Transcript New drugs for hepatitis C

PHM142 Fall 2016
Coordinator: Dr. Jeffrey Henderson
Instructor: Dr. David Hampson
Newest Drugs for Hepatitis C
Matthew Luu, Yuan Fang (Pearl) Cai, Shiming Sun,
Ziyi Cheng
What is Hepatitis C?
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Flaviviridae virus family
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Liver cells are primary host cells
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(+) single-stranded lipid-enveloped RNA virus
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Genotype variants and sub-variants (eg. genotype 1,2)
60-85% Chronicity
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Liver cirrhosis → Hepatic Failure → Hepatocellular Carcinoma
Hepatitis C Life Cycle
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Flaviviridae binds hepatocytes to trigger receptor-mediated
endocytosis and undergoes decapsidation in cytoplasm
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Translation of viral genome in rough ER produces a
polyprotein
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Cleaved by cellular and viral proteases to structural and
nonstructural proteins (NS) functioning in viral replication
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NS5A forms membranous web
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NS5B RNA-dependent RNA polymerase
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NS3/4A serine protease
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Core protein binds lipid droplet for assembly
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Assembled virion bud out of cell via membrane
Bartenschlager, R., Cosset, F., & Lohmann, V. (2010). Hepatitis C virus replication cycle. Journal of Hepatology, 53(3), 583-585.
NS5A Protein: Overview
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Interact with other nonstructural proteins
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Consists of a lead sequence followed by three
domains
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The α-helix anchor NS5A into cell membrane
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A pivotal component of membranous web replication
complex
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All three domains necessary for viral replication
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3961994/
NS5A protein: Structure
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Domain I contains Zinc-binding and RNA-binding
motif
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Domain II and III are unfolded
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Domain I is essential for HCV replication.
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Domain II is associated with RNA replication and
Domain III is important for virus assembly
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Dimeric structure is consistent with surface
interactions with other proteins, RNA molecules and
cell membranes
Crystal Structure of NS5A Dimer Domain I
Genotype 1a (A), and 1B (B)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4093949/
NS5A inhibitors
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Exact inhibitory mechanisms of these molecules on
HCV is unknown
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Conserved symmetrical molecules
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Suggest that they act on dimer of NS5A proteins
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Examples include Daklinza and Ledipasvir
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4093949/
Daklinza
• Highly specific and potent NS5A inhibitor
• Directly binds to HCV NS5A at dimer interface
• Induces an alteration in the subcellular
localization of HCV NS5A proteins, which
inhibits the formation and activation of HCV
replication complexes
• Blocks intracellular HCV RNA synthesis, virus
assembly and secretion
http://pillsgermany.com/tovar/daklinza/
Sofosbuvir: NS5B Inhibitors
• In Canada, sofosbuvir is the only available
nucleoside inhibitor of NS5B
• There are 3 therapies:
1. Genotypes 1 and 4: Sofosbuvir + Peginterferon +
Ribavirin
2. Genotypes 2 and 3: Sofosbuvir + Ribavirin
3. Most recently, genotype 1: Sofosbuvir + Ledipasvir
Ledipasvir inhibits HCV RNA replication and virion
production by targeting the HCV NS5A protein.
Mechanism: Sofosbuvir
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Sofosbuvir: prodrug
active
antiviral agent 2'-deoxy-2'-αfluoro-β-C-methyluridine-5'triphosphate.
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The triphosphate acts as a
defective substrate for the
NS5B protein.
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NS5B is the viral RNA
polymerase, thus sofosbuvir
acts as an inhibitor of viral RNA
synthesis.
Drug-drug Interactions: Sofosbuvir + Ledipasvir
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Sofosbuvir and ledipasvir: substrates of drug
transporter P-gp.
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P-gp/MDR1: ATP-dependent efflux pump;
expressed in the intestinal apical side; pumps
drugs back into the intestinal lumen
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P-gp inducers decrease sofosbuvir and
ledipasvir plasma concentration; reduced
therapeutic effect; loss of virologic response.
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P-gp inhibitors may be coadministered with
sofosbuvir or ledipasvir
http://www.cyprotex.com/useruploads/Transporters_inte
stines.jpg
NS3/4A
NS3
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Protein involved in viral replication with both a protease and helicase domain
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Protease activity - important for generating viral non-structural proteins that are required for HCV replication
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Cleavage of four sites of the HCV polypeptides (post-translational processing) - essential of viral replication
Helicase activity - important for RNA replication
NS4A
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Cofactor involved in enhancing the activity of NS3
NS3/4A Inhibitors
• Serine Protease Inhibitors
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Linear alpha-ketoamide derivatives that
covalently bind to the active site (located
between the His57 and Asp81 of the N terminal,
and Ser139 of the C terminal). I.e. Boceprevir,
Telaprevir
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Prevents the cleavage of the HCV polypeptide at
four sites: NS4A,NS4B, NS5A, NS5B
• Used in combination with other HCV drugs
http://www.nature.com/nbt/journal/v29/n1
1/full/nbt.2031.html
Zepatier
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Fixed-dose combination drug containing elbasvir (NS5A inhibitor) and grazoprevir
(NS3/4A inhibitor) for treatment of HCV genotype 1 and 4.
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Works by stopping the viral replication and assembly.
Summary
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Hepatitis C is a (+) single-stranded RNA virus from the Flaviviridae family
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Translation in host cell (hepatocytes) RER creates polyprotein which is cleaved into structural and non-structural proteins by host and viral proteases
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Treatments of HepC targets NS5A, NS5B and NS3/4A protease
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Effect of compounds targeting NS5A on HCV replication is unknown
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Daclinza is a potent NS5A inhibitor and is most effective and resistant to mutations when used with other HCV drugs like Harvon
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NS5B Inhibitor Sofosbuvir acts as a defective substrate which binds with RNA polymerase. By blocking RNA polymerase, the RNA synthesis and life cycle of HCV is stopped.
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Sofosbuvir and ledipasvir are substrates of efflux transporter P-gp. To maintain effective plasma concentration of these drugs, we may need to co-administer P-gp inhibitors.
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It is highly anticipated that sofosbuvir may play a key role in future all-oral regimens for the treatment of genotype 1 HCV infections
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N3/4A serine protease inhibitors works by inhibiting the formation of new replication sites
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NS3/4A serine protease inhibitors works in combination of other HCV drugs
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Zepatier is a combination of Elbasvir (NS5A inhibitor) and Grazoprevir (NS3/4A inhibitor)
References
Akiyama S (Dec 2001). "[Mechanisms of drug resistance and reversal of the resistance]". Human Cell. 14 (4): 257–60. PMID 11925925
Drugs, N. E. W. (2015). Daclatasvir. Australian Prescriber, 38(6), 217–219.
Bartenschlager, R., Cosset, F., & Lohmann, V. (2010). Hepatitis C virus replication cycle. Journal of Hepatology, 53(3), 583-585.
Carrion, A., Martin, P. (2016). Safety and efficacy of elbasvir and grazoprevir for treatment of hepatitis C. Expert Opinion on Drug Safety, 15(6): 883-890.
Dugum M, O'Shea R. Hepatitis C virus: here comes all-oral treatment. Cleve Clin J Med 2014;81(3):159-72.
Lambert, S. M., Langley, D. R., Garnett, J. A., Angell, R., Hedgethorne, K., Meanwell, N. A., & Matthews, S. J. (2014). The crystal structure of NS5A domain 1 from genotype 1a reveals new clues to the
mechanism of action for dimeric HCV inhibitors. Protein Science : A Publication of the Protein Society, 23(6), 723–734.
Liang, J., Ghany, MG. (2013). Current and Future Therapies for Hepatitis C Virus Infection. The New England Journal of Medicine, 368:1907-1917
McGivern DR, Masaki T, Lovell W, Hamlett C, Saalau-Bethell S, Graham B. (2015). Protease Inhibitors Block Multiple Functions of the NS3/4A Protease-Helicase during the Hepatitis C Virus Life Cycle.
Nakamoto, S., Kanda, T., Wu, S., Shirasawa, H., & Yokosuka, O. (2014). Hepatitis C virus NS5A inhibitors and drug resistance mutations. World Journal of Gastroenterology : WJG, 20(11), 2902–2912.
Salam, KA., Akimitsu, N. (2013). Hepatitis C Virus NS3 Inhibitors: Current and Future Perspectives. BioMed Research International. 467869, 9 pages.
Nakamoto, S., Kanda, T., Wu, S., Shirasawa, H., & Yokosuka, O. (2014). Hepatitis C virus NS5A inhibitors and drug resistance mutations. World Journal of Gastroenterology, 20(11), 2902–12.
https://doi.org/10.3748/wjg.v20.i11.2902
Obrien, C., & Agresti, N. (2012). NS5A inhibitors. Current Hepatitis Reports. https://doi.org/10.1007/s11901-012-0138-2