1. Edited by Morris Sherman MD BCh PhD FRCP(C) Associate Professor of Medicine University of Toronto Protease Inhibitors in Chronic Hepatitis C: An Update Chapter 6 – Investigational Anti-HCV Drugs Beyond Boceprevir and Telaprevir November 2012

2. Investigational Anti-HCV Drugs Beyond Boceprevir and Telaprevir Stephen D. Shafran MD, FRCPC, FACP Professor, Division of Infectious Diseases Department of Medicine University of Alberta

3. Investigational Drugs for HCV with Activity in Humans  Direct-acting antivirals (DAAs)  Non-DAAs  Peginterferon lambda (IFN- )  Tarabivirin  Pro drug of ribavirin  Higher ratio of liver to RBC distribution than RBV  Less anemia than with RBV  Silibinin (milk thistle extract, IV formulation)  Cyclophilin inhibitors (eg. Alisporivir*) * Development on hold due to cases of pancreatitis

4. Pegylated Interferon Lambda  IFN- (a type III interferon) receptors are expressed in hepatocytes but in fewer other cells than IFN-  (a type I interferon).  In a phase-IIa trial in treatment-naïve patients, pegIFN- 120-180 μg weekly + RBV resulted in similar or higher virologic responses at weeks 4 and 12 vs. pegIFN  -2a + RBV with less toxicity. 1 1. Muir A et al. AASLD 2010. Abstract 821

5. EMERGE: PegIFN-λ/RBV vs. PegIFN  -2a/RBV PegIFN  -2a 180 μg/wk + RBV (n=133) PegIFN- 120 μg/wk + RBV (n=128) PegIFN- 180 μg/wk + RBV (n=131) PegIFN- 240 μg/wk + RBV (n=134) Treatment naïve patients with genotype 1-4 HCV infection (n=526) Wk 24: GT 2 or 3 Wk 48: GT 1 or 4 Zeuzem S et al. EASL 2011. Abstract 1360

6. EMERGE: PegIFN- /RBV vs. PegIFN  -2a/RBV: Preliminary Results to Week 12 Parameter (%) PegIFN  -2aPegIFN- 180 μg120 μg180 μg240 μg GT1/4 RVR5.86.014.7*16.5* GT1/4 cEVR3855*56* GT 2/3 RVR314376*67* GT 2/3 cEVR86909783 Myalgia30116.19.0 Fever29776 Hb < 10 g/dL44211513 ANC < 7501500.80 PLT < 251.5000 Conjugated bilirubin2.35.58.519.7 Zeuzem S et al. EASL 2011. Abstract 1360 * p<0.05 compared with PegIFN  -2a

7.  SVR rates comparable in pegIFN- arm vs. pegIFN  -2a  PegIFN- 180 μg dosage chosen for phase III trials EMERGE: PegIFN- /RBV vs. PegIFN  -2a/RBV: Efficacy and Safety in Genotypes 2 & 3  Fewer hematologic AEs and ALT/AST elevations with pegIFN- Zeuzem S et al. EASL 2012. Abstract 10 SVR24 (%) 0 40 60 80 100 65.5 20 75.9 60.0 53.3 N = 29 30 Lambda 120 µg Lambda 180 µg Lambda 240 µg Alfa 180 µg Adverse Event, % Lambda 180 µg (N = 29) Alfa 180 µg (N = 30) Hb 3.4 g/dL 6.944.8 RBV dose reduction (Hb associated) 023.3 Neutrophils < 750/mm 3 027.6 Platelets < 100,000/mm 3 024.1 PegIFN dose reduction (hematologic reason) 023.3 ALT/AST > 5 to 10 x ULN 6.913.3

8. Proteins encoded by the HCV genome: Three validated targets and four classes of DAAs 5’ UTR region 3’ UTR region 9.6 kb RNA Polyprotein Polyprotein processing CE1E2p7NS2NS34ANS4BNS5ANS5B CE1E2p7NS2NS3NS4ANS5ANS5B CoreEnvelope Glycoproteins ProteaseSerine Protease Helicase RNA binding RNA-dependent RNA polymerase NS4B Serine Protease Cofactor Adapted from Asselah T et al. Liver International 2011; 31 Suppl 1:68-77 NS5B polymerase inhibitors Nucleoside analogsNon-nucleoside analogs 3 34 NS5A inhibitors 2 2 NS3-4A protease inhibitors 1 1

9. HCV NS3/NS4A Protease Inhibitors (1)  Inhibit cleavage of viral polyprotein chain, essential to HCV replication.  Very active against genotype (GT) 1.  A single nucleotide mutation in the NS3 region (R155K) results in resistance in GT 1a, but two mutations are required for resistance in GT 1b.  Some have activity against non-1 genotypes, but very little clinical data exist.  “First generation” NS3 PIs (boceprevir and telaprevir) are linear ketoamides and are associated with anemia;  “Second generation” NS3 PIs are macrocyclic and are not associated with anemia.

10. HCV NS3/NS4A Protease Inhibitors (2)  The two most developed after BOC/TVR are simeprevir (TMC-435) 1 and faldaprevir (BI-201335) 2. Both are in fully enrolled phase 3 clinical trials vs. dual PegIFN + RBV controls; results are expected in early 2013.  Simeprevir and faldaprevir are dosed once daily (150 and 120 mg, respectively) and do not produce additive anemia beyond PegIFN + RBV.  Simeprevir is associated with some increase in bilirubin due to reversible inhibition of OATP1B1 and MRP2 transporters.  Faldaprevir inhibits glucuronyl transferase and can cause a Gilbert’s like syndrome (similar to the HIV protease inhibitor, atazanavir).  Faldaprevir is also associated with rash and photosensitivity. 1. Fried MW et al. AASLD 2010. Abstract LB-5 2. Sulkowski M et al. EASL 2011. Abstracts 60 and 66

11. HCV NS3/NS4A Protease Inhibitors (3)  Two NS3 PIs (danoprevir 1 and ABT-450 2 ) are being developed for administration with low dose ritonavir.  Ritonavir, an HIV protease inhibitor, is a potent inhibitor of CYP3A4; ritonavir increases exposure of drugs metabolized principally via CYP3A4.  Other NS3 PIs are under development, including asunaprevir (BMS-650032), MK-5172, GS-9451, sovaprevir (ACH-1625), whereas the development of several others has been terminated. 1. Rouzier R et al. EASL 2011. Abstract 62 2. Lawitz E et al. EASL 2011. Abstract 1220

12. HCV NS5A Inhibitors 1. Gao M et al. Nature 2010; 465:96-100 2. Pol S et al. Lancet Infect Dis 2012; 12(9):671-7  NS5A is a protein with no known enzymatic function, but a definite, yet poorly defined role in viral replication.  NS5A inhibitors are very potent and pangenotypic in the replicon system 1. They are significantly more active vs. genotype 1b than genotype 1a.  Daclatasvir, the most developed NS5A inhibitor, is given once daily, and is in phase 3 in treatment naïve patients with genotypes 1 and 4, and in phase 2 for genotypes 2 and 3, and for genotype 1 in the HIV co-infected.  NS5A inhibitors in phase 2 are ABT-267 and GS-5885  NS5A inhibitors have no “signature” toxicity to date 2.

13. Antiviral Activity of Daclatasvir in Combination with PegIFN  2a + RBV in Treatment of Naïve Patients with Chronic HCV Genotype 1 Infection Placebo + PegIFN  -2a 180 µg/wk + RBV 1000/1200 mg/d Daclatasvir 10 mg QD + PegIFN  -2a 180 µg/wk + RBV 1000/1200 mg/d Daclatasvir 60 mg QD + PegIFN  -2a 180 µg/wk + RBV 1000/1200 mg/d Treatment naïve HCV GT1 patients n=48 Pol S et al. Lancet Infect Dis 2012; 12(9):671-7 Daclatasvir 3 mg QD + PegIFN  -2a 180 µg/wk + RBV 1000/1200 mg/d Day 1Week 48 Week 72 SVR 24

14. Daclatasvir (DCV) with PegIFN  -2a + RBV: Virologic Response at Weeks 4, 12 & SVR (ITT) Percent HCV RNA negative (<10 IU/mL by Roche TaqMan) RVRcEVR PRPR + DCV 3 mgPR + DCV 10 mg SVR (24) PR + DCV 60 mg 0 20 40 60 80 100 8 42 25 42 58 83 92 Pol S et al. Lancet Infect Dis 2012; 12(9):671-7 12 patients per treatment arm; the 60 mg QD dose was selected for phase 3

15. HCV NS5B Polymerase Inhibitors  NS5B is a RNA-dependent RNA polymerase, responsible for viral RNA synthesis  The viral polymerase is the “classic” target for antiviral drugs (eg. DNA-dependent DNA polymerase in HSV and VZV or RNA-dependent DNA polymerase [reverse transcriptase] in HIV and HBV)  As with HIV RT inhibitors, there are two subtypes of NS5B inhibitors,  Nucleoside/nucleotide analogues  Act as RNA chain terminators  High barrier to resistance  Pan-genotypic  Non-nucleoside inhibitors  Least potent class of DAA  Low barrier to resistance

16. HCV NS5B Polymerase Inhibitors: Drugs with Antiviral Activity in Humans  Nucleoside/nucleotide analogues  Mericitabine (RG-7128)  Sofosbuvir (GS-7977/ PSI-7977)  VX-135 (ALS-2200)  Non-nucleoside inhibitors  Tegobuvir (GS-9190)  Setrobuvir (ANA-598)  ABT-333 (lead Abbott NNI)  ABT-072 (back-up Abbott NNI)  VX-222  BI-207127

17. IFN-Free, All Oral Regimens with SVR Data  As of October 2012, 5 pharmaceutical companies have presented pilot data demonstrating that SVR can be achieved in small numbers of patients.  The majority of IFN-free regimens to date continue to include ribavirin.  Only one study to date has included patients with cirrhosis (SOUND C-2).  The most common combination of agents in IFN-free regimens for genotype 1 has been a 3-drug combination of a NS3 PI, a NS5B non-nucleoside (NN) inhibitor and ribavirin.  For GT 2 & 3, IFN-free regimens demonstrating SVR are sofosbuvir with either RBV or daclatasvir.

18. IFN Free SVR: The Very First Report (Daclatasvir + Asunaprevir in GT1 Prior Null Responders) Lok AS et al. EASL 2011; NEJM 2012;366:216-24  SVR was achieved in 2/9 GT 1a and 2/2 GT 1b prior null responders to PR with 24 weeks of DCV + ASV (all enrolled patients were non-cirrhotic)  On therapy breakthrough was common in GT 1a 7 5 4 3 2 1 6 01234681012162024 PT4PT8 PT12PT24 PT36PT48 HCV RNA (log 10 IU/mL) Week LLOQ LLOD Follow-upDaclatasvir+asunaprevir

19. Dual Oral Therapy with Daclatasvir and Asunaprevir x 24 Weeks for HCV GT1b Virologic Response (%) Prior Null Responders (n=21) [6 IL-28B CC] IFN Ineligible/Intolerant (n=22) [16 IL-28B CC] Week 4 RVR5286 Week 12 cEVR91 EOTR9186 SVR249164 Suzuki F, et al. EASL 2012. Abstract 14  Study conducted in Japan  All had genotype 1b  Treated with asunaprevir (NS3 PI) and daclatasvir (NS5A inhibitor) x 24 weeks

20. PILOT: NS3 PI + NN + RBV: Virologic Responses  n = 11, HCV GT1, treatment-naïve, non-cirrhotic; 8 GT1a, 3 GT 1b  Only IL-28B CC patients were enrolled, so that they would have a high probability of salvage with PegIFN + RBV in the event that all-oral therapy failed  All were treated with ABT-450/r 150/100 mg QD + ABT-072 400 mg QD + RBV 1000/1200 mg/d Lawitz E, et al. EASL 2012. Abstract 13 Wk 4 (RVR) Wk 12 (EOT) SVR12 SVR24 HCV RNA Negative (%) 0 40 60 80 100 20 100 91 82 SVR36 11/11 10/11 9/11 n/N

21. CO-PILOT: NS3 PI + NN + RBV: Virologic Responses  Because of the favorable results in PILOT, CO-PILOT was open to all IL-28B genotypes and explored prior PR non-responders;  All had genotype 1 and were non-cirrhotic  In CO-PILOT, a different NS5B non-nucleoside inhibitor was used (ABT-333) than in PILOT (ABT-072) Poordad F et al. EASL 2012. Abstract 1399 HCV RNA negative (%) 0 40 60 80 100 20 ABT-450/r 250/100 mg QD + ABT-333 + RBV Treatment naive (n = 19; 17 G1a, 2 G1b) ABT-450/r 150/100 mg QD + ABT-333 + RBV Treatment naive (n = 14; 11 G1a, 3 G1b) ABT-450/r 150/100 mg QD + ABT-333 + RBV Prior PR Non-responders* (n = 17; 16 G1a; 1 G1b) RVR eRVR SVR4 SVR12 90 95 79 93 77 59 47 * 11 partial responders, 6 null responders

22. INFORM-SVR: NS3 PI + Nucleoside + RBV in GT1: SVR12 by HCV Subtype and IL28B Genotype  Data shown are patients treated with 24 weeks of mericitabine + danoprevir/r + ribavirin; all were treatment naïve and non-cirrhotic  SVR12 rates were encouraging in GT1b but disappointing in GT1a Gane E et al. EASL 2012. Abstract 1412 SVR12 (%) 0 40 60 80 100 20 Overall CCNon-CC IL28B Genotype n/N = 41 26 71 32 27 50 44 25 76 All (n = 64) GT1a (n = 43) GT1b (n = 21) 26/6411/4315/216/194/152/420/457/2813/17 0 40 60 80 100 20 n/N =

23. 68 SOUND-C2: NS3 PI + NN ± RBV: SVR12 by Study Arm  N=362; the largest IFN-free study to date  All had GT1 and were treatment naïve; 10% had cirrhosis  All received faldaprevir 120 mg QD + RBV 1000/1200 mg/d  Patients were randomized to 5 arms, 4 containing BI-207127, 600 mg TID (3 arms) or 600 mg BID (one arm) for 3 different durations  RBV-free arm was stopped prematurely due to high relapse rate Zeuzem S et al. EASL 2012. Abstract 101 SVR12 (%) 0 40 60 80 100 20 BID 28 wks + RBV TID 28 wks (no RBV) TID 40 wks + RBV TID 28 wks + RBV TID 16 wks + RBV 59 61 56 39 BI 207127 Dosing 48/81 49/80 43/7753/7818/46 n/N

24. SOUND-C2 BID Dosing Arm: Higher SVR12 in Patients With GT1b or GT1a-IL28B CC  Boehringer Ingelheim has decided to undertake additional studies of this 3-drug regimen only in patients with GT1b and those with GT1a who are IL-28B CC Zeuzem S et al. EASL 2012. Abstract 101 SVR12 (%) n/N = 32 75 84 82 1a non-CC 1a CC 1b non-CC 1b CC SVR According to IL28B and HCV Subtype: BID 28 Wks + RBV (ITT) 0 40 60 80 100 20 7/226/831/379/11 HCV Subtype and IL28B Genotype

25. Sofosbuvir (GS-7977) Gane E et al. EASL 2012. Abstract 1113  Nucleotide NS5B inhibitor  Once daily oral dosing with no food effect  No described toxicity to date  Pangenotypic  No virological breakthroughs reported to date  Studied in combination with RBV or daclatasvir or simeprevir*  In GT2 & 3, sofosbuvir + RBV x 12 weeks achieved SVR24 in 10/10 patients; sofosbuvir + RBV x 8 weeks achieved SVR12 in 10/10 patients (all non cirrhotic)  Two phase 3 RCTs are fully enrolled in GT2 & 3 (including cirrhotics); results expected EASL 2013  FISSION: Treatment naïve patients randomized to sofosbuvir + RBV x 12 weeks vs. PegIFN + RBV x 24 weeks  FUSION: Treatment failure patients randomized to 12 wk vs. 16 wk of sofosbuvir + RBV * No data have been presented on sofosbuvir + simeprevir

26. Sofosbuvir + RBV x 12 Weeks: Results in GT1 Treatment Naïve Patients 1. Gane E et al. EASL 2012. Abstract 1113 2. Gilead Press Release, Apr 19, 2012  In ELECTRON, 25/25 achieved EOT; 22/25 (88%) achieved SVR4 and 3/25 (12%) relapsed 1  In QUANTUM, 17/17 achieved EOT; 10/17 (59%) achieved SVR4, and 7/10 (41%) relapsed 2  Combined ELECTRON and QUANTUM SVR in GT1 naives is 32/42 (76%)  Only non-cirrhotic patients were enrolled in ELECTRON and QUANTUM  Future studies in GT1 will examine  Longer treatment durations of Sofosbuvir + RBV  The addition of a third antiviral drug

27. The Canadian Liver Foundation (CLF) was the first organization in the world devoted to providing support for research and education into the causes, diagnoses, prevention and treatment of all liver disease. Through its chapters across the country, the CLF strives to promote liver health, improve public awareness and understanding of liver disease, raise funds for research and provide support to individuals affected by liver disease. For more information visit www.liver.ca or call 1-800-563-5483.www.liver.ca This project made possible through the financial support of Merck Canada Inc. The views, information and opinions contained herein are those of the authors and do not necessarily reflect the views and opinions of Merck Canada Inc. The Canadian Liver Foundation gratefully acknowledges the participating health care professionals for their contributions to this project and for their commitment to the liver health of Canadians.