HCV nonstructural 5B protein (NS5B); RNA-dependent RNA polymerase (RdRp)

Filibuvir (0.01-10000 nM; 48 h)has a dose-dependent inhibitory effect on the WT 1b replicon, with an EC50 of about 70 nM in Huh7.5 cells that carry the HCV replicon. The HCV polymerase and filibuvir have a 29 nM dissociation constant[2].
Filibuvir inhibits RNA synthesis more preferentially through elongative inhibition as opposed to de novo initiation. With an IC50 of 73 nM, filibuvir reduces primer extension from PE46 but has no discernible effect on de novo-initiated RNA synthesis (IC50=∼5 μM)[2].

More effective and better-tolerated therapies are needed for chronic hepatitis C virus (HCV) infection. Among the direct-acting anti-HCV agents in development is the nonstructural 5B protein (NS5B polymerase) non-nucleoside inhibitor filibuvir. We investigated the antiviral activity, pharmacokinetics, safety, and tolerability of multiple doses of filibuvir in treatment-naive and treatment-experienced patients who were chronically infected with HCV genotype 1 in two phase 1b clinical studies (study 1 was a randomized, placebo-controlled dose escalation study and study 2 was a nonrandomized, open-label study). The filibuvir doses evaluated ranged from 200-1400 mg daily, and the duration of dosing ranged from 3-10 days. Genotypic changes in the NS5B nucleotide sequence following short-term filibuvir therapy were also assessed. Filibuvir potently inhibited viral replication in a dose-dependent manner. Mean maximum HCV RNA change from baseline ranged from -0.97 log(10) IU/mL with filibuvir given at 100 mg twice daily to -2.30 log(10) IU/mL with filibuvir given at 700 mg twice daily in treatment-naive patients. In treatment-experienced patients, an HCV RNA reduction of 2.20 log(10) IU/mL was achieved with filibuvir given at 450 mg twice daily. Filibuvir was well tolerated in both studies. Adverse events were mild or moderate in severity. No discontinuations, serious adverse events, or deaths were reported. NS5B sequencing identified residue 423 as the predominant site of mutation after filibuvir dosing. Conclusion: Filibuvir administration resulted in significant reductions in HCV RNA concentrations at doses that were well tolerated in patients infected with HCV genotype 1. Filibuvir is currently being evaluated in combination with pegylated interferon alfa 2a plus ribavirin in treatment-naive patients [1].

Surface plasmon resonance. [2]
All analyte binding experiments were performed with a Biacore T100 instrument using preconditioned CM5 sensor chips activated with N-hydroxysuccinimide ester and 1-ethyl-3(3-diaminopropyl) carbodiimide hydrochloride. The 1bΔ21 NS5B protein and variants were immobilized after a 5-min injection to a nominal density of about 9,000 response units. The surface was then deactivated by injection of ethanolamine for 7 min. Compounds were injected in a buffer containing 25 mM HEPES (pH 7.4), 10 mM MgCl2, 150 mM NaCl, 0.01% Tween 20, 0.05% β-mercaptoethanol, and 5% DMSO. All compounds displayed saturable 1:1 binding behavior. For competition binding, the experimental design consisted of injecting a saturating concentration of the first analyte (160 nM filibuvir) followed by immediate injection of an equimolar ratio of the analyte mixture (160 nM filibuvir plus 160 nM VX-222 or ANA-598).

[1]. Antiviral activity of the hepatitis C virus polymerase inhibitor filibuvir in genotype 1-infected patients. Hepatology. 2011 Jul;54(1):50-9.

[2]. Biochemical study of the comparative inhibition of hepatitis C virus RNA polymerase by VX-222 and filibuvir. Antimicrob Agents Chemother. 2012 Feb;56(2):830-7.

Filibuvir is a member of triazolopyrimidines.
Filibuvir has been used in trials studying the treatment of Hepatitis, Hepatitis C, and Chronic Hepatitis C.
Filibuvir is a non-nucleoside polymerase inhibitor of the hepatitis C virus NS5B RNA-dependent RNA polymerase. Filibuvir binds to the non-catalytic Thumb 2 site on viral polymerase and causes a decrease in viral RNA synthesis.

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Researchers characterized the interaction of filibuvir and VX-222 with the thumb II pocket of the HCV polymerase and determined their effects on 1b/Con1 replicons as well as the polymerase activity. Both filibuvir and VX-222 have binding affinities (Kds) for the HCV polymerase in the nanomolar range, with rapid on rates and relatively slow off rates. In the crystal structure of the filibuvir-polymerase complex, L419 and I482 interact with the pyridine group, while M423 interacts with the cyclopentyl portion of the lactone. Our results show that the latter interaction is more important for stable binding by filibuvir. For VX-222, the crystal structure of the complex is not known, but all three residues we examined contributed to interaction with VX-222. We note that L412, M423, and I482 all help to form a hydrophobic surface within the thumb II domain, and it is likely that they interact hydrophobically with VX-222, likely with the 4-methy-cyclohexanoyl group.
Studies with inhibitors have demonstrated that the thumb subdomain has an important role in regulating the mode of RNA synthesis. Benzimidazole-based compounds that bind to the thumb I pocket likely affect the interaction between the Δ1 loop and the thumb subdomain to prevent de novo-initiated RNA synthesis. Chinnaswamy et al. previously showed that a substitution in the thumb I subdomain can affect the interaction between subunits of the polymerase that are needed for de novo-initiated RNA synthesis. The results here with filibuvir and VX-222 and those of Le Pogam et al. with thiophene-based compounds consistently reveal an inhibitory effect on the ability of the HCV polymerase to extend from a primed template. It is quite likely that the thumb region of the polymerase is involved in conformational changes and/or oligomerization states of the HCV polymerase that could regulate the activities of the polymerase, as proposed by Wang et al. Furthermore, VX-222 and filibuvir likely interfere with the required conformational changes required for elongative RNA synthesis. DSF results did show a significant change in polymerase stability indicative of a conformational change (Fig. 4), but additional structural and functional analyses are needed to define the polymerase conformation(s) that could facilitate de novo-initiated or elongative RNA synthesis.[2]

C29H37N5O3

503.647

503.29

C, 69.16; H, 7.41; N, 13.91; O, 9.53

877130-28-4

54708673

White to off-white solid powder

1.29g/cm3

5.124

1

7

8

37

833

1

C([C@]1(OC(=O)C(CC2N=C3N=C(C=C(N3N=2)C)C)=C(O)C1)C1CCCC1)CC1C=C(CC)N=C(CC)C=1

SLVAPEZTBDBAPI-GDLZYMKVSA-N

InChI=1S/C29H37N5O3/c1-5-22-14-20(15-23(6-2)31-22)11-12-29(21-9-7-8-10-21)17-25(35)24(27(36)37-29)16-26-32-28-30-18(3)13-19(4)34(28)33-26/h13-15,21,35H,5-12,16-17H2,1-4H3/t29-/m1/s1

(2R)-2-cyclopentyl-2-[2-(2,6-diethylpyridin-4-yl)ethyl]-5-[(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)methyl]-4-hydroxy-3H-pyran-6-one

P 00868554; PF 868554; PF-00868554; PF868554; Filibuvir; 877130-28-4; PF-00868554; (R)-6-Cyclopentyl-6-[2-(2,6-diethylpyridin-4-yl)ethyl]-3-[(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)methyl]-4-hydroxy-5,6-dihydro-2H-pyran-2-one; (R)-6-Cyclopentyl-6-(2-(2,6-diethylpyridin-4-yl)ethyl)-3-((5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)methyl)-4-hydroxy-5,6-dihydro-2H-pyran-2-one; 198J479Y2L; (2R)-2-cyclopentyl-2-[2-(2,6-diethylpyridin-4-yl)ethyl]-5-[(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)methyl]-4-hydroxy-3H-pyran-6-one; 2H-Pyran-2-one, 6-cyclopentyl-6-(2-(2,6-diethyl-4-pyridinyl)ethyl)-3-((5,7-dimethyl(1,2,4)triazolo(1,5-a)pyrimidin-2-yl)methyl)-5,6-dihydro-4-hydroxy-, (6R)-; PF00868554; PF-868554; Filibuvir

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)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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