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

Personalized care approaches to hepatitis C therapy: recent advances and future directions

INTRODUCTION

The introduction of direct-acting antivirals (DAAs) has significantly transformed the therapeutic landscape for chronic C hepatitis virus (HCV) infection. However, there is still room for further improvement in optimizing therapy efficacy and minimizing adverse effects.

AREAS COVERED

This review is devoted to the rationale for adopting a personalized approach to HCV therapy. Specifically, we explore the role of host-related factors, such as sex or the presence of comorbidities. We thoroughly examine the implications of commonly encountered comorbidities, including HIV infection, chronic renal disease, liver cirrhosis, and other chronic viral hepatitis infections. Additionally, we discuss the prevalent drug-to-drug interactions between DAAs and other medications, while providing guidance on their management. Finally, we investigate viral-related issues that can influence treatment outcomes, such as viral genotype, quasi-species, and the presence of resistance-associated mutations.

EXPERT OPINION

Despite pivotal trials demonstrating efficacy rates exceeding 90% for currently available DAA regimens, there are still opportunities to optimize therapy outcomes and tailor treatment to each patient. This can be achieved through a meticulous evaluation of the patient's specific clinical conditions and comorbidities, a vigilant approach to manage potential drug interactions, and diligent patient follow-up.

Unified Approach to Benzo[d]thiazol-2-yl-Sulfonamides

In this paper, we report a unified approach to N-substituted and N,N-disubstituted benzothiazole (BT) sulfonamides. Our approach to BT-sulfonamides starts from simple commercially available building blocks (benzo[d]thiazole-2-thiol and primary and secondary amines) that are connected via (a) a S oxidation/S-N coupling approach, (b) a S-N coupling/S-oxidation sequence, or via (c) a S-oxidation/S-F bond formation/SuFEx approach. The labile N-H bond in N-monoalkylated BT-sulfonamides (pK_a (BTSO₂N(H)Bn) = 3.34 ± 0.05) further allowed us to develop a simple weak base-promoted N-alkylation method and a stereoselective microwave-promoted Fukuyama-Mitsunobu reaction. N-Alkyl-N-aryl BT-sulfonamides were accessed with the help of the Chan-Lam coupling reaction. Developed methods were further used in stereo and chemoselective transformations of podophyllotoxin and several amino alcohols.

Direct acting antivirals treatment for hepatitis C virus infection does not increase the incidence of de novo hepatocellular carcinoma occurrence: Results from an Italian real-life cohort (LINA cohort)

The effectiveness of direct-acting antivirals (DAAs) against hepatitis C virus (HCV) infection is ascertained. However, some authors raised the issue of an increased incidence of de novo hepatocellular carcinoma (HCC) in patients treated with DAAs. Aim of the study was to evaluate the rate of HCC occurrence in a real-life cohort of patients who received anti-HCV treatment with DAAs.A prospective multicentre study was conducted. All adult patients with HCV infection who received treatment between March 2015 and December 2017 in 4 hospital of Campania region (South Italy) with at least 6 months of follow-up were enrolled.A total of 323 patients were included in the study. Most patients had HCV genotype 1b (61.8%). The overall SVR12 rate was 95.5%. Median time of observation was 10 months. The incidence rate of HCC was 0.2 per 100 person-months (crude incidence rate 3.4%, 95 confidence interval: 1.5%-5.3%). The median time for HCC occurrence was 11 months. HCC occurrence rate was significantly higher among patients who did not achieve SVR12 compared with patients who did (28.6% vs 2.8%, P < 0.05). No patient with F0-F3 fibrosis developed HCC. Among patients with cirrhosis, at the multivariate time-to-event analysis, no covariates were independently associated with the risk of HCC occurrence.Treatment with DAAs did not increase the risk of HCC occurrence. Patients who achieved SVR12 had a lower rate of HCC occurrence. Further studies are needed to estimate the incidence and the risk for HCC in the long-term follow-up among patients undergoing treatment with DAAs.

Grazoprevir/elbasvir for the treatment of adults with chronic hepatitis C: a short review on the clinical evidence and place in therapy

Chronic hepatitis C virus (HCV) infection impacts approximately 71 million people and approximately 400,000 deaths are attributed to HCV-related liver disease annually worldwide. Mainstay of treatment for over 25 years has been pegylated interferon until the advent of protease inhibitors, which has led to all-oral HCV treatment regimens that have changed the outlook of hepatitis C treatment. Grazoprevir/elbasvir provides high rates of efficacy and tolerability and is an all-oral once daily treatment option for HCV infection. Efficacy of grazoprevir/elbasvir has been proven in patients with cirrhosis, patients who have previously failed treatment with peginterferon and ribavirin (RBV), patients with end-stage renal disease and patients with HIV co-infection. Data have shown a high barrier to resistance despite the presence of resistance-associated substitutions. Grazoprevir/elbasvir represents a very promising regimen for treatment of HCV infection. This review provides a summary of pharmacology, efficacy, and safety of grazoprevir/elbasvir for the treatment of HCV infection.

Pharmacokinetics, Efficacy, and Safety of Hepatitis C Virus Drugs in Patients with Liver and/or Renal Impairment

Hepatitis C virus (HCV)-infected patients often suffer from liver cirrhosis, which can be complicated by renal impairment. Therefore, in this review we describe the treatment possibilities in HCV patients with hepatic and renal impairment. Cirrhosis alters the structure of the liver, which affects drug-metabolizing enzymes and drug transporters. These modifications influence the plasma concentration of substrates of drugs metabolized/transported by these enzymes. The direct-acting antivirals (DAAs) are substrates of, for example, cytochrome P450 enzymes in the liver. Most DAAs are not studied in HCV-infected individuals with decompensated cirrhosis, and therefore awareness is needed when these patients are treated. Most DAAs are contraindicated in cirrhotic patients; however, patients with a Child-Pugh score of B or C can be treated safely with a normal dose sofosbuvir plus ledipasvir or daclatasvir, in combination with ribavirin. Patients with renal impairment (glomerular filtration rate [GFR] <90 mL/min) or who are dependent on dialysis often tolerate ribavirin treatment poorly, even after dose adjustments. However, most DAAs can be used at the normal dose because DAAs are not renally excreted. To date, grazoprevir plus elbasvir is the preferred DAA regimen in patients with renal impairment as data are pending for sofosbuvir patients with GFR <30 mL/min (as for ledipasvir and velpatasvir). However, sofosbuvir has been used in a small number of patients with severe renal impairment and, based on these trials, we recommend sofosbuvir 400 mg every day when no other DAA regimen is available. Ledipasvir and velpatasvir are not recommended in patients with severe renal impairment.

Hepatitis C virus in vitro replication is efficiently inhibited by acridone Fac4

Hepatitis C virus (HCV) affects about 170 million people worldwide. The current treatment has a high cost and variable response rates according to the virus genotype. Acridones, a group of compounds extracted from natural sources, showed potential antiviral actions against HCV. Thus, this study aimed to evaluate the effect of a panel of 14 synthetic acridones on the HCV life cycle. The compounds were screened using an Huh7.5 cell line stably harbouring the HCV genotype 2a subgenomic replicon SGR-Feo-JFH-1. Cells were incubated in the presence or absence of compounds for 72 h and cell viability and replication levels were assessed by MTT and luciferase assays, respectively. At a concentration of 5 µM the acridone Fac4 exhibited a >90 % inhibition of HCV replication with no effect on cell viability. The effects of Fac4 on virus replication, entry and release steps were evaluated in Huh7.5 cells infected with the JFH-1 isolate of HCV (HCVcc). Fac4 inhibited JFH-1 replication to approximately 70 %, while no effect was observed on virus entry. The antiviral activity of Fac4 was also observed on viral release, with almost 80 % of inhibition. No inhibitory effect was observed against genotype 3 replication. Fac4 was able to intercalate into dsRNA, however did not inhibit NS5B polymerase activity or translation driven by the HCV IRES. Although its mode of action is partly understood, Fac4 presents significant inhibition of HCV replication and can therefore be considered as a candidate for the development of a future anti-HCV treatment.

Limiting the access to direct-acting antivirals against HCV: an ethical dilemma

Hepatitis C virus (HCV) infection affects about 200 million people worldwide and represents a leading cause of liver-related mortality. Eradication of HCV infection, achieved mainly through direct-acting antivirals (DAA), results in a decrease of mortality and an improvement of quality of life. These drugs have a maximal efficacy and an optimal tolerability. However, their high cost precludes a universal access even in wealthy countries. Areas covered: This article deals with the policies adopted for the use of the new anti-HCV drugs, especially in Europe and most of all in Italy, supposedly the developed country with the highest HCV prevalence. The literature search was performed using Pubmed and Web of Science. Moreover, national regulatory institutional websites were consulted. Expert commentary: The current policy of limitation to the access of the DAA presents a series of ethical issues that makes it non-applicable. A 'treat-all' strategy should resolve all ethical dilemmas, by virtue of the wide benefits of anti-HCV treatment not only for the advanced stage of infection, but also for the initial stages. A reduction in price of the drugs is the actual condition to achieve such a change.

Pharmacodynamics and pharmacokinetics of elbasvir and grazoprevir in the treatment of hepatitis C

INTRODUCTION

Approximately 130 - 150 million people have chronic hepatitis C virus (HCV) infection and upwards of 500,000 deaths annually are attributed to HCV related liver disease worldwide. Pegylated interferon and ribavirin have been the mainstay of treatment for greater than 25 years until recent advent of protease inhibitors which has led to all oral HCV treatment regimens that have changed the outlook of hepatitis C treatment.

AREAS COVERED

This review provides summary of pharmacokinetics, pharmacodynamics, efficacy and safety of grazoprevir/elbasvir therapy for treatment of HCV infection.

EXPERT OPINION

Grazoprevir/elbasvir provides an all-oral once daily treatment option for HCV infection with high rates of efficacy and tolerability in a pangenotypic fashion. It highly efficacious in treating patients with cirrhosis, patients who have previously failed treatment with pegylated interferon and ribavirin, and patients with HIV co-infection. Grazoprevir/elbasvir has demonstrated higher barrier to resistance even in the presence of variants associated with resistance such as Q41R, F43S, R155K, V36M, T54S, and D168. It is one of only few HCV treatment regimens evaluated for use in patients with advanced chronic kidney disease and dialysis. It is a very promising regimen for treatment of HCV infection.

Elbasvir/Grazoprevir

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are available online to subscribers. Monographs can be customized to meet the needs of a facility. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, contact Wolters Kluwer customer service at 866-397-3433. The September 2016 monograph topics are barictinib, buprenorphine implants, sarilumab, sofosbuvir/velpatasvir, and cholera vaccine, live, oral. The Safey MUE is on sofosbuvir/velpatasvir.

The therapeutic potential of new investigational hepatitis C virus translation inhibitors

INTRODUCTION

Hepatitis C virus (HCV) infection is a leading cause of liver cirrhosis, hepatocellular carcinoma and liver-related death worldwide. Currently, the anti-HCV armamentarium encompasses several direct-acting antivirals (DAA) that achieve very high response rates and have an excellent tolerability profile. However, they do not represent a final solution for HCV global eradication for at least these two reasons: i) some patients harbour resistant strains to DAAs and cannot benefit from currently available treatments; ii) the cost of these drugs remains very high.

AREAS COVERED

This review summarizes pre-clinical and clinical data regarding HCV translation inhibitors, a new class of drugs currently in the pipeline with novel mechanisms of action.

EXPERT OPINION

The availability of DAAs resolved most issues related to HCV treatment compared with the previous interferon-based therapies. However, there are some patients that cannot achieve a viral clearance with currently available treatments. Therefore, there is still room for new drugs in this setting, providing that they demonstrate an advantage in terms of efficacy, safety, cost or or simplicity of use. Based on preliminary results, at least for some promising molecules (e.g. miravirsen and RG-101), studies on safety and efficacy on this intriguing class of drugs are needed.

Resistance to direct-acting antiviral agents: clinical utility and significance

PURPOSE OF REVIEW

This article examines the dynamics and factors underlying hepatitis C virus (HCV) resistance, along with their impact on daily clinical management of HCV-infected patients.

RECENT FINDINGS

Across available treatment-regimens, GT-3 is the most difficult-to-cure genotype, but also genotype-1a may show lower success-rates compared with genotype-1b. Natural resistance to NS3, NS5A and NS5B inhibitors may contribute to treatment failures. The Q80K NS3-protease mutation affects sensibility to simeprevir + peg-interferon/ribavirin combinations. It reaches up to 48% prevalence in genotype-1a in some studies (but it is lower in other). Resistant variants (particularly in NS5A) developed at failure can persist, in a substantial proportion of patients, even 3 years after treatment-discontinuation, potentially affecting readministration of the same direct-acting antiviral agent (DAA)-class. This will become an issue for those patients failing all-oral regimens with multiple-resistant viruses.

SUMMARY

Recent data support the importance of an accurate genotype and genotype-1 subtype (1a/1b) assignment prior therapy. Resistance testing at baseline has no clear indication so far in clinical practice for all-DAA regimens selection, while it remains a valuable option at the retreatment of patients who failed DAA-containing regimens, provided that data are generated to inform treatment decisions based on the results of resistance testing. In this context, long-term RAVs persistence after failure should be taken into account.

Potent Antiviral Activities of the Direct-Acting Antivirals ABT-493 and ABT-530 with Three-Day Monotherapy for Hepatitis C Virus Genotype 1 Infection

ABT-493 is a hepatitis C virus (HCV) nonstructural (NS) protein 3/4A protease inhibitor, and ABT-530 is an HCV NS5A inhibitor. These direct-acting antivirals (DAAs) demonstrated potent antiviral activity against major HCV genotypes and high barriers to resistance in vitro. In this open-label dose-ranging trial, antiviral activity and safety were assessed during 3 days of monotherapy with ABT-493 or ABT-530 in treatment-naive adults with HCV genotype 1 infection, with or without compensated cirrhosis. The presence of baseline resistance-associated variants (RAVs) was also evaluated. The mean maximal decreases in HCV RNA levels from baseline were approximately 4 log₁₀ IU/ml for all ABT-493 doses ranging from 100 mg to 700 mg and for ABT-530 doses of ≥40 mg. There were no meaningful differences in viral load declines for patients with versus without compensated cirrhosis. Twenty-four (50%) of the baseline samples from patients treated with ABT-493 had RAVs to NS3/4A protease inhibitors. Among 40 patients treated with ABT-530, 6 (15%) carried baseline RAVs to NS5A inhibitors. Viral load declines in patients with single baseline NS5A RAVs were similar to those in patients without RAVs. One patient harbored baseline RAVs at 3 NS5A positions and appeared to have a slightly less robust viral load decline on day 3 of monotherapy. No serious or grade 3 (severe) or higher adverse events and no clinically relevant laboratory abnormalities were observed with either compound. ABT-493 and ABT-530 demonstrated potent antiviral activity and acceptable safety during 3-day monotherapy in patients with HCV genotype 1 infection, with or without compensated cirrhosis. Based on these results, phase II studies assessing the combination of these DAAs for the treatment of chronic HCV infection in patients with or without compensated cirrhosis have been initiated. (This study has been registered at ClinicalTrials.gov under registration no. NCT01995071.)

Hepatitis C virus infection: Are there still specific problems with genotype 3?

Hepatitis C virus (HCV) infection is one of the most common causes of chronic liver disease and the main indication for liver transplantation worldwide. As promising specific treatments have been introduced for genotype 1, clinicians and researchers are now focusing on patients infected by non-genotype 1 HCV, particularly genotype 3. Indeed, in the golden era of direct-acting antiviral drugs, genotype 3 infections are no longer considered as easy to treat and are associated with higher risk of developing severe liver injuries, such as cirrhosis and hepatocellular carcinoma. Moreover, HCV genotype 3 accounts for 40% of all HCV infections in Asia and is the most frequent genotype among HCV-positive injecting drug users in several countries. Here, we review recent data on HCV genotype 3 infection/treatment, including clinical aspects and the underlying genotype-specific molecular mechanisms.

Asunaprevir for hepatitis C: a safety evaluation

INTRODUCTION

The introduction of direct-acting antiviral (DAA) agents has revolutionized the treatment of hepatitis C virus (HCV) chronic infection. Non-structural 3 protease inhibitors are currently the most numerous class of DAAs on the market.

AREAS COVERED

This review mainly focuses on the tolerability and safety profile of asunaprevir (ASV)-containing DAA regimens. ASV is a second-wave protease inhibitor currently in Phase III clinical development in most countries and already available in Japan.

EXPERT OPINION

ASV shows potent antiviral effect and clinical efficacy on HCV genotypes 1 and 4. The all-oral combination daclatasvir/ASV reached high eradication rates in HCV genotype 1b and 4 infection, and a lower efficacy in genotype 1a infection. ASV presents a low potential for drug-drug interaction and a good tolerability as part of multiple, including all-oral, regimens. ASV is associated with a transient and usually mild increase in aminotransferase levels in a low percentage of cases. Due to the impaired pharmacokinetic profile observed in advanced liver disease, ASV use in patients with moderate or severe hepatic impairment is not allowed. In conclusion, ASV represents a powerful weapon against HCV infection and has to be considered an optimal option as a component of genotype tailored interferon-free combinations.

Beclabuvir for the treatment of hepatitis C

INTRODUCTION

About 185,000,000 people worldwide are chronically infected with hepatitis C virus (HCV). Currently, the most successful HCV infection antiviral therapies reduce the chance of progression towards the advanced phases of the hepatopathy (liver cirrhosis, hepatocellular carcinoma and death). Recently, however, several new direct-acting antivirals against HCV are available or are in an advanced phase of clinical development.

AREAS COVERED

This review focuses on beclabuvir , an allosteric non-nucleotide inhibitor of HCV polymerase. The article covers its pharmacokinetics, mechanism of action, in addition to its tolerability and safety profile as well as its resistance pattern.

EXPERT OPINION

The pharmacokinetic, efficacy and tolerability profile of beclabuvir, as well as its barrier to resistance, are very favorable. In particular, the combination of beclabuvir with asunaprevir and daclatasvir achieves very high rates of viral eradication (about 90%) in patients infected with HCV genotype 1, which is the most common genotype worldwide. Therefore, beclabuvir represents a powerful weapon against HCV infection and has to be considered an optimal option in tailored IFN-free combinations.

New era for management of chronic hepatitis C virus using direct antiviral agents: A review

The pegylated interferon regimen has long been the lone effective management of chronic hepatitis C with modest response. The first appearance of protease inhibitors included boceprevir and telaprevir. However, their efficacy was limited to genotype 1. Recently, direct antiviral agents opened the gate for a real effective management of HCV, certainly after FDA approval of some compounds that further paved the way for the appearance of enormous potent direct antiviral agents that may achieve successful eradication of HCV.

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.

Exploring resistance mechanisms of HCV NS3/4A protease mutations to MK5172: insight from molecular dynamics simulations and free energy calculations

Mutations at a number of key positions (Ala156, Asp168 and Arg155) of the HCV NS3/4A protease can induce medium to high resistance to MK5172.

Interferon-free antiviral combination therapies without nucleosidic polymerase inhibitors

The establishment of robust HCV cell culture systems and characterization of the viral life cycle provided the molecular basis for highly innovative, successful years in HCV drug development. With the identification of direct-acting antiviral agents (DAAs), such as NS3/4A protease inhibitors, NS5A replication complex inhibitors, nucleotide and non-nucleoside polymerase inhibitors, as well as host cell targeting agents, novel therapeutic strategies were established and competitively entered clinical testing. The first-in-class NS3/4A protease inhibitors telaprevir and boceprevir, approved in 2011, were recently outpaced by the pan-genotypic nucleotide polymerase inhibitor sofosbuvir that in combination with pegylated interferon and ribavirin, further shortens therapy durations and also offers the first interferon-free HCV treatment option. In the challenging race towards the goal of interferon-free HCV therapies, however, several oral DAA regimens without nucleotide polymerase inhibitors that combine a NS3/4A protease inhibitor, a NS5A inhibitor and/or a non-nucleoside polymerase inhibitor yielded competitive results. Second generation NS3/4A protease and NS5A inhibitors promise an improved genotypic coverage and a high resistance barrier. Results of novel DAA combination therapies without the backbone of a nucleotide polymerase inhibitor, as well as treatment strategies involving host targeting agents are reviewed herein.

Ombitasvir: a potent pan-genotypic inhibitor of NS5A for the treatment of hepatitis C virus infection

Hepatitis C virus (HCV) chronically infects about 150,000,000 people worldwide and is a relevant cause of liver cirrhosis, hepatocellular carcinoma and death. Antiviral treatment is rapidly moving from interferon (IFN)-based therapy to IFN-free approaches. This review focuses on the mechanism of action, pharmacokinetics, efficacy, tolerability, safety and resistance of ombitasvir, which is an inhibitor of the HCV nonstructural protein 5A. The pharmacokinetics of ombitasvir enables its once daily administration. In vivo, in combinations with other oral direct acting antivirals, ombitasvir achieves very high rates of sustained virological response (about 95%) in patients with HCV genotype 1 infection with a good tolerability. Resistance profiling revealed a low barrier to resistance when given as monotherapy. However, coadministration of ombitasvir and other antivirals enhances its barrier to resistance. In conclusion, ombitasvir is a good drug to be used in IFN-free combinations for the treatment of chronic 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.

Vertical transmission of hepatitis B virus: challenges and solutions

More than 240 million people worldwide are chronically infected with hepatitis B virus (HBV). Mother-to-child transmission remains the most important mechanism of infection in countries with a high prevalence of HBV. Universal screening of all pregnant women, at-birth prophylaxis with specific anti-HBV immune globulin, as well as HBV vaccination for newborns of infected mothers are effective in reducing the risk of vertical transmission. However, in cases of a high viral load and hepatitis B e antigen positivity, there is a residual risk of HBV transmission to the newborn despite prophylaxis. This review focuses on the above-indicated strategies and on the efficacy and safety of antiviral drugs administered during the third trimester of pregnancy.

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.

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.