Synthetic Approaches and Clinical Application of Representative Small-Molecule Inhibitors of Cyclin-Dependent Kinase for Cancer Therapy.

The regulation of the cancer cell cycle heavily relies on cyclin-dependent kinases (CDKs). Targeting CDKs has been identified as a promising approach for effective cancer therapy. In recent years, there has been significant attention paid towards developing small-molecule CDK inhibitors in the field of drug discovery. Notably, five such inhibitors have already received regulatory approval for the treatment of different cancers, including breast tumors, lung malignancies, and hematological malignancies. This review provides an overview of the synthetic routes used to produce 17 representative small-molecule CDK inhibitors that have obtained regulatory approval or are currently being evaluated through clinical trials. It also discusses their clinical applications for treating CDK-related diseases and explores the challenges and limitations associated with their use in a clinical setting, which will stimulate the further development of novel CDK inhibitors. By integrating therapeutic applications, synthetic methodologies, and mechanisms of action observed in various clinical trials involving these CDK inhibitors, this review facilitates a comprehensive understanding of the versatile roles and therapeutic potential offered by interventions targeting CDKs.

Design and synthesis of TPP+-Mitomycin C conjugate with reduced toxicity.

Mitomycin C (MMC) is a class of alkylating anticancer drug, which non-specifically interacts with nuclear DNA and cross-links guanine and cytosine of DNA, thereby affecting DNA replication and synthesis. However, toxic effects largely impeded MMC's clinical applications. In this study, triphenylphosphine groups (TPP+) were attached to MMC via the active aziridine amine with the aim to reduce its toxicity. MTT assay suggested that 5 possessed a good anticancer activity (IC50 = 1.09 µM, A549) with negligible effects on human normal cells (IC50 > 20 µM, L02 and HUVEC), while MMC exhibited IC50 values of less than 2.5 µM on the tested human normal cells. Dose range-finding experiments suggested that 5 had little effect on the body weight and tissues in mouse at a dose of 20 mg/kg, indicating significantly reduced toxicity as compared to MMC (LD50 < 2.5 mg/kg). Collectively, these data suggested that TPP+ group could be an effective vector to reduce toxicity of MMC.

Nucleolin-Targeted Ratiometric Fluorescent Carbon Dots with a Remarkably Large Emission Wavelength Shift for Precise Imaging of Cathepsin B in Living Cancer Cells.

As one of the most promising biomarkers for numerous malignant tumors, accurate and reliable reporting of Cathepsin B (CTSB) activity is of great significance to achieve efficient diagnosis of cancers at an early stage and predicting metastasis. Here, we report a vigorous ratiometric fluorescent method integrating a cancer-targeting recognition moiety with a remarkably large emission wavelength shift into a single matrix to report CTSB activity sensitively and specifically. As a proof of concept, we synthesized amine-rich carbon quantum dots (CQDs) with a blue fluorescence, which offered an efficient scaffolding to covalently assemble the nucleolin-targeting recognition nucleic acid aptamer AS1411 and a CTSB-cleavable peptide substrate Gly-Arg-Arg-Gly-Lys-Gly-Gly-Cys-COOH that tethered with a near-infrared (NIR) fluorophore chlorin e6 (Ce6-GRRGKGGC, Ce6-Pep), enabling a cancer-targeting and CTSB stimulus-responsive ratiometric nanoprobe AS1411-Ce6-CQDs. Owing to the efficient fluorescence resonance energy transfer (FRET) process from the CQDs to Ce6 inside the assembly of nanoprobe, the blue fluorescence of CQDs at ∼450 nm was remarkably quenched, along with an obvious NIR fluorescence enhancement of Ce6 at ∼650 nm. After selective entry into cancer cells via nucleolin-mediated endocytosis, the overexpressed CTSB in lysosome could cleave Ce6-Pep and trigger the Ce6 moiety dissociation from AS1411-Ce6-CQDs, thus leading to the termination of FRET process, achieving the efficient ratiometric fluorescence response toward endogenous CTSB with a remarkably large emission wavelength shift of ∼200 nm from NIR to blue emission region. Notably, the nanoprobe AS1411-Ce6-CQDs exhibited an excellent specificity for ratiometric fluorescent sensing of CTSB activity with an ultralow detection limit of 0.096 ng/mL, demonstrating its promising use for early precise cancer diagnosis in the near future.

Novel carbazole-oxadiazoles as potential Staphylococcus aureus germicides.

Staphylococcus aureus resistance poses nonnegligible threats to the livestock industry. In light of this, carbazole-oxadiazoles were designed and synthesized for treating S. aureus infection. Bioassay discovered that 3,6-dibromocarbazole derivative 13a had effective inhibitory activities to several Gram-positive bacteria, in particular to S. aureus, S. aureus ATCC 29213, MRSA and S. aureus ATCC 25923 (MICs = 0.6-4.6 nmol/mL), which was more active than norfloxacin (MICs = 6-40 nmol/mL). Subsequent studies showed that 3,6-dibromocarbazole derivative 13a acted rapidly on S. aureus ATCC 29213 and possessed no obvious tendency to induce bacterial resistance. Further evaluations indicated that 3,6-dibromocarbazole derivative 13a showed strong abilities to disrupt bacterial biofilm and interfere with DNA, which might be the power sources of antibacterial performances. Moreover, 3,6-dibromocarbazole derivative 13a also exhibited slight cell lethality toward Hek 293 T and LO2 cells and low hemolytic toxicity to red blood cells. The above results implied that the active molecule 13a could be studied in the future development of agricultural available antibiotics.

Engineering of a Dual-Recognition Ratiometric Fluorescent Nanosensor with a Remarkably Large Stokes Shift for Accurate Tracking of Pathogenic Bacteria at the Single-Cell Level.

Rapid, accurate, reliable, and risk-free tracking of pathogenic microorganisms at the single-cell level is critical to achieve efficient source control and prevent outbreaks of microbial infectious diseases. For the first time, we report a promising approach for integrating the concepts of a remarkably large Stokes shift and dual-recognition into a single matrix to develop a pathogenic microorganism stimuli-responsive ratiometric fluorescent nanoprobe with speed, cost efficiency, stability, ultrahigh specificity, and sensitivity. As a proof-of-concept, we selected the Gram-positive bacterium Staphylococcus aureus (S. aureus) as the target analyte model, which easily bound to its recognition aptamer and the broad-spectrum glycopeptide antibiotic vancomycin (Van). To improve the specificity and short sample-to-answer time, we employed classic noncovalent π-π stacking interactions as a driving force to trigger the binding of Van and aptamer dual-functionalized near-infrared (NIR) fluorescent Apt-Van-QDs to the surface of an unreported blue fluorescent π-rich electronic carbon nanoparticles (CNPs), achieving S. aureus stimuli-responsive ratiometric nanoprobe Apt-Van-QDs@CNPs. In the assembly of Apt-Van-QDs@CNPs, the blue CNPs (energy donor) and NIR Apt-Van-QDs (energy acceptor) became close to allow the fluorescence resonance energy transfer (FRET) process, leading to a remarkable blue fluorescence quenching for the CNPs at ∼465 nm and a clear NIR fluorescence enhancement for Apt-Van-QDs at ∼725 nm. In the presence of S. aureus, the FRET process from CNPs to Apt-Van-QDs was disrupted, causing the nanoprobe Apt-Van-QDs@CNPs to display a ratiometric fluorescent response to S. aureus, which exhibited a large Stokes shift of ∼260 nm and rapid sample-to-answer detection time (∼30.0 min). As expected, the nanoprobe Apt-Van-QDs@CNPs showed an ultrahigh specificity for ratiometric fluorescence detection of S. aureus with a good detection limit of 1.0 CFU/mL, allowing the assay at single-cell level. Moreover, we also carried out the precise analysis of S. aureus in actual samples with acceptable results. We believe that this work offers new insight into the rational design of efficient ratiometric nanoprobes for rapid on-site accurate screening of pathogenic microorganisms at the single-cell level in the early stages, especially during the worldwide spread of COVID-19 today.

Organocatalytic Asymmetric One-Step Desymmetrizing Dearomatization Reaction of Indoles: Development and Bioactivity Evaluation.

An organocatalytic one-step desymmetrizing dearomatization reaction of indoles with in situ formed vinylidene ortho-quinone methides is reported. A set of [6-6-5] and/or [5-6-5] fused indoline heterocycles were obtained in excellent yields with excellent diastereoselectivities (>20:1 d.r.) and enantioselectivities (up to 99 % ee). Moreover, some of the obtained products were screened against a panel of cancer cell lines, and one was identified to inhibit the proliferation of all the tested cancer cells, but showed marginal effects against non-cancerous cells. The methodology provides a platform for the synthesis of new leading compounds with antitumor activity.

Dichloroacetophenones targeting at pyruvate dehydrogenase kinase 1 with improved selectivity and antiproliferative activity: Synthesis and structure-activity relationships.

Dichloroacetophenone is a pyruvate dehydrogenase kinase 1 (PDK1) inhibitor with suboptimal kinase selectivity. Herein, we report the synthesis and biological evaluation of a series of novel dichloroacetophenones. Structure-activity relationship analyses (SARs) enabled us to identify three potent compounds, namely 54, 55, and 64, which inhibited PDK1 function, activated pyruvate dehydrogenase complex, and reduced the proliferation of NCI-H1975 cells. Mitochondrial bioenergetics assay suggested that 54, 55, and 64 enhanced the oxidative phosphorylation in cancer cells, which might contribute to the observed anti-proliferation effects. Collectively, these results suggested that 54, 55, and 64 could be promising compounds for the development of potent PDK1 inhibitors.

Study the interactions between human serum albumin and two antifungal drugs: fluconazole and its analogue DTP.

Binding affinities of fluconazole and its analogue 2-(2,4-dichlorophenyl)-1,3-di(1H-1,2,4-triazol-yl)-2-propanol (DTP) to human serum albumin (HSA) were investigated under approximately human physiological conditions. The obtained result indicated that HSA could generate fluorescent quenching by fluconazole and DTP because of the formation of non-fluorescent ground-state complexes. Binding parameters calculated from the Stern-Volmer and the Scatchard equations showed that fluconazole and DTP bind to HSA with binding affinities of the order 10(4)L/mol. The thermodynamic parameters revealed that the binding was characterized by negative enthalpy and positive entropy changes, suggesting that the binding reaction was exothermic. Hydrogen bonds and hydrophobic interaction were found to be the predominant intermolecular forces stabilizing the drug-protein. The effect of metal ions on the binding constants of fluconazole-HSA complex suggested that the presence of Mg(2+) and Zn(2+) ions could decrease the free drug level and extend the half-life in the systematic circulation. Docking experiments revealed that fluconazole and DTP binds in HSA mainly by hydrophobic interaction with the possibility of hydrogen bonds formation between the drugs and the residues Arg 222, Lys 199 and Lys 195 in HSA.

Novel aminothiazoximone-corbelled ethoxycarbonylpyrimidones with antibiofilm activity to conquer Gram-negative bacteria through potential multitargeting effects.

The emergence of drug-resistant microorganisms threatens human health, and it is usually exacerbated by the formation of biofilm, which forces the development of new antibacterial agents with antibiofilm activity. In this work, a novel category of aminothiazoximone-corbelled ethoxycarbonylpyrimidones (ACEs) was designed and synthesized, and some of the prepared ACEs showed potent bioactivity against the tested bacteria. In particular, imidazolyl ACE 6c showed better inhibitory activity towards Acinetobacter baumannii and Escherichia coli with MIC values both of 0.0066 mmol/L than norfloxacin. It was also revealed that imidazolyl ACE 6c not only possessed inconspicuous hemolytic rate and cytotoxicity, low drug resistance and no risk of penetrating the blood-brain barrier, but also exhibited obvious biofilm inhibition and eradication activities. The preliminary mechanism research suggested that imidazolyl ACE 6c could induce metabolic dysfunction by deactivating lactate dehydrogenase and promote the accumulation of reactive oxygen species to decrease the reduced glutathione and ultimately cause oxidative damage in bacteria. Furthermore, ACE 6c was also found that could insert into DNA to form the supramolecular complex of 6c-DNA and trigger cell death. The multidimensional effect might promote bacterial cell rupture, leading to the leakage of intracellular content. These findings manifested that novel imidazolyl ACE 6c as a potential multitargeting antibacterial agent with potent antibiofilm activity could provide new possibility for the treatment of refractory biofilm-intensified bacterial infections.

Targeting the pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase (PDC/PDK) axis to discover potent PDK inhibitors through structure-based virtual screening and pharmacological evaluation.

Proliferating cancer cells are characterized by the Warburg effect, a metabolic alteration in which ATP is generated from cytoplasmic glycolysis instead of oxidative phosphorylation. The pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase (PDC/PDK) axis plays a crucial role in this effect and has been identified as a potential target for anticancer drug development. Herein, we present the discovery and pharmacological evaluation of potent PDK inhibitors targeting the PDK/PDC axis. We successfully identified 6 compounds from a small molecule library through a structure-based virtual screening campaign and evaluated their enzymatic inhibitory potencies for PDK1-4. Our results indicated that compound 1 exhibited submicromolar inhibitory activities against PDK1-3 (IC50 = 109.3, 135.8, and 458.7 nM, respectively), but is insensitive to PDK4 (IC50 = 8.67 µM). Furthermore, compound 1 inhibited the proliferation of A549 cells with an EC50 value of 10.7 µM. In addition, compound 1 induced cell apoptosis, arrested the cell cycle at the S phase, and reduced cell invasion and migration, while showing low in vivo toxicity at a high dose. Based on these observations, it can be concluded that compound 1 is a promising anti-PDK1-3 lead that merits further investigation.

Discovery of novel natural-product-derived mutant isocitrate dehydrogenases 1 inhibitors: Structure-based virtual screening, biological evaluation and structure-activity relationship study.

Mutations in IDH1 are commonly observed across various cancers, causing the conversion of α-KG to 2-HG. Elevated levels of 2-HG disrupt histone and DNA demethylation processes, promoting tumor development. Consequently, there is substantial interest in developing small molecule inhibitors targeting the mutant enzymes. Herein, we report a structure-based high-throughput virtual screening strategy using a natural products library, followed by hit-to-lead optimization. Through this process, we discover a potent compound, named 11s, which exhibited significant inhibition to IDH1 R132H and IDH1 R132C with IC50 values of 124.4 and 95.7 nM, respectively. Furthermore, 11s effectively reduced 2-HG formation, with EC50 values of 182 nM in U87 R132H cell, and 84 nM in HT-1080 cell. In addition, 11s significantly reduced U87 R132H and HT-1080 cell proliferation with GC50 values of 3.48 and 1.38 µM, respectively. PK-PD experiments further confirmed that compound 11s significantly decreased 2-HG formation in an HT-1080 xenograft mouse model, resulting in notable suppression of tumor growth without apparent loss in body weight.

Discovery of benzopyridone cyanoacetates as new type of potential broad-spectrum antibacterial candidates.

Unique benzopyridone cyanoacetates (BCs) as new type of promising broad-spectrum antibacterial candidates were discovered with large potential to combat the lethal multidrug-resistant bacterial infections. Many prepared BCs showed broad antibacterial spectrum with low MIC values against the tested strains. Some highly active BCs exhibited rapid sterilization capacity, low resistant trend and good predictive pharmacokinetic properties. Furthermore, the highly active sodium BCs (NaBCs) displayed low hemolysis and cytotoxicity, and especially octyl NaBC 5g also showed in vivo potent anti-infective potential and appreciable pharmacokinetic profiles. A series of preliminary mechanistic explorations indicated that these active BCs could effectively eliminate bacterial biofilm and destroy membrane integrity, thus resulting in the leakage of bacterial cytoplasm. Moreover, their unique structures might further bind to intracellular DNA, DNA gyrase and topoisomerase IV through various direct noncovalent interactions to hinder bacterial reproduction. Meanwhile, the active BCs also induced bacterial oxidative stress and metabolic disturbance, thereby accelerating bacterial apoptosis. These results provided a bright hope for benzopyridone cyanoacetates as potential novel multitargeting broad-spectrum antibacterial candidates to conquer drug resistance.

Development of membrane-targeting TPP+-chloramphenicol conjugates to combat methicillin-resistant staphylococcus aureus (MRSA) infections.

Infections caused by drug-resistant bacteria have become a new challenge in infection treatment, gravely endangering public health. Chloramphenicol (CL) is a well-known antibiotic which has lost its efficacy due to bacterial resistance. To address this issue, herein we report the design, synthesis and biological evaluations of novel triphenylphosphonium chloramphenicol conjugates (TPP+-CL). Study results indicated that compounds 39 and 42 possessed remarkable antibacterial effects against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) with MIC values ranging from 1 to 2 µg/mL, while CL was inactive to the tested MRSA strains. In addition, these conjugates exhibited rapid bactericidal properties and low toxicity, and did not readily induced bacterial resistance, obviously outperforming the parent drug CL. In a mouse model infected with a clinically isolated MRSA strain, compound 39 at a dose of 20 mg/kg exhibited a comparable or even better in vivo anti-MRSA efficacy than the golden standard drug vancomycin, while no toxicity was observed.

Cyanomethylquinolones as a New Class of Potential Multitargeting Broad-Spectrum Antibacterial Agents.

This work identified a class of cyanomethylquinolones (CQs) and their carboxyl analogues as potential multitargeting antibacterial candidates. Most of the prepared compounds showed high antibacterial activities against most of the tested bacteria, exhibiting lower MIC values (0.125-2 µg/mL) than those of clinical norfloxacin, ciprofloxacin, and clinafloxacin. The low hemolysis, drug resistance, and cytotoxicity, as well as good predictive pharmacokinetics of active CQs and carboxyl analogues revealed their development potential. Furthermore, they could eradicate the established biofilm, facilitating bacterial exposure to these antibacterial candidates. These active compounds could induce bacterial death through multitargeting effects, including intercalating into DNA, up-regulating reactive oxygen species, damaging membranes directly, and impeding metabolism. Moreover, the highly active cyclopropyl CQ 15 exhibited more effective in vivo anti-MRSA potency than ciprofloxacin. These findings highlight the potential of CQs and their carboxyl analogues as multitargeting broad-spectrum antibacterial candidates for treating intractable bacterial infections.

Novel berberine triazoles: synthesis, antimicrobial evaluation and competitive interactions with metal ions to human serum albumin.

A series of novel berberine triazoles were synthesized and characterized by IR, NMR, MS and HRMS spectra. All target compounds and their precursors were screened for antimicrobial activities in vitro against four Gram-positive bacteria, four Gram-negative bacteria and two fungal strains. Bioactive assay indicated that most of the prepared compounds exhibited good antibacterial and antifungal activities with low MIC values ranging from 2 to 64 µg/mL, which were comparable to or even better than the reference drugs Berberine, Chloromycin, Norfloxacin and Fluconazole. The competitive interactions between compound 5a and metal ions to Human Serum Albumin (HSA) revealed that the participation of Mg(2+) and Fe(3+) ions in compound 5a-HSA association could result in the concentration increase of free compound 5a, shorten the storage time and half-life of compound 5a in the blood, thus improving its antimicrobial efficacy.

Synthesis and biological evaluation of a class of quinolone triazoles as potential antimicrobial agents and their interactions with calf thymus DNA.

A novel series of quinolone triazoles were synthesized and characterized by IR, NMR, MS and HRMS spectra. All the newly prepared compounds were screened for their antimicrobial activities against seven bacteria and four fungi. Bioactive assay manifested that most of new compounds exhibited good or even stronger antibacterial and antifungal activities against the tested strains including multi-drug resistant MRSA in comparison with reference drugs Norfloxacin, Chloromycin and Fluconazole. The preliminary interactive investigations of compound 6b with calf thymus DNA by fluorescence and UV-vis spectroscopic methods revealed that compound 6b could effectively intercalate DNA to form compound 6b-DNA complex which might block DNA replication and thus exert its antimicrobial activities.

Synthesis and bioactive evaluation of novel hybrids of metronidazole and berberine as new type of antimicrobial agents and their transportation behavior by human serum albumin.

A series of novel hybrids of metronidazole and berberine as new type of antimicrobial agents were synthesized and characterized by (1)H NMR, (13)C NMR, IR, MS and HRMS spectra. Bioactive assay manifested that most of the prepared compounds exhibited effective antibacterial and antifungal activities and some showed comparable or superior potency against Methicillin-resistant Staphylococcus aureus to reference drugs Norfloxacin, Chloromycin and Berberine. The transportation behavior of human serum albumin (HSA) to the highly active compound 5g was evaluated and revealed that the association of imidazole derivative 5g with HSA was spontaneous and the electrostatic interactions played important roles in the transportation of HSA to 5g. The calculated parameters indicated that compound 5g could be effectively stored and carried by HSA.

Cytosolic malic enzyme and glucose-6-phosphate dehydrogenase modulate redox balance in NSCLC with acquired drug resistance.

Lung cancer cells often show elevated levels of reactive oxygen species (ROS) and nicotinamide adenine dinucleotide phosphate (NADPH). However, the connections between deregulated redox homeostasis in different subtypes of lung cancer and acquired drug resistance in lung cancer have not yet been fully established. Herein, we analyzed different subtypes of lung cancer data reported in the Cancer Cell Line Encyclopedia (CCLE) database, the Cancer Genome Atlas program (TCGA), and the sequencing data obtained from a gefitinib-resistant non-small-cell lung cancer (NSCLC) cell line (H1975GR). Using flux balance analysis (FBA) model integrated with multiomics data and gene expression profiles, we identified cytosolic malic enzyme 1 (ME1) and glucose-6-phosphate dehydrogenase as the major contributors to the significantly upregulated NADPH flux in NSCLC tissues as compared with normal lung tissues, and gefitinib-resistant NSCLC cell line as compared with the parental cell line. Silencing the gene expression of either of these two enzymes in two osimertinib-resistant NSCLC cell lines (H1975OR and HCC827OR) exhibited strong antiproliferative effects. Our findings not only underscored the pivotal roles of cytosolic ME1 and glucose-6-phosphate dehydrogenase in regulating redox states in NSCLC cells but also provided novel insights into their potential roles in drug-resistant NSCLC cells with disturbed redox states.

New Efforts toward Aminothiazolylquinolones with Multitargeting Antibacterial Potential.

New antibacterial 3-(aminothiazolyl)quinolones (ATQs) were designed and efficiently synthesized to counteract the growing multidrug resistance in animal husbandry. Bioactive assays manifested that N,N-dicyclohexylaminocarbonyl ATQ 10e and methyl ATQ 17a, respectively, showed better antibacterial behavior against Staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa than reference drug norfloxacin. Notably, highly active ATQ 17a with low hemolysis, negligible mammalian cytotoxicity, and good pharmacokinetic properties displayed low trends to induce resistance and synergistic combinations with norfloxacin. Preliminary mechanism exploration implied that representative ATQ 17a could inhibit the formation of biofilms and destroy bacterial membrane integrity, further binding to intracellular DNA and DNA gyrase to hinder bacterial DNA replication. ATQ 17a could also induce the production of excess reactive oxygen species and reduce bacterial metabolism to accelerate bacterial death. These results provided a promise for 3-(aminothiazolyl)quinolones as new potential multitargeting antibacterial agents to treat bacterial infection of animals.

Azolylpyrimidinediols as Novel Structural Scaffolds of DNA-Groove Binders against Intractable Acinetobacter baumannii.

A unique class of antibacterial azolylpyrimidinediols (APDs) and their analogues were developed. Some synthesized compounds showed excellent bacteriostatic potency; especially, triazolylpyrimidinediol (triazolyl PD) 7a exhibited good anti-Acinetobacter baumannii potential with a low MIC of 0.002 mmol/L. Triazolyl PD 7a with inconspicuous cytotoxicity and hemolytic activity could eradicate the established biofilm, showed low resistance, and exhibited favorable drug-likeness. Mechanistic explorations revealed that compound 7a without membrane-targeting ability could decrease metabolic activity, interact with DNA through groove binding action to block DNA replication rather than intercalate into and cleave DNA, and thus inhibit bacterial growth. Further computations displayed that the low EHOMO and large energy gap might help triazolyl PD 7a binding to biological targets more easily. Moreover, compound 7a gave appreciable in vivo pharmacokinetic properties and pharmacodynamics. These findings of azolylpyrimidinediols as novel structural scaffolds of DNA-groove binders might imply a large promise for the treatments of Acinetobacter baumannii infection.