1. Christoph Sarrazin J. W. Goethe-University Hospital Frankfurt am Main, Germany Resistance is important? No 5 th Paris Hepatitis Conference Paris, 31.01.2012

2. Hepatitis C virus is an RNA virus

3. Selected resistant variants are not archived VX-950 Dosing Period Median Log HCV RNA Post-Dosing 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 IC 50 fold change WT V36 M/A/L R155 K/T/S/M T54A36/155 A156 V/T 36/156 WT 36 155 54 36/155 WT 156 36 155 54 36/155 WT 36 155 WT Long-term follow-up EOD 14 days Baseline Follow-Up 7/10 days post-dosing Long-term follow-up 3-7 months post-dosing 1 3.5 6.8 12 46 466 781 Sarrazin et al. Gastroenterology 2007

4. Selected resistant variants are not archived during long-term follow-up Patients (n) 53% 20% Population based sequencing Boceprevir (Phase 3) Telaprevir (Phase 2/3) (median FU 29 months) Overall 36 54155 156 168 36+155 0 20 40 60 80 100 49/60 107/12620/2174/81 11/11 69/82n/N = 91 84 82 85 Percent of patients with no detectable variants 95 100 0 0/1 Sherman KE, et al. Hepatology 2011;54 (Suppl. S1): Abstract 248 Barnard RJO, et al. Hepatology 2011;54 (Suppl. S1): Abstract 164

5. Resistant variants at long-term FU are rarely observed: clonal / deep sequencing [4.5 years] V36A V36M T54A T54S Patient # Susser et al., J Clin Virol 2011 Sarrazin et al., AASLD 2011 Deep sequencing (Illumina) 5.7y after Telaprevir (Phase 1)

6. Re-Treatment of patients is not commonly associated with treatment failure 10 8 10 7 10 6 10 5 10 4 10 3 10 2 10 1 10 0 Baseline 1 2 4 6 8 Time (weeks) 1 Patient had a confirmed viral breakthrough at Week 8 (V36M/V + R155K/R) Genotype 1a Genotype 1b Sarrazin et al., AASLD 2011

7. Re-Exposure of patients is not commonly associated with re-selection of same variants Vermehren et al., J Viral Hepatitis 2012 #1, GT 1a #2, GT 1a #3, GT 1b #4, GT 1b

8. Theoretically all possible single and double variants exist - but… Rong L, et al, Sci Transl Med 2010;2:30ra32; Neumann AU, et al. Science 1998;282:103–7 Domingo E, et al. Viral Hepatitis Rev 1996;2:247–61; Cuevas JM, et al. J Virol 2009;83:5760–4 Number of nucleotide change Probability of generation after one round of replication Number of virions with nucleotide change(s) produced per day Number of all possible nucleotide mutants Fraction of all possible mutants created per day 091%9.1 x 10 11 18.7%8.7 x 10 10 2.9 x 10 4 1 20.4%4.2 x 10 9 4.1 x 10 8 1 30.001%1.3 x 10 8 4.0 x 10 12 3.4 x 10 -5 Hepatitis C virus: ~9600 nucleotides Error rate during replication: ~10 -4 – 10 -5 per copied nucleotide Viral turnover:~10 12 virions produced every day Not all variants survive  Dead mutations (variants that can not replicate)  Immune sensitive mutations (variants that are eliminated by the immune system)

9. Presence of resistant variants at baseline is rare (TVR/BOC) and at low frequencies has no impact on SVR  Study 1 (n=570) 0.9% V36M, 0.7% R155K, 0.2% V170A, 0.2% R109K  Study 2 (n=507) 0.3–2.2% dominant PI resistant mutations within NS3 protease  Study 3 (n=662) 1.8% T54S, 0.6% R155K, 0.3% V36M  Study 4 (n=595) 4 % dominant PI resistant mutations within NS3 protease Population based sequencing Deep sequencing* (454) Sub- type Peg- IFN RBVTVR Virologic Response V36 A/M T54 A/S R155 K/T/Q A156 S/T/V 1aSVR–11%–0.3% 1aSVR––0.1%0.5% 1aSVR––0.6%1.8% 1aSVR––0.6%– 1aRR––6.0%3.2% 1bSVR–––0.3% 1bSVR––0.2% *cut-off: 0.1% according to statistical test based on Poisson’s law; SVR: sustained virologic response; NR: non-responder; RR responder-relapser Bartels DJ, et al. J Infect Dis 2008;198:800–7 Kuntzen T, et al. Hepatology 2008;48:1769–78; Vierling JM, et al. Hepatology 2010;52(Suppl.):702A De Meyer S, et al. J Hepatol 2011;54(Suppl. 1):S475; Chevaliez S, et al. J Hepatol 2011;54(Suppl. 1):S30

10. Presence of resistant variants at baseline at high frequencies requires combination therapies C E1 E2 p7 2 35B 5A4B 3 capsid envelope metallo-/ cysteine-protease NTPase/ helicase NS3-protease cofactor RNA-dependent RNA-polymerase serine- protease 4A NS3/4A-protease- inhibitors polymerase- inhibitors NS5A inhibitors membrane anchor regulation of replication Cyclophilin inhibitors Interferon alfa Ribavirin

11. Barrier to resistance depend on number and probability of nucleotide exchanges One nucleotide exchange for subtype 1a versus two nucleotide exchanges for subtype 1b NS3 protease sequence 155 HCV-1aGIFRAAV HCV-1bGIFRAAV HCV-1a AGG → AAG(R155K) HCV-1b CGG → AAG(R155K) Kieffer et al., Hepatology 2007 Sarrazin et al., Gastroenterology 2010 Main first generation NS3 Protease-Inhibitor Resistance site (R155K) NS5B polymerase in favor of transitions (A ↔ G and C ↔ T) over tranversions (A/G ↔ C/T and C/T ↔ A/G NS3 protease sequence 155 HCV-1aGIFRAAV HCV-1bGIFRAAV Transition HCV-1a AGG → AAG(R155K) Tranversion HCV-1b CGG → AAG(R155K) Powdrill et al., PNAS 2011 NS3, NS5A and non-nuc resistance mutations typically require transitions while nuc resistance site requires transversion (S282T)

12. New Triple- / Quadruple-Therapies and all-oral DAA therapies are highly effective Treatment-naive non-cirrhotic genotype 2/3 patients, n=50 (Nuc PSI-7977 +/- PEG2a +/- R for a total duration of 12 weeks) RVR [%] EOT [%] SVR [%] PSI- 7977+PEG12+R 100 PSI- 7977+PEG8+R 100 PSI- 7977+PEG4+R 100 PSI-7977+R100 PSI-7977 mono100 60 Gane et al., AASLD 2011, #34 Null-responder genotype 1 patients, n=10 (NS5A Inh Daclatasvir + PI Asunaprevir with and without PEG2a + R for 24 weeks) Lok et al., NEJM 2012 Quadruple 90% SVR NS5A-Inh + PI 36% SVR [2/2, GT 1b]

13. Summary  HCV is an RNA virus - treatment induced eradication of virus is possible - resistant variants can not be archived  Frequency of resistant variants at baseline is - low for many DAA - has no importance for SVR at low levels  Barrier to resistance is high for certain subtypes / isolates, and in general for nucleoside analogues  Combination therapies are effective to avoid resistance - many DAAs / HTA without cross resistance in development - quadruple therapies shown to highly effective - proof of principle to achieve SVR with all oral treatment