No HBV or HIV co-infection NIAID FOUR-WEEK Study: LDV/SOF + vedroprevir or LDV/SOF + vedroprevir + GS-9669 in genotype 1 Design Non-randomised Open-label Sequential cohorts W4 ≥ 18 years Chronic HCV Genotype 1 Treatment-naïve HCV RNA ≥ 2,000 IU/ml Liver fibrosis F0 to F2 No HBV or HIV co-infection N = 25 LDV/SOF + VDV SVR12 N = 25 LDV/SOF + VDV + GS-9669 LDV/SOF: 90/400 mg 1 tablet qd ; VDV (vedroprevir): 80 mg 1 tablet qd ; GS-9669: 250 mg 1 tablet qd Objective SVR12 (HSV RNA < 12 IU/ml), with 95% CI, by intention-to-treat analysis Sample size with 93% probability of observing ≥ 1 participant with an AE occurring in ≥ 10% of patients NIAID FOUR-WEEK Kohli A. Ann Intern Med 2015;163:899-907 1

Baseline characteristics and outcome NIAID FOUR-WEEK Study: LDV/SOF + vedroprevir or LDV/SOF + vedroprevir + GS-9669 in genotype 1 Baseline characteristics and outcome LDV/SOF + VDV N = 25 LDV/SOF + VDV + GS-9669 Mean age, years 54 58 Female 32% 24% White / Black 20% / 76% 24% / 76% Genotype : 1a / 1b 72% / 28% 64% / 36% HCV RNA > 6 M IU/ml 44% 40% Fibrosis stage 0 / 1 / 2 / 3 20% / 56% / 24% / 0 32% / 48% / 16% / 4% IL28B CC 12% 8% Any NS3, NS5A, NS5B RAV with > 20-fold resistance 28% Discontinued study 1 (lost to follow-up) HCV RNA < 12 IU/ml, end of treatment 100% 92% (23/25) SVR12 (95% CI) 40% (21%-61%) 20% (7%-41%) NIAID FOUR-WEEK Kohli A. Ann Intern Med 2015;163:899-907 2

Treatment outcomes by subgroups NIAID FOUR-WEEK Study: LDV/SOF + vedroprevir or LDV/SOF + vedroprevir + GS-9669 in genotype 1 Treatment outcomes by subgroups SVR12 higher if lower age, genotype 1b, HCV RNA < 6 M IU/ml Analysis of Resistance associated variants Genotype 1a, N = 33 NS3 Q80K at baseline (3-fold reduced susceptibility to VDV), N = 10 Viral relapse: 60% if Q80K+ vs 97% if Q80K- NS3 R155K and D168E and/or NS5A L31M, Y93H and Y93N (> 20-fold reduced susceptibility to VDV and LDV, respectively), N = 10 Viral relapse: 100% if these RAVS present vs 63% if absent (p = 0.022) NS5B M423I (4.6 fold resistance to GS-9669), N = 1 Viral relapse in this patient NIAID FOUR-WEEK Kohli A. Ann Intern Med 2015;163:899-907 3

NIAID FOUR-WEEK Study: LDV/SOF + vedroprevir or LDV/SOF + vedroprevir + GS-9669 in genotype 1 Adverse events, N LDV/SOF + VDV N = 25 LDV/SOF + VDV + GS-9669 Serious adverse event 2 Discontinuation due to adverse events Adverse events in ≥ 10% of patients Constipation 3 Nausea 6 Fatigue 4 Diarrhea 5 Headache 1 Dry mouth Dizziness Abdominal pain Grade 3 laboratory abnormality Hypophosphatemia Hyperamylasemia Hyperglycemia NIAID FOUR-WEEK Kohli A. Ann Intern Med 2015;163:899-907 4

NIAID FOUR-WEEK Study: LDV/SOF + vedroprevir or LDV/SOF + vedroprevir + GS-9669 in genotype 1 Summary Treatment for 4 weeks with the all oral combination DAA regimens used in this study seems to have high tolerability but limited response in achieving SVR12 in non cirrhotic treatment- naive patients with HCV genotype 1 infection NIAID FOUR-WEEK Kohli A. Ann Intern Med 2015;163:899-907 5