Identification of novel aza-analogs of TN-16 as disrupters of microtubule dynamics through a multicomponent reaction.

Despite novel biological targets emerging at an impressive rate for anticancer therapy, antitubulin drugs remain the backbone of numerous oncological protocols and their efficacy has been demonstrated in a wide variety of adult and pediatric cancers. In the present contribution, we set to develop analogs of a potent but neglected antitubulin agent, TN-16, originally discovered via modification of tenuazonic acid (3-acetyl-5-sec-butyltetramic acid). To this extent, we developed a novel multicomponent reaction to prepare TN-16, and then we applied the same reaction for the synthesis of aza-analogs. In brief, we prepared a library of 62 novel compounds, and three of these retained nanomolar potencies. TN-16 and the active analogs are cytotoxic on cancer cell lines and, as expected from antitubulin agents, induce G2/M cell cycle arrest. These agents lead to a disruption of the microtubules and an increase in α-tubulin acetylation and affect in vitro polymerization, although they have a lesser effect in cellular tubulin polymerization assays.

Biochemical and structural analysis of a cytosolic sulfotransferase of the malaria vector Anopheles gambiae overexpressed in the reproductive tissues.

The temporary or permanent chemical modification of biomolecules is a crucial aspect in the physiology of all living species. However, while some modules are well characterised also in insects, others did not receive the same attention. This holds true for sulfo-conjugation that is catalysed by cytosolic sulfotransferases (SULT), a central component of the metabolism of endogenous low molecular weight molecules and xenobiotics. In particular, limited information is available about the functional roles of the mosquito predicted enzymes annotated as SULTs in genomic databases. The herein described research is the first example of a biochemical and structural study of a SULT of a mosquito species, in general, and of the malaria vector Anopheles gambiae in particular. We confirmed that the AGAP001425 transcript displays a peculiar expression pattern that is suggestive of a possible involvement in modulating the mosquito reproductive tissues physiology, a fact that could raise attention on the enzyme as a potential target for insect-containment strategies. The crystal structures of the enzyme in alternative ligand-bound states revealed elements distinguishing AgSULT-001425 from other characterized SULTs, including a peculiar conformational plasticity of a discrete region that shields the catalytic cleft and that could play a main role in the dynamics of the reaction and in the substrate selectivity of the enzyme. Along with further in vitro biochemical studies, our structural investigations could provide a framework for the discovery of small-molecule inhibitors to assess the effect of interfering with AgSULT-001425-mediated catalysis at the organismal level.

Synthesis and Characterization of Bis-Triazolyl-Pyridine Derivatives as Noncanonical DNA-Interacting Compounds.

Besides the well-known double-helical conformation, DNA is capable of folding into various noncanonical arrangements, such as G-quadruplexes (G4s) and i-motifs (iMs), whose occurrence in gene promoters, replication origins, and telomeres highlights the breadth of biological processes that they might regulate. Particularly, previous studies have reported that G4 and iM structures may play different roles in controlling gene transcription. Anyway, molecular tools able to simultaneously stabilize/destabilize those structures are still needed to shed light on what happens at the biological level. Herein, a multicomponent reaction and a click chemistry functionalization were combined to generate a set of 31 bis-triazolyl-pyridine derivatives which were initially screened by circular dichroism for their ability to interact with different G4 and/or iM DNAs and to affect the thermal stability of these structures. All the compounds were then clustered through multivariate data analysis, based on such capability. The most promising compounds were subjected to a further biophysical and biological characterization, leading to the identification of two molecules simultaneously able to stabilize G4s and destabilize iMs, both in vitro and in living cells.

CTLA-4 rs231775 and risk of acute renal graft rejection: an updated meta-analysis with trial sequential analysis.

Contrasting results exist on the association between CTLA-4 rs231775 and acute rejection in kidney transplant recipients. We herein conducted an updated systematic review with meta-analysis and trial sequential analysis (TSA) to clarify this relationship and to establish whether the current evidence is sufficient to draw firm conclusions. In addition, noteworthiness of significant pooled odds ratios (ORs) was estimated by false positive report probability (FPRP). A comprehensive search was performed through PubMed, Web of Knowledge, Cochrane Library and Open Grey up to October 2019. Fifteen independent cohorts, including a total of 5,401 kidney transplant recipients, were identified through the systematic review. Overall, no association was detected with the allelic (OR 1.07, 95% CI 0.88-1.30, P = 0.49), dominant (OR 0.94, 95% CI 0.73-1.22, P = 0.66) or the recessive (OR 1.18, 95% CI 0.97-1.43, P = 0.096) model of CTLA-4 rs231775. In each genetic model, the cumulative Z-curve in TSA crossed the futility boundary and entered the futility area. In addition, none of the significant genetic comparisons detected in the subsequent and sensitivity analyses or in previously reported meta-analyses were found to be noteworthy by FPRP. In conclusion, this study provides strong evidence that CTLA-4 rs231775 is not a clinically-relevant genetic risk determinant of acute rejection after renal transplantation.

Recent Advances in NAMPT Inhibitors: A Novel Immunotherapic Strategy.

Nicotinamide adenine dinucleotide (NAD) is a cofactor of many enzymatic reactions as well as being a substrate for a number of NAD-consuming enzymes (e.g., PARPS, sirtuins, etc). NAD can be synthesized de novo starting from tryptophan, nicotinamide, nicotinic acid, or nicotinamide riboside from the diet. On the other hand, the nicotinamide that is liberated by NAD-consuming enzymes can be salvaged to re-form NAD. In this former instance, nicotinamide phosphoribosyltransferase (NAMPT) is the bottleneck enzyme. In the many cells in which the salvage pathway is predominant, NAMPT, therefore, represents an important controller of intracellular NAD concentrations, and as a consequence of energy metabolism. It is, therefore, not surprising that NAMPT is over expressed by tumoral cells, which take advantage from this to sustain growth rate and tumor progression. This has led to the initiation of numerous medicinal chemistry programs to develop NAMPT inhibitors in the context of oncology. More recently, however, it has been shown that NAMPT inhibitors do not solely target the tumor but also have an effect on the immune system. To add complexity, this enzyme can also be secreted by cells, and in the extracellular space it acts as a cytokine mainly through the activation of Toll like Receptor 4 (TLR4), although it has not been clarified yet if this is the only receptor responsible for its actions. While specific small molecules have been developed only against the intracellular form of NAMPT, growing evidences sustain the possibility to target the extracellular form. In this contribution, the most recent evidences on the medicinal chemistry of NAMPT will be reviewed, together with the key elements that sustain the hypothesis of NAMPT targeting and the drawbacks so far encountered.

Gene polymorphisms and risk of acute renal graft rejection: A field synopsis of meta-analyses and genome-wide association studies.

In the present study we systematically re-analyzed results from meta-analyses and genome-wide association studies (GWASs) to assess the credibility of genetic associations with acute rejection risk in renal transplantation. A comprehensive literature search was performed on PubMed, Web of Knowledge, Cochrane library, and Open Grey up to July 2019. Methodological quality of systematic meta-analyses was assessed by the AMSTAR tool. Credibility of genetic associations was assessed by employing the Venice criteria and two Bayesian statistical approaches, the false positive report probability (FPRP) and the Bayesian false discovery probability (BFDP). Sixteen systematic meta-analyses, with a moderate-high quality score (median AMSTAR score: 9, range: 6-11) and 1 GWAS fulfilled the inclusion criteria. Overall, our systematic re-analysis has identified 9 polymorphic variants in 8 genes (ACE, CD28, CTLA-4, CYP3A5, IFNG, TNF-α, PTPRO and CCDC67) as potential risk factors for acute renal graft rejection. At the pre-specified prior probability of 0.001, the 2 SNPs identified by the GWAS (rs7976329 and rs10765602) showed no evidence of noteworthiness under FPRP or BFDP, indicating the possibility of false-positive associations. After applying the Venice criteria in combination with FPRP and BFDP to results from systematic meta-analyses, TT/AT vs AA of IFNG +874 T/A reached moderate epidemiological credibility, while weak evidence of association was found for all the other genetic comparisons. Well-designed GWASs and large replication studies with updated meta-analyses are still needed to identify reliable genetic predictors of acute renal graft rejection.

Data on metabolic stability, aqueous solubility and CYP inhibition of novel triazole-based nicotinamide phosphoribosyltransferase (NAMPT) inhibitors.

In the related research article, entitled "Identification of novel triazole-based nicotinamide phosphoribosyltransferase (NAMPT) inhibitors endowed with antiproliferative and antiinflammatory activity" [1], we reported the in vitro hepatic metabolism data for compounds 30c, 48b, and 31b (here named as E5, A6, and T1), in comparison with the reference compounds GPP78 and FK866 [1-3]. In this article, we retrieved the available data about the hepatic microsomal stability and metabolites structural characterization of the entire library of triazole-based NAMPT inhibitors, also implementing the given information with data regarding aqueous solubility and CYP inhibition. Compounds are divided in subclasses based on the hydrolytic resistant groups replacing the amide function of GPP78 [1, 2].

Metabolic Fate of the Isocyanide Moiety: Are Isocyanides Pharmacophore Groups Neglected by Medicinal Chemists?

Despite the isolation of hundreds of bioactive isocyanides from terrestrial fungi and bacteria as well as marine organisms, the isocyanide functionality has so far received little attention from a medicinal chemistry standpoint. The widespread tenet that isocyanides are chemically and metabolically unstable has restricted bioactivity studies to their antifouling properties and technical applications. In order to confirm or refute this idea, the hepatic metabolism of six model isocyanides was investigated. Aromatic and primary isocyanides turned out to be unstable and metabolically labile, but secondary and tertiary isocyanides resisted metabolization, showing, in some cases, cytochrome P450 inhibitory properties. The potential therefore exists for the secondary and tertiary isocyanides to qualify them as pharmacophore groups, in particular as war-heads for metalloenzyme inhibition because of their potent metal-coordinating properties.

A nicotinamide phosphoribosyltransferase-GAPDH interaction sustains the stress-induced NMN/NAD+ salvage pathway in the nucleus.

All cells require sustained intracellular energy flux, which is driven by redox chemistry at the subcellular level. NAD+, its phosphorylated variant NAD(P)+, and its reduced forms NAD(P)/NAD(P)H are all redox cofactors with key roles in energy metabolism and are substrates for several NAD-consuming enzymes (e.g. poly(ADP-ribose) polymerases, sirtuins, and others). The nicotinamide salvage pathway, constituted by nicotinamide mononucleotide adenylyltransferase (NMNAT) and nicotinamide phosphoribosyltransferase (NAMPT), mainly replenishes NAD+ in eukaryotes. However, unlike NMNAT1, NAMPT is not known to be a nuclear protein, prompting the question of how the nuclear NAD+ pool is maintained and how it is replenished upon NAD+ consumption. In the present work, using human and murine cells; immunoprecipitation, pulldown, and surface plasmon resonance assays; and immunofluorescence, small-angle X-ray scattering, and MS-based analyses, we report that GAPDH and NAMPT form a stable complex that is essential for nuclear translocation of NAMPT. This translocation furnishes NMN to replenish NAD+ to compensate for the activation of NAD-consuming enzymes by stressful stimuli induced by exposure to H2O2 or S-nitrosoglutathione and DNA damage inducers. These results indicate that by forming a complex with GAPDH, NAMPT can translocate to the nucleus and thereby sustain the stress-induced NMN/NAD+ salvage pathway.

Aryl Azides as Forgotten Electrophiles in the Van Leusen Reaction: A Multicomponent Transformation Affording 4-Tosyl-1-arylimidazoles.

Considering aryl azides as electrophilic partners for the TosMIC mediated Van Leusen reaction, a novel multicomponent synthesis of 4-tosyl-1-arylimidazoles is reported. In this transformation, two molecules of TosMIC participate in the reaction mechanism in two different ways, with the second molecule undergoing a novel type of fragmentation resulting in the incorporation of a C-H into the final product.

Identification of potent triazolylpyridine nicotinamide phosphoribosyltransferase (NAMPT) inhibitors bearing a 1,2,3-triazole tail group.

The enzyme nicotinamide phosphoribosyltransferase is both a key intracellular enzyme for NAD biosynthesis (iNAMPT) and an extracellular cytokine (eNAMPT). The relationship between this latter role and the catalytic activity of the enzyme is at present unknown. With the intent of discovering inhibitors specifically able to target eNAMPT, we increased the polarity of MV78 (EC50 = 5.8 nM; IC50 = 3.1 nM), a NAMPT inhibitor previously discovered by us. The replacement of a phenyl ring with a 1,2,3-triazole bearing a protonable N,N-dialkyl methanamine group gave a series of molecules which maintained the inhibition of the enzymatic activity but were unable to cross the plasma membrane and affect cell viability in vitro. Compounds 30b and 30f can therefore be considered as the first experimental/pharmacological tools for scientists that wish to understand the role of the catalytic activity of eNAMPT. Serendipitously, we also discovered a compound (25) which, notwithstanding its high polarity, was able to cross the plasma membrane being cytotoxic, a potent NAMPT inhibitor and effective in reducing growth of triple negative mammary carcinoma in mice. In our hands, 25 lacked retinal and cardiac toxicity, although we observed a lesser toxicity of NAMPT inhibitors in general compared to other reports.

Exploiting the Nucleophilicity of the Nitrogen Atom of Imidazoles: One-Pot Three-Component Synthesis of Imidazo-Pyrazines.

A novel one-pot multicomponent reaction to synthesize substituted imidazopyrazines is described. In brief, 1H-(imidazol-5-yl)-N-substituted methanamines react with aldehydes and isocyanides in methanol at room temperature to give imidazopyrazine derivatives in excellent yields. The imidazole nitrogen atom was able to intercept the nascent nitrilium ion, channeling the reaction toward to the sole formation of imidazopyrazines, suppressing the competitive formation of other possible side products deriving from the reaction with the high-energy nitrilium ion. The number of examples and the variability of the nature of isocyanides, aldehydes, and amine components herein employed, witness the robustness of this novel methodology.

Study of Anopheles gambiae 3-hydroxykynurenine transaminase activity and inhibition by LC-MS/MS method.

In Anopheles gambiae, the most efficient vector of the malaria parasite Plasmodium falciparum, 3-hydroxykynurenine is endowed with a toxic potential. In adult mosquitoes, the excess of 3-hydroxykynurenine is removed by a specific transaminase (3-hydroxykynurenine transaminase, 3-HKT) which converts the compound into the more stable xanthurenic acid. Interfering with 3-hydroxykynurenine metabolism in A. gambiae is a potential approach for the development of transmission-blocking drugs and insecticides. Hence, the aims of this work were to develop and validate a new LC-MS/MS method for the evaluation of A. gambiae 3-hydroxykynurenine transaminase (Ag-HKT) activity and the determination of the potency of inhibitors of the enzyme. We set up a LC-MS/MS based enzymatic assay for the determination of kinetic constants values of the recombinant Ag-HKT enzyme and for the evaluation of Ag-HKT inhibition by a known protein inhibitor used as reference and a newly synthesized compound. The chromatographic separation was performed in a gradient mode on a Phenomenex Synergi Polar-RP (150 mm × 2.0, 4 µm) with methanol and water containing both 0.2% formic acid. Mass spectrometric detection was achieved with an ion trap equipped with an ESI source, in positive ionization scan, operating in SRM mode. The LC-MS/MS method was validated in terms of selectivity, linearity, precision and accuracy.

Drug Discovery for Soft Drugs on TRPV1 and TRPM8 Channels Using the Passerini Reaction.

Multicomponent transformations, such as Ugi and Passerini reactions, allow for the fast synthesis of libraries of medium complexity, avoiding the formation of waste residues and significantly reducing time and money expenditure. Although the Ugi reaction has found a vast number of uses in medicinal chemistry, the employment of the Passerini reaction has received scant attention due to the formation of an α-acyloxyamide, which hardly resists the hydrolytic enzymes in the body. On the other hand, an overlooked possibility with the Passerini products is to exploit the presence of an ester group in the design and synthesis of soft drugs. We started to fill this gap, designing and synthesizing a series of TRPV1 and TRPM8 agonists able to act as soft drugs by using the Passerini reaction.

Nicotinamide Phosphoribosyltransferase Acts as a Metabolic Gate for Mobilization of Myeloid-Derived Suppressor Cells.

Cancer induces alteration of hematopoiesis to fuel disease progression. We report that in tumor-bearing mice the macrophage colony-stimulating factor elevates the myeloid cell levels of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway, which acts as negative regulator of the CXCR4 retention axis of hematopoietic cells in the bone marrow. NAMPT inhibits CXCR4 through a NAD/Sirtuin 1-mediated inactivation of HIF1α-driven CXCR4 gene transcription, leading to mobilization of immature myeloid-derived suppressor cells (MDSC) and enhancing their production of suppressive nitric oxide. Pharmacologic inhibition or myeloid-specific ablation of NAMPT prevented MDSC mobilization, reactivated specific antitumor immunity, and enhanced the antitumor activity of immune checkpoint inhibitors. Our findings identify NAMPT as a metabolic gate of MDSC precursor function, providing new opportunities to reverse tumor immunosuppression and to restore clinical efficacy of immunotherapy in patients with cancer. SIGNIFICANCE: These findings identify NAMPT as a metabolic gate of MDSC precursor function, providing new opportunities to reverse tumor immunosuppression and to restore clinical efficacy of immunotherapy in cancer patients.

Pyrtriazoles, a Novel Class of Store-Operated Calcium Entry Modulators: Discovery, Biological Profiling, and in Vivo Proof-of-Concept Efficacy in Acute Pancreatitis.

In recent years, channels that mediate store-operated calcium entry (SOCE, i.e., the ability of cells to sense a decrease in endoplasmic reticulum luminal calcium and induce calcium entry across the plasma membrane) have been associated with a number of disorders, spanning from immune disorders to acute pancreatitis and have been suggested to be druggable targets. In the present contribution, we exploited the click chemistry approach to synthesize a class of SOCE modulators where the arylamide substructure that characterizes most inhibitors so far described is substituted by a 1,4-disubstituted 1,2,3-triazole ring. Within this series, inhibitors of SOCE were identified and the best compound proved effective in an animal model of acute pancreatitis, a disease characterized by a hyperactivation of SOCE. Strikingly, two enhancers of the process were discovered, affording invaluable research tools to further explore the (patho)physiological role of capacitative calcium entry.

Identification of Novel Triazole-Based Nicotinamide Phosphoribosyltransferase (NAMPT) Inhibitors Endowed with Antiproliferative and Antiinflammatory Activity.

Nicotinamide phosphoribosyltransferase (NAMPT) is a key enzyme involved in the recycling of nicotinamide to maintain adequate NAD levels inside the cells. It has been postulated to be a pharmacological target, as it is overexpressed in cancer cells as well as in inflammatory diseases. We describe the synthesis and characterization of a novel class of one-digit nanomolar NAMPT inhibitors based on in vitro characterization. The most active compound tested, 30c, displayed activity in xenograft and allograft models, strengthening the potential of NAMPT inhibitors as antitumoral drugs. Furthermore, in the present contribution we describe the ability of 30c to significantly improve the outcome of colitis in mice. Given that this is the first report of an effect of NAMPT inhibitors in colitis, this result paves the way for novel applications for this class of compounds.

A Successful Replacement of Phenols with Isocyanides in the Bargellini Reaction: Synthesis of 3-Carboxamido-Isobutyric Acids.

Old multicomponent reactions are still a source of inspiration for discovering novel combinations of three or more reactants. A simple idea is to replace one of the educts of a known multicomponent reaction with another functional group and still be able to mimic the same reactivity. Following this line of thought, we report a three-component reaction in which isocyanides are able to open the epoxide intermediate of the Bargellini reaction affording 3-carboxamido-isobutyric acids in yields of 47-95%.

The Guareschi Pyridine Scaffold as a Valuable Platform for the Identification of Selective PI3K Inhibitors.

A novel series of 4-aryl-3-cyano-2-(3-hydroxyphenyl)-6-morpholino-pyridines have been designed as potential phosphatidylinositol-3-kinase (PI3K) inhibitors. The compounds have been synthesized using the Guareschi reaction to prepare the key 4-aryl-3-cyano-2,6-dihydroxypyridine intermediate. A different selectivity according to the nature of the aryl group has been observed. Compound 9b is a selective inhibitor against the PI3Kα isoform, maintaining a good inhibitory activity. Docking studies were also performed in order to rationalize its profile of selectivity.

Design, synthesis, and biological evaluation of combretabenzodiazepines: a novel class of anti-tubulin agents.

In the present manuscript, starting from the 1,4-benzodiazepin-2-one nucleus, a privileged structure in medicinal chemistry, we have synthesized a novel class of cis-locked combretastatins named combreatabenzodiazepines. They show similar cytotoxic and antitubulin activity compared to combretastatin A-4 in neuroblastoma cells, showing a better pharmacokinetic profile. This class of compounds has therefore the potential for further development as antitubulin agents.