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HCV-796 Displays Potent Antiviral Activity in Replicon and in Chimeric Mice Infected with Hepatitis C Virus (HCV)
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Reported by Jules Levin
ICAAC
San Francisco, Sept 27-30, 2006
There are abstracts on several new HCV drugs at ICAAC. Today, there is a poster on MK-0608, a promising HCV nucleoside, which showed potency in 7-day study results in chimps reported at the HIV Drug Resistance Workshop this Summer. Although the poster will be displayed today a summary was printed in the abstract book showing results of 37 days of therapy in chimps, and the results are very good. I will report the poster results later today afyer viewing it in about 1 hour. Also presented at this meeting were posters on HCV polymerase inhibitors in development by Roche and Abbott. R1626 is the Roche polymerase inhibitor for which study results in patients were reporred this Spring showing a 1.2 log reduction in patients after 14 days of monotherapy. Further study results will be reported at AASLD. Abbott is in pre-clinical development for a HCV drug.
A. Y. M. HOWE1, N. M. KNETEMAN 2,3, T. GAO 2, J. LEWIS 3, M. COLLETT 4, D. PEVEAR 4, D. L. J. TYRRELL 2,3, J. F. O'CONNELL 1;
1Wyeth Res., Collegeville, PA, 2KMT Hepatech, Inc., Edmonton, Canada, 3Univ. of Alberta, Edmonton, Canada, 4ViroPharma, Inc., Exton, PA.
HCV-796, a non-nucleoside HCV polymerase inhibitor, demonstrates potent antiviral activity in vitro and in a small animal model of HCV replication.
Introduction
Since the initial report of its development (1), the SCID/beige-Alb/uPA human hepatocyte chimeric mouse model, infected with hepatitis C virus, has been successfully employed to test a number of anti-viral compounds, including interferon a-2b, the NS3 protease inhibitor BILN-2061 and the NS5B polymerase inhibitor HCV-371 (2). Results obtained from the mouse model have successfully predicted outcomes from human clinical trials, both for positive (BILN-2061) and negative (HCV-371) outcomes.
HCV-796, an orally dosed hepatitis C viral polymerase inhibitor developed from a different chemical series than HCV-371, has now been evaluated in in vitro and in vivo studies for anti-viral activity.
The following studies were carried out with the animal model system and biochemical assays:
--RNA dependent RNA polymerase inhibition assays and subgenomic replicon assays (study 1)
--a pilot, proof-of-concept study of the anti-viral activity of HCV-796 at one dose in HCV infected chimeric mice (study 2)
--assessment in infected chimeric mice of the antiviral activity of HCV-796 compared to IFN a-2b or vehicle control (study 3)
--assessment in infected chimeric mice of the antiviral activities of HCV-796 or IFN a-2b alone or in combination with each other (study 4)
STUDY 1: In Vitro activity profile of HCV-796
In vitro antiviral activity was evaluated in HCV replicon cells. Polymerase inhibition assays revealed an IC50 of 0.01 - 0.16 uM for genotype 1 and 0.22 - 1.7 uM for genotype 2, 3 and 4. In an in vitro subgenomic replicon assay, HCV=796 specifically reduced steady state levels of HCV RNA with IC50s of 5nM & 9 nM against genotypes 1a and 1b (Therapeutic Index >1100) and also reduced HCV protein. In the 1a replicon assay, HCV-796 reduced HCV RNA levels 3-4 log10 HCV copies/_g total RNA (EC50=4.5nM).
Study 2 design: Pilot study of HCV-796 anti-viral activity in chimeric mice
dose: 50 mg/kg/dose
administration: 3 times a day, oral
course: 5 days treatment
study animals: HCV-796: 6. Control: 6
Assays: hAAT for monitoring human hepatocyte grafts, Taqman ABI 7300 real time PCR for HCV RNA quantification.
RESULTS
--mean serum HCV viral RNA decreased by 2.02 +/- 0.55 log after 5 days therapy in HCV-796 treatment group
--HCV viral RNA level remained stable in vehicle control (3.94 +/- 0.8 to 3.71 +/- 1.0)
--A significant difference in the net decrease of HCV viral RNA existed between HCV-796 and vehicle control (p=0.01, two-sided (unpaired) t-test).
Study 3 design: Effect of polymerase inhibitor HCV-796 and IFN on HCV titer in chimeric mice
Dose: HCV-796 50/mg/kg per dose
Interferon a-2b (IFN): 1350 IU/gm/day
Administration: HCV-796 and vehicle 3 times per day by oral gavage; IFN once per day i.m.
Course: 10 days treatment
Study animals: 5 each of HCV-796, IFN and vehicle control groups
Assays: hAAT for monitoring human hepatocyte grafts; Taqman ABI 7300 real time PCR for HCV RNA quantification
RESULTS
--mean HCV viral RNA decreased 1.78 +/- 0.27 log after 10 day treatment course with HCV-796 versus 0.35 +/- log decrease in vehicle control (p=0.009)
--mean HCV viral RNA decreased 1.11 +/- 0.2 log after 10 days treatment with IFNa-2b (p=0.04 vs vehicle control)
--HCV viral titer rebounded in all HCV-796 treated animals following end of treatment (data not shown
Study 4 design: HCV-796 and Interferon a-2b combination study in chimeric mice
Dose: HCV-796 30/mg/kg/dose alone or combined with 1350 IU/gm IFN
Administration: HCV-796 3 doses daily by oral gavage; IFN daily i.m.
Course: 18 days treatment
Study animals: HCV-796: 7; IFN: 7, IFN+hCV-796 combination: 8; vehicle control: 7
Assays: hAAT for monitoring human hepatocyte grafts, Taqman ABI 7300 real time PCR for HCV quantification
RESULTS
--On day 11, mean serum HCV viral NA decreased by 0.66 +/-0.16 log )HCV-796 30 mg/kg, p=0.013), 1.35 +/- 0.14 log (IFN 1350 IU/gm, p=0.0001), and 2.44 +/- 0.23 (IFN + HCV-796 combination, p=0.0001) versus 0.12 +/- 0.22 increase in vehicle control after 10 days of treatment
--Serum HCV viral RNA titer reduction after 10 days of therapy was significantly greater in the combination group compared to the grouos receiving IFN or HCV-796 alone (p<0.05)
In the SCID mouse model, mean plasma concentrations at 8 hr after a single dose and dosing for 5 days with 50 mg/kg were 5- and 12-fold, respectively, above replicon EC50 (t1/2=2hr).
The specific antiviral activity of HCV-796 is further confirmed by the viral rebound to baseline within 1 week of stopping treatment.
The authors summarized: HCV-796 represents a potential antiviral for the treatment of HCV infection in humans. HCV-796, a novel non-nucleoside inhibitor of the hepatitis C virus RNA-dependent RNA polymerase, demonstrated specific polymerase activity with IC50 values of 0.01 - 0.16 uM against genotype 1 and IC50 values of 0.22 to 1,7 uM against genotype 2, 3, and 4 enzymes. The compound also exhibited high activity in replicon systems and multiple treatments of genotype 1b replicon cells yielded a 3 to 4 log reduction in HCV viral RNA levels. The in vitro activity paralled in vivo results obtained with the HCV-infected chimeric mouse model. The mean HCV viral load in mice was reduced by 1.78 to 1.88 log after 5 to 10 days therapy with 50 mg/kg dose of HCV-796 compared to a mean 1.11 log decrease obtained with interferon a-2b treatment for 10 days. The combination of 30 mg/kg HCV-796 with interferon a-2b (1350IU/gm/day) resulted in a mean 2.44 log decrease in HCV viral RNA which was significantly greater than the decrease obtained with either HCV-796 or interferon a-2b alone (0.66 or 1.35 log, respectively; p<0.05).
This small animal model has previously proven predictive of clinical treatment impact for antiviral compounds for HCV as demonstrated by positive outcomes in the mouse model with interferon a-2b and a protease inhibitor (BILN-2061) and by negative outcomes with a polymerase inhibitor HCV-371 in both the mouse model (2) and a phase 1b clinical trial (4).
The predictive value of the mouse model has now also been confirmed by the positive outcomes with HCV-796 in the model and in vitro studies and the recently announced preliminary data from a clinical phase 1b trial of HCV-796 and pegylated interferon combination therapy in which a mean viral load reduction across all combination groups of between 3.3 to 3.5 log was obtained at day 14 compared to a 1.7 log decrease obtained with interferon alone (6).
REFERENCES
6. Viropharma (www.viropharma.com) press elease dated Aug 28, 2006.
2. Kneteman N, et al, Anti-HCV therapies in chimeric scid-Alb/uPA mice parallel outcomes in human clinical application. Hepatology 43: 1346-1353, 2006.
4. Viropharma (www.viropharma.com) press release dated July 15, 2003.
1. Mercer D et al, Hepatitis C virus replication in mice with chimeric human livers. Nature Medicine 7: 727-933, 2001.
3. Lamarre D et al. An NS3 protease inhibitor with antiviral effects in humans infected with hepatitis C virus. Nature 426: 186-189, 2003
5. Howe AYM, et al. Novel nonnucleoside inhibitor of hepatitis C virus RNA-dependent RNA polymerase. Antimicrobial Agents & Chemotherapy 48: 4813-4821, 2004.
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