Interleukin-28B (IL28B) has been a phenomenal discovery in the field of hepatitis C (HCV); yet, with the emergence of direct-acting antiviral (DAA) agents, its importance has been overshadowed.  While the long-term significance of IL28B is unclear, for now, it has significant clinical utility.  Three reviews/commentaries help elucidate its role:

▪                Hepatology 2012; 56: 361-66. IL 28B Genetics and Biology

▪                Hepatology 2012; 56: 367-372 Clinical Utility of IL28B

▪                Hepatology 2012; 56:  373-380 Relevance of IL28B in age of DAAs

Key points from these references:

African-Americans are less likely to respond to treatment with pegylated interferon (PEGIFN) (and ribavirin [RBV]) in large part due to a low frequency of favorable alleles (C/C genotype) to IL28B.

Predictors of response to treatment with PEGIFN/RBV:

▪                CC IL28B genotype: OR 5.9 (compared to non-CC genotype)

▪                HCV RNA level ≤600,000 IU/mL: OR 3.1 (compared to >600,000 IU/mL)

▪                Degree of fibrosis, metavir F0-2: OR 2.7 (compared with F3-F4)

▪                Rapid virological response: OR 9.1 (compared with non-RVR non CC genotype)

Overall CC genotype is associated with double the sustained virological response (SVR).

Vitamin D also plays an important role in innate immunity and deficiency is associated with lower SVR.

Algorithm for use of IL28B (applicable to patients ≥18 years):

▪                Consider obtaining IL28B in all genotype 1 patients:  

▪                If CC genotype and does not have risk factors for poor response (including cirrhosis, high viral load), then likely to treat with PEGIFN/RBV and monitor for RVR.  In patients without RVR, addition of DAA would be reasonable.

▪                If risk factors for poor response or if non-CC genotype (C/T or T/T), then consider use of DAA at onset of therapy

DAAs are expensive.  Boceprevir (BOC) costs $26,000 for 24 weeks & $48,000 for 44 weeks.  Telaprevir (TVR) costs $49,000 for 12 weeks.  These costs are in addition to costs for PEGIFN/RBV which is approximately $30,000.  The cost of testing IL28B status is approximately $300.

In patients with CC IL28B genotype, the main advantage of DAAs may be to shorten treatment course by increasing the likelihood of RVR; though with TVR, the SVR was improved even among CC genotype patients in the “ADVANCE” trial (90% compared with 64%).  In non-CC IL28B genotype, TVR or BOC is associated with > 2-fold increase in SVR.  The specific response rates for both TVR and BOC are available in these references.