Vidarabine as a novel antifungal agent against Candida albicans: insights on mechanism of action.

Around 1.5 million mortality cases due to fungal infection are reported annually, posing a massive threat to global health. However, the effectiveness of current antifungal therapies in the treatment of invasive fungal infections is limited. Repurposing existing antifungal drugs is an advisable alternative approach for enhancing their effectiveness. This study evaluated the antifungal efficacy of the antiviral drug vidarabine against Candida albicans ATCC 90028. Antifungal susceptibility testing was performed by microbroth dilution assay and further processed to find the minimum fungicidal concentration. Investigation on probable mode of vidarabine action against C. albicans was assessed by using the ergosterol reduction assay, reactive oxygen species (ROS) accumulation, nuclear condensation, and apoptosis assay. Results revealed that C. albicans was susceptible to vidarabine action and exhibited minimum inhibitory concentration at 150 µg/ml. At a concentration of 300 µg/ml, vidarabine had fungicidal activity against C. albicans. 300 µg/ml vidarabine-treated C. albicans cells demonstrated 91% reduced ergosterol content. Annexin/FITC/PI assay showed that vidarabine (150 µg/ml) had increased late apoptotic cells up to 31%. As per the fractional inhibitory concentration index, vidarabine had synergistic activity with fluconazole and caspofungin against this fungus. The mechanism underlying fungicidal action of vidarabine was evaluated at the intracellular level, and probably because of increased nuclear condensation, enhanced ROS generation, and cell cycle arrest. In conclusion, this data is the first to report that vidarabine has potential to be used as a repurposed antifungal agent alone or in combination with standard antifungal drugs, and could be a quick and safe addition to existing therapies for treating fungal infections.

Gaining insight into irrational off-label use of vidarabine through analysis of a spontaneous reporting system in China.

WHAT IS KNOWN AND OBJECTIVE: Although superseded by other antiviral agents in many Western countries, vidarabine is still widely used in some countries, including China; hence, the extent and appropriateness of vidarabine prescriptions in children require better characterization. This study examined the rationale, extent, and health risks associated with irrational off-label vidarabine use in China. METHODS: Data used in the study were extracted from a multi-provincial joint adverse drug reactions monitoring platform from 2002 to 2018. Descriptive statistics were used to analyse the characteristics of individual case safety reports (ICSRs) related to vidarabine use. RESULTS AND DISCUSSION: Among 2772 individual ICSRs related to vidarabine, 2223 (80.19%) cases occurred in patients aged 0-9. In all patients, the median age and interquartile range were 2 (0-6). Although most adverse events were mild, five deaths were recorded, all in children below 7 years of age. Paediatric use is the most prominent off-label use of vidarabine. Additionally, several other irrational off-label uses were identified, including 218 (7.86%) cases of overdosing and numerous applications beyond the approved indications, dosages, routes of administration, and solvents. WHAT IS NEW AND CONCLUSION: Data indicate that vidarabine was mainly prescribed for suspected common viral infections in paediatric patients, demonstrating serious inappropriate off-label uses. The problem was further complicated by the lack of sufficient information regarding safety, efficacy, and dosing regimens in children, as well as by several additional risk factors such as inappropriate solvents, routes of administration, and overdose. In the case of children, the physicians' lack of understanding of antiviral activities and compassionate prescriptions were mainly responsible for drug overuse. The health risks associated with the paediatric use of vidarabine in China require greater attention and further investigation.

Citrobacter koseri immobilized on agarose beads for nucleoside synthesis: a potential biocatalyst for preparative applications.

The biocatalyzed synthesis of purine nucleosides and their analogs is a case widely studied due to the high pharmaceutical interest of these compounds, providing the whole-cell biocatalysts, a useful tool for this purpose. Vidarabine and fludarabine are commercial examples of expensive bioactive nucleosides that can be prepared using a microbial transglycosylation approach. Citrobacter koseri whole-cells immobilized on agarose beads proved to be an interesting option to transform this biotransformation in a preparative process. The entrapment matrix provided a useful and resistant multipurpose biocatalyst regarding its stability, mechanical strength, microbial viability and reuse. Immobilized biocatalyst retained the initial activity for up to 1 year storage and after 10 years, the biocatalyst did not show cell leaking and still exhibited residual activity. In addition, the biocatalyst could be reused in batch 68 times keeping up to 50% of the initial biocatalytic activity and for at least 124 h in a continuous process.

An Enzymatic Flow-Based Preparative Route to Vidarabine.

The bi-enzymatic synthesis of the antiviral drug vidarabine (arabinosyladenine, ara-A), catalyzed by uridine phosphorylase from Clostridium perfringens (CpUP) and a purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNP), was re-designed under continuous-flow conditions. Glyoxyl-agarose and EziGTM1 (Opal) were used as immobilization carriers for carrying out this preparative biotransformation. Upon setting-up reaction parameters (substrate concentration and molar ratio, temperature, pressure, residence time), 1 g of vidarabine was obtained in 55% isolated yield and >99% purity by simply running the flow reactor for 1 week and then collecting (by filtration) the nucleoside precipitated out of the exiting flow. Taking into account the substrate specificity of CpUP and AhPNP, the results obtained pave the way to the use of the CpUP/AhPNP-based bioreactor for the preparation of other purine nucleosides.

The use of online heart-cutting high-performance liquid chromatography coupled with linear ion trap mass spectrometry in the identification of impurities in vidarabine monophosphate.

It is difficult to identify unknown impurities in nucleotide analogues by mass spectrometry because mass-spectrometry-incompatible mobile phases need to be used to separate the major ingredient from impurities. In this study, vidarabine monophosphate was selected, and unknown impurities were identified by online heart-cutting two-dimensional high-performance liquid chromatography and linear ion trap mass spectrometry. The one-dimensional reversed-phase column was filled with a mobile phase containing nonvolatile salt. In two-dimensional high-performance liquid chromatography, we used an Acclaim Q1 column with volatile salt, and the detection wavelength was 260 nm. The mass spectrum was scanned in positive- and negative-ion mode. The online heart-cutting and online demineralization technique ensured that the mobile phase was compatible with mass spectrometry; seven impurities were identified by MS2 and MS3 fragments. The mass fragmentation patterns of these impurities were investigated. The two isomers were semiprepared and complemented by nuclear magnetic resonance. The results were further compared with those of normal-phase high-performance liquid chromatography with mass spectrometry. The online heart-cutting two-dimensional high-performance liquid chromatography with mass spectrometry was superior in identifying more impurities. The method solves the problem of incompatibility between the mobile phase and mass spectrometry, so it is suitable for identifying unknown impurities. This method may also be used for investigating impurities in other nucleotide analogues.

Early-onset herpes simplex encephalitis type 1 triggered by COVID-19 disease: A case report.

Coronavirus disease 2019 (COVID-19) causes a systemic inflammatory response and a temporary immunosuppression of hosts. Several reports have showed that reactivation of herpes simplex virus type 1 (HSV-1) is strongly associated with COVID-19. We present a case of a 66-year-old female, who developed HSV-1 encephalitis, showing impaired consciousness and typical MRI findings such as hyperintense lesions in the temporal lobe, insular cortices, bilateral medial frontal lobe on diffusion-weighted imaging, 7 days after the onset of COVID-19 symptoms. The number of cases of encephalitis in patients with COVID-19 is increasing. However, there has been limited reports of HSV-1 encephalitis following COVID-19, especially for cases with an interval of 7 days or less from the onset of COVID-19 symptoms to the onset of HSV-1 encephalitis. Our case highlights the importance of considering HSV-1 encephalitis in the differential when managing a patient with COVID-19-associated neurologic complications, even if it is in the early stages of COVID-19.

Synthesis and Preliminary Evaluation of an ASGPr-Targeted Polycationic ß-Cyclodextrin Carrier for Nucleosides and Nucleotides.

Most antiviral and anticancer nucleosides are prodrugs that require stepwise phosphorylation to their triphosphate nucleotide form for biological activity. Monophosphorylation may be rate-limiting, and the nucleotides may be unstable and poorly internalized by target cells. Effective targeting and delivery systems for nucleoside drugs, including oligonucleotides used in molecular therapeutics, could augment their efficacy. The development of a carrier designed to effect selective transmembrane internalization of nucleotides via the asialoglycoprotein receptor (ASGPr) is now reported. In this work, the polycationic, polygalactosyl drug delivery carrier heptakis[6-amino-6-deoxy-2-O-(3-(1-thio-ß-D-galactopyranosyl)-propyl)]-ß-cyclodextrin hepta-acetate salt (GCyDAc), potentially a bifunctional carrier of (poly)nucleotides, was modeled by molecular docking in silico as an ASGPr-ligand, then synthesized for testing. The antivirals arabinosyl adenine (araA, vidarabine, an early generation antiviral nucleoside), arabinosyl adenine 5'-monophosphate (araAMP), and 12-mer-araAMP (p-araAMP) were selected for individual formulation with GCyDAc to develop this concept. Experimentally, beta cyclodextrin was decorated with seven protonated amino substituents on the primary face, and seven thiogalactose residues on its secondary face. AraA, araAMP, and p-araAMP were individually complexed with GCyDAc and complex formation for each drug was confirmed by differential scanning calorimetry (DSC). Finally, the free drugs and their GCyDAc complexes were evaluated for antiviral activity using ASGPr-expressing HepAD38 cells in cell culture. In this model, araA, araAMP, and p-araAMP showed relative antiviral potencies of 1.0, 1.1, and 1.2, respectively. In comparison, GCyDAc-complexes of araA, araAMP, and p-araAMP were 2.5, 1.3, and 1.2 times more effective than non-complexed araA in suppressing viral DNA production. The antiviral potencies of these complexes were minimally supportive of the hypothesis that ASGPr-targeted, CyD-based charge-association complexation of nucleosides and nucleotides could effectively enhance antiviral efficacy. GCyDAc was non-toxic to mammalian cells in cell culture, as determined using the MTS proliferation assay.

Current Drugs to Treat Infections with Herpes Simplex Viruses-1 and -2.

Herpes simplex viruses-1 and -2 (HSV-1 and -2) are two of the three human alphaherpesviruses that cause infections worldwide. Since both viruses can be acquired in the absence of visible signs and symptoms, yet still result in lifelong infection, it is imperative that we provide interventions to keep them at bay, especially in immunocompromised patients. While numerous experimental vaccines are under consideration, current intervention consists solely of antiviral chemotherapeutic agents. This review explores all of the clinically approved drugs used to prevent the worst sequelae of recurrent outbreaks by these viruses.

SAMHD1 protects cancer cells from various nucleoside-based antimetabolites.

Recently, we demonstrated that sterile α motif and HD domain containing protein 1 (SAMHD1) is a major barrier in acute myelogenous leukemia (AML) cells to the cytotoxicity of cytarabine (ara-C), the most important drug in AML treatment. Ara-C is intracellularly converted by the canonical dNTP synthesis pathway to ara-CTP, which serves as a substrate but not an allosteric activator of SAMHD1. Using an AML mouse model, we show here that wild type but not catalytically inactive SAMHD1 reduces ara-C treatment efficacy in vivo. Expanding the clinically relevant substrates of SAMHD1, we demonstrate that THP-1 CRISPR/Cas9 cells lacking a functional SAMHD1 gene showed increased sensitivity to the antimetabolites nelarabine, fludarabine, decitabine, vidarabine, clofarabine, and trifluridine. Within this Extra View, we discuss and build upon both these and our previously reported findings, and propose SAMHD1 is likely active against a variety of nucleoside analog antimetabolites present in anti-cancer chemotherapies. Thus, SAMHD1 may constitute a promising target to improve a wide range of therapies for both hematological and non-haematological malignancies.

[Bilateral non-arteritic ischemic optic neuropathy during treatment of viral hepatitis C with pegylated interferon and Ribavirin]. / Neuropathie optique ischémique non artéritique bilatérale au cours du traitement de l'hépatite virale C par l'association interféron pégylé et Ribavirine®

INTRODUCTION: Hepatitis C is a serious viral infection, for which the current treatment is based on the combination of pegylated interferon (IFN) and Ribavirin(®). Ophthalmic complications observed with PEG-IFN are infrequent and of variable prognosis. They often include an ischemic retinopathy with typical cotton-wool spots, hemorrhage and retinal edema, and rarely acute non-arteritic anterior ischemic optic neuropathy as illustrated by our report. OBSERVATION: We report the case of a 51-year-old man followed for chronic active hepatitis C, who presented in the fourth month of treatment with pegylated interferon and vidarabine with a sharp decline in visual acuity secondary to acute bilateral non-arteritic anterior ischemic optic neuropathy. The hepatitis C treatment was discontinued. His course was notable by the third week for a significant regression of papilledema with improvement in visual acuity in the right eye and no change in the left eye, remaining at counting fingers. After regressing for four years, the disease progressed to bilateral temporal optic atrophy without change in visual acuity. CONCLUSION: Pegylated interferon and Ribavirin(®) are commonly used in the treatment of chronic hepatitis C. They are the source of various ophthalmologic complications of varied severity. The pathophysiology of this ocular toxicity currently remains hypothetical. Non-arteritic ischemic optic neuropathy is still a relatively rare complication with a poor functional prognosis, often requiring discontinuation of treatment. Thus, careful ophthalmologic monitoring before and during antiviral treatment of patients with hepatitis C appears necessary.

Vidarabine is neither a potent nor a selective AC5 inhibitor.

Vidarabine was the first clinically approved antiviral drug, but due to safety and efficacy issues the drug is currently only used topically for herpes virus keratitis. Scientific interest in vidarabine has been recently renewed due to the fact that the compound exhibits beneficial effects in animal models of heart failure and cancer, replicating effects of the knockout of adenylyl cyclase 5 (AC5). Therefore, vidarabine has been suggested to mediate these effects via selective inhibition of AC5. Based on these results, clinical studies with vidarabine in humans for heart failure and cancer have been proposed. Here, evidence is presented that vidarabine is neither a potent nor a selective AC5 inhibitor. Greatest caution should be exerted when proposing new mechanisms of actions and clinical uses for vidarabine.

In vitro activity of six antiviral drugs against equid alphaherpesvirus type 1 indicates ganciclovir as promising drug for in vivo studies / A atividade in vitro de seis drogas antivirais contra o alfaherpesvírus equino tipo 1 indica que o ganciclovir é uma droga promissora para estudos in vivo

ABSTRACT: Equid alphaherpesvirus type 1 (EHV-1) is distributed worldwide and is a major agent of abortion, respiratory and neurological disease in horses. No specific treatment is available for EHV-1 infection, yet the potential of antiviral therapy has been explored. In this study we investigated the in vitro activity of Acyclovir, Ganciclovir, Foscarnet, Famciclovir, Vidarabina and Cidofovir against EHV-1. For this, the MTT test was performed, in which all the tested drugs showed no toxicity up to 200μg/mL. Subsequently, different drug concentrations were submitted to viral plaque reduction assays in cell culture. The selectivity index (SI) of the compounds was determined using the cytotoxic concentration for 50% of cells (CC50), obtained by MTT, and effective drug concentration to inhibit by 50% the number of viral plaques (EC50). Ganciclovir (SI: 490; EC50: 1.9 μg/mL) was the most efficient and safest drug against EHV-1, followed by Cidofovir (SI: 150, EC50: 5.7μg/mL), Acyclovir (SI: 37.4, EC50: 22.2μg/mL), Famciclovir (SI: 25.1, EC50: 24.5μg/mL), Vidarabine (SI: 12.2, EC50: 40.9μg/mL) and Foscarnet (SI: 6.9, EC50: 49.5 μg/mL), respectively. These results indicated that Ganciclovir (followed by Cidofovir), is a promising candidate for use in in vivo experiments.

RESUMO: O alfaherpesvírus equino tipo 1 (EHV-1) está amplamente distribuído nos rebanhos equinos de todo o mundo e é um dos principais agentes causadores de abortos, doença respiratória e neurológica em equinos. Ainda não há tratamento específico para a infecção pelo EHV-1 em equinos, mas o potencial da terapia antiviral tem sido investigado. Neste trabalho, foi investigada a atividade anti-herpética in vitro dos fármacos Aciclovir, Ganciclovir, Foscanet, Famciclovir, Vidarabina e Cidofovir frente ao EHV-1. Para isso, foi realizado o teste de MTT, em que todas as drogas não apresentaram citotoxicidade até a dose de 200μg/mL. A seguir, diferentes concentrações dos fármacos foram submetidas ao teste de redução de placas virais em cultivo celular. O índice de seletividade (IS) dos compostos foi determinado usando a concentração citotóxica para 50% dos cultivos celulares (CC50), obtida pelo MTT, e pela concentração dos fármacos efetiva para inibir em 50% o número de placas virais (EC50). O Ganciclovir (IS: 490; EC50: 1,9μg/mL) foi o mais eficiente e seguro frente ao EHV-1, seguido pelo Cidofovir (IS: 150; EC50: 5,7 μg/mL), Aciclovir (IS: 37,4; EC50: 22,2μg/mL), Famciclovir (IS: 25,1; EC50: 24,5μg/mL), Vidarabina (IS: 12,2; EC50: 40,9μg/mL) e Foscarnet (IS: 6,9; EC50: 49,5μg/mL). Estes resultados indicam que o Ganciclovir constitui-se em um candidato para uso em experimentos in vivo.