Poster Presentation

1
Drugs for the therapy of HCVDr Ramesh R
RaiJaipur
2
Interferons
Comprise a group of related proteins Similar
to those produced by virus infected cells
EFFECTS
Antiviral Immunomodulatory
Enhancement of Major Histocompatibility Complex
antigen expression
3
Types of interferon

• Interferon alfa-2b
• Interferon alfa2a
• Interferon alfacon1 or Consensus Interferon
  recombinant Interferon
• Interferon alfan1, produced from a human B
  lymphoblastoid cell line, not approved for use in
  HCV Infection
• Pegylated interferon
• covalently bound to 40 kd polyethylene glycol
• advantage once weekly dosage
• more sustained absorption (time to peak plasma
  concentration increased 7 fold)
• reduced clearance (10 fold)
• smaller volume of distribution (4 fold)
• sustained more uniform interferon concentration
  compared to standard preparations

4
Mechanism of action activation of TH and TC
cells in response to viral or bacterial infection
(1)
Ag antigen MHC I major histo-compatibility
antigen class I MHC II major histo-compatibility
antigen class II TH T-helper cell TC cytotoxic
T cell APC antigen presenting cell Interleukin
IL interleukin Ab antibody APC antigen
presenting cell
Bacterium engulfed by phagocytic cell, Ag
processed and expressed on surface of APC in
conjunction with MHC II
Recognition of Ag MHC II by TH cell
Bacterial Ag Viral Ag MHC I MHC II
5
Mechanism of action activation of TH and TC
cells in response to viral or bacterial infection
(2)
TH activation
TH activation
Release cytokinese.g. IL-2, -4, -5, -6
B
Tc
Promotes activation and proliferation of TH, TC
and B cells
Interacts with B cells to promote B-cell
proliferation, activation and Ab secretion
Interacts with TC cell to promote TC cell
activation
Antibody response
Activated Tc cell binds virus-infected cell
neutralization of virusmediate formation of
complement complexpromote phagocytosis of
infectious agent
Lysis of infected or cancerous cell
6

• Effects of interferon-alpha

TH
TS
Interferon
TH, T-helper cell NK, natural killer cell TC,
cytotoxic T cell TS, suppressor T cell
NK
TC
MHC class I antigen
2-5A synthetase
Infected cell
7
Mechanism of action of interferon
Interferon induced Protein kinase PKR 2',5'
oligoadenylate Latent enzymes (inactive) synth
etase (inactive) Product of
Double stranded Virus infection
RNA Active enzymes Phosphorylated 2',5'
oligoadenylate PKR (active) synthetase
(active) Initiation factor Phosphorylated ATP
2',5'oligo AMP elf - 2? elf -
2? adenylates Phosphatase
Ribonuclease L RNase
L (inactive) (active) Inhibition
of Inhibits initiation Degrades mRNA Protein
synthesis of translation and rRNA
8
Mechanism of action of interferon
NSSA IFN PKR ADAR 2.5(A) Synthetase
dsRNA PACT dsRNA dsRNA Bc
l-2 Bcl-X 2.5 (A) PKR E2 RNA ed
iting Transcriptional elf-2? Signaling Trans
lation RNaseL inhibition Apoptosis
Apoptosis mRNA Altered mRNA
degradation translation
9
Viral kinetics early viral response to IFN
therapy
Lag
First phase
HCV Load (log10 IU/mL)
Second phase
Detection limit
Day
Neumann AU et al. Science. 1998282103-107.
10
Nomenclature of initial virological response
7
Nonresponder (c lt0.2)
6
First phase
5
Partial responder
4
Serum HCV RNA (log10 IU/mL)
Second phase
3
Detection limit
2
Rapid responder (d ?0.35)
1
0
1
2
3
7
14
21
28
Day
c rate of clearance d rate of infected-cell
death.
Zeuzem S et al. Gastroenterology.
20011201438-1447.
11
Time course of virological response to IFN
therapy in patients with CHC
100
Inhibition of viral replication
HCV RNA
Immune system elimination of infected cells
Induction phase
Maintenance phase
Detection limit
0
1428 Days
?
1st dose
Zeuzem S et al. Gastroenterology.
20011201438-1447.
12
Treatment goals of therapy

• Primary objective cure
• No virus1
• No progression(histology/fibrosis)
• No symptoms

• Secondary objective slow / prevent
• Slow fibrosis1
• Slow cirrhosis2
• Prevent decompensation
• Prevent HCC2

1. Worman HJ. Hepatitis C Current treatment. 2.
Peters MG et al. Medscape HIV/AIDS eJournal.
20028(1). 3. Nishiguchi S et al. Lancet.
19953461051-1055.
13
Virological response definitions

• End-of-treatment response
• Undetectable HCV RNA levels (lt50 IU/ml) at the
  end of treatment (24 weeks for HCV genotype
  non-1, 48 weeks for HCV genotype 1)
• Sustained virological response
• Undetectable HCV RNA levels (lt50 IU/ml) at end of
  follow-up (24 weeks post treatment)
• Nonresponse
• Detectable HCV RNA levels (50 IU/ml) at the end
  of treatment
• Breakthrough
• Undetectable HCV RNA levels during treatment, but
  return to detectable HCV RNA levels prior to
  completion of therapy
• Relapse
• Patient who is HCV RNA negative at the end of
  treatment but subsequently becomes positive
  during the follow-up period

14
Patterns of virological response
Baseline
Treatment
Nonresponder
Breakthrough
HCV RNA
Partialresponder
Relapser
Sustainedresponder (cure)
Detection limit
HCV RNA Undetectable
6 months
Time
15
Limitations of conventional IFN alfa therapy

• Rapid absorption after subcutaneous injection
• Wide fluctuation in serum concentration
• Inadequate antiviral coverage
• Vast systemic distribution
• High renal clearance
• Short serum half-life (2 to 5 hours)

16
Pegylated interferons protein pegylation

• Addition of polyethylene glycol (PEG) moiety to
  protein may result in1
• Prolonged plasma half-life (increased conc. 7
  folds)
• Reduced clearance (10 folds)
• Less immunogenicity
• Characteristics of new protein depend on1,2
• Structure of PEG moiety (eg, size, branching,
  linkage bond strength)
• Site(s) of attachment to parent compound

1. Delgado C et al. Clin Rev Ther Drug Carrier
Syst. 19929249-304. 2. Hoffmann-La Roche.
Roche Facets.
17
Peginterferon alfa-2a 40KD

• Pegylation makes a difference

IFN
Stable amide bond
Large branched-chain PEG
18
Peginterferon alfa-2b 12KD
His-34 of IFN
O
H
Prodrug of IFN
H3C-(OCH2CH2)n-O-C-N N
H
Urethane bond
Small linear-chain PEG
Wang Y-S et al. Biochemistry. 20003910634-10640.
19
(No Transcript)
20
Optimizing IFN alfa pharmacokinetics
Optimized PK
Higher-dose IFN ?
Serum Levels
Conventional IFN ?
Time
1 Week
21
Mean concentration-time profiles of
multiple-dose injections
PEG-interferon 40
PEG-interferon 12
1200
Tue
Wed
Thu
Fri
Sat
Sun
Mon
0.5 mg/kg qw 1.0 mg/kg qw 1.5 mg/kg qw
30
1000
25
800
20
Concentration (pg/mL)
600
Concentration (ng/mL)
15
400
10
200
5
0
0
0
24
48
72
96
120
144
168
0
24
48
72
96
120
144
168
Hour
Hour
Adapted from Glue P et al. Clin Pharmacol Ther.
200068556-567.
Modi MW. AASLD Annual Meeting. 2000.
22
Pharmacokinetics of peginterferon alfa-2a 40KD
Tue
Wed
Thu
Fri
Sat
Sun
Mon
30
25
PEG-IFN ?-2a (40KD)180 mg qw
20
Mean Concentration(ng/mL)
15
10
5
0
0
24
48
72
96
120
144
168
Hour
After first dose1
After steady state2
1. Algranati NE et al. AASLD Annual Meeting.
1999. 2. Modi MW. AASLD Annual Meeting. 2000.
23
Pegylated interferons pharmacokinetic properties
Varies according to patient body weight. Does
not vary according to patient body weight.
1. Perry CM, Jarvis B. Drugs. 2001612263-2288.
2. Glue P et al. Clin Pharmacol Ther.
200068556-567. 3. PEG-Intron. PDR . 56th
ed. 2002. 4. ROFERON-A. PDR . 56th ed. 2002.
5. Reddy KR. Ann Pharmacother. 200034915-923.
6. Hoffmann-La Roche. PEGASYS Monograph. 7.
INTRON A. PDR . 56th ed. 2002.
24
Metabolic fate of peginterferon alfa-2a 40KD
metabolism and excretion via urine and bile
PEG attached to IFN fragments
PEG-IFN ?-2a (40KD)
PROTEASES
URINE
BILE

• PEG-IFN ?-2a (40KD) is metabolized in the liver
  and other organs by nonspecific proteases the
  metabolic products are excreted readily in the
  urine and the bile1,2
• The PEG moiety is inert and eliminated from the
  body in 50 to 60 days1

1. Modi MW et al. Hepatology. 200032(suppl)394A.
2. Algranati NE et al. AASLD Annual Meeting.
1999.
25
Pegylated IFNsdosing and administration
PEG-Interferon 12
PEG Interferon 40
WEIGHT-based dosing
FIXED dose
Lyophilized powder that needs to be reconstituted
before each injection
Dispensed as a stable solution ready for
injection
1. PDR . 56th ed. 2002. 2. Perry CM, Jarvis B.
Drugs. 2001612263-2288.
26
PEG attachment versus detachment
PEG Interferon 40 (Stable Bond)
PEG-Interferon 12
PEG
PEG
IFN
IFN
Absorption
PEG
BLOOD
Slowerdegradation by peptidases
Rapid degradation by peptidases
Biliary Excretion
27
Peginterferon alfa-2a 40KD need not be dosed by
weight
The volume of distribution for PEG-IFN a-2a
(40KD) varies little with body weight
Lamb MW, Martin NE. Ann Pharmacother.
200236933-935.
28
Side effects of interferon therapy

• Flu like symptoms, hematological
  thrombocytopenia leucopenia,
• auto-immune hemolytic anaemia
• Psychiatric Insomnia, irritability,
  depression. Rarely, suicidal ideation
• Auto- immune flare of auto-immune conditions
  of thyroid, hyperglycemia
• Cardiac Cardiomyopathy
• Renal Interstitial nephritis
• Pulmonary Interstitial pneumonia,
  bronchiolitis obliterans.
• Neurological Peripheral neuropathy
• Ophthalmic cotton-wool spots, hard exudates,
  retinal vascular thrombosis

29
Ribavarin

• Ribavarin is a nucleoside analogue, structurally
  similar to guanosine
• Broad spectrum anti-viral activity
• Inhibits replication of RNA viruses
• Less inhibition of DNA viruses
• Mode of action is not completely understood

30
Mechanism of action of ribavarin

• Inhibition of viral dependent RNA polymerase
• Inhibition of 5' cap' structure of viral m-RNA
• Depletion of intracellular nucleotide
  triphosphate pool by direct
• inhibition of inosine phosphate
  dehydrogenase (IMDH)
• Induction of mutations into viral genome
• Shift of Cytokine balance from anti-inflammatory
  (Th2) to
• pro-inflammatory Th1

31
Ribavarin mono-therapy

• Decrease in amino-transferases during therapy
• Ineffective in decreasing / eliminating HCV RNA
• Modest benefit in hepatic inflammation
• Little improvement in fibrosis
• Limited role in treatment of CHC

32
Adverse effects of ribavarin therapy

• Hemolysis
• Nausea
• Fatigue
• Nasal congestion
• Vertigo
• Pruritus
• Insomnia
• Anorexia
• Mutagenicity / Teratogenicity
• Mild reversible increase in serum bilirubin and
  uric acid

33
Efficacy results of HCV therapy SVR
70
61
60
54
50
41
39
40
SVR ()
25
30
16
20
6
10
0
IFN 24 wk 19981
IFN 48 wk 19981
IFN RBV 19981,2
PEG-IFN 20003,4
PEG-IFN RBV 20025,6
1. McHutchison JG et al. N Engl J Med.
19983391485-1492. 2. Poynard T et al. Lancet.
19983521426 -1432 3. Zeuzem S et al. N Engl J
Med. 20003431666-1672. 4. Lindsay KL et al.
Hepatology. 200134 395-403 5. Manns MP et al.
Lancet. 2001358958-965. 6. Hadziyannis SJ.
EASL Annual Meeting. 2002.
34
Predictors of response to IFN ribavarin therapy

• Genotype 1b respond worse than genotype 2 or 3
• Viral titers Possibly related to underlying
  genotype or genetic variability as quasi-species.
  High titers respond poorly
• Liver Histology Mild inflammation and low stage
  of fibrosis predict better response than bridging
  fibrosis/ cirrhosis
• Interferon sensitivity determining region ( ISDR
  ) Mutations in NS5A region coding for this
  segment of viral genome show better response at
  least in genotype 1b
• Iron overload / concomitant alcohol intake
  Predict poor response in some studies

35
Dose modification of ribavarin and IFN according
to hematologic parameters
Parameter Dose modification Discontinuation
Hemoglobin lt 10 gm / dl lt 8.5 gm / dl W.B.C.
Count lt 1500 / µL lt 1000 / µL Neutrophil
Count lt 750 / µL lt 500 / µL Platelet Count
lt 50,000 / µL lt 25,000 / µL Change in
dose of Ribavarin (600 mg/day) Change in dose
of IFN (1.5 MU, TIW)
36
Contra-indications to use of IFN ribavarin
therapy

• Cytopenia
• Major psychiatric illness
• Cardiac diseases
• Poorly controlled diabetes
• Seizure disorders
• Auto immune / potentially autoimmune diseases

Drop in Hb lt 2 gm / dl over 4 weeks or Hb
level lt 12gm/dl after 4 weeks of Ribavarin
therapy in a cardiac patient warrants
modification or discontinuation of T/t