SPRINT-2/RESPOND-2Boceprevir Plus Standard of Care Phase 3 Clinical Trials

Analysis of Resistance Associated Variants by HCV Genotype 1 subtypes 1a and 1b

Background► Nearly 170 million people worldwide are chronically infected with

Hepatitis C virus (HCV)– HCV genotype 1 is the most common and least responsive to

peginterferon alfa and ribavirin with geographic differences in HCV genotype 1 subtypes:

• Genotype 1a is predominant in Northern Europe and North America• Genotype 1b is predominant in Southern and Eastern Europe and

Japan– Leading indication for liver transplantation in Europe and United

States and is major etiologic factor in hepatocellular carcinoma

► Boceprevir - binds to the active site of the HCV NS3 protease– VictrelisTM (Boceprevir) approved by FDA for treatment use in

combination with peginterferon alfa and ribavirin in adult patients (≥18 years of age) with compensated liver disease, including cirrhosis, who are previously untreated or who have failed previous interferon and ribavirin therapy.

Objectives

► To compare the rate of sustained virologic response (SVR) of Boceprevir (BOC) dosed in combination with Peg-interferon alfa-2b (P) plus ribavirin (R) standard of care therapy in patients with Genotype 1a (G1a) and Genotype 1b (G1b) in the SPRINT-2 and RESPOND-2 clinical trials.

► To compare the frequency of Resistance Associated amino acid Variants (RAVs) between G1a and G1b viruses among non-SVR patients enrolled in SPRINT-2 and RESPOND-2

SPRINT-2/RESPOND-2 Phase 3 Trials► SPRINT-2 - 1,097 previously untreated patients (two cohorts enrolled and analyzed separately)

• Cohort 1: 938 (86%) non-Black patients• Cohort 2: 159 (14%) Black patients

► RESPOND-2– 403 prior treatment failures to P/R (patients failing to attain sustained

virologic response after an adequate course of therapy)

► Patient characteristics common to both studies– Patients mono-infected with chronic hepatitis C genotype 1– Co-infection with HIV or HBV excluded– Adult (≥18 years) patients– Compensated liver disease with all degrees of fibrosis– Studies conducted primarily in North America and Western Europe

– Double-blind for BOC – 3 treatment arms (all patients received a 4 week lead-in of

P/R prior to having BOC or placebo added to their regimen)• Arm 1: PR48 (Control)

– 4 weeks P/R then 44 weeks P/R + BOC placebo• Arm 2: BOC RGT

– 4 weeks P/R then P/R + BOC using response guided therapy (RGT)• Arm 3: BOC/PR48

– 4 weeks P/R then 44 weeks P/R + BOC– Primary endpoint: SVR in each experimental arm compared

to control arm• COBAS TaqMan 2.0 (Roche) HCV Test• Limit of Detection (LOD): 9.3 IU/ml• Limit of Quantitation: 25 IU/ml• All decisions based on LOD

SPRINT-2/RESPOND-2 Phase 3 Trials

Methods► Plasma samples were collected for resistance testing from

patients at baseline and at or near the time of virologic failure in patients that did not achieve SVR.

► Viral genotype was determined at screening using the TruGene assay. Subsequently, genotyping was determined by a combination of NS5b sequencing and/or inferred from positive amplification using subtype-specific primers (Virco BVM, Belgium)

► Population sequencing of the NS3 region was performed by Virco.

► Sequences from G1a and G1b viruses were aligned to the H77S and Con 1 reference strains, respectively. Major RAVs identified based on changes at specified loci compared with reference strain sequences.

TrugeneGenotype Assay

Genotype 1a Genotype 1 orGenotype 1b

NS3/4a Sequence Assay

Confirm Subtypeby NS5B Sequence

G1aSequence

Failed

Method 1

Method 2

Phylogenetic Analysis Method 3

HCV Genotype 1 Subtype Analysis

● Many patients genotyped as 1a using the Trugene assay were inconsistent with methods 2 and 3 (low concordance)● High concordance was observed between method 2 (used for final data analysis) and phylogenetic analysis of NS3/4a sequences

Patients Achieving SVR by HCV Genotypein SPRINT-2 and RESPOND-2

● There was a consistent but small numerical advantage for patients Infected with G1b compared to G1a to achieve SVR in both Boceprevir arms of each study.

SPRINT-2(Treatment Naive)

PR only BOC-RGT BOC-PR480

20

40

60

80 G1aG1b

Treatment Arm

35%41%

62/177 51/126 106/179 89/134 147/237 85/117

59%66% 62%

73%

% o

f Pat

ient

s Ac

hiev

ing

SVR

RESPOND-2(Previous PR non-responders)

PR only BOC-RGT BOC-PR48

0

20

40

60

80 G1aG1b

Treatment Arm

24%18%

53%

67% 64%71%

11/46 6/34 50/94 44/66 61/96 43/61%

of P

atie

nts

Achi

evin

g SV

R

Detection of Resistance Associated Variants (RAVs) in Boceprevir Treated patients(SPRINT-2 and RESPOND-2)

●There was a consistently higher % of patients with RAVs detected in patientsinfected with HCV G1a compared to G1b in both BOC arms of each trial.

RAVs (% of all BOC treated patients)

SPRINT 2 RESPOND 20

20

40

60

80G1aG1b

87/468 24/232 31/188 14/127

19%10%

16%11%

% P

atie

nts

with

RAV

s D

etec

ted

RAVs (% of all non-SVR Subjects treated with BOC)

SPRINT 2 RESPOND 20

20

40

60

80 G1aG1b

58%

48% 48%41%

87/151 24/50 31/65 13/41

% o

f Pat

ient

s w

ith R

AVs

Det

ecte

d

Frequency of RAVs in Non-SVR Patients by Genotype 1 subtype

9743

32

15

117

38

0

50

100

150

200

250

300

Genotype 1a Genotype 1b

Pat

ient

s, n

Patients with No Sequence DataPatients with RAVs DetectedPatients with no RAVs Detected

n=246

n=96

47%†

55%†

(SPRINT-2 and RESPOND-2)

9743

32

15

117

38

0

50

100

150

200

250

300

Genotype 1a Genotype 1b

Pat

ient

s, n

Patients with No Sequence DataPatients with RAVs DetectedPatients with no RAVs Detected

n=246

n=96

47%†

55%†

(SPRINT-2 and RESPOND-2)

Patients infected with HCV Genotype 1b had lower % RAVs detected compared to Genotype 1a Infected patients

† Expressed as a percentage of patients with sequence data available.RAVs=Resistance Associated Amino Acid Variants

3

61

60 0

19

3 1

68

8 5 40

70 1 1 0 03 3

42

3 3

37

24

0 3 0

26

3 5 5

32

0 0 3 5

0

10

20

30

40

50

60

70

80

90

100

Varia

nts,

%

G1aG1b

Frequency Distribution of Boceprevir RAVs Detected Post Baseline Among Boceprevir Treated patients

(SPRINT-2 and RESPOND-2)

● V36M and R155K were the predominant (>25%) RAVs in HCV G1a● T54A/S, A156S and V170A were the predominant RAVs (>25%) in HCV G1b

RAV Genotype WT Codon RAV Codon # changes

V36M G1aG1b

GTG GTT/C

ATGATG

12

R155K G1aG1b

AGGCGG

AAGAAG

12

T54A G1aG1b

ACTACT

GCTGCT

11

T54S G1aG1b

ACTACT

TCTTCT

11

A156S G1aG1b

GCCGCC/T

TCCTCC or TCT

11

V/I170A G1aG1b

ATCG/ATA/G

GCCGCA/G

21

Genetic Variation Between Genotype 1a and 1b Partially Explains Different RAV Frequencies

►V36M, R155K in G1b and V170A in G1a require 2 nucleotide changes and likely accounts for the different frequency observed between HCV G1a and G1b

RAVs Detected in a higher % of Non-SVR Patients with a poor Interferon Response at TW4

8 Patients missing TW4 viral load data and 42 with no sequence data are not included.RAV=resistance associated amino acid variant; SVR=sustained virologic response; TW=treatment week.

8752

39 115

020406080

100120140160180

Interferon Responsive Poorly Interferon Responsive

Pat

ient

s, n

Patients With No RAVs Detected Patients With RAVs Detected

31% 69%

126

167

≥1 log ↓ in viral load at TW4 <1 log ↓ in viral load at TW4

8752

39 115

020406080

100120140160180

Interferon Responsive Poorly Interferon Responsive

Pat

ient

s, n

Patients With No RAVs Detected Patients With RAVs Detected

31% 69%

126

167

≥1 log ↓ in viral load at TW4 <1 log ↓ in viral load at TW4

Frequency and Distribution of RAVs Detected at Baseline vs. Post-Baseline RAVs Associated With Virologic Failure

(Boceprevir Arm of SPRINT-2 and RESPOND-2)

All data based on population sequencing.RAVs=resistance associated amino acid variants.

Baseline RAVs Post-Baseline RAVs

8072

3623

1613

1210

96

422

1111110000

0 20 40 60 80

R155KV36MT54ST54A

A156SV55A

V170AV158I

R155TA156TV36A

A156VM175LT54CT54GI170FI170T

V170TV55I

V170MV36I

V36LQ41H

Patients, n

12

1810

22000000100000

1522

144

0 20 40 60 80

R155KV36MT54ST54A

A156SV55A

V170AV158I

R155TA156TV36A

A156VM175LT54CT54GI170FI170T

V170TV55I

V170MV36I

V36LQ41H

Patients, n

Not associated with Viral Failure

Associated with Viral Failure

0%778%3643V36M, R155K, T54S/A and V55A50%680%1521Other Baseline RAVs23%1376%5164Patients with Baseline RAVs34%25479%648902Patients without Baseline RAVs

SVR(%)

Patientsn

SVR(%)

PatientnTotal†

Poor Interferon Responders§

Interferon Responders‡

0%778%3643V36M, R155K, T54S/A and V55A50%680%1521Other Baseline RAVs23%1376%5164Patients with Baseline RAVs34%25479%648902Patients without Baseline RAVs

SVR(%)

Patientsn

SVR(%)

PatientnTotal†

Poor Interferon Responders§

Interferon Responders‡

(SPRINT-2 and RESPOND-2)

SVR Rates By Treatment Week 4 Response in Patients With or Without Baseline RAVs

†Total with Week 4 vial load available (treatment week 4 data not available for 12 patients without baseline RAVs and 2 with baseline RAVs). ‡Patients with ≥1 log10 decrease in viral load at treatment week 4.§ Patients with <1 log10 decrease in viral load at treatment week 4.SVR=sustained virologic response; RAVs=resistance associated amino acid variants.

SummaryBoceprevir, in combination with P/R significantly improved

SVR rates compared with P/R alone in both treatment naïve and previously treated patients

SVR rates among patients with G1b virus were consistently higher compared with G1a patients in both SPRINT-2 and RESPOND-2 phase 3 trials

Detection of resistance variants was more common among G1a vs G1b viruses in both pivotal trials when analyzed by all boceprevir treated and subset not achieving SVR

►predominant RAVs for G1a : V36M and R155K

►predominant RAVs for G1b : T54A/S, A156S, V170A

Conclusions

► Genetic variation between G1a and G1b viruses likely contributes to the higher rate of SVR and lower rate of major RAV detection (in non-SVR patients) in HCV G1b patients treated with Boceprevir combination therapy

► non-SVR patients with a good Interferon response had fewer RAVs detected

► Majority of poorly interferon responsive non-SVR patients had RAVs detected at failure primarily due to the fact most patients failed during the BOC dosing period