Discovery of N-(6-Fluoro-1-oxo-1,2-dihydroisoquinolin-7-yl)-5-[(3R)-3-hydroxypyrrolidin-1-yl]thiophene-2-sulfonamide (LSN 3213128), a Potent and Selective Nonclassical Antifolate Aminoimidazole-4-carboxamide Ribonucleotide Formyltransferase (AICARFT) Inhibitor Effective at Tumor Suppression in a Cancer Xenograft Model

Structure-Based Design of Transport-Specific Multitargeted One-Carbon Metabolism Inhibitors in Cytosol and Mitochondria

Multitargeted agents provide tumor selectivity with reduced drug resistance and dose-limiting toxicities. We previously described the multitargeted 6-substituted pyrrolo[3,2-d]pyrimidine antifolate 1 with activity against early- and late-stage pancreatic tumors with limited tumor selectivity. Structure-based design with our human serine hydroxymethyl transferase (SHMT) 2 and glycinamide ribonucleotide formyltransferase (GARFTase) structures, and published X-ray crystal structures of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC), SHMT1, and folate receptor (FR) α and β afforded 11 analogues. Multitargeted inhibition and selective tumor transport were designed by providing promiscuous conformational flexibility in the molecules. Metabolite rescue identified mitochondrial C1 metabolism along with de novo purine biosynthesis as the targeted pathways. We identified analogues with tumor-selective transport via FRs and increased SHMT2, SHMT1, and GARFTase inhibition (28-, 21-, and 11-fold, respectively) compared to 1. These multitargeted agents represent an exciting new structural motif for targeted cancer therapy with substantial advantages of selectivity and potency over clinically used antifolates.

Structure based drug design and fragment based approach to identify potential methotrexate analogues as dual inhibitors for management of psoriasis

Psoriasis is characterized as chronic inflammatory disorder of skin having unregulated hyperproliferation and shedding of plaques. As per first line treatment methotrexate is the most widely used cytotoxic drug for psoriasis. It shows anti-proliferative effect with hDHFR while anti-inflammatory and immunosuppressive action is due to AICART. Serious hepatotoxic effects are recognized with long-term treatment of methotrexate. In this study, in silico technique is used in this work to find Dual-Acting Methotrexate-like molecules with increased efficacy and decreased toxicity. Structure-based virtual screening assisted by a fragment-based method against a library of chemicals that are similar to methotrexate revealing 36 and 27 potential inhibitors of hDHFR and AICART respectively. Further, based on dock score, binding energy, molecular interactions, and ADME/T analysis compound 135565151 was chosen for dynamic stability evaluation. Overall, these findings provided information on possible methotrexate analogues for the treatment of psoriasis that had lower hepatotoxicity.Communicated by Ramaswamy H. Sarma.

Purine synthesis suppression reduces the development and progression of pulmonary hypertension in rodent models

AIMS

Proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of pulmonary hypertension (PH). Proliferative cells utilize purine bases from the de novo purine synthesis (DNPS) pathways for nucleotide synthesis; however, it is unclear whether DNPS plays a critical role in VSMC proliferation during development of PH. The last two steps of DNPS are catalysed by the enzyme 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC). This study investigated whether ATIC-driven DNPS affects the proliferation of pulmonary artery smooth muscle cells (PASMCs) and the development of PH.

METHODS AND RESULTS

Metabolites of DNPS in proliferative PASMCs were measured by liquid chromatography-tandem mass spectrometry. ATIC expression was assessed in platelet-derived growth factor-treated PASMCs and in the lungs of PH rodents and patients with pulmonary arterial hypertension. Mice with global and VSMC-specific knockout of Atic were utilized to investigate the role of ATIC in both hypoxia- and lung interleukin-6/hypoxia-induced murine PH. ATIC-mediated DNPS at the mRNA, protein, and enzymatic activity levels were increased in platelet-derived growth factor-treated PASMCs or PASMCs from PH rodents and patients with pulmonary arterial hypertension. In cultured PASMCs, ATIC knockdown decreased DNPS and nucleic acid DNA/RNA synthesis, and reduced cell proliferation. Global or VSMC-specific knockout of Atic attenuated vascular remodelling and inhibited the development and progression of both hypoxia- and lung IL-6/hypoxia-induced PH in mice.

CONCLUSION

Targeting ATIC-mediated DNPS compromises the availability of purine nucleotides for incorporation into DNA/RNA, reducing PASMC proliferation and pulmonary vascular remodelling and ameliorating the development and progression of PH.

ATIC-Associated De Novo Purine Synthesis Is Critically Involved in Proliferative Arterial Disease

BACKGROUND

Proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of arterial diseases, especially in arterial restenosis after angioplasty or stent placement. VSMCs reprogram their metabolism to meet the increased requirements of lipids, proteins, and nucleotides for their proliferation. De novo purine synthesis is one of critical pathways for nucleotide synthesis. However, its role in proliferation of VSMCs in these arterial diseases has not been defined.

METHODS

De novo purine synthesis in proliferative VSMCs was evaluated by liquid chromatography-tandem mass spectrometry. The expression of ATIC (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase), the critical bifunctional enzyme in the last 2 steps of the de novo purine synthesis pathway, was assessed in VSMCs of proliferative arterial neointima. Global and VSMC-specific knockout of Atic mice were generated and used for examining the role of ATIC-associated purine metabolism in the formation of arterial neointima and atherosclerotic lesions.

RESULTS

In this study, we found that de novo purine synthesis was increased in proliferative VSMCs. Upregulated purine synthesis genes, including ATIC, were observed in the neointima of the injured vessels and atherosclerotic lesions both in mice and humans. Global or specific knockout of Atic in VSMCs inhibited cell proliferation, attenuating the arterial neointima in models of mouse atherosclerosis and arterial restenosis.

CONCLUSIONS

These results reveal that de novo purine synthesis plays an important role in VSMC proliferation in arterial disease. These findings suggest that targeting ATIC is a promising therapeutic approach to combat arterial diseases.

Pharmacokinetics, bioavailability, and plasma protein binding study of glytrexate, a novel multitarget antifolate

Glytrexate, developed by our team, as a novel multitarget folate antagonist, has inhibitory effects on a variety of cancer cell types, especially KB tumor cells (IC₅₀ 0.078 nM), and thus has antitumor drug development prospects. However, its pharmacokinetics and plasma protein binding properties remain unknown. In this study a selective and sensitive liquid chromatography-tandem mass spectrometry (LC‒MS/MS) method was developed and verified to facilitate biological analysis. The bioanalysis method was applied to evaluate the stability, plasma protein binding, and pharmacokinetics of glytrexate. Glytrexate is more stable in human plasma than in rat plasma and in human liver microsomes. The binding of glytrexate to human plasma proteins was higher than that to rat plasma proteins, both of which were less than 30%, suggesting that glytrexate may be at a higher concentration at the pharmacologic target receptor(s) in tissues. Pharmacokinetic characteristics were determined by noncompartmental analysis after administration of single oral (12.5, 25 and 50 mg/kg) and intravenous (2 mg/kg) doses in rats. According to the rat oral pharmacokinetic characteristics, glytrexate had linear dynamics in a dose range of 12.5–50 mg/kg and a poor oral bioavailability of 0.57–1.15%. The investigation revealed that the intravenous half-life, AUC, and C_max of glytrexate were higher than those of pemetrexed. Pemetrexed is generally produced as an injection preparation. This provides ideas for the development of glytrexate formulations. Therefore, glytrexate injection has clinical application prospects compared to oral administration. This study provides a basis for further investigations into the pharmacological effects and clinical uses of glytrexate.

Genetic variations in methotrexate metabolic pathway genes influence methotrexate responses in rheumatoid arthritis patients in Malaysia

Methotrexate (MTX) is the most widely used disease-modifying anti-rheumatic drug (DMARD) for rheumatoid arthritis (RA). Many studies have attempted to understand the genetic risk factors that affect the therapeutic outcomes in RA patients treated with MTX. Unlike other studies that focus on the populations of Caucasians, Indian and east Asian countries, this study investigated the impacts of six single nucleotide polymorphisms (SNPs) that are hypothesized to affect the outcomes of MTX treatment in Malaysian RA patients. A total of 647 RA patients from three ethnicities (N_Malay = 153; N_Chinese = 326; N_Indian = 168) who received MTX monotherapy (minimum 15 mg per week) were sampled from three hospitals in Malaysia. SNPs were genotyped in patients using TaqMan real-time PCR assay. Data obtained were statistically analysed for the association between SNPs and MTX efficacy and toxicity. Analysis of all 647 RA patients indicated that none of the SNPs has influence on either MTX efficacy or MTX toxicity according to the Chi-square test and binary logistic regression. However, stratification by self-identified ancestries revealed that two out of six SNPs, ATIC C347G (rs2372536) (OR 0.5478, 95% CI 0.3396–0.8835, p = 0.01321) and ATIC T675C (rs4673993) (OR 0.5247, 95% CI 0.3248–0.8478, p = 0.008111), were significantly associated with MTX adequate response in RA patients with Malay ancestry (p < 0.05). As for the MTX toxicity, no significant association was identified for any SNPs selected in this study. Taken all together, ATIC C347G and ATIC T675C can be further evaluated on their impact in MTX efficacy using larger ancestry-specific cohort, and also incorporating high-order gene–gene and gene–environment interactions.

Survival-Associated Metabolic Genes and Risk Scoring System in HER2-Positive Breast Cancer

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer and triple-negative breast cancer have their own genetic, epigenetic, and protein expression profiles. In the present study, based on bioinformatics techniques, we explored the prognostic targets of HER2-positive breast cancer from metabonomics perspective and developed a new risk score system to evaluate the prognosis of patients. By identifying the differences between HER2 positive and normal control tissues, and between triple negative breast cancer and normal control tissues, we found a large number of differentially expressed metabolic genes in patients with HER2-positive breast cancer and triple-negative breast cancer. Importantly, in HER2-positive breast cancer, decreased expression of metabolism-related genes ATIC, HPRT1, ASNS, SULT1A2, and HAL was associated with increased survival. Interestingly, these five metabolism-related genes can be used to construct a risk score system to predict overall survival (OS) in HER2-positive patients. The time-dependent receiver operating characteristic (ROC) curve analysis showed that the predictive sensitivity of the risk scoring system was higher than that of other clinical factors, including age, stage, and tumor node metastasis (TNM) stage. This work shows that specific transcriptional changes in metabolic genes can be used as biomarkers to predict the prognosis of patients, which is helpful in implementing personalized treatment and evaluating patient prognosis.

Current Status of the Use of Multifunctional Enzymes as Anti-Cancer Drug Targets

Fighting cancer is one of the major challenges of the 21st century. Among recently proposed treatments, molecular-targeted therapies are attracting particular attention. The potential targets of such therapies include a group of enzymes that possess the capability to catalyze at least two different reactions, so-called multifunctional enzymes. The features of such enzymes can be used to good advantage in the development of potent selective inhibitors. This review discusses the potential of multifunctional enzymes as anti-cancer drug targets along with the current status of research into four enzymes which by their inhibition have already demonstrated promising anti-cancer effects in vivo, in vitro, or both. These are PFK-2/FBPase-2 (involved in glucose homeostasis), ATIC (involved in purine biosynthesis), LTA₄H (involved in the inflammation process) and Jmjd6 (involved in histone and non-histone posttranslational modifications). Currently, only LTA₄H and PFK-2/FBPase-2 have inhibitors in active clinical development. However, there are several studies proposing potential inhibitors targeting these four enzymes that, when used alone or in association with other drugs, may provide new alternatives for preventing cancer cell growth and proliferation and increasing the life expectancy of patients.

The Intersection of Purine and Mitochondrial Metabolism in Cancer

Nucleotides are essential to cell growth and survival, providing cells with building blocks for DNA and RNA, energy carriers, and cofactors. Mitochondria have a critical role in the production of intracellular ATP and participate in the generation of intermediates necessary for biosynthesis of macromolecules such as purines and pyrimidines. In this review, we highlight the role of purine and mitochondrial metabolism in cancer and how their intersection influences cancer progression, especially in ovarian cancer. Additionally, we address the importance of metabolic rewiring in cancer and how the evolving landscape of purine synthesis and mitochondria inhibitors can be potentially exploited for cancer treatment.

Synthesis of Isoquinolones by Sequential Suzuki Coupling of 2-Halobenzonitriles with Vinyl Boronate Followed by Cyclization

A novel, facile, and expeditious two-step synthesis of 3,4-unsubstituted isoquinolin-1(2H)-ones from a Suzuki cross-coupling between 2-halobenzonitriles and commercially available vinyl boronates followed by platinum-catalyzed nitrile hydrolysis and cyclization is described.

PAICS, a Purine Nucleotide Metabolic Enzyme, is Involved in Tumor Growth and the Metastasis of Colorectal Cancer

The identification of colorectal cancer (CRC) molecular targets is needed for the development of drugs that improve patient survival. We investigated the functional role of phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS), a de novo purine biosynthetic enzyme involved in DNA synthesis, in CRC progression and metastasis by using cell and animal models. Its clinical utility was assessed in human CRC samples. The expression of PAICS was regulated by miR-128 and transcriptionally activated by Myc in CRC cells. Increased expression of PAICS was involved in proliferation, migration, growth, and invasion of CRC cells irrespective of the p53 and microsatellite status. In mice, the depletion of PAICS in CRC cells led to reduced tumor growth and metastatic cell dissemination to the liver, lungs, and bone. Positron emission tomography imaging showed significantly reduced metastatic lesions in stable PAICS knockdown CRC cells. In cells with PAICS knockdown, there was upregulation of the epithelial mesenchymal transition marker, E-cadherin, and bromodomain inhibitor, JQ1, can target its increased expression by blocking Myc. PAICS was overexpressed in 70% of CRCs, and was associated with poor 5-year survival independent of the pathologic stage, patient’s race, gender, and age. Overall, the findings point to the usefulness of PAICS targeting in the treatment of aggressive colorectal cancer.

Design, synthesis and biological activity of N5-substituted tetrahydropteroate analogs as non-classical antifolates against cobalamin-dependent methionine synthase and potential anticancer agents

Cobalamin-dependent methionine synthase (MetH) is involved in the process of tumor cell growth and survival. In this study, a novel series of N⁵-electrophilic substituted tetrahydropteroate analogs without glutamate residue were designed as non-classical antifolates and evaluated for their inhibitory activities against MetH. In addition, the cytotoxicity of target compounds was evaluated in human tumor cell lines. With N⁵-chloracetyl as the optimum group, further structure research on the benzene substituent and on the 2,4-diamino group was also performed. Compound 6c, with IC₅₀ value of 12.1 μM against MetH and 0.16-6.12 μM against five cancer cells, acted as competitive inhibitor of MetH. Flow cytometry studies indicated that compound 6c arrested HL-60 cells in the G₁-phase and then inducted late apoptosis. The molecular docking further explained the structure-activity relationship.

Dysregulation of de novo nucleotide biosynthetic pathway enzymes in cancer and targeting opportunities

Cancer is a disease of uncontrolled cell growth and a major cause of death worldwide. Many molecular events characterize tumor initiation and progression. Global gene expression analyses using next-generation sequencing, proteomics and metabolomics show genomic, epigenetic, and metabolite concentration changes in various tumors. Molecular alterations identified include multiple cancer-driving mutations, gene fusions, amplifications, deletions, and post-translational modifications. Data integration from many high-throughput platforms unraveled dysregulation in many metabolic pathways in cancer. Since cancer cells are fast-growing, their metabolic needs are enhanced, hence the requirement for de novo synthesis of essential metabolites. One critical requirement of fast-growing cells and a historically important pathway in cancer is the nucleotide biosynthetic pathway and its enzymes are valuable targets for small molecule inhibition. Purines and pyrimidines are building blocks of DNA synthesis and due to their excessive growth, cancer cells extensively utilize de novo pathways for nucleotide biosynthesis. Methotrexate, one of the early chemotherapeutic agents, targets dihydrofolate reductase of the folate metabolic pathway that is involved in nucleotide biosynthesis. In this review, we discuss the nucleotide biosynthetic pathways in cancer and targeting opportunities.

Folic Acid Antagonists: Antimicrobial and Immunomodulating Mechanisms and Applications

: Bacterial, protozoan and other microbial infections share an accelerated metabolic rate. In order to ensure a proper functioning of cell replication and proteins and nucleic acids synthesis processes, folate metabolism rate is also increased in these cases. For this reason, folic acid antagonists have been used since their discovery to treat different kinds of microbial infections, taking advantage of this metabolic difference when compared with human cells. However, resistances to these compounds have emerged since then and only combined therapies are currently used in clinic. In addition, some of these compounds have been found to have an immunomodulatory behavior that allows clinicians using them as anti-inflammatory or immunosuppressive drugs. Therefore, the aim of this review is to provide an updated state-of-the-art on the use of antifolates as antibacterial and immunomodulating agents in the clinical setting, as well as to present their action mechanisms and currently investigated biomedical applications.

Synthesis of 4-Iodoisoquinolin-1(2 H)-ones by a Dirhodium(II)-Catalyzed 1,4-Bisfunctionalization of Isoquinolinium Iodide Salts

An efficient Rh₂(II,II)-catalyzed reaction has been developed under mild conditions. This synthetic method proceeds through iodination/oxidation of readily available isoquinolinium iodide salts under aerobic conditions with good to excellent yields. 4-Iodoisoquinolin-1(2 H)-ones are important building blocks for biologically and medicinally important compounds. The developed methodology was applied to the gram-scale synthesis of a key intermediate in the synthesis of the CRTH2 antagonist CRA-680.

Characterization of a novel AICARFT inhibitor which potently elevates ZMP and has anti-tumor activity in murine models

AICARFT is a folate dependent catalytic site within the ATIC gene, part of the purine biosynthetic pathway, a pathway frequently upregulated in cancers. LSN3213128 is a potent (16 nM) anti-folate inhibitor of AICARFT and selective relative to TS, SHMT1, MTHFD1, MTHFD2 and MTHFD2L. Increases in ZMP, accompanied by activation of AMPK and cell growth inhibition, were observed with treatment of LY3213128. These effects on ZMP and proliferation were dependent on folate levels. In human breast MDA-MB-231met2 and lung NCI-H460 cell lines, growth inhibition was rescued by hypoxanthine, but not in the A9 murine cell line which is deficient in purine salvage. In athymic nude mice, LSN3213128 robustly elevates ZMP in MDA-MB-231met2, NCI-H460 and A9 tumors in a time and dose dependent manner. Significant tumor growth inhibition in human breast MDA-MB231met2 and lung NCI-H460 xenografts and in the syngeneic A9 tumor model were observed with oral administration of LSN3213128. Strikingly, AMPK appeared activated within the tumors and did not change even at high levels of intratumoral ZMP after weeks of dosing. These results support the evaluation of LSN3213128 as an antineoplastic agent.

New Antibacterial Bagremycins F and G from the Marine-Derived Streptomyces sp. ZZ745

As part of our research to discover novel bioactive natural products from marine microorganisms, five bagremycin analogues, including the previously unreported bagremycins F (1) and G (2), were isolated from a marine actinomycete Streptomyces sp. ZZ745. The structures of these compounds were determined by means of NMR spectroscopic analysis, HRESIMS data, and optical rotation. Both bagremycins F (1) and G (2) showed antibacterial activity against Escherichia coli, with MIC values of 41.8 and 61.7 μM, respectively.