Synthesis of the inosine 5′-monophosphate dehydrogenase (IMPDH) inhibitors

Approaches Towards Better Immunosuppressive Agents

Several classes of compounds are applied in clinics due to their immunosuppressive properties in transplantology and the treatment of autoimmune diseases. Derivatives of mycophenolic acid, corticosteroids and chemotherapeutics bearing heterocyclic moieties like methotrexate, azathioprine, mizoribine, and ruxolitinib are active substances with investigated mechanisms of action. However, improved synthetic approaches of known drugs and novel derivatives are still being reported to attempt better accessibility and therapeutic properties. In this review article, we present the synthesis of the designed chemical structures based on recent literature reports concerning novel compounds as promising immunosuppressive drugs. Moreover, some of the discussed derivers revealed also other types of activities with prospective medicinal potential.

The roles of HDAC with IMPDH and mTOR with JAK as future targets in the treatment of rheumatoid arthritis with combination therapy

Various studies have shown that cytokines are important regulators in rheumatoid arthritis (RA). In synovial inflammation alteration of the enzyme HDAC, IMPDH enzyme, mTOR pathway, and JAK pathway increase cytokine level. These increased cytokine levels are responsible for the inflammation in RA. Inflammation is a physiological and normal reaction of the immune system against dangerous stimuli such as injury and infection. The cytokine-based approach improves the treatment of RA. To reach this goal, various researchers and scientists are working more aggressively by using a combination approach. The present review of combination therapy provides essential evidence about the possible synergistic effect of combinatorial agents. We have focused on the effects of HDAC inhibitor with IMPDH inhibitor and mTOR inhibitor with JAK inhibitor in combination for the treatment of RA. Combining various targeted strategies can be helpful for the treatment of RA.

Validating Interactions of Pathogenic Proteins of Staphylococcus aureus and E. coli with Phytochemicals of Ziziphus jujube and Acacia nilotica

This study focused on the assessment of the antimicrobial resistance of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) isolated from bovine mastitis milk samples and the revealing anti-mastitis potential of phytocompounds of Ziziphus jujube and Acacia nilotica through molecular docking analysis. The mastitis milk samples were collected from various dairy farms for the isolation of the bacteria (S. aureus and E. coli) and their response to antibiotics. Ethanolic extracts of both plants were prepared. Their antibacterial activity was evaluated, and they were processed for phytochemical analysis after which, molecular docking analysis with pathogenic proteins of the bacteria was carried out. Parametric and non-parametric statistical analyses were performed to reach the conclusions of this study. The findings of the study revealed a higher drug resistance (≥40%) of E. coli against ampicillin, amikacin, and vancomycin, while S. aureus exhibited the highest resistance to ampicillin, erythromycin, and ciprofloxacin. The ethanolic extracts of the Ziziphus jujube and Acacia nilotica plants produced a ZOI between 18 and 23 mm against multidrug-resistant S. aureus and E. coli. Gas chromatography-mass spectrophotometry (GC-MS) was used to explore 15 phytocompounds from Ziziphus jujube and 18 phytocompounds from Acacia nilotica. The molecular docking analysis of 2cyclopenten-1-one,3,4,4 trimethyl and Bis (2ethylhexyl) phthalate of Ziziphus jujube showed a binding affinity of -4.8 kcal/mol and -5.3 kcal/mol and -5.9 kcal/mol and -7.1 kcal/mol against the DNA Gyrase and toxic shock syndrome toxin-1 proteins of S. aureus and E. coli, respectively. The suberic acid monomethyl ester of Acacia nilotica showed a binding affinity of -5.9 kcal/mol and -5 kcal/mol against the outer membrane protein A and Topoisomerase IV protein of E. coli and -5.1 kcal/mol and -5.8 kcal/mol against the toxic shock syndrome toxin-1 and Enterotoxin B proteins of S. aureus. Similarly, 2,2,4-trimethyl-1,3-pentanediol di-iso-butyrate showed a binding affinity of -6.5 kcal/mol and -5.3 kcal/mol against the outer membrane protein A and Topoisomerase IV of E. coli and -5.2 kcal/mol and -5.9 kcal/mol against the toxic shock syndrome toxin-1 and Enterotoxin B proteins of S. aureus, respectively. The study concluded that there was an increasing trend for the antimicrobial resistance of S. aureus and E. coli, while the Ziziphus jujube and Acacia nilotica plant extracts expressed significant affinity to tackle this resistance; hence, this calls for the development of novel evidence-based therapeutics.

Synthesis and Biological Evaluation of Novel Anti-leukemia Proteolysis-Targeting Chimeras in Degradating Inosine Monophosphate Dehydrogenase

Background

Proteolysis-targeting chimera (PROTAC) is a bifunctional molecule comprising a ligand to recognize the targeted protein to be degraded.

Objectives

To use the advantages of the PROTAC technique, we have synthesized novel compounds to degrade inosine monophosphate dehydrogenase (IMPDH) by the proteasome system.

Methods

We describe the synthesis of new PROTACs based on a combination of mycophenolic acid (MPA) as the potent IMPDH inhibitor and pomalidomide as a ligand of E3 ubiquitin ligase via linkers formed from Cu(I)-catalyzed cycloaddition reaction.

Results

All synthesized compounds were investigated against Jurkat cells as acute T-cell leukemia and were potent apoptosis inducers at 50 nM.

Conclusion

The effect of compound 2 in 0.05 μM on IMPDH degradation can be almost prevented by competition with bortezomib as the proteasome inhibitor at 0.1 and 0.5 μM.

Novel amides of mycophenolic acid and some heterocyclic derivatives as immunosuppressive agents

The group of 18 new amide derivatives of mycophenolic acid (MPA) and selected heterocyclic amines was synthesised as potential immunosuppressive agents functioning as inosine-5′-monophosphate dehydrogenase (IMPDH) uncompetitive inhibitors. The synthesis of 14 of them employed uronium-type activating system (TBTU/HOBt/DIPEA) while 4 of them concerned phosphonic acid anhydride method (T3P/Py) facilitating amides to be obtained in moderate to excellent yields without the need of phenolic group protection. Most of optimised protocols did not require complicated reaction work-ups, including chromatographic, solvent-consuming methods. The biological activity assay was performed on the T-Jurkat cell line and peripheral mononuclear blood cells (PBMCs) which are both dedicated for antiproliferative activity determination. Each of designed derivatives was characterised by reduced cytotoxicity and benzoxazole analogue (A2) revealed the most promising activity. Subsequently, an observed structure-activity relationship was discussed.

Inhibitors of Nucleotide Biosynthesis as Candidates for a Wide Spectrum of Antiviral Chemotherapy

Emerging and re-emerging viruses have been a challenge in public health in recent decades. Host-targeted antivirals (HTA) directed at cellular molecules or pathways involved in virus multiplication represent an interesting strategy to combat viruses presently lacking effective chemotherapy. HTA could provide a wide range of agents with inhibitory activity against current and future viruses that share similar host requirements and reduce the possible selection of antiviral-resistant variants. Nucleotide metabolism is one of the more exploited host metabolic pathways as a potential antiviral target for several human viruses. This review focuses on the antiviral properties of the inhibitors of pyrimidine and purine nucleotide biosynthesis, with an emphasis on the rate-limiting enzymes dihydroorotate dehydrogenase (DHODH) and inosine monophosphate dehydrogenase (IMPDH) for which there are old and new drugs active against a broad spectrum of pathogenic viruses.

Aspergichromones A-E, Five Chromone Derivatives with Complicated Polycyclic Architecture from Aspergillus deflectus

Five unprecedented chromone derivatives involving a 6/6/5/5/5/6 hexacyclic scaffold (1, 2), 6/6/5/6/6/6/6 heptacyclic scaffold (3), and 6/6/6/5/5/6 hexacyclic scaffold (4, 5) were obtained from the fungus Aspergillus deflectus NCC0415. Their structures were identified using comprehensive spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Except for 3, the other compounds, especially the 6/6/6/5/5/6 hexacyclic derivatives (4 and 5), exhibited potent inosine-5'-monophosphate dehydrogenase (IMPDH) inhibitory activities.

Anticancer Properties of Amino Acid and Peptide Derivatives of Mycophenolic Acid

BACKGROUND

Although Mycophenolic Acid (MPA) is applied as prodrugs in clinic as an immunosuppressant, it also possesses anticancer activity. MPA acts as Inosine-5'-Monophosphate Dehydrogenase (IMPDH) inhibitor, where the carboxylic group at the end of the side chain interacts with Ser 276 of the enzyme via hydrogen bonds. Therefore, MPA derivatives with other polar groups indicated high inhibition too. On the other hand, potent anticancer agents like dacarbazine and cisplatin give numerous side-effects.

OBJECTIVE

Based on the literature data, MPA derivatives should be explored towards anticancer properties. Conversion of the carboxylic group of MPA to amide could maintain antiproliferative activity. Therefore, we decided to investigate several amino acid and peptide derivatives of MPA against chosen cancer cell lines in vitro.

METHODS

Amides of MPA hold threonine and arginine amino acid unit. These amino acid derivatives were tested as L and D enantiomers and both in free acid and methyl esters forms. Additionally, MPA was modified with tuftsin or retro-tuftsin as biologically active peptides, which could act as a drug carrier.

RESULTS

Amino acid and peptide derivatives of MPA were investigated in vitro as potential anticancer agents on cell lines: Ab melanoma, A375 melanoma and SHSY5Y neuroblastoma. The activity of the tested compounds was compared to parent MPA and known chemotherapeutics: dacarbazine and cisplatin.

CONCLUSION

Amino acid moiety and the sequence of amino acids in the peptide part influenced observed activity. The most active amino acid MPA analogues occurred to be D and L-threonine derivatives as methyl esters, probably due to better cell membrane penetration.

Immunosuppressive properties of amino acid and peptide derivatives of mycophenolic acid

Mycophenolic acid (MPA) was coupled with amino acids and biologically active peptides including derivatives of tuftsin to modify its immunosuppressive properties. Both amino acid unit in the case of simple MPA amides and modifications within peptide moiety of MPA - tuftsin conjugates influenced the observed activity. Antiproliferative potential of the obtained conjugates was investigated in vitro and MPA amides with threonine methyl ester and conjugate of MPA with retro-tuftisin occurred to be more selective against PBMC in comparison to parent MPA. Both amino acid and peptide derivatives of MPA acted as inosine-5'-monophosphate dehydrogenaze (IMPDH) inhibitors.

Synthesis and antiproliferative activity of new mycophenolic acid conjugates with adenosine derivatives

New conjugates of mycophenolic acid (MPA) and adenosine derivatives were synthesized and assessed as potential immunosuppressants on Jurkat cell line and peripheral blood mononuclear cells (PBMC) from healthy donors. As compared to MPA, all compounds were found to be more active against Jurkat cell line. The antiproliferative activities were compared with MPA and adenosine, in both 2',3'-O-isopropylidene protected and free hydroxyl groups possessing forms. The obtained results were also discussed in terms of selectivity index, defined as SI = IC₅₀/EC₅₀.

Discovery of novel human inosine 5'-monophosphate dehydrogenase 2 (hIMPDH2) inhibitors as potential anticancer agents

The enzyme inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes an essential step in the de novo biosynthesis of guanine nucleotides, and thus regulates the guanine nucleotide pool required for cell proliferation. Of the two isoforms, human IMPDH type 2 (hIMPDH2) is a validated molecular target for potential immunosuppressive, antiviral and anticancer chemotherapy. In search of newer hIMPDH2 inhibitors as potential anticancer agents, three novel series (A: 5-aminoisobenzofuran-1(3H)-one, B: 3,4-dimethoxyaniline and C: benzo[d]-[1,3]dioxol-5-ylmethanamine) were synthesized and evaluated for in vitro and cell-based activities. A total of 37 molecules (29-65) were screened for their in vitro hIMPDH2 inhibition, with particular emphasis on establishing their structure-activity relationship (SAR) trends. Eight compounds (hits, 30, 31, 33-35, 37, 41 and 43) demonstrated significant enzyme inhibition (>70% @ 10 μM); especially the A series molecules were more potent than B series (<70% inhibition @ 10 μM), while C series members were found to be inactive. The hIMPDH2 IC₅₀ values for the hits ranged from 0.36 to 7.38 μM. The hits displaying >80% hIMPDH2 inhibition (30, 33, 35, 41 and 43) were further assessed for their cytotoxic activity against cancer cell lines such as MDA-MB-231 (breast adenocarcinoma), DU145 (prostate carcinoma), U87 MG (glioblastoma astrocytoma) and a normal cell line, NIH-3T3 (mouse embryonic fibroblast) using MTT assay. Most of the compounds exhibited higher cellular potency against cancer cell lines and notably lower toxicity towards NIH-3T3 cells compared to mycophenolic acid (MPA), a prototypical hIMPDH2 inhibitor. Two of the series A hits (30 and 35) were evaluated in human peripheral blood mononuclear cells (hPBMC) assay and found to be better tolerated than MPA. The calculated/predicted molecular and physicochemical properties were satisfactory with reference to drug-likeness. The molecular docking studies clearly demonstrated crucial interactions of the hits with the cofactor-binding site of hIMPDH2, further providing critical information for refining the design strategy. The present study reports the design and discovery of structurally novel hIMPDH2 inhibitors as potential anticancer agents and provides a guide for further research on the development of safe and effective anticancer agents, especially against glioblastoma.

Newer human inosine 5'-monophosphate dehydrogenase 2 (hIMPDH2) inhibitors as potential anticancer agents

Human inosine 5′-monophosphate dehydrogenase 2 (hIMPDH2), being an age-old target, has attracted attention recently for anticancer drug development. Mycophenolic acid (MPA), a well-known immunosuppressant drug, was used a lead structure to design and develop modestly potent and selective analogues. The steep structure–activity relationship (SAR) requirements of the lead molecule left little scope to synthesise newer analogues. Here, newer MPA amides were designed, synthesised and evaluated for hIMPDH2 inhibition and cellular efficacy in breast, prostate and glioblastoma cell lines. Few title compounds exhibited cellular activity profile better than MPA itself. The observed differences in the overall biological profile could be attributed to improved structural and physicochemical properties of the analogues over MPA. This is the first report of the activity of MPA derivatives in glioblastoma, the most aggressive brain cancer.

Synthesis and antimicrobial activity of amino acid and peptide derivatives of mycophenolic acid

The series of 16 novel amino acid and peptide mycophenolic acid (MPA) derivatives was obtained as potential antibacterial agents. Coupling of MPA with respective amines was optimized with condensing reagents such as EDCI/DMAP and T3P/TEA. Amino acid analogs were received both as methyl esters and also with the free carboxylic group. The biological activity of the products was tested on five references bacterial strains: Klebsiella pneumoniae ATCC 700603 (ESBL), Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus MRSA ATCC 43300, Staphylococcus aureus MSSA ATCC 25923. Peptide derivatives proved to be the most versatile ones, their MIC values relative to most strains was lower than MPA alone. It has been noted that the activity of amino acid derivatives depends on the configuration at the chiral center in the amino acid unit and methyl esters indicated better antimicrobial activity than analogs with free carboxylic group.

New conjugates of mycophenolic acid and their antiproliferative activity

The new conjugates of mycophenolic acid (MPA) were obtained in the reaction of N(6)-(ω-aminoalkyl)adenosines with MPA in the presence of EDCI as a coupling reagent. New compounds 4a-h were evaluated on leukemia cell line (Jurkat) and PBMC from healthy donors. Length of the linker influenced observed activity. The compound 4b possessing 1,3-diamine spacer exhibited the most promising results and can be considered to further investigations.

Viral Polymerase-Helicase Complexes Regulate Replication Fidelity To Overcome Intracellular Nucleotide Depletion

To date, the majority of work on RNA virus replication fidelity has focused on the viral RNA polymerase, while the potential role of other viral replicase proteins in this process is poorly understood. Previous studies used resistance to broad-spectrum RNA mutagens, such as ribavirin, to identify polymerases with increased fidelity that avoid misincorporation of such base analogues. We identified a novel variant in the alphavirus viral helicase/protease, nonstructural protein 2 (nsP2) that operates in concert with the viral polymerase nsP4 to further alter replication complex fidelity, a functional linkage that was conserved among the alphavirus genus. Purified chikungunya virus nsP2 presented delayed helicase activity of the high-fidelity enzyme, and yet purified replication complexes manifested stronger RNA polymerization kinetics. Because mutagenic nucleoside analogs such as ribavirin also affect intracellular nucleotide pools, we addressed the link between nucleotide depletion and replication fidelity by using purine and pyrimidine biosynthesis inhibitors. High-fidelity viruses were more resistant to these conditions, and viral growth could be rescued by the addition of exogenous nucleosides, suggesting that mutagenesis by base analogues requires nucleotide pool depletion. This study describes a novel function for nsP2, highlighting the role of other components of the replication complex in regulating viral replication fidelity, and suggests that viruses can alter their replication complex fidelity to overcome intracellular nucleotide-depleting conditions.

IMPORTANCE

Previous studies using the RNA mutagen ribavirin to select for drug-resistant variants have highlighted the essential role of the viral RNA-dependent RNA polymerase in regulating replication fidelity. However, the role of other viral replicase components in replication fidelity has not been studied in detail. We identified here an RNA mutagen-resistant variant of the nsP2 helicase/protease that conferred increased fidelity and yet could not operate in the same manner as high-fidelity polymerases. We show that the alphavirus helicase is a key component of the fidelity-regulating machinery. Our data show that the RNA mutagenic activity of compounds such as ribavirin is coupled to and potentiated by nucleotide depletion and that RNA viruses can fine-tune their replication fidelity when faced with an intracellular environment depleted of nucleotides.

Synthesis and biological activity of ester derivatives of mycophenolic acid and acridines/acridones as potential immunosuppressive agents

Improved derivatives of mycophenolic acid (MPA) are necessary to reduce the frequency of adverse effects, this drug exerts in treated patients. In this study, MPA was coupled with N-(ω-hydroxyalkyl)-9-acridone-4-carboxamides or N-(ω-hydroxyalkyl)acridine-4-carboxamides to give respective ester conjugates upon Yamaguchi protocol. This esterification required protection of phenol group in MPA. Designed conjugates revealed higher potency in vitro than parent MPA. Acridine derivatives were more active than acridone analogs and length of the alkyl linker between MPA and heterocyclic units influenced the observed cytotoxicity. Derivatives 2b, 2d, 3a, 3b displayed the most promising immunosuppressive activity.