes of urokinase inhibitors and the clinical failures of MMPIs are discussed.

Functional Diversity of TonB-Like Proteins in the Heterocyst-Forming Cyanobacterium Anabaena sp. PCC 7120.

The TonB-dependent transport of scarcely available substrates across the outer membrane is a conserved feature in Gram-negative bacteria. The plasma membrane-embedded TonB-ExbB-ExbD accomplishes complex functions as an energy transducer by physically interacting with TonB-dependent outer membrane transporters (TBDTs). TonB mediates structural rearrangements in the substrate-loaded TBDTs that are required for substrate translocation into the periplasm. In the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, four TonB-like proteins have been identified. Out of these TonB3 accomplishes the transport of ferric schizokinen, the siderophore which is secreted by Anabaena to scavenge iron. In contrast, TonB1 (SjdR) is exceptionally short and not involved in schizokinen transport. The proposed function of SjdR in peptidoglycan structuring eliminates the protein from the list of TonB proteins in Anabaena. Compared with the well-characterized properties of SjdR and TonB3, the functions of TonB2 and TonB4 are yet unknown. Here, we examined tonB2 and tonB4 mutants for siderophore transport capacities and other specific phenotypic features. Both mutants were not or only slightly affected in schizokinen transport, whereas they showed decreased nitrogenase activity in apparently normal heterocysts. Moreover, the cellular metal concentrations and pigment contents were altered in the mutants, most pronouncedly in the tonB2 mutant. This strain showed an altered susceptibility toward antibiotics and SDS and formed cell aggregates when grown in liquid culture, a phenotype associated with an elevated lipopolysaccharide (LPS) production. Thus, the TonB-like proteins in Anabaena appear to take over distinct functions, and the mutation of TonB2 strongly influences outer membrane integrity. IMPORTANCE The genomes of many organisms encode more than one TonB protein, and their number does not necessarily correlate with that of TonB-dependent outer membrane transporters. Consequently, specific as well as redundant functions of the different TonB proteins have been identified. In addition to a role in uptake of scarcely available nutrients, including iron complexes, TonB proteins are related to virulence, flagellum assembly, pilus localization, or envelope integrity, including antibiotic resistance. The knowledge about the function of TonB proteins in cyanobacteria is limited. Here, we compare the four TonB proteins of Anabaena sp. strain PCC 7120, providing evidence that their functions are in part distinct, since mutants of these proteins exhibit specific features but also show some common impairments.

Non-Hydroxamate Zinc-Binding Groups as Warheads for Histone Deacetylases.

Histone deacetylases (HDACs) remove acetyl groups from acetylated lysine residues and have a large variety of substrates and interaction partners. Therefore, it is not surprising that HDACs are involved in many diseases. Most inhibitors of zinc-dependent HDACs (HDACis) including approved drugs contain a hydroxamate as a zinc-binding group (ZBG), which is by far the biggest contributor to affinity, while chemical variation of the residual molecule is exploited to create more or less selectivity against HDAC isozymes or other metalloproteins. Hydroxamates have a propensity for nonspecificity and have recently come under considerable suspicion because of potential mutagenicity. Therefore, there are significant concerns when applying hydroxamate-containing compounds as therapeutics in chronic diseases beyond oncology due to unwanted toxic side effects. In the last years, several alternative ZBGs have been developed, which can replace the critical hydroxamate group in HDACis, while preserving high potency. Moreover, these compounds can be developed into highly selective inhibitors. This review aims at providing an overview of the progress in the field of non-hydroxamic HDACis in the time period from 2015 to present. Formally, ZBGs are clustered according to their binding mode and structural similarity to provide qualitative assessments and predictions based on available structural information.

Sodium hyaluronate-g-2-((N-(6-aminohexyl)-4-methoxyphenyl)sulfonamido)-N-hydroxyacetamide with enhanced affinity towards MMP12 catalytic domain to be used as visco-supplement with increased degradation resistance.

The present paper describes the functionalization of sodium hyaluronate (NaHA) with a small molecule (2-((N-(6-aminohexyl)-4-methoxyphenyl)sulfonamido)-N-hydroxyacetamide) (MMPI) having proven inhibitory activity against membrane metalloproteins involved in inflammatory processes (i.e. MMP12). The obtained derivative (HA-MMPI) demonstrated an increased resistance to the in-vitro degradation by hyaluronidase, viscoelastic properties close to those of healthy human synovial fluid, cytocompatibility towards human chondrocytes and nanomolar affinity towards MMP 12. Thus, HA-MMPI can be considered a good candidate as viscosupplement in the treatment of knee osteoarticular disease.

Trichostatin A promotes esophageal squamous cell carcinoma cell migration and EMT through BRD4/ERK1/2-dependent pathway.

BACKGROUND: Histone deacetylases (HDACs) have been demonstrated to be aberrantly activated in tumorigenesis and cancer development. Thus, HDAC inhibitors (HDACIs) are considered to be promising anti-cancer therapeutics. However, recent studies have shown that HDACIs promote the migration of many cancer cells. Therefore, there is a need to elucidate the underlying mechanisms of HDACIs on cancer cell migration to establish a combination therapy that overcomes HDACI-induced cell migration. METHODS: KYSE-150 and EC9706 cells were treated differently. Effects of drugs and siRNA treatment on tumor cell migration and cell signaling pathways were investigated by transwell migration assy. Gene expression for SNAI2 was tested by RT-qPCR. Western blot analysis was employed to detect the level of E-cadherin, ß-catenin, vimentin,Slug，ERK1/2, H3, PAI-1 and BRD4. The effect of drugs on cell morphology was evaluated through phase-contrast microscopic images. RESULTS: TSA promotes epithelial-mesenchymal transition (EMT) in ESCC cells by downregulating the epithelial marker E-cadherin and upregulating mesenchymal markers ß-catenin, vimentin, Slug, and PAI-1. Knockdown of Slug by siRNA or inhibition of PAI-1 clearly suppressed TSA-induced ESCC cell migration and resulted in the reversal of TSA-triggered E-cadherin, ß-catenin, and vimentin expression. However, no crosstalk between Slug and PAI-1 was observed in TSA-treated ESCC cells. Blocking ERK1/2 activation also inhibited TSA-induced ESCC cell migration, EMT, and upregulation of Slug and PAI-1 levels in ESCC cells. Interestingly, inhibition of BRD4 suppressed TSA-induced ESCC cell migration and attenuated TSA-induced ERK1/2 activation and upregulation of Slug and PAI-1 levels. CONCLUSIONS: Our data indicate the existence of at least two separable ERK1/2-dependent signaling pathways in TSA-mediated ESCC cell migration: an ERK1/2-Slug branch and an ERK1/2-PAI-1 branch. Both branches of TSA-induced ESCC cell migration appear to favor the EMT process, while BRD4 is responsible for two separable ERK1/2-dependent signaling pathways in TSA-mediated ESCC cell migration.

Design, synthesis, and biological evaluation of hydroxamic acid-substituted 2,4-diaryl aminopyrimidines as potent EGFRT790M/L858R inhibitors for the treatment of NSCLC.

A series of 2,4-diarylaminopyrimidine derivatives bearing hydrophilic hydroxamic acids were designed and synthesized as potent EGFRT790M/L858R inhibitors. Among the derivatives synthesized, 10c (IC50 = 5.192 nM), 10j (IC50 = 10.35 nM), and 10o (IC50 = 0.3524 nM) exhibited higher potencies against EGFRT790/M/L858R compared to the known EGFR inhibitor AZD-9291 (IC50 = 20.80 nM). Moreover, 10j showed moderate activity against H1975 cells transfected with the EGFRT790M/L858R mutant, with an IC50 of 0.2113 µM over A431 (wild-type EGFR, SI = 47.3). In addition, 10j exhibited low toxicity in normal HBE cells (human bronchial epithelial cells, IC50 > 40 µΜ). Analysis of the mode of action indicated that 10j effectively induced apoptosis in H1975 cells by arresting the cells in the G2/M phase. Compound 10j also demonstrated efficacy in inhibiting tumor growth in a H1975 xenograft mouse model without losing body weight or killing the mice. Taken together, these results suggested that 10j might be a promising candidate for development as a potential treatment for NSCLC harboring the EGFRT790M/L858R mutation.

Discovery of Novel Dihydropyrimidine and hydroxamic acid hybrids as potent Helicobacter pylori Urease inhibitors.

Two novel series of Dihydropyrimidine-hydroxamic acid hybrids (4a-4l and 5a-5l) were designed, synthesized and evaluated for in vitro Helicobacter pylori urease inhibition. In vitro enzyme inhibition screening led to the discovery of three potent urease inhibitors 2-[[4-(4-hydroxy phenyl)-6-oxo-1,6-dihydropyrimidine-2-yl]-amino]-N-hydroxy acetamide (4g), 2-[[4-(4-chloro phenyl)-6-oxo-1,6-dihydropyrimidine-2-yl]-amino]-N-hydroxy acetamide (4b) and 3-[[4-(3-methoxy phenyl)-6-oxo-1,6-dihydropyrimidine-2-yl]-amino]-N-hydroxy propanamide (5l). Compound 4g showed excellent urease inhibition with IC50 value of 14 ± 1 nM, indicated by its strong interactions with both metallic Ni++ ions, Gly279, His221, Ala365, Asp362, Asn168, Arg338 and His322 residues of the active site of urease. Further, compounds 4b and 5l displayed very good activity with IC50 value of 0.082 ± 0.004 µM and 0.14 ± 0.013 µM respectively compared to standard Acetohydroxamic acid (IC50 - 27.4 ± 1.2 µM). Kinetic studies revealed that a mixed inhibition with both competitive and non-competitive aspects is involved in the urease inhibition mechanism. The in vitro urease inhibition results were supported by molecular docking studies. Collectively, this study indicates that 4g could be considered as promising lead molecule that can be further developed as a potent drug molecule for the treatment of Helicobacter pylori caused gastritis for further studies.

Discovery of STAT3 and Histone Deacetylase (HDAC) Dual-Pathway Inhibitors for the Treatment of Solid Cancer.

Nowadays, simultaneous inhibition of multiple targets through drug combination is an important anticancer strategy owing to the complex mechanism behind tumorigenesis. Recent studies have demonstrated that the inhibition of histone deacetylases (HDACs) will lead to compensated activation of a notorious cancer-related drug target, signal transducer and activator of transcription 3 (STAT3), in breast cancer through a cascade, which probably limits the anti-proliferation effect of HDAC inhibitors in solid tumors. By incorporating the pharmacophore of the HDAC inhibitor SAHA (vorinostat) into the STAT3 inhibitor pterostilbene, a series of potent pterostilbene hydroxamic acid derivatives with dual-target inhibition activity were synthesized. An excellent hydroxamate derivate, compound 14, inhibited STAT3 (KD = 33 nM) and HDAC (IC50 = 23.15 nM) with robust potency in vitro. Compound 14 also showed potent anti-proliferation ability in vivo and in vitro. Our study provides the first STAT3 and HDAC dual-target inhibitor for further exploration.

Reduced Expression of Extracellular Matrix Proteins in the Heart and Kidneys of Rats with Endotoxemia under the Effect of Actinonin.

We studied modulation of the expression of extracellular matrix proteins under conditions of meprin inhibition in rats with LPS-induced endotoxemia. Endotoxemia increased the expression of type I, III, IV collagens and fibronectin in the renal tissue and type III and IV collagens in the heart. Meprin inhibitor actinonin reduced expression of both meprins and genes of extracellular matrix proteins, but the intensity of this effect in the heart and kidney was different. Inhibition of meprins in endotoxemia can prevent pathological remodeling of the extracellular matrix in the heart and kidney.

Discovery of Novel Plasmodium falciparum HDAC1 Inhibitors with Dual-Stage Antimalarial Potency and Improved Safety Based on the Clinical Anticancer Drug Candidate Quisinostat.

Previously, we identified the clinical anticancer drug candidate quisinostat as a novel and potent antimalarial lead compound. To further enhance the antimalarial effect and improve safety, 31 novel spirocyclic hydroxamic acid derivatives were synthesized based on the structure of quisinostat, and their antimalarial activities and cytotoxicity were evaluated. Among them, compound 11 displayed broad potency in vitro against several multiresistant malarial parasites, especially two artemisinin-resistant clinical isolates. Moreover, 11 could eliminate both liver and erythrocytic parasites in vivo, kill all morphological erythrocytic parasites with specific potency against schizonts, and show acceptable metabolic stability and pharmacokinetic properties. Western blot analysis, PfHDAC gene knockdown, and enzymatic inhibition experiments collectively confirmed that PfHDAC1 was the target of 11. In summary, 11 is a structurally novel PfHDAC1 inhibitor with the potential to prevent and cure malaria, overcome multidrug resistance, and provide a prospective prototype for antimalarial drug research.

Unique Molecular Interaction with the Histone Deacetylase 6 Catalytic Tunnel: Crystallographic and Biological Characterization of a Model Chemotype.

Histone deacetylase 6 (HDAC6) is involved in multiple regulatory processes, ranging from cellular stress to intracellular transport. Inhibition of aberrant HDAC6 activity in several cancers and neurological diseases has been shown to be efficacious in both preclinical and clinical studies. While selective HDAC6 targeting has been pursued as an alternative to pan-HDAC drugs, identifying truly selective molecular templates has not been trivial. Herein, we report a structure-activity relationship study yielding TO-317, which potently binds HDAC6 catalytic domain 2 (Ki = 0.7 nM) and inhibits the enzyme function (IC50 = 2 nM). TO-317 exhibits 158-fold selectivity for HDAC6 over other HDAC isozymes by binding the catalytic Zn2+ and, uniquely, making a never seen before direct hydrogen bond with the Zn2+ coordinating residue, His614. This novel structural motif targeting the second-sphere His614 interaction, observed in a 1.84 Å resolution crystal structure with drHDAC6 from zebrafish, can provide new pharmacophores for identifying enthalpically driven, high-affinity, HDAC6-selective inhibitors.

HDAC7 Inhibition by Phenacetyl and Phenylbenzoyl Hydroxamates.

The zinc-containing histone deacetylase enzyme HDAC7 is emerging as an important regulator of immunometabolism and cancer. Here, we exploit a cavity in HDAC7, filled by Tyr303 in HDAC1, to derive new inhibitors. Phenacetyl hydroxamates and 2-phenylbenzoyl hydroxamates bind to Zn2+ and are 50-2700-fold more selective inhibitors of HDAC7 than HDAC1. Phenylbenzoyl hydroxamates are 30-70-fold more potent HDAC7 inhibitors than phenacetyl hydroxamates, which is attributed to the benzoyl aromatic group interacting with Phe679 and Phe738. Phthalimide capping groups, including a saccharin analogue, decrease rotational freedom and provide hydrogen bond acceptor carbonyl/sulfonamide oxygens that increase inhibitor potency, liver microsome stability, solubility, and cell activity. Despite being the most potent HDAC7 inhibitors to date, they are not selective among class IIa enzymes. These strategies may help to produce tools for interrogating HDAC7 biology related to its catalytic site.

Antibody drug conjugates with hydroxamic acid cargos for histone deacetylase (HDAC) inhibition.

Antitumor hydroxamates SAHA and Dacinostat have been linked to cetuximab and trastuzumab through a non-cleavable linker based on the p-mercaptobenzyl alcohol structure. These antibody drug conjugates (ADCs) were able to inhibit HDAC in several tumour cell lines. The cetuximab based ADCs block human lung adenocarcinoma cell proliferation, demonstrating that bioconjugation with antibodies is a suitable approach for targeted therapy based on hydroxamic acid-containing drugs. This work also shows that ADC-based delivery might be used to overcome the classical pharmacokinetic problems of hydroxamic acids.