Stereoselective Approach for the Synthesis of Diverse 1'-Modified Carbanucleosides

We describe an efficient and stereoselective synthesis of 1'-substituted-β-carbocylic nucleosides 5 via gem-dichlorooxirane intermediate 7, which directly condensed with weak nucleophiles such as pyrimidines or purines. The formation of gem-dichlorooxirane 7 and direct nucleobase condensation exclusively proceeded in protic polar solvents like MeOH. This method provides a general and modular route for the late-stage diversification of 1'-modified nucleosides.

Structure-Activity Relationship of Truncated 2,8-Disubstituted-Adenosine Derivatives as Dual A2A/A3 Adenosine Receptor Antagonists and Their Cancer Immunotherapeutic Activity

Based on hA2AAR structures, a hydrophobic C8-heteroaromatic ring in 5'-truncated adenosine analogues occupies the subpocket tightly, converting hA2AAR agonists into antagonists while maintaining affinity toward hA3AR. The final compounds of 2,8-disubstituted-N6-substituted 4'-thionucleosides, or 4'-oxo, were synthesized from d-mannose and d-erythrono-1,4-lactone, respectively, using a Pd-catalyst-controlled regioselective cross-coupling reaction. All tested compounds completely antagonized hA2AAR, including 5d with the highest affinity (Ki,A2A = 7.7 ± 0.5 nM). The hA2AAR-5d X-ray structure revealed that C8-heteroaromatic rings prevented receptor activation-associated conformational changes. However, the C8-substituted compounds still antagonized hA3AR. Structural SAR features and docking studies supported different binding modes at A2AAR and A3AR, elucidating pharmacophores for receptor activation and selectivity. Favorable pharmacokinetics were demonstrated, in which 5d displayed high oral absorption, moderate half-life, and bioavailability. Also, 5d significantly improved the antitumor effect of anti-PD-L1 in vivo. Overall, this study suggests that the novel dual A2AAR/A3AR nucleoside antagonists would be promising drug candidates for immune-oncology.

In Silico Discovery of 5'-Modified 7-Deoxy-7-ethynyl-4'-thioadenosine as a HASPIN Inhibitor and Its Synergistic Anticancer Effect with the PLK1 Inhibitor

Despite genetic perturbations resulting in embryo lethality for most mitotic kinases, loss of the histone H3 mitotic kinase HASPIN reveals no adverse effect in mice models, establishing HASPIN as a promising target for anticancer therapy. However, developing a HASPIN inhibitor from conventional pharmacophores poses a technical challenge as this atypical kinase shares slight similarities with eukaryotic protein kinases. Chemically modifying a cytotoxic 4'-thioadenosine analogue through high genotoxicity yielded several novel nongenotoxic kinase inhibitors. In silico apporoaches utilizing transcriptomic and chemical similarities with known compounds and KINOMEscan profiles unveiled the HASPIN inhibitor LJ4827. LJ4827's specificity and potency as a HASPIN inhibitor were verified through in vitro kinase assay and X-ray crystallography. HASPIN inhibition by LJ4827 reduced histone H3 phosphorylation and impeded Aurora B recruitment in cancer cell centromeres but not in noncancer cells. Through transcriptome analysis of lung cancer patients, PLK1 was determined as a druggable synergistic partner to complement HASPIN inhibition. Chemical or genetic PLK1 perturbation with LJ4827 effectuated pronounced lung cancer cytotoxicity in vitro and in vivo. Therefore, LJ4827 is a novel anticancer therapeutic for selectively impeding cancer mitosis through potent HASPIN inhibition, and simultaneous HASPIN and PLK1 interference is a promising therapeutic strategy for lung cancer.

Discovery of 2-aminoquinolone acid derivatives as potent inhibitors of SARS-CoV-2

The COVID-19 pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) continues to threaten human health and create socioeconomic problems worldwide. A library of 200,000 small molecules from the Korea Chemical Bank (KCB) were evaluated for their inhibitory activities against SARS-CoV-2 in a phenotypic-based screening assay to discover new therapeutics to combat COVID-19. A primary hit of this screen was the quinolone structure-containing compound 1. Based on the structure of compound 1 and enoxacin, which is a quinolone-based antibiotic previously reported to have weak activity against SARS-CoV-2, we designed and synthesized 2-aminoquinolone acid derivatives. Among them, compound 9b exhibited potent antiviral activity against SARS-CoV-2 (EC₅₀ = 1.5 µM) without causing toxicity, while having satisfactory in vitro PK profiles. This study shows that 2-aminoquinolone acid 9b provides a promising new template for developing anti-SARS-CoV-2 entry inhibitors.

Structure–Activity Relationships of Truncated 1′-Homologated Carbaadenosine Derivatives as New PPARγ/δ Ligands: A Study on Sugar Puckering Affecting Binding to PPARs

Peroxisome proliferator-activated receptors (PPARs) are associated with the regulation of metabolic homeostasis. Based on a previous report that 1'-homologated 4'-thionucleoside acts as a dual PPARγ/δ modulator, carbocyclic nucleosides 2-5 with various sugar conformations were synthesized to determine whether sugar puckering affects binding to PPARs. (S)-conformer 2 was synthesized using Charette asymmetric cyclopropanation, whereas (N)-conformer 3 was synthesized using stereoselective Simmons-Smith cyclopropanation. All synthesized nucleosides did not exhibit binding affinity to PPARα but exhibited significant binding affinities to PPARγ/δ. The binding affinity of final nucleosides to PPARγ did not differ significantly based on their conformation, but their affinity to PPARδ depended greatly on their conformation, correlated with adiponectin production. (N)-conformer 3h was discovered to be the most potent PPARδ antagonist with good adiponectin production, which exhibited the most effective activity in inhibiting the mRNA levels of LPS-induced IL-1β expression in RAW 264.7 macrophages, implicating its anti-inflammatory activity.

Synthesis of oligonucleotides containing 5'-homo-4'-selenouridine derivative and its increased resistance against nuclease

As technologies using RNA or DNA have been developed, various chemical modifications of nucleosides have been attempted to increase the stability of oligonucleotides. Since it is known that 2'-OMe-modification greatly contributes to increasing the stability of oligonucleotides, we added 2'-OMe to our previously developed 4'-selenonucleoside and 5'-homo-4'-selenonucleoside as the modified monomers for oligonucleotide: 2'-methoxy-4'-selenouridine (2'-OMe-4'-Se-U) and 5'-homo-2'-methoxy-4'-selenouridine (5'-homo-2'-OMe-4'-Se-U). We synthesized oligonucleotides containing the chemically modified 4'-selenouridine and evaluated their thermal stability and nuclease resistance. In conclusion, the nuclease stability of the oligonucleotide containing 5'-homo-2'-OMe-4'-selenouridine increased while its thermal stability decreased.

Synthesis of Enantiomerically Pure Pyrimidine Ribonucleosides Locked in the South Conformation

The conformation of the central five-membered ring of a nucleoside plays an important role in enzyme recognition. Bicyclo[3.1.0]hexane, also known as the methanocarba (MC), serves as a template that can mimic the locked forms of the two distinctive conformations, namely, the north and south conformations. While modified nucleosides locked in the north conformation have been actively investigated, the south counterpart remains largely unexplored because it is difficult to synthesize. Herein, we report a concise synthetic route that can provide the key amino sugar intermediate essential for the synthesis of (S)-MC ribonucleosides in a 100% stereoselective manner. Also, through the proposed synthetic approach, we report the first synthesis of enantiomerically pure (S)-MC cytidine 1. We believe our findings would greatly contribute to the field of nucleoside chemistry and provide opportunities for novel nucleoside discovery.

Anti-obesity effects of the dual-active adenosine A2A/A3 receptor-ligand LJ-4378

BACKGROUND AND OBJECTIVES

A_2A adenosine receptor (A_2AAR)-mediated signaling in adipose tissues has been investigated as a potential target for obesity-related metabolic diseases. LJ-4378 has been developed as a dual-acting ligand with A_2AAR agonist and A₃ adenosine receptor (A₃AR) antagonist activity. The current study aimed to investigate the anti-obesity effects of LJ-4378 and its underlying molecular mechanisms.

METHODS

Immortalized brown adipocytes were used for in vitro analysis. A high-fat diet (HFD)-induced obesity and cell death-inducing DFFA-like effector A reporter mouse models were used for in vivo experiments. The effects of LJ-4378 on lipolysis and mitochondrial metabolism were evaluated using immunoblotting, mitochondrial staining, and oxygen consumption rate analyses. The in vivo anti-obesity effects of LJ-4378 were evaluated using indirect calorimetry, body composition analyses, glucose tolerance tests, and histochemical analyses.

RESULTS

In vitro LJ-4378 treatment increased the levels of brown adipocyte markers and mitochondrial proteins, including uncoupling protein 1. The effects of LJ-4378 on lipolysis of adipocytes were more potent than those of the A_2AAR agonist or A₃AR antagonist. In vivo, LJ-4378 treatment increased energy expenditure by 17.0% (P value < 0.0001) compared to vehicle controls. LJ-4378 (1 mg/kg, i.p.) treatment for 10 days reduced body weight and fat content by 8.24% (P value < 0.0001) and 24.2% (P value = 0.0044), respectively, and improved glucose tolerance in the HFD-fed mice. LJ-4378 increased the expression levels of brown adipocyte markers and mitochondrial proteins in interscapular brown and inguinal white adipose tissue.

CONCLUSION

These findings support the in vivo anti-obesity effects of LJ-4378, and suggest a novel therapeutic approach to combat obesity and related metabolic diseases.

Molecular basis of specific viral RNA recognition and 5'-end capping by the Chikungunya virus nsP1

Many viruses encode RNA-modifying enzymes to edit the 5' end of viral RNA to mimic the cellular mRNA for effective protein translation, genome replication, and evasion of the host defense mechanisms. Alphavirus nsP1 synthesizes the 5' end Cap-0 structure of viral RNAs. However, the molecular basis of the capping process remains unclear. We determine high-resolution cryoelectron microscopy (cryo-EM) structures of Chikungunya virus nsP1 in complex with m7GTP/SAH, covalently attached m7GMP, and Cap-0 viral RNA. These structures reveal details of viral-RNA-capping reactions and uncover a sequence-specific virus RNA-recognition pattern that, in turn, regulates viral-RNA-capping efficiency to ensure optimal genome replication and subgenomic RNA transcription. This sequence-specific enzyme-RNA pairing is conserved across all alphaviruses.

Abstract 3949: Identification of a novel HASPIN inhibitor and the synthetic lethal partner by computational analysis

HASPIN, a mitotic kinase to phosphorylate Histone H3 at centromere, has been studied as a promising target for anti-cancer therapy. However, as HASPIN belongs to atypical kinase, lacking the Asp-Phe-Gly (DFG) motif, development from the chemical library of kinase inhibitors with conventional pharmacophore, would be technically challenging. In particular, one of adenosine analogues (LJ4827), a potent inhibitor of multi-kinases, showing clear anti-cancer activity in vitro and in vivo, was predicted as a HASPIN inhibitor by computation analysis of its transcriptome profile in cancer cells to drug-omic data set in the connectivity MAP (cMAP) as it shared similar transcriptome profile of 5-iodotubercidin (5ITU). The specificity and potency as HASPIN inhibitor of LJ4827 (IC50 = 0.45 nM) validated by in vitro kinase screening and consequent 3D structure modeling. As expected, treatment of LJ4827 in cancer cell lines efficiently delayed mitotic progression without double strand break (DSB) unlike 5ITU and significantly attenuated Aurora B localization at centromere. Along with clinical significance of HASPIN expression in lung cancer patients, mitotic gene signature closely associated to high expression of HASPIN, revealed the poor prognosis. Additional computational analysis of kinase perturbation data to predict the dependency of mitotic kinase in the absence of HASPIN activity, revealed the synthetic lethal effect of cotreatment of the chemical inhibitor of BUB1, PLK1 or AURKA with LJ4827. These data suggest that combined inhibition of HASPIN with the novel inhibitor and key mitotic kinases for centromere/kinetochore regulation would be effectivity therapeutic approach for cancer therapy.

Citation Format: Eun-Ji Kwon, Karishma Mashelkar, Hyuk Woo Lee, Yoon-Ze Shin, Lak Shin Jeong, Hyuk-Jin Cha. Identification of a novel HASPIN inhibitor and the synthetic lethal partner by computational analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3949.

Catalyst-controlled regioselective Sonogashira coupling of 9-substituted-6-chloro-2,8-diiodopurines

We have established a catalyst-dependent regioselective Sonogashira coupling methodology where both regioisomeric products can be obtained independently with remarkably high selectivity.

Subtle Chemical Changes Cross the Boundary between Agonist and Antagonist: New A3 Adenosine Receptor Homology Models and Structural Network Analysis Can Predict This Boundary

Distinguishing compounds' agonistic or antagonistic behavior would be of great utility for the rational discovery of selective modulators. We synthesized truncated nucleoside derivatives and discovered 6c (K_i = 2.40 nM) as a potent human A₃ adenosine receptor (hA₃AR) agonist, and subtle chemical modification induced a shift from antagonist to agonist. We elucidated this shift by developing new hA₃AR homology models that consider the pharmacological profiles of the ligands. Taken together with molecular dynamics (MD) simulation and three-dimensional (3D) structural network analysis of the receptor-ligand complex, the results indicated that the hydrogen bonding with Thr94^3.36 and His272^7.43 could make a stable interaction between the 3'-amino group with TM3 and TM7, and the corresponding induced-fit effects may play important roles in rendering the agonistic effect. Our results provide a more precise understanding of the compounds' actions at the atomic level and a rationale for the design of new drugs with specific pharmacological profiles.

Stereoselective Synthesis of (S)- and (N)-Cyclopropyl-Fused Carbocyclic Nucleosides Using Stereoselective Cyclopropanation

To determine which sugar conformation is favorable in binding to peroxisome proliferator-activated receptors, the conformationally locked south (S) and north (N) analogues were asymmetrically synthesized using a bicyclo[3.1.0]hexane template. The (S)-conformer was synthesized by employing "reagent-controlled" Charette asymmetric cyclopropanation in a 100% stereoselective manner, whereas the (N)-conformer was stereoselectively synthesized by using "substrate-controlled" hydroxyl-directed Simmons-Smith cyclopropanation as a key step.

Dual Actions of A2A and A3 Adenosine Receptor Ligand Prevents Obstruction-Induced Kidney Fibrosis in Mice

Kidney fibrosis is the final outcome of chronic kidney disease (CKD). Adenosine plays a significant role in protection against cellular damage by activating four subtypes of adenosine receptors (ARs), A₁AR, A_2AAR, A_2BAR, and A₃AR. A_2AAR agonists protect against inflammation, and A₃AR antagonists effectively inhibit the formation of fibrosis. Here, we showed for the first time that LJ-4459, a newly synthesized dual-acting ligand that is an A_2AAR agonist and an A₃AR antagonist, prevents the progression of tubulointerstitial fibrosis. Unilateral ureteral obstruction (UUO) surgery was performed on 6-week-old male C57BL/6 mice. LJ-4459 (1 and 10 mg/kg) was orally administered for 7 days, started at 1 day before UUO surgery. Pretreatment with LJ-4459 improved kidney morphology and prevented the progression of tubular injury as shown by decreases in urinary kidney injury molecular-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) excretion. Obstruction-induced tubulointerstitial fibrosis was attenuated by LJ-4459, as shown by a decrease in fibrotic protein expression in the kidney. LJ-4459 also inhibited inflammation and oxidative stress in the obstructed kidney, with reduced macrophage infiltration, reduced levels of pro-inflammatory cytokines, as well as reduced levels of reactive oxygen species (ROS). These data demonstrate that LJ-4459 has potential as a therapeutic agent against the progression of tubulointerstitial fibrosis.

Design and Synthesis of 2,6-Disubstituted-4'-Selenoadenosine-5'-N,N-Dimethyluronamide Derivatives as Human A3 Adenosine Receptor Antagonists

A new series of 4′-selenoadenosine-5′-N,N-dimethyluronamide derivatives as highly potent and selective human A₃ adenosine receptor (hA₃AR) antagonists, is described. The highly selective A₃AR agonists, 4′-selenoadenosine-5′-N-methyluronamides were successfully converted into selective antagonists by adding a second N-methyl group to the 5′-uronamide position. All the synthesized compounds showed medium to high binding affinity at the hA₃AR. Among the synthesized compounds, 2-H-N⁶-3-iodobenzylamine derivative 9f exhibited the highest binding affinity at hA₃AR. (K_i = 22.7 nM). The 2-H analogues generally showed better binding affinity than the 2-Cl analogues. The cAMP functional assay with 2-Cl-N⁶-3-iodobenzylamine derivative 9l demonstrated hA₃AR antagonist activity. A molecular modelling study suggests an important role of the hydrogen of 5′-uronamide as an essential hydrogen bonding donor for hA₃AR activation.

Discovery and Structure-Activity Relationships of Novel Template, Truncated 1'-Homologated Adenosine Derivatives as Pure Dual PPARγ/δ Modulators

Following our report that A₃ adenosine receptor (AR) antagonist 1 exhibited a polypharmacological profile as a dual modulator of peroxisome proliferator-activated receptor (PPAR)γ/δ, we discovered a new template, 1'-homologated adenosine analogues 4a-4t, as dual PPARγ/δ modulators without AR binding. Removal of binding affinity to A₃AR was achieved by 1'-homologation, and PPARγ/δ dual modulation was derived from the structural similarity between the target nucleosides and PPAR modulator drug, rosiglitazone. All the final nucleosides were devoid of AR-binding affinity and exhibited high binding affinities to PPARγ/δ but lacked PPARα binding. 2-Cl derivatives exhibited dual receptor-binding affinity to PPARγ/δ, which was absent for the corresponding 2-H derivatives. 2-Propynyl substitution prevented PPARδ-binding affinity but preserved PPARγ affinity, indicating that the C2 position defines a pharmacophore for selective PPARγ ligand designs. PPARγ/δ dual modulators functioning as both PPARγ partial agonists and PPARδ antagonists promoted adiponectin production, suggesting their therapeutic potential against hypoadiponectinemia-associated cancer and metabolic diseases.

A Novel cytarabine analog evokes synthetic lethality by targeting MK2 in p53-deficient cancer cells

Most nucleoside anticancer drugs show a primary resistance to p53-deficient or p53-mutated cancer cells and are limited in the clinic to the treatment of hematological malignancies. However, 2'-fluoro-4'-seleno-ara-C (F-Se-Ara-C), a new generation of cytarabine (Ara-C) analogs, exhibited potent antitumor activity against the p53-deficient prostate cancer cell line PC-3. The distinct activity of F-Se-Ara-C was achieved by targeting the synthetic lethal interaction between p53 and mitogen-activated protein kinase-activated protein kinase-2 (MK2). MK2 is a checkpoint effector for DNA damage responses to drive cell cycle arrest and DNA repair in p53-deficient cancer cells. Therefore, targeting MK2 may be an effective therapeutic strategy that induces apoptosis for cancers deficient in p53. F-Se-Ara-C effectively induced anti-prostate cancer activity in vitro and in vivo by inhibition of MK2 activation in p53-deficient prostate cancer cells. Moreover, combining F-Se-Ara-C with cabozantinib, an anticancer drug currently in clinical use, induced synergistic antitumor activity in p53-deficient prostate cancer cells. Taken together, these data show that F-Se-Ara-C may become great anticancer drug candidate with its unique mechanism of action for overcoming the apoptotic resistance of p53-deficient cells by targeting the synthetic lethal interaction.

UBC12-mediated SREBP-1 neddylation worsens metastatic tumor prognosis

Activation of sterol regulatory element-binding protein 1 (SREBP-1), a master lipogenic transcription factor, is associated with cancer metabolism and metabolic disorders. Neddylation, the process of adding NEDD8 to its substrate, contributes to diverse biological processes. Here, we identified SREBP-1 as a substrate for neddylation by UBC12 and explored its impact on tumor aggressiveness. In cell-based assays, SREBP-1 neddylation prolonged SREBP-1 stability with a decrease in ubiquitination. Consequently, NEDD8 overexpression facilitated proliferation, migration, and invasion of SK-Hep1 liver tumor cells. MLN4924 (an inhibitor of the NEDD8-activating enzyme-E1) treatment or UBC12 knockdown prevented SREBP-1 neddylation and tumor cell phenotype change. This effect was corroborated in an in vivo xenograft model. In human specimens, SREBP-1, UBC12, and NEDD8 were all upregulated in hepatocellular carcinoma (HCC) compared to nontumorous regions. Moreover, SREBP-1 levels positively correlated with UBC12. In GEO database analyses, SREBP-1 levels were greater in metastatic HCC samples accompanying UBC12 upregulation. In HCC analysis, tumoral SREBP-1 and UBC12 levels discriminated overall patient survival rates. Additionally, MLN4924 treatment destabilized SREBP-1 in MDA-MB-231 breast cancer cells and in the tumor cell xenograft. SREBP-1 and UBC12 were also highly expressed in human breast cancer tissues. Moreover, most breast cancers with lymph node metastasis displayed predominant SREBP-1 and UBC12 expressions, which compromised overall patient survival rates. In summary, SREBP-1 is neddylated by UBC12, which may contribute to HCC and breast cancer aggressiveness through SREBP-1 stabilization, and these events can be intervented by MLN4924 therapy. Our findings may also provide potential reliable prognostic markers for tumor metastasis.

LJ-2698, an Adenosine A3 Receptor Antagonist, Alleviates Elastase-Induced Pulmonary Emphysema in Mice

Emphysema, a major component of chronic obstructive pulmonary disease (COPD), is a leading cause of human death worldwide. The progressive deterioration of lung function that occurs in the disease is caused by chronic inflammation of the airway and destruction of the lung parenchyma. Despite the main impact of inflammation on the pathogenesis of emphysema, current therapeutic regimens mainly offer symptomatic relief and preservation of lung function with little therapeutic impact. In the present study, we aimed to discover novel therapeutics that suppress the pathogenesis of emphysema. Here, we show that LJ-2698, a novel and highly selective antagonist of the adenosine A₃ receptor, a G protein-coupled receptor involved in various inflammatory diseases, significantly reversed the elastase-induced destructive changes in murine lungs. We found that LJ-2698 significantly prevented elastase-induced airspace enlargement, resulting in restoration of pulmonary function without causing any obvious changes in body weight in mice. LJ-2698 was found to inhibit matrix metalloproteinase activity and pulmonary cell apoptosis in the murine lung. LJ-2698 treatment induced increases in anti-inflammatory cytokines in macrophages at doses that displayed no significant cytotoxicity in normal cell lines derived from various organs. Treatment with LJ-2698 significantly increased the number of anti-inflammatory M2 macrophages in the lungs. These results implicate the adenosine A₃ receptor in the pathogenesis of emphysema. Our findings also demonstrate the potential of LJ-2698 as a novel therapeutic/preventive agent in suppressing disease development with limited toxicity.

Antiproliferative and Antimigration Activities of Fluoro-Neplanocin A via Inhibition of Histone H3 Methylation in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is among the most aggressive and potentially metastatic malignancies. Most affected patients have poor clinical outcomes due to the lack of specific molecular targets on tumor cells. The upregulated expression of disruptor of telomeric silencing 1-like (DOT1L), a histone methyltransferase specific for the histone H3 lysine 79 residue (H3K79), is strongly correlated with TNBC cell aggressiveness. Therefore, DOT1L is considered a potential molecular target in TNBC. Fluoro-neplanocin A (F-NepA), an inhibitor of S-adenosylhomocysteine hydrolase, exhibited potent antiproliferative activity against various types of cancer cells, including breast cancers. However, the molecular mechanism underlying the anticancer activity of F-NepA in TNBC cells remains to be elucidated. We determined that F-NepA exhibited a higher growth-inhibitory activity against TNBC cells relative to non-TNBC breast cancer and normal breast epithelial cells. Moreover, F-NepA effectively downregulated the level of H3K79me2 in MDA-MB-231 TNBC cells by inhibiting DOT1L activity. F-NepA also significantly inhibited TNBC cell migration and invasion. These activities of F-NepA might be associated with the upregulation of E-cadherin and downregulation of N-cadherin and Vimentin in TNBC cells. Taken together, these data highlight F-NepA as a strong potential candidate for the targeted treatment of high-DOT1L-expressing TNBC.

Identification of 6'-β-fluoro-homoaristeromycin as a potent inhibitor of chikungunya virus replication

We have reported on aristeromycin (1) and 6′-fluorinated-aristeromycin analogues (2), which are active against RNA viruses such as Middle East respiratory syndrome coronavirus (MERS-CoV), severe acute respiratory syndrome coronavirus (SARS-CoV), Zika virus (ZIKV), and Chikungunya virus (CHIKV). However, these exhibit substantial cytotoxicity. As this cytotoxicity may be attributed to 5′-phosphorylation, we designed and synthesized one-carbon homologated 6′-fluorinated-aristeromycin analogues. This modification prevents 5′-phosphorlyation by cellular kinases, whereas the inhibitory activity towards S-adenosyl-l-homocysteine (SAH) hydrolase will be retained. The enantiomerically pure 6′-fluorinated-5′-homoaristeromycin analogues 3a-e were synthesized via the electrophilic fluorination of the silyl enol ether with Selectfluor, using a base-build up approach as the key steps. All synthesized compounds exhibited potent inhibitory activity towards SAH hydrolase, among which 6′-β-fluoroadenosine analogue 3a was the most potent (IC₅₀ = 0.36 μM). Among the compounds tested, 6′-β-fluoro-homoaristeromycin 3a showed potent antiviral activity (EC₅₀ = 0.12 μM) against the CHIKV, without noticeable cytotoxicity up to 250 μM. Only 3a displayed anti-CHIKV activity, whereas both3a and 3b inhibited SAH hydrolase with similar IC₅₀ values (0.36 and 0.37 μM, respectively), which suggested that 3a’s antiviral activity did not merely depend on the inhibition of SAH hydrolase. This is further supported by the fact that the antiviral effect was specific for CHIKV and some other alphaviruses and none of the homologated analogues inhibited other RNA viruses, such as SARS-CoV, MERS-CoV, and ZIKV. The potent inhibition and high selectivity index make 6′-β-fluoro-homoaristeromycin (3a) a promising new template for the development of antivirals against CHIKV, a serious re-emerging pathogen that has infected millions of people over the past 15 years.

Asymmetric Synthesis of 2'-C-Methyl-4'-selenonucleosides as Anti-Hepatitis C Virus Agents

In search of a new template for anti-hepatitis C virus (HCV) agents, we designed and synthesized the 2'-C-methyl-4'-selenopyrimidine and -purine nucleosides and their phosphoramidate prodrugs to replace a furanose oxygen of anti-HCV nucleos(t)ides with a selenium atom on the basis that selenium is a chemical isostere of oxygen. These nucleosides are expected to show different physicochemical properties such as better lipophilicity which might enhance the penetration across cell membranes and the conformational constraint induced by a bulky selenium atom in the sugar ring. The 2'-C-methyl-4'-selenopyrimidine and -purine nucleosides 8 and 9 were synthesized from 2-C-methyl-d-ribono-γ-lactone (14) via construction of 2-C-methyl-d-selenosugar 18 through C-4 epimerization and S_N2 cyclization with Se^2- as key steps. The key 4'-selenosugar was converted to the 2'-C-methyl-4'-selenopyrimidine and -purine nucleosides using Pummerer-type rearrangement and Vorbrüggen glycosylation, respectively. In addition, the ProTide strategy has been applied to synthesize the adenine and uracil phosphoramidate derivatives 10a and 10b to overcome the limitations associated with parent nucleosides such as inefficient conversion to their corresponding 5'-monophosphate form and poor cellular uptake. The regio- and stereochemistry of 4'-selenonucleosides were confirmed by 2D NOESY NMR spectroscopy and X-ray crystallography. None of the final pyrimidine and purine nucleosides and their prodrugs exhibited significant anti-HCV activity up to 100 μM.

Abstract 75: Anti-tumor activity of a novel selenonucleoside via targeting Skp2 degradation in paclitaxel-resistant prostate cancer

Prostate cancer (PC) is the most common disease in men over age 50, and its prevalence rate has been gradually increasing since 1980. Taxane-derived anticancer agents are the primary agents used to treat metastatic prostate cancer patients; however, the side effects and acquired drug resistance limit the success of these therapies. Because there is no specific treatment for paclitaxel-resistant prostate cancer, it is necessary to develop new targets and therapeutic strategies to overcome the acquired resistance. In this study, the antitumor activity of a novel selenonucleoside (4′-selenofuranosyl-2,6-dichloropurine, LJ-2618), a third-generation nucleoside, and its plausible mechanisms of action in paclitaxel-resistant prostate cancer (PC-3-Pa) cells were investigated. The established PC-3-Pa cells exhibited over 100-fold resistance against paclitaxel compared to the paclitaxel-sensitive PC-3 cells. LJ-2618, however, effectively inhibited the proliferation of both cell lines with similar IC50values in vitro. In PC-3-Pa cells, the activated PI3K/Akt signaling pathway was suppressed by LJ-2618 treatment. In addition, Skp2 was found to be over-expressed in paclitaxel-resistant cells, and the transfection of Skp2 siRNA recovered the sensitivity of paclitaxel in PC-3-Pa cells. Furthermore, LJ-2618 significantly down-regulated Skp2 expression in PC-3-Pa cells by promoting degradation and inducing destabilization of Skp2, which triggers G2/M cell cycle arrest. In a xenograft mouse model implanted with PC-3-Pa cells, LJ-2618 (3 or 10 mg/kg) effectively inhibited tumor growth with the enhancement of Skp2 degradation and induction of p27 expression in tumor tissues. These findings suggest that LJ-2618 may have a potential for overcoming paclitaxel resistance via promoting Skp2 degradation and stabilizing p27 expression in PC-3-Pa cells. Therefore, the novel selenonucleoside LJ-2618 may lead to the development of a new treatment strategy for patients with paclitaxel-resistant, castration-resistant prostate cancer. This study was supported by a National Research Foundation of Korea (NRF) Grant funded by the Korean Government (NRF-2016M3A9B6903499).

Citation Format: Woong Sub Byun, Minkyung Jin, Jinha Yu, Won Kyung Kim, Lak Shin Jeong, Sang Kook Lee. Anti-tumor activity of a novel selenonucleoside via targeting Skp2 degradation in paclitaxel-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 75.

Promotion of tumor-associated macrophages infiltration by elevated neddylation pathway via NF-κB-CCL2 signaling in lung cancer

Tumor-associated macrophages (TAMs) are the most abundant cancer stromal cells and play an essential role in tumor immunosuppression, providing a suitable microenvironment for cancer development and progression. However, mechanisms of regulating TAMs infiltration in tumor sites are not fully understood. Here, we show that inactivation of neddylation pathway significantly inhibits infiltration of TAMs, leading to the suppression of lung cancer metastasis. RNA-sequencing analysis revealed that neddylation inactivation suppresses the transactivation of chemotactic cytokine ligand 2 (CCL2). Mechanistically, neddylation inactivation inhibits the activity of Cullin-RING ligases (CRLs) and induces the accumulation of its substrate IκBα to block NF-κB transcriptional activity and CCL2 transactivation. As a result, neddylation inactivation exhibits lower chemotaxis of monocytes, thereby decreasing TAMs infiltration, which can be alleviated by CCL2 addition. Moreover, the expression level of NEDD8 is positively correlated with high CCL2 expression in lung adenocarcinoma, conferring a worse overall patient survival. Together, neddylation pathway promotes CCL2 transactivation and TAMs infiltration in lung cancer to provide a tumor-promoting microenvironment, which validates neddylation pathway as a promising target for anti-TAMs therapeutic strategies.

Design, Synthesis, and Anti-RNA Virus Activity of 6'-Fluorinated-Aristeromycin Analogues

The 6'-fluorinated aristeromycins were designed as dual-target antiviral compounds aimed at inhibiting both the viral RNA-dependent RNA polymerase (RdRp) and the host cell S-adenosyl-l-homocysteine (SAH) hydrolase, which would indirectly target capping of viral RNA. The introduction of a fluorine at the 6'-position enhanced the inhibition of SAH hydrolase and the activity against RNA viruses. The adenosine and N⁶-methyladenosine analogues 2a-e showed potent inhibition against SAH hydrolase, while only the adenosine derivatives 2a-c exhibited potent antiviral activity against all tested RNA viruses such as Middle East respiratory syndrome-coronavirus (MERS-CoV), severe acute respiratory syndrome-coronavirus, chikungunya virus, and/or Zika virus. 6',6'-Difluoroaristeromycin (2c) showed the strongest antiviral effect for MERS-CoV, with a ∼2.5 log reduction in infectious progeny titer in viral load reduction assay. The phosphoramidate prodrug 3a also demonstrated potent broad-spectrum antiviral activity, possibly by inhibiting the viral RdRp. This study shows that 6'-fluorinated aristeromycins can serve as starting points for the development of broad-spectrum antiviral agents that target RNA viruses.

Neddylation Inactivation Facilitates FOXO3a Nuclear Export to Suppress Estrogen Receptor Transcription and Improve Fulvestrant Sensitivity

PURPOSE

How the neddylation pathway functions in breast tumor and regulation of estrogen receptor (ER) expression is rarely reported. The purpose of this study was to identify the role of neddylation in breast cancer and ER expression, and further explore the underlying mechanisms.

EXPERIMENTAL DESIGN

Expression patterns of nedd8-activating enzyme (NAE) and nedd8, two key proteins in the neddylation pathway, were examined in human breast specimens. ER-α expression was investigated using animal 18F-FES-PET/CT and immunoblotting upon NAE inhibitor MLN4924 treatment. Chromatin immunoprecipitation assay, luciferase reporter promoter assay, and the CRISPR-Cas9 system were used to elucidate the mechanism of ER-α regulation by MLN4924. The ER-positive breast cancer mouse model was used to determine the synergetic effect of MLN4924 and fulvestrant on tumor growth. All statistical tests were two-sided.

RESULTS

Both NAE1 and nedd8 expressions were higher in the ER-positive subgroup. Higher expressions of NAE1 and nedd8 indicated poorer prognosis. Importantly, ER-α expression was significantly downregulated upon MLN4924 treatment in vitro and in vivo. Mechanistically, MLN4924 treatment delayed serum and glucocorticoid-induced protein kinase (SGK) degradation and induced Forkhead box O3a (FOXO3a) nuclear export as well as decreased binding to the ESR1 promoter. Importantly, MLN4924 single or synergized with fulvestrant significantly suppressed the growth of ER-positive breast cancer in vitro and in vivo.

CONCLUSIONS

Our proof-of-principle study determines the activation of neddylation in breast tumor tissues for the first time and reveals a new ER-α regulatory mechanism, as well as further explores an effective approach to improve fulvestrant sensitivity through a neddylation inactivation combination.

LJ-1888, a selective antagonist for the A3 adenosine receptor, ameliorates the development of atherosclerosis and hypercholesterolemia in apolipoprotein E knock-out mice

Cardiovascular diseases arising from atherosclerosis are the leading causes of mortality and morbidity worldwide. Lipid-lowering agents have been developed in order to treat hypercholesterolemia, a major risk factor for atherosclerosis. However, the prevalence of cardiovascular diseases is increasing, indicating a need to identify novel therapeutic targets and develop new treatment agents. Adenosine receptors (ARs) are emerging as therapeutic targets in asthma, rheumatoid arthritis, cancer, ischemia, and inflammatory diseases. This study assessed whether LJ-1888, a selective antagonist for A₃ AR, can inhibit the development of atherosclerosis in apolipoprotein E knock-out (ApoE^−/−) mice who are fed a western diet. Plaque formation was significantly lower in ApoE^−/− mice administered LJ-1888 than in mice not administered LJ-1888, without any associated liver damage. LJ-1888 treatment of ApoE^−/− mice prevented western diet-induced hypercholesterolemia by markedly reducing low-density lipoprotein cholesterol levels and significantly increasing high-density lipoprotein cholesterol concentrations. Reduced hypercholesterolemia in ApoE^−/− mice administered LJ-1888 was associated with the enhanced expression of genes involved in bile acid biosynthesis. These findings indicate that LJ-1888, a selective antagonist for A₃ AR, may be a novel candidate for the treatment of atherosclerosis and hypercholesterolemia.

An efficient synthesis of fluoro-neplanocin A analogs using electrophilic fluorination and palladium-catalyzed dehydrosilylation

An alternative and efficient approach to neplanocin A analogs 1b and 1d has been developed using electrophilic fluorination and Pd-catalyzed dehydrosilylation.

An alternative and efficient synthesis of MLN4924, a selective NEDD8 inhibitor

A highly efficient synthesis of MLN4924viaregioselective removal of α-alkoxy group and stereoselective reduction of ketone is described.

Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase 1A (DYRK1A) Inhibitors as Potential Therapeutics

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a member of an evolutionarily conserved family of protein kinases that belongs to the CMGC group of kinases. DYRK1A, encoded by a gene located in the human chromosome 21q22.2 region, has attracted attention due to its association with both neuropathological phenotypes and cancer susceptibility in patients with Down syndrome (DS). Inhibition of DYRK1A attenuates cognitive dysfunctions in animal models for both DS and Alzheimer's disease (AD). Furthermore, DYRK1A has been studied as a potential cancer therapeutic target because of its role in the regulation of cell cycle progression by affecting both tumor suppressors and oncogenes. Consequently, selective synthetic inhibitors have been developed to determine the role of DYRK1A in various human diseases. Our perspective includes a comprehensive review of potent and selective DYRK1A inhibitors and their forthcoming therapeutic applications.

The Nedd8-activating enzyme inhibitor MLN4924 (TAK-924/Pevonedistat) induces apoptosis via c-Myc-Noxa axis in head and neck squamous cell carcinoma

Objectives

The present study aimed to reveal expression status of the neddylation enzymes in HNSCC and to elucidate the anticancer efficacy and the underlying mechanisms of inhibiting neddylation pathway.

Materials and methods

The expression levels of neddylation enzymes were estimated by Western blotting in human HNSCC specimens and bioinformatics analysis of the cancer genome atlas (TCGA) database. Cell apoptosis was evaluated by Annexin V fluorescein isothiocyanate/propidium iodide (Annexin V‐FITC/PI) stain and fluorescence‐activated cell sorting (FACS). Small interfering RNA (siRNA) and the CRISPR‐Cas9 system were used to elucidate the underlying molecular mechanism of MLN4924‐induced HNSCC apoptosis.

Results

Expression levels of NAE1 and UBC12 were prominently higher in HNSCC tissues than that in normal tissues. Inactivation of the neddylation pathway significantly inhibited malignant phenotypes of HNSCC cells. Mechanistic studies revealed that MLN4924 induced the accumulation of CRL ligase substrate c‐Myc that transcriptionally activated pro‐apoptotic protein Noxa, which triggered apoptosis in HNSCC.

Conclusions

These findings determined the over‐expression levels of neddylation enzymes in HNSCC and revealed novel mechanisms underlying neddylation inhibition induced growth suppression in HNSCC cells, which provided preclinical evidence for further clinical evaluation of neddylation inhibitors (eg, MLN4924) for the treatment of HNSCC.

A novel selenonucleoside suppresses tumor growth by targeting Skp2 degradation in paclitaxel-resistant prostate cancer

Prostate cancer (PC) is the most common disease in men over age 50, and its prevalence rate has been gradually increasing since 1980. Taxane-derived anticancer agents are the primary agents used to treat metastatic prostate cancer patients; however, the side effects and acquired drug resistance limit the success of these therapies. Because there is no specific treatment for paclitaxel-resistant prostate cancer, it is necessary to develop new targets and therapeutic strategies to overcome the acquired resistance. In this study, the antitumor activity of a novel selenonucleoside (4'-selenofuranosyl-2,6-dichloropurine, LJ-2618), a third-generation nucleoside, and its plausible mechanisms of action in paclitaxel-resistant prostate cancer (PC-3-Pa) cells were investigated. The established PC-3-Pa cells exhibited over 100-fold resistance against paclitaxel compared to the paclitaxel-sensitive PC-3 cells. LJ-2618, however, effectively inhibited the proliferation of both cell lines with similar IC₅₀ values in vitro. In PC-3-Pa cells, the activated PI3K/Akt signaling pathway was suppressed by LJ-2618 treatment. In addition, Skp2 was found to be over-expressed in paclitaxel-resistant cells, and the transfection of Skp2 siRNA recovered the sensitivity of paclitaxel in PC-3-Pa cells. Furthermore, LJ-2618 significantly down-regulated Skp2 expression in PC-3-Pa cells by promoting degradation and inducing destabilization of Skp2, which triggers G₂/M cell cycle arrest. In a xenograft mouse model implanted with PC-3-Pa cells, LJ-2618 (3 or 10 mg/kg) effectively inhibited tumor growth with the enhancement of Skp2 degradation and induction of p27 expression in tumor tissues. These findings suggest that LJ-2618 may have potential for overcoming paclitaxel resistance via promoting Skp2 degradation and stabilizing p27 expression in PC-3-Pa cells. Therefore, the novel selenonucleoside LJ-2618 may lead to the development of a new treatment strategy for patients with paclitaxel-resistant, castration-resistant prostate cancer.

Correlation study between A3 adenosine receptor binding affinity and anti-renal interstitial fibrosis activity of truncated adenosine derivatives

Truncated 4'-thionucleosides 1-4 and 4'-oxonucleosides 5-8 as potent and selective A₃AR antagonists were synthesized from D-mannose and D-erythronic acid γ-lactone, respectively. These nucleosides were evaluated for their anti-fibrotic renoprotective activity in TGF-β1-treated murine proximal tubular (mProx) cells. Their antagonistic activities for A₃AR were proportional to their inhibitory activities against TGF-β1-induced collagen I upregulation in mProx cells. This result suggests that the binding affinity of A₃AR antagonists is closely correlated with their anti-fibrotic activity. Thus, A₃AR antagonists might be novel therapeutic candidates for treating chronic kidney disease.

Asymmetric Synthesis of (-)-6'-β-Fluoro-aristeromycin via Stereoselective Electrophilic Fluorination

(-)-6'-β-Fluoro-aristeromycin (2), a potent inhibitor of S-adenosylhomocysteine (AdoHcy) hydrolase, has been synthesized via stereoselective electrophilic fluorination followed by a purine base build-up approach. Interestingly, purine base condensation using a cyclic sulfate resulted in a synthesis of (+)-5'-β-fluoro-isoaristeromycin (2a). Computational analysis indicates that the fluorine atom controlled the regioselectivity of the purine base substitution.

Design, synthesis and anticancer activity of fluorocyclopentenyl-purines and - pyrimidines

Based on the potent anticancer activity of 6'-fluorocyclopentenyl-cytosine 2b in phase IIa clinical trials for the treatment of gemcitabine-resistant pancreatic cancer, we carried out a systematic structure-activity relationship study of 6'-fluorocyclopentenyl-pyrimidines 3a-i and -purines 3j-o to discover novel anticancer agents. We also synthesized the phosphoramidate prodrug 3p of adenine derivative 1b to determine if the anticancer activity depended on the inhibition of DNA and/or RNA polymerase in cancer cells and/or on the inhibition of S-adenosylhomocysteine (SAH) hydrolase. All of the synthesized pyrimidine nucleosides exhibited much less potent anticancer activity in vitro than the cytosine derivative 2b, acting as RNA and/or DNA polymerase inhibitor, indicating that they could not be efficiently converted to their triphosphates for anticancer activity. Among all the synthesized purine nucleosides, adenine derivative 1b and N⁶-methyladenine derivative 3k showed potent anticancer activity, showing equipotent inhibitory activity as the positive control, neplanocin A (1a) or Ara-C. However, the phosphoramidate prodrug 3p showed less anticancer activity than 1b, indicating that it did not act as a RNA and/or DNA polymerase inhibitor like 2b. This result also demonstrates that the anticancer activity of 1b largely depends on the inhibition of histone methyltransferase, resulting from strong inhibition of SAH hydrolase. The deamination of the N⁶-amino group, the addition of the bulky alkyl group at the N⁶-amino group, or the introduction of the amino group at the C2 position almost abolished the anticancer activity.

Orally active, species-independent novel A3 adenosine receptor antagonist protects against kidney injury in db/db mice

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease, and the current pharmacological treatment for DKD is limited to renin-angiotensin system (RAS) inhibitors. Adenosine is detectable in the kidney and is significantly elevated in response to cellular damage. While all 4 known subtypes of adenosine receptors, namely, A₁AR, A_2aAR, A_2bAR, and A₃AR, are expressed in the kidney, our previous study has demonstrated that a novel, orally active, species-independent, and selective A₃AR antagonist, LJ-1888, ameliorates unilateral ureteral obstruction-induced tubulointerstitial fibrosis. The present study examined the protective effects of LJ-2698, which has higher affinity and selectivity for A₃AR than LJ-1888, on DKD. In experiment I, dose-dependent effects of LJ-2698 were examined by orally administering 1.5, 5, or 10 mg/kg for 12 weeks to 8-week-old db/db mice. In experiment II, the effects of LJ-2698 (10 mg/kg) were compared to those of losartan (1.5 mg/kg), which is a standard treatment for patients with DKD. LJ-2698 effectively prevented kidney injuries such as albuminuria, glomerular hypertrophy, tubular injury, podocyte injury, fibrosis, inflammation, and oxidative stress in diabetic mice as much as losartan. In addition, inhibition of lipid accumulation along with increases in PGC1α, a master regulator of mitochondrial biogenesis, were demonstrated in diabetic mice treated with either LJ-2698 or losartan. These results suggest that LJ-2698, a selective A₃AR antagonist, may become a novel therapeutic agent against DKD.

A therapeutic treatment targeting a protein involved in the progression of diabetic kidney disease (DKD) shows promise in mouse trials. Between 30 and 40 per cent of diabetic patients suffer from DKD, a common cause to fatal end-stage kidney disease. Protein receptors, commonly expressed on cell surfaces throughout the body, play both positive and negative roles in diseases. The A₃ adenosine receptor (A₃AR) is highly expressed in diabetic kidney tissue, and is linked to disease progression. Hunjoo Ha at Ewha Womans University in Seoul, Republic of Korea, and co-workers demonstrated the positive effect of a novel drug in targeting A₃AR in mice with DKD. A 12-week treatment of the drug prevented kidney injury, lowered oxidative stress and inflammation, and improved kidney function. It may prove an invaluable drug, particularly in combination with an existing DKD drug.

Polypharmacology of N6-(3-Iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA) and Related A3 Adenosine Receptor Ligands: Peroxisome Proliferator Activated Receptor (PPAR) γ Partial Agonist and PPARδ Antagonist Activity Suggests Their Antidiabetic Potential

A₃ adenosine receptor (AR) ligands including A₃ AR agonist, N⁶-(3-iodobenzyl)adenosine-5'-N-methyluronamide (1a, IB-MECA) were examined for adiponectin production in human bone marrow mesenchymal stem cells (hBM-MSCs). In this model, 1a significantly increased adiponectin production, which is associated with improved insulin sensitivity. However, A₃ AR antagonists also promoted adiponectin production in hBM-MSCs, indicating that the A₃ AR pathway may not be directly involved in the adiponectin promoting activity. In a target deconvolution study, their adiponectin-promoting activity was significantly correlated to their binding activity to both peroxisome proliferator activated receptor (PPAR) γ and PPARδ. They functioned as both PPARγ partial agonists and PPARδ antagonists. In the diabetic mouse model, 1a and its structural analogues A₃ AR antagonists significantly decreased the serum levels of glucose and triglyceride, supporting their antidiabetic potential. These findings indicate that the polypharmacophore of these compounds may provide therapeutic insight into their multipotent efficacy against various human diseases.

Targeting neddylation pathway with MLN4924 (Pevonedistat) induces NOXA-dependent apoptosis in renal cell carcinoma

Inhibition of protein neddylation pathway has emerged an attractive anticancer strategy in preclinical studies by using Nedd8-activating enzyme (NAE) inhibitor MLN4924 (Pevonedistat). Previous studies have reported the antitumor activity of MLN4924 mediated by its efficacy on apoptosis, autophagy and senescence. However, whether MLN4924 has any effect on renal carcinoma cells (RCC) remains unexplored. Here we reported that MLN4924 specifically inhibited protein neddylation pathway, leading to statistically significantly suppress the proliferation, survival and migration of RCC cells by inducing G₂ cell-cycle arrest, followed by apoptosis in a MLN4924 dose-dependent manner. Further mechanistic study revealed that MLN4924-induced apoptosis was mediated by substantial up-regulation of pro-apoptotic NOXA. These findings highlighted the anticancer effects of the neddylation inhibitors (e.g. MLN4924) for the treatment of RCC.

Stereoselective Synthesis of 4'-Selenonucleosides via the Seleno-Michael Reaction

5'-Homo-4'-selenonucleosides, a class of next-generation nucleosides, are synthesized from D-ribose via a 4-selenosugar intermediate. The key step in synthesizing this intermediate is a seleno-Michael reaction. 5'-Homo-4'-selenouridine and -adenosine are prepared using Pummerer-type and Vorbrüggen condensation, respectively. © 2017 by John Wiley & Sons, Inc.

NEDD8-activating enzyme inhibitor, MLN4924 (Pevonedistat) induces NOXA-dependent apoptosis through up-regulation of ATF-4

It has been reported that MLN4924 can inhibit cell growth and metastasis in various kinds of cancer. We have reported that MLN4924 is able to inhibit angiogenesis through the induction of cell apoptosis both in vitro and in vivo models. Moreover, Neddylation inhibition using MLN4924 triggered the accumulation of pro-apoptotic protein NOXA in Human umbilical vein endothelial cells (HUVECs). However, the mechanism of MLN4924-induced NOXA up-regulation has not been addressed in HUVECs yet. In this study, we investigated how MLN4924 induced NOXA expression and cellular apoptosis in HUVECs treated with MLN4924 at indicated concentrations. MLN4924-induced apoptosis was evaluated by Annexin V-FITC/PI analysis and expression of genes associated with apoptosis was assessed by Quantitative RT-PCR and western blotting. As a result, MLN4924 triggered NOXA-dependent apoptosis in a dose-dependent manner in HUVECs. Mechanistically, inactivation of Neddylation pathway caused up-regulation of activating transcription factor 4 (ATF-4), a substrate of Cullin-Ring E3 ubiquitin ligases (CRL). NOXA was subsequently transactivated by ATF-4 and further induced apoptosis. More importantly, knockdown of ATF-4 by siRNA significantly decreased NOXA expression and apoptotic induction in HUVECs. In summary, our study reveals a new mechanism underlying MLN4924-induced NOXA accumulation in HUVECs, which may help extend further study of MLN4924 for angiogenesis inhibition treatment.

N6-Substituted 5'-N-Methylcarbamoyl-4'-selenoadenosines as Potent and Selective A3 Adenosine Receptor Agonists with Unusual Sugar Puckering and Nucleobase Orientation

Potent and selective A₃ adenosine receptor (AR) agonists were identified by the replacement of 4'-oxo- or 4'-thionucleosides with bioisosteric selenium. Unlike previous agonists, 4'-seleno analogues preferred a glycosidic syn conformation and South sugar puckering, as shown in the X-ray crystal structure of 5'-N-methylcarbamoyl derivative 3p. Among the compounds tested, N⁶-3-iodobenzyl analogue 3d was found to be the most potent A₃AR full agonist (K_i = 0.57 nM), which was ≥800- and 1900-fold selective for A₁AR and A_2AAR, respectively. In the N⁶-cycloalkyl series, 2-Cl analogues generally exhibited better hA₃AR affinity than 2-H analogues, whereas 2-H > 2-Cl in the N⁶-3-halobenzyl series. N⁷ isomers 3t and 3u were much weaker in binding than corresponding N⁹ isomers, but compound 3t lacked A₃AR activation, appearing to be a weak antagonist. 2-Cl-N⁶-3-iodobenzyl analogue 3p inhibited chemoattractant-induced migration of microglia/monocytes without inducing cell death at ≤50 μM. This suggests the potential for the development of 4'-selenonucleoside A₃AR agonists as novel antistroke agents.

2,3,4-Trihydroxybenzyl-hydrazide analogues as novel potent coxsackievirus B3 3C protease inhibitors

Human coxsackievirus B3 (CVB3) 3C protease plays an essential role in the viral replication of CVB3, which is a non-enveloped and positive single-stranded RNA virus belonging to Picornaviridae family, causing acute viral myocarditis mainly in children. During optimization based on SAR studies of benserazide (3), which was reported as a novel anti-CVB3 3C(pro) agent from a screening of compound libraries, the 2,3,4-trihydroxybenzyl moiety of 3 was identified as a key pharmacophore for inhibitory activity against CVB3 3C(pro). Further optimization was performed by the introduction of various aryl-alkyl substituted hydrazide moieties instead of the serine moiety of 3. Among the optimized compounds, 11Q, a 4-hydroxyphenylpentanehydrazide derivative, showed the most potent inhibitory activity (IC50 = 0.07 μM). Enzyme kinetics studies indicated that 11Q exhibited a mixed inhibitory mechanism of action. The antiviral activity against CVB3 was confirmed using the further derived analogue (14b) with more cell permeable valeryl ester group at the 2,3,4-trihydroxy moiety.

Synthesis, structural characterization and biological evaluation of 4'-C-methyl- and phenyl-dioxolane pyrimidine and purine nucleosides

Nucleoside analogues play an important role in antiviral, antibacterial and antineoplastic chemotherapy. Herein we report the synthesis, structural characterization and biological activity of some 4'-C -methyl- and -phenyl dioxolane-based nucleosides. In particular, α and β anomers of all natural nucleosides were obtained and characterized by NMR, HR-MS and X-ray crystallography. The compounds were tested for antimicrobial activity against some representative human pathogenic fungi, bacteria and viruses. Antitumor activity was evaluated in a large variety of human cancer cell-lines. Although most of the compounds showed non-significant activity, 23α weakly inhibited HIV-1 multiplication. Moreover, 22α and 32α demonstrated a residual antineoplastic activity, interestingly linked to the unnatural α configuration. These results may provide structural insights for the design of active antiviral and antitumor agents.

Renoprotective Effects of a Highly Selective A3 Adenosine Receptor Antagonist in a Mouse Model of Adriamycin-induced Nephropathy

The concentration of adenosine in the normal kidney increases markedly during renal hypoxia, ischemia, and inflammation. A recent study reported that an A3 adenosine receptor (A3AR) antagonist attenuated the progression of renal fibrosis. The adriamycin (ADX)-induced nephropathy model induces podocyte injury, which results in severe proteinuria and progressive glomerulosclerosis. In this study, we investigated the preventive effect of a highly selective A3AR antagonist (LJ1888) in ADX-induced nephropathy. Three groups of six-week-old Balb/c mice were treated with ADX (11 mg/kg) for four weeks and LJ1888 (10 mg/kg) for two weeks as following: 1) control; 2) ADX; and 3) ADX + LJ1888. ADX treatment decreased body weight without a change in water and food intake, but this was ameliorated by LJ1888 treatment. Interestingly, LJ1888 lowered plasma creatinine level, proteinuria, and albuminuria, which had increased during ADX treatment. Furthermore, LJ1888 inhibited urinary nephrin excretion as a podocyte injury marker, and urine 8-isoprostane and kidney lipid peroxide concentration, which are markers of oxidative stress, increased after injection of ADX. ADX also induced the activation of proinflammatory and profibrotic molecules such as TGF-β1, MCP-1, PAI-1, type IV collagen, NF-κB, NOX4, TLR4, TNFα, IL-1β, and IFN-γ, but they were remarkably suppressed after LJ1888 treatment. In conclusion, our results suggest that LJ1888 has a renoprotective effect in ADX-induced nephropathy, which might be associated with podocyte injury through oxidative stress. Therefore, LJ1888, a selective A3AR antagonist, could be considered as a potential therapeutic agent in renal glomerular diseases which include podocyte injury and proteinuria.