Search Results (244)

Feline Infectious Peritonitis (FIP) has been transformed from a fatal disease to a treatable condition following the introduction of GS-441524, a nucleoside analogue targeting feline coronavirus replication. However, the widespread use of unregulated compounded formulations and the absence of validated analytical tools for therapeutic drug monitoring (TDM) represent critical gaps in clinical FIP management. This study describes the development and full ICH M10-compliant validation of a high-throughput LC-MS/MS method for the quantification of GS-441524 in feline serum, incorporating an automated protein precipitation protocol and a PBS-BSA surrogate matrix in accordance with 3Rs principles. The method met all acceptance criteria across validated parameters, including linearity (0.1–50 µg/mL), accuracy (bias within ±12.5%), precision (CV ≤ 10.9%), selectivity, extraction recovery (87.5–107.9%), and stability under clinically relevant storage conditions. Matrix equivalence between PBS-BSA and authentic feline serum was confirmed, enabling routine calibration without animal-derived materials. The validated method was applied to clinical TDM in cats undergoing GS-441524 treatment for FIP, providing preliminary evidence of inter-individual pharmacokinetic variability. The compounded formulations administered to the TDM cohort were independently verified by LC-MS/MS, confirming drug content within ±15% of labelled claims and excluding pharmaceutical quality as a confounding factor in the interpretation of serum drug concentrations. Full article

A series of nucleolipid derivatives based on adenosine and 1,N⁶-ethenoadenosine was synthesized, and their cytotoxicity was evaluated in glioma and glioblastoma cell models. Twenty O-2′,3′-ketalized nucleolipid derivatives were prepared as symmetric and asymmetric adenosine analogs. The lipophilicity was determined using the octanol/water partition method, yielding logP_OW values from −0.04 to 4.08. First, cytotoxicity was screened in rat/human glioma cell lines (BT4Ca/GOS-3) using a PrestoBlue™ viability assay, with 5-fluorouridine (5-FUrd) as the reference compound. Selected derivatives with the highest cytotoxicity were evaluated in human glioblastoma cell lines U87 and U251, and their efficacy was compared with the chemotherapeutic agent temozolomide (TMZ). PMA-differentiated human THP-1 macrophages were used to assess cytotoxic side effects in human immune-related cells. Several derivatives induced 90–100% cytotoxicity at 50 µM after 48 h, with cytotoxicity increasing with alkyl chain length and reaching a maximum for derivatives bearing medium-length chains (C₁₅–C₁₇). In contrast, shorter or longer chains caused reduced activity. Cytotoxicity was independent of symmetric or asymmetric ketal configuration, while 1,N⁶-ethenoadenosine ketal derivatives displayed higher activity than the corresponding adenosine ketals. These novel derivatives indicate that lipophilicity and alkyl chain length are responsible for the cytotoxic effect in glioma and glioblastoma, and that they are more effective than 5-FUrd and TMZ. Full article

Marine biofouling remains a major challenge for maritime industries, affecting submerged structures and vessels worldwide. The long-standing reliance on biocidal coatings, together with their documented environmental impacts, has led to increasingly restrictive regulations and an urgent demand for environmentally compatible antifouling (AF) solutions. This study evaluates the AF potential and toxicological profile of two nucleoside analogues, hypoxanthine arabinoside (1′) and 2′-deoxyinosine (2′), selected based on the previously reported non-lethal AF activity of the naturally occurring nucleosides adenosine and 2′-deoxyadenosine from cyanobacteria. Both analogues inhibited the growth of Navicula sp. by approximately 60% without inducing mortality and significantly reduced settlement of Mytilus galloprovincialis plantigrades, with EC₅₀ values of 5.50 µM (1′) and 8.54 µM (2′), and no lethality detected (LC₅₀ > 200 µM). At near-EC₅₀ concentrations, both compounds increased acetylcholinesterase and tyrosinase activities, supported by molecular docking results, suggesting involvement of neurotransmission- and byssal formation-related pathways. Proteomic analysis revealed compound-specific molecular responses. No lethal effects were observed in non-target organisms (LC₅₀ > 32 µM for A. amphitrite and LC₅₀ > 50 µM for A. salina), and environmental fate modelling predicted low bioaccumulation and rapid degradation. Overall, substitution of the amino group by a carbonyl group preserved AF efficacy without increasing toxicity, highlighting nucleosides as promising low-toxicity AF agents. Full article

Feline infectious peritonitis (FIP) is a disease arising as a result of feline coronavirus infection. It used to be regarded a fatal disease, with euthanasia commonly recommended following diagnosis due to its very poor prognosis. The availability of effective antiviral therapies, particularly nucleoside analogues such as oral GS-441524, has fundamentally changed the outlook for cats with FIP. FIP is now a treatable and frequently curable disease. In these revised guidelines, the European Advisory Board on Cat Diseases (ABCD) presents an update on the treatment of FIP, incorporating the findings of new studies including the range of available treatments (such as GS-441524, remdesivir and molnupiravir (EIDD-2801) and its active metabolite EIDD-1931), which varies globally, as well as suggestions for monitoring and prognostic indicators. Tables are used to present easy-to-find information on antiviral and supportive treatments for cats with FIP. GS-441524 is the most extensively studied antiviral for FIP with treatment success rates often exceeding 90%. Remdesivir is primarily reserved as an injectable antiviral for severely affected cats unable to tolerate oral medication; it is usually replaced by oral medication as soon as, and when, possible. Although 84-day treatment courses have historically been used, emerging evidence suggests that shorter regimens of 42 days can be equally effective. Full article

West Nile Virus (WNV) is becoming a significant and enduring public health menace in Europe, propelled by climate changes and accelerated population aging. Most infections are asymptomatic but older adults are more prone to develop neuroinvasive disease, which is characterized by high morbidity and mortality, as well as long-term neurological disturbances and disability. To date, there is still no licensed human vaccine or specific antiviral treatment, and management is mostly supportive. This review brings together the most recent information about WNV epidemiology, pathogenesis, and clinical manifestations, with a special focus on older people in Europe. We critically analyze current and novel pharmaceutical strategies, encompassing drug repurposing, nucleoside analogues, interferon-based therapies, peptides, monoclonal antibodies, and host-directed agents, emphasizing their therapeutic potential alongside the challenges presented by age-related pharmacokinetic and immunological alterations. We also discuss some important gaps in the current evidence base, such as the frequent exclusion of older adults from clinical studies and the lack of a coordinated clinical trial infrastructure that can be quickly activated during seasonal outbreaks. Lastly, we suggest a framework that combines systematic antiviral screening with the creation of a Europe-wide network of clinical trial readiness that is built into current One Health surveillance systems. Full article

A detailed mathematical model has been developed for the dynamics of hepatitis B virus (HBV) infection in a single cell. It provides a platform for a better quantitative understanding of the biochemical kinetics of the HBV lifecycle. The model is used to study the sensitivity of virus growth, providing a clear ranking of intracellular virus replication processes with respect to their contribution to net viral production. The stochastic formulation of the model enables the quantification of the variability characteristics in viral production, the probability of productive infection and the secretion of protein- and genome-deficient viral particles. An essential difference in infection efficiency between deterministic and stochastic models has been revealed. For example, in the case of $\mathrm{MOI}=1$, the mean value of the total number of mature virions released during the lifecycle of the infection in the stochastic model is 1.06, whereas, in the deterministic model, its value is less than one thousandth and thus close to 0. The model is also used to quantitatively predict the effect of combinations of direct-acting antivirals, such as small interfering RNAs, capsid inhibitors and nucleoside analogues. The model shows that the inhibitory effect of siRNA on viral production is approximately two orders of magnitude higher than that of nucleoside analogues and capsid inhibitors. Full article

KRAS is one of the most frequently mutated genes in all human cancers, and its oncogenic mutation hotspots are glycine 12 (G12), glycine 13 (G13), glutamine 61 (Q61) and alanine 146 (A146). Among these hotspot mutations, A146 substitution mutations (A146X) occur relatively infrequently, except for haematopoietic and lymphoid cancers, suggesting that A146X causes intrinsically distinct KRAS signalling compared to other KRAS oncogenic alleles. However, due to the absence of model A146X cell lines derived from haematopoietic sources, the cellular mechanisms that cause the differences between KRAS.A146X and other common KRAS mutants, such as KRAS.G12X, remain largely unexplored. In this study, we developed a set of isogenic model haematopoietic cell lines expressing KRAS.A146T, KRAS.G12V and KRAS.G12G (non-mutated) from the endogenous locus by genetically modifying the human lymphoblastoid TK6 cell line. We found that TK6 cells carrying KRAS^A146T/+ or KRAS^G12V/+ exhibited increased replication stress compared to KRAS wild-type cells. Strikingly, KRAS^A146T/+ cells strongly rely on PrimPol for maintaining cellular survival upon replication stress. In contrast, KRAS^G12V/+ cells exhibited hypersensitivity to inhibitors for the ATR-Chk1 checkpoint signalling axis and to nucleoside analogues commonly used to treat cancers and viral infections. Our findings demonstrate that the endogenously expressed oncogenic KRAS mutations exacerbate the replication stress and reveal KRAS allele-specific replication phenotypes, facilitating the development of effective chemotherapies tailored to specific oncogenic KRAS mutation alleles and types of cancer. Moreover, our study offers valuable model cell lines for investigating mechanisms underlying replication vulnerability in cancers harbouring oncogenic KRAS mutations. Full article

Flammulina filiformis is a widely cultivated edible mushroom valued for its taste and nutrition. However, its stipe often develops a fibrous and stringy texture that unpleasantly lodges between teeth during chewing. Texture analysis confirmed a distinct toughness gradient, with the upper stipe being more brittle and less tough than the lower part. UHPLC-MS/MS-based metabolomics of these regions identified 953 metabolites, predominantly spanning lipids and lipid-like molecules, organic acids and derivatives, and nucleosides, nucleotides, and analogues. Comparative analysis revealed that the tender upper stipe was characterized by a widespread downregulation of primary metabolites, including severe depletion of key signaling molecules (cAMP, cGMP) and amino acids such as L-tryptophan. In contrast, the tough lower stipe was enriched with metabolites indicative of an oxidative environment, notably a broad spectrum of oxidized lipids and phenolic compounds. KEGG pathway analysis attributed this dichotomy to distinct metabolic programs. While the upper stipe exhibited downregulation in tryptophan and purine metabolism, the lower stipe was enriched for pathways associated with redox homeostasis and lipid peroxidation, including glutathione metabolism and lipid peroxidation. The co-accumulation of oxidized lipids and phenolics suggests a potential mechanism for oxidation-driven tissue fortification. This study reveals a spatially programmed metabolic basis for the textural differentiation in F. filiformis stipes, providing a framework for understanding tissue development and highlighting potential regulatory targets for breeding varieties with improved eating quality. Full article

Herpes simplex viruses (HSV-1 and HSV-2) are highly prevalent human pathogens that establish lifelong latency in sensory neurons, posing a persistent challenge to global public health. Their clinical manifestations range from mild, self-limiting orolabial lesions to severe, life-threatening conditions such as disseminated neonatal infections, focal encephalitis, and herpetic stromal keratitis, which can lead to irreversible corneal blindness. Beyond direct pathology, HSV-mediated genital ulcerative disease (GUD) significantly enhances mucosal susceptibility to HIV-1 and other sexually transmitted infections, amplifying co-infection risk and disease burden. Despite decades of clinical reliance on nucleoside analogues such as acyclovir, the therapeutic landscape has stagnated with rising antiviral resistance, toxicity associated with prolonged use, and the complete inability of current drugs to eliminate latency or prevent reactivation continue to undermine effective disease control. These persistent gaps underscore an urgent need for next-generation antivirals that operate through fundamentally new mechanisms. Marine ecosystems, the planet’s most chemically diverse environments, are providing an expanding repertoire of antiviral compounds with significant therapeutic promise. Recent discoveries reveal that marine-derived polysaccharides, sulfated glycans, peptides, alkaloids, and microbial metabolites exhibit remarkably potent and multi-targeted anti-HSV activities, disrupting viral attachment, fusion, replication, and egress, while also reshaping host antiviral immunity. Together, these agents showcase mechanisms and scaffolds entirely distinct from existing therapeutics. This review integrates emerging evidence on structural diversity, mechanistic breadth, and translational promise of marine natural products with anti-HSV activity. Collectively, these advances position marine-derived compounds as powerful, untapped scaffolds capable of reshaping the future of HSV therapeutics. Full article

Usutu virus (USUV) is an emerging arbovirus recently associated with outbreaks in Western Europe. Although USUV is typically associated with asymptomatic or nonspecific febrile disease, the occurrence of severe neuroinvasive forms of disease has raised concern. There is currently no antiviral treatment available for USUV infection; therefore, we sought to investigate the protective effects of the nucleoside analogue 7DMA against USUV. Adding to 7DMA’s activity against USUV in vitro reported by us and others, we found that 7DMA inhibits USUV replication at multiple stages in mammalian cell lines Vero CCL81 and SH-SY5Y. In vivo testing of 7DMA using the susceptible IFNAR^-/- mouse model indicated that 7DMA treatment significantly reduced USUV viremia and viral load in tissues and prolonged mice survival. The characterization of the protective effects of 7DMA indicated that treatment also altered immunological aspects of disease development, further increasing the expression of mediators such as CXCL10, IL-15, and IFN-γ, and increasing neutrophil recruitment to target organs. We did not observe significant tissue damage or pathology in USUV-infected mouse brains, suggesting that systemic infection and disease are the major components leading to mortality in this model. We conclude that 7DMA exerts protective effects against USUV infection in the IFNAR^-/- model. Full article

Background/Objectives: Fibroblast growth factor receptors (FGFRs) are frequently dysregulated in diverse cancers and represent important therapeutic targets. Here, we report the design and synthesis of a novel nucleoside-based scaffold which enables irreversible pan-FGFR inhibition as a potential anticancer strategy. Methods: A series of nucleoside analogues was synthesized and assessed through structure–activity relationship studies. Structural analyses, including X-ray co-crystallography and molecular dynamics simulations, were performed to define key determinants of potency and selectivity. Biochemical assays against FGFR1–4 proteins, cellular antiproliferative assays in HCT116 (FGFR1 amplification) and RT4 (FGFR3-TACC3) models, metabolic stability evaluations and covalent bonding confirmation were conducted to characterize representative compounds. Results: SAR studies revealed that fused aromatic substituents and 4′-thio ribose enhanced FGFR potency, whereas enantiomeric inversion of ribose reduced activity. X-ray co-crystallography further demonstrated that two hydroxyl groups form a key water-mediated hydrogen bond network, uniquely stabilizing the ligand and enhancing potency of inhibitors compared to reference compounds. The 7-methoxy-5-methylbenzo[b]thiophene scaffold and ribose moiety emerged as critical features. Compounds 13f, 19e, and 22f demonstrated potent inhibition of FGFR1-4 and dose-dependent suppression of FGFR1-mediated signaling, with strong antiproliferative activity in both FGFR-driven and wild-type cancer models. Compound 22f showed efficient irreversible covalent engagement of FGFRs, confirmed at the protein and cellular levels, and exhibited improved metabolic stability. Conclusions: Nucleoside analogues represent a privileged scaffold for covalent pan-FGFR inhibition. The findings highlight their potential as promising therapeutic candidates for targeting FGFR-driven malignancies. Future efforts will focus on further improving stability and optimizing physicochemical properties to advance these compounds toward translational development. Full article

Nucleoside analogues are used as drugs and as labels in laboratory-based research. However, the effect of different nucleoside analogue mechanism(s) on cell sensitivity or mutagenesis is unclear. This is particularly important in cancer treatments where checkpoint proteins and DNA damage factors are often mutated. We tested six nucleoside analogues in fission yeast, Schizosaccharomyces pombe. We found that the mutations in the DNA replication checkpoint cause unique sensitivity profiles towards chemotherapeutic nucleoside analogues (gemcitabine, 5-fluorouracil, cytarabine) and the non-clinical analogue bromodeoxyuridine. Antiretroviral compounds, zidovudine and lamivudine, did not alter cell growth. We compared half-maximal inhibitory concentration (IC50) doses between checkpoint deficient yeast strains, examining culture growth and DNA mis-segregation. Intriguingly, gemcitabine and bromodeoxyuridine doses above the IC50 promoted better growth. Above each compound’s IC50 dose we saw that cells were insensitive to nucleoside analogue re-exposure, particularly in DNA replication checkpoint mutants (cds1∆, rad3∆). Thus, pairing nucleoside analogue use with personal genomics may inform drug choice, dose, and schedule. Finally, these data indicate that resistance may be predictable, informing clinical strategy. Full article

The nucleoside analogue GS-441524 is a common treatment for cats with feline infectious peritonitis (FIP). In a previous study, 40 cats with FIP with effusion were treated with 15 mg/kg GS-441524 orally once daily for either 42 days or 84 days, and a 42-day treatment was as effective as the earlier recommended 84-day treatment. The aim of the present study was to describe unexpected clinical and laboratory observations occurring during and after treatment (within one year) in these cats and to compare them regarding the different treatment durations. Thirty-eight cats recovered rapidly during treatment, two cats had to be euthanized, and one cat was lost to follow-up. During treatment, 25 cats developed diarrhea. Lymphocytosis occurred in 26/40 cats during treatment, eosinophilia in 25/40 during treatment, increased alanine aminotransferase activity in 22/40, alkaline phosphatase activity in 7/40, and symmetric dimethylarginine levels in 25/40. These unexpected observations occurred equally in both treatment duration groups, but statistically significantly more cats developed lymphocytosis and eosinophilia when treated for 84 days. Although most of the unexpected observations during GS-441524 treatment improved or disappeared after treatment termination, these conditions have to be monitored, and treatment should not be given for longer than necessary. Full article

The synthesis of a new acyclic and cyclic series of D-Ala-AMP analogues was reported. Chemical modifications were introduced on the carbohydrate, the sulfamate linker, and/or the amino-acid N-terminal moiety in order to increase in vivo stability and cell permeability. These new compounds were evaluated in vitro as DltA inhibitors and also in vivo as adjuvant antibiotics to re-sensitize methicillin-resistant Staphylococcus aureus. Indeed, we showed that seven nucleosides containing either a fluorine atom, an azido group, a difluorophosphonylated allylic ether moiety onto the 2′-position, or a sulfamate and a triazole as the sulfamate linker had moderate to excellent IC₅₀ values. Among all these new DltA inhibitors, two molecules functionalized by the fluorinated ether or the sulfamide linker were able to efficiently re-sensitize MRSA to imipenem. Quantification of D-alanyl esters confirmed that these two compounds reduced the level of bacterial cell wall D-alanyl residues by 50% and 80%. Full article

The anticancer activity of 3′-deoxyadenosine (Cordycepin, or dCor) is known to be linked to the inhibition of the MAPK/ERK signalling and Hedgehog pathways, as well as the termination of primer elongation by primase in DNA lagging-strand synthesis. In this study, the electronic properties of dCor, 7,8-dihydro-8-oxo-3′-deoxyadenosine (^OXOdCor), and 8-hydroxy-3′deoxyadenosie (^HOdCor), together with their spin densities, charge distributions, and global reactive descriptors, have been taken into consideration at the M06-2x/6-31++G** level of theory in the aqueous phase. It was found that dCor predominantly adopts a 3′-endo,anti conformation, while ^OXOdCor and ^HOdCor adopt a 2′-endo,syn conformation. Also, the keto form of oxidised dCor was found to be energetically preferred to its enolic form. The adiabatic ionisation potentials (AIPs) were noted as follows (in eV): 6.29 for dCor, 6.21 for ^OXOdCor, and 6.17 for ^HOdCor. The lowest adiabatic electron affinity among all the discussed adenine nucleosides analogues was assigned for ^OXOdCor at 1.12 eV. A thorough analysis of the spin density distribution of the adiabatic radical cation reveals that it has a higher accumulation at N6 > C5 > C8 > 3 of dCor, C5 > N6 > N7 > O8 of ^OXOdCor, and N6 > C5 > C8 > C2 of ^HOdCor. The results suggest that Cordycepin is more easily converted to ^OXOdCor and ^HOdCor than canonical adenine nucleosides. Much like typical drugs, after its administration and release, Cordycepin is exposed to various physiological factors and can be exposed to ionisation radiation during combined therapy. These factors can influence the therapeutic potential of Cordycepin. Therefore, further studies on its stability are of utmost importance. Full article