Summary of Industry Responses and Regulatory Perspective

1. Summary of Industry Responses and Regulatory Perspective William Tauber, M.D. Division of Antiviral Products Food and Drug Administration October 19, 2006

2. Presentation Outline • Introduction • Consensus Definitions • Summary of responses re: • Study Populations-Inclusions and Definitions • Selection of Controls • Study Endpoints Compensated liver disease • Study Endpoints Decompensated liver disease • Study Design Options • Long Term Follow-up • Concluding Remarks

3. Introduction • Chronic Hepatitis C is a global problem • est. 170M infected worldwide and 3.2M USA • Incidence infection USA decreasing but HCV related disease: cirrhosis, ESLD, HCC increasing • long latency, • lack of spontaneous resolution, • aging of infected population = liver related complications will increase in the next 10-20years • CHC already the most common reason for transplant

4. Introduction (cont.) • Current SOC treatment is interferon based • Duration 48 weeks for G1/4 , 24 weeks G2/3 • SVR endpoint measured 24 weeks after end of therapy • Expensive with safety issues • Effective for 30 to 80% based on genotype and patient characteristics • New treatment strategies and/or novel agents needed

5. Achillion Pharmaceuticals Bristol-Myers Squibb Coley Pharmaceutical Grp Hoffmann-La Roche Human Genome Sciences Idenix Pharmaceuticals National Institutes Health NIDDK, NIAID Peregrine Pharmaceuticals Schering-Plough SciClone Pharmaceuticals Vertex Pharmaceuticals Wyeth Pharmaceuticals XTL Biopharmaceuticals Respondents(IND Holders)

6. Consensus Definitions All CHC pts including compensated cirrhosis Evidence of ongoing liver damage and hepatitis C viral replication during at least 6 months of observation Chronic Hepatitis C (CHC) Compensated Liver Disease Decompensated Liver Disease Compensated cirrhosis Absence of clinical consequences of liver disease (ascites, variceal bleeding, encephalopathy) and preserved hepatic synthetic function (albumin ≥ 3.5g/dL, total bilirubin ≤1.5mg/dL and prothrombin time INR ≤ 1.5) Decompensated cirrhosis

7. Study Population:Initial Clinical Development Program • Stage of disease- Compensated/Decompensated • Treatment naïve or experienced • Genotype 1or 4 vs 2 or 3 • Co-infection with either HIV or HBV • Pre or post liver transplantation • Pediatrics • Racial or Ethnic Groups

8. Candidates: Initial Clinical Development Trials Preferred Populations Ideal Treatment-Naïve with early stage histologic changes, high baseline viral load and genotype 1 (largest group, homogeneous, current treatment response 40-50%) Greatest Need Treatment-Experienced, non-responder (fasted growing group, more advanced histology, more urgent need for effective treatment) Compensated liver disease to include: cirrhosis, no cofactors, adults, genotypes 1, 2, 3 and 4

9. Candidates-Initial Clinical Development Trials • Most favored inclusion of African Americans and Hispanics • Registrational trials • Also suggested investigator trials or phase 4 post-marketing due to historically difficult enrollment in these groups

10. Inclusion Candidates Post Approval Pediatric “post-approval”studies and access programs during phase 2-3development of promising agents CHC pts co-infected with HIV or HBV Historically difficult to enroll Decompensated cirrhosis or in the immediate post liver transplant period

11. Definition Non-Responder General agreement with the following components as inclusion criteria in clinical development studies of treatment experienced non- responder patients: Previously treated with 1 or more IFN-containing regimens that include PEG-IFN and RBV Failure to achieve a ≥ 2 log10 reduction in HCV RNA at Week 12, or HCV detectability at Week 24 or beyond while on therapy (confirmed by a repeat test) AND Compliance documented over the first 12 weeks of previous therapy to confirm receipt of at least 80% of the prescribed RBV and PEG-IFN dose

12. Non-Responder Populations • “Non-responders to prior interferon based therapy” can refer to a heterogeneous population. • patients with no significant response (true nonresponder) • patients with partial response (≥ 2 log10 reduction HCV RNA at Week 12 but detectable at Week 24 and beyond) • relapsers- undetectable during treatment but unable to maintain undetectable during follow-up • relapsers/rebounders- temporarily undetectableduring treatment

13. Selection of Controls • Treatment naïve compensated CHC patients • consensus most appropriate comparator control is parenteral pegylated interferon alfa and oral ribavirin for 24 or 48 weeks based on genotype • placebo or deferred administration could be acceptable if cross over to active treatment assured • an acceptable delay duration varied between 4 to 12 wks • no parenteral placebo was endorsed

14. Selection of Controls • For treatment-experienced compensated CHC pts • longer durations of placebo controls or Rx delay (up to 24 months) were acceptable. • For both populations novel drug monotherapy acceptable for short periods, typically 2 weeks but longer periods suggested by some IND holders • Few commented on patients with decompensated liver disease but one ventured placebo controlled or treatment delay might be possible

15. Summary of ResponsesEndpoints Compensated Liver Disease • Primary Endpoints: Viral Clearance Goal • Primary Endpoints: Viral Suppression Goal • Secondary Endpoints

16. Sustained Virologic Response (SVR) • Defined as: • HCV RNA undetectable (< 100 copies/mL) by RT-PCR after 24 weeks of untreated follow-up • Preferred endpoint for all patient populations, surrogate for viral clearance • Definition problematic with differing treatment durations leading to measurements at multiple timepoints leading to statistical chaos • Timing of SVR measurement more controversial • Some noted that 98% of relapses occur within 12 weeks after treatment discontinued and offered SVR 12 as alternative • SVR only currently validated for IFN treatment, some suggested SVR demonstration for novel drugs needed

17. Endpoints Compensated Liver Disease • Primary Endpoints: Viral Clearance Goal • Primary Endpoints: Viral Suppression Goal • Secondary Endpoints

18. Primary Endpoints Viral Clearance Goal • Treatment-Naïve • Consensus for Sustained Virologic Response (SVR) • Potential co-primary = Rapid Virologic Response (RVR4) defined as undetectable HCV RNA (<100 copies/mL) at 4 weeks of therapy • Treatment-Experience • SVR preferred where reasonably attainable • Early Virologic Response (EVR12) defined as > 2 log10 decrease in HCV RNA 12 weeks recommended as futility endpoint for INF based Rx • Novel Agents viral clearance may be slower

19. Endpoints Compensated Liver Disease • Primary Endpoints: Viral Clearance Goal • Primary Endpoints: Viral Suppression Goal • Secondary Endpoints

20. Primary Endpoints Viral Suppression Goal Hypothesis: Suppression will decrease development of ESLD, HCC • Non-Responder population with lack of response or intolerance to PEG-IFN/RBV • Histologic improvement- usually 2 HAI K/I • Biochemical Improvement- normalization of liver transaminases • Viral Suppression (similar to goals of HIV Rx) actual clinically meaningful levels not suggested; -RVR4 might be applicable in this situation

21. Endpoints Compensated Liver Disease • Primary Endpoints: Viral Clearance Goal • Primary Endpoints: Viral Suppression Goal • Secondary Endpoints

22. Secondary Endpoints • For both treatment-naïve and non-responders except as noted above, histologic and biochemical endpoints were considered appropriate secondary endpoints due to their lack of specificity and sensitivity

23. Endpoints Decompensated Liver Disease 1 • Few IND holders responded to this question • Without transplantation, 5 year survival 50% • Primary Goals (transplant avoidance) • Slowing progression, improving hepatic function, reversing complications, reduced transplant need • Secondary Goals (preparation for transplant) • Clearance of HCV RNA to prevent recurrence of HCV viremia post transplant (nearly universal) • Reduction of HCV RNA to reduce severity post transplant liver disease

24. Endpoints Decompensated Liver Disease 2 • Major concern regarding IFN safety with increased risk bone marrow toxicity and worsening liver function • SVR remains favored primary endpoint. • Up to 22% SVR prior to transplantation, virus-free post transplant • SVR post transplant, 36% with decreased fibrosis in one study • Other studies not as favorable

25. Endpoints Decompensated Liver Disease 3 • Scoring systems used to prioritize transplantation list include: • Child Turcotte Pugh (CTP) • Model for Endstage Liver Disease (MELD) • Consider improvements in CTP and MELD scores as endpoints. However, threshold values not established nor validated for this purpose • One suggested composite endpoint • Serum HCV RNA reduction of >1 Log10WITH • Histologic response of (2 points of Knodell HAI with no worsening fibrosis)

26. Study Design Options Monotherapy Use of a dose of PEG-INF lower than SOC and/or of shorter duration + investigational agent Use of two or more investigational agents Adding Investigational agent to SOC Ribavirin substitution

27. Study Design Options Monotherapy Use of a dose of PEG-INF lower than SOC and/or of shorter duration + investigational agent Use of two or more investigational agents Adding Investigational agentto SOC Ribavirin substitution

28. Study Design OptionsAdding Agent to SOC • General agreement: adding a third agent to PEG-IFN/RBV is the preferred clinical design for treatment naïve pts. • Other suggestions: • For the treatment experienced, use RVR4 and EVR12 to prevent extended monotherapy • If investigational agent is oral, an oral placebo could be used • Depending on efficacy/safety characteristics of novel agent, a) triple Rx maintained throughout treatment course b) administered for defined period followed by consolidation with SOC c) administered for defined period followed by off-treatment F/U

29. Study Design Options Monotherapy Use of a dose of PEG-INF lower than SOC and/or of shorter duration + investigational agent Use of two or more investigational agents Adding investigational agent to SOC Ribavirin substitution

30. Study Design OptionsUse of Non-SOC PEG-IFN/Novel Agent • Consensus decreased dosage and/or duration of PEG-IFN with acceptable or improved efficacy might be possible with co-administration of novel agents • However, pivotal studies should include SOC comparator arms with and without novel agent

31. Study Design Options Monotherapy Use of a dose of PEG-INF lower than SOC and/or of shorter duration + investigational agent Use of two or more investigational agents Adding investigational agent to SOC Ribavirin substitution

32. Study Design OptionsRibavirin Substitution • Ribavirin’s mechanism of improving interferon-alfa SVR rates for CHC is unknown • Many were reluctant to study a novel agent as substitution for RBV until activity as third agent to SOC is demonstrated • In the presence of such data, a novel agent could be combined with PEG-IFN vs SOC and might be approvable if non-inferior and comparable or better safety/tolerability • To test additive or synergistic effects novel agent, administration as monotherapy prior to PEG-IFN suggested up to 12 weeks (DAVP Concerned)

33. Study Design Options Monotherapy Use of a dose of PEG-INF lower than SOC and/or of shorter duration + investigational agent Use of two or more investigational agents Adding investigational agent to SOC Ribavirin substitution

34. Study Design OptionsUse of two or more Novel Agents 1 • Ideally, differing mechanisms of action • Prior to combination studies, a novel agent would need to demonstrate anti-HCV activity over specified period up to 14 days, longer if viral resistance issues satisfied • Drug-Drug interaction studies might be considered if metabolism profile of drugs suggests interaction potential • Novel investigational regimens with 2+ novel agents with complementary mechanisms considered important for difficult to treat CHC populations

35. Study Design OptionsUse of two or more Novel Agents 2 • Patient populations to benefit from use of two or more agents • SOC Non-Responders: • Multi-drug regimens compared with retreatment SOC or deferred treatment with novel regimen to establish placebo-like control period • A concurrent PEG-IFN/RBV treatment period with EVR12 should be incorporated to confirm non responder • Patients for whom IFN/RBV contraindicated such as decompensated liver disease or severe anemia • To minimize safety concerns, RVR4 could be used depending on viral kinetics of products

36. Study Design Options Monotherapy Use of a dose of PEG-INF lower than SOC and/or of shorter duration + investigational agent Use of two or more investigational agents Adding investigational agent to SOC Ribavirin substitution

37. Study Design OptionsMonotherapy • Agreement for limited monotherapy treatment periods in clinical trials • The major concern is high daily turnover of HCV RNA and low fidelity of the HCV replicase result in development of viral resistance with longer durations of monotherapy • No support expressed for more than short duration of interferon monotherapy except in special populations such as those with ESRD

38. Long-Term Follow-up Confidence with durability of SVR for INF based treatment SVR following non interferon based treatment needs validation with F/U HCV RNA, ALT x 3 years • No further follow-up • 5-10 Year follow-up For cirrhotics, transplant recipients, HIV/HCV coinfected and immune deficit patients, more frequent follow-up of HCV RNA after SVR suggested

39. Long-Term Follow-up For patients who fail to achieve SVR, and continuous treatment not elected Semi-annual follow-up to monitor the state of liver function was recommended For situations where viral suppression is the goal and histologic and or biochemical endpoints used Every 4-5 years to determine if study agent should be continued

40. Concluding RemarksStudy Populations • Inclusion Candidates Initial Approval: • Adult, compensated liver dz, including cirrhotics, minority participation, genotypes 1, 2, 3 and 4, no co-infections • Treatment naïve most homogeneous • Treatment experienced heterogeneous, fastest growing, greatest need • Inclusion Candidates Post Approval: • Pediatrics, decompensated/transplanted, co-infected, minority focused • Agency needs representative population to support labeling

41. Study Populations/Controls • The Non-Responder population: • Important challenge • Substantial opportunity for the development of novel drugs or new treatment regimens utilizing currently approved products • Issues: • Heterogeneity • Proposed inclusion criteria definition appeared acceptable but additional advice on increasing interpretability is sought • Controls: • SOC comparator recommended whenever possible • Placebo or deferred treatment possible with shorter durations for treatment naïve

42. Concluding Remarks-Endpoints • Consensus primary endpoint = SVR= problems: • SVR currently only validated for IFN treatment • Timing of endpoint measurement- • IND holders recommended set number of weeks after treatment stopped • Agency prefers standard comparable testing times • EVR12 and RVR4 (IFN Study Tools) • Histologic and Biochemical Endpoints • Clinically meaningful levels of viral suppression and changes CTP/MELD not validated

43. Concluding Remarks Study Design Options General agreements: • Adding third agent to SOC treatment naïve preferred • RVR4 and EVR12 could prevent prolonged monotherapy in treatment experienced • Ribavirin substitution-active novel agent • Two or more novel agents SOC non-response or contraindication, SOC comparator possible • Monotherapy limited time, special populations IFN

44. Conclusions Long Term Follow-Up • Confidence in SVR with IFN based Rx- range from no follow-up to 5-10years • SVR with novel agents unknown durability, recommend retesting to 3 years post Rx • Special populations more frequent follow-up • No SVR, no treatment, F/U twice per year • Long term suppression, Rx monitor every 4-5 years