genotype 1 HCV NS3-4A protease (Ki = 7 nM)

Telaprevir inhibits the NS3-4A serine protease of the hepatitis C virus, which stops the virus's ability to process polyproteins. This, in turn, causes a time- and dose-dependent decrease in viral RNA replication, total HCV RNA levels, and protein levels in Con1 (genotype 1b) subgenomic HCV replicon cells. Telaprevir exhibits a noteworthy increase in inhibitory effect on HCV RNA replication over time, with IC50 values for 24, 48, 72, and 120 hours of incubation, respectively, of 0.574 μM, 0.488 μM, 0.210 μM, and 0.139 μM. Three separate experiments using a 48-hour incubation period show that telaprevir has an average IC50 of 0.354 μM and an average IC90 of 0.830 μM, respectively. Telaprevir has no appreciable cytotoxicity against HepG2, parental Huh-7, or HCV replicon cells after 48 hours of incubation. After incubating for 13 days without any rebound, replicon cells are completely free of HCV RNA when telaprevir (17.5 μM) is withdrawn. In comparison to treatment with each agent alone, telaprevir and IFN-α exhibit an additive to moderate synergistic effect on suppression of resistance mutations and reduction of HCV RNA replication without a discernible increase in cytotoxicity.[1]

In the mice model, oral telaprevir administration decreases HCV protease-dependent cleavage and subsequent liver-secreted SEAP into the blood to 18.7% and 18.4% at dosages of 10 and 25 mg/kg, respectively. [/2] In HCV-infected human hepatocyte chimeric mice with genotype 1b, administration of Telaprevir at 200 mg/kg for one week causes a 1.9 log reduction in HCV RNA; when treatment is combined with MK-0608 (50 mg/kg) for four weeks, viruses are eradicated from the mice.[3]

Stable Huh-7 cells containing the self-replicating, subgenomic HCV replicon, which is identical in sequence to the I377neo/NS3-3'/wt replicon are used for anti-HCV assays. Telaprevir serially diluted in DMEM plus 2% FBS and 0.5% dimethyl sulfoxide (DMSO) is incubated with replica cells at 37 °C for the specified amount of time. Using an RNeasy-96 kit, total cellular RNA is extracted, and a quantitative real-time polymerase chain reaction (QRT-PCR) assay is used to determine the copy number of HCV RNA in order to assess the 50% inhibitory concentration (IC50).

Evaluating Telaprevir (VX-950) or IFN-α in HCV replicon cells involves determining its IC50, IC90, and CC50. To sum up, 96-well plates are plated with 1×10⁴ replicon cells each well. Using antiviral agents serially diluted in DMEM plus 2% FBS and 0.5% DMSO, replicon cells are incubated at 37°C for the specified amount of time on the following day. With an RNeasy-96 kit, total cellular RNA is extracted, and a quantitative RT-PCR (QRT-PCR) assay is used to calculate the copy number of HCV RNA. The mean of five replicates in cell culture is represented by each datum point. A tetrazolium (MTS)-based cell viability assay is used to measure the cytotoxicity of Telaprevir under the same experimental conditions. One million parental Huh-7 cells or four million HepG2 cells per well are used in the cytotoxicity assay using human hepatocyte cell lines. In order to assess the cytotoxicity of Telaprevir against resting peripheral blood monoclonal cells, 1×10⁵ cells per well are cultured with Telaprevir in RPMI-1640 medium (without serum) for 48 hours, after which the MTS-based assay is used to determine the cell viability. Precoated with anti-human CD3 antibody, a 96-well plate is filled with 1×10⁵ cells per well in RPMI-1640 medium to test the cytotoxicity of VX-950 against proliferating PBMC. The cells are cultured for 72 hours at 37°C with Telaprevir and anti-human CD28 antibody. The [³H]thymidine update is used to measure the cell growth between the 48th and 72nd hours[1].

Mice: Recombinant adenovirus Ad-WT-HCVpro-SEAP, with 10⁹ IFU per mouse, is injected via the tail vein into five groups of six-week-old SCID mice (six animals per group). Two oral doses of Telaprevir (VX-950) at a dose of 10, 25, 75, 150, or 300 mg/kg are administered to each group of mice. First dose of Telaprevir is administered two hours prior to adenovirus injection; second dose is administered ten hours following injection. A second set of ten mice is given the vehicle on its own. Serum samples are taken 24 hours after injection, and the SEAP activity in each group administered with Telaprevir is contrasted with the vehicle group's. Rat and Canine Rats and dogs are used to assess the oral and intravenous pharmacokinetics of telaprevir (VX-950). One intravenous bolus dose of 0.95 mg/kg Telaprevir is given intravenously to three male Sprague-Dawley rats weighing 250–300 g. Heparinized tubes are used to collect serial blood samples prior to dosage administration and at intervals of 0.083, 0.167, 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, and 8 hours following the dose. Telaprevir in 10% ethanol, 40% polyethylene glycol 400, and 50% D5W is given intravenously as a bolus dose to three male beagle dogs (8–12 kg). Heparinized tubes are used to collect serial blood samples prior to dosage administration as well as at 0.083, 0.167, 0.25, 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 hours later. Telaprevir is formulated in polyvinylpyrrolidone (PVP) K-30 plus 2% sodium lauryl sulfate and dosed as an oral gavage for oral studies in rats and dogs. Oral dosages of 40 mg/kg VX-950 are given to three male Sprague-Dawley rats (250–300 g) and 9.6 mg/kg VX-950 are given to four male Beagle dogs (10.9–12.0 kg). Blood samples are obtained before dosage administration and at 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours following dose administration in both oral studies. Plasma samples are obtained by centrifugation and kept at -70°C until analysis in both intravenous and oral studies. Samples from the oral studies are analyzed using an achiral LC/MS/MS method, while samples from the intravenous studies are analyzed using a chiral liquid chromatography followed by tandem mass spectrometry (LC/MS/MS) method.

Absorption, Distribution and Excretion
Telaprevir reaches peak plasma concentration 4-5hours after administration. Absolute bioavailability has not been determined. When taken with a normal fat meal (21g of fat), exposure increases by 235% compared to fasting conditions. With low (3.6g of fat) and high fat (56g of fat) meals, exposure increased 117% and 330% respectively.
Telaprevir is mainly eliminated in the feces (82%) with a smaller amount eliminated via expiration (9%) and very little in the urine (1%). 31.9% and 18.8% of drug in the feces was present as the parent compound and R-diastereomer of the parent compound respectively.
The estimated apparent volume of distribution for Telapravir is 252 litres with an inter-individual variability of 72%.
Telaprevir has an estimated aparent total body clearance of 32.4 liters per hour with an interindividual variability of 27.2%.
The pharmacokinetic properties of telaprevir have been evaluated in healthy adult subjects and in subjects with chronic hepatitis C. Following multiple doses of telaprevir (750 mg every 8 hr) in combination with peginterferon alfa and ribavirin in treatment-naive subjects with genotype 1 chronic hepatitis C, mean (SD) Cmax was 3510 (1280) ng/mL, Cmin was 2030 (930) ng/mL, and AUC8h was 22,300 (8650) ng.hr/mL.
Telaprevir is orally available, most likely absorbed in the small intestine, with no evidence for absorption in the colon. Maximum plasma concentrations after a single dose of telaprevir are generally achieved after 4 to 5 hours.
Telaprevir is a substrate for and inhibitor of P-glycoprotein transport.
The systemic exposure (AUC) to telaprevir was increased by 237% when telaprevir was administered with a standard fat meal (containing 533 kcal and 21 g fat) compared to when telaprevir was administered under fasting conditions. In addition, the type of meal significantly affects exposure to telaprevir. Relative to fasting, when telaprevir was administered with a low-fat meal (249 kcal, 3.6 g fat) and a high-fat meal (928 kcal, 56 g fat), the systemic exposure (AUC) to telaprevir was increased by approximately 117% and 330%, respectively.
For more Absorption, Distribution and Excretion (Complete) data for Telaprevir (13 total), please visit the HSDB record page.

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Metabolism / Metabolites
Telaprevir is extensively metabolized via hydrolysis, oxidation, and reduction. The major metabolites of Telaprevir are pyrazinoic acid, a metabolite that underwent reduction at the α-ketoamide bond, and the R-diastereomer of telaprevir which is 30-fold less active than the parent compound were found to be the predominant metabolites. The primary enzyme involved in the metabolism of Telaprevir is CYP3A4. Some metabolism is performed by aldo-keto reductases and other reductases.
Telaprevir is extensively metabolized in the liver, involving hydrolysis, oxidation, and reduction. Multiple metabolites were detected in feces, plasma, and urine. After repeated oral administration, the R-diastereomer of telaprevir (30-fold less active), pyrazinoic acid, and a metabolite that underwent reduction at the alpha-ketoamide bond of telaprevir (not active) were found to be the predominant metabolites of telaprevir.

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Biological Half-Life
Telaprevir has a half-life of elimination of 4.0-4.7 hours after a single dose and an effective half life of 9-11 hours at steady state.
The mean elimination half-life after single-dose oral administration of telaprevir 750 mg typically ranged from about 4.0 to 4.7 hours. At steady state, the effective half-life is about 9 to 11 hours.

Hepatotoxicity
In large randomized controlled trials, triple therapy with telaprevir, peginterferon and ribavirin was associated with a high rate of adverse events that often required dose adjustments and led to early discontinuation in 5% to 20% of patients. However, serum ALT elevations and clinically apparent liver injury were not generally mentioned as adverse events of therapy. Telaprevir, however, was associated with a high rate of rash, which was sometimes associated with features of hypersensitivity, including rare instances of DRESS and Stevens Johnson syndrome. These severe cutaneous reactions are often accompanied by laboratory evidence of hepatic injury (ALT and alkaline phosphatase elevations). In reported cases, however, the rash and other features of hypersensitivity typically overshadowed the hepatic injury and none were reported to be associated with jaundice.
Another rare but severe hepatic complications of telaprevir therapy occurs in patients with advanced fibrosis or cirrhosis, among whom de novo, seemingly spontaneous hepatic decompensation occurred in a proportion of treated subjects. Decompensation was particularly common in patients with advanced fibrosis or cirrhosis with a previous history of decompensation. The cause of the decompensation was not clear and the separate role of telaprevir in contrast to peginterferon and ribavirin could not be defined. Nevertheless, in postmarketing studies of triple therapy of chronic hepatitis C with cirrhosis, decompensation was reported in 2% to 8% of patients, and deaths from hepatic failure in 1% to 3%.
Likelihood score for the combination of telaprevir, peginterferon and ribavirin: B (likely cause of liver injury and hepatic decompensation in patients with preexisting cirrhosis or advanced fibrosis).

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Telaprevir is no longer marketed in the United States and has not been studied in nursing mothers. Because it must be used with ribavirin and peginterferon alfa, it is not considered a good choice during breastfeeding. When it was marketed, the manufacturer recommended that mothers taking telaprevir not breastfeed their infants.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

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Protein Binding
Telapravir is 59-76% bound to human plasma proteins following a single dose. It binds to both human serum albumin and α1-acid glycoprotein.

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Interactions
Telaprevir is a strong inhibitor of CYP3A. Telaprevir is contraindicated when combined with drugs that are highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events (narrow therapeutic index). Telaprevir is contraindicated when combined with drugs that strongly induce CYP3A and thus may lead to lower exposure and loss of efficacy of telaprevir.
Potential pharmacokinetic interaction with drugs that are inducers or inhibitors of P-glycoprotein, with possible alteration in telaprevir concentrations.
Potential pharmacokinetic interaction with alfuzosin (increased alfuzosin concentrations). Concomitant use of telaprevir and alfuzosin is contraindicated because increased alfuzosin concentrations may result in hypotension or cardiac arrhythmia.
Potential pharmacokinetic interaction with antiarrhythmic agents (amiodarone, bepridil (no longer commercially available in US), flecainide, systemic lidocaine, propafenone, quinidine) may result in increased concentrations of the antiarrhythmic agent; potential for serious and/or life-threatening adverse effects. If telaprevir and antiarrhythmic agents are used concomitantly, use caution and clinical monitoring.
For more Interactions (Complete) data for Telaprevir (54 total), please visit the HSDB record page.

[1]. Antimicrob Agents Chemother . 2006 May;50(5):1813-22.

[2]. Antimicrob Agents Chemother . 2006 Mar;50(3):899-909.

[3]. J Hepatol . 2011 May;54(5):872-8.

Therapeutic Uses
Oligopeptides
INCIVEK (telaprevir), in combination with peginterferon alfa and ribavirin, is indicated for the treatment of genotype 1 chronic hepatitis C in adult patients with compensated liver disease, including cirrhosis, who are treatment-naive or who have previously been treated with interferon-based treatment, including prior null responders, partial responders, and relapsers. /Included in US product label/

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Drug Warnings
Fatal and non-fatal serious skin reactions, including Stevens Johnson Syndrome (SJS), Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), and Toxic Epidermal Necrolysis (TEN), have been reported in patients treated with INCIVEK combination treatment. Fatal cases have been reported in patients with progressive rash and systemic symptoms who continued to receive INCIVEK combination treatment after a serious skin reaction was identified. For serious skin reactions, including rash with systemic symptoms or a progressive severe rash, INCIVEK, peginterferon alfa, and ribavirin must be discontinued immediately. Discontinuing other medications known to be associated with serious skin reactions should be considered. Patients should be promptly referred for urgent medical care.
Rash developed in 56% of patients receiving telaprevir during controlled clinical trials. Severe rash (e.g., generalized rash or rash with vesicles or bullae or ulcerations other than SJS) was reported in 4% of patients receiving telaprevir in conjunction with peginterferon alfa and ribavirin compared with less than 1% of patients receiving peginterferon alfa and ribavirin without telaprevir. Rash frequently was observed during the first 4 weeks of telaprevir treatment, but can occur at any time. Rash generally improves when telaprevir therapy is completed or discontinued; complete resolution may take weeks.
If a serious skin reaction occurs, telaprevir, peginterferon alfa, and ribavirin should be immediately discontinued and the patient promptly referred for urgent medical care. Patients with mild to moderate rash should be monitored for progression of rash or development of systemic symptoms. If rash progresses and becomes severe or if systemic symptoms develop, telaprevir should be discontinued; peginterferon alfa and ribavirin may be continued.
Telaprevir dosage should not be reduced and telaprevir should not be restarted if it was discontinued because of rash. If improvement is not observed within 7 days of discontinuing telaprevir, sequential or simultaneous interruption or discontinuance of peginterferon alfa and/or ribavirin should be considered. If medically indicated, earlier interruption or discontinuance of peginterferon alfa and ribavirin should be considered.
For more Drug Warnings (Complete) data for Telaprevir (18 total), please visit the HSDB record page.

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Pharmacodynamics
Telaprevir is classified as a direct-acting antiviral (DAA) and prevents viral replication in HCV genotype 1.

C36H53N7O6

679.85

679.405

C, 63.60; H, 7.86; N, 14.42; O, 14.12

402957-28-2

Telaprevir-d4

3010818

White to off-white solid powder

1.3±0.1 g/cm3

1.584

3.93

4

8

14

49

1240

6

O=C(N([C@@H]1C(N[C@H](C(C(NC2CC2)=O)=O)CCC)=O)C[C@@]3(CCC[C@@]31[H])[H])[C@@H](NC([C@@H](NC(C4=NC=CN=C4)=O)C5CCCCC5)=O)C(C)(C)C

BBAWEDCPNXPBQM-GDEBMMAJSA-N

InChI=1S/C36H53N7O6/c1-5-10-25(29(44)34(48)39-23-15-16-23)40-33(47)28-24-14-9-13-22(24)20-43(28)35(49)30(36(2,3)4)42-32(46)27(21-11-7-6-8-12-21)41-31(45)26-19-37-17-18-38-26/h17-19,21-25,27-28,30H,5-16,20H2,1-4H3,(H,39,48)(H,40,47)(H,41,45)(H,42,46)/t22-,24-,25-,27-,28-,30+/m0/s1

(3S,3aS,6aR)-2-[(2S)-2-[[(2S)-2-cyclohexyl-2-(pyrazine-2-carbonylamino)acetyl]amino]-3,3-dimethylbutanoyl]-N-[(3S)-1-(cyclopropylamino)-1,2-dioxohexan-3-yl]-3,3a,4,5,6,6a-hexahydro-1H-cyclopenta[c]pyrrole-3-carboxamide

VX-950; LY-570310; MP-424; VX950; LY570310; MP424; VX 950; LY 570310; MP 424; trade names: Incivek; Incivo

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)

Solubility in Formulation 1: ≥ 2.5 mg/mL (3.68 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 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 2: 30% PEG400+0.5% Tween80+5% propylene glycol: 30 mg/mL

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