Enhancing nicotinamide N-methyltransferase bisubstrate inhibitor activity through 7-deazaadenosine and linker modifications.

Nicotinamide N-methyltransferase (NNMT) catalyzes the transfer of a methyl group from S-adenosylmethionine (SAM) to nicotinamide (NAM) and other pyridine-related compounds and is involved in various metabolic processes in the human body. In addition, abnormal expression of NNMT occurs under various pathological conditions such as cancer, diabetes, metabolic disorders, and neurodegenerative diseases, making it a promising drug target worthy of in-depth research. Small-molecule NNMT inhibitors with high potency and selectivity are necessary chemical tools to test biological hypotheses and potential therapies. In this study, we developed a series of highly active NNMT inhibitors by modifying N7 position of adenine. Among them, compound 3-12 (IC50 = 47.9 ± 0.6 nM) exhibited potent inhibitory activity and also had an excellent selectivity profile over a panel of human methyltransferases. We showed that the N7 position of adenine in the NNMT bisubstrate inhibitor was a modifiable site, thus offering insights into the development of NNMT inhibitors.

Design, Synthesis, and Resolution of Spirocyclic Bisoxindole-Based C2-Symmetric Diols.

A new type of spirocyclic bisoxindole-based C2-symmetric diols (SBIDOLs) was designed and synthesized. A series of racemic SBIDOL derivatives (6a-6g) were readily synthesized from commercially available 2-halo-5-methoxyanilines 1 (X = Cl or Br) through N-mono alkylation, acylation, oxidation, double intramolecular Friedel-Crafts reaction, and demethylation reactions. The optical resolution of racemic 6b was achieved via fractional crystallization of their bis-l-menthoxycarboxylates. Further modifications of SBIDOLs were investigated, leading to 5,5'-diaryl SBIDOL derivatives (11a and 11b) through Pd-catalyzed Suzuki coupling and DM-SBIDOL 12 by Pd/C-catalyzed hydrogenative dechlorination reactions.

Synthesis and computational studies of highly selective inhibitors of human recombinant tissue non-specific alkaline phosphatase (h-TNAP): A therapeutic target against vascular calcification.

In this study, we have discovered small druglike molecules as selective inhibitors of human tissue-nonspecific alkaline phosphatase (h-TNAP), an enzyme critical for the regulation of extracellular matrix calcification. The upregulation of h-TNAP is associated with various pathologies particularly the vascular calcification (VC). Selective inhibition of h-TNAP over h-NPP1 may serve as a useful therapeutic strategy against vascular calcification. A series of novel triazolyl pyrazole derivatives (10a-y) in which thiol bearing triazole moiety as the zinc binding functional group was introduced to a pyrazole based pharmacophore was synthesized and evaluated as potent and selective inhibitors of h-TNAP over h-NPP1. The biological screening against h-TNAP, h-IAP, h-NPP1 and h-NPP3 showed that many of the synthesized compounds are selective inhibitors of TNAP. Particularly, the compounds 10a-h, 10j, 10m-q, 10u, 10w and 10x displayed high potency and complete selectivity towards h-TNAP over h-NPP1. Compound 10q emerged as a highly potent inhibitor (IC50 = 0.16 µM or 160 nM) against h-TNAP with 127-fold increased inhibition compared to levamisole. On the other hand, compound 10e was found to be most selective inhibitor against the tested APs and NPPs (IC50 = 1.59 ± 0.36 µM). Binding sites architecture analysis, molecular-docking and molecular dynamics simulations (MDS), revealed the basis for h-TNAP and h-IAP ligand selectivity as well as selectivity towards h-TNAP over h-NPP1. These newly discovered inhibitors are believed to represent valuable lead structures to further streamline the generation of candidate compounds to target VC.

Ligand binding and heterodimerization with retinoid X receptor α (RXRα) induce farnesoid X receptor (FXR) conformational changes affecting coactivator binding.

Nuclear receptor farnesoid X receptor (FXR) functions as the major bile acid sensor coordinating cholesterol metabolism, lipid homeostasis, and absorption of dietary fats and vitamins. Because of its central role in metabolism, FXR represents an important drug target to manage metabolic and other diseases, such as primary biliary cirrhosis and nonalcoholic steatohepatitis. FXR and nuclear receptor retinoid X receptor α (RXRα) form a heterodimer that controls the expression of numerous downstream genes. To date, the structural basis and functional consequences of the FXR/RXR heterodimer interaction have remained unclear. Herein, we present the crystal structures of the heterodimeric complex formed between the ligand-binding domains of human FXR and RXRα. We show that both FXR and RXR bind to the transcriptional coregulator steroid receptor coactivator 1 with higher affinity when they are part of the heterodimer complex than when they are in their respective monomeric states. Furthermore, structural comparisons of the FXR/RXRα heterodimers and the FXR monomers bound with different ligands indicated that both heterodimerization and ligand binding induce conformational changes in the C terminus of helix 11 in FXR that affect the stability of the coactivator binding surface and the coactivator binding in FXR. In summary, our findings shed light on the allosteric signal transduction in the FXR/RXR heterodimer, which may be utilized for future drug development targeting FXR.

Rational design, synthesis and biological evaluation of ubiquinone derivatives as IDO1 inhibitors.

Indoleamine 2,3-dioxygenase 1 (IDO1) is an attractive therapeutic target for the treatment of cancer, chronic viral infections and neurological disorders characterized by pathological immune stimulation. Herein, a series of known metal-chelating ubiquinone derivatives were designed, synthesized and evaluated for the IDO1 inhibiting activities. The docking studies showed that the compounds 11, 16, 18 and coenzyme-Q1 exhibited different binding modes to IDO1 protein. Among these compounds, the most active compound is 16d with an IC50 of 0.13 µM in enzymatic assay. The results reveal that a possible halogen bonding interaction between the bromine atom (3-Br) and Cys129 significantly enhances the inhibition activity against IDO1. This study provides structural insights of the interactions between ubiquinone analogues and IDO1 protein for the further modification and optimization.

Acetylation of Aurora B by TIP60 ensures accurate chromosomal segregation.

Faithful segregation of chromosomes in mammalian cells requires bi-orientation of sister chromatids, which relies on the sensing of correct attachments between spindle microtubules and kinetochores. Although the mechanisms underlying cyclin-dependent kinase 1 (CDK1) activation, which triggers mitotic entry, have been extensively studied, the regulatory mechanisms that couple CDK1-cyclin B activity to chromosome stability are not well understood. Here, we identified a signaling axis in which Aurora B activity is modulated by CDK1-cyclin B via the acetyltransferase TIP60 in human cell division. CDK1-cyclin B phosphorylates Ser90 of TIP60, which elicits TIP60-dependent acetylation of Aurora B and promotes accurate chromosome segregation in mitosis. Mechanistically, TIP60 acetylation of Aurora B at Lys215 protects Aurora B's activation loop from dephosphorylation by the phosphatase PP2A to ensure a robust, error-free metaphase-anaphase transition. These findings delineate a conserved signaling cascade that integrates protein phosphorylation and acetylation with cell cycle progression for maintenance of genomic stability.

Mechanistic insights into peptide and ligand binding of the ATAD2-bromodomain via atomistic simulations disclosing a role of induced fit and conformational selection.

ATAD2 has emerged as a promising bromodomain (BRD)-containing therapeutic drug target in multiple human cancers. However, recent druggability assessment studies predicted ATAD2's BRD as a target 'difficult to drug' because its binding pocket possesses structural features that are unfeasible for ligand binding. Here, by using all-atom molecular dynamics simulations and an advanced metadynamics method, we demonstrate a dynamic view of the binding pocket features which can hardly be obtained from the "static" crystal data. The most important features disclosed from our simulation data, include: (1) a distinct 'open-to-closed' conformational switch of the ZA loop region in the context of peptide or ligand binding, akin to the induced fit mechanism of molecular recognition, (2) a dynamic equilibrium of the BC loop "in" and "out" conformations, highlighting a role in the conformational selection mechanism for ligand binding, and (3) a new binding region identified distal to the histone-binding pocket that might have implications in bromodomain biology and in inhibitor development. Moreover, based on our simulation results, we propose a model for an "auto-regulatory" mechanism of ATAD2's BRD for histone binding. Overall, the results of this study will not only have implications in bromodomain biology but also provide a theoretical basis for the discovery of new ATAD2's BRD inhibitors.

Discovery of hepatitis B virus capsid assembly inhibitors leading to a heteroaryldihydropyrimidine based clinical candidate (GLS4).

Inhibition of hepatitis B virus (HBV) capsid assembly is a novel strategy for the development of chronic hepatitis B (CHB) therapeutics. Herein we described our lead optimization studies including the synthesis, molecular docking studies and structure-activity relationship (SAR) studies of a series of novel heteroaryldihydropyrimidine (HAP) inhibitors of HBV capsid assembly inhibitors, and the discovery of a potent inhibitor of HBV capsid assembly of GLS4 (ethyl 4-[2-bromo-4-fluorophenyl]-6-[morpholino-methyl]-2-[2-thiazolyl]-1,4-dihydro-pyrimidine-5-carboxylate) which is now in clinical phase 2. GLS4 demonstrated potent inhibitory activities in HBV HepG2.2.15 cell assay with an EC50 value of 1nM, and it also exhibited high potency against various drug-resistant HBV viral strains with EC50 values in the range of 10-20nM, more potent than the typical HBV polymerase inhibitors such as lamivudine, telbivudine, and entecavir. Pharmacokinetic profiles of GLS4 were favorable and safety evaluation including acute toxicity and repeated toxicity study indicated that GLS4 was safe enough to support clinical experiments in human.

Implications of MDSCs-targeting in lung cancer chemo-immunotherapeutics.

Despite advances in chemotherapy and immunotherapy, advanced lung cancer remains an incurable disease. Novel trends in anticancer therapeutics focus on harnessing the therapeutically-targeted tumor-related immune suppression. In this respect, myeloid-derived suppressor cells (MDSCs) have captured considerable attention in the last few years, as they are vividly implicated in tumor immune escape mechanisms. In this review, we specifically discuss the multifaceted roles of MDSCs in lung tumor microenvironment, encompassing lung tumor growth and progression via suppression of anti-tumor immunity, association with worse prognosis, and hampering the efficacy of lung cancer chemotherapy and immunotherapy. In addition, we also discuss that therapeutic manipulation of MDSCs-targeting, either alone or in combination with chemo- and/or immune-therapeutic regimens, may not only have tumor growth inhibition, anti-angiogenesis and anti-metastasis effects, but may also have the potential to enhance the efficacy of lung cancer chemotherapy and immunotherapy.

Skp1: Implications in cancer and SCF-oriented anti-cancer drug discovery.

In the last decade, the ubiquitin proteasome system (UPS), in general, and E3 ubiquitin ligases, in particular, have emerged as valid drug targets for the development of novel anti-cancer therapeutics. Cullin RING Ligases (CRLs), which can be classified into eight groups (CRL1-8) and comprise approximately 200 members, represent the largest family of E3 ubiquitin ligases which facilitate the ubiquitination-derived proteasomal degradation of a myriad of functionally and structurally diverse substrates. S phase kinase-associated protein 1 (Skp1)-Cullin1-F-Box protein (SCF) complexes are the best characterized among CRLs, which play crucial roles in numerous cellular processes and physiological dysfunctions, such as in cancer biology. Currently, there is growing interest in developing SCF-targeting anti-cancer therapies for clinical application. Indeed, the research in this field has seen some progress in the form of cullin neddylation- and Skp2-inhibitors. However, it still remains an underdeveloped area and needs to design new strategies for developing improved form of therapy. In this review, we venture a novel strategy that rational pharmacological targeting of Skp1, a central regulator of SCF complexes, may provide a novel avenue for SCF-oriented anti-cancer therapy, expected: (i) to simultaneously address the critical roles that multiple SCF oncogenic complexes play in cancer biology, (ii) to selectively target cancer cells with minimal normal cell toxicity, and (iii) to offer multiple chemical series, via therapeutic interventions at the Skp1 binding interfaces in SCF complex, thereby maximizing chances of success for drug discovery. In addition, we also discuss the challenges that might be posed regarding rational pharmacological interventions against Skp1.

Mitotic regulator Mis18ß interacts with and specifies the centromeric assembly of molecular chaperone holliday junction recognition protein (HJURP).

The centromere is essential for precise and equal segregation of the parental genome into two daughter cells during mitosis. CENP-A is a unique histone H3 variant conserved in eukaryotic centromeres. The assembly of CENP-A to the centromere is mediated by Holliday junction recognition protein (HJURP) in early G1 phase. However, it remains elusive how HJURP governs CENP-A incorporation into the centromere. Here we show that human HJURP directly binds to Mis18ß, a component of the Mis18 complex conserved in the eukaryotic kingdom. A minimal region of HJURP for Mis18ß binding was mapped to residues 437-460. Depletion of Mis18ß by RNA interference dramatically impaired HJURP recruitment to the centromere, indicating the importance of Mis18ß in HJURP loading. Interestingly, phosphorylation of HJURP by CDK1 weakens its interaction with Mis18ß, consistent with the notion that assembly of CENP-A to the centromere is achieved after mitosis. Taken together, these data define a novel molecular mechanism underlying the temporal regulation of CENP-A incorporation into the centromere by accurate Mis18ß-HJURP interaction.

Chromatin protein HP1 interacts with the mitotic regulator borealin protein and specifies the centromere localization of the chromosomal passenger complex.

Accurate mitosis requires the chromosomal passenger protein complex (CPC) containing Aurora B kinase, borealin, INCENP, and survivin, which orchestrates chromosome dynamics. However, the chromatin factors that specify the CPC to the centromere remain elusive. Here we show that borealin interacts directly with heterochromatin protein 1 (HP1) and that this interaction is mediated by an evolutionarily conserved PXVXL motif in the C-terminal borealin with the chromo shadow domain of HP1. This borealin-HP1 interaction recruits the CPC to the centromere and governs an activation of Aurora B kinase judged by phosphorylation of Ser-7 in CENP-A, a substrate of Aurora B. Consistently, modulation of the motif PXVXL leads to defects in CPC centromere targeting and aberrant Aurora B activity. On the other hand, the localization of the CPC in the midzone is independent of the borealin-HP1 interaction, demonstrating the spatial requirement of HP1 in CPC localization to the centromere. These findings reveal a previously unrecognized but direct link between HP1 and CPC localization in the centromere and illustrate the critical role of borealin-HP1 interaction in orchestrating an accurate cell division.

Synthesis and biological evaluation of 3,5-disubstituted-4-alkynylisoxozales as a novel class of HSP90 inhibitors.

A series of 3,5-disubstitute-4-alkynylisoxazole derivatives were designed and synthesized through palladium(II)-copper(I) catalyzed Sonogashira cross-coupling reaction of an alkynyl moiety and an isoxazole scaffold as novel HSP90 inhibitors. The resultant compounds displayed moderate to potent binding affinity to HSP90 proteins, and also demonstrated good cell growth inhibitory activity against various cancer cell lines (A549, K562, MCF-7, DU145 and Hela). Some compounds (18d, 18e, 19a, 19d, 20c and 20q) show similar or better binding affinity towards HSP90α and HSP90ß comparing to NVP-AUY922. In addition, compounds 18e, 19a and 20q exhibited potent inhibitory activity against various human cancer cell lines.

Polyvalent mpox mRNA vaccines elicit robust immune responses and confer potent protection against vaccinia virus.

The 2022 mpox outbreak led the World Health Organization (WHO) to declare it a public health emergency of international concern (PHEIC). There is a need to develop more effective and safer mpox virus (MPXV)-specific vaccines in response to the mpox epidemic. The mRNA vaccine is a promising platform to protect against MPXV infection. In this study, we construct two bivalent MPXV mRNA vaccines, designated LBA (B6R-A29L) and LAM (A35R-M1R), and a quadrivalent mRNA vaccine, LBAAM (B6R-A35R-A29L-M1R). The immunogenicity and protective efficacy of these vaccines alone or in combination were evaluated in a lethal mouse model. All mRNA vaccine candidates could elicit potential antigen-specific humoral and cellular immune responses and provide protection against vaccinia virus (VACV) infection. The protective effect of the combination of two bivalent mRNA vaccines and the quadrivalent vaccine was superior to that of the individual bivalent mRNA vaccine. Our study provides valuable insights for the development of more efficient and safer mRNA vaccines against mpox.

CENP-E kinesin interacts with SKAP protein to orchestrate accurate chromosome segregation in mitosis.

Mitotic chromosome segregation is orchestrated by the dynamic interaction of spindle microtubules with the kinetochore. Although previous studies show that the mitotic kinesin CENP-E forms a link between attachment of the spindle microtubule to the kinetochore and the mitotic checkpoint signaling cascade, the molecular mechanism underlying dynamic kinetochore-microtubule interactions in mammalian cells remains elusive. Here, we identify a novel interaction between CENP-E and SKAP that functions synergistically in governing dynamic kinetochore-microtubule interactions. SKAP binds to the C-terminal tail of CENP-E in vitro and is essential for an accurate kinetochore-microtubule attachment in vivo. Immunoelectron microscopic analysis indicates that SKAP is a constituent of the kinetochore corona fibers of mammalian centromeres. Depletion of SKAP or CENP-E by RNA interference results in a dramatic reduction of inter-kinetochore tension, which causes chromosome mis-segregation with a prolonged delay in achieving metaphase alignment. Importantly, SKAP binds to microtubules in vitro, and this interaction is synergized by CENP-E. Based on these findings, we propose that SKAP cooperates with CENP-E to orchestrate dynamic kinetochore-microtubule interaction for faithful chromosome segregation.

Design, synthesis, and biological evaluation of novel 2'-methyl-2'-fluoro-6-methyl-7-alkynyl-7-deazapurine nucleoside analogs as anti-Zika virus agents.

Zika virus (ZIKV) is a mosquito-borne flavivirus and outbreaks of ZIKV have been reported in Africa, Americas and other parts of the world lately. The ZIKV epidemic has received extensive attention due to its ability to cause serious medical consequences and complications such as microcephaly and Guillain-Barre syndrome in recent years. Up to now, there are no specific treatments or vaccines available for ZIKV infection, which highlights the urgent need for developing new therapies. In this work, we designed and synthesized a series of novel 6-methyl-7-acetylenenyl-7-deazapurine nucleoside analogs as potential inhibitors of ZIKV replication. The biological activities against ZIKV replication were evaluated and the structure-activity relationship (SAR) was also studied. Among the compounds evaluated, nucleoside analog 38 (EC50 = 2.8 ± 0.8 µM, EC90 = 6.8 ± 2.3 µM) showed the most potent anti-ZIKV activity with low cytotoxicity (CC50 = 54.1 ± 6.9 µM) in an A549 based cellular model. The inhibitory activity of 38 was about 5 times more potent than the positive control NITD008. Notably, 38 showed similar inhibition potency against different ZIKV strains (ZG-01 and MR766) in a variety of host cell types including SNB19, A549, Huh7, Vero. In addition, 38 (Kd = 1.87 µM) has a stronger affinity to ZIKV RNA-dependent RNA polymerase (RdRp) protein than NITD008 (Kd = 3.43 µM) in the non-phosphorylation assay. These results indicated that compound 38 may serve as a promising candidate in future anti-ZIKV drug discovery.

A small-molecule Skp1 inhibitor elicits cell death by p53-dependent mechanism.

Skp1 overexpression promotes tumor growth, whereas reduced Skp1 activity is also linked with genomic instability and neoplastic transformation. This highlights the need to gain better understanding of Skp1 biology in cancer settings. To this context, potent and cellularly active small-molecule Skp1 inhibitors may be of great value. Using a hypothesis-driven, structure-guided approach, we herein identify Z0933M as a potent Skp1 inhibitor with KD ∼0.054 µM. Z0933M occupies a hydrophobic hotspot (P1) - encompassing an aromatic cage of two phenylalanines (F101 and F139) - alongside C-terminal extension of Skp1 and, thus, hampers its ability to interact with F-box proteins, a prerequisite step to constitute intact and active SCF E3 ligase(s) complexes. In cellulo, Z0933M disrupted SCF E3 ligase(s) functioning, recapitulated previously reported effects of Skp1-reduced activity, and elicited cell death by a p53-dependent mechanism. We propose Z0933M as valuable tool for future efforts toward probing Skp1 cancer biology, with implications for cancer therapy.

Dimerization of CPAP orchestrates centrosome cohesion plasticity.

Centrosome cohesion and segregation are accurately regulated to prevent an aberrant separation of duplicated centrosomes and to ensure the correct formation of bipolar spindles by a tight coupling with cell cycle machinery. CPAP is a centrosome protein with five coiled-coil domains and plays an important role in the control of brain size in autosomal recessive primary microcephaly. Previous studies showed that CPAP interacts with tubulin and controls centriole length. Here, we reported that CPAP forms a homodimer during interphase, and the fifth coiled-coil domain of CPAP is required for its dimerization. Moreover, this self-interaction is required for maintaining centrosome cohesion and preventing the centrosome from splitting before the G(2)/M phase. Our biochemical studies show that CPAP forms homodimers in vivo. In addition, both monomeric and dimeric CPAP are required for accurate cell division, suggesting that the temporal dynamics of CPAP homodimerization is tightly regulated during the cell cycle. Significantly, our results provide evidence that CPAP is phosphorylated during mitosis, and this phosphorylation releases its intermolecular interaction. Taken together, these results suggest that cell cycle-regulated phosphorylation orchestrates the dynamics of CPAP molecular interaction and centrosome splitting to ensure genomic stability in cell division.

Organocatalytic Asymmetric Arylation of p-Quinone Phosphonates: A Green Access to Biaryl Monophosphorus Ligands.

Herein, we report a highly efficient organocatalytic asymmetric synthesis of axially chiral biaryl phosphonates with p-quinone phosphonates and 2-naphthols via CPA-catalyzed asymmetric arylations. A series of chiral biaryl monophosphonates were obtained in excellent yields and enantioselectivities (up to 99% yield and 95% ee). This reaction could be operated at a gram scale with a low catalyst loading (0.5 mol %). Remarkably, our approach provides a green and ready access to chiral biaryl monophosphorus ligands. Compound 4ca was successfully converted to novel chiral biaryl monophosphorus ligands 7a, 7b, and 8 with high enantioselectivities in three steps.

The development of HEC-866 and its analogues for the treatment of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with a typical survival time between three to five years. Two drugs, pirfenidone and nintedanib have been approved for the treatment of IPF, but they have limited efficacy. Thus, the development of new drugs to treat IPF is an urgent medical need. In this paper we report the discovery of a series of orally active pyrimidin-4(3H)-one analogs which exhibit potent activity in in vitro assays. Among them, HEC-866 showed promising efficacy in rat IPF models. Since HEC-866 also had good oral bioavailability, a long half-life and favorable long-term safety profiles, it was selected for further clinical evaluation.