ABT-450: a novel protease inhibitor for the treatment of hepatitis C virus infection.

About 2.3% of the world's population is infected with hepatitis C virus (HCV) and patients have a high risk of developing liver cirrhosis and its complications. Current therapeutic strategies are based on a combination of pegylatedinterferon, ribavirin and (only for patients with genotype 1 infection) a protease inhibitor (boceprevir or telaprevir). Consequently, all these combinations have the limitations of interferon. In fact, they are contraindicated in decompensated disease and in subjects with severe comorbidities, and are associated with a high rate of side effects. Moreover, they are poorly effective in advanced disease. As complete viral eradication is associated with improved disease-free survival, several molecules are under clinical development for their potential to overcome the drawbacks of currently available treatments. This review focuses on the pharmacodynamics, pharmacokinetics, safety and tolerability of ABT-450, a potent inhibitor of non-structural 3 protease. ABT-450 is a substrate of cytochrome P450; hence its co-administration with ritonavir, a cytochrome P450 inhibitor, dramatically increases the plasma concentration and half-life of ABT-450 and allows once-daily administration. Given in monotherapy for 3 days at different doses, ABT-450 causes a mean maximum viral decline of about 4 logs. Interestingly, high doses of ABT-450 are associated with a reduced and delayed development of resistance-conferring mutations. Given in combination with other direct antiviral drugs, the sustained response rate reaches 90-95% in both naïve and treatment-experienced genotype 1 patients, and tolerability is good. In conclusion, ABT-450 is an excellent component of interferon-free combinations for the treatment of chronic HCV infection.

Ledipasvir : a novel synthetic antiviral for the treatment of HCV infection.

INTRODUCTION: About 150,000,000 people worldwide are chronically infected with hepatitis C virus (HCV). HCV infection can lead to liver cirrhosis, hepatocellular carcinoma and death. Treatment was based previously only on pegylated interferon combined with other antiviral drugs. Recently, the first interferon-free combination for patients with genotype 2 or 3 was approved in the USA and Europe, and several molecules are in an advanced phase of clinical development. AREAS COVERED: This review focuses on the pharmacokinetics, pharmacodynamics and tolerability of ledipasvir , an inhibitor of HCV nonstructural 5A protein. The authors also highlight the drug's safety and resistance profile. EXPERT OPINION: The pharmacokinetic profile and antiviral activity of ledipasvir are ideal. However, given the high rate of natural and drug-related ledipasvir-resistant HCV mutations, ledipasvir is administered in combination regimens with other antiviral drugs, which resulted in a cure rate up to 100%. While ledipasvir is effective in patients with genotype 1 chronic hepatitis C, its efficacy remains to be established in patients with genotype 4, 5 or 6, in subjects with HIV coinfection, in hemodialyzed and elderly patients and in subjects with decompensated cirrhosis. If the excellent results of combination therapy be confirmed in larger trials, hepatologists will have the possibility to cure most HCV-positive patients in the near future.

MK-5172 : a second-generation protease inhibitor for the treatment of hepatitis C virus infection.

INTRODUCTION: Approximately 170 million people worldwide are chronic carriers of the hepatitis C virus (HCV). Twenty-five percent of them develop liver cirrhosis and hepatocellular carcinoma during their life. Successful antiviral treatment dramatically reduces the risk of disease progression. HCV infection is treated with pegylated interferon and ribavirin; the addition of a protease inhibitor (boceprevir or telaprevir) can also be considered for patients with genotype 1. AREAS COVERED: This review summarizes the data about the pharmacokinetics, pharmacodynamics, efficacy and safety of MK-5172 , a second-generation inhibitor of HCV NS3/4A protease. EXPERT OPINION: The pharmacokinetic profile allows for once-a-day administration. Combined with pegylated interferon and ribavirin, MK-5172 results in a high rate of HCV eradication (in about 90% of cases) and a better outcome than boceprevir-based triple therapy. Also in interferon-free combinations, MK-5172-associated eradication rates are very high (89 - 100%). MK-5172 has a higher barrier to resistance than first-generation protease inhibitors and is active against most variants associated with resistance to first-generation protease inhibitors. Tolerability and safety profile are good. Although data are limited, MK-5172 appears to overcome most of the drawbacks of the first-generation protease inhibitors and is thus a very promising agent to be used in combination with other antivirals to eradicate HCV infection.

Efficacy and Safety of Sofosbuvir in the Treatment of Chronic Hepatitis C: The Dawn of a New Era.

Hepatitis C virus (HCV) infection affects about 160 million people worldwide. Currently, it is treated with pegylated interferon (PEG-IFN) plus ribavirin, associated with a protease inhibitor in case of genotype 1 infection. However, this combination is often contraindicated and associated with severe adverse events that limit its use in clinical practice. Several drugs active against HCV are in an advanced phase of clinical development. Among these, sofosbuvir appears one of the most promising candidates for use in association with both interferon and interferon-free combinations. This review focuses on the results of several sofosbuvir-based phase III trials that have very recently become available. These studies show that the co-administration of sofosbuvir, PEG-IFN and ribavirin for 12 weeks is associated with a very high rate of sustained virological responses (SVR) (about 90%) in naïve patients with genotypes 1, 4, 5 or 6. In patients infected by genotypes 2 or 3, the interferon-free combination of sofosbuvir and ribavirin administered for 12 weeks is associated with a SVR of 97% and 56% in naïve patients, and of 86% and 30% in experienced genotype 2 or 3 patients, respectively. The safety and tolerability profile is optimal and consistent with that of the other drugs administered in the combination (ribavirin and/or interferon). In conclusion, the recent phase III trials of sofosbuvir confirm the excellent results of phase II studies in terms of efficacy and safety and will probably open a new era in the fight against HCV.

The efficacy and safety of telaprevir - a new protease inhibitor against hepatitis C virus.

IMPORTANCE OF THE FIELD: Hepatitis C virus (HCV) is the main agent of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma in the western world. It affects more than 170 million people worldwide. HCV treatment, based on the combination of Peg-interferon and ribavirin, is effective in about 50% of treated patients. Therefore, there is a need to develop new drugs active against HCV. AREAS COVERED IN THIS REVIEW: Data were obtained by searching for all full articles on Medline and abstracts presented at major international congresses on viral hepatitis. WHAT THE READER WILL GAIN: A review of clinical data about the efficacy and safety of telaprevir (VX-950), the HCV protease inhibitor that is in the most advanced phase of clinical development. TAKE HOME MESSAGE: Telaprevir has an acceptable pharmacokinetic profile and seems to be a potent antiviral drug against HCV, although, owing to a low genetic barrier, resistant variants emerge within a few days when used in monotherapy, thereby decreasing its efficacy. Consequently, telaprevir has been combined with pegylated-interferon and ribavirin in clinical trials. This triple combination is more effective but has a higher rate of adverse events (notably rash) than the standard of care, despite the shorter duration of therapy.

Homocysteine levels and sustained virological response to pegylated-interferon alpha2b plus ribavirin therapy for chronic hepatitis C: a prospective study.

BACKGROUND: Chronic hepatitis C affects about 3% of the world's population. Pegylated interferon (IFN) alpha plus ribavirin is the gold standard treatment. Methylenetetrahydrofolate reductase(MTHFR) is a key enzyme in the metabolism of homocysteine. MTHFR gene polymorphisms and high levels of homocysteine are associated with a high degree of steatosis and fibrosis, conditions associated with a low sustained virological response (SVR) rate. AIMS: To evaluate whether MTHFR polymorphisms and homocysteine levels are predictors of the outcome of treatment in 102 prospectively enrolled patients with chronic hepatitis C naive to treatment. METHODS: Patients were treated with pegylated interferon alpha-2b plus ribavirin. All patients underwent blood tests, assessment of homocysteine, vitamin B(12), folate, hepatitis C virus (HCV)-RNA levels, screening for MTHFR gene polymorphisms and liver ultrasound examination. RESULTS: Homocysteine levels were deranged (>16 micromol/L) in 10.5% of MTHFR wild-type patients vs 40.3% of non-wild-type patients (P=0.015). Homocysteine levels were 14.4 micromol/L in SVR patients and 15.5 micromol/L in non-SVR patients (P=0.049). The SVR rate was 40.0% in MTHFR wild-type patients, 52.0% in heterozygote mutants and 39.3% in homozygote mutants (P=0.467). At logistic regression analysis, genotypes 2 and 3 (odds ratio: 12.328, 95% confidence interval: 3.390-44.837, P=0.0001), homocysteine <16 micromol/L (odds ratio: 3.397, 95% confidence interval: 1.033-11.177, P=0.044) and aspartate aminotransferase (AST) levels <48 U/L (odds ratio: 3.262, 95% confidence interval: 1.125-9.458, P=0.029) were independent predictors of SVR. CONCLUSIONS: In patients with chronic hepatitis C, homocysteine levels are associated with the outcome of pegylated-IFNalpha plus ribavirin treatment, while polymorphisms of MTHFR are not.