A novel approach to pH-Responsive targeted cancer Therapy: Inhibition of FaDu cancer cell proliferation with a pH low insertion Peptide-Conjugated DGAT1 inhibitor

Targeting enzymes involved in lipid metabolism is increasingly recognized as a promising anticancer strategy. Efficient inhibition of diacylglycerol O-transferase 1 (DGAT1) can block fatty acid (FA) storage. This, in turn, triggers an increase in free polyunsaturated FA concentration, leading to peroxidation and ferroptosis. In this study, we report the development of a pH-sensitive peptide (pHLIP)-drug conjugate designed to selectively deliver DGAT1 inhibitors to cancer cells nested within the acidic microenvironment of tumors. We utilized two previously established pHLIP sequences for coupling with drugs. The study of DGAT1 conjugates in large unilamellar vesicles (LUVs) of different compositions did not reveal enhanced pH-dependent insertion compared to POPC LUVs. However, using in vitro 3D tumor spheroids, significant antiproliferative effects were observed upon exposure to pHLIP-T863 (DGAT1 inhibitor) conjugates, surpassing the inhibitory activity of T863 alone. In conclusion, our study provides the first evidence that pHLIP-based conjugates with DGAT1 inhibitors have the potential to specifically target the acidic compartment of tumors. Moreover, it sheds light on the limitations of LUV models in capturing the pH-dependency of such conjugates.

Enhancing Tsuji-Trost deallylation in living cells with an internal-nucleophile coumarin-based probe

In recent years, bioorthogonal uncaging reactions have been developed to proceed efficiently under physiological conditions. However, limited progress has been made in the development of protecting groups combining stability under physiological settings with the ability to be quickly removed via bioorthogonal catalysis. Herein, we present a new water-soluble coumarin-derived probe bearing an internal nucleophilic group capable of promoting Tsuji-Trost deallylation under palladium catalysis. This probe can be cleaved by a bioorthogonal palladium complex at a faster rate than the traditional probe, namely N-Alloc-7-amino-4-methylcoumarin. As the deallylation process proved to be efficient in mammalian cells, we envision that this probe may find applications in chemical biology, bioengineering, and medicine.

Tryptophan depletion sensitizes the AHR pathway by increasing AHR expression and GCN2/LAT1-mediated kynurenine uptake, and potentiates induction of regulatory T lymphocytes

BACKGROUND

Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan-dioxygenase (TDO) are enzymes catabolizing the essential amino acid tryptophan into kynurenine. Expression of these enzymes is frequently observed in advanced-stage cancers and is associated with poor disease prognosis and immune suppression. Mechanistically, the respective roles of tryptophan shortage and kynurenine production in suppressing immunity remain unclear. Kynurenine was proposed as an endogenous ligand for the aryl hydrocarbon receptor (AHR), which can regulate inflammation and immunity. However, controversy remains regarding the role of AHR in IDO1/TDO-mediated immune suppression, as well as the involvement of kynurenine. In this study, we aimed to clarify the link between IDO1/TDO expression, AHR pathway activation and immune suppression.

METHODS

AHR expression and activation was analyzed by RT-qPCR and western blot analysis in cells engineered to express IDO1/TDO, or cultured in medium mimicking tryptophan catabolism by IDO1/TDO. In vitro differentiation of naïve CD4⁺ T cells into regulatory T cells (Tregs) was compared in T cells isolated from mice bearing different Ahr alleles or a knockout of Ahr, and cultured in medium with or without tryptophan and kynurenine.

RESULTS

We confirmed that IDO1/TDO expression activated AHR in HEK-293-E cells, as measured by the induction of AHR target genes. Unexpectedly, AHR was also overexpressed on IDO1/TDO expression. AHR overexpression did not depend on kynurenine but was triggered by tryptophan deprivation. Multiple human tumor cell lines overexpressed AHR on tryptophan deprivation. AHR overexpression was not dependent on general control non-derepressible 2 (GCN2), and strongly sensitized the AHR pathway. As a result, kynurenine and other tryptophan catabolites, which are weak AHR agonists in normal conditions, strongly induced AHR target genes in tryptophan-depleted conditions. Tryptophan depletion also increased kynurenine uptake by increasing SLC7A5 (LAT1) expression in a GCN2-dependent manner. Tryptophan deprivation potentiated Treg differentiation from naïve CD4⁺ T cells isolated from mice bearing an AHR allele of weak affinity similar to the human AHR.

CONCLUSIONS

Tryptophan deprivation sensitizes the AHR pathway by inducing AHR overexpression and increasing cellular kynurenine uptake. As a result, tryptophan catabolites such as kynurenine more potently activate AHR, and Treg differentiation is promoted. Our results propose a molecular explanation for the combined roles of tryptophan deprivation and kynurenine production in mediating IDO1/TDO-induced immune suppression.

Repositioning of FDA-Approved antifungal agents to interrogate Acyl-CoA synthetase long chain family member 4 (ACSL4) in ferroptosis

Ferroptosis, first coined in 2012, is an iron-dependent regulated cell death (RCD) characterized by the accumulation of lipid peroxides to toxic levels. This mechanism is currently being evaluated as a target for a variety of diseases offering new opportunities for drug design and development. Recent reports uncovered acyl-CoA synthetase long-chain 4 (ACSL4) as a critical contributor to ferroptosis execution. Therefore, ACSL4 inhibitors are emerging as attractive anti-ferroptotic agents. Herein, we developed a robust screening cascade with orthogonal biophysical and biochemical techniques to identify original human ACSL4 inhibitors. By screening an FDA-approved drug library, we were able to identify and validate new inhibitors with micromolar-range activities against ACSL4. With an IC₅₀ of 280 nM against hACSL4, antifungal agent sertaconazole is to our knowledge, the most potent ACSL4 inhibitor identified so far. In addition, sertaconazole significantly reduced lipid peroxidation and ferroptosis in human differentiated dopaminergic neurons (Lund human mesencephalic LUHMES cells), demonstrating that it is a valuable chemical tool for further investigating the role of ACSL4 in ferroptosis. This study highlights the phenethyl-imidazole scaffold as a novel and promising starting point for the development of anti-ferroptotic agents targeting ACSL4.

Targeting cancer cells in acidosis with conjugates between the carnitine palmitoyltransferase 1 inhibitor etomoxir and pH (low) Insertion Peptides

Targeting enzymes involved in tumor metabolism is a promising way to tackle cancer progression. The inhibition of carnitine palmitoyltransferase 1 (CPT1) by etomoxir (Eto) efficiently slows down the growth of various cancers. Unfortunately, the clinical use of this drug was abandoned because of hepatotoxic effects. We report the development of pH-sensitive peptide (pHLIP)-drug conjugate to deliver Eto selectively to cancer cells exposed to acidic microenvironmental conditions. A newly designed sequence for the pHLIP peptide, named pHLIPd, was compared with a previously published reference pHLIP peptide, named pHLIPr. We showed that the conjugate between pHLIPd and Eto has a better pH-dependent insertion and structuration than the pHLIPr-based conjugate inside POPC vesicles. We observed antiproliferative effects when applied on acid-adapted cancer cells, reaching a larger inhibitory activity than Eto alone. In conclusion, this study brings the first evidence that pHLIP-based conjugates with a CPT1 inhibitor has the potential to specifically target the tumor acidic compartment and exert anticancer effects while sparing healthy tissues.

Impact of PEGylation on an antibody-loaded nanoparticle-based drug delivery system for the treatment of inflammatory bowel disease

Nanoparticle-based oral drug delivery systems have the potential to target inflamed regions in the gastrointestinal tract by specifically accumulating at disrupted colonic epithelium. But, delivery of intact protein drugs at the targeted site is a major challenge due to the harsh gastrointestinal environment and the protective mucus layer. Biocompatible nanoparticles engineered to target the inflamed colonic tissue and efficiently penetrate the mucosal layer can provide a promising approach for orally delivering monoclonal antibodies to treat inflammatory bowel disease. The study aims to develop mucus-penetrating nanoparticles composed of poly(lactic-co-glycolic acid, PLGA) polymers with two different polyethylene glycol (PEG) chain lengths (2 kDa and 5kDa) to encapsulate monoclonal antibody against tumor necrosis factor-α (TNF-α). The impact of different PEG chain lengths on the efficacy of the nanosystems was evaluated in vitro, ex vivo, and in vivo. Both PLGA-PEG2k and PLGA-PEG5k nanoparticles successfully encapsulated the antibody and significantly reduced TNF-α secretion from activated macrophages and intestinal epithelial cells. However, only antibody-loaded PLGA-PEG2k nanoparticles were able to alleviate the experimental acute colitis in mice demonstrated by improved colon weight/length ratio, histological score, and reduced tissue-associated myeloperoxidase activity and expression of proinflammatory cytokine TNF-α levels compared with the control group. The results suggest that despite having no significant differences in the in vitro cell-based assays, PEG chain length has a significant impact on the in vivo performance of the mucus penetrating nanoparticles. Overall, PLGA-PEG2k nanoparticles were presented as a promising oral delivery system for targeted antibody delivery to treat inflammatory bowel disease. STATEMENT OF SIGNIFICANCE: There is an unmet therapeutic need for oral drug delivery systems for safe and effective antibody therapy of inflammatory bowel disease. Therefore, we have developed PEGylated PLGA-based nanoparticulate drug delivery systems for oral targeted delivery of anti-TNF-α antibody as a potential alternative treatment strategy. The PEG chain length did not affect encapsulation efficiency or interaction with mucin in vitro but resulted in differences in in vitro release profile and in vivo efficacy study. We demonstrated the superiority of anti-TNF-α mAb-PLGA-PEG2k over mAb-PLGA-PEG5k nanoparticles to effectively exhibit anti-inflammatory responses in an acute murine colitis model. These nanoparticle-based formulations may be adjusted to encapsulate other drugs that could be applied to a number of disorders at different mucosal surfaces.

Olaparib Is a Mitochondrial Complex I Inhibitor That Kills Temozolomide-Resistant Human Glioblastoma Cells

Glioblastoma represents the highest grade of brain tumors. Despite maximal resection surgery associated with radiotherapy and concomitant followed by adjuvant chemotherapy with temozolomide (TMZ), patients have a very poor prognosis due to the rapid recurrence and the acquisition of resistance to TMZ. Here, initially considering that TMZ is a prodrug whose activation is pH-dependent, we explored the contribution of glioblastoma cell metabolism to TMZ resistance. Using isogenic TMZ-sensitive and TMZ-resistant human glioblastoma cells, we report that the expression of O6-methylguanine DNA methyltransferase (MGMT), which is known to repair TMZ-induced DNA methylation, does not primarily account for TMZ resistance. Rather, fitter mitochondria in TMZ-resistant glioblastoma cells are a direct cause of chemoresistance that can be targeted by inhibiting oxidative phosphorylation and/or autophagy/mitophagy. Unexpectedly, we found that PARP inhibitor olaparib, but not talazoparib, is also a mitochondrial Complex I inhibitor. Hence, we propose that the anticancer activities of olaparib in glioblastoma and other cancer types combine DNA repair inhibition and impairment of cancer cell respiration.

Investigation of chalcogen bioisosteric replacement in a series of heterocyclic inhibitors of tryptophan 2,3-dioxygenase

Selenium is an underexplored element that can be used for bioisosteric replacement of lower molecular weight chalcogens such as oxygen and sulfur. More studies regarding the impact of selenium substitution in different chemical scaffolds are needed to fully grasp this element's potential. Herein, we decided to evaluate the impact of selenium incorporation in a series of tryptophan 2,3-dioxygenase (TDO2) inhibitors, a target of interest in cancer immunotherapy. First, we synthesized the different chalcogen isosteres through Suzuki-Miyaura type coupling. Next, we evaluated the isosteres' affinity and selectivity for TDO2, as well as their lipophilicity, microsomal stability and cellular toxicity on TDO2-expressing cell lines. Overall, chalcogen isosteric replacements did not disturb the on-target activity but allowed for a modulation of the compounds' lipophilicity, toxicity and stability profiles. The present work contributes to our understanding of oxygen/sulfur/selenium isostery towards increasing structural options in medicinal chemistry for the development of novel and distinctive drug candidates.

Needle-free iontophoresis-driven β-adrenergic sweat rate test

OBJECTIVES

Two CFTR-dependent β-adrenergic sweat rate tests applying intradermal drug injections were reported to better define diagnosis and efficacy of CFTR-directed therapies. The aim of this work was to develop and test a needle-free image-based test and to provide an accurate analysis of the responses.

METHODS

The modified method was conducted by applying two successive iontophoresis sessions using the Macroduct device. Efficiency of drug delivery was tested by evaporimetry. Cholinergically stimulated sweating was evoked by pilocarpine iontophoresis. β-adrenergically stimulated sweating was obtained by iontophoresis of isoproterenol and aminophylline in the presence of atropine and ascorbic acid. A nonlinear mixed-effects (NLME) approach was applied to model volumes of sweat and subject-specific effects displaying inter- and intra-subject variability.

RESULTS

Iontophoresis provided successful transdermal delivery of all drugs, including almost neutral isoproterenol and aminophylline. Pilocarpine was used at a concentration ∼130-times lower than that used in the classical Gibson and Cooke sweat test. Addition of ascorbic acid lowered the pH of the solution, made it stable, prevented isoproterenol degradation and promoted drug iontophoresis. Maximal secretory capacity and kinetic rate of β-adrenergic responses were blunted in CF. A cutoff of 5.2 minutes for ET50, the time to reach the half maximal secretion, discriminated CF from controls with a 100% sensitivity and specificity. Heterozygous showed an apparently reduced kinetic rate and a preserved secretory capacity.

CONCLUSION

We tested a safe, well-tolerated needle-free image-based sweat test potentially applicable in children. Modelling responses by NLME allowed evaluating metrics of CFTR-dependent effects reflecting secretory capacity and kinetic rate.

Rational Design of Original Fused-Cycle Selective Inhibitors of Tryptophan 2,3-Dioxygenase

Tryptophan 2,3-dioxygenase (TDO2) is a heme-containing enzyme constitutively expressed at high concentrations in the liver and responsible for l-tryptophan (l-Trp) homeostasis. Expression of TDO2 in cancer cells results in the inhibition of immune-mediated tumor rejection due to an enhancement of l-Trp catabolism via the kynurenine pathway. In the study herein, we disclose a new 6-(1H-indol-3-yl)-benzotriazole scaffold of TDO2 inhibitors developed through rational design, starting from existing inhibitors. Rigidification of the initial scaffold led to the synthesis of stable compounds displaying a nanomolar cellular potency and a better understanding of the structural modulations that can be accommodated inside the active site of hTDO2.

Phosphoglycerate dehydrogenase (PHGDH) inhibitors: a comprehensive review 2015-2020

Introduction:The phosphoglycerate dehydrogenase (PHGDH), a metabolic enzyme involved in the serine synthetic pathway (SSP), appears to play a central role in supporting cancer growth and proliferation. PHGDH is a dehydrogenase whose expression in cancers was first demonstrated in 2010. Because its silencing allows a significant reduction in tumor proliferation, it appears to be a promising target in the development of new anti-cancer agents.Areas covered: In this review, we will detail PHGDH inhibitors that were reported since 2015. These compounds will be ranked according to their chemical class and their site of action. Representative examples of each series will be presented as well as their inhibitory potency in vitro and/or in vivo. Finally, their most significant biological effects will be detailed.Expert opinion: Currently, and despite significant efforts, the search for PHGDH inhibitors has not yet led to the development of compounds that can be used therapeutically. The available inhibitors have either too weak inhibitory potency or limited selectivity. Therefore, it seems crucial, given the importance of this enzyme in the progression of cancer but also in other pathologies, to pursue the development of new chemical series.

Discovery of a novel lactate dehydrogenase tetramerization domain using epitope mapping and peptides

Despite being initially regarded as a metabolic waste product, lactate is now considered to serve as a primary fuel for the tricarboxylic acid cycle in cancer cells. At the core of lactate metabolism, lactate dehydrogenases (LDHs) catalyze the interconversion of lactate to pyruvate and as such represent promising targets in cancer therapy. However, direct inhibition of the LDH active site is challenging from physicochemical and selectivity standpoints. However, LDHs are obligate tetramers. Thus, targeting the LDH tetrameric interface has emerged as an appealing strategy. In this work, we examine a dimeric construct of truncated human LDH to search for new druggable sites. We report the identification and characterization of a new cluster of interactions in the LDH tetrameric interface. Using nanoscale differential scanning fluorimetry, chemical denaturation, and mass photometry, we identified several residues (E62, D65, L71, and F72) essential for LDH tetrameric stability. Moreover, we report a family of peptide ligands based on this cluster of interactions. We next demonstrated these ligands to destabilize tetrameric LDHs through binding to this new tetrameric interface using nanoscale differential scanning fluorimetry, NMR water–ligand observed via gradient spectroscopy, and microscale thermophoresis. Altogether, this work provides new insights on the LDH tetrameric interface as well as valuable pharmacological tools for the development of LDH tetramer disruptors.

Interrogating the Lactate Dehydrogenase Tetramerization Site Using (Stapled) Peptides

Lactate dehydrogenases (LDHs) are tetrameric enzymes of major significance in cancer metabolism as well as promising targets for cancer therapy. However, their wide and polar catalytic sites make them a challenging target for orthosteric inhibition. In this work, we conceived to target LDH tetramerization sites with the ambition of disrupting their oligomeric state. To do so, we designed a protein model of a dimeric LDH-H. We exploited this model through WaterLOGSY nuclear magnetic resonance and microscale thermophoresis for the identification and characterization of a set of α-helical peptides and stapled derivatives that specifically targeted the LDH tetramerization sites. This strategy resulted in the design of a macrocyclic peptide that competes with the LDH tetramerization domain, thus disrupting and destabilizing LDH tetramers. These peptides and macrocycles, along with the dimeric model of LDH-H, constitute promising pharmacological tools for the de novo design and identification of LDH tetramerization disruptors. Overall, our study demonstrates that disrupting LDH oligomerization state by targeting their tetramerization sites is achievable and paves the way toward LDH inhibition through this novel molecular mechanism.

Anti-alcohol abuse drug disulfiram inhibits human PHGDH via disruption of its active tetrameric form through a specific cysteine oxidation

Due to rising costs and the difficulty to identify new targets, drug repurposing appears as a viable strategy for the development of new anti-cancer treatments. Although the interest of disulfiram (DSF), an anti-alcohol drug, to treat cancer was reported for many years, it is only very recently that one anticancer mechanism-of-action was highlighted. This would involve the inhibition of the p97 segregase adaptor NPL4, which is essential for the turnover of proteins involved in multiple regulatory and stress-response intracellular pathways. However, recently DSF was also reported as one of the first phosphoglycerate dehydrogenase (PHGDH) inhibitors, a tetrameric enzyme catalyzing the initial step of the serine synthetic pathway that is highly expressed in numerous cancer types. Here, we investigated the structure-activity relationships (SAR) of PHGDH inhibition by disulfiram analogues as well as the mechanism of action of DSF on PHGDH via enzymatic and cell-based evaluation, mass spectrometric and mutagenesis experiments.

Radiosynthesis and validation of (±)-[18F]-3-fluoro-2-hydroxypropionate ([18F]-FLac) as a PET tracer of lactate to monitor MCT1-dependent lactate uptake in tumors

Cancers develop metabolic strategies to cope with their microenvironment often characterized by hypoxia, limited nutrient bioavailability and exposure to anticancer treatments. Among these strategies, the metabolic symbiosis based on the exchange of lactate between hypoxic/glycolytic cancer cells that convert glucose to lactate and oxidative cancer cells that preferentially use lactate as an oxidative fuel optimizes the bioavailability of glucose to hypoxic cancer cells. This metabolic cooperation has been described in various human cancers and can provide resistance to anti-angiogenic therapies. It depends on the expression and activity of monocarboxylate transporters (MCTs) at the cell membrane. MCT4 is the main facilitator of lactate export by glycolytic cancer cells, and MCT1 is adapted for lactate uptake by oxidative cancer cells. While MCT1 inhibitor AZD3965 is currently tested in phase I clinical trials and other inhibitors of lactate metabolism have been developed for anticancer therapy, predicting and monitoring a response to the inhibition of lactate uptake is still an unmet clinical need. Here, we report the synthesis, evaluation and in vivo validation of (±)-[18F]-3-fluoro-2-hydroxypropionate ([18F]-FLac) as a tracer of lactate for positron emission tomography. [18F]-FLac offers the possibility to monitor MCT1-dependent lactate uptake and inhibition in tumors in vivo.

31ièmes Journées Franco-Belges de Pharmacochimie: Meeting Report

The "Journées Franco-Belges de Pharmacochimie" is a recognized two-day annual meeting on Medicinal Chemistry that is renowned for the advanced science presented, conviviality, and outstanding opportunities for senior and young scientists to exchange knowledge. Abstracts of plenary lectures, oral communications, and posters presented during the meeting are collected in this report.

α-Ketothioamide Derivatives: A Promising Tool to Interrogate Phosphoglycerate Dehydrogenase (PHGDH)

Given the putative role of PHGDH in cancer, development of inhibitors is required to explore its function. In this context, we established and validated a straightforward enzymatic assay suitable for high-throughput screening and we identified inhibitors with similar chemical scaffolds. Through a convergent pharmacophore approach, we synthesized α-ketothioamides that exhibit interesting in vitro PHGDH inhibition and encouraging cellular results. These novel probes may be used to understand the emerging biology of this metabolic target.

Lactate Dehydrogenase B Controls Lysosome Activity and Autophagy in Cancer

Metabolic adaptability is essential for tumor progression and includes cooperation between cancer cells with different metabolic phenotypes. Optimal glucose supply to glycolytic cancer cells occurs when oxidative cancer cells use lactate preferentially to glucose. However, using lactate instead of glucose mimics glucose deprivation, and glucose starvation induces autophagy. We report that lactate sustains autophagy in cancer. In cancer cells preferentially to normal cells, lactate dehydrogenase B (LDHB), catalyzing the conversion of lactate and NAD(+) to pyruvate, NADH and H(+), controls lysosomal acidification, vesicle maturation, and intracellular proteolysis. LDHB activity is necessary for basal autophagy and cancer cell proliferation not only in oxidative cancer cells but also in glycolytic cancer cells.

Intestinal Sucrase as a Novel Target Contributing to the Regulation of Glycemia by Prebiotics

Inulin-type fructans (ITF) are known for their capacity to modulate gut microbiota, energy metabolism and to improve glycemia in several animal models of obesity, and in humans. The potential contribution of ITF as modulators of sugar digestion by host enzymes has not been evaluated yet. A sucrose challenge has been performed on naive mice fed a standard diet supplemented with or without native chicory inulin (Fibruline 5%) for 3 weeks. The area under the curve of glycemia as well as sucrase activity in the small intestine were lowered after inulin treatment. Pyrosequencing of the 16S rRNA gene confirmed important changes in gut microbiota (mostly in favor of Blautia genus) due to inulin extract supplementation. Interestingly, the suppressive effect of inulin extract on postprandial glycemia also occurred when inulin was directly added to the sucrose solution, suggesting that the effect on sucrose digestion did not require chronic inulin administration. In vitro tests confirmed a direct inhibition of sucrase enzyme by the inulin extract, thereby suggesting that native chicory inulin, in addition to its well-known prebiotic effect, is also able to decrease the digestibility of carbohydrates, a phenomenon that can contribute in the control of post prandial glycemia. We may not exclude that the sucrose escaping the digestion could also contribute to the changes in the gut microbiota after a chronic treatment with inulin.

3D-QSAR, design, synthesis and characterization of trisubstituted harmine derivatives with in vitro antiproliferative properties

Apolar trisubstituted derivatives of harmine show high antiproliferative activity on diverse cancer cell lines. However, these molecules present a poor solubility making these compounds poorly bioavailable. Here, new compounds were synthesized in order to improve solubility while retaining antiproliferative activity. First, polar substituents have shown a higher solubility but a loss of antiproliferative activity. Second, a Comparative Molecular Field Analysis (CoMFA) model was developed, guiding the design and synthesis of eight new compounds. Characterization has underlined the in vitro antiproliferative character of these compounds on five cancerous cell lines, combining with a high solubility at physiological pH, making these molecules druggable. Moreover, targeting glioma treatment, human intestinal absorption and blood brain penetration have been calculated, showing high absorption and penetration properties.

New selective carbonic anhydrase IX inhibitors: synthesis and pharmacological evaluation of diarylpyrazole-benzenesulfonamides

Carbonic anhydrase (CA) IX expression is increased upon hypoxia and has been proposed as a therapeutic target since it has been associated with poor prognosis, tumor progression and pH regulation. We report the synthesis and the pharmacological evaluation of a new class of human carbonic anhydrase (hCA) inhibitors, 4-(5-aryl-2-hydroxymethyl-pyrazol-1-yl)-benzenesulfonamides. A molecular modeling study was conducted in order to simulate the binding mode of this new family of enzyme inhibitors within the active site of hCA IX. Pharmacological studies revealed high hCA IX inhibitory potency in the parameters nanomolar range. This study showed that the position of sulfonamide group in meta of the 1-phenylpyrazole increase a selectivity hCA IX versus hCA II of our compounds. An in vitro antiproliferative screening has been performed on the breast cancer MDA-MB-231 cell using doxorubicin as cytotoxic agent and in presence of selected CA IX inhibitor. The results shown that the cytotoxic efficiency of doxorubicin in an hypoxic environment, expressed in IC50 value, is restored at 20% level with 1μM CA IX inhibitor.

Novel trisubstituted harmine derivatives with original in vitro anticancer activity

To overcome the intrinsic resistance of cancer cells to apoptotic stimuli, we designed and synthesized approximately 50 novel β-carbolines structurally related to harmine. Harmine is known for its anticancer properties and is a DYRK1A inhibitor. Of the synthesized compounds, the most active in terms of growth inhibition of five cancer cell lines are cytostatic and approximately 100 times more potent than harmine but demonstrated no DYRK1A inhibitory activity. These novel β-carbolines display similar growth inhibitory activity in cancer cells that are sensitive and resistant to apoptotic stimuli. Using ChemGPS-NP, we found that the more active β-carbolines are all more lipophilic and larger than the less active compounds. Lastly, on the basis of the NCI human tumor cell line anticancer drug screen and the NCI COMPARE algorithm, it appears that some of these compounds, including 5a and 5k, seem to act as protein synthesis inhibitors.

Tryptophan 2,3-dioxygenase (TDO) inhibitors. 3-(2-(pyridyl)ethenyl)indoles as potential anticancer immunomodulators

Tryptophan catabolism mediated by indoleamine 2,3-dioxygenase (IDO) is an important mechanism of peripheral immune tolerance contributing to tumoral immune resistance. IDO inhibition is thus an active area of research in drug development. Recently, our group has shown that tryptophan 2,3-dioxygenase (TDO), an unrelated hepatic enzyme also catalyzing the first step of tryptophan degradation, is also expressed in many tumors and that this expression prevents tumor rejection by locally depleting tryptophan. Herein, we report a structure-activity study on a series of 3-(2-(pyridyl)ethenyl)indoles. More than 70 novel derivatives were synthesized, and their TDO inhibitory potency was evaluated. The rationalization of the structure-activity relationships (SARs) revealed essential features to attain high TDO inhibition and notably a dense H-bond network mainly involving His(55) and Thr(254) residues. Our study led to the identification of a very promising compound (58) displaying good TDO inhibition (K(i) = 5.5 μM), high selectivity, and good oral bioavailability. Indeed, 58 was chosen for preclinical evaluation.

Indol-2-yl ethanones as novel indoleamine 2,3-dioxygenase (IDO) inhibitors

Indoleamine 2,3-dioxygenase (IDO) is a heme dioxygenase which has been shown to be involved in the pathological immune escape of diseases such as cancer. The synthesis and structure-activity relationships (SAR) of a novel series of IDO inhibitors based on the indol-2-yl ethanone scaffold is described. In vitro and in vivo biological activities have been evaluated, leading to compounds with IC(50) values in the micromolar range in both tests. Introduction of small substituents in the 5- and 6-positions of the indole ring, indole N-methylation and variations of the aromatic side chain are all well tolerated. An iron coordinating group on the linker is a prerequisite for biological activity, thus corroborating the virtual screening results.

Design, solid-phase synthesis, and biological evaluation of novel 1,5-diarylpyrrole-3-carboxamides as carbonic anhydrase IX inhibitors

Following previous studies we herein report the synthesis and the pharmacological evaluation of a new class of human carbonic anhydrase (hCA) inhibitors, 1,5-diarylpyrrole-3-carboxamides prepared by a solid-phase strategy involving a PS(HOBt) resin. A molecular modeling study was conducted in order to simulate the binding mode of this new family of enzyme inhibitors within the active site of hCA IX. This study revealed that the 3-position of the pyrrole was opened to the solvent, so we introduced an amino side-chain, protonated at physiological pH both to enhance the aqueous solubility and to decrease the cell membrane penetration. This strategy consisted of preparing membrane-impermeant inhibitors that may selectively target the tumor-associated hCA IX. Physico-chemical characterizations including aqueous solubility and lipophilic parameters are described. Pharmacological studies revealed high hCA IX inhibitory potency in the nanomolar range. Some compounds are selective for hCA IX displaying hCA I/hCA IX and hCA II/hCA IX ratios higher than 20 and 5, respectively.

Phosphoinositide-3-kinases (PI3Ks): combined comparative modeling and 3D-QSAR to rationalize the inhibition of p110alpha

The p110alpha isoform of the class IA PI3Ks was recently genetically validated as a promising target for anticancer therapy. However, up to now, only one compound (PIK75 = 1) has been reported as a very potent and selective inhibitor of this isoform. The lack of a 3D structure for this enzyme has clearly hindered the discovery of new p110alpha selective compounds. In view of this, we combined target-based (homology modeling) and ligand-based (3D-QSAR) approaches in an attempt to define an integrated interaction model for p110alpha inhibition. Twenty-five analogues of 1 were docked within the putative p110alpha binding site, and the molecular alignment generated was subsequently used to derive QSAR models based on scoring function, free energy of binding, CoMFA. and CoMSIA. The predictive power of these models was then analyzed using a challenging test set of 5 compounds. CoMSIA, and particularly CoMFA, models were found to outperform the other methods, predicting accurately the potency of 100% of the compounds in the test set, thereby validating our p110alpha homology model for use in further drug development.

Mechanism-Based Thrombin Inhibitors: Design, Synthesis, and Molecular Docking of a New Selective 2-Oxo-2H-1-benzopyran Derivative

New 2-oxo-2H-1-benzopyran derivatives were prepared to optimize 2a,b, initially developed as mechanism-based alpha-chymotrypsin (alpha-CT) inhibitors, into potent and selective thrombin (THR) inhibitors. From this study, 22, characterized by a 2-(N-ethyl-2'-oxoacetamide)-5'-chlorophenyl ester side chain, was shown to be a good THR inhibitor (ki/KI = 3455 M(-1) x s(-1)), displaying an excellent selectivity profile against other serine proteases such as factor Xa, trypsin, and alpha-CT. Docking analysis of this compound into the different protein structures revealed the molecular basis responsible for its potency and selectivity.

Synthesis, Structural Reassignment, and Biological Activity of Type B MAO Inhibitors Based on the 5H-Indeno[1,2-c]pyridazin-5-one Core

The synthesis and enzyme inhibitor properties of reversible type B monoamine oxidase inhibitors are described. These compounds belong to the 5H-indeno[1,2-c]pyridazine family and possess a hydrophobic benzyloxy or 4,4,4-trifluorobutoxy side chain which, in contrast to a previous assignment, has been unambiguously located at C(8) of the heterocyclic moiety. Investigation of the regioisomeric structures establishes that substitution of the 5H-indeno[1,2-c]pyridazin-5-one core at C(7) vs C(8) dramatically influences the MAO-inhibiting properties of these compounds.

Investigation of mechanism-based thrombin inhibitors: Implications of a highly conserved water molecule for the binding of coumarins within the S pocket

The synthesis of novel coumarins bearing on the lateral side chain in the 3-position an amine or a guanidine group is described. In vitro evaluation highlighted 14d which possesses a meta aniline side chain as a very potent THR inhibitor. Surprisingly, the introduction of a guanidine moiety always led to a decrease in THR inhibiting properties. We, thus, used docking experiments to rationalize the SAR in the series. This study showed the crucial role of a conserved water molecule in the specificity pocket of THR during docking simulation in order to explain the inactivity of guanidine derivatives.

3,6-Disubstituted Coumarins as Mechanism-Based Inhibitors of Thrombin and Factor Xa

In this work, coumarins were screened on thrombin (THR) and factor Xa (FXa), two of the most promising targets for the development of anticoagulant drugs. This allowed us to highlight compound 30, characterized by a 2,5-dichlorophenyl ester in the 3-position and a chloromethyl moiety in the 6-position, as a very potent THR inhibitor (ki/KI= 37,000 M(-1) s(-1)). Moreover, this compound exhibits good selectivity over FXa (168-fold) and trypsin (54-fold). The mechanism of inactivation was investigated in this series and significantly differs from that previously observed with alpha-chymotrypsin. Indeed, the addition of hydrazine on the THR-inhibitor complex promotes a partial induced THR reactivation. This reactivation, confirmed by LC/MS, showed the resurgence of the native THR and a new dihydrazide complex. Docking experiments were then efficiently used to explain the trends observed in the enzymatic assays as well as to corroborate the postulated inhibition mechanism. Finally, the cell permeability of our derivatives was estimated using a computational approach.

(E)-8-(3-Chlorostyryl)-1,3,7-trimethylxanthine, a caffeine derivative acting both as antagonist of adenosine A2A receptors and as inhibitor of MAO-B

In the crystal structure of (E)-8-(3-chlorostyryl)-1,3,7-trimethylxanthine (CSC) [systematic name: (E)-8-(3-chlorostyryl)-1,3,7-trimethyl-3,7-dihydro-1H-purine-2,6-dione], C16H15ClN4O2, the xanthine ring and the lateral styryl chain are coplanar. The crystal packing involves mainly parallel stacking of these planar molecules. The electrostatic potential calculated on the crystal structure conformation confirms the pharmacophore elements associated with MAO-B inhibition.

Modulators of the Coagulation Cascade: Focus and Recent Advances in Inhibitors of Tissue Factor, Factor VIIa and their Complex

Recent developments in the field of haemostasis and thrombosis highlighted the crucial role of the tissue factor/factor VIIa complex (TF/FVIIa) in the initiation of coagulation processes. Nowadays, anticoagulant therapies involving heparin or coumarin derivatives, thrombin or factor Xa inhibitors are generally associated with side effects such as bleeding and thrombocytopenia. In this context, the inhibition of TF, FVIIa and their complex by efficient antithrombotic drugs represents a new strategy to reduce this bleeding and to prevent thrombosis events. Moreover, TF/FVIIa inhibition is shown to be useful in the treatment of biological processes independent of the clotting cascade such as angiogenesis and cancer. Among the natural and genetically engineered TF/FVIIa inhibitors, injections of the recombinant protein rNAPc2 show clinical improvements, such as reduced bleeding and thromboembolism, over classical drugs used in the therapy of coronary angioplasty and hip or knee replacement surgery. The knowledge of the 3D-structure of TF/FVIIa complex and examination of co-crystal data of some drugs bound to this complex led to the design and synthesis of numerous TF/FVIIa inhibitors. Among them, the p-amidinophenylurea 18 (Ki = 0.027 microM), the pyrimidinones PHA-927 (30, IC50 = 0.016 microM) and PHA-798 (31, IC50 = 0.014 microM) and the pyridinone 37 (IC50 = 0.052 microM) are highly potent inhibitors of the TF/FVIIa complex, deprived of activity towards thrombin (IC50 > 30-100 microM) and factor Xa (IC50 > 10-100 microM), other proteases involved in the coagulation cascade. Both pyrimidinones prevent arterial thrombosis in non-human primate models of thrombosis and represent a safe approach to anti-thrombotic therapy in patients with cardiovascular risk factors.

Coumarin and isocoumarin as serine protease inhibitors

Serine proteases are attractive targets for the design of enzyme inhibitors since they are involved in the etiology of several diseases. Within the class of serine proteases, HLE is one of the most destructive enzymes in the body. It is implicated in the promotion or exacerbation of a number of diseases including pancreatitis, acute respiratory syndrome, rheumatoid arthritis, atherosclerosis, pulmonary emphysema, and cystic fibrosis. Thrombin, a trypsin-like serine protease, plays a dual role in thrombogenesis, including fibrin formation and platelet activation. As a result, thrombin constitutes one of the most widely studied targets for antithrombotic strategy. Numerous inhibitors of serine proteases have been reported during the past three decades. Among them, coumarin-type molecules displayed a high inhibitory potency towards various serine proteases. At that time, halomethyl dihydrocoumarins have been shown to behave as the first general suicide inhibitors of serine protease. These molecules inhibit several proteases such as human leucocyte elastase, porcine pancreatic elastase, thrombin, urokinase and human plasmin. Isocoumarins are very effective as mechanism-based inhibitors of serine proteases. Pharmacomodulation on the 3-alkoxy-4-chloroisocoumarins and the 3-alkoxy-7-amino-4-chloroisocoumarins led to strong inhibitors of numerous serine proteases such as HLE, human factor XIa and XIIa, thrombin, urokinase and kallikrein. Recently, a series of coumarins characterised by an alkyl, aryl ester, amide, thioester or ketone in the position 3 and an electrophilic chloromethyl moiety in the position 6 have been developed. These compounds were found to be high inhibitors of alpha-chymotrypin, HLE and human thrombin.

Three 5H-indeno[1,2-c]pyridazin-5-one derivatives, potent type-B monoamine oxidase inhibitors

The structures of three compounds, namely 7-methoxy-2-[3-(trifluoromethyl)phenyl]-9H-indeno[1,2-c]pyridazin-9-one, C19H11F3N2O2, (Id), 6-methoxy-2-[3-(trifluoromethyl)phenyl]-9H-indeno[1,2-c]pyridazin-9-one, C19H11F3N2O2, (IId), and 2-methyl-6-(4,4,4-trifluorobutoxy)-9H-indeno[1,2-c]pyridazin-9-one, C16H13F3N2O2, (IIf), which are potent reversible type-B monoamine oxidase (MAO-B) inhibitors, are presented and discussed. Compounds (Id) and (IId) crystallize in a nearly planar conformation. The crystal structures are stabilized by weak C-H...O hydrogen bonds. The packing is dominated by pi-pi stacking interactions between the heterocyclic central moieties of centrosymmetrically related molecules. In compound (IIf), the trifluoroethyl termination is almost perpendicular to the plane of the ring.