Federico Borgia

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.

A Novel Promising Therapeutic Option Against Hepatitis C Virus: An Oral Nucleotide NS5B Polymerase Inhibitor Sofosbuvir

Hepatitis C virus (HCV) infection is one of the main causes of liver disease worldwide. Its treatment is currently based on the combination of peg-interferon, ribavirin, and, for patients with genotype 1, a protease inhibitor (telaprevir or boceprevir). However, interferon-based combinations are not effective in all patients. Moreover, they are contraindicated in patients who cannot receive interferon (e.g. those with decompensated cirrhosis), and are frequently associated with adverse events. Consequently, there is a need to develop new drugs to treat HCV infection. This review focuses on preclinical and clinical data regarding sofosbuvir (GS-7977), a uridine nucleotide analogue inhibitor of HCV NS5 B polymerase that is effective against HCV genotypes 1,2, 3,4 and 6. Thanks to its excellent pharmacokinetic profile, sofosbuvir can be administered in an oral single daily dose. In vitro it exerts a potent antiviral effect against HCV. Clinical data show that combined with peg-interferon and ribavirin for 12 weeks it yields SVR of about 90% in subjects with HCV genotype 1 and about 100% in patients with HCV genotype 2 or 3. Moreover, sofosbuvir and ribavirin administered for 12 weeks yield similar high SVR rate (84% for genotype 1 and 100% for genotype 2/3 patients) as well as sofosbuvir and daclatasvir (an inhibitor of NS5A) which produce SVR rate of about 100% regardless of genotype or of ribavirin employment. Safety and tolerability of sofosbuvir appear to be excellent. In conclusion, sofosbuvir especially in interferon-free combinations represents a very promising option in the treatment of chronic hepatitis C.

Homocysteine levels and sustained virological response to pegylated‐interferon α2b plus ribavirin therapy for chronic hepatitis C: a prospective study

Background: Chronic hepatitis C affects about 3% of the worlds population. Pegylated interferon (IFN) α 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.

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 drugs 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.

Daclatasvir: The First of a New Class of Drugs Targeted Against Hepatitis C Virus NS5A

Hepatitis C virus (HCV) infection affects about 160 million people worldwide. It is treated with pegylatedinterferon (peg-IFN) and ribavirin, and in the case of patients affected by genotype 1, also with a protease inhibitor (telaprevir or boceprevir). Despite a good success rate, IFN-based combinations are contraindicated in several patients (e.g. decompensated cirrhosis, patients with psychiatric disorders, severe heart diseases or autoimmune disorders) and are associated with frequent adverse events that ultimately reduce their use. Numerous oral drugs are in an advanced phase of clinical development, and in some cases, in IFN-free combinations. This review focuses on preclinical and clinical data regarding daclatasvir (BMS-790052), which is a highly selective HCV NS5A replication complex inhibitor effective against HCV genotypes 1, 2, 3 and 4. In vitro data show that daclatasvir exerts a very potent antiviral effect against several HCV genotypes. Its pharmacokinetics is optimal and allows once-a-day oral administration. Its adverse event profile is good. Clinical data regarding its efficacy in combination with peg-IFN, ribavirin or other direct antiviral agents are impressive (rates of sustained virological response range between 60% and 100% in treatment-naïve patients). The only drawback of this drug appears to be a relatively low genetic barrier to resistance. In conclusion, daclatasvir, especially in combinations with other antiviral agents, is a very promising drug for the treatment of chronic hepatitis C.

Telaprevir: a promising protease inhibitor for the treatment of hepatitis C virus infection.

Chronic hepatitis C affects 130,000,000 people worldwide. Hepatitis C virus (HCV) is a single-strand RNA virus responsible for most cases of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma (HCC) in the Western world. The gold standard for the treatment of chronic hepatitis C (combination of pegylated-interferon alpha and ribavirin) results in a sustained virological response (namely, clearance of serum HCV RNA 6 months after therapy withdrawal) in only about half treated patients. Therefore, there is a race to develop new drugs for the treatment of HCV infection. One of the most promising approaches is to use protease inhibitors, i.e. drugs inhibiting NS3/NS4A HCV protease, which plays a crucial role in the viral life cycle. Telaprevir (VX-950) is the protease inhibitor in the most advanced phase of clinical testing. Telaprevir is orally available and when used in monotherapy it induced a median decline of 4 logs of HCV RNA after two weeks of therapy. However, mutants with a lower sensitivity to telaprevir have been demonstrated in a high proportion of patients within 14 days of monotherapy. The drug has been used in clinical trials in combination with pegylated-interferon and ribavirin. This triple combination resulted in a higher rate of SVR but also in a higher rate of side effects (rash, gastrointestinal disorders, and anemia) than standard treatment. This review focuses on the mechanism of action, pharmacokinetics, clinical efficacy, and tolerability of telaprevir, and on possible use of this drug in combination with other drugs for the treatment of HCV infection.

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.

ABT-450: A Novel Protease Inhibitor for the Treatment of Hepatitis C Virus Infection

About 2.3% of the worlds 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.

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.