Protease Inhibitors in Chronic Hepatitis C:
An Update
Chapter 6 – Investigational Anti-HCV Drugs Beyond
Boceprevir and Telaprevir
Edited by
Morris Sherman MD BCh PhD FRCP(C)
Associate Professor of Medicine
University of Toronto
November 2012
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
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
Pegylated Interferon Lambda
 IFN- (a type III interferon) receptors are expressed
in hepatocytes but in fewer other cells than IFN-a
(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. pegIFNa-2a + RBV with less toxicity.1
1. Muir A et al. AASLD 2010. Abstract 821
EMERGE: PegIFN-λ/RBV vs. PegIFNa-2a/RBV
Wk 24: GT 2 or 3
Wk 48: GT 1 or 4
PegIFNa-2a 180 μg/wk + RBV
(n=133)
Treatment naïve patients
with genotype 1-4 HCV
infection (n=526)
PegIFN- 120 μg/wk + RBV
(n=128)
PegIFN- 180 μg/wk + RBV
(n=131)
PegIFN- 240 μg/wk + RBV
(n=134)
Zeuzem S et al. EASL 2011. Abstract 1360
EMERGE: PegIFN-/RBV vs. PegIFNa-2a/RBV:
Preliminary Results to Week 12
PegIFNa-2a
Parameter (%)
PegIFN-
180 μg
120 μg
180 μg
240 μg
GT1/4 RVR
5.8
6.0
14.7*
16.5*
GT1/4 cEVR
38
55*
56*
56*
GT 2/3 RVR
31
43
76*
67*
GT 2/3 cEVR
86
90
97
83
Myalgia
30
11
6.1
9.0
Fever
29
7
7
6
Hb < 10 g/dL
44
21
15
13
ANC < 750
15
0
0.8
0
PLT < 25
1.5
0
0
0
Conjugated bilirubin
2.3
5.5
8.5
19.7
* p<0.05 compared with PegIFNa-2a
Zeuzem S et al. EASL 2011. Abstract 1360
EMERGE: PegIFN-/RBV vs. PegIFNa-2a/RBV:
Efficacy and Safety in Genotypes 2 & 3

SVR rates comparable in pegIFN arm vs. pegIFNa-2a
100
SVR24 (%)
Lambda
180 µg
(N = 29)
Alfa
180 µg
(N = 30)
6.9
44.8
RBV dose reduction
(Hb associated)
0
23.3
Neutrophils < 750/mm3
0
27.6
Platelets < 100,000/mm3
0
24.1
PegIFN dose reduction
(hematologic reason)
0
23.3
6.9
13.3
75.9
65.5
60.0
53.3
40
20
0
Fewer hematologic AEs and
ALT/AST elevations with pegIFN-
Adverse Event, %
80
60

N = 30
29
29
30
Alfa Lambda Lambda Lambda
180 µg 120 µg 180 µg 240 µg
Hb < 10 g/dL or
∆ > 3.4 g/dL
ALT/AST > 5 to 10 x ULN

PegIFN- 180 μg dosage chosen
for phase III trials
Zeuzem S et al. EASL 2012. Abstract 10
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
C
E1
E2
p7 NS2
NS3
4A
Polyprotein
NS4B
NS5A
Polyprotein processing
1
C
Core
E1
E2
Envelope
Glycoproteins
NS5B
p7 NS2
Protease
2
NS3
NS4A
Serine Helicase Serine
Protease
Protease
Cofactor
NS4B
NS5A
RNA
binding
NS5A
inhibitors
NS3-4A
protease
inhibitors
2
3
NS5B
RNA-dependent
RNA polymerase
NS5B
polymerase
inhibitors
1
Nucleoside analogs
Non-nucleoside analogs
3
4
Adapted from Asselah T et al. Liver International 2011; 31 Suppl 1:68-77
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.
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
HCV NS3/NS4A Protease Inhibitors (3)
 Two NS3 PIs (danoprevir1 and ABT-4502) 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
HCV NS5A Inhibitors
 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 system1. 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 date2.
1. Gao M et al. Nature 2010; 465:96-100
2. Pol S et al. Lancet Infect Dis 2012; 12(9):671-7
Antiviral Activity of Daclatasvir in Combination with
PegIFNa2a + RBV in Treatment of Naïve Patients
with Chronic HCV Genotype 1 Infection
Day 1
Week 48
Placebo +
PegIFNa-2a 180 µg/wk + RBV 1000/1200 mg/d
Treatment
naïve HCV
GT1 patients
n=48
Week 72
SVR 24
Daclatasvir 3 mg QD +
PegIFNa-2a 180 µg/wk + RBV 1000/1200 mg/d
Daclatasvir 10 mg QD +
PegIFNa-2a 180 µg/wk + RBV 1000/1200 mg/d
Daclatasvir 60 mg QD +
PegIFNa-2a 180 µg/wk + RBV 1000/1200 mg/d
Pol S et al. Lancet Infect Dis 2012; 12(9):671-7
Daclatasvir (DCV) with PegIFNa-2a + RBV:
Virologic Response at Weeks 4, 12 & SVR (ITT)
PR
Percent HCV RNA negative
(<10 IU/mL by Roche TaqMan)
100
PR + DCV 3 mg
PR + DCV 10 mg
PR + DCV 60 mg
92
83
83
83
83
83
80
58
60
42
40
42
42
25
20
8
0
RVR
cEVR
SVR (24)
12 patients per treatment arm; the 60 mg QD dose was selected for phase 3
Pol S et al. Lancet Infect Dis 2012; 12(9):671-7
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
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
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.
IFN Free SVR: The Very First Report (Daclatasvir
+ Asunaprevir in GT1 Prior Null Responders)
Daclatasvir+asunaprevir
Follow-up
HCV RNA (log10 IU/mL)
7
6
5
4
3
2
LLOQ
LLOD
1
0 1 2 3 4 6 8 10 12 16 20 24
Week
 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
Lok AS et al. EASL 2011; NEJM 2012;366:216-24
Dual Oral Therapy with Daclatasvir and
Asunaprevir x 24 Weeks for HCV GT1b
 Study conducted in Japan
 All had genotype 1b
 Treated with asunaprevir (NS3 PI) and daclatasvir
(NS5A inhibitor) x 24 weeks
Virologic Response (%)
Prior Null
Responders
(n=21)
[6 IL-28B CC]
IFN
Ineligible/Intolerant
(n=22)
[16 IL-28B CC]
Week 4 RVR
52
86
Week 12 cEVR
91
91
EOTR
91
86
SVR24
91
64
Suzuki F, et al. EASL 2012. Abstract 14
PILOT: NS3 PI + NN + RBV:
Virologic Responses
HCV RNA Negative (%)
 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
100
100
100
91
91
82
80
60
40
20
n/N
11/11
11/11
10/11
10/11
9/11
Wk 4
(RVR)
Wk 12
(EOT)
SVR12
SVR24
SVR36
0
Lawitz E, et al. EASL 2012. Abstract 13
CO-PILOT: NS3 PI + NN + RBV:
Virologic Responses
HCV RNA negative (%)
 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)
100
90
90
95
95
93
79
80
RVR
eRVR
SVR4
SVR12
93
79
77
59
60
47
47
40
20
0
ABT-450/r 250/100 mg QD
+ ABT-333 + RBV
Treatment naive
(n = 19; 17 G1a, 2 G1b)
* 11 partial responders, 6 null responders
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)
Poordad F et al. EASL 2012. Abstract 1399
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

100
80
SVR12 (%)
All (n = 64)
GT1a (n = 43)
GT1b (n = 21)
100
71
60
76
80
60
50
44
41
40
40
27
26
20
n/N =
0
32
25
20
26/64 11/43 15/21
Overall
n/N =
0
6/19 4/15
CC
2/4
20/45 7/28 13/17
IL28B Genotype
Non-CC
Gane E et al. EASL 2012. Abstract 1412
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
SVR12 (%)
100
80
60
59
61
68
56
39
40
20
n/N
0
BI 207127
Dosing
48/81
49/80
43/77
53/78
18/46
TID
16 wks
+ RBV
TID
28 wks
+ RBV
TID
40 wks
+ RBV
BID
28 wks
+ RBV
TID
28 wks
(no RBV)
Zeuzem S et al. EASL 2012. Abstract 101
SOUND-C2 BID Dosing Arm: Higher SVR12 in
Patients With GT1b or GT1a-IL28B CC
SVR According to IL28B and HCV Subtype:
BID 28 Wks + RBV (ITT)
100
82
75
80
SVR12 (%)
84
60
40
32
20
n/N =
0
7/22
6/8
31/37
9/11
1a
non-CC
1a
CC
1b
non-CC
1b
CC
HCV Subtype and IL28B Genotype
 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
Sofosbuvir (GS-7977)







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
Gane E et al. EASL 2012. Abstract 1113
Sofosbuvir + RBV x 12 Weeks:
Results in GT1 Treatment Naïve Patients
 In ELECTRON, 25/25 achieved EOT; 22/25 (88%)
achieved SVR4 and 3/25 (12%) relapsed1
 In QUANTUM, 17/17 achieved EOT; 10/17 (59%)
achieved SVR4, and 7/10 (41%) relapsed2
 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
1. Gane E et al. EASL 2012. Abstract 1113
2. Gilead Press Release, Apr 19, 2012
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.
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.
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.