HSV-1(IC50=7.7-20 ng/mL);HSV-2(IC50=15-58 ng/mL)

Amenamevir (ASP2151) prevents the replication of both laboratory-stocked HSV strains and strains isolated in the US and Japan. Acyclovir (ACV) has mean EC50s against HSV-1 and HSV-2 of 29 (range, 18 to 38) and 71 ng/mL (range, 45 to 95), respectively, while amenamevir's mean EC50s against HSV-1 and HSV-2 are 14 (range, 7.7 to 20) and 30 ng/mL (range, 15 to 58), respectively. Compared to ACV, Amenamevir's EC50s against HSV strains are noticeably lower[1].

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In vitro antiviral activity of ASP2151 (amenamevir). [2]
The antiviral activities of ASP2151 (amenamevir) and ACV against 10 HSV-1 and HSV-2 strains in HEF cells were examined using a plaque reduction assay. Table 1 summarizes the EC50s of ASP2151 and ACV for each of the examined HSV strains. ASP2151 inhibited the replication of the clinical strains isolated in Japan and the United States as well as the laboratory-stocked strains. The mean EC50s of ASP2151 against HSV-1 and HSV-2 were 14 (range, 7.7 to 20) and 30 ng/ml (range, 15 to 58), respectively, whereas those of ACV were 29 (range, 18 to 38) and 71 ng/ml (range, 45 to 95), respectively. The EC50s of ASP2151 against HSV strains were significantly lower than those of ACV.

The administration of amenamevir (ASP2151) in the dose-dependent range of 3 to 30 mg/kg/day accelerates the reduction in virus titer. Regardless of the dosing interval, amenamevir treatment reduces lesion scores and HSV-1 titers in a dose-dependent manner. The PK parameters at which oral administration of Amenamevir completely suppresses HSV-1 growth are estimated based on the correlation curves. These parameters are 10,000 ng/mL or higher for the maximum concentration of drug in serum (Cmax), 60 μg • h/ml or higher for concentration-time curve over 24 h (AUC24h), and 21 to 24 h for T>100. Five days after infection, the mean plasma concentration of Amenamevir rises in a dose-dependent manner; doses of 3 mg Amenamevir/g or more markedly lower the intradermal HSV-1 titer[1].

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ASP2151 (amenamevir) is a potent helicase-primase inhibitor and a novel class of antiviral agent other than nucleoside compounds, such as aciclovir, valaciclovir and famciclovir. This study is the first randomized, double-blind, valaciclovir-controlled phase 3 study to evaluate the efficacy and safety of amenamevir in Japanese patients with herpes zoster when treated within 72 h after onset of rash. A total of 751 patients were randomly assigned to receive either amenamevir 400 mg or 200 mg p.o. once daily or valaciclovir 1000 mg three times daily (daily dose, 3000 mg) for 7 days. The primary efficacy end-point was the proportion of cessation of new lesion formation by day 4 ("day 4 cessation proportion"). The day 4 cessation proportions for amenamevir 400 and 200 mg and valaciclovir were 81.1% (197/243), 69.6% (172/247) and 75.1% (184/245), respectively. Non-inferiority of amenamevir 400 mg to valaciclovir was confirmed by a closed testing procedure. Days to cessation of new lesion formation, complete crusting, healing, pain resolution and virus disappearance were evaluated as secondary end-points. No significant differences were observed in any of the treatment groups. Amenamevir 400 and 200 mg were well tolerated as well as valaciclovir. The proportions of patients who experienced drug-related adverse events were 10.0% (25/249), 10.7% (27/252) and 12.0% (30/249) with amenamevir 400 and 200 mg and valaciclovir, respectively. In conclusion, amenamevir 400 mg appears to be effective and well tolerated for treatment of herpes zoster in immunocompetent Japanese patients. [1]

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Effect of ASP2151 (amenamevir) on intradermal HSV-1 titer.[2]
Following the cutaneous infection of mice with HSV-1 strain WT51, cutaneous lesions developed beginning on day 4 postinfection, and intradermal HSV-1 titers rapidly increased, peaking on days 4 to 5 postinfection (Fig. 1). In this model, almost all mice infected with HSV-1 strain WT51 in the vehicle group are dead from day 6 postinfection and show neurological signs, while ASP2151 and VCV reduce the mortality of HSV-1-infected mice (6). Lesion scores and intradermal HSV-1 titers in the mice infected with another HSV-1 strain, CI-116, showed almost similar time courses (data not shown). Using the cutaneously HSV-1-infected mouse model, a repeated oral dose of ASP2151 was administered three times daily at total doses of 3, 10, 30, 100, and 300 mg/kg/day for 3 days from day 4 postinfection. The skin of treated mice was collected, and the intradermal HSV-1 titer was then determined using the plaque method (Fig. 2).
ASP2151 (amenamevir) administration accelerated the reduction in virus titer in a dose-dependent manner in the range of 3 to 30 mg/kg/day (Fig. 2A). However, the efficacy of ASP2151 was comparable at doses of 30 mg/kg/day and higher (Fig. 2B), suggesting that ASP2151 completely suppressed HSV-1 growth at the dose of 30 mg/kg/day.
The goal in treating herpetic disease is to prevent disease progress and accelerate the cure of the virus infection-induced lesions by suppressing viral growth at an early stage. Accordingly, the clinical efficacy of ASP2151 can be considered to have maximal effect at the dose that completely suppresses viral growth. However, it is difficult to estimate the dosing regimen of antiviral agents needed for viral suppression in clinical studies based solely on experiments in murine models due to possible differences in PK patterns between mice and humans. For this reason, we conducted a series of nonclinical PK/PD analyses to estimate the plasma ASP2151 concentration (PK/PD parameters) at which HSV-1 growth would be completely suppressed.

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Dose fractionation study in HSV-1-infected mice.[2]
Dose fractionation efficacy studies in animal models are a useful approach to elucidate PK/PD relationships of a target drug, as different patterns of plasma drug concentrations can result from dose fractionation, even on administration of identical daily doses (14, 30). As part of the PK/PD analyses of ASP2151 (amenamevir), we examined the effect of daily dose fractionation on the antiviral efficacy of ASP2151 in the HSV-1-infected mouse model. ASP2151 doses of 1, 3, 10, 30, and 100 mg/kg/day were administered to mice for 5 days from the day of HSV-1 infection either as a single dose or as two or three divided doses. Mean HSV-1 titers and lesion scores were then assessed on day 5 postinfection (Fig. 3). ASP2151 treatment decreased both lesion scores and HSV-1 titers in a dose-dependent manner, irrespective of the dosing interval. Lesion development was not observed in mice treated with the following ASP2151 dosages and administration intervals: 30 and 100 mg/kg/day every 24 hours (q24h); 10, 30, and 100 mg/kg/day q12h; or 30 and 100 mg/kg/day q8h (Fig. 3A). HSV-1 titers were close to the lower detection limit in infected mice treated with ASP2151 at dosages of 100 mg/kg/day q12h and 30 or 100 mg/kg/day q8h (Fig. 3B). The relationship between lesion score and HSV-1 titer in each animal on day 5 postinfection is shown in Fig. 3C. Animals with an HSV-1 titer below 5 log10 PFU/skin did not develop cutaneous lesions (score, 0), indicating that HSV-1 titer was more sensitive than lesion score as a direct PD marker of HSV-1 infection. These results suggested that dividing the daily dose of ASP2151 had greater efficacy in reducing HSV-1 titer than did the same daily dose as a single dose.

Plaque reduction assay. [2]
The antiviral activities of ASP2151 (amenamevir) and ACV against HSVs were tested using a plaque reduction assay, as described previously. Briefly, HEF cells were seeded into multiwell plates and incubated until they formed a monolayer. After the medium was removed, the cells were infected with HSV-1 or HSV-2, and the plates were further incubated for 1 h at 37°C. The cells were washed twice with maintenance medium and then treated with the test compound until clear plaques appeared. The cells were then fixed with 10% formalin in phosphate-buffered saline, stained with a 0.02% crystal violet solution, and the number of plaques was determined under a light microscope. The EC50, which represents the concentration of test compound needed to reduce the plaque number by 50%, was calculated using nonlinear regression analysis with a sigmoid-maximum effect (Emax) model.

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ATPase assay [3]
ssDNA-dependent ATPase activity of the HSV-1 helicase–primase complex was determined using an assay modified from a previously described method.10 The reaction buffer contained 20 mM HEPES (pH 7.6), 2 mM MgCl2, 10 mM dithiothreitol (DTT), 9 μg/mL ssDNA prepared using calf thymus DNA, 90 μM ATP and 25 ng of the enzyme complex in a reaction volume of 10 μL. The mixture containing ASP2151 (amenamevir) at concentrations of 0.0001–3 μM was incubated for 75 min at 37°C. ATP hydrolysis was determined by adding 10 μL of Biomol® green according to the manufacturer's instructions.

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DNA helicase assay [3]
Forked DNA helicase substrate was prepared using the oligonucleotides 5′-CAGTCACGACGTTGTAAAACGACGGCCAGTGTTATTGCATGAAAGCCCGGCTG-3′ labelled at the 5′ end with Alexa Fluor® 488 (Invitrogen) and unlabelled 5′-GTCGGCCCACCTTCCTGTTATTGACTGGCCGTCGTTTTACAACGTCGTGACTG-3′ as previously reported.20 The reaction mixture (10 μL) contained 20 mM HEPES (pH 7.6), 1 mM DTT, 5 mM MgCl2, 2 mM ATP, 1 μg of helicase–primase complex, 20 nM forked DNA helicase substrate and a 200 nM concentration of a capture strand (5′-CAGTCACGACGTTGTAAAACGACGGCCAGT-3′). Reactions containing ASP2151 (amenamevir) were allowed to proceed for 60 min at 30°C, and then the products were electrophoresed through a 20% non-denaturing polyacrylamide gel. Fluorescence was detected using the ProXPRESS® 2D Proteomic Imaging System.

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Primase assay [3]
Primase activity was measured by detecting synthesized RNA primers in the presence of fluorescence-labelled CTP using the 51-mer DNA oligonucleotide 5′-CTTCTTCGGTTCCGACTACCCCTCCCGACTGCCTATGATGTTTATCCTTTG-3′ as a template.13,19 Reaction mixtures (10 μL) containing 50 mM Tris–HCl (pH 8.0), 10 mM MgCl2, 1 mM DTT, 1 mM ATP, 1 mM GTP, 1 mM UTP, 2 μM fluorescence-labelled CTP, 10 pmol of the 51-mer template and 2 µg of the helicase–primase complex were incubated at 30°C for 90 min in the presence of vehicle (0.1% DMSO) or ASP2151 (amenamevir). Reactions were then quenched by 10 μL of stop buffer containing 50 mM EDTA (pH 8.0) and 90% (v/v) formamide. The products were heat denatured at 95°C for 5 min and separated via denaturing PAGE (15% polyacrylamide–7 M urea), and then fluorescence was detected using the ProXPRESS® 2D Proteomic Imaging System.

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Plaque reduction assay (PRA) and cytotoxicity assay [3]
HEF cells were seeded into multi-well plates and incubated until the cells formed a monolayer. After the medium was removed, the cells were infected with VZV, HSV-1 or HSV-2 at a titre of 40 plaque forming units (pfu)/well. The plates were then incubated for 1 h at 37°C. After being washed twice with maintenance medium, cells were treated with the test compound until clear plaques appeared. The cells were then fixed with 10% formalin in PBS and stained with 0.02% Crystal Violet solution. The number of plaques present was counted under a microscope. An MTT assay or a Neutral Red assay was conducted using HEF cells to determine the cytotoxic concentration causing a 50% reduction in the number of viable cells (CC50).

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PAGE of virus-specific PCR fragments [3]
HEF cells infected with HSV-1, HSV-2, VZV and HCMV were exposed to ASP2151 (amenamevir) and incubated until plaques clearly appeared in virus control wells. Cells were then collected to extract whole DNA using the Gentra® Puregene® Cell Kit. PCR was performed using a specific primer set targeting US4, ORF31 or UL83 for HSV-1 and HSV-2, VZV or HCMV, respectively [Table S1, available as Supplementary data at JAC Online (http://jac.oxfordjournals.org/)]. Each PCR was electrophoresed, stained and visualized. Human β-actin gene was used as an internal control.

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ASP2151 (amenamevir)-resistant VZV mutants [3]
ASP2151-resistant VZV mutant, ‘C2151rm’, was selected by serial passage of VZV strain CaQu using HEF cells in the presence of stepwise-increasing concentrations of ASP2151 from 0.1 to 60 μM. In brief, monolayered HEF cells in a 25 cm2 flask were initially infected with cell-free VZV stock of parental strain CaQu and cultured in the presence of the 50% effective concentration (EC50) of ASP2151 (0.1 μM) until cytopathic effects were visible. After cells were harvested, 10% of the collected cells were then dispersed on fresh monolayered HEF cells as a cell-associated VZV source and incubated in the presence of 1×, 2× or 4× the concentration of ASP2151 previously used. After incubation for 4–6 days, the cells from the flask in which cytopathic effects were evident for <50% of cells were used as viral source for the next passage. The procedure was continued until the ASP2151 concentration reached 60 μM (600 × EC50). After the ASP2151 concentration reached 60 µM, virus passage was repeated five times in the presence of 60 µM ASP2151 to avoid contamination. The total number of passages and total period of the process were 16 and 72 days, respectively. Then cell-free VZV stock, designated C2151rm, was prepared according to the method described previously.22 DNA regions including the full-length open reading frame of the helicase (ORF55) and primase (ORF6) genes, were amplified via PCR by using the corresponding primer sets (ORF55, 5′-TGGTCATTTGGGTTACTTCCA-3′ and 5′-AGTGAAGAACCCGCCTAAC-3′; and ORF6, 5′-CAGCGGTTAAAGCCTCTTG-3′ and 5′-CGGTCCACCATTAATCACC-3′) and viral DNAs extracted from cell-free stock of the C2151rm and its parent CaQu. Each PCR product was used as a template for direct sequencing. Amino acid substitutions were analysed using GENETYX® software.

Plaque reduction assay is used to evaluate the antiviral efficacy of Amenamevir (ASP2151) and ACV against HSVs. In a nutshell, HEF cells are cultivated in multiwell plates and allowed to grow into a monolayer. Following the removal of the medium, HSV-1 or HSV-2 is added to the cells, and the plates are then incubated for an additional hour at 37°C. After twice washing the cells in maintenance medium, the test compound—which includes amenamevir—is applied to the cells until clear plaques start to form.After staining the cells with 0.02% crystal violet solution and fixing them with 10% formalin in phosphate-buffered saline, the number of plaques is counted under a light microscope. Using a sigmoid-maximum effect (Emax) model in nonlinear regression analysis, the EC50, or the concentration of test compound required to reduce the plaque number by 50%, is determined[1].

Female hairless mice (HOS:HR-1, 7 to 8 weeks old) are infected in the dorsolateral skin stripped as a small square using a needle under anesthesia with a suspension of HSV-1 strains WT51 (15 μL/mouse; titer, 2×108 PFU/mL) or CI-116 (15 μL/mouse; titer, 4×107 PFU/mL). Day zero postinfection is the day of HSV-1 infection. HSV-1-infected mice (n=5) are given oral doses of 1, 3, 10, 30, or 100 mg/kg/day of ASP2151 for a duration of 5 days. Treatments with amenamevir (ASP2151) begin two to three hours after HSV infection. The medication is taken once daily (every 24 hours, q24h), twice a day (every 12 hours, q12h), or three times a day (every 8 hours, q8h). On day five after infection, lesion scores and intradermal HSV-1 titers are measured[1].

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Mouse HSV infection model. [2]
All animal experimental procedures were approved by the Animal Ethical Committee of Astellas Pharma, Inc. Female hairless mice (HOS:HR-1, 7 to 8 weeks old) were infected with a suspension of HSV-1 strain WT51 (15 μl/mouse; titer, 2 × 108 PFU/ml) or CI-116 (15 μl/mouse; titer, 4 × 107 PFU/ml) in the dorsolateral skin stripped as a small square using a needle, under anesthesia. The day of HSV-1 infection was designated day zero postinfection.

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Dose fractionation study.Total daily doses of 1, 3, 10, 30, or 100 mg/kg/day ASP2151 (amenamevir) were orally administered to HSV-1-infected mice (n = 5) for 5 days. ASP2151 treatments were started 2 to 3 h after HSV infection either as a single daily dose (every 24 h, q24h) or as two (every 12 h, q12h) or three (every 8 h, q8h) divided doses. Lesion scores and intradermal HSV-1 titers were measured on day 5 postinfection, as described below.

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Continuous-infusion study. [2]
Mice in each group (n = 10) were implanted subcutaneously with an Alzet miniosmotic pump filled with ASP2151 (amenamevir) solution (1, 3, 10, and 20 mg/g in polyethylene glycol 400 [PEG 400]) or vehicle at 1 to 2 h before infection. It had been preliminarily confirmed that the way of infusion kept ASP2151 concentration in plasma constant at levels corresponding to ASP2151 solutions used over the study period. Based on the pumping rate (23.28 μl/day) and mean animal body weight (20.4 g), the daily dosage of ASP2151 for the groups infused with 1-, 3-, 10-, and 20-mg/g ASP2151 solution corresponded to approximately 1.1, 3.3, 11, and 22 mg/kg of body weight/day, respectively. Infusion was continued for 5 days. Lesion scores, intradermal HSV-1 titers, and ASP2151 concentrations in plasma were measured on day 5 postinfection, as described below.

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Measurement of lesion scores, intradermal HSV-1 titers, and concentration of ASP2151 (amenamevir) in plasma. [2]
Disease severity for each animal was scored on a composite scale from 0 to 7 based on the severity of zosteriform lesions and general symptoms according to previously published criteria (6). After scoring disease symptoms, skin and/or blood samples from each animal were obtained. Skin samples were homogenized in 10 ml ice-cold saline, and debris was then removed by centrifugation. The HSV-1 titer in each sample was determined using a plaque assay. The concentration of ASP2151 in plasma obtained from mouse blood was determined using the liquid chromatography-tandem mass spectrometry (LC/MS/MS) method.

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Simulation of PK after repeated oral administration of ASP2151 (amenamevir). [2]
To estimate PK parameters after repeated oral dosing of ASP2151, concentrations of ASP2151 in plasma were measured after a single oral administration to mice. ASP2151 was administered to mice (n = 3) at doses of 0.33, 3, 30, and 100 mg/kg, and blood samples were then collected from the heart at 0.25, 0.5, 1, 2, 4, 8, and 12 h postdosing. The concentrations in plasma after repeated administration of ASP2151 were simulated by the nonparametric superposition method using WinNonlin software, and data were obtained from the single administration of ASP2151 at a dose of 30 mg/kg.

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PK/PD modeling. [2]
The relationship between the steady-state PK parameters of peak concentration (Cmax), area under the concentration-time curve (AUC24 h), and time above the threshold concentration and the antiviral efficacy of ASP2151 (amenamevir) was examined using the sigmoid-Emax model. The threshold concentration was the concentration of ASP2151 required to completely inhibit the growth of HSV-1 in the dose fractionation experiment.The PK parameters were fitted to the mean intradermal HSV-1 titer (log10 PFU/skin) using the sigmoid dose-response (variable slope) program of GraphPad Prism. The following equation was used: y = bottom + (top − bottom)/(1 + 10[(log EC50− x) × hill slope]), where x is the logarithm of each PK variable and y is the response intradermal HSV-1 titer (log10 PFU/skin). The “top” value was fixed as the mean value for the vehicle groups, and the “bottom” value was fixed as the log10 250 value, which represents the detection limit value of the HSV-1 titer.

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In vivo antiviral activity [3]
Hairless mice (HOS:HR-1, female, aged 7 weeks at virus infection) were infected (designated as day 0 post-infection) with HSV-1 strain WT51 (15 μL/mouse of suspension at a titre of 8.0 × 105 pfu/mL) on dorsolateral skin that had been scratched in a grid-like pattern with a 27-gauge needle under anaesthesia. ASP2151 (amenamevir) at doses of 0.3, 1, 3, 10 and 30 mg/kg, or valaciclovir at doses of 3, 10, 30 and 100 mg/kg (suspension in 0.5% methylcellulose solution) was orally administered twice daily for 5 days starting 3 h after viral inoculation. Ten mice per test group were used. Disease course was monitored daily for 17 days and scored on a composite scale from 0 to 7 based on the severity of zosteriform lesions and general symptoms according to the following criteria: score 0, no sign of infection; score 1, localized, barely perceptible small vesicles; score 2, slight vesicle spread; score 3, large patches of vesicles formed; score 4, zosteriform vesicles; score 5, large patches of ulcers formed; score 6, large zosteriform ulcers (severe); and score 7, hind limb paralysis or death.

Pharmacokinetic studies of ASP2151 (Amenamevir) were conducted in mice. [2] After a single oral administration of 0.33, 3, 30, and 100 mg/kg of ASP2151 to mice, the plasma concentration of ASP2151 increased with increasing dose and reached Cmax 0.25 to 1.0 hours after administration (Figure 4A). The Cmax corresponding to the doses of 0.33, 3, 30, and 100 mg/kg were 50, 646, 5199, and 14903 ng/ml, respectively, and the AUC0–∞ values were 0.22, 2.37, 21.97, and 56.12 μg·h/ml, respectively. The plasma concentrations after a single oral administration of 30 mg/kg of ASP2151 were analyzed using a one-compartment model. Figure 4B shows the simulated plasma concentrations of ASP2151 at doses of 100 mg/kg/day q24h, 100 mg/kg/day q12h, and 30 mg/kg/day q8h. When the intradermal HSV-1 titer falls below the limit of detection, the estimated trough plasma concentration of ASP2151 is approximately 100 ng/ml at both the 30 mg/kg/day q8h and 100 mg/kg/day q12h dosing regimens.

Safety[1] Adverse events were coded using the MedDRA (Medical Terminology Reference Intake). The overall incidence of adverse events was similar across treatment groups (range: 45.4%–46.6%). The proportions of patients experiencing drug-related adverse events were 10.0% (25/249), 10.7% (27/252), and 12.0% (30/249) in the Amenamevir 400 mg, 200 mg, and valacyclovir groups, respectively. Adverse events with an incidence of ≥2% in each group included: nasopharyngitis, elevated β-N-acetyl-D-glucosidase, elevated fibrin degradation products, elevated α-1-microglobulin, stomatitis, proteinuria, contact dermatitis, diabetes, eczema, diarrhea, headache, and folliculitis (Table 4). Drug-related adverse events occurring in ≥2% of patients included: elevated fibrin degradation products in 2.0% (5/249) of the Amenamevir 400 mg group and 2.4% (6/249) of the valacyclovir group; and elevated α1-microglobulin in 2.4% (6/252) of the Amenamevir 200 mg group. Most adverse events were mild, and no serious adverse events were observed among the drug-related adverse events (Table S4). No deaths were reported in this study. A total of 6 serious adverse events (SAEs) were reported in 5 patients: 1 in the Amenamevir 400 mg group (infectious mononucleosis), 1 in the Amenamevir 200 mg group (angina pectoris), and 3 in the valacyclovir group (loss of consciousness, embolic stroke, malignant lung tumor, and tendon rupture). All serious adverse events were considered unrelated to the study drug. One patient in the Amenamevir 200 mg group (headache and nausea) discontinued study treatment due to adverse events, and two patients in the valacyclovir group (abdominal pain, abnormal liver function, and encephalopathy) discontinued study treatment due to adverse events. All adverse events were drug-related, and all were mild except for moderate encephalopathy. All adverse events resolved with adequate treatment and discontinuation of the study drug. No significant changes were observed in clinical laboratory tests (hematology, biochemistry, and urinalysis), vital signs, or electrocardiograms.

[1]. J Dermatol.2017 Nov;44(11):1219-1227.

[2]. Antimicrob Agents Chemother.2013 Mar;57(3):1339-46.

[3]. J Antimicrob Chemother. 2010 Aug;65(8):1733-41.

Amenamevir has been used in clinical trials to investigate the treatment and safety of herpes zoster, herpes simplex, and genital herpes. Amenamevir is a novel helicase-primase inhibitor effective against varicella-zoster virus and herpes simplex virus types 1 and 2. Amenamevir stabilizes the interaction between the helicase-primase and its DNA substrate, preventing the helicase or primase-catalyzed cycle, thereby interfering with viral DNA replication and viral proliferation. ASP2151 (Amenamevir) is a helicase-primase inhibitor targeting herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus. To determine and analyze the correlation between the pharmacodynamic (PD) and pharmacokinetic (PK) parameters of ASP2151, we investigated the PD characteristics of ASP2151 using an in vitro plaque reduction assay and an HSV-1-infected mouse model. ASP2151 inhibits HSV-1 replication in vitro, with a mean half-maximal effective concentration (EC50) of 14 ng/ml. In a mouse model of skin infection with HSV-1, ASP2151 dose-dependently inhibited intradermal HSV-1 growth, reaching a plateau at a dose of 30 mg/kg body weight/day. Dose-split studies showed that twice-daily administration of 100 mg/kg body weight/day of ASP2151, as well as three-daily administrations of 30 or 100 mg/kg body weight/day of ASP2151, resulted in intradermal HSV-1 titers below the limit of detection in mice. Intradermal HSV-1 titers were correlated with the maximum serum drug concentration (Cmax), the area under the 24-hour concentration-time curve (AUC24h), and the time to plasma ASP2151 concentration above 100 ng/ml (T100). In mice with plasma ASP2151 concentrations of 79 to 145 ng/ml, continuous infusion of ASP2151 effectively reduced intradermal HSV-1 titers to below the detection limit. Our results indicate that the antiviral efficacy of ASP2151 in HSV-1-infected mice is closely related to the pharmacokinetic parameter T₁₀₀. Based on these results, we propose that maintaining plasma ASP2151 concentrations above 100 ng/ml daily for 21 to 24 hours in HSV-1-infected mice can achieve optimal efficacy. [2]

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Objective
To evaluate and describe the antiherpesvirus activity of ASP2151 (amenavir), a novel non-nucleoside helicase-primase complex inhibitor containing oxadiazolylphenyl.
Methods
The inhibitory effect of ASP2151 on the activity of recombinant HSV-1 helicase-primase complex-related enzymes was evaluated. To investigate its effect on viral DNA replication, we analyzed viral DNA in cells infected with herpesviruses [herpes simplex virus (HSV), varicella-zoster virus (VZV), and human cytomegalovirus]. Sequencing analysis was performed on VZV mutants resistant to ASP2151. In vitro and in vivo antiviral activity was evaluated using plaque reduction assays and a mouse herpes zoster-like spread model infected with HSV-1.
Results
ASP2151 inhibited the activities of single-stranded DNA-dependent ATPase, helicase, and primase associated with the HSV-1 helicase-primase complex. Antiviral assays showed that, unlike other known HSV helicase-primase inhibitors, ASP2151 was equally effective against VZV, HSV-1, and HSV-2 by inhibiting viral DNA replication. In addition, the anti-VZV activity of ASP2151 (EC50, 0.038–0.10 µM) was stronger than that of acyclovir (EC50, 1.3–27 µM) against all tested strains. ASP2151 was also effective against acyclovir-resistant VZV. Amino acid substitutions were found in the helicase and primase subunits of ASP2151-resistant VZV. In a mouse model of herpes zoster-like spread, ASP2151 was orally active and more effective than valacyclovir in inhibiting disease progression. Conclusion ASP2151 is a novel herpes helicase-primase inhibitor worthy of further investigation for the treatment of varicella-zoster virus (VZV) and herpes simplex virus (HSV) infections. [3]

C24H26N4O5S

482.55

482.162

C, 59.74; H, 5.43; N, 11.61; O, 16.58; S, 6.64

841301-32-4

1039623-01-2 (LB-80380 maleate)

11397521

White to off-white solid powder

4.303

1

7

6

34

800

0

O=C(CN(C1C(C)=CC=CC=1C)C(C1CCS(=O)(=O)CC1)=O)NC1C=CC(C2N=CON=2)=CC=1

MNHNIVNAFBSLLX-UHFFFAOYSA-N

InChI=1S/C24H26N4O5S/c1-16-4-3-5-17(2)22(16)28(24(30)19-10-12-34(31,32)13-11-19)14-21(29)26-20-8-6-18(7-9-20)23-25-15-33-27-23/h3-9,15,19H,10-14H2,1-2H3,(H,26,29)

N-(2-((4-(1,2,4-oxadiazol-3-yl)phenyl)amino)-2-oxoethyl)-N-(2,6-dimethylphenyl)tetrahydro-2H-thiopyran-4-carboxamide 1,1-dioxide

ASP-2151; ASP2151; Amenamevir; 841301-32-4; Amenamevir [INN]; 94X46KW4AE; AMENAMEVIR [MI]; ASP 2151

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : 50~96 mg/mL ( 103.62~198.94 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.31 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (4.31 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (4.31 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 10% DMSO+40% PEG300+5% Tween-80+45% Saline: ≥ 2.08 mg/mL (4.31 mM)

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 (Please use freshly prepared in vivo formulations for optimal results.)