The IL28B polymorphism did predict for short duration in the RGT arm, with 90% of good-responder patients qualifying for 28 weeks of therapy. Poor-response IL28B patients GSK-3 phosphorylation gained the most from the addition of BOC, with SVR rates increasing approximately twofold.74 The RESPOND-2 trial included only patients with prior relapse and partial response, that is, primary non-responders with a < 2log10 drop in HCV—RNA at week 12 were excluded.73 In this more difficult-to-treat population with a well-documented treatment

history, major improvements were seen in SVR rates irrespective of IL28B genotype. The IL28B genotype was not an independent predictor of SVR. Despite not predicting for SVR, the IL28B genotype did identify patients who were more likely to be eligible for short-duration therapy (36 weeks in total). The ADVANCE trial assessed TVR and peg-IFN/RBV in comparison with peg-IFN/RBV control.77 Patients were randomized to receive either standard of care, or 24 or 48 weeks of peg-IFN or RBV in combination with either 8 or 12 weeks of TVR. A total of 454 Caucasian patients or 42% of the overall trial cohort were genotyped, with improvements compared to control across all IL28B genotypes, but greater than twofold in poor-response genotypes.76 Again, the association between the IL28B genotype and treatment response was attenuated with TVR regimens, and the major SVR increment was noted in patients

who carried the poor-response IL28B genotypes. In contrast to SPRINT-2, SVR rates did increase compared to control Ridaforolimus in patients with the good-response IL28B genotype. The IL28B genotype identified patients more likely to be eligible for short-duration therapy. The REALIZE study included patients who failed to achieve SVR from prior treatment (i.e. patients with prior primary non-response were included), with patients receiving either 48 weeks of peg-IFN/RBV (control) or 12 weeks of combination triple therapy with TVR, and then another 36 weeks of peg-IFN/RBV.78 Absolute increases in SVR rate of 40–50% were seen with TVR, irrespective of IL28B genotype.75

Again, however, there remained a 18–19% difference in SVR rates observed between the good- and poor-response genotypes, even with the addition of TVR (SVR by IL28B genotype for TVR12/PR48: CC 79% vs CT 61% Amylase vs TT 60%). The IL28B genotype remains relevant to treatment outcomes in the setting of TVR/BOC therapy for treatment-naïve patients, but the strength of the association is attenuated. The major benefit of DAA is in poor-response IL28B genotype patients, where SVR rates are dramatically increased. In good-responder IL28B patients, the SVR benefit of DAA therapy is less clear. We feel that DAA therapy is likely to be associated with a small increase in SVR rate, but that the major benefit of DAA therapy in these patients will be to allow short-duration therapy. SVR rates were not increased in good-responder IL28B patients in SPRINT-2 (BOC), but were in ADVANCE (TVR).