Antiviral Therapy

Marcellin, Patrick; Rizzetto, Mario

doi: 10.1177/135965350801301s06pmid: N/A

Foster, Graham; Mathurin, Philippe

doi: 10.1177/135965350801301s04pmid: N/A

Chronic hepatitis C is a major contributor to cirrhosis and hepatocellular cancer worldwide, justifying the considerable research effort aimed at understanding the disease and refining its treatment. As a result, significant therapeutic advances have been made in the last decade, particularly with regard to the development of pegylated interferons and ribavirin. This review will discuss the physical properties, pharmacokinetics, viral kinetics and side-effect profiles of the different treatment options and how they have improved, culminating in the use of pegylated interferon and ribavirin combination therapy as the current standard of care.

Lee, Samuel S; Ferenci, Peter

doi: 10.1177/135965350801301s03pmid: N/A

Currently, many decisions for the treatment of hepatitis C virus (HCV) are based on genotype, which is the most significant baseline predictor of response to therapy; however, it has become increasingly apparent that fixed treatment durations might not be appropriate for all patients. The use of on-treatment predictors such as rapid virological response (RVR) at week 4 and early virological response (EVR) at week 12 can be used to predict the likelihood of achieving a sustained virological response (SVR), helping to tailor treatment to the individual. Until now, EVR has been defined as achieving either undetectable HCV RNA (<50 IU/ml) or a >2 log drop in HCV RNA, but still detectable, at week 12. However, rates of SVR in patients achieving an EVR are heterogeneous. It has recently been suggested that by subdividing EVR into RVR (<50 IU/ml at week 4), complete EVR (HCV RNA <50 IU/ml at week 12) or partial EVR (HCV RNA >2 log drop in HCV RNA but still detectable [>50 IU/ml] at week 12), it might be possible to further improve the prediction of patients likely to achieve an SVR and may allow for tailoring of treatment duration. Genotype 1 and 4 patients achieving an RVR have high rates of SVR and may be candidates for shorter treatment duration. Patients with a complete EVR achieve high SVR rates with the current treatment duration of 48 weeks, whereas patients achieving a partial EVR have lower rates of SVR and could benefit from treatment intensification to 72 weeks. Here, we discuss the importance of baseline predictors of response and the emerging concept of response-guided therapy in genotype 1 and 4 patients.

Berg, Thomas; Carosi, Giampiero

doi: 10.1177/135965350801301s01pmid: N/A

On-treatment predictors of response could be useful in optimizing treatment for patients with hepatitis C virus (HCV) genotype 2 or 3. Early virological response (EVR) has limited value as a predictor of response in genotype 2 or 3 patients, as it is achieved by 97% of this population. However, rapid virological response (RVR) measured at week 4 is a strong predictor of sustained virological response (SVR) in this group, and patients achieving an RVR may be suitable candidates for shorter treatment durations. Several small studies investigating the efficacy of shortened treatment durations in this population have been published; however, differences in study design have made their collective interpretation difficult. We discuss these studies, followed by a comparison of the data from ACCELERATE, the largest, randomized trial carried out to investigate abbreviated therapy in genotype 2 and 3 patients. The data confirm that RVR, and its use alongside significant baseline predictors, can assist in optimizing therapy. Patients achieving an RVR have high SVR rates and might be candidates for shorter treatment duration, particularly those displaying a low viral load at baseline; however, the need to consider the increased rate of relapse versus the benefits of abbreviated therapy must also be considered. Conversely, in patients who do not achieve an RVR there is evidence to suggest they may benefit from intensified therapy (longer therapy and/or increased doses). As in genotype 1 and 4 patients, response-guided therapy aims to optimize treatment outcomes for individuals, without compromising SVR rates.

Dusheiko, Geoffrey; Nelson, David; Reddy, K Rajender

doi: 10.1177/135965350801301s02pmid: N/A

Ribavirin is a guanosine analogue that has little antiviral activity when used alone, but considerably enhances the efficacy of conventional and pegylated interferon in the treatment of hepatitis C virus (HCV). The precise mode of action of ribavirin is not fully understood; however, it is crucial for the achievement of high sustained virological response (SVR) rates by enhancing virological response and reducing relapse rates. Data from several studies have confirmed that higher initial doses of ribavirin lead to higher SVR rates. Furthermore, intensified ribavirin dosing might also improve SVR rates in ‘difficult-to-cure’ patients. It is also important to minimize ribavirin dose reductions to promote high SVR rates and to maintain ribavirin levels throughout treatment to prevent viral breakthrough and relapse. The pharmacokinetic profile of ribavirin reveals a long elimination half-life due to accumulation in the blood, such that its side-effect profile includes haemolytic anaemia. Therefore, finding the optimal ribavirin dose requires a balance between efficacy and its associated side effects to ensure improved patient outcomes. Here, we discuss how optimizing the ribavirin component of combined therapy for HCV is an essential part of treatment optimization.

Jensen, Donald M; Ascione, Antonio

doi: 10.1177/135965350801301s05pmid: N/A

The development of new antiviral therapies in the treatment of hepatitis C virus (HCV) is reviewed, including a discussion of the potential advances that this treatment will bring. Data from new molecules in Phase I and II clinical trials, specifically polymerase and protease inhibitors, will be discussed. The potential for resistance has been reported when these have been used as monotherapy. However, their use in combination with pegylated interferon, particularly in the presence of ribavirin, has resulted in significant improvements in antiviral activity. Preliminary studies have confirmed that the new molecules are well tolerated and further clinical studies are underway to evaluate their efficacy. Nevertheless, because of its critical role at all stages of therapy, pegylated interferon is likely to remain the cornerstone of HCV therapy.