New Treatments of Hepatitis C

PHM 142Fall 2015

Presented by: Chantel Asamoah (1002875365) Sarah He (1000762917)

Liborio Borsellino (1002875418) Theresia Wibowo (1000653027)

PHM142 Fall 2015Coordinator: Dr. Jeffrey HendersonInstructor: Dr. David Hampson

What is Hepatitis C?

Hepatitis C is a disease caused by a virus that infects hepatocytes. It can lead to liver scarring, cirrhosis (nodules), liver failure, and liver cancer.1

Hepatitis C Virus (HCV) is a positive strand RNA virus encoding for a polyprotein that undergoes a polypeptide cleavage to 10 polypeptides, each with different functions1

• Structural proteins: consist of 2 envelope proteins E1 & E2.1 Both envelope proteins target host antibody response.1

• Non-structural proteins: NS2, NS3, NS4A, NS4B, NS5A, NS5B1 Form a complex with viral RNA to initiate viral replication.1

The Life Cycle of Hepatitis C

What does it do to the body? 1) Virus goes to liver and starts to reproduce using host machinery

2) Sends immune cells to attack the virus and the liver cells infected with the virus1

3) These liver cells become inflamed and then die1

• Causes scar tissue on the liver1

• Untreated HCV can lead to cirrhosis1

Transmission of HCV

Transmitted through the blood1

Ex. sex, sharing toothbrushes, sharing razors, birth

Older Treatments of Hepatitis C: Interferon & Ribavirin

• Older treatment options are interferon-ribavirin drug regimens that have a 50-70% cure rate depending on the HCV genotype.

• Many patients can’t tolerate interferon due to side effects and comorbidities, while ribavirin is teratogenic1

• Used to treat Hepatitis C for 20 years

Interferon alpha is an inhibitor of HCV replication that induces specific host genes with antiviral functions1

Ribavirin acts in synergy with interferon alpha; boosts efficacy from 10% to 50%1

Ribavirin

Older Treatments of Hepatitis C: Interferon & Ribavirin

 

Process of how (endogenous) interferon

works: 1. Virus enters cell and use host

machinery to reproduce1

2. Interferon genes are turned on1

3. Produced and released by dying cell1

4. Binds to the receptor on the cell membrane which turns on genes for antiviral proteins1

5. Antiviral proteins block viral production1

 

Interferon alpha (exogenous) This drug induces host-genes that have anti viral function1

 Interferon side effectsCytopenia, depression, autoimmunity and rashes1

Ribavirin• Ribavirin competes with

guanosine in the formation of viral mRNA cap structure1

• Interferes with enzymes responsible for functional methylation which is crucial for the virus1

Protease Inhibitors

• Protease inhibitors2

• Boceprevir

• Telaprevir

• Simeprevir

• For genotype 1 infection

• Most common genotype worldwide3

• Least responsive to interferon and ribavirin based therapy so these treatments are used in conjunction with protease inhibitors3

• Direct-acting antivirals (DAA)- inhibit viral replication by targeting specific steps in the HCV life cycle 3

Boceprevir

Protease inhibitor of the hepatitis C virus non-structural protein serine protease2

Covalently and reversibly binds to NS3/4A protease active site through alpha-ketoamide functional group2

Prevents the polyprotein precursors from maturing into mature forms of NS4A, NS4B, NS5A, NS5B2

Sofosbuvir:A Nucleotide Analog

• Brand name: Sovaldi4

• Works 90% of the time on HCV genotype 2, 3, 44

• First interferon free HCV treatment5

• Sofosbuvir is a prodrug that is metabolized to its active form 2'-deoxy-2'-α-fluoro-β-C-methyluridine-5'-triphosphate (GS-461203)4

• GS-461203 is a uridine analog triphosphate5

Sofosbuvir: Mechanism of Action

• The NS5B protein made by the virus is a RNA polymerase5

• GS-461203 differs from uridine triphosphate because of the fluoro and methyl group on the 2’ carbon4

• GS-461203 competes with uridine triphosphate in the body for incorporation into the new RNA strand being made4

• This increased electronegativity of the flouro group causes irreversible binding and stops RNA replication4

Uridine triphosphate GS-461203

NS5A Inhibitors

DAA that directly inhibits NS5A protein, which is important in:

• Regulating viral RNA replication6

• Viral assembly6

• Inhibition of host cell apoptosis6

In the presence of NS5A inhibitor:

• Inhibition of viral replication and virion assembly6

• Inhibition of secretion from infected cell6

• Decline in HCV RNA levels

• Redistribution of NS5A from ER to lipid droplet6

NS5A Inhibitor Mechanism

Two different pathways in RNA replication:1. Inhibition of NSA hyperphosphorylation7

• Phosphorylation of NS5A required for viral production7

• Regulation of phosphorylation vs. hyperphosphorylation required for viral function7

2. Alteration the subcellular localization of NS5A, causing faulty viral assembly8

Daclatasvir (Daklinza)

• Combination with sofosbuvir (Harvoni) and simepravir WITHOUT interferon or ribavirin!6

• Minor side effects6

• Development of new treatments can potentially treat HCV without adverse effects of ribavirin and interferon6

Ledipasvir

• Targets HCV genotype 36

• Combination with sofosbuvir

Summary

Older treatment: Interferon & Ribavirin

Interferon side effects: Cytopenia, depression, autoimmunity and rashes

3 Examples of New Treatment

Protease inhibitors

• Broceprevir, Telaprevir, Simeprevir

• Inhibitors of genotype 1 infection

• Protease inhibitors used in conjunction with interferon and ribavirin

Sofosbuvir: A Nucleotide Analog

• Sofosbuvir is a prodrug that is metabolized to GS-461203, a competitor of uridine triphosphate

• The flouro group on GS-461203 causes irreversible binding to NS5B and stops RNA replication

NS5A inhibitors:

• Daclatasvir (Daklinza)

• Combination of ledipasvir & sofosbuvir (Harvoni)

• Combination of ledipasvir & simepravir

Act WITHOUT interferon & ribavirin

References1. T. Jake Liang, M.D., et al.(2013). “Current and Future Therapies for Hepatitis C Virus

Infection.” The New England Journal of Medicine. Web. 6 Nov. 2015.

2. Garnock-Jones, Karly. "Boceprevir." Drugs 72.18 (2012): 2431-56. ProQuest. 9 Nov. 2015 .

3. Perry, Caroline M. "Telaprevir." Drugs 72.5 (2012): 619-41. ProQuest. 9 Nov. 2015 .

4. Cada, Dennis J., Jasen Cong, and Danial E. Baker. “Sofosbuvir.” Hospital Pharmacy 49.5 (2014): 46

5. Stedman, Catherine. “Sofosbuvir, a NS5B Polymerase Inhibitor in the Treatment of Hepatitis C: A Review of Its Clinical Potential.” Therapeutic Advances in Gastroenterology 7.3 (2014): 131–140. PMC. Web. 10 Nov. 2015

6. Jean-Michel Pawlotsky, NS5A inhibitors in the treatment of hepatitis C, Journal of Hepatology, Volume 59, Issue 2, August 2013, Pages 375-382, ISSN 0168-8278, http://dx.doi.org/10.1016/j.jhep.2013.03.030.

7. Ying Huang, Kirk Staschke, Raffaele De Francesco, Seng-Lai Tan, Phosphorylation of hepatitis C virus NS5A nonstructural protein: A new paradigm for phosphorylation-dependent viral RNA replication?, Virology, Volume 364, Issue 1, 20 July 2007, Pages 1-9, ISSN 0042-6822, http://dx.doi.org/10.1016/j.virol.2007.01.042.

8. P. Targett-Adams, E.J. Graham, J. Middleton, A. Palmer, S.M. Shaw, H. Lavender, et al.Small molecules targeting hepatitis C virus-encoded NS5A cause subcellular redistribution of their target: insights into compound modes of action. J Virol, 85 (2011), pp. 6353–6368