1. Resistance to HCV direct-acting antivirals: What should we know?
Heidar Sharafi, MSc, PhDc
Middle East Liver Diseases (MELD) Center
E mail:

2. Approved HCV Direct-acting Antiviral (DAA) Agents
Core E1 E2 P7
NS2
NS3 4A
NS4B
NS5A
NS5B
5’UTR
3’UTR
Protease Inhibitors
Simeprevir (SMV)
Paritaprevir (PTV)
Grazoprevir (GZR)
NS5A Inhibitors
Ledipasvir (LDV)
Daclatasvir (DCV)
Ombitasvir (OMV)
Elbasvir (EBR)
Velpatasvir (VEL)
NS5B NUC Inhibitors
Sofosbuvir (SOF)
NS5B non-NUC Inhibitors
Dasabuvir (DSV)
Bertino G. World Journal of Hepatology. 2016;8(2):

3. Mechanism of Action Mechanism of action: Resistance:
Binding and blocking the active site of the protein (NS3, NS5A & NS5B)
Resistance:
Mutations close to active site reduce affinity to drug

4. HCV displays a high genetic diversity
Production of 1012 virions daily
~1 error per 10,000 bases for RNA polymerase
Within one patient HCV exists as a population of genetically distinct but closely related variants (quasispecies)
RAVs: Resistance-associated Variants

5. The Theory for Resistance to new DAAs
2-12 weeks after termination of treatment
Quasispecies with dominant wild-type virus and single resistant variants
After few days, wild-type virus is eliminated
At the end of treatment v
Treatment with DAAs
Baseline
Wild type
Medium resistance/more fit
High resistance/unfit
Resistance with increased fitness

6. Barriers to Genetic Resistance by DAAs Approved (GT1)
Protease Inhibitors
NS5A Inhibitors
NS5B NUC Inhibitors
NS5B non-NUC Inhibitors
DAAs in class
Simeprevir Paritaprevir
Grazoprevir
Ledipasvir Daclatasvir Ombitasvir Elbasvir
Sofosbuvir
Dasabuvir
Barrier to resistance
Low (1a < 1b)
High (1a = 1b)
Very Low (1a < 1b)
RAVs to one DAA are generally cross-resistant to other DAAs within a class, although this is not always the case
Bertino G. World Journal of Hepatology. 2016;8(2):

7. NS5A Resistance Overview
Baseline polymorphisms associated with resistance are relatively prevalent (15-30%)
Currently available NS5A inhibitors suffer from broad cross-resistance at key positions
Q30R, L31M/V, Y93H/N
75% of patients harbor RAVs after treatment failure with SOF/LDV
NS5A variants persist for prolonged periods
Selected NS5A RAVs impact re-treatment responses

8. Broad Cross-resistance with NS5A inhibitors
Fold-change in resistance
GT1a
GT1b
M28T
Q30R
L31M/V
Y93H/N
L31V
LDV
20x
>100x
>100x/ >1,000x
>1,000x/ >10,000x
>100x/--
OMV
>1000x
<3x
<10x
20x/50x
DCV
EBR
>10x
VEL
<3x/--

9. Baseline NS5A RAVs in DAA-naïve Patients
Genotype 1a
Genotype 1b
Baseline RAVs in GT1a (M28, Q30, L31 & Y93) have the largest clinical impact.
Y93H in GT1b; most common but little impact
Y93H in GT1b ~100-fold change while in GT1a ~10,000-fold shift
The subtype background has much to do with whether the RAV has a clinical impact.
Dietz J. PloS one. 2015;10(8):e

10. Treatment-Naïve: Baseline NS5A Resistance and SOF/LDV ~4% delta in SVR if RAV
Analysis of baseline samples (n=1904) in phase 2/3 SOF/LDV studies
93%
SVR12
92%
SVR12
97%
SVR12
NS5A
RAVs
95%
SVR12
16%
16%
84%
84%
No RAVs
96%
SVR12
98%
SVR12
Sarrazin C. AASLD. 2014;Abstract#1926.

11. Baseline NS5A Resistance and SOF/LDV
SVR12, %
Sarrazin C. AASLD. 2014;Abstract#1926.

12. Baseline NS5A Resistance and SOF/LDV
SVR12, %
Sarrazin C. AASLD. 2014;Abstract#1926.

13. Impact of Baseline NS5A RAVs in Patients with Cirrhosis Treated with SOF/LDV
Impact of subtype and fold-change
SVR12, %
SVR12, %
SVR12 combined: 98% no RAVs vs 89% RAVs level]
Sarrazin C. EASL. 2015;Abstract#P0773.

14. Impact of Baseline NS5A RAVs in Patients with Cirrhosis Treated with SOF/LDV
Impact of duration and RBV
SVR12, %
Sarrazin C. EASL. 2015;Abstract#P0773.

15. Consideration for NS5A Resistance Testing in DAA-Naïve Patients – G1a Only
SOF/LDV
Apparent role in treatment-naïve patients
8 weeks Rx
Cirrhosis
Could baseline testing be used to “optimize” therapy in TE patients, particularly those with cirrhosis?
24 weeks + RBV for all TE cirrhosis with baseline NS5A RAVs?
Overtreatment of many patients?

16. High Durability of Treatment Emergent NS5A RAVs
Patients with NS5A RAVs, %
Dvory-Sobol H. EASL. 2015;Abstract#77.

17. NS5A RAVs are Associated with Retreatment Failure-SOF/LDV for 24 Weeks (n=41)
SVR12, %
SVR12, %
Lawitz E. EASL. 2015;Abstract#O005.

18. SUMMARY
Additional data are needed, particularly in the setting of DAA failure, to define the role of resistance testing in deciding best therapy.
In case of HCV genotype 1 infection, the following are parameters associated with resistance:
Subtype 1a
Duration of treatment
Cirrhosis
Adding RBV
Fold change caused by the RAV
In the future, resistance testing may play a role in deciding how long to treat as well as what to use