Effective Antiviral Concentrations Research Articles

Safety, Tolerability, and Pharmacokinetics of Intravenous Doses of PF-07304814, a Phosphate Prodrug Protease Inhibitor for the Treatment of SARS-CoV-2, in Healthy Adult Participants.

Studies on targeted antivirals for treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the ongoing pandemic, are limited. PF-07304814 (lufotrelvir) is the phosphate prodrug of PF-00835231, a protease inhibitor targeting the 3C-like protease of SARS-CoV-2. This phase 1 study evaluated the safety, tolerability, and pharmacokinetics (PK) of single ascending intravenous doses of lufotrelvir (continuous 24-hour infusion of 50, 150, 500, or 700 mg) versus placebo in healthy volunteers (2 interleaving cohorts: 1, n = 8; 2, n = 7). Each dosing period was separated by a washout interval (≥5 days). Treatment-emergent adverse events, PK, and biomarker concentrations were estimated from plasma/urine samples. Lufotrelvir was administered to 15 volunteers (mean [SD] age 39.7 [11.8] years). No serious adverse events, discontinuations, or deaths were reported. Mean maximum observed concentration of PF-00835231 (active moiety; 97.0 ng/mL to 1288 ng/mL) were observed between median time to maximum concentration of 14 to 16 hours after the start of the lufotrelvir infusion. Near-maximum plasma concentrations of PF-00835231 were observed ≈6 hours after infusion start and sustained until infusion end. PF-00835231 plasma concentrations declined rapidly after infusion end (mean terminal half-life: 500 mg, 2.0 hours; 700 mg, 1.7 hours). Approximately 9%-11% of the dose was recovered in urine as PF-00835231 across doses. A continuous, single-dose, 24-hour infusion of lufotrelvir (50-700 mg) was rapidly converted to PF-00835231 (active moiety), with dose-proportional PK exposures and no significant safety concerns. A daily, 24-hour continuous infusion of 270 to 350 mg is expected to maintain PF-00835231 concentration at steady state/above effective antiviral concentrations. Further studies exploring lufotrelvir efficacy in patients with coronavirus disease 2019 are ongoing.

Zirconium-Based Metal-Organic Frameworks as Acriflavine Cargos in the Battle against Coronaviruses─A Theoretical and Experimental Approach.

In this study, we present a complementary approach for obtaining an effective drug, based on acriflavine (ACF) and zirconium-based metal–organic frameworks (MOFs), against SARS-CoV-2. The experimental results showed that acriflavine inhibits the interaction between viral receptor-binding domain (RBD) of spike protein and angiotensin converting enzyme-2 (ACE2) host receptor driving viral cell entry. The prepared ACF@MOF composites exhibited low (MOF-808 and UiO-66) and high (UiO-67 and NU-1000) ACF loadings. The drug release profiles from prepared composites showed different release kinetics depending on the local pore environment. The long-term ACF release with the effective antiviral ACF concentration was observed for all studied ACF@MOF composites. The density functional theory (DFT) calculations allowed us to determine that π–π stacking together with electrostatic interaction plays an important role in acriflavine adsorption and release from ACF@MOF composites. The molecular docking results have shown that acriflavine interacts with several possible binding sites within the RBD and binding site at the RBD/ACE2 interface. The cytotoxicity and ecotoxicity results have confirmed that the prepared ACF@MOF composites may be considered potentially safe for living organisms. The complementary experimental and theoretical results presented in this study have confirmed that the ACF@MOF composites may be considered a potential candidate for the COVID-19 treatment, which makes them good candidates for clinical trials.

Identification of broad anti-coronavirus chemical agents for repurposing against SARS-CoV-2 and variants of concern

Endemic human coronaviruses (hCoVs) 229E and OC43 cause respiratory disease with recurrent infections, while severe acute respiratory syndrome (SARS)-CoV-2 spreads across the world with impact on health and societies. Here, we report an image-based multicycle infection procedure with α-coronavirus hCoV-229E-eGFP in an arrayed chemical library screen of 5440 clinical and preclinical compounds. Toxicity counter selection and challenge with the β-coronaviruses OC43 and SARS-CoV-2 in tissue culture and human airway epithelial explant cultures (HAEEC) identified four FDA-approved compounds with oral availability. Methylene blue (MB, used for the treatment of methemoglobinemia), Mycophenolic acid (MPA, used in organ transplantation) and the anti-fungal agent Posaconazole (POS) had the broadest anti-CoV spectrum. They inhibited the shedding of SARS-CoV-2 and variants-of-concern (alpha, beta, gamma, delta) from HAEEC in either pre- or post exposure regimens at clinically relevant concentrations. Co-treatment of cultured cells with MB and the FDA-approved SARS-CoV-2 RNA-polymerase inhibitor Remdesivir reduced the effective anti-viral concentrations of MB by 2-fold, and Remdesivir by 4 to 10-fold, indicated by BLISS independence synergy modelling. Neither MB, nor MPA, nor POS affected the cell delivery of SARS-CoV-2 or OC43 (+)sense RNA, but blocked subsequent viral RNA accumulation in cells. Unlike Remdesivir, MB, MPA or POS did not reduce the release of viral RNA in post exposure regimen, thus indicating infection inhibition at a post-replicating step as well. In summary, the data emphasize the power of unbiased, full cycle compound screens to identify and repurpose broadly acting drugs against coronaviruses.

Methotrexate inhibits SARS-CoV-2 virus replication "in vitro".

In early 2020 the new respiratory syndrome COVID‐19 (caused by the zoonotic SARS‐CoV‐2 virus) spread like a pandemic, starting from Wuhan, China, causing severe economic depression. Despite some advances in drug treatments of medical complications in the later stages of the disease, the pandemic's death toll is tragic, as no vaccine or specific antiviral treatment is currently available. By using a systems approach, we identify the host‐encoded pathway, which provides ribonucleotides to viral RNA synthesis, as a possible target. We show that methotrexate, an FDA‐approved inhibitor of purine biosynthesis, potently inhibits viral RNA replication, viral protein synthesis, and virus release. The effective antiviral methotrexate concentrations are similar to those used for established human therapies using the same drug. Methotrexate should be most effective in patients at the earliest appearance of symptoms to effectively prevent viral replication, diffusion of the infection, and possibly fatal complications.

Broad-spectrum antiviral JL122 blocks infection and inhibits transmission of aquatic rhabdoviruses

The aquaculture industry is growing rapidly to meet the needs for global protein consumption. Viral diseases in aquaculture are quite challenging due to lack of treatment options as well as limited injection-delivery vaccines, which are costly. Thus, water-immersion antiviral treatments are highly desirable. This study focused on broad-spectrum, light-activated antivirals that target the viral membrane (envelope) of viruses to prevent viral-cell membrane fusion, ultimately blocking viral entry into cells. Of the tested small-molecules, JL122, a new broad-spectrum antiviral previously unexplored against aquatic viruses, blocked infection of three aquatic rhabdoviruses (IHNV, VHSV and SVCV) in cell culture and in two live fish challenge models. Importantly, JL122 inhibited transmission of IHNV from infected to uninfected rainbow trout. Further, the effective antiviral concentrations were not toxic to cells or susceptible fish. These results show promise for JL122 to become an immersion treatment option for outbreaks of aquatic enveloped viral infections.

In vitro evaluation of cutaneous penetration of acyclovir from semisolid commercial formulations and relation with its effective antiviral concentration

The evaluation of drug permeation/penetration of semisolid formulations into animal skin can be useful to supplement the pharmaceutical equivalence. This paper describes the in vitro assessment of acyclovir (ACV) into porcine skin from commercial formulations with etermination of drug concentration in different layers of cutaneous tissue to correlate with effective antiviral concentration in order to improve the equivalence decision. Studies were conducted using Franz cells and porcine skin. Selected pharmaceutical creams containing ACV had identical (reference and generic) and different (similar) excipients. A software program was employed for the simulation of antiviral effectiveness in the skin. Regarding ACV skin penetration, the first batch of the generic product showed a significant difference from reference and similar products, while in the second batch all products demonstrated equivalent drug penetration in the skin. Simulation studies suggest that formulations analysed exhibit a pharmacological effect even when in contact with Herpes simplex strains of high IC50 (inhibitory concentration required to reduce viral replication by 50%). According to results, it can be assumed that the in vitro cutaneous permeation/penetration study does not supply sensitivity information regarding small alterations of ACV semisolid formulations due to the variability inherent to the method, although it can be relevant to pharmaceutical equivalence studies in the development of semisolid products.

STUDY OF ANTIADENOVIRALACTIVITY OF NEW FLUORINECONTAINING HETEROCYCLIC COMPOUNDS

Purpose: To study the cytotoxic action and antiviral activity of new fluorinated nucleoside compounds on human adenovirus model and the role of individual molecular fragments in their activity. Methods. Cytotoxic activity of the compounds was determined by the MTT method. Antiviral activity of substances was studied using cyto-morphological method with acridine orange dye. The virus-specific intranuclear inclusions were determined. Results. In present study the cytotoxicity of 2N-substituted-4-tosyl-5-polyfluoroalkyl-1,2,3-triazoles for Hep-2 and Hela cell lines were studied. The dependence of cytotoxicity on the compounds in the structure of substituents in the aromatic rings of the molecules was defined. Combination of residues of 3-hlorotetrahydropyran, 3-chloro-dihydrofuran tetrahydrofuran in a glycosidic moiety with trifluoromethyl or perfluoropropyl in a triazole ring were more toxic. Antiviral activity of 3 compounds (G7, G8 and G10) against HAdV5 in vitro was revealed. The effective antiviral concentrations (EC50) for them were 16, 70 and 186 mg/ml, and the selectivity indexes were equal to 91, 8 and 4, respectively. Conclusions. High rates of antiviral activity and low cytotoxicity of G8 compound make it perspective for development antiviral agents.

Ruxolitinib and tofacitinib are potent and selective inhibitors of HIV-1 replication and virus reactivation in vitro.

The JAK-STAT pathway is activated in both macrophages and lymphocytes upon human immunodeficiency virus type 1 (HIV-1) infection and thus represents an attractive cellular target to achieve HIV suppression and reduced inflammation, which may impact virus sanctuaries. Ruxolitinib and tofacitinib are JAK1/2 inhibitors that are FDA approved for rheumatoid arthritis and myelofibrosis, respectively, but their therapeutic application for treatment of HIV infection was unexplored. Both drugs demonstrated submicromolar inhibition of infection with HIV-1, HIV-2, and a simian-human immunodeficiency virus, RT-SHIV, across primary human or rhesus macaque lymphocytes and macrophages, with no apparent significant cytotoxicity at 2 to 3 logs above the median effective antiviral concentration. Combination of tofacitinib and ruxolitinib increased the efficacy by 53- to 161-fold versus that observed for monotherapy, respectively, and each drug applied alone to primary human lymphocytes displayed similar efficacy against HIV-1 containing various polymerase substitutions. Both drugs inhibited virus replication in lymphocytes stimulated with phytohemagglutinin (PHA) plus interleukin-2 (IL-2), but not PHA alone, and inhibited reactivation of latent HIV-1 at low-micromolar concentrations across the J-Lat T cell latency model and in primary human central memory lymphocytes. Thus, targeted inhibition of JAK provided a selective, potent, and novel mechanism to inhibit HIV-1 replication in lymphocytes and macrophages, replication of drug-resistant HIV-1, and reactivation of latent HIV-1 and has the potential to reset the immunologic milieu in HIV-infected individuals.

Mechanisms Associated with HIV-1 Resistance to Acyclovir by the V75I Mutation in Reverse Transcriptase

It has recently been demonstrated that the anti-herpetic drug acyclovir (ACV) also displays antiviral activity against the human immunodeficiency virus type 1 (HIV-1). The triphosphate form of ACV is accepted by HIV-1 reverse transcriptase (RT), and subsequent incorporation leads to classical chain termination. Like all approved nucleoside analogue RT inhibitors (NRTIs), the selective pressure of ACV is associated with the emergence of resistance. The V75I mutation in HIV-1 RT appears to be dominant in this regard. By itself, this mutation is usually not associated with resistance to currently approved NRTIs. Here we studied the underlying biochemical mechanism. We demonstrate that V75I is also selected under the selective pressure of a monophosphorylated prodrug that was designed to bypass the bottleneck in drug activation to the triphosphate form (ACV-TP). Pre-steady-state kinetics reveal that V75I discriminates against the inhibitor at the level of catalysis, whereas binding of the inhibitor remains largely unaffected. The incorporated ACV-monophosphate (ACV-MP) is vulnerable to excision in the presence of the pyrophosphate donor ATP. V75I compromises binding of the next nucleotide that can otherwise provide a certain degree of protection from excision. Collectively, the results of this study suggest that ACV is sensitive to two different resistance pathways, which warrants further investigation regarding the detailed resistance profile of ACV. Such studies will be crucial in assessing the potential clinical utility of ACV and its derivatives in combination with established NRTIs.

Novel Nonnucleoside Inhibitor of Hepatitis C Virus RNA-Dependent RNA Polymerase

A novel nonnucleoside inhibitor of hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), [(1R)-5-cyano-8-methyl-1-propyl-1,3,4,9-tetrahydropyano[3,4-b]indol-1-yl] acetic acid (HCV-371), was discovered through high-throughput screening followed by chemical optimization. HCV-371 displayed broad inhibitory activities against the NS5B RdRp enzyme, with 50% inhibitory concentrations ranging from 0.3 to 1.8 microM for 90% of the isolates derived from HCV genotypes 1a, 1b, and 3a. HCV-371 showed no inhibitory activity against a panel of human polymerases, including mitochondrial DNA polymerase gamma, and other unrelated viral polymerases, demonstrating its specificity for the HCV polymerase. A single administration of HCV-371 to cells containing the HCV subgenomic replicon for 3 days resulted in a dose-dependent reduction of the steady-state levels of viral RNA and protein. Multiple treatments with HCV-371 for 16 days led to a >3-log10 reduction in the HCV RNA level. In comparison, multiple treatments with a similar inhibitory dose of alpha interferon resulted in a 2-log10 reduction of the viral RNA level. In addition, treatment of cells with a combination of HCV-371 and pegylated alpha interferon resulted in an additive antiviral activity. Within the effective antiviral concentrations of HCV-371, there was no effect on cell viability and metabolism. The intracellular antiviral specificity of HCV-371 was demonstrated by its lack of activity in cells infected with several DNA or RNA viruses. Fluorescence binding studies show that HCV-371 binds the NS5B with an apparent dissociation constant of 150 nM, leading to high selectivity and lack of cytotoxicity in the antiviral assays.

Effects of aromatic cationic molecules on bovine viral diarrhea virus and embryonic development

Bovine viral diarrhea virus (BVDV) has been shown to replicate in embryo culture systems and remain associated with bovine embryos developing in vitro. In this study, novel antiviral agents were evaluated for capability to inhibit replication of BVDV without affecting embryonic development. Serial concentrations of 2-[5(6)-{2-imidazolinyl}-2-benzimidazolyl]-5-(4-aminophenyl)furan (DB456) or 2-(4-[2-imidazolinyl]phenyl)-5-(4-methoxyphenyl)furan (DB606) were prepared in IVC medium. Then, bovine uterine tubal epithelial cells (UTC) were placed in IVC media with varying concentrations of DB456 or DB606. Within 1 h, a genotype I or II strain of BVDV was added to the cultures. Cultures were maintained for 7 days. Infectious virus was quantitated in IVC media collected on days 3 and 7 and in UTC lysates harvested on day 7. The effective antiviral concentrations of DB606 were much lower than effective antiviral concentrations of DB456. In subsequent experiments, IVF presumptive zygotes were cultured in IVC medium with or without DB456 or DB606 at multiple concentrations for 7 days to evaluate effect of the compound on conceptus development. On day 7, stage of embryonic development was observed, and blastocysts were harvested and stained using Hoechst 33342 to enumerate embryonic cells. While DB456 inhibited blastocyst development, DB606 at 20 times the effective antiviral concentration did not hinder blastocyst development or reduce the mean number of cells per blastocyst. These preliminary results indicated that bovine embryo cultures might be safely supplemented with effective concentrations of an antiviral agent.

Antiviral Activity and Pharmacokinetics of 1-(2,3-Dideoxy-2-Fluoro-β- l -Glyceropent-2-Enofuranosyl)Cytosine

1-(2,3-Dideoxy-2-fluoro-beta-L-glyceropent-2-enofuranosyl)cytosine (L-2'-Fd4C) is an L-nucleoside analogue with both anti-human immunodeficiency virus (HIV) and anti-hepatitis B virus (HBV) activity with median effective concentrations of 0.12 microM in peripheral blood mononuclear cells and 0.002 microM in HepG2-2.2.15 cells, respectively. The purpose of this study was to examine the antihepadnavirus potency and pharmacokinetics of L-2'-Fd4C in vivo. HBV-transgenic mice treated intraperitoneally with L-2'-Fd4C showed a reduction of HBV levels in their blood comparable to that produced by lamivudine. The pharmacokinetics of L-2'-Fd4C in rhesus monkeys was evaluated after intravenous and oral administration. The concentrations in plasma declined in a biexponential manner after intravenous administration, with a long terminal-phase half-life of 5.02 h. The steady-state volumes of distribution and systemic clearance were 1.09 liter x kg(-1) and 0.25 liter x h(-1) x kg(-1), respectively, with a renal clearance of 0.16 liter x h(-1) x kg(-1). The oral bioavailability was approximately 44%. About 53% of the compound administered intravenously and 19% of that administered orally were recovered unchanged in the urine within the 24-h urine collection period, and no other metabolite was detected. The compound penetrated the central nervous system at concentrations that exceeded the median effective antiviral concentration against HIV in cell cultures. Based upon these observations, further testing to develop this agent for treatment of HIV and HBV infections is warranted.

HIV-1 Resistance Profile of the Novel Nucleoside Reverse Transcriptase Inhibitor β-D-2′,3′-Dideoxy-2′,3′-Didehydro-5-Fluorocytidine (Reverset™)

Nucleoside reverse transcriptase inhibitors (NRTIs) represent the cornerstone of highly active antiretroviral therapy when combined with non-nucleoside reverse transcriptase inhibitors (NNRTIs) or HIV-1 protease inhibitors (PIs). Unlike the NNRTIs and PIs, NRTIs must be successively phosphorylated by cellular kinases to a triphosphate form, which represents the active metabolite possessing antiviral activity. Emergence of viral resistance to NRTIs has severely hampered treatment options for persons infected with HIV-1. As such, there is an urgent need to develop NRTIs capable of suppressing NRTI-resistant strains of HIV-1. We have recently reported that the cytidine analogue D-d4FC (DPC817, Reverset) effectively inhibits clinically prevalent resistant strains of HIV-1. In this report, we have extended these findings and now describe a detailed resistance profile for this novel NRTI. By examining a panel of 50 viruses carrying RTs derived from HIV-1 clinical isolates displaying a wide range of NRTI resistance mutations, we report that the median fold increase in effective antiviral concentration for such a panel of viruses is 3.2, which is comparable to tenofovir (2.8-fold) and didanosine (2.4-fold). D-d4FC is highly effective at inhibiting subsets of lamivudine- and zidovudine-resistant variants but, like other NRTIs, seems less potent against multi-NRTI-resistant viruses, particularly those carrying the Q151M complex of mutations. Finally, in vitro selections for HIV-1 mutants capable of replicating in the presence of D-d4FC yielded a mutant carrying the RT K65R mutation. This mutation confers 5.3- to 8.7-fold resistance to D-d4FC in vitro. These findings suggest that D-d4FC may represent an alternative NRTI for the treatment of individuals infected with lamivudine- and zidovudine-resistant strains of HIV-1.

Antiviral activity of Rwandan medicinal plants against human immunodeficiency virus type-1 (HIV-1).

Selected plants used in Rwandan traditional medicine for the treatment of infections and/or rheumatoid diseases were investigated for antiviral activity in vitro against human immunodeficiency virus type-1 (HIV-1). Of the 38 tested 80% ethanolic extracts, belonging to plants of 21 different families only the extracts from the leaves of Aspilia pluriseta (Asteraceae) and Rumex bequaertii (Polygonaceae) had interesting selectivity indices (SI = ratio of the 50% cytotoxic concentration to the 50% effective antiviral concentration) higher than 1. Further fractionation of the initially antivirally inactive ethanolic extract of Tithonia diversifolia, however, led to an aqueous fraction with a high anti-HIV-1 activity (SI > 461), indicating that the cytotoxicity of some plant components may mask the antiviral properties of the active plant substances in total plant extracts.

Antiviral activity against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) of ethnobotanically selected Ethiopian medicinal plants

Ethiopian medicinal plants used for the treatment of a variety of ailments including infectious diseases were screened for activity against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2). Seventy-one polar and nonpolar extracts derived from 21 plants belonging to 14 families were tested for inhibition of viral replication using HIV-1 (III(B)) and HIV-2 (ROD) strains. Selective inhibition of viral growth was assessed by the simultaneous determination of the in vitro cytotoxicity of each of the extracts against MT-4 cells. Six extracts made from the root bark of Bersama abyssinica Fresen, the leaves of Combretum paniculatum Vent., and Dodonaea angustifolia L.f., and the stem bark of Ximenia americana L. displayed antiviral activity at concentrations that were nontoxic to MT-4 cells. The highest selective inhibition of HIV-1 replication was observed with the acetone fraction of C. paniculatum and the methanol fraction of D. angustifolia which showed selectivity indices (ratio of 50% cytotoxic concentration to 50% effective antiviral concentration) of 6.4 and 4.9, and afforded cell protection of viral induced cytopathic effect of 100% and 99%, respectively, when compared with control samples. The greatest degree of antiviral activity against HIV-2 was achieved with the acetone extract of C. paniculatum (EC(50): 3 microg/mL), which also showed the highest selectivity index (32). The 50% cytotoxic concentration ranged from 0.5 microg/mL for the hexane extract of D. angustifolia L.f., the most cytotoxic of the extracts tested, to >250 microg/mL for some extracts such as the methanol fraction of Alcea rosea L., the least toxic tested. Only the polar extracts that were obtained by extraction with hydroalcohol, methanol or acetone exhibited inhibition of viral growth at subtoxic concentrations. The results obtained in this study enable the selection of extracts which show some specificity of action and support the further investigation of these extracts for their potential as new lead antiretroviral compounds.

Indolocarbazoles exhibit strong antiviral activity against human cytomegalovirus and are potent inhibitors of the pUL97 protein kinase

We have analyzed a panel of protein kinase inhibitors (PKIs) and found that some indolocarbazoles (Gö6976, K252a, K252c) proved to be highly effective inhibitors of GCV-sensitive and -resistant human cytomegalovirus (HCMV) strains, but did not show any effect against herpes simplex virus. Antiviral activity was determined by focus reduction assays (IC 50 ranging from 0.009 to 0.4 μM). Other inhibitors of serine/threonine kinases (Gö6850, H-7, roscovitine) were found to be ineffective. Virus yield at 5 days after infection was reduced by three orders of magnitude with nanomolar concentrations of the indolocarbazoles. These compounds were fully effective when added up to 24 h post infection and showed reduced activity up to 72 h post infection. Cytotoxicity assays in proliferating and non-proliferating cells demonstrated that the effective antiviral concentration of these compounds was significantly lower than either antiproliferative (IC 50/CC 50 ranging from 6.5 to 390) or cytotoxic (IC 50/CC 50 ranging from 72.5 to 1000) doses. The effects of PKIs on the virus-encoded protein kinase pUL97 were studied using recombinant vaccinia viruses. Indolocarbazoles strongly inhibited both pUL97 autophosphorylation (IC 50 ranging from 0.0012 to 0.013 μM) and pUL97-dependent ganciclovir phosphorylation (IC 50 ranging from 0.05 to 0.26 μM). Other inhibitors of serine/threonine kinases showed only weak (Gö6850) or no (H-7, roscovitine) effect on these pUL97 functions, while oxoflavone tyrosine kinase inhibitors had no effect at all.

Clinical pharmacokinetics of the prodrug oseltamivir and its active metabolite Ro 64-0802.

Oseltamivir is an ethyl ester prodrug of Ro 64-0802, a selective inhibitor of influenza virus neuraminidase. Oral administration of oseltamivir delivers the active antiviral Ro 64-0802 to the bloodstream, and thus all sites of influenza infection (lung, nasal mucosa, middle ear) are accessible. The pharmacokinetic profile of oseltamivir is simple and predictable, and twice daily treatment results in effective antiviral plasma concentrations over the entire administration interval. After oral administration, oseltamivir is readily absorbed from the gastrointestinal tract and extensively converted to the active metabolite. The absolute bioavailability of the active metabolite from orally administered oseltamivir is 80%. The active metabolite is detectable in plasma within 30 minutes and reaches maximal concentrations after 3 to 4 hours. After peak plasma concentrations are attained, the concentration of the active metabolite declines with an apparent half-life of 6 to 10 hours. Oseltamivir is eliminated primarily by conversion to and renal excretion of the active metabolite. Renal clearance of both compounds exceeds glomerular filtration rate, indicating that renal tubular secretion contributes to their elimination via the anionic pathway. Neither compound interacts with cytochrome P450 mixed-function oxidases or glucuronosyltransferases. The pharmacokinetic profile of the active metabolite is linear and dose-proportional, with less than 2-fold accumulation over a dosage range of oseltamivir 50 to 500 mg twice daily. Steady-state plasma concentrations are achieved within 3 days of twice daily administration, and at a dosage of 75mg twice daily the steady-state plasma trough concentrations of active metabolite remain above the minimum inhibitory concentration for all influenza strains tested. Exposure to the active metabolite at steady state is approximately 25% higher in elderly compared with young individuals; however, no dosage adjustment is necessary. In patients with renal impairment, metabolite clearance decreases linearly with creatinine clearance. A dosage reduction to 75mg once daily is recommended for patients with creatinine clearance <30 ml/min (1.8 L/h). The pharmacokinetics in patients with influenza are qualitatively similar to those in healthy young adults. In vitro and in vivo studies indicate no clinically significant drug interactions. Neither paracetamol (acetaminophen) nor cimetidine altered the pharmacokinetics of Ro 64-0802. Coadministration of probenecid resulted in a 2.5-fold increase in exposure to Ro 64-0802; however, this competition is unlikely to result in clinically relevant effects. These properties make oseltamivir a suitable candidate for use in the prevention and treatment of influenza.

Antiviral effect of a polysaccharide from Sclerotium glucanicum towards herpes simplex virus type 1 infection.

Among different neutral polysaccharides from natural sources, scleroglucan from Sclerotium glucanicum significantly inhibits the replication of herpes simplex virus type 1 on Vero cells. Scleroglucan belongs to a class of exopolymers, expressed by members of genus Sclerotium and consists of a linear beta-1,3-linked glucopyranose with side chains of single glucopyranose residues linked through beta-1,6 glycosidic bonds. The effective antiviral concentration of this polysaccharide is far from the cytotoxicity threshold and consequently this natural product possesses a good selectivity index. Results obtained in experiments carried out in order to clarify the mechanism of action of this carbohydrate indicate that the block of infection occurs during the very early phases of the viral mutliplication cycle since the highest inhibitory effect took place when it was added during the attachment step. The antiviral effect of scleroglucan seems to be related to its binding with membrane glycoproteins of HSV-1 particles which impedes the complex interactions of the virus with the cell plasma membrane.

Antiviral activity of Hawaiian medicinal plants against human immunodeficiency Virus Type-1 (HIV-1)

Hawaiian medicinal plants commonly used for the treatment of a variety of infections were screened for antiviral activity against human immunodeficiency virus type 1 (HIV-1). Sixty-one extracts derived from seventeen plants were tested for selective viral growth inhibition using the LAI (HTLV-IIIB) isolate. The greatest degree of antiviral activity was observed with aqueous extracts made from the bark of Eugenia malaccensis (L.) and the leaves of Pluchea indica (Less.) which had antiviral selectivity indices (50% cytotoxic concentration/50% effective antiviral concentration) of 109 and 94, respectively. These and other extracts conferred 100% cell protection against viral cytopathic effect when compared with control samples. Methanol and water extracts made from the Pipturus albidus (Gray) leaves and bark also achieved a high selective inhibition of virus replication with very low cytotoxicity. Plant extracts made from Aleurites moluccana (Willd.), Psychotria hawaiiensis (Gray), Clermontia aborescens (Mann), and Scaevola sericea (Forst.) also showed antiviral activity. These data provide a rationale for the characterization of antiviral natural products from these plants and related plant species.

In vitro Antimyxovirus and Anti-Human Immunodeficiency Virus Activities of Polyoxometalates

Polyoxometalates have been shown to inhibit the replication of retro-, toga-, paramyxo- and herpesviruses. The primary mechanism of the anti-human immunodeficiency virus type 1 (HIV-1) action of polyoxometalates seems to be inhibition of binding of virus to cells and inhibition of syncytium formation. Since myxoviruses and HIV-1 are known to interact with the cytoplasmic membrane by adsorption and penetration of virus and by fusion of infected and uninfected cells, 25 polyoxometalates were examined for anti-ortho-, anti-paramyxovirus and anti-HIV-1 activity in vitro. Of the 25 compounds evaluated, 24 showed antiviral effects against influenza virus A, 11 showed activity against respiratory syncytial virus, six showed activity against measles virus, and 23 were considered effective against HIV-1 at a lower concentration than that producing cytotoxicity. Four polyoxotungstates which had potent inhibitory effects were examined for inhibitory effects against additional ortho- and paramyxoviruses, and proved to have a broad spectrum of antimyxoviral activity. HS-058, the Keggin sandwich compound K10Fe4(H2O)2(PW9O34)2·nH2O, was inhibitory against influenza viruses A and B, respiratory syncytial virus, measles virus, and parainfluenza virus 2, with median effective concentrations of 1.4, 21.8, 7.4, 0.8 and 0.32 μ,M, respectively. However, HS-058 had no effect on parainfluenza virus 3 or mumps virus. The median cytotoxic concentration of HS-058 for Madin-Darby canine kidney (MDCK) and HEp-2 cells was more than 200 μM and that for HMV-2 and Vero cells was about 50 μM. When HS-058 was added at different times after influenza A and respiratory syncytial virus infection, it inhibited binding of the latter but not of the former to cells. However, at higher concentrations, HS-054 and HS-058 inhibited haemolysis of chick erythrocytes by influenza virus and syncytium formation involving respiratory syncytial virus-infected cells and uninfected cells. Four times the median effective antiviral concentration of HS-058 completely inhibited the growth of influenza virus A in MDCK cells when compound was added before virus adsorption. Furthermore, when HS-058 was added after virus adsorption, it inhibited the yield of virus in MDCK cells infected at low but not at high multiplicity of infection.