The family Flaviviridae, encompassing DENV and HCV, poses a substantial threat to global public health, with no clinically approved antiviral agents available for DENV and emerging resistance challenges complicating HCV management. NS4B has emerged as a promising antiviral target due to its indispensable roles in membrane remodeling, viral RNA replication, and innate immune evasion. This review provides a comprehensive medicinal chemistry perspective on the development of small-molecule NS4B inhibitors, systematically summarizing recent advances in structural and functional studies of DENV NS4B and HCV NS4B with particular emphasis on their critical protein-protein interactions with viral partners. We critically analyze the current landscape of small-molecule NS4B inhibitors developed over the past decade, covering diverse chemical scaffolds, including indole, imidazole, pyrazole, quinoline, thiazole, and thiophene derivatives. The SARs, mechanisms of action, and preclinical or clinical development status of these inhibitors are discussed in detail. Furthermore, we address current challenges, including drug resistance, suboptimal pharmacokinetic properties, and incomplete pan-genotypic coverage, and propose future directions for the rational design of next-generation NS4B-targeted therapeutics. This review aims to provide valuable insights for the discovery of potent antiviral agents to combat infections caused by the family Flaviviridae.
Many diseases, including cancer, are characterized by increased or decreased expression of specific genes. These changes can occur without genome alteration, primarily modulated by the addition or removal of epigenetic markers, which influence chromatin condensation and architecture. Genes in more condensed chromatin regions have lower expression and the opposite also applies. In the last twenty-two years, small molecule inhibitors of enzymes responsible for chromatin deacetylation or methylation have successfully moved from preclinical discovery to clinical therapy. This review explores the ten epigenetic drugs that have attained worldwide regulatory approval for human therapy: the DNA methyltransferase inhibitors azacitidine (2004) and decitabine (2006), the histone deacetylase inhibitors vorinostat (2006), romidepsin (2009), belinostat (2014), panobinostat (2015) tucidinostat (2015) and givinostat (2024), and the histone methyltransferase inhibitors tazemetostat (2020) and valemetostat (2022). The history and strategy of their discovery and development, their biological targets and mechanisms of action and their therapeutic use. In addition, current advancements and efforts, as well as future perspectives in the design and clinical approval of new epigenetic drugs are discussed.
Cardiovascular disease (CVD) encompasses a group of severe cardiac and vascular disorders with high global prevalence and mortality rates. CVD is characterized by abnormal cell death and inflammation of cardiomyocytes and vascular endothelial cells, involving mutually interconnected pathogenic mechanisms. N6-methyladenosine (m6A) RNA modification has emerged as a key mechanism promoting the progression of CVDs through regulation of gene expression. Among the key mediators, Methyltransferase-like 14 (METTL14)-mediated m6A modification modulates the stability of mRNAs and the processing of pre-miRNAs. We critically discuss recent advances elucidating the function of METTL14 in regulating cardiomyocyte death, which leads to myocardial ischemia/reperfusion injury, heart failure and cardiac fibrosis. In addition, METTL14 promotes endothelial inflammation and atherosclerosis. The long noncoding RNA NEAT1 serves as a central effector integrating the functions of most METTL14 substrates in the pathogenesis of CVD. These analyses on METTL14-mediated signaling pathways highlight METTL14, PHLPP2, TLR4 and NEAT1 as potential therapeutic targets. We thoroughly discuss the structure-based design, binding mechanisms, potency, pharmacokinetic properties and safety of small peptides directly targeting METTL14, and stapled peptides disrupting the interface between METTL3 and METT14 in the catalytic complex. The advantages and limitations of these peptides are compared with METTL3-targeting proteolysis-targeting chimeras (PROTACs), which induce the degradation of both METTL3 and METTL14. Our molecular docking analyses, combined with previous structural biology and medicinal chemistry studies, propose potential binding modes of inhibitors to METTL14, PHLPP1/2, and TLR4. These interdisciplinary discussion reveals various novel concepts in designing the therapeutics to combat METTL14-mediated pathologies.
The rapid emergence of multidrug-resistant (MDR) bacterial pathogens necessitates the development of new antibacterial chemotherapeutics with improved efficacy and additional therapeutic benefits. Here, in this study we have conjugated spermine with non-steroidal anti-inflammatory drugs (NSAID) as potent antibacterials with anti-inflammatory properties. Among the synthesized compounds, RNP-11, a gemini amphiphilic conjugate of spermine and flufenamic acid, exhibited potent antibacterial activity with minimum inhibitory concentrations (MICs) of 2-4 μg/mL against a broad panel of Staphylococcal and Enterococcus species, including clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). Interestingly, RNP-11 exhibited a superior post-antibiotic effect relative to vancomycin as the RNP-11 did not induce any detectable resistance even after thirty-three generations of bacterial exposure. Mechanistic investigations revealed a concentration-dependent membrane-disruptive antibacterial mode of action, wherein RNP-11 visibly disrupts and damages bacterial membranes at 5×MIC. Furthermore, RNP-11 retained the anti-inflammatory characteristics of its parent NSAID, displaying selective COX-2 inhibition and suppression of pro-inflammatory cytokine production. This dual-action capability allows the molecule to simultaneously eradicate pathogens and mitigate the host's inflammatory response. The therapeutic viability of this hybrid strategy was successfully validated in a murine skin-infection model, where RNP-11 achieved significant bacterial reduction of S. aureus. Collectively, these findings establish spermine-NSAID conjugation as an effective strategy for developing dual-action antibacterial agents for the treatment of persistent drug-resistant infections.
Synthetic lethality has emerged as a transformative therapeutic paradigm in precision oncology, offering unprecedented tumor selectivity while minimizing off-target toxicity-a longstanding limitation of conventional cancer therapies. PKMYT1, a key regulator of CDK1 phosphorylation, represents a promising therapeutic target for cancers with specific DNA damage response deficiencies driven by its synthetic lethal relationship with CCNE1 amplification. Herein, we report the rational design and synthesis of a novel class of PKMYT1 inhibitors via structure-based drug design, integrating three core optimization strategies: proposed water displacement to enhance direct ligand-protein binding, metabolic soft-spot shielding to mitigate metabolic liability, and steric hindrance modulation to preserve critical axial chirality. Through systematic structural refinement of the clinical-stage lead RP-6306, we identified compound 6-A as a favorable candidate featuring enhanced pharmacological profiles and improved in vitro metabolic stability, with no detectable cardiotoxic or genotoxic risks. This compound potently and selectively inhibits PKMYT1, suppresses CDK1 phosphorylation, and exerts robust antiproliferative effects in CCNE1-amplified cell lines. It exhibits favorable metabolic stability and demonstrates significant in vivo antitumor efficacy yet shows only moderate oral exposure in vivo, which warrants further structural optimization. Notably, combination therapy with gemcitabine achieved near-complete inhibition of tumor progression in OVCAR3 xenograft models, with no overt systemic toxicity. Collectively, these results validate compound 6-A as an attractive lead scaffold for further development and underscore the value of the proposed scaffold optimization approach in facilitating targeted treatment of CCNE1-amplified cancers.
25-Hydroxycholesterol (25-HC) and 25R,26-hydroxycholesterol (25R,26-HC) are two endogenous oxysterols endowed with broad-spectrum antiviral activity. They hamper viral replication by targeting oxysterol-binding protein (OSBP), a host lipid transporter which plays a critical role in the replicative cycle of several viruses. Recently, we have reported the remarkable antiviral activity against herpes simplex virus 2 (HSV-2) of N,N-dimethyl-3β-hydroxychol-5-en-24-amide (PFM067, 3), identified by the screening of our synthetic oxysterol library. Further development of antiviral cholenamide-based fluorescent probes allowed us to support the hypothesis that OSBP was involved in the antiviral mechanism of action of the parent PFM067. Herein, we report the first study aimed at the definition of structure-antiviral activity relationships for PFM067 (3); successfully, we identified 24-(morpholin-4-yl)-3β-hydroxychol-5-en-24-one (8d), as highly potent, nanomolar inhibitor of HSV-2 replication, endowed with promising selectivity index. Moreover, we demonstrated that OSBP was the molecular target underlying the anti-HSV-2 activity of PFM067 (3) and its analogues by the development of a microscale thermophoresis binding assay. In-depth experiments performed using an OSBP-silenced cell line allowed us to disclose the role played by OSBP in the replicative cycle of HSV-2. Finally, molecular modelling studies evidenced a peculiar orientation of the active compound 8d within the binding site of OSBP respect to that stroked by either the endogenous ligand or an inactive compound.
Developing drugs to treat rhinovirus (RV) infections remains a serious and unresolved problem. Pleconaril is the most widely studied broad-spectrum RV inhibitor. Fewer than 10 % of circulating RV types are naturally resistant to pleconaril, which is why researchers continue to study it as a basis for creating new, more active molecules. We conducted a comprehensive study on modifying the pleconaril molecule and demonstrated that the isoxazole ring is crucial for determining anti-RV activity. Based on these findings, we aimed to further study the pleconaril core to discover new therapeutic candidates. We synthesized a large series of new pleconaril derivatives with mono- or di-substituted central phenyl rings, modified linkers, and substitutions on the isoxazole or 1,2,4-oxadiazole moieties. We evaluated the cytotoxicity and inhibitory activity of the obtained compounds using RV-A2 and RV-B14 strains in HeLa cells. To explain the differences in inhibitory profiles, we performed molecular dynamics simulations. Results from the structure-activity relationship analysis revealed that the substituents on the isoxazole and 1,2,4-oxadiazole rings, as well as the linker, play a decisive role in the anti-RV activity profile of monomethylated pleconaril derivatives. We demonstrated that the movement of two loops at the entrance of the VP1 binding pocket of the capsid protein and the inhibitor molecules correlates with the stability of the complex, and therefore, with efficacy against RV. Compounds 1q, 1gg, 2g, and 4c were identified as potent new RV inhibitors from this series of compounds. These compounds are promising new candidates for lead optimization and preclinical studies in the development of antiviral drugs against RV.
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a validated therapeutic target for regulating low-density lipoprotein cholesterol (LDL-C) levels and treating dyslipidemia-related cardiovascular diseases. In this study, pharmacophore-based virtual screening identified 4 (ZINC4681905) as a lead compound, which was subsequently optimized into a series of N,N'-diacyl-m-phenylenediamine derivatives. A total of fourteen compounds were synthesized and evaluated using a fluorescence polarization-based assay. Among them, compound 4a exhibits the highest potency with an IC50 value of 1.07 μM, surpassing that of the positive control berberine (IC50 = 2.59 μM), while compound 4f shows comparable activity. Structure-activity relationship (SAR) analysis revealed that the inhibitory activity of this N,N'-diacyl-m-phenylenediamine scaffold is influenced by the cooperative interplay of the two terminal substituents, with a combination of a multisubstituted hydrophobic aryl group and a flexible, bulky alicyclic moiety affording favorable potency. In cell-based assays, 4a reduced PCSK9 expression and concurrently increased low-density lipoprotein receptor (LDLR) levels in HK-2 cells, and this effect was partially rescued by PCSK9 overexpression, providing supportive cell-based evidence for the involvement of the PCSK9 pathway. Collectively, these findings support further optimization of this scaffold as a potential class of small molecule PCSK9 inhibitors. However, direct LDL uptake assays and assessment of PCSK9-LDLR interaction disruption have not been performed; therefore, the functional evidence remains preliminary.
Non-small cell lung cancer (NSCLC) is one of the deadliest malignancies, which is mostly caused by activating mutations in the epidermal growth factor receptor (EGFR). While EGFR tyrosine kinase inhibitors (TKIs) of the first, second, and third generations have improved patient outcomes, long-term efficacy is often compromised by acquired resistance caused by mutations like T790 M and C797S. The discovery and promise of small-molecule allosteric modulators, including both reversible allosteric, ATP dual targeting inhibitors and targeted protein degraders (PROTACs) that employ allosteric binding for mutant-selective EGFR degradation that target mutant EGFR in NSCLC treatment are thoroughly evaluated in this study. We detail advances in design strategies and structure-activity relationship (SAR) studies of various compounds, including marine-derived Clathrin analogues, and a spectrum of heterocyclic derivatives catalogued as C1-C19. The integration of in silico docking, molecular dynamics simulations, and in vitro/in vivo evaluations reveals that modifications to functional groups, heterocyclic scaffolds, and linker structures are critical for enhancing binding affinity and selectivity toward the allosteric site, while acknowledging that the proposed SAR trends and pharmacophore model require further experimental validation through co-crystallization and systematic analogue studies across different chemotypes. Notably, compounds C7, C8, C10, and C14 exhibit excellent superimposition with the benchmark allosteric inhibitor JBJ-09-063, underscoring their robust activity profiles and potential to overcome ATP-site mediated resistance. By bridging both the ATP and allosteric sites, these molecules offer a novel dual-targeting approach to counteract the heterogeneity of resistance mechanisms. Overall, the gathered data support the promise of allosteric modulators as a next-generation therapeutic strategy in EGFR-mutant NSCLC, and a 3-Point pharmacophoric framework is presented to guide future drug design aimed at maximising potency while limiting toxicity.
Colony-stimulating factor-1 receptor (CSF-1R) is a class III receptor tyrosine kinase that regulates monocyte/macrophage lineage cells, including microglia, and has emerged as an attractive target for neuroinflammation-associated neurodegenerative diseases. Inspired by the clinical relevance of dual CSF-1R/c-Kit inhibition and building upon our previously reported 5-methylisoxazole-based lead scaffold, we designed and synthesized a new series of 2-amino-oxazole-based inhibitors by replacing the original 5-methylisoxazole hinge-binding motif with a 2-amino-oxazole core, thereby introducing an additional hydrogen-bond donor. Structure-activity relationship studies revealed that CSF-1R/c-Kit inhibitory activity was strongly influenced by N-substitution, amide bond directionality, and the spatial arrangement of basic amine-containing R groups. Notably, modification of the terminal aryl substitution pattern from 1,3,5 to 1,3,4 enabled improved positioning of pendant amines and afforded several low-nanomolar CSF-1R/c-Kit inhibitors. Integrated biochemical, cellular, kinome, and in vitro ADME profiling identified 12l and 11o as the most promising lead candidates. In SIM-A9 microglial cells, both compounds suppressed CSF-1-induced ERK phosphorylation, a downstream readout of CSF-1R signaling. Compound 12l showed potent dual CSF-1R/c-Kit inhibition, suppression of CSF-1-induced ERK phosphorylation, favorable microsomal and plasma stability, high BBB-PAMPA permeability, and a cleaner kinome selectivity profile. Compound 11o exhibited particularly strong c-Kit inhibition, suppression of CSF-1-induced ERK phosphorylation in SIM-A9 cells, and favorable ADME properties. These findings identify 12l and 11o as promising dual CSF-1R/c-Kit inhibitor leads for further development toward neuroinflammation-associated neurodegenerative diseases.
The rapid emergence of drug-resistant influenza A virus (IAV) strains has severely limited the efficacy of current antiviral therapies, highlighting an urgent need for novel agents with distinct mechanisms of action. In this study, a series of 2-aminoquinoline derivatives were synthesized via a trimethylsilyl trifluoromethanesulfonate (TMSOTf) -catalyzed annulation strategy. Evaluation of their anti-influenza virus activity revealed that derivative 3g exhibited potent antiviral efficacy, low cytotoxicity, and a high selectivity index(SI), making it the most promising candidate in this series. In vitro investigations revealed that 3g primarily acted during the early-to-mid stages of viral replication, significantly suppressing the transcription and translation of viral nucleoprotein (NP) and matrix protein 2 (M2), thereby effectively blocking viral replication and protein synthesis. Furthermore, 3g inhibited virus-induced apoptosis, reduced excessive production of reactive oxygen species (ROS) and nitric oxide (NO) triggered by viral infection, and markedly attenuated cytokine storm responses by suppressing the retinoic acid-inducible gene I (RIG-I)/Toll-like receptor 3 (TLR3)-mediated signaling pathways. In vivo experiments confirmed that 3g significantly reduced viral loads in the lungs of infected mice, alleviated pulmonary histopathological damage, and downregulated inflammatory factor levels, while exhibiting good biosafety. Collectively, these results position derivative 3g as a promising compound for the development of novel anti-influenza therapies.
Senescence is a risk factor for chronic diseases, making anti-aging interventions a promising strategy for geriatric conditions. While a non-antibacterial derivative C1 of enrofloxacin has been proposed to extend lifespan in Caenorhabditis elegans (C. elegans), its unresolved cytotoxicity in healthy mammalian cells limits its combinatory potential and safety as an anti-aging agent. With the aim of preserving anti-aging activity while enhancing safety, we here performed structural optimization of C1 and created 37 derivatives. Among them, C36, which derived from introducing an isopropoxy group at the R7 position, exhibited the most potent lifespan extending effect (11.49%) in C. elegans with low cytotoxicity (IC50 > 100 μM) in two commonly used aging relevant mammalian cell lines. In a mouse model with doxorubicin induced senescence, C36 treatment attenuated the senescence associated secretory phenotype (SASP), mitigated cell cycle arrest, and significantly lowered aging markers in kidney tissue. Given the central role of cellular senescence and SASP in the progression of chronic kidney disease (CKD), we evaluated C36 in mice with kidney failure. The results showed that C36 effectively reduced the level of SASP and thus alleviated senescence of the diseased kidney through a senomorphic approach. In comparison to the model group, C36 significantly improved renal function, reduced renal fibrosis by approximately 50%, and decreased the renal expression of the senescence-associated markers p21, p16, and p53. These findings imply that C36 could have a role in modulating organismal senescence with potential implications for CKD, and offer a perspective on drug repurposing and secondary development for age-related diseases.
The global rise of methicillin-resistant Staphylococcus aureus (MRSA) has highlighted the urgent need for alternative therapeutic strategies beyond conventional bactericidal antibiotics. Targeting bacterial virulence rather than viability represents a promising approach to mitigate selective pressure and delay resistance development. Sortase A (SrtA), a membrane-associated transpeptidase responsible for anchoring virulence-associated surface proteins, is an attractive anti-virulence target due to its non-essential role in bacterial survival. Here, we report a machine learning-guided strategy for the discovery of novel covalent SrtA inhibitors based on a 1,2-benzoselenazol-3-one (BSEA) scaffold featuring a tunable electrophilic Se-N bond. A scaffold-aware classification model with a Tanimoto similarity constraint trained on 529 SrtA inhibitors enabled prospective virtual screening of over 35,000 BSEA and BTA derivatives, leading to a high hit rate of 89% upon experimental validation. Representative compounds exhibited submicromolar SrtA inhibition (IC50 = 0.84-1.04 μM) while showing minimal effects on bacterial growth (MIC = 8-32 μM), indicating effective functional decoupling of virulence and viability. Mechanistic studies demonstrated time-dependent irreversible inhibition kinetics, supported by jump dilution assays and Nano-LC-MS/MS identification of covalent modification at the catalytic residue Cys184. These inhibitors effectively disrupted MRSA biofilm formation at sub-inhibitory concentrations and significantly improved host survival in a Galleria mellonella infection model. Collectively, this study establishes a data-driven framework integrating machine learning and covalent chemistry for anti-virulence drug discovery and provides promising lead compounds targeting SrtA to combat MRSA infections.
Fluoroquinolones are broad-spectrum antibacterials that exert their effects by inhibiting DNA gyrase and topoisomerase IV, enzymes crucial for bacterial DNA replication. Here, we report the synthesis of 60 novel ciprofloxacin-amino acid derivatives, designed to inhibit multiple bacterial targets by the so-called polypharmacology approach. Some of the synthesized compounds retained or improved the antibacterial potency against Gram-positive, Gram-negative, and mycobacterial species. Notably, some derivatives demonstrated promising activity (MIC <10 μM) against multidrug-resistant strains. The most active derivatives were selected for in silico, in vitro, and in vivo mechanistic studies. Molecular modeling, enzyme assay, and phenotypic analysis supported the polypharmacological mode of action. These findings indicate inhibition of DNA gyrase, topoisomerase IV and reduced off-target potential on human topoisomerase II, along with engagement of LpxC and urease as supportive targets. Interference with bacterial cell division and transient membrane disruption in Gram-positive bacteria and aberrant penicillin binding protein activity and possible effects on the outer membrane in Gram-negative bacteria may additionally contribute to the observed antibacterial activity. Compounds 10b and 12b showed the most potent antibacterial activity, with MIC values ranging from 0.2 to 5.47 μM against the evaluated strains. Cytotoxicity studies further revealed favorable selectivity, with SI values of 10-25. Overall, these findings underscore new ciprofloxacin derivatives as promising multi-target antimicrobial agents with potential to combat multidrug-resistant pathogens.
STING, a central component of the cGAS-STING innate immune signaling pathway, is implicated in various autoimmune and inflammatory disorders when aberrantly activated. In this study, an L-configured homoproline derivative Z55 was obtained through structural optimization of the natural product resibufogenin (RBG), which exhibited approximately threefold greater cellular inhibitory activity against STING than RBG (IC50 = 0.40 ± 0.04 μM for Z55 vs. 1.42 ± 0.11 μM for RBG), and maintained favorable in vitro safety. Surface plasmon resonance (SPR) analysis confirmed high-affinity binding of Z55 to hSTING (KD = 2.31 μM), and a cellular thermal shift assay (CETSA) further demonstrated that Z55 directly engages endogenous STING in living cells, with a thermal stabilization of 4.31 ± 0.7 °C. Mechanistic studies, including DTT stability and SPR reversibility assays, support a non covalent interaction mode, while molecular docking provided structural insight into the binding interface. Mechanistically, Z55 inhibited STING phosphorylation and downstream activation of p-TBK1 and p-IRF3, leading to decreased levels of key inflammatory cytokines (IL-1β, IL-6, and TNF-α) in both colon tissue and serum of mice with ulcerative colitis. Importantly, this series of compounds exhibited a marked chiral-toxicity separation, with the L-configuration identified as the optimal pharmacophore for both efficacy and safety. Collectively, these findings highlight Z55 as a promising STING-targeting lead candidate for the treatment of inflammatory diseases.
p21-activated kinase 4 (PAK4), a Group II PAK family member, is a therapeutically relevant candidate target in cancer, metabolic disease, and tissue injury. However, translation of PAK4 biology into drug candidates has been constrained by the conserved ATP-binding architecture of PAK isoforms, unfavorable pharmacokinetic profiles, and suboptimal clinical efficacy. We summarize the evolution of ATP-competitive Type I inhibitors, Type I½ back-pocket inhibitors, allosteric modulators, and PROTAC degraders, and compare representative compounds using potency, isoform selectivity, cellular activity, oral bioavailability, and development status. Particular emphasis is placed on structural determinants of selectivity, including the αC-helix-dependent hydrophobic back pocket, the inward Asp444/Asp458 floor pocket arrangement, and peripheral microenvironment differences that distinguish PAK4 from Group I PAKs. We also summarize the potential ADMET liabilities-such as pronounced efflux, metabolic instability, and poor oral bioavailability-that may arise from structural modifications aimed at enhancing PAK4 selectivity, and discuss rational optimization strategies to navigate these inherent barriers. Finally, we discuss clinical lessons from PF-3758309 and KPT-9274/padnarsertib and highlight how allosteric inhibitors and PROTAC degraders may help address limitations of conventional ATP-site inhibitors.
Sulfonylureas (SUs) have been used in the treatment of type 2 diabetes since the 1950s, yet growing evidence shows that many members of this class also exert biologically relevant off-target effects that may be exploited in oncology and other therapeutic contexts. This review provides a structured overview of the literature from 1956 to 2025, integrating preclinical studies, clinical and epidemiological data, pharmacovigilance signals, and patent activity. To facilitate comparison across compounds, the available evidence is organized into drug-specific mechanistic maps rather than treated as a uniform class effect. Across the literature, SUs have been linked to modulation of KATP channels, ABC transporters involved in multidrug resistance, gap-junction communication, redox balance, mitochondrial function, inflammatory signaling, and DNA damage-related pathways. However, these activities differ markedly between individual agents. Glibenclamide emerges primarily as a chemosensitizing and transporter-modulating compound, gliclazide as a drug with antioxidant, anti-inflammatory, and DNA-protective properties, glimepiride as a promising synergistic agent with additional AKR1C3-inhibitory activity, tolbutamide as a modulator of gap-junction signaling and mitochondrial stability, and chlorpropamide derivatives as ALDH-targeting chemosensitizers. At the same time, the review highlights major translational constraints, including weak baseline cytotoxicity for most SUs, frequent exposure mismatches between experimental and clinical settings, heterogeneous safety profiles, photoreactivity, and limited commercial incentives for development, while also outlining practical strategies to address these limitations. Overall, SUs should not be viewed as a single repurposing candidate, but as a chemically related set of drugs that require indication-specific and compound-specific selection for future oncology applications.
Thiosemicarbazone ligands and their transition-metal complexes have attracted considerable attention in medicinal inorganic chemistry due to their versatile coordination modes and broad pharmacological potential. This review presents recent studies (2020-2025) on the comparative evaluation of the biological applications of Zn(II) and Cd(II) thiosemicarbazone complexes incorporating N,S-, N,N,S-, and N,S,O-donor ligand systems. The compiled studies demonstrate that metal coordination considerably enhances antimicrobial, anticancer, antioxidant, and anti-inflammatory activities compared to free ligands, primarily due to chelation-induced lipophilicity, improved cellular uptake, and stronger biomolecular interactions. Comparative structure-activity relationship analysis indicates that biological activity is strongly influenced by metal ion identity, ligand denticity, donor atom set, and coordination geometry. In particular, tridentate N,N,S- and N,S,O-donor systems generally exhibit superior biological activity compared to bidentate N,S analogues. Furthermore, differences in biological responses between Zn(II) and Cd(II) complexes highlight the important role of metal-ion characteristics in determining pharmacological behaviour. In general, Zn(II) and Cd(II) thiosemicarbazone complexes emerge as promising candidates for multifunctional biological applications and provide valuable insights for the rational design of next-generation metal-based therapeutic agents. However, studies on the antioxidant and anti-inflammatory activities of these complexes remain comparatively limited relative to antimicrobial and anticancer investigations, highlighting the need for further systematic exploration of these biological properties.
Cerebral ischemia-reperfusion (I/R) injury remains a major therapeutic challenge due to excessive mitochondrial oxidative stress and limited neuroprotective interventions. Although idebenone exhibits mitochondrial protective activity, its efficacy is strongly dependent on NAD(P)H:quinone oxidoreductase 1 (NQO1), whose expression is often heterogeneous and insufficient in neuronal tissues. To address this limitation, we designed and synthesized a series of novel idebenone-rhein conjugates (4a-4f) that integrate the mitochondrial electron-transfer capability of idebenone with the antioxidant and NQO1-inducing properties of rhein. Among these derivatives, compound 4c demonstrated the most potent neuroprotective activity against glutamate-induced excitotoxicity in HT22 hippocampal neurons, exhibiting an EC50 of 0.75 μM, markedly superior to idebenone (EC50 = 3.11 μM). Molecular docking predicted a favorable docking score of 4c toward NQO1 (-10.8 kcal/mol), supporting a possible ligand-NQO1 interaction. Mechanistic investigations showed that 4c attenuated mitochondrial oxidative stress by reducing mitochondrial reactive oxygen species, restoring ATP production, preserving mitochondrial membrane potential, and enhancing mitochondrial integrity. Notably, lentiviral NQO1 knockdown experiments demonstrated that 4c retained substantial neuroprotective efficacy under reduced NQO1 expression, unlike idebenone. In a mouse middle cerebral artery occlusion/reperfusion (MCAO/R) model, intraperitoneal administration of 4c significantly reduced infarct volume, improved neurological outcomes, increased hippocampal NQO1 expression. In addition, 4c showed favorable in vitro PAMPA-BBB permeability, and H&E staining of major organs showed no obvious short-term histopathological abnormalities under the present experimental conditions. Collectively, these findings identify 4c as a promising idebenone-rhein conjugate with neuroprotective activity, which may involve NQO1 expression modulation and additional mitochondrial protective mechanisms, highlighting its potential value for further investigation in ischemic stroke and other oxidative stress-related neurological disorders.
The frequent emergence of novel RNA viruses and the rapid development of viral resistance highlight the urgent need for new antiviral therapies. In this study, we employed an integrated computational pipeline combining shape-based models, machine-learning (ML)-based models, and hotspot analysis to identify novel human dihydroorotate dehydrogenase (HsDHODH) inhibitors. A virtual screening (VS) campaign of the H3D chemical library identified H3D-002856 as the primary hit (IC50 = 2.92 ± 0.07 μM), which subsequently guided a similarity-based hit expansion (Tanimoto coefficient≥0.7) of 17 structural analogs. This two-stage workflow collectively yielded four anthranilate-based compounds H3D-002856, H3D-003181, H3D-001915, and H3D-003186 with enzymatic IC50 values below 5.0 μM. Our crystal structures of HsDHODH in complex with H3D-002856, H3D-003181, and H3D-003186 confirmed the predicted binding modes and revealed a conserved interaction pattern across the series. The four most potent compounds successfully inhibited SARS-CoV-2 replication in vitro in Calu-3 cells, demonstrating EC50 values ranging from 1.3 to 3.9 μM, and a favorable selectivity index, supported by minimal cytotoxicity (CC50 values ≥ 100 μM). These findings highlight the value of integrated computational-experimental workflows in the discovery of HsDHODH inhibitors, establishing this scaffold as a viable starting point for further development with potential applicability against SARS-CoV-2. Furthermore, by using accessible, shape-based and low-code ML-based modeling platforms, this workflow provides a reproducible and practical template that can be readily adopted by medicinal chemists to accelerate lead identification.