Figures
Abstract
Background
Hepatitis C genotype 6 (HCV-6) is prevalent in Southeast Asia. Data on the efficacy of direct-acting antiviral agents in chronic HCV-6 patients is limited and pegylated interferon (Peg-IFN) plus ribavirin (RBV) combination therapy remains standard therapy for those patients.
Aim
Meta-analysis was performed to assess the efficacy and safety of Peg-IFN plus RBV combination therapy for chronic HCV-6 patients.
Methods
Relevant studies were found by database search through Medline, Embase, Web of Science and The Cochrane Library. All published clinical trials assessing the efficacy of Peg-IFN plus RBV combination therapy for chronic HCV-6 patients were included. Sustained virological response rate (SVR) was pooled. We performed additional meta-analyses to compare the SVR outcomes of 24 versus 48 weeks of treatment in four head-to-head trials. Another second meta-analysis was also conducted to compare the efficacy of combination Peg-IFN plus RBV therapy in HCV-6 versus HCV-1 patients.
Results
Thirteen studies met the inclusion criteria. The pooled SVR of all single arms was 75% (95% CI: 0.68–0.81). The SVR of 24 weeks treatment was significantly lower than that at 48 weeks, with a risk difference of −14% (95% CI: −0.25 to −0.02, p = 0.02). However, when restricted to the patients with rapid virological response (RVR), there was no significant effect on SVR between these two treatment groups, with a risk difference of −1% (95% CI: −0.1 to 0.07, p = 0.67). The SVR in HCV-6 patients was significantly higher than that in HCV-1 patients, with a relative risk of 1.35 (95% CI: 1.16–1.57, p<0.001). Side effects were common, but rarely caused treatment discontinuation.
Citation: Wang X, Liu F, Wei F, Ren H, Hu H (2014) Efficacy and Safety of Pegylated Interferon Plus Ribavirin Therapy for Chronic Hepatitis C Genotype 6: A Meta-Analysis. PLoS ONE 9(6): e100128. https://doi.org/10.1371/journal.pone.0100128
Editor: Wenzhe Ho, Temple University School of Medicine, United States of America
Received: March 25, 2014; Accepted: May 21, 2014; Published: June 25, 2014
Copyright: © 2014 Wang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. Data included in this meta-analysis were from Reference 25 to 37 in the manuscript. All the data are publicly available.
Funding: This research was supported by the Natural Science Foundation of China (81171560, 30930082, 81171561, 30972584), the National Science and Technology Major Project of China (2008ZX10002-006, 2012ZX10002007001, 2011ZX09302005, 2012ZX09303001-001, 2012ZX10002003), the Key Project of Chongqing Science and Technology (cstc2012gg-yyjsB10007), the Chongqing Natural Science Commission Foundation (cstc2011jjA10025), the Medical Research Fund by Chongqing Municipal Health Bureau (2009-1-71). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
HCV infection frequently causes liver cirrhosis and liver cancer. Almost 3% of the world population have chronic HCV infection, and over 350,000 people die annually due to advanced liver disease [1]. Until now, six primary genotypes and numerous subtypes have been classified based on HCV nucleotide sequences [2]. HCV genotypes have a varied geographic distribution around the world. The most common genotypes in Western Europe and North America are 1, 2, and 3 [3],[4]. HCV genotype 4 is mostly distributed in the Middle East and North Africa, while genotype 5 is limited to South Africa. Of the primary HCV genotypes, genotype 6 is one of the most prevalent in Southern China and Southeast Asia, contributing to almost 30% of all HCV-infected patients in these areas [5]. Among the subtypes of HCV-6, subtype 6a is the most geographically limited having been discovered only in Vietnam, Macau and Hong Kong, or emigrants from those countries [6].
Recent advances in the development of direct-acting antiviral agents (DAAs), which inhibit viral proteins and block the HCV lifecycle, have revolutionized HCV therapy [7]. DAAs can achieve higher antiviral responses when combined with pegylated interferon (Peg-IFN) plus ribavirin (RBV) [8], [9]. They also have the potential to eradicate HCV without IFN [10]. In 2011, boceprevir and telaprevir received FDA approval for use in HCV-1 patients, and were the first approved DAAs for anti-HCV therapy [11]. Subsequently, a number of additional DAAs are being tested in ongoing clinical trials, and two are now commercially available. However, in many countries, DAAs are still not available or are too expensive for general use. As a result, in those places, a combination of Peg-IFN with RBV remains the standard therapy for chronic hepatitis C [12].
The HCV genotype is a crucial predictor of anti-viral therapeutic response, and is also important in determining treatment duration [13]. Patients with HCV-1 have a much lower sustained virological response (SVR) rate of only ∼40–50% with Peg-IFN plus RBV combination therapy. In contrast, HCV-2 is considered an “easy to treat” genotype compared to HCV-1 [14]. Furthermore, many recent studies have indicated that HCV-2 can achieve higher SVR than HCV-3 [15], [16]. Consequently, the package inserts state that HCV-1 patients should be treated for 48 weeks with Peg-IFN plus RBV combination therapy, whereas for HCV-2 patients, 24 weeks was recommended [12], [17]. However, the data on expected response rates and optimal treatment duration for HCV genotype 6 (HCV-6) are limited compared to what is known for genotypes 1–3.
Meta-analysis is a useful quantitative approach to combine the results from multiple studies, especially when the results of the studies are not consistent. Although the efficacy and safety of Peg-IFN and RBV combination therapy in HCV-6 patients have been evaluated by others through a systematic review [2], no comprehensive meta-analyses of clinical trial data were reported. The aim of the present study was to conduct a meta-analysis of trials to assess the efficacy and safety of Peg-IFN and RBV treatment in chronic HCV-6 patients.
Methods
Eligibility
Our review included eligible clinical trials that assessed the efficacy of combination therapy with Peg-IFN and RBV in chronic HCV-6 patients. For inclusion, published articles or abstracts had to: (a) have a protocol with an adequate course of treatment (24 or 48 weeks); (b) provide information on a primary outcome of interest clearly defined as sustained virological response (SVR), which was defined as undetectable HCV RNA at least 24 weeks after the end of treatment; (c) focus on treatment-naïve adult patients; (d) be reported in English. We excluded the studies referring to patients with other HCV genotypes, hepatitis B virus or human immune deficiency virus co-infections, other liver diseases, hemophilia, chronic renal failure, liver decompensation, liver transplantation, liver cancer, and psychosis. The studies that had less than 10 HCV-6 patients were also excluded. When there were multiple publications from the same population, only data from the most recent and complete ones were selected. Moreover, we contacted the authors if further detailed data was required.
Search strategy
Searches of Medline, Embase, Web of Science and The Cochrane Library, from inception to December 2013, were conducted by two investigators (XWW and FL). The following keywords were searched in combination of MeSH terms and text words: “hepatitis C”, “genotype”, “peg-interferon” and “ribavirin”. To locate additional studies, relevant reference lists, journals and abstracts of two international meetings in the areas of liver disease (AASLD and EASL) were also searched. Furthermore, we corresponded with authors for more information when necessary.
Study selection and data extraction
Titles and abstracts of potentially eligible publications were screened by two investigators (XWW and FL). We retrieved and independently reviewed all the trials for possible inclusion. Conflicting opinions were resolved by consensus between the two investigators. When required, the corresponding author (HDH) provided arbitration.
Using a data collection form, each selected study was abstracted independently and in duplicate by the two reviewers (XWW and FL). The following information was extracted: year of publication, study design, study population, number of participants per study arm, baseline patient characteristics, treatments received, duration of follow up, and virological responses. Where possible, data on adverse events were extracted as well. Any disagreement between the reviewers was resolved as mentioned above.
Endpoints
Endpoints were defined prior to the initiation of the study. To estimate the efficacy of Peg-IFN plus RBV treatment in the selected trials, the SVR rate (percentage of patients with undetectable HCV RNA at least 24 weeks after the end of treatment) was defined as the primary outcome. The secondary outcomes were the rates of rapid virological response (RVR, undetectable HCV RNA at week 4), treatment discontinuation and adverse events. Differences in the limits of HCV RNA detectability among the studies are shown in Table 1.
Statistical Analysis
Primary and secondary outcomes were evaluated by calculating point estimates and 95% confidence intervals (CIs) and p values. We used a Freeman-Tukey type arcsine square root transformation [18] to stabilize the variance of raw proportions (r/n), and then pooled the proportions by a DerSimonian–Laird random-effects model [19], [20]. As errors may occur when evaluating heterogeneity in pooled proportions, we calculated the I2value when required [21]. To assess sources of potential bias, sensitivity analyses were conducted for included studies where required. For some direct comparison studies, we calculated the risk difference of SVR between 24 and 48 weeks treatment for HCV-6 patients. In some trials, we included head-to-head comparison of antiviral therapeutic efficacy in HCV-1 versus HCV-6. A second meta-analysis was performed to pool the relative risk of SVR. Furthermore, we constructed funnel plots for both primary and secondary outcomes, together with Egger's regression asymmetry test and Begg's rank correlation test [22], [23], to assess potential publication bias. All analyses were conducted by Stata (version 12.0) and R (version 3.0.2) software, with a P<0.05 considered significant.
Results
We initially identified 123 citations by manual and electronic database searches. After removing 61 duplicate citations, 62 remained. We screened the titles and abstracts of remaining citations and found 21 potentially eligible trials. Eight potential trials were excluded because those studies included co-infected patients, and could not provide sufficient data on primary outcomes. After parsing, 13 studies were included in this meta-analysis [24]–[36]. Figure 1 shows a diagram of the process of study selection.
Among the 13 eligible trials, 10 were published as full-texts, while 3 were abstracts [24], [29], [36]. The characteristics of included studies are shown in Table 1. In total, the pooled number of HCV-6 patients in these studies was 849 participants who were mostly Asian or Asian descent.
All 13 trials reported SVR data. HCV treatment was consisted of Peg-IFN plus weight-based RBV in 11 trials. The SVR for HCV-6 patients ranged from 39% to 92.8% in these trials. As shown in Figure 2, the pooled SVR across all study arms was 75% (95% CI: 0.68–0.81, I2 = 65.9%), while the pooled SVR for 24 and 48 weeks treatment were 65% (95% CI: 0.53–0.76, I2 = 56.2%) and 80% (95% CI: 0.73–0.85 I2 = 59.3%), respectively. The RVR for HCV-6 patients ranged from 48% to 93%, with pooled rate of 70% (95% CI: 0.60–0.79, I2 = 77.9%, Figure.3A). Information on adverse events and treatment discontinuations due to adverse events were shown in Table 2.
(A) Pooled proportion of RVR in all eligible study arms. (B) Overall analysis of studies head-to-head directly assessing 24-week versus 48-week treatment for HCV-6 patients. (C) Sensitivity analysis restricted to studies evaluating 24-week versus 48-week treatment among RVR patients.
Four studies included head-to-head comparisons of 24 week versus 48 week treatment with Peg-IFN plus RBV for HCV-6 patients [27], [31], [32], [34]. We conducted a second meta-analysis of these four studies, and found that the SVR rate for 24 weeks of treatment was significantly lower than that for 48 weeks. The risk difference was −14% (95% CI: −0.25 to −0.02, p = 0.019, Figure.3B). However, after performing a sensitivity analysis restricted to three studies that evaluated 24- versus 48-week treatments among RVR patients [24], [27], [34], we found no significant effect on the SVR rate after 24 weeks of treatment. The risk difference was −1% (95% CI: −0.1 to 0.07, p = 0.765, Figure. 3C).
Five trials were direct comparisons of antiviral therapy in HCV-6 versus HCV-1 patients [25], [26],[28],[31],[35]. Among these trials, we found that SVR rate in HCV-6 patients was higher than that in HCV-1 patients: 75.9% vs 55.3%, with a relative risk of 1.35 (95% CI: 1.16–1.57, p<0.001) (Figure. 4). No significant publication bias was found by Egger's funnel plot asymmetry test, and Begg's rank correlation test (Figure. S1, S2, S3, S4).
Discussion
To our knowledge, no studies to date have been conducted to evaluate the efficacy of boceprevir and telaprevir, the most recently approved DAAs, in HCV-6 patients. In recent phase II/III trials, simeprevir [37] and sofosbuvir [38] were shown to have clinical benefit in HCV-6 patients, although the sample sizes were small. DAAs seem to be effective in this group, but the data are too limited to make a general recommendation [39], [40]. In addition, DAAs are not available in most countries in Southeast Asia because of socio-economic and other obstacles [41]. Until these issues are resolved, Peg-IFN plus RBV combination therapy remains appropriate for patients with HCV-6. However, most available data has focused on treatment of genotypes 1, 2 and 3, which are prevalent in Western Europe and North America, where the majority of multicenter trials have been performed. Optimal treatment duration and expected virological response of Peg-IFN plus RBV combination therapy in HCV-6 patients has not yet been determined. Previous results comparing 24 and 48 weeks of treatment remain conflicting. Nguyen et al., in a retrospective study, found that HCV-6 patients treated for 48 weeks had significantly higher SVR rates than those treated for 24 weeks. Nevertheless, in two randomized controlled studies published recently, similar rates of SVR were noted following 24 weeks and 48 weeks of therapy [27], [34]. This may be due to small sample sizes that made meaningful differences difficult to discern. Although it has been suggested that the response to antiviral therapy in HCV-6 patients is higher than that in HCV-1 patients, most related studies included small sample sizes, and failed to give effective recommendations [25],[26],[28],[31],[35]. Furthermore, one recent retrospective study also found that SVR in HCV-1 patients and HCV-6 patients was not significantly different [42].
In the present meta-analysis, we assessed efficacy in the light of virological outcomes. As for the safety, side effects and treatment discontinuation of peg-IFR and RBV were examined as well. Furthermore, a second meta-analysis of suitable trials was conducted to compare 24 weeks versus 48 weeks treatment in HCV-6 patients. For a more comprehensive understanding of the efficacy of this treatment strategy in HCV-6 patients, we also evaluated SVR for HCV-6 and HCV-1 patients in some head-to-head comparison trials. Our analyses indicate that Peg-IFN plus RBV was effective in the majority of HCV-6 patients, and efficacy was higher than that for genotype 1. Side effects were common, and consisted mostly of hematologic and dermatologic events which rarely caused treatment discontinuation.
The optimal duration of treatment in HCV-6 patients has been studied previously [27], [31], [32], [34]. In the present study we performed a second meta-analysis to assess the efficacy of Peg-IFN plus RBV in HCV-6 patients for 24 versus 48 weeks treatment. Pooled data suggested that 48 weeks of treatment may be more effective in inducing SVR than 24 weeks of treatment. Nevertheless, when restricted to RVR patients in head-to-head treatments at 24 weeks compared to 48 weeks, no statistical differences were found in SVR [24], [27], [34]. These results indicated that shortened treatment may be appropriate in RVR group. A previous retrospective cohort study reported higher SVR after 48 weeks of treatment. This discrepancy may have been due to the small sample size and lack of intention-to-treat analysis [32]. Although the present meta-analysis showed that 24 weeks of therapy achieved similar efficacy compared to 48 weeks of treatment, clinicians should consider shortening treatment in HCV-6 patients with RVR cautiously, as the data from this meta-analysis are not sufficient to recommend treatment duration for all HCV-6 patients. Thus, we recommend larger randomized controlled trials to define the optimal treatment duration in such patients. A recent study had found that the IL28B rs8099917 TT genotype was significantly related to an increased SVR rate compared to the TG genotype [30]. These results suggest that IL28B could be another important potential predictor, and deserves further study.
There are limitations to the present study. Although our study has included all related work in one recent systematic review, the number of trials that met the inclusion criteria was small. Given these limited trials, the pooled data represent various study designs, and only included three randomized controlled trials. In addition, although the efficacy of Peg-IFN and RBV may vary depending on the dose schedules, and types of treatment regimen, we were not able to perform sensitivity analyses on these parameters due to limited data. Besides, limited information on other potential predictors of SVR such as early virological response, male sex, increasing age, AST/ALT ratio and viral load, also prevented quantitative analysis. Although most trials only included treatment of naive patients, some trials included a few treated patients. Furthermore, three included trials were only available as abstracts. However, these trials met all the inclusion criteria, and could provide data on the outcomes of interest. We therefore included these studies in our meta-analysis here. Despite these limitations, the present meta-analysis study provides the most comprehensive summary of evidence to date on the effectiveness of Peg-IFN plus RBV in treating HCV-6 patients.
In conclusion, based on the available data, our results indicate that Peg-IFN plus RBV is effective for patients with HCV-6, and the efficacy was superior compared to patients with HCV-1. With this treatment schedule, about three-quarters of patients are expected to achieve SVR. Furthermore, shortening treatment seems to be feasible in HCV-6 patients with RVR when tolerance to treatment is poor, but the decision should be make cautiously.
Supporting Information
Figure S1.
Publication bias tests for proportion meta-analysis of SVR in 24-week (A) or 48-week (B) treatment arms.
https://doi.org/10.1371/journal.pone.0100128.s001
(TIF)
Figure S2.
Publication bias test for proportion meta-analysis of RVR in all eligible study arms.
https://doi.org/10.1371/journal.pone.0100128.s002
(TIF)
Figure S3.
Publication bias tests when evaluating the effect of RVR on SVR. (A) Publication bias test for overall analysis of SVR in trials comparing the efficacy of 24- versus 48- week treatment directly. (B) Publication bias test for the sensitivity analysis of SVR among RVR patients after 24- versus 48- week treatment.
https://doi.org/10.1371/journal.pone.0100128.s003
(TIF)
Figure S4.
Publication bias test for SVR in trials directly comparing antiviral therapy in HCV-6 versus HCV-1 patients.
https://doi.org/10.1371/journal.pone.0100128.s004
(TIF)
Author Contributions
Conceived and designed the experiments: XWW HR HDH. Performed the experiments: XWW FL FW HDH. Analyzed the data: XWW FL HR HDH. Contributed to the writing of the manuscript: XWW FL FW HR HDH.
References
- 1. Shepard CW, Finelli L, Alter MJ (2005) Global epidemiology of hepatitis C virus infection. Lancet Infect Dis 5: 558–567.
- 2. Chao DT, Abe K, Nguyen MH (2011) Systematic review: epidemiology of hepatitis C genotype 6 and its management. Aliment Pharmacol Ther 34: 286–296.
- 3. McOmish F, Yap PL, Dow BC, Follett EA, Seed C, et al. (1994) Geographical distribution of hepatitis C virus genotypes in blood donors: an international collaborative survey. J Clin Microbiol 32: 884–892.
- 4. Davidson F, Simmonds P, Ferguson JC, Jarvis LM, Dow BC, et al. (1995) Survey of major genotypes and subtypes of hepatitis C virus using RFLP of sequences amplified from the 5' non-coding region. The Journal of general virology 76 (Pt 5): 1197–1204.
- 5. Nguyen MH, Keeffe EB (2005) Prevalence and treatment of hepatitis C virus genotypes 4, 5, and 6. Clinical gastroenterology and hepatology: the official clinical practice journal of the American Gastroenterological Association 3: S97–S101.
- 6. Mellor J, Walsh EA, Prescott LE, Jarvis LM, Davidson F, et al. (1996) Survey of type 6 group variants of hepatitis C virus in Southeast Asia by using a core-based genotyping assay. J Clin Microbiol 34: 417–423.
- 7. Welsch C, Jesudian A, Zeuzem S, Jacobson I (2012) New direct-acting antiviral agents for the treatment of hepatitis C virus infection and perspectives. Gut 61 Suppl 1i36–46.
- 8. Jacobson IM, McHutchison JG, Dusheiko G, Di Bisceglie AM, Reddy KR, et al. (2011) Telaprevir for previously untreated chronic hepatitis C virus infection. N Engl J Med 364: 2405–2416.
- 9. Poordad F, McCone J Jr, Bacon BR, Bruno S, Manns MP, et al. (2011) Boceprevir for untreated chronic HCV genotype 1 infection. N Engl J Med 364: 1195–1206.
- 10.
Zeuzem S, Asselah T, Angus P, Zarski JP, Larrey D, et al.. (2011) Efficacy of the protease inhibitor BI 201335, polymerase inhibitor BI 207127, and ribavirin in patients with chronic HCV infection. Gastroenterology 141: : 2047–2055; quiz e2014.
- 11. Ghany MG, Nelson DR, Strader DB, Thomas DL, Seeff LB, et al. (2011) An update on treatment of genotype 1 chronic hepatitis C virus infection: 2011 practice guideline by the American Association for the Study of Liver Diseases. Hepatology 54: 1433–1444.
- 12. Ghany MG, Strader DB, Thomas DL, Seeff LB (2009) American Association for the Study of Liver D (2009) Diagnosis, management, and treatment of hepatitis C: an update. Hepatology 49: 1335–1374.
- 13. Davis GL, Lau JY (1997) Factors predictive of a beneficial response to therapy of hepatitis C. Hepatology. 26: 122S–127S.
- 14. Manns MP, McHutchison JG, Gordon SC, Rustgi VK, Shiffman M, et al. (2001) Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomised trial. Lancet 358: 958–965.
- 15. Zeuzem S, Hultcrantz R, Bourliere M, Goeser T, Marcellin P, et al. (2004) Peginterferon alfa-2b plus ribavirin for treatment of chronic hepatitis C in previously untreated patients infected with HCV genotypes 2 or 3. J Hepatol 40: 993–999.
- 16. Andriulli A, Mangia A, Iacobellis A, Ippolito A, Leandro G, et al. (2008) Meta-analysis: the outcome of anti-viral therapy in HCV genotype 2 and genotype 3 infected patients with chronic hepatitis. Aliment Pharmacol Ther 28: 397–404.
- 17. European Association for the Study of the L (2011) EASL Clinical Practice Guidelines: management of hepatitis C virus infection. J Hepatol 55: 245–264.
- 18. Freeman MF, Tukey JW (1950) Transformations related to the angular and the square root. The Annals of Mathematical Statistics 21: 607–611.
- 19. DerSimonian R, Laird N (1986) Meta-analysis in clinical trials. Controlled clinical trials 7: 177–188.
- 20. Davies A, Singh KP, Shubber Z, Ducros P, Mills EJ, et al. (2013) Treatment outcomes of treatment-naive Hepatitis C patients co-infected with HIV: a systematic review and meta-analysis of observational cohorts. PLoS One 8: e55373.
- 21. Druyts E, Mills EJ, Nachega J, O'Regan C, Cooper CL (2012) Differences in clinical outcomes among hepatitis C genotype 1-infected patients treated with peginterferon alpha-2a or peginterferon alpha-2b plus ribavirin: a meta-analysis. Clinical and experimental gastroenterology 5: 11–21.
- 22. Begg CB, Mazumdar M (1994) Operating characteristics of a rank correlation test for publication bias. Biometrics 50: 1088–1101.
- 23. Egger M, Davey Smith G, Schneider M, Minder C (1997) Bias in meta-analysis detected by a simple, graphical test. BMJ (Clinical research ed) 315: 629–634.
- 24. Qing-Xian C, Zhixin Z, Lin C, Min X, Min W, et al. (2013) Shortened treatment duration in treatment-naive genotype 6 chronic hepatitis C patients with rapid virological response: A randomized controlled trial. Hepatology 58: 1098A.
- 25. Zhou YQ, Wang XH, Hong GH, Zhu Y, Zhang XQ, et al. (2011) Twenty-four weeks of pegylated interferon plus ribavirin effectively treat patients with HCV genotype 6a. J Viral Hepat 18: 595–600.
- 26. Tsang OT, Zee JS, Chan JM, Li RS, Kan YM, et al. (2010) Chronic hepatitis C genotype 6 responds better to pegylated interferon and ribavirin combination therapy than genotype 1. J Gastroenterol Hepatol 25: 766–771.
- 27. Thu Thuy PT, Bunchorntavakul C, Tan Dat H, Rajender Reddy K (2012) A randomized trial of 48 versus 24 weeks of combination pegylated interferon and ribavirin therapy in genotype 6 chronic hepatitis C. J Hepatol. 56: 1012–1018.
- 28. Tangkijvanich P, Komolmit P, Mahachai V, Poovorawan K, Akkarathamrongsin S, et al. (2012) Response-guided therapy for patients with hepatitis C virus genotype 6 infection: a pilot study. J Viral Hepat 19: 423–430.
- 29. Shao X, Zhao Z, Cai Q, Zhang X, Gao Z (2012) THE DYNAMIC ANALYSIS OF THE TH1/TH2 RATIO DURING THE INTERFERON ALPHA/RIBAVIRIN COMBINATION THERAPY FOR HCV GENOTYPE 6 INFECTED PATIENTS. Journal of Hepatology 56: S66–S67.
- 30. Seto WK, Tsang OT, Liu K, Chan JM, Wong DK, et al. (2013) Role of IL28B and inosine triphosphatase polymorphisms in the treatment of chronic hepatitis C virus genotype 6 infection. Journal of viral hepatitis 20: 470–477.
- 31. Nguyen NH, VuTien P, Garcia RT, Trinh H, Nguyen H, et al. (2010) Response to pegylated interferon and ribavirin in Asian American patients with chronic hepatitis C genotypes 1 vs 2/3 vs 6. J Viral Hepat 17: 691–697.
- 32. Nguyen MH, Trinh HN, Garcia R, Nguyen G, Lam KD, et al. (2008) Higher rate of sustained virologic response in chronic hepatitis C genotype 6 treated with 48 weeks versus 24 weeks of peginterferon plus ribavirin. The American journal of gastroenterology 103: 1131–1135.
- 33. Mauss S, Berger F, Vogel M, Pfeiffer-Vornkahl H, Alshuth U, et al. (2012) Treatment results of chronic hepatitis C genotype 5 and 6 infections in Germany. Z Gastroenterol 50: 441–444.
- 34. Lam KD, Trinh HN, Do ST, Nguyen TT, Garcia RT, et al. (2010) Randomized controlled trial of pegylated interferon-alfa 2a and ribavirin in treatment-naive chronic hepatitis C genotype 6. Hepatology 52: 1573–1580.
- 35. Fung J, Lai CL, Hung I, Young J, Cheng C, et al. (2008) Chronic hepatitis C virus genotype 6 infection: response to pegylated interferon and ribavirin. The Journal of infectious diseases 198: 808–812.
- 36. Cai Q-X, Zhao Z, Zhang X, Gao Z, Lin C, et al. (2011) THE HIGH IL-28B CC GENOTYPE CONTRIBUTE TO THE GOOD RESPONSE OF CHRONIC HEPATITIS C GENOTYPE 6 IN CHINA. Hepatology 54: 829A–830A.
- 37. Lenz O, Vijgen L, Berke JM, Cummings MD, Fevery B, et al. (2013) Virologic response and characterisation of HCV genotype 2-6 in patients receiving TMC435 monotherapy (study TMC435-C202). J Hepatol 58: 445–451.
- 38. Lawitz E, Gane EJ (2013) Sofosbuvir for previously untreated chronic hepatitis C infection. N Engl J Med 369: 678–679.
- 39. Clark VC, Peter JA, Nelson DR (2013) New therapeutic strategies in HCV: second-generation protease inhibitors. Liver international: official journal of the International Association for the Study of the Liver 33 Suppl 180–84.
- 40. Gerber L, Welzel TM, Zeuzem S (2013) New therapeutic strategies in HCV: polymerase inhibitors. Liver international: official journal of the International Association for the Study of the Liver 33 Suppl 185–92.
- 41. Bunchorntavakul C, Chavalitdhamrong D, Tanwandee T (2013) Hepatitis C genotype 6: A concise review and response-guided therapy proposal. World journal of hepatology 5: 496–504.
- 42. Tsang OT, Zee J, Chan J, Li RS, Lai JY, et al. (2008) A RETROSPECTIVE COMPARATIVE STUDY OF PEGYLATED INTERFERON AND RIBAVIRIN FOR THE TREATMENT OF CHRONIC HEPATITIS C GENOTYPE 6 AND GENOTYPE 1. Hepatology 48: 884A–884A.