1. New Treatments for Hepatitis C
Harshan Gill
Felix Ho
Kyle Yuen
Chengming Zhang
November 14, 2017
PHM Fall 2016
Coordinator: Dr. Jeffrey Henderson
Instructor: Dr. David Hampson

2. Sofosbuvir = Hepatitis C Polymerase Inhibitor
Nonstructural protein 5B (NS5B) is a RNA polymerase in the hepatitis C virus (HCV).
Sofosbuvir is a nucleotide analog NS5B inhibitor used to treat chronic HCV genotype 1, 2, 3, or 4 in adults.
Sofosbuvir is given orally as a tablet.

3. Metabolism of Sofosbuvir in the Liver
The carboxylate ester of sofosbuvir is hydrolyzed by cathepsin A or carboxylesterase 1.
The phosphoramidate of sofosbuvir is cleaved by histidine triad nucleotide-binding protein 1 (Hint1).
Repeated phosphorylation creates the active triphosphate GS
Dephosphorylation creates the inactive metabolite GS

4. Mechanism of Action of Sofosbuvir
GS = pharmacologically active uridine analog triphosphate
GS competes with natural nucleotides for insertion by NS5B (RNA polymerase) into the growing RNA strand during viral genome replication. GS differs from natural pyrimidine nucleotides because it has an additional methyl and fluoro group at the 2’ position.
It has been proposed that the 2' methyl group of GS causes a steric clash with an incoming nucleotide. Thus, insertion of GS into viral RNA prevents RNA elongation by NS5B, resulting in premature termination of RNA synthesis. HCV replication will stop.

5. Telepravir (Incevek/Incivo)
Indicated for Hepatitis C, Genotype 1
Inhibitor of NS3/4A serine protease
One of many drugs of a class known as protease inhibitors
NS3: non-structural protein 3 is a cleavage product of the HCV polypeptide and acts as a serine protease
NS4A: cofactor for the NS3 serine protease

6. Mechanism of Action Irreversible inhibition of the NS3/4A complex
Prevents activation of the “The Real MVP” for HCV
NS3 contains protease and RNA helicase
Metabolized into pyrazinoic acid by CYP3A4 (inactive)
David Spach, MD & H. Nina Kim, MD
Hepatitis Web Study: Hepatitis C Online

7. Clinical Applications
PROVE3, REALIZE, and ADVANCE trial demonstrated efficacy of Telapravir in combination with peginterferon alfa-2a and ribavirin (the standard of care for HCV)
In patients whom the standard had failed, the likelihood of sustained viral response (aviremia period) was increased
The addition of telaprevir increased SVR from 14% to 53%
REALIZE showed rates increasing from 14% on standard alone to 83-87% with Telapravir + standard in relapsed patients
ADVANCE showed increased rates in untreated patients up to 75% SVR with Telapravir + standard from 44% with standard alone
Telaprevir for previously untreated chronic hepatitis C virus infection. (2011)

8. Boceprevir Protease Inhibitor of HCV (Targets NS3-NS4A)
Prevents viral replication because it binds to the protease machinery of HCV

9. Mechanism of Action Binds irreversibly to the NS3 active site
NS3 is essential in cleaving (activating) non-structural viral proteins from the HCV polypeptide
NS3-NS4A also cleaves signaling proteins such as TRIF which disrupts the synthesis of proinflammatory cytokines such as interferons
“Dual function from blocking NS3”
Interferon Type I (IFN-alpha and IFN-beta)

10. Clinical Results Interferons are important in antiviral responses
Phase 3 clinical trials conducted showed 68% of the experimental group (boceprevir + PEGylated interferon + ribavirin) had no detectable viruses while the standard of care (PEGylated interferon + ribavirin) is 40% (P < 0.001)
Approved by FDA on May 14, 2011
Standard of care is pegylated interferon and ribavirin (stop viral RNA synthesis as a nucleoside inhibitor). IFN alpha primes NK cells and increases HLAII

11. IFNα treatments
Early Hepatitis C virus (HCV) treatments included interferon treatments with sustained viral response (SVR) rates between %.
Marketed as Pegasys® in the USA.
Used in conjunction with Ribavirin (RBV) and other DAAs for nearly 92% cure rate in HCV type 1.
Pegylated Interferon alpha 2a (PegIFNα-2a)
Induces genes involved in antiviral activity, apoptosis and inflammation.
Newer treatments involve PegIFN α2a/RBV along with Sofosbuvir and Simeprivir to increase SVR up to >90%
SVR means that after stopping treatment, viral RNA should be less than 15 IU/mL.
Pegasys costs roughly $12-14,000 over 12 weeks.
Pegylated IFN just means they added a polyethylene glycol moiety to the IFN 2a.
This decreases SubQ absorption and decreases clearance to give an overall 20X increase in half life
IFN stimulates
New therapies involving IFNa-2a are triple therapies with two direct acting anti-virals (DAAs) with the addition of IFN to mediate effectiveness of DAAs. Older triple therapies had higher adverse events.
Complications of chronic HepC infection include liver cirrhosis and hepatocellular carcinoma
Treatments involving IFN tend to reduce hepatocellular carcinoma and liver cirrhosis progression.

12. Boson study HCV genotype 2&3 patients in multiple countries.
Treatment for genotype 2 patients with Sofosbuvir, Ribavirin and PegIFNα was able to achieve similar SVR rates in 12 weeks compared to Sofosbuvir and Ribavirin together for 24 weeks (94% vs. 100%)
Treatment for genotype 3 patients with SOF/RBV + PegIFNα showed 93% SVR rates after a 12 week treatment. SOF/RBV treatment for 16 and 24 weeks resulted in 71% and 84% SVR respectively.
In genotype 2 HCV, patients were able to achieve similar results in half the time as using double Direct Acting Antiviral therapy.
In genotype 3 HCV, 50 patients treated with SOF/RBV relapsed after measuring SVR compared to only 9 with the SOF/RBV+pegIFN

13. Mechanism The HCV NS3/4A Serine protease complex
“The real MVP” for HCV
PegIFNα is a replacement for IFNα.
It induces genes responsible for innate immunity.
Increases activation of macrophages, NK cells, killer T cells and neutrophils.
The HCV serine protease cleaves two important proteins involved in

14. Summary Sofosbuvir = Hepatitis C polymerase (NS5B) inhibitor
Telaprevir = Hepatitis C protease (NS3/4A) inhibitor
Boceprevir = Hepatitis C protease (NS3/4A) inhibitor
PegIFNα induces genes involved in antiviral activity, apoptosis, and inflammation .
NS5B uses HCV positive RNA strand as a template to link ribonucleotide triphosphates together during RNA replication.
NS3 cleaves (activates) non-structural viral proteins from the HCV polypeptide.

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