New drugs for hepatitis C virus (HCV)

Replication efficiency of chimeric replicon containing NS5A-5B genes derived from HCV-infected patient sera

A transient subgenomic replicon-based shuttle vector system has been developed to investigate how genetic heterogeneity affects HCV replication efficiency. Individual NS5A or NS5B genes or cassettes containing both NS5A and NS5B genes were amplified from "quasispecies" pools derived from HCV genotype 1a or 1b patient sera using RT-PCR and cloned into their respective shuttle vectors. All shuttle vectors containing NS5A or NS5A-5B genes were constructed with the S2204I "adaptive" mutation because replicons lacking the S2204I mutation replicated poorly. Gene sequences of the quasispecies pools within either genotype 1a or 1b patient samples ranged from 94 to 95% in identity. The replication capacity of 1b shuttle vectors containing patient-derived NS5A or NS5B genes averaged 67 and 75%, respectively, relative to the laboratory-optimized 1b replicon. In contrast, the replication efficiencies of both 1a and 1b shuttle vectors containing patient-derived NS5A-5B gene cassettes averaged around 2% relative to the respective laboratory-optimized replicon. All patient-derived replicons were tested in a transient assay for their sensitivity to either interferon-alpha (IFN-alpha) or to the polymerase inhibitor A-782759. Despite the differences in replication efficiency, IC(50) values measured for most of the patient-derived replicons were equivalent to the respective values measured in the control laboratory strain replicons. These results demonstrate that patient sequence heterogeneity affects replication efficiency whenever patient-derived NS5A-5B genes are inserted into the laboratory-optimized replicon. The findings also demonstrate the utility of the shuttle vector system to test patient-derived gene sequences for sensitivity to IFN-alpha and to small molecule inhibitors.

Comparison of quality of life, work productivity and medical resource utilization of peginterferon alpha 2a vs the combination of interferon alpha 2b plus ribavirin as initial treatment in patients with chronic hepatitis C

The on-treatment impact of interferon-based therapies on quality of life (QOL), work productivity, and medical resource utilization has not been systematically studied. We evaluated the effects of treatment with peginterferon alpha (pegIFNalpha) 2a monotherapy and the combination of interferon alpha (IFNalpha) 2b plus ribavirin (RBV) on health-related QOL, work productivity and resource utilization. A total of 412 patients with hepatitis C infection were randomized to open-label treatment with either pegIFNalpha 2a (n = 206) or IFNalpha 2b/RBV (n = 206). PegIFNalpha 2a was administered subcutaneously at a dose of 180 microg once weekly for 48 weeks; and IFNalpha 2b/RBV at doses of 3 MU thrice weekly subcutaneously and 1000-1200 mg/day orally. Outcome measures included the SF-36 Health Survey Questionnaire and additional generic and specific scales. During treatment, for all SF-36 summary and Hepatitis Quality of Life Questionnaire (HQLQ)-specific scales, the pegIFNalpha 2a group experienced less impairment than did the IFNalpha 2b/RBV patients. The between-treatment differences were significant for many of the scores particularly in the first 24 weeks of treatment. Across all measures of work functioning and productivity at each visit, patients randomized to pegIFNalpha 2a treatment showed less impairment relative to the group treated with IFNalpha 2b/RBV. Hence treatment with pegIFNalpha 2a relative to IFNalpha 2b/RBV minimizes the adverse impact of therapy on health-related QOL. Patients randomized to pegIFNalpha 2a had improved work productivity, less activity impairment, decreased need for prescription drugs to treat adverse effects, and better adherence to therapy.

A novel high throughput screening assay for HCV NS3 serine protease inhibitors

Hepatitis C virus (HCV) infection is a major worldwide health problem, causing chronic hepatitis, liver cirrhosis and primary liver cancer (Hepatocellular carcinoma). HCV encodes a precursor polyprotein that is enzymatically cleaved to release the individual viral proteins. The viral non-structural proteins are cleaved by the HCV NS3 serine protease. NS3 is regarded currently as a potential target for anti-viral drugs thus specific inhibitors of its enzymatic activity should be of importance. A prime requisite for detailed biochemical studies of the protease and its potential inhibitors is the availability of a rapid reliable in vitro assay of enzyme activity. A novel assay for measurement of HCV NS3 serine protease activity was developed for screening of HCV NS3 serine protease potential inhibitors. Recombinant NS3 serine protease was isolated and purified, and a fluorometric assay for NS3 proteolytic activity was developed. As an NS3 substrate we engineered a recombinant fusion protein where a green fluorescent protein is linked to a cellulose-binding domain via the NS5A/B site that is cleavable by NS3. Cleavage of this substrate by NS3 results in emission of fluorescent light that is easily detected and quantitated by fluorometry. Using our system we identified NS3 serine protease inhibitors from extracts obtained from natural Indian Siddha medicinal plants. Our unique fluorometric assay is very sensitive and has a high throughput capacity making it suitable for screening of potential NS3 serine protease inhibitors.

Relationship of health-related quality of life to treatment adherence and sustained response in chronic hepatitis C patients

Interferon therapy may exacerbate health-related quality of life (HRQL) deficits associated with hepatitis C virus (HCV) early in the course of therapy. Treatment with polyethylene glycol-modified interferon (peginterferon) alfa-2a (40 kd) provides improved sustained response over interferon alfa-2a, but its effect on HRQL is unknown. The objective of this study was to (1) evaluate the effect of sustained virologic response on HRQL in patients with HCV and (2) determine whether impairment of HRQL during treatment contributes to early treatment discontinuation. Data consisted of a pooled secondary analysis of patients (n = 1,441) across 3 international, multicenter, open-label, randomized studies that compared peginterferon alfa-2a (40 kd) with interferon alfa-2a. ANCOVA was used to examine the effect of sustained virologic response on HRQL. Repeated-measures mixed-models ANCOVA was used to compare Fatigue Severity Scale (FSS) and SF-36 scores during treatment by treatment group. Logistic regression analysis was used to examine the association between changes at baseline in on-treatment HRQL and early treatment discontinuation. Sustained virologic response was associated with marked improvements from baseline to end of follow-up in all subjects, including patients with cirrhosis. During treatment, patients receiving peginterferon alfa-2a (40 kd) had statistically significantly better scores on both the SF-36 and FSS. Baseline to 24-week changes in fatigue and SF-36 mental and physical summary scores significantly predicted treatment discontinuation. In conclusion, sustained virologic response is associated with improvements in quality of life in patients with or without advanced liver disease. This parameter may be an important consideration in maximizing treatment adherence.