Acridone-based inhibitors of inosine 5'-monophosphate dehydrogenase: discovery and SAR leading to the identification of N-(2-(6-(4-ethylpiperazin-1-yl)pyridin-3-yl)propan-2-yl)-2- fluoro-9-oxo-9,10-dihydroacridine-3-carboxamide (BMS-566419)

Polymer-supported synthesis of N-substituted anthranilates as the building blocks for preparation of N-arylated 3-hydroxyquinolin-4(1H)-ones

Fast and simple access to N-arylated 3-hydroxyquinolin-4(1H)-ones starting from easily available 1-methyl-2-iodoterephthalate and variously substituted anilines is presented. N-Alkylated anthranilic acid derivatives represent important intermediates. They can be advantageously prepared by solid-phase synthesis, by Buchwald–Hartwig amination or reductive amination with wide substrate scope and with excellent crude purities.

Fast and simple access to N-arylated 3-hydroxyquinolin-4(1H)-ones starting from easily available 1-methyl-2-iodoterephthalate and variously substituted anilines is presented.

10-(4-Phenylpiperazine-1-carbonyl)acridin-9(10H)-ones and related compounds: Synthesis, antiproliferative activity and inhibition of tubulin polymerization

As part of our continuing search for potent inhibitors of tubulin polymerization, two novel series of 42 10-(4-phenylpiperazine-1-carbonyl)acridin-9(10H)-ones and N-benzoylated acridones were synthesized on the basis of a retrosynthetic approach. All newly synthesized compounds were tested for antiproliferative activity and interaction with tubulin. Several analogs potently inhibited tumor cell growth. Among the compounds tested, 10-(4-(3-methoxyphenyl)piperazine-1-carbonyl)acridin-9(10H)-one (17c) exhibited excellent growth inhibitory effects on 93 tumor cell lines, with an average GI₅₀ value of 5.4 nM. We were able to show that the strong cytotoxic effects are caused by disruption of tubulin polymerization, as supported by the EBI (N,N'-Ethylenebis(iodoacetamide)) assay and the fact that the most potent inhibitors of cancer cell growth turned out to be the most efficacious tubulin polymerization inhibitors. Potencies were nearly comparable or superior to those of the antimitotic reference compounds. Closely related to this, the most active analogs inhibited cell cycling at the G2/M phase at concentrations down to 30 nM and induced apoptosis in K562 leukemia cells. We believe that our work not only proves the excellent suitability of the acridone scaffold for the design of potent tubulin polymerization inhibitors but also enables synthetic access to further potentially interesting N-acylated acridones.

Anti-Tumor Potential of IMP Dehydrogenase Inhibitors: A Century-Long Story

The purine nucleotides ATP and GTP are essential precursors to DNA and RNA synthesis and fundamental for energy metabolism. Although de novo purine nucleotide biosynthesis is increased in highly proliferating cells, such as malignant tumors, it is not clear if this is merely a secondary manifestation of increased cell proliferation. Suggestive of a direct causative effect includes evidence that, in some cancer types, the rate-limiting enzyme in de novo GTP biosynthesis, inosine monophosphate dehydrogenase (IMPDH), is upregulated and that the IMPDH inhibitor, mycophenolic acid (MPA), possesses anti-tumor activity. However, historically, enthusiasm for employing IMPDH inhibitors in cancer treatment has been mitigated by their adverse effects at high treatment doses and variable response. Recent advances in our understanding of the mechanistic role of IMPDH in tumorigenesis and cancer progression, as well as the development of IMPDH inhibitors with selective actions on GTP synthesis, have prompted a reappraisal of targeting this enzyme for anti-cancer treatment. In this review, we summarize the history of IMPDH inhibitors, the development of new inhibitors as anti-cancer drugs, and future directions and strategies to overcome existing challenges.

Boron Trifluoride Etherate Promoted Microwave-Assisted Synthesis of Antimalarial Acridones

A microwave-assisted, rapid and efficient method using boron trifluoride etherate (BF₃.Et₂O) for the synthesis of acridones, via an intramolecular acylation of N-phenylanthranilic acid derivatives, has been developed. The reaction proceeds under solvent-free conditions, tolerates a wide range of functional groups, and provides rapid access to a range of acridones in good to excellent yields. Several of the synthesized acridones exhibited potent antimalarial activities against CQ sensitive and multi-drug resistant (MDR) parasites.

Discovery of a novel allosteric inhibitor scaffold for polyadenosine-diphosphate-ribose polymerase 14 (PARP14) macrodomain 2

The polyadenosine-diphosphate-ribose polymerase 14 (PARP14) has been implicated in DNA damage response pathways for homologous recombination. PARP14 contains three (ADP ribose binding) macrodomains (MD) whose exact contribution to overall PARP14 function in pathology remains unclear. A medium throughput screen led to the identification of N-(2(-9H-carbazol-1-yl)phenyl)acetamide (GeA-69, 1) as a novel allosteric PARP14 MD2 (second MD of PARP14) inhibitor. We herein report medicinal chemistry around this novel chemotype to afford a sub-micromolar PARP14 MD2 inhibitor. This chemical series provides a novel starting point for further development of PARP14 chemical probes.

Inosine-5'-monophosphate dehydrogenase (IMPDH) inhibitors: a patent and scientific literature review (2002-2016)

INTRODUCTION

Inosine-5'-monophosphate dehydrogenase (IMPDH) is an enzyme involved in the de novo biosynthesis of guanine nucleotides. To date human IMPDH inhibitors have been approved for prevention of organ transplant rejection and as anti-viral agents. More recently, the use of IMPDH inhibitors for other indications including cancer and pathogenic microorganisms has been pursued. Areas covered: IMPDH inhibitors disclosed primarily in the patent and scientific literature from 2002 to the present are discussed. Several interesting chemotypes that have not been pursued by patent protection are also highlighted. Expert opinion: Progress has been made in the development of IMPDH inhibitors, particularly compounds that are structurally distinct from mycophenolic acid and nucleoside-based inhibitors. However, clinical progression has been hampered primarily by a limited understanding of the enzyme's role in disease pathophysiology. Finally, most of the IMPDH inhibitors developed over the past fourteen years fall within a relatively narrow set of chemotypes. This provides opportunities for expanding IMPDH inhibitor chemical space to further evaluate this class of molecular targets.

Myricetin is a novel inhibitor of human inosine 5'-monophosphate dehydrogenase with anti-leukemia activity

Human inosine 5'-monophosphate dehydrogenase (hIMPDH) is a rate-limiting enzyme in the de novo biosynthetic pathway of purine nucleotides, playing crucial roles in cellular proliferation, differentiation, and transformation. Dysregulation of hIMPDH expression and activity have been found in a variety of human cancers including leukemia. In this study, we found that myricetin, a naturally occurring phytochemical existed in berries, wine and tea, was a novel inhibitor of human type 1 and type 2 IMPDH (hIMPDH1/2) with IC50 values of 6.98 ± 0.22 μM and 4.10 ± 0.14 μM, respectively. Enzyme kinetic analysis using Lineweaver-Burk plot revealed that myricetin is a mix-type inhibitor for hIMPDH1/2. Differential scanning fluorimetry and molecular docking simulation data demonstrate that myricetin is capable of binding with hIMPDH1/2. Myricetin treatment exerts potent anti-proliferative and pro-apoptotic effects on K562 human leukemia cells in a dose-dependent manner. Importantly, cytotoxicity of myricetin on K562 cells were markedly attenuated by exogenous addition of guanosine, a salvage pathway of maintaining intracellular pool of guanine nucleotides. Taking together, these results indicate that natural product myricetin exhibits potent anti-leukemia activity by interfering with purine nucleotides biosynthetic pathway through the suppression of hIMPDH1/2 catalytic activity.

Synthesis of a Fluorescent Acridone using a Grignard Addition, Oxidation, and Nucleophilic Aromatic Substitution Reaction Sequence

A three-pot synthesis oriented for an undergraduate organic chemistry laboratory was developed to construct a fluorescent acridone molecule. This laboratory experiment utilizes Grignard addition to an aldehyde, alcohol oxidation, and iterative nucleophilic aromatic substitution steps to produce the final product. Each of the intermediates and the acridone product of the synthesis are analyzed by common techniques available in most undergraduate chemistry laboratories, such as melting point, TLC, IR spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. Yields for each transformation in the synthesis are generally moderately low to good (20-90%) and nearly all of the students (>90%) who attempted the synthesis were able to produce the final acridone product.

Antiviral activity of an N-allyl acridone against dengue virus

Background

Dengue virus (DENV), a member of the family Flaviviridae, is at present the most widespread causative agent of a human viral disease transmitted by mosquitoes. Despite the increasing incidence of this pathogen, there are no antiviral drugs or vaccines currently available for treatment or prevention. In a previous screening assay, we identified a group of N-allyl acridones as effective virus inhibitors. Here, the antiviral activity and mode of action targeted to viral RNA replication of one of the most active DENV-2 inhibitors was further characterized.

Results

The compound 10-allyl-7-chloro-9(10H)-acridone, designated 3b, was active to inhibit the in vitro infection of Vero cells with the four DENV serotypes, with effective concentration 50% (EC₅₀) values in the range 12.5-27.1 μM, as determined by virus yield inhibition assays. The compound was also effective in human HeLa cells. No cytotoxicity was detected at 3b concentrations up to 1000 μM. Mechanistic studies demonstrated that virus entry into the host cell was not affected, whereas viral RNA synthesis was strongly inhibited, as quantified by real time RT-PCR. The addition of exogenous guanosine together with 3b rescued only partially the infectivity of DENV-2.

Conclusions

The acridone derivative 3b selectively inhibits the infection of Vero cells with the four DENV serotypes without a direct interaction with the host cell or the virion but interfering specifically with the intracellular virus multiplication. The mode of antiviral action for this acridone apparently involves the cellular enzyme inosine-monophospahe dehydrogenase together with another still unidentified target related to DENV RNA synthesis.

In silico design of human IMPDH inhibitors using pharmacophore mapping and molecular docking approaches

Inosine 5′-monophosphate dehydrogenase (IMPDH) is one of the crucial enzymes in the de novo biosynthesis of guanosine nucleotides. It has served as an attractive target in immunosuppressive, anticancer, antiviral, and antiparasitic therapeutic strategies. In this study, pharmacophore mapping and molecular docking approaches were employed to discover novel Homo sapiens IMPDH (hIMPDH) inhibitors. The Güner-Henry (GH) scoring method was used to evaluate the quality of generated pharmacophore hypotheses. One of the generated pharmacophore hypotheses was found to possess a GH score of 0.67. Ten potential compounds were selected from the ZINC database using a pharmacophore mapping approach and docked into the IMPDH active site. We find two hits (i.e., ZINC02090792 and ZINC00048033) that match well the optimal pharmacophore features used in this investigation, and it is found that they form interactions with key residues of IMPDH. We propose that these two hits are lead compounds for the development of novel hIMPDH inhibitors.

Synthesis and evaluation of the antitumor activity of polyhalo acridone derivatives

A series of polyhalo acridone heterocyclic compounds were synthesized and evaluated for theirin vitroantitumor activity. Compounds4d,4o,5jand5kshowed good antineoplastic selectivity.

A biomass-involved strategy for the synthesis of N-arylated dibenzo[b,e][1,4]oxazepin-11(5H)-ones, acridones, 7,12-dihydrodibenzo[b,e][1,4]oxazocin-6H-ones and dibenzo[b,f]azepin-10(11H)-ones

A chemo- and regio-selective method for the construction of benzo-fused six- to eight-membered N-heterocycles from renewable feedstock shikimic acid is described.

Synthesis and evaluation of N-alkyl-9-aminoacridines with antibacterial activity

A series of 9-alkylaminoacridines were synthesized and evaluated for activity against two strains of methicillin-resistant and one strain of methicillin-sensitive Staphylococcus aureus. Results are presented that show a clear structure activity relationship between the N-alkyl chain length and antibacterial activity with peak MIC99 values of 2-3 μM for alkyl chains ranging from 10 to 14 carbons in length. Although prior work has linked the function of acridine-based compounds to intercalation and topoisomerase inhibition, the present results show that 9-alkylaminoacridines likely function as amphiphilic membrane-active disruptors potentially in a similar manner as quaternary ammonium antimicrobials.

Host cell factors as antiviral targets in arenavirus infection

Among the members of the Arenaviridae family, Lassa virus and Junin virus generate periodic annual outbreaks of severe human hemorrhagic fever (HF) in endemic areas of West Africa and Argentina, respectively. Given the human health threat that arenaviruses represent and the lack of a specific and safe chemotherapy, the search for effective antiviral compounds is a continuous demanding effort. Since diverse host cell pathways and enzymes are used by RNA viruses to fulfill their replicative cycle, the targeting of a host process has turned an attractive antiviral approach in the last years for many unrelated virus types. This strategy has the additional benefit to reduce the serious challenge for therapy of RNA viruses to escape from drug effects through selection of resistant variants triggered by their high mutation rate. This article focuses on novel strategies to identify inhibitors for arenavirus therapy, analyzing the potential for antiviral developments of diverse host factors essential for virus infection.

Drug discovery technologies and strategies for Machupo virus and other New World arenaviruses

INTRODUCTION

Seven arenaviruses cause viral hemorrhagic fever in humans: the Old World arenaviruses Lassa and Lujo, and the New World Clade B arenaviruses Machupo (MACV), Junín (JUNV), Guanarito (GTOV), Sabiá (SABV), and Chapare (CHPV). All of these viruses are Risk Group 4 biosafety pathogens. MACV causes human disease outbreak with high case-fatality rates. To date, at least 1,200 cases with ≈200 fatalities have been recorded.

AREAS COVERED

This review summarizes available systems and technologies for the identification of antivirals against MACV. Furthermore, the article summarizes animal models that have been used for the in vivo evaluation of novel inhibitors. The article highlights present treatments for arenaviral diseases and provides an overview of efficacious small molecules and other therapeutics reported to date. Finally, the article summarizes strategies to identify novel inhibitors for anti-arenaviral therapy.

EXPERT OPINION

New high-throughput approaches to quantitate infection rates of arenaviruses, as well as viruses modified to carry reporter genes, will accelerate compound screens and drug discovery efforts. RNAi, gene expression profiling and proteomics studies will identify host targets for therapeutic intervention. New discoveries in the cell entry mechanism of MACV and other arenaviruses as well as extensive structural studies of arenaviral L and NP could facilitate the rational design of antivirals effective against all pathogenic New World arenaviruses.

Identification of novel Mt-Guab2 inhibitor series active against M. tuberculosis

Tuberculosis (TB) remains a leading cause of mortality worldwide. With the emergence of multidrug resistant TB, extensively drug resistant TB and HIV-associated TB it is imperative that new drug targets be identified. The potential of Mycobacterium tuberculosis inosine monophosphate dehydrogenase (IMPDH) as a novel drug target was explored in the present study. IMPDH exclusively catalyzes the conversion of inosine monophosphate (IMP) to xanthosine monophosphate (XMP) in the presence of the cofactor nicotinamide adenine dinucleotide (NAD⁺). Although the enzyme is a dehydrogenase, the enzyme does not catalyze the reverse reaction i.e. the conversion of XMP to IMP. Unlike other bacteria, M. tuberculosis harbors three IMPDH-like genes, designated as Mt-guaB1, Mt-guaB2 and Mt-guaB3 respectively. Of the three putative IMPDH's, we previously confirmed that Mt-GuaB2 was the only functional ortholog by characterizing the enzyme kinetically. Using an in silico approach based on designed scaffolds, a series of novel classes of inhibitors was identified. The inhibitors possess good activity against M. tuberculosis with MIC values in the range of 0.4 to 11.4 µg mL⁻¹. Among the identified ligands, two inhibitors have nanomolar K_is against the Mt-GuaB2 enzyme.

Azaindenoisoquinolines as topoisomerase I inhibitors and potential anticancer agents: a systematic study of structure-activity relationships

A comprehensive study of a series of azaindenoisoquinoline topoisomerase I (Top1) inhibitors is reported. The synthetic pathways have been developed to prepare 7-, 8-, 9-, and 10-azaindenoisoquinolines. The present study shows that 7-azaindenoisoquinolines possess the greatest Top1 inhibitory activity and cytotoxicity. Additionally, the introduction of a methoxy group into the D-ring of 7-azaindenoisoquinolines improved their biological activities, leading to new lead molecules for further development. A series of QM calculations were performed on the model "sandwich" complexes of azaindenoisoquinolines with flanking DNA base pairs from the Drug-Top1-DNA ternary complex. The results of these calculations demonstrate how changes in two forces contributing to the π-π stacking (dispersion and charge-transfer interactions) affect the binding of the drug to the Top1-DNA cleavage complex and thus modulate the drug's Top1 inhibitory activity.

Synthesis of fluorinated benzophenones, xanthones, acridones, and thioxanthones by iterative nucleophilic aromatic substitution

Fluorination of fluorophores can substantially enhance their photostability and improve spectroscopic properties. To facilitate access to fluorinated fluorophores, bis(2,4,5-trifluorophenyl)methanone was synthesized by treatment of 2,4,5-trifluorobenzaldehyde with a Grignard reagent derived from 1-bromo-2,4,5-trifluorobenzene, followed by oxidation of the resulting benzyl alcohol. This hexafluorobenzophenone was subjected to sequential nucleophilic aromatic substitution reactions, first at one or both of the more reactive 4,4'-fluorines, and second by cyclization through substitution of the less reactive 2,2'-fluorines, using a variety of oxygen, nitrogen, and sulfur nucleophiles, including hydroxide, methoxide, amines, and sulfide. This method yields symmetrical and asymmetrical fluorinated benzophenones, xanthones, acridones, and thioxanthones and provides scalable access to known and novel precursors to fluorinated analogues of fluorescein, rhodamine, and other derivatives. Spectroscopic studies revealed that several of these precursors are highly fluorescent, with tunable absorption and emission spectra, depending on the substituents. This approach should allow access to a wide variety of novel fluorinated fluorophores and related compounds.

In vitro and in vivo characterization of AS2643361, a novel and highly potent inosine 5'-monophosphate dehydrogenase inhibitor

Inosine 5'-monophosphate (IMP) dehydrogenase is a critical target in solid organ transplantation. To this end, the development of mycophenolate mofetil (MMF) represents a major advance in transplant medicine. Here, we investigated the in vitro and in vivo pharmacological effects of a novel IMP dehydrogenase inhibitor, AS2643361, in several immunological and non-immunological models. The in vitro inhibitory activity of AS2643361 on immune cell and endothelial cell proliferation and on antibody production from lipopolysaccharide-stimulated B cells, was significantly more potent than that of mycophenolic acid, the active form of MMF, despite the similar potency of these compounds on IMP dehydrogenase. In a rat heterotopic cardiac transplant model, monotherapy using orally administered AS2643361 at 10 or 20mg/kg/day prolonged the median graft survival time from 6 to 16 and 19days, respectively. In dinitrophenol-lipopolysaccharide stimulated rats, oral administration of AS2643361 at 2.5, 5 or 10mg/kg/day resulted in suppression of antibody production. In vivo antibody production against alloantigen was also suppressed by AS2643361 treatment at 5 or 10mg/kg/day. Furthermore, treatment with AS2543361 effectively inhibited balloon injury induced-intimal thickening, which is a major cause of late allograft loss. Overall, the in vivo activity of AS2643361 was over two-fold more potent than that of MMF. In addition, gastrointestinal toxicity, considered a dose-limiting factor for MMF, was reduced with AS2643361 treatment. These results suggest AS2643361 has higher potency and less toxicity than MMF, making it a potential candidate for treatment of acute and chronic rejection in transplant medicine.

Inhibition of Junin virus RNA synthesis by an antiviral acridone derivative

There are no specific approved drugs for the treatment of agents of viral hemorrhagic fevers (HF) and antiviral therapies against these viruses are urgently needed. The present study characterizes the potent and selective antiviral activity against the HF causing arenavirus Junin virus (JUNV) of the compound 10-allyl-6-chloro-4-methoxy-9(10H)-acridone, designated 3f. The effectiveness of 3f to inhibit JUNV multiplication was not importantly affected by the initial multiplicity of infection, with similar effective concentration 50% (EC(50)) values in virus yield inhibition assays performed in Vero cells in the range of 0.2-40 plaque forming units (PFU)/cell. Mechanistic studies demonstrated that 3f did not affect the initial steps of adsorption and internalization. The subsequent process of viral RNA synthesis was strongly inhibited, as quantified by real time RT-PCR in compound-treated cells relative to non-treated cells. The addition of exogenous guanosine rescued the infectivity and RNA synthesis of JUNV in 3f-treated cells in a dose-dependent manner, but the reversal was partial, suggesting that the reduction of the GTP pool contributed to the antiviral activity of 3f, but it was not the main operative mechanism. The comparison of 3f with two other viral RNA inhibitors, ribavirin and mycophenolic acid, showed that ribavirin did not act against JUNV through the cellular enzyme inosine monophosphate dehydrogenase (IMPDH) inhibition whereas the anti-JUNV activity of mycophenolic acid was mainly targeted at this enzyme.

A three-dimensional pharmacophore model for IMPDH inhibitors

Inosine 5'-monophosphate dehydrogenase (IMPDH) is a key enzyme in the de novo synthesis of guanosine nucleotides. It is considered an important target in the quest for drugs in the immunosuppressive, antiviral, antibacterial and anticancer therapeutic areas. In this study, a chemical feature-based pharmacophore model of IMPDH inhibitors has been firstly developed with the aid of the HypoRefine protocol within Discovery Studio 2.5. The best model for IMPDH inhibitors, Hypo1-1, was characterized by the best correlation coefficient (0.97595) and the lowest RMSD (0.582058). It consisted of one hydrogen-bond donor, one hydrogen-bond acceptor, one aromatic ring and one hydrophobic feature, as well as two excluded volumes. The model was validated using a wide range of test molecules and a cross-validation. Furthermore, the pharmacophore features were confirmed by molecular docking studies. The pharmacophore model could quantitatively predict inhibitor activity and identify highly potent molecules. Therefore, the present results could be valuable for the discovery and development of specific IMPDH inhibitors.

Different BOLD responses to intragastric load of L-glutamate and inosine monophosphate in conscious rats

In this study, we compared the blood oxygen level-dependent (BOLD) signal changes between intragastric load of monosodium L-glutamate (MSG) and inosine monophosphate (IMP), which elicit the umami taste. An intragastric load of 30 mM IMP or 60 mM MSG induced a BOLD signal increase in several brain regions, including the nucleus of the solitary tract (NTS), lateral hypothalamus (LH), and insular cortex. Only MSG increased the BOLD signal in the amygdala (AMG). The time course of the BOLD signal changes in the NTS and the LH in the IMP group was different from that of the MSG group. We further compared the brain regions correlated with the BOLD signal change in the NTS between MSG and IMP groups. The BOLD responses in the hippocampus and the orbital cortex were associated with activation of the NTS in both MSG and IMP groups, but the association in the AMG and the pyriform was only in MSG group. These results indicate that gut stimulation with MSG and IMP evoked BOLD responses in distinct regions with different temporal patterns and that the mechanism of perception of L-glutamate and IMP in the gastrointestinal tract differed from that in the taste-sensing system.

Structure-activity relationship studies of acridones as potential antipsoriatic agents. 2. Synthesis and antiproliferative activity of 10-substituted hydroxy-10H-acridin-9-ones against human keratinocyte growth

A series of 10-substituted hydroxy-10H-acridin-9-ones were synthesized and studied as potential antipsoriatic agents. The antiproliferative activity of the novel derivatives, which can be considered as aza-analogues of the antipsoriatic drug anthralin, was determined using the human keratinocyte cell line HaCaT. Structure-activity relationships with respect to the nature of the N-substituent at the acridone scaffold were delineated. Release of lactate dehydrogenase (LDH) was used to exclude non-specific cytotoxic effects. As compared to anthralin, N-substitution of the acridone scaffold in the target compounds provided agents devoid of radical producing properties, which was documented by their ineffectiveness to interact with the free radical 2,2-diphenyl-1-picrylhydrazyl. This was in excellent agreement with the data obtained from the LDH assay in which the novel compounds did not induce membrane damage. Benzyl substitution at the 10-position yielded keratinocyte growth inhibitory activity in the low micromolar range. The most potent inhibitor of keratinocyte hyperproliferation was compound 8a having an N-methyl group and a 1,3-dihydroxy arrangement at the acridone scaffold, with an IC(50) value comparable to that of anthralin.

Effect of the inosine 5'-monophosphate dehydrogenase inhibitor BMS-566419 on renal fibrosis in unilateral ureteral obstruction in rats

Chronic allograft nephropathy (CAN) is a major cause of late allograft loss. One morphological characteristic of CAN is renal interstitial fibrosis. Mycophenolate mofetil (MMF), the inosine 5'-monophosphate dehydrogenase (IMPDH) inhibitor, has been reported to attenuate the progression of renal interstitial fibrosis. However, the question of whether the newly synthesized IMPDH inhibitors with structures different from MMF have an antifibrotic effect remains unanswered. We evaluated the antifibrotic effects of BMS-566419, a chemically synthesized IMPDH inhibitor, using an experimental rat model, unilateral ureteral obstruction (UUO), in comparison with those of MMF. Expression levels of monocyte chemoattractant protein-1 (MCP-1) and transforming growth factor-beta1 (TGF-β1), which play important roles in UUO-induced renal fibrosis, were also investigated to determine the mechanism by which BMS-566419 affects the progression of renal fibrosis. After 14 days of UUO, interstitial fibrosis was frequently observed in the renal cortex of rats administered vehicle control. BMS-566419 by oral administration showed a significant and dose-dependent suppressive effect on UUO-induced renal fibrosis in histopathological experiments. BMS-566419 treatment also decreased collagen content, as indicated by hydroxyproline concentration, and the expression of collagen type 1 mRNA. BMS-566419 also decreased the expression of mRNA for both MCP-1 and TGF-β1. The antifibrotic effects of treatment with BMS-566419 at 60 mg/kg seemed comparable to those with MMF at 40 mg/kg. These results suggest that BMS-566419 and other chemically synthesized IMPDH inhibitors have beneficial pharmacological effects similar to those of MMF, and are potential pharmaceutical candidates in the treatment of fibrotic renal disease, including CAN.

Dual inhibitors of inosine monophosphate dehydrogenase and histone deacetylase based on a cinnamic hydroxamic acid core structure

Small molecules that act on multiple biological targets have been proposed to combat the drug resistance commonly observed for cancer chemotherapy. By combining the structural features of known inhibitors of inosine monophosphate dehydrogense (IMPDH) and histone deacetylase (HDAC), dual inhibitors of IMPDH and HDAC based on the scaffold of cinnamic hydroxamic acid (CHA) have been designed, synthesized, and evaluated in biological assays. Key features, including the linker length, linker functionality, substitution position, and interacting groups, have been explored. Their individual contribution to the inhibitory activities against human IMPDH1 and IMPDH2 as well as HDAC has been assessed.

Synthesis of new acridone derivatives, inhibitors of NS3 helicase, which efficiently and specifically inhibit subgenomic HCV replication

A new goup of acridone derivatives, obtained by reaction of acridone-4-carboxylic acid derivatives with aromatic amines, was tested to determine the inhibitory properties toward the NS3 helicase of hepatitis C virus (HCV). Six compounds inhibited the NS3 helicase at low concentrations (IC(50) from 1.5 to 20 microM). The acridone derivatives probably act via intercalation into double-stranded nucleic acids with a strong specificity for double-stranded RNA, although an interaction with the enzyme cannot be excluded. Testing in the subgenomic HCV replicon system revealed that compounds 10 and 13 are efficient RNA replication inhibitors, with EC(50) of 3.5 and 1 microM and therapeutic indexes of >28 and 20, respectively. Compound 16, with EC(50) < 1 microM and TI > 1000, is extremely specific and practically noncytotoxic at the concentrations tested, proving that the acridone derivatives may be regarded as potential antiviral agents. Although the mechanism of action of 16 in the replicon system remains unclear, it is the key lead compound for further development of anti-HCV drugs.

Effect of the inosine 5'-monophosphate dehydrogenase inhibitor BMS-566419 on rat cardiac allograft rejection

Inosine 5'-monophosphate dehydrogenase (IMPDH) inhibition is a critical target in solid organ transplantation, and the development of mycophenolate mofetil (MMF) represents a major advance in transplant medicine. In this study, the in vitro and in vivo pharmacological effects of BMS-566419, a novel chemically synthesized IMPDH inhibitor, were compared to those of mycophenolic acid (MPA) and MMF based on results from several immunological experiments. The in vitro inhibitory activity of BMS-566419 on IMPDH type I/II, immune cell proliferation and antibody production from lipopolysaccharide (LPS)-stimulated B cells was similar, albeit slightly less potent than that of MPA. In a rat heterotopic cardiac transplant model, monotherapy using orally administered BMS-566419 60mg/kg or MMF 40mg/kg prolonged the median survival time (MST) of transplanted grafts in the vehicle group from 5 to 18 and 18.5 days, respectively. In the presence of a sub-therapeutic dose of FK506, BMS-566419 30mg/kg and MMF 20mg/kg showed identical efficacy with an MST of 21.5 days. In dinitrophenol-LPS-stimulated rats in which calcineurin inhibitors failed to inhibit antibody production, in vivo oral administration of BMS-566419 resulted in antibody production suppression with similar efficacy to MMF. The in vivo antibody production against alloantigen was also suppressed by MMF or BMS-566419 treatment. In addition, gastrointestinal toxicity, considered a dose-limiting factor of MMF, was reduced in BMS-566419 treatment. These results suggest that BMS-566419 and other chemically synthesized IMPDH inhibitors have beneficial pharmacological effects similar to those of MMF, and are potential pharmaceutical candidates in transplant indications.

Synthesis and evaluation of N-substituted acridones as antiviral agents against haemorrhagic fever viruses

BACKGROUND

In the present study, a series of N-substituted acridone derivatives was synthesized and evaluated against two haemorrhagic fever viruses (HFV).

METHODS

Compounds were tested against Junin virus (JUNV), an arenavirus agent of Argentine haemorrhagic fever, and dengue virus (DENV), a flavivirus agent of the most prevalent arthropod-borne viral disease in humans.

RESULTS

Among tested compounds, two N-allyl acridones (derivatives 3c and 3f) elicited a potent and selective antiviral activity against JUNV (strain 1V4454) and DENV-2 (strain NGC) with 50% effective concentration values between 2.5 and 5.5 microM, as determined by virus yield inhibition. No cytotoxicity was detected at concentrations up to 1,000 microM, resulting in selectivity indices >181.8-400.0. Both acridones were effective against a wide spectrum of arenaviruses and the four serotypes of DENV. Furthermore, 3c and 3f failed to inactivate virus before cell infection as well as to induce a refractory state by cell pretreatment, indicating that the inhibitory effect was exerted through a blockade in virus multiplication during the infectious process.

CONCLUSION

These data are the first demonstration that acridone derivatives have a potent antiviral activity that block in vitro multiplication of HFV belonging to Arenaviridae and Flaviviridae, such as JUNV and DENV.