Pharmacogenomic perspectives of chronic hepatitis C virus (HCV) infection

IL28B genetic variations are associated with treatment response of patients with chronic hepatitis C in a Chinese Han population

OBJECTIVES

This study aimed to investigate the association between interleukin 28B (IL28B) single nucleotide polymorphisms (SNPs) and sustained virological response (SVR) in Chinese Han patients with chronic hepatitis C (CHC) and to analyze the correlations between IL28B SNPs and their personal, virological and clinical characteristics.

METHODS

Altogether 631 Chinese Han individuals, including 297 CHC patients treated with pegylated interferon α plus ribavirin, 14 spontaneous responders to hepatitis C virus (HCV) and 320 healthy controls were enrolled in the study. Two main SNPs of IL28B, rs12979860 and rs8099917, were genotyped using an SNaPshot Multiplex Assay. Associations between IL28B, treatment outcomes and the patients' characteristics were assessed by multivariate logistic regression.

RESULTS

The proportion of individuals with the rs12979860 CC or rs8099917 TT genotype was similar in the healthy controls and the CHC patients, although all spontaneous responders presented with both genotypes. Patients with IL28B genotypes had a significantly high rate of rapid virological response (RVR) and SVR. Multivariate analysis revealed that the IL28B SNP rs12979860 CC genotype, being aged <40 years and having a non-genotype 1 (G1) were independent predictors for SVR. The rs12979860 CC genotype and rs8099917 TT genotypes were predictors for RVR. The rs12979860 CC and rs8099917 TT genotypes were more prevalent in patients with a non-G1 genotype than those with G1 genotype.

CONCLUSIONS

IL28B rs12979860 CC genotype is a significant predictor for SVR and RVR in Chinese Han patients with CHC. Non-G1 HCV genotype is associated with favourable IL28B genotypes.

Role of interleukin-28B polymorphisms in the treatment of hepatitis C virus genotype 2 infection in Asian patients

Genome-wide association studies have linked single nucleotide polymorphisms (SNPs) near the interleukin-28B gene to the hepatitis C virus genotype 1 (HCV-1) response to peginterferon/ribavirin treatment. We aimed to explore the impact on the treatment outcomes of Asian HCV-2 patients. We determined rs8105790, rs8099917, rs4803219, and rs10853728 to be candidate SNPs in 482 Asian HCV-2 patients treated with the standard of care. Because the first three SNPs were in very strong linkage disequilibrium with one another (r2 = 0.94-0.96), rs8099917 and rs10853728 were selected for an analysis of their influence on the achievement of rapid virological response [RVR; seronegativity for hepatitis C virus (HCV) RNA in treatment week 4] and sustained virological response (SVR; seronegativity for HCV RNA throughout 24 weeks of posttreatment follow-up). The rs10853728 genotype did not predict RVR or SVR in HCV-2 patients. However, patients with the rs8099917 TT genotype, in comparison with patients with GT/GG genotypes, had a significantly higher rate of achieving RVR (85.2% versus 72.0%, P = 0.017) but did have not a significantly higher rate of achieving SVR (89.4% versus 86.0%). Multivariate analysis revealed that a baseline HCV viral load <400,000 IU/mL was the strongest predictor of RVR [odds ratio (OR) = 4.27, 95% confidence interval (CI) = 2.31-7.87, P < 0.001], and this was followed by advanced liver fibrosis (OR = 0.28, 95% CI = 0.15-0.53, P < 0.001), the carriage of the rs8099917 TT genotype (OR = 3.10, 95% CI = 1.34-7.21, P = 0.008), and the pretreatment level of aspartate aminotransferase (OR = 0.996, 95% CI = 0.99-1.00, P = 0.04). Nevertheless, the achievement of RVR was the single predictor of SVR with an OR of 19.37 (95% CI = 8.89-42.23, P < 0.001), whereas the rs8099917 genotypes played no role in achieving SVR with or without RVR.

CONCLUSION

The rs8099917 TT genotype is significantly independently predictive of RVR, which is the single best predictor of SVR, in Asian HCV-2 patients.

Evolution of interferon-based therapy for chronic hepatitis C

Since 1986, interferon-alfa (IFN-α) monotherapy has been administered for patients with chronic hepatitis C (CHC). However, sustained response rate is only about 8% to 9%. Subsequent introduction of ribavirin in combination with IFN-α was a major breakthrough in the treatment of CHC. Sustained virological responses (SVRs) rate is about 30% in hepatitis C virus genotype 1 (HCV-1) patients, and is about 65% in HCV-2 or -3 patients. After 2000, pegylated interferon (PegIFN) much improved the rates of SVR. Presently, PegIFN-α-ribavirin combination therapy has been current standard of care for patients infected with HCV. In patients with HCV-1, treatment for 48 weeks is optimal, but 24 weeks of treatment is sufficient in HCV-2 or -3 infected patients. Clinical factors have been identified as predictors for the efficacy of the IFN-based therapy. The baseline factor most strongly predictive of an SVR is the presence of HCV-2 or -3 infections. Rapid virological response (RVR) is the single best predictor of an SVR to PegIFN-ribavirin therapy. If patients can't achieve a RVR but achieve a complete early virological response (cEVR), treatment with current standard of care can provide more than 90% SVR rate. HCV-1 patients who do not achieve an EVR should discontinue the therapy. Recent advances of protease inhibitor may contribute the development of a novel triple combination therapy.

Can (and will) governments afford personalized medicine?

'Personalized' (or more specifically targeted) medicines promise aging populations important medium- to long-term benefits, including extended healthy life expectancies. But the time and resources needed to deliver such advances may be significantly greater than optimists expect. Given current methodologies, drugs for limited numbers of older patients are also much less likely to be judged cost effective than treatments for more common conditions in younger populations. There is a consequent danger that private and public funding for personalized medicine development will in the future fall to a level that is significantly below the global public's best interests. Policy-makers should be aware of this risk, and take actions to mitigate it. These include minimizing the costs and complexities associated with marketing personalized medicines and linked diagnostic tests, as well as strengthening intellectual property protection in ways that will allow 'rich world' pharmaceutical price moderation, increased innovator security and enhanced treatment access for poorer populations.

Treatment of chronic hepatitis C in Asia: when East meets West

The issue of best treatment for chronic hepatitis C virus (HCV) infection is in constant flux, not only in Western countries but also in Asia. Currently, pegylated-interferon plus ribavirin is the standard of care. Studies from Asia provide evidence to support the same broad treatment strategies for Asian patients as recommended in Western countries. Nevertheless, there is increasing evidence that Asians have a higher likelihood of achieving a sustained virological response (SVR) than their Caucasians counterparts when treated with the corresponding regimen. With the recommended 'standard dose and duration treatment regimens', SVR is achieved in Asia for around 70% of HCV genotype 1 (HCV-1) infected cases, approximately 90% of HCV-2/3, approximately 65% of HCV-4, and approximately 80% of HCV-6 patients. Difference of body weight in race might contribute the superior response in Asian patients. HCV genotype distribution in Asia also differs from North-America/Europe. HCV-6 and its variants, previously mistyped as HCV-1, needs accurate genotyping. Increasing data support the proposal that HCV genotype, baseline viral load and on-treatment virological response provide information for decision-making so that treatment can be individualized. Beyond the older recommendations, an abbreviated 24-week regimen could be suggested for HCV-1/4 patients with baseline viral loads < 400 000 IU/mL and a rapid virological response (RVR, HCV RNA undetectable at week 4), and an abbreviated 12-16 weeks of pegylated-interferon with weight-based doses of ribavirin could be suggested for HCV-2/3 patients with a RVR. Such tailored treatment regimens can reduce the costs of treatment and incidence of adverse events without compromising efficacy. Hepatitis C virus (HCV) infection is one of the most important causes of cirrhosis worldwide, and particularly in some countries of Asia (notably Japan) where it is now more prevalent than chronic hepatitis B virus infection. Hepatitis C virus infection can also lead to hepatocellular carcinoma (HCC). It is estimated that there are more than 170 million people chronically infected with HCV, and 3 to 4 million persons are newly infected each year. The risk for developing cirrhosis 20 years after initial HCV infection among those chronically infected varies between studies, but is estimated at around 10%-15% for men and 1-5% for women. Once cirrhosis is established, the rate of developing HCC is at 1%-4% per year. Approximately 280 000 deaths per year are related to HCV infection. Hepatitis C virus-related end-stage liver disease and HCC have become the leading cause for liver transplantation worldwide. In the Asia-Pacific area, the estimated prevalence of antibodies to HCV (anti-HCV) range from 0.3% in New Zealand to 5.6% in Thailand. In Japan, Middle East, Vietnam and Taiwan, several HCV hyper-endemic areas have been reported with an anti-HCV prevalence rate of 12% to as high as 58%. In addition to the well-known endemic status of HBV infection in most countries of the Asia-Pacific region, HCV infection presents another critical scenario of public health issue in this region, as outlined in Guidelines by the Asia-Pacific Association for Study of the Liver (APASL). Given the lack of an effective vaccine, optimal treatment of chronic HCV infection is now perceived as a 'must' in terms of public health strategies, as well as of the clinical setting for individual patients.

Genetic predisposition of responsiveness to therapy for chronic hepatitis C

BACKGROUND

A combination of interferon-alpha (IFN-alpha) and ribavirin has been the choice for treating chronic hepatitis C (CHC) patients. It achieves an overall sustained response rate of approximately 50%; however, the treatment takes 6-12 months and often brings significant adverse reactions to some patients. It would therefore be beneficial to include a pretreatment evaluation in order to maximize the efficacy. In addition to viral genotypes, we hypothesize that patient genotypes might also be useful for the prediction of treatment response.

METHODS

We retrospectively analyzed the genetic differences of CHC patients that are associated with IFN/ribavirin responses. The DNA polymorphisms among 195 sustained responders and 122 nonresponders of CHC patients of Taiwanese origin were compared. Statistical and algorithmic methods were used to select the genes associated with drug response and single nucleotide polymorphisms (SNPs) that permitted the construction of a predictive model.

RESULTS

Association studies and haplotype reconstruction revealed selection of seven genes: adenosine deaminase, RNA-specific (ADAR), caspase 5, apoptosis-related cysteine peptidase (CASP5), fibroblast growth factor 1 (FGF1), interferon consensus sequence binding protein 1 (ICSBP1), interferon-induced protein 44 (IFI44), transporter 2, ATP-binding cassette, subfamily B (TAP2) and transforming growth factor, beta receptor associated protein 1 (TGFBRAP1) for the responsiveness trait. Based on confirmed linkage disequilibrium block in the population, a minimal set of 26 SNPs in the seven selected genes was inferred. To predict treatment outcome, a multiple logistic regression model was constructed using susceptible genotypes of SNPs. The performance of the resultant model had a sensitivity of 68.2% and specificity of 60.7% on 317 CHC patients treated with IFN-combined therapy. In addition, a prediction model with both the host genetic and viral genotype information was also constructed which enhanced the performance with a sensitivity of 80.7% and specificity of 67.2%.

CONCLUSIONS

A genetic model was constructed to predict outcomes of the combination therapy in CHC patients with high sensitivity and specificity. Results also provide a possible process of selecting targets for predicting treatment outcomes and the basis for developing pharmacogenetic tests.