Emanuela Zappulo

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.

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.

Etiopathogenesis of autism spectrum disorders: Fitting the pieces of the puzzle together

Autism spectrum disorders (ASD) are disorders of the central nervous system characterized by impairments in communication and social reciprocity. Despite thousands of studies on this topic, the etiopathogenesis of these disorders remains unclear, apart from a general belief that they derive from an interaction between several genes and the environment. Given the mystery surrounding the etiopathogenesis of ASD it is impossible to plan effective preventive and treatment measures. This is of particular concern due to the progressive increase in the prevalence of ASD, which has reached a figure as high as 1:88 children in the USA. Here we present data corroborating a novel unifying hypothesis of the etiopathogenesis of ASD. We suggest that ASD are disorders of the immune system that occur in a very early phase of embryonic development. In a background of genetic predisposition and environmental predisposition (probably vitamin D deficiency), an infection (notably a viral infection) could trigger a deranged immune response which, in turn, results in damage to specific areas of the central nervous system. If proven, this hypothesis would have dramatic consequences for strategies aimed at preventing and treating ASD. To confirm or refute this hypothesis, we need a novel research approach, which unlike former approaches in this field, examine the major factors implicated in ASD (genetic, infections, vitamin D deficiency, immune system deregulation) not separately, but collectively and simultaneously.

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.

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 discovery of sofosbuvir: a revolution for therapy of chronic hepatitis C

Introduction: Hepatitis C virus (HCV) infection is a worldwide health problem, whose management has been revolutionized after the availability of sofosbuvir, a direct-acting antiviral (DAAs). Sofosbuvir is a HCV NS5B polymerase inhibitor. Antiviral regimens including sofosbuvir are associated with success rates >90%, even in the case of “difficult-to-treat” patients such as subjects with liver cirrhosis as well as prior null response to IFN and ribavirin. Areas covered: This drug discovery case history focuses on the pre-clinical and clinical development of sofosbuvir. The authors analyze all of the main steps leading to the global approval of sofosbuvir. The paper also highlights the encouraging data from the subsequent trials wherein sofosbuvir was tested in combination with other DAAs (IFN- and often ribavirin-free regimens) and from first real life studies. Expert opinion: Sofosbuvir is a very powerful weapon in the new armamentarium against HCV. Thanks to its valuable features including its pangenotypic activity, once-daily oral administration, its excellent tolerability, and safety profile, it represents the backbone of several effective regimens, in combination with IFN or with other DAAs (IFN-free therapies). Regimens including sofosbuvir have quickly become the touchstone for all the novel anti-HCV treatments.

Prevention of mother-to-child transmission of hepatitis B virus and hepatitis C virus

About 240 million people worldwide are chronically infected with hepatitis B virus (HBV). Vertical transmission is the most important mechanism of infection persistence in endemic areas. About 150 million people worldwide are chronically infected with hepatitis C virus (HCV). Mother-to-child transmission of HCV, which occurs in 3–10% of cases, is the leading route of infection in childhood. This review focuses on strategies to reduce the vertical transmission of HBV and HCV. The at-birth prophylaxis of newborns of HBV-infected mothers with specific immunoglobulin and vaccine plus administration of antivirals (tenofovir or telbivudine) in the third trimester of pregnancy (in case of high maternal viral load) greatly reduces the risk of transmission. In contrast, currently there is no drug able to reduce the vertical transmission of HCV infection. We discuss the possibility of reducing mother-to-child HCV transmission using newly available antivirals or antivirals in the pipeline for the treatment of hepatitis C.

Asunaprevir, a protease inhibitor for the treatment of hepatitis C infection.

According to the World Health Organization, approximately 150 million people worldwide are chronic carriers of hepatitis C virus (HCV). HCV infection can evolve into cirrhosis of the liver and its complications, which are ultimately responsible for more than 350,000 deaths every year. Antiviral therapy, when successful, is able to decrease the rate of progression and increase survival. Two types of therapies are currently available, ie, interferon-based therapies and interferon-free ones. The latter have several advantages in terms of safety and tolerability, and could be used even in the most advanced stages of the disease. However, their use is restricted to some viral genotypes (genotype 2 and 3) and they are expensive. Several molecules are in an advanced phase of development. This review deals with the pharmacokinetics, pharmacodynamics, tolerability, and safety of asunaprevir, an inhibitor of HCV nonstructural 3 protease. Asunaprevir exerts optimal in vitro activity particularly against HCV genotypes 1 and 4, and its pharmacokinetic profile enables twice daily administration. The drawback of asunaprevir, and of all protease inhibitors, is its low barrier to resistance. Consequently, it is used in association with other drugs to prevent resistance. Specifically, when combined with daclatasvir, an NS5A inhibitor, asunaprevir results in a very high rate of viral eradication in both treatment-naïve and treatment-experienced patients, with a sustained virological response rate of 80%–90%. Tolerability is fair; in fact, asunaprevir is associated with a transient increase in aminotransferase levels, which is mild in most cases. In conclusion, asunaprevir is a good candidate component of interferon-free combinations and may revolutionize the treatment of chronic HCV infection in the near future.