Antonio Riccardo Buonomo

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.

Interferon-free therapies for chronic hepatitis C: toward a hepatitis C virus-free world?

About 2% of the world’s population is estimated to be chronically infected with hepatitis C virus (HCV). These chronic carriers are at risk of developing liver cirrhosis and its complications. Successful treatment of HCV infection is associated with improved quality of life and increased survival. Antiviral approaches were formerly based on interferon and therefore all patients with a contraindication to interferon were excluded from treatment (e.g., patients with decompensated disease, severe impairment of other organs). Very recently, interferon-free combinations have become available for genotypes 2 and 3. This review focuses on the most recently reported data on the various interferon-free combinations used (namely, sofosbuvir-based combinations, the ABT-450/ombitasvir/dasabuvir/ribavirin combination, the daclatasvir/asunaprevir combination, and the MK-5172/MK-8742 combination). All these combinations yielded amazing results in terms of efficacy (90–100%), tolerability and safety. If the problem of the high cost is overcome, interferon-free therapies will lead to what has long been a chimera, namely, an HCV-free world.

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.

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.

Dasabuvir: A Non-Nucleoside Inhibitor of NS5B for the Treatment of Hepatitis C Virus Infection

Hepatitis C virus (HCV) chronically infects about 2% of the worlds population. Approximately a quarter of these patients will develop, during their life, liver cirrhosis, which entails a high risk of complications and death. Successful antiviral therapy can reduce the risk of disease progression, but it is feasible only in a minority of patients because it includes interferon which is contraindicated in the most advanced stages of the disease and in patients with severe impairment of other organs. Consequent to the launch of the first direct antiviral agents (DAA), namely the protease inhibitors telaprevir and boceprevir, several molecules are in an advanced phase of clinical development to be used in association with interferon or with other DAA (in interferon-free combinations). This review focuses on the mechanism of action, pharmacokinetics, efficacy, safety and resistance of dasabuvir, a non-nucleoside inhibitor of NS5B viral RNA-dependent RNA polymerase. Thanks to its pharmacokinetics, dasabuvir can be administered twice daily. In combinations with other oral DAAs, dasabuvir results in very high rates of SVR (about 95%) in patients with HCV genotype 1 infection with a good tolerability and safety. In conclusion, dasabuvir is a good agent to be used in interferon-free combinations for the treatment of chronic hepatitis C.

A Simple Noninvasive Score Based on Routine Parameters can Predict Liver Cirrhosis in Patients With Chronic Hepatitis C

Background Liver biopsy has remained the gold standard for the diagnosis of chronic hepatitis C; even though, it has a low but non-negligible rate of both false negative and complications. Several authors have proposed noninvasive tools to diagnose cirrhosis. But none of them showed complete concordance with liver biopsy. Objectives To devise a score based on noninvasive routine parameters that discriminate between patients with a high risk, and those with a low risk of cirrhosis among patients with chronic hepatitis C without performing liver biopsy, and to compare this score with other ones using routine parameters devoted to this aim. Patients and Methods We reviewed the charts of patients with chronic hepatitis C who performed a liver biopsy between 2000 and 2004. Multivariate analysis was used to identify independent predictors of cirrhosis. An independent group of patients with chronic hepatitis C admitted for a liver biopsy between 2007 and 2012 constituted the validation set. Results We enrolled 249 patients who had complete laboratoristic data, and sufficient liver tissue for fibrosis staging. Age, AST, prothrombin activity, and platelets were identified as independent predictors of histological cirrhosis. We categorized these variables, and devised a novel score called CISCUN (Cirrhosis Score University of Naples), giving one point to each of the following predictors: age > 40 years; AST > 2 upper normal values; platelet count < 160.000/mmc; prothrombin activity < 100%. Cirrhosis rate was 2.9% for the 103 patients with a CISCUN = 0 or 1, 23.4% for the 124 patients with a CISCUN of 2 or 3, and 86.4% for the 22 patients with a CISCUN = 4. These results were confirmed in the independent validation group of 285 patients with similar characteristics. Conclusions Patients with chronic hepatitis C and with a CISCUN ≤ 1 had a very low rate of cirrhosis while those with a CISCUN = 4 had a high risk of cirrhosis. Patients with CISCUN = 2 or 3 had an intermediate rate of cirrhosis, and therefore needed to perform a liver biopsy to receive a reliable diagnosis.

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.

Investigational nucleoside and nucleotide polymerase inhibitors and their use in treating hepatitis C virus

Introduction: About 150 million people worldwide are estimated to be chronically infected with the hepatitis C virus (HCV). Successful antiviral treatment can stop the progression of the disease toward liver cirrhosis, hepatocellular carcinoma and death. IFN has been the drug of choice and the backbone of all combinations in the past two decades. However, an IFN-free combination (sofosbuvir and ribavirin) has been recently approved for genotypes 2 and 3 patients with many other drugs in preclinical and clinical development. Areas covered: This review focuses on investigational nucleoside or nucleotide inhibitors of viral polymerase that are potential treatments of HCV. The article reviews drugs that are currently under investigational status. Expert opinion: Currently, mericitabine has the most robust data but its efficacy appears to be less than optimal. Other drugs such as ALS-2200 (and its diastereomer VX-135) and BMS-986094 are promising but the data in humans are too scanty to draw conclusions about their future role at this current point in time. Other promising molecules are LG-7501, ACH-3422 and EP-NI266, although no clinical studies have been performed thus far, so this must be rectified. Another drug of promise GS-6620 has displayed a high degree of pharmacokinetic and pharmacodynamic variability, which makes further development unlikely.

Discontinued drugs in 2012 – 2013: hepatitis C virus infection

Introduction: Hepatitis C virus (HCV) chronically infects about 150 million people worldwide. Antiviral treatment can stop and even reverse the progression of the disease. Several antivirals have been developed. However, about 10,000 compounds are tested for each drug that eventually reaches the market. It would be useful to learn from these failures, for example, by reporting the candidate drugs that were discontinued and the reason for discontinuation. Areas covered: This article focuses on the anti-HCV drug candidates discontinued between 1 January 2012 and 1 January 2014. Expert opinion: In detail, 17 drugs were discontinued. Of these: 10 were NS5B inhibitors, 3 were NS5A inhibitors, 2 were immunostimulants, 1 was a therapeutic and prophylactic vaccine and 1 an NS3 inhibitor. Only 3 candidates were discontinued in the preclinical phase, and 14 were discontinued during clinical development (8 in Phase II and 6 in Phase I). Most discontinuations were attributed to corporate strategic decisions. The authors believe that learning from HCV drug development failures will help pharmaceutical companies and researchers to develop better strategies for the future. It is therefore important that this information is made available.