The Future: Is Ribavirin Still Useful? David Nelson, MD Professor of Medicine, Microbiology, and Molecular Genetics Associate Dean, Clinical Research and Training Director, Clinical and Translational Science Institute University of Florida 5 th Paris Hepatitis Conference

History of Ribavirin 1970: first synthesized at ICN Pharmaceuticals 1972: ribavirin active against a variety of RNA viruses (including flavivirus) – Failed FDA approval for influenza 1980: approved indication in inhalant form for RSV 1998: oral ribavirin approved as part of a combination treatment (with interferon) for hepatitis C – Improved SVR rates by 20-30% Prevention of relapse

Adapted from US Food and Drug Administration, Antiviral Drugs Advisory Committee Meeting, April 27-28, 2011, Silver Spring MD. SVR (%) IFN 6m Peg-IFN/ RBV 12m IFN 12m IFN/RBV 12m Peg-IFN 12m Standard Interferon Ribavirin Peginterferon 1991 Direct Acting Antivirals Peg-IFN/ RBV/ DAA IFN/RBV 6m Interferon-Based Therapy Critical Role for Ribavirin in HCV Therapy

Proposed mechanisms of action for ribavirin against HCV include Direct effect against the HCV RNA dependent RNA polymerase Induction of mis-incorporation of nucleotides leading to lethal mutagenesis Depletion of intracellular pools via inhibition of inosine monophosphate dehydrogenase Alteration in the cytokine balance between a Th2 profile (anti-inflammatory) to a Th1 profile (pro-inflammatory) Potentiating the effect of interferon via up-regulation of genes involved in interferon signalling Clark V, Nelson DR. Liver Int 2012; 32:103-7

Perspectives on Ribavirin Role in DAA Combinations Pros – It works: leads to higher SVR across all trials to date Cons – Very “weak” antiviral – Lack of understanding MOA: difficult to predict best combination with DAA – Adverse events Hemolytic anemia (monotherapy trials) – Mean hgb reduction > 2gms by week 4 – 20% pts have > 4 gm drop Teratogen Pill burden and bid dosing

In-Vitro Prediction of RBV + DAAs Protease inhibitors 1 – PI + RBV = additive antiviral activity – PI + PEG/RBV = synergistic effect Reduce emergence of drug resistant variants 1. Hofmann WP, et al. Antivir Ther 2011; 16:

7 PROVE-2 1 PROVE-3 2 SVR (%) PR 48 wk (no lead-in) (n = 16) B + P + low-dose R (48 wk) (n = 59) SPRINT %50%36% 24%53% 60% Ribavirin Is Critical for Protease Inhibitor Combination Therapy: Phase 2 Trials Dosages not consistent between above studies. Abbreviations: B, boceprevir; P, peg-IFN  -2a and -2b; R, ribavirin; T, telaprevir. Hezode C et al N Engl J Med 2009;360:1839.; McHutchinson JG, et al. N Engl J Med 2010;362:1292; Kwo PY et al. Lancet 2010;376:705 T 12 wk + PR 12 wk (n = 82) T 12 wk + P 12 wk (n = 78) T 24 wk + PR 48 wk (n = 113) T 24 wk + P 24 wk (n = 111) PROVE IIPROVE IIISPRINT-1

Impact of RBV on Virologic Breakthrough Role of Viral Subtype Patients with confirmed virologic breakthrough (%) T12/PR T24/P24 (no RBV) T24/PR48 Genotype 1a Genotype 1b 2 PR48 (control) McHutchison JG, et al. Hepatology. 2009;50:334A-335A. (PROVE III)

Summary Patients that did not receive RBV in the PROVE trials and those with low dose RBV in the SPRINT-1 trial had – Increased viral breakthrough – Higher relapse rates – Lower SVR Standard dose RBV is required to optimize response to first generation PIs

Balapiravir (RG1626): RBV provides significant antiviral activity with IFN + Nuc Treatment ArmMean Reduction in HCV RNA Level from Baseline log 10 IU/mL Week 1Week 2Week 3Week 4 PEG-IFN + RG PEG-IFN + RG RBV PEG-IFN + RBV Nelson DR et al. Ann Hepatol 2012; 11(1):15-31

Role of Ribavirin Interferon-free Regimens

Day Median HCV RNA (IU/ml) Log GS-9256: protease inhibitor GS-9190: polymerase inhibitor GS GS-9190 (n = 15) GS GS RBV (n = 13) GS GS PEG IFN/RBV (n = 3) Breakthrough Ribavirin Reduces Viral Breakthrough In Protease + Polymerase Combination Zeuzem S, et al. Hepatology. 2010;52:Abstract LB-1.

ZENITH: VX Telaprevir ± PegIFN/ RBV in Genotype 1 Treatment-Naive Pts VX-222, NS5B nonnucleoside, polymerase inhibitor 2-drug arms terminated due high rates (>25%) of on-treatment breakthrough – 12 vBT (11 G1a and 1G1b) – new arm added: VX mg QD + telaprevir 1125 mg BID + RBV. * † PegIFN 180 µg/wk + weight-based RBV mg/day. Treatment-naive patients with chronic genotype 1 HCV infection* (N = 106) VX mg BID + Telaprevir 1125 mg BID (n = 29) VX mg BID + Telaprevir 1125 mg BID + PR † (n = 29) VX mg BID + Telaprevir 1125 mg BID + PR † (n = 30) Wk 12 VX mg BID + Telaprevir 1125 mg BID (n = 18) Wk 36 ‡ Wk 24 Nelson DR, et al. AASLD Abstract LB-14. PR for 12 wks if HCV RNA detectable at Wks 2 or 8 † Stop tx if HCV RNA undetectable at Wks 2 and 8 †

HCV Gen 1b Can Be Cured Without IFN or RBV BMS (NS5A) + BMS (NS3) 1. Lok A, et al. EASL Abstract Chayama K, et al. AASLD Abstract LB SVR24 (%) † N/A US Study [1] AASLD 2011: Japan Study (N = 10) [2] 9/10 n/N = 4/11 9/10 BMS mg QD + BMS mg BID + PEG-IFN/RBV A n=11 B n=10 BMS mg QD + BMS mg BID BMS mg QD + BMS mg BID Expansion A1 n=10 (GT-1b) weeks 024

8 PSI mg + PegIFN/RBV Week PSI mg + RBV 12 PSI + R 12 weeks n=10 PSI + PR 12 weeks n=10 4 PSI mg + RBV PSI mg + PegIFN/RBV PSI + PR 8 weeks n=10 PSI + PR 4 weeks n=10 PSI mg + RBV 15 ELECTRON PSI RBV (GT-2/3) Gane EJ, et al. AASLD Abstract 34 PSI mg PSI 12 weeks n=10

PSI-7977 ELECTRON What is the role of Ribavirin? Assay LLOD 15 IU/mL PSI-7977/RBV Combined IFN Arms Time (Days) Mean HCV RNA (Log 10 IU/mL) PSI-7977 Monotherapy

PSI RBV (GT-2/3) Ribivirin Prevents relapse Gane EJ, et al. AASLD Abstract

ELECTRON: Anemia RBV Impact on Hemoglobin with IFN-free PSI-7977/RBV PSI RBV

Alisporivir 600 mg BID + RBV Alisporivir 600 mg BID + PegIFN Week Alisporivir 800 mg QD + RBV* 24 ALV1000 n=83 ALV-P n=39 1 Alisporivir 600 mg BID Alisporivir 600 mg BID + RBV ALV800R n=94 ALV600R n=84 Alisporivir 600 mg QD + RBV* 19 Alisporivir (GT-2/3) Pawlotsky JM, et al. AASLD Abstract LB-11 PegIFN/RBV PR n=40 VITAL-1: phase IIb trial of alisporivir in treatment-naïve HCV GT-2 or GT-3 patients Alisporivir 1000 mg QD* Alisporivir 600 mg QD + PegIFN* *Patients with HCV RNA ≥25 IU/mL at Week 4 received alisporivir 600 mg QD + PegIFN/RBV from Week 6 until Week 24

20 Alisporivir in Genotyope 2/3 Pawlotsky JM, et al. AASLD Abstract LB-11

Conclusions The question of the role of RBV remains as real today as it was two decades ago! Critical role for RBV in combination with DAAs for both IFN- containing and IFN-sparing regimens – Leads to higher SVR Additive antiviral activity – Accelerates second slope of viral decline Prevents relapse and viral breakthrough RBV-free regimens more likely with potent and high-genetic barrier regimens and subtype (1b >1a)