The pharmacogenetic background of hepatitis C treatment

Hepatitis C virus genotype 3: a genotype that is not 'easy-to-treat'

The efficacy of antiviral treatment depends on which of the seven genotypes (G1-G7) of hepatitis C virus (HCV) has infected the patient. Conventionally, clinicians regarded G2 and G3 infections as 'easy-to-treat': dual therapy with pegylated interferon and ribavirin produces a sustained virologic response in approximately 40-50% of patients with G1 infection, compared with 80% when analyses report combined data for G2 and G3 patients, which is standard practice in many clinical studies. However, sustained virologic response rates appear to be lower in certain subgroups of people infected with G3 compared with those with G2 or the general HCV-infected population. This review examines the growing evidence that factors related to the virus (e.g., baseline viral load and a rapid virologic response) and host characteristics (e.g., steatosis and fibrosis, metabolic syndrome, host polymorphisms and ethnicity) contribute to variations in therapeutic success in G3 HCV.

Genetic variants at the IFNL3 locus and their association with hepatitis C virus infections reveal novel insights into host-virus interactions

Human genetic variation plays a critical role in both spontaneous clearance of and response to interferon (IFN)-based therapies against hepatitis C virus (HCV) as shown by the success of recent genome-wide association studies (GWAS). Several GWAS and later validation studies have shown that single nucleotide polymorphisms (SNPs) at the IFNL3 (formerly IL28B) locus on chromosome 19 are involved in eliminating HCV in human patients. No doubt that this information is helping clinicians worldwide in making better clinical decisions in anti-HCV therapy, but the biological mechanisms involving the SNPs leading to differential responses to therapy and spontaneous clearance of HCV remain elusive. Recent reports including the discovery of a novel IFN (IFN-λ4) gene at the IFNL3 locus and in vitro functional studies implicating 2 SNPs as causal variants lead to novel conclusions and perhaps to new directions in research. An attempt is made in this review to summarize the major findings of the GWAS, the efforts involved in the discovery of causal SNPs; and to explain the biological basis for spontaneous clearance and response to treatment in HCV infections.

Individualization of chronic hepatitis C treatment according to the host characteristics

Hepatitis C virus (HCV) infection is a global health problem that affects more than 170 million people worldwide. It is a major cause of cirrhosis and hepatocellular carcinoma, making the virus the most common cause of liver failure and transplantation. The standard-of-care treatment for chronic hepatitis C (CHC) has been changed during the last decade and direct acting antiviral drugs have already been used. Besides, understanding of the pathogenesis of CHC has evolved rapidly during the last years and now several host factors are known to affect the natural history and response to treatment. Recent genome-wide association studies have shown the important role of interleukin-28B and inosine triphosphatase in HCV infection. The present review article attempts to summarize the current knowledge on the role of host factors towards individualization of HCV treatment.

The role of pharmacogenetics in the treatment of chronic hepatitis C infection

Hepatitis C virus (HCV) chronically infects 170 million people worldwide. Until recently, combination therapy with peginterferon-α (pegIFN) and ribavirin (RBV) has been the standard of care. However, for many patients, especially those infected with the most common HCV genotype 1 (HCV-1), this treatment has resulted in unsatisfactory treatment response rates. Many clinical factors, including pharmacogenetics, influence the treatment response rate. Genetic variation in the interleukin 28B (IL28B) gene is the major determinant of treatment response, a finding that has been replicated in multiple independent cohorts. This review focuses on the association between pharmacogenetics and conventional pegIFN/RBV therapy in patients infected with HCV non-genotype 1; patients reinfected with HCV after liver transplantation; and patients coinfected with HCV and human immunodeficiency virus. We also review the pharmacogenetic data for boceprevir and telaprevir triple therapy in patients with HCV-1 infection, as well as viral genomic polymorphisms and genetic variants that may protect against anemia. Pharmacogenetic information offers a personalized medicine approach to help clinicians and patients make better informed decisions to maximize response and minimize toxicity for the treatment of chronic HCV infection.

Functional genomics of pain in analgesic drug development and therapy

Advances in genomic research have led to the clarification of the detailed involvement of gene products in biological pathways and these are being increasingly exploited in strategies for drug discovery and repurposing. Concomitant developments in informatics have resulted in the acquisition of complex gene information through the application of computational analysis of molecular interaction networks. This approach enables the acquired knowledge on hundreds of genes to be used to view molecular disease mechanisms from a genetic point of view. By analyzing 410 genes which control the complex process of pain, we show by computational analysis, based on functional annotations to pain-related genes, that 12 clearly circumscribed functional areas are essential for pain perception and thus for analgesic drug development. The genetics perspective revealed that future development strategies should focus on substances modulating intracellular signal transduction, ion transport and anatomical structure development. These processes are involved in the genetic-based absence of pain and therefore, provide promising fields for curative or preventive treatments. In contrast, interactions with G-protein coupled receptor pathways seem merely to provide symptomatic, not preventative relief of pain. In addition, biological functions accessed either by analgesic drugs or microRNAs suggest that synergistic therapies may be a future direction for drug development. With modern computational functional genomics, it is possible to exploit genetic information from increasingly available data sets on complex diseases, such as pain, and offers a new insight into drug development and therapy which is complementary to pathway-centered approaches.

New tools in HCV diagnosis, in light of the enhanced awareness and the new drugs for treatment: SMARTube and stimmunology

With improved HCV therapy, challenges regarding HCV diagnosis, such as seronegative window period, false positive readings, and differentiation between recent, chronic, and resolved infections, are of increasing importance. To address these challenges an innovative device—SMARTube HIV & HCV—was used. Blood samples were tested for anti-HCV antibodies before and after incubation in the SMARTube, which promotes the in vitro stimulation of in vivo HCV primed lymphocytes, thus enhancing levels of anti-HCV antibodies. Comparing antibody levels, in concordant samples before and after SMARTube, yielded the Stimulation Index (SI). Among 5888 fresh blood samples, from various populations and regions worldwide, 641 were seropositive using plasma, while SMARTube processing (yielding enriched plasma, termed SMARTplasma) enabled diagnosis of 10 additional carriers in high-risk cohorts, that is, earlier detection. Using SMARTplasma eliminated all false positive results, using the current assays. In addition we show that SI calculation may serve as an important tool for differentiating between those who recently seroconverted, carriers of long-term infection, and those who have cleared the virus. SMARTube and the SI could lead to better, more informative diagnosis of HCV infections and play an important role in changing the way we treat both the infected individuals and the epidemic as a whole.