Epidemic and Pandemic Use of Antivirals Introduction

1
Epidemic and Pandemic Use of AntiviralsIntroduct
ion
15 September 2008 Frederick G. Hayden,
M.D. University of Virginia Health
System Charlottesville, Virginia, USA
2
Antiviral Agents for Influenza
3
Antivirals for Influenza Overview

• Effective for prophylaxis and early therapy
• Useful in outbreak control
• Rapid antiviral effect
• Differing anti-influenza spectra
• Amantadine/rimantadine influenza A only
• Oseltamivir/zanamivir influenza A B
• Favorable PK characteristics
• Treatment 2X/d prophylaxis 1X/d
• Few drug interactions
• Differences in dosing routes, PK, tolerance,
  efficacy, and resistance profiles

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M2 Inhibitor Prophylaxis During Pandemic Influenza
Hayden. J Infect Dis 176S56, 1997
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Influenza Prevention In Households PEP
Index case given treatment
6
Antiviral Treatment of Acute Influenza
? No placebo-controlled study or not reported
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Oseltamivir Treatment Effects in A(H5N1) Infection
Adapted from Writing Committee of Second WHO
Consultation on Human H5 Infections. N Engl J Med
358 261, 2008
8
Resistance to M2 Inhibitors (S31N) in Community
Isolates of A/H3N2, 2000-07

Bright et al. Lancet 2005, JAMA 2006 Klimov et
al. CDC unpublished Barr et al. Antiviral Res
2006 R Saito, Niigata Univ, unpublished
9
Oseltamivir Resistance in H1N1 (H274Y)

• Rare in community H1N1 isolates, 1996-2007
• 0 to lt1 in most surveys
• 2.2 in Japan in 2005-6 (but not in 2006-7 or
  early in 2007-8)
• High prevalence in Europe and globally, 2007-8
• Patients without known oseltamivir use or
  exposure to those on drug
• Generally no obvious epidemiologic links
• Household contacts, several apparent clusters
• Typical influenza illness some fatalities
• Efficient person-to-person transmission

10
Oseltamivir Resistance in H1N1 Viruses
4Q07- 1Q08 2Q08-20Aug08 http//www.w
ho.int/csr/disease/influenza/h1n1_table/en/index.h
tml 20 Aug 08
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Antivirals for Seasonal, A(H5N1), and Pandemic
Influenza Efficacy, Resistance, and New Agents
15 September 2008 Frederick G. Hayden,
M.D. University of Virginia Health
System Charlottesville, Virginia, USA
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Do We Need New Anti-Influenza Agents?

• Antiviral resistance
• Global spread of M2 inhibitor resistance in H3N2
  gt H1N1
• New emergence of oseltamivir-resistant H1N1
• Dual M2 and NAI resistance in IC hosts
• Antiviral efficacy incomplete in H5N1 disease
• Oseltamivir resistance emergence
• Safety/efficacy ? in risk populations infants lt
  1 yr, pregnancy, hospitalized, IC hosts
• Lack of parenteral agents

13
Viral Loads and Antiviral Treatments in
Immunocompromised Host with Fatal
Oseltamivir-Resistant H1N1 Illness

• 67 yo male with CLL recent chemoRx ?
  neutropenia
• Fever, cough, SOB ? acute respiratory failure

Re-intubation ?
Extubation ?
Intubation ?
? Oseltamivir resistance (H274Y) ?
Amantadine resistance (L26F)
Van der vries et al. NEJM 3591074, 2008
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Medical Needs for Anti-Influenza Antivirals

• Greater antiviral efficacy? greater clinical
  benefit
• Safety and efficacy in special risk populations
  infants lt 1 yr, pregnancy, hospitalized,
  immuno-compromised
• Reliable drug delivery in seriously ill patients
• Manage antiviral resistance
• Combinations

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Influenza Virus Replication and Sites for
Antiviral Inhibition
De Clercq. Nature Reviews- Drug Discovery 51015,
2006
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Investigational Anti-Influenza Agents

• Neuraminidase (NA) inhibitors
• - Zanamivir (IV), peramivir (IV/IM), A-315675
  (oral)
• Long-acting NA inhibitors (LANI)
• CS8958/R-118958 (topical), Flunet? (topical)
• Conjugated sialidase- DAS181 (topical)
• HA inhibitors- cyanovirin-N, sialyl-glycopolymer,
  arbidol
• Polymerase inhibitors- ribavirin viramidine
  siRNA T-705
• Protease inhibitors- aprotinin
• Biologics- antibodies, interferons

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Investigational Agents in Clinical Development
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Neuraminidase Inhibitors
Peramivir
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NA Inhibitor Resistance Profiles
Mishin et al. AAC 494516, 2005 Wetherall et al.
AAC 41742, 2003 Abed et al. Antiviral Res 77
163, 2008
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• IV zanamivir 600 mg or placebo twice daily X 5
  days starting 4 hr before virus inoculation
• Highly protective against experimental infection
  (14 vs 100), virus shedding (0 vs 100), and
  illness

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Pharmacokinetic Profiles of Intravenous and
Intramuscular Peramivir
Intravenous
Intramuscular

• Linear PK prolonged plasma T1/2elim (18 20 hr)

Kilpatrick JM, et al. Pharmacokinetics and Safety
of Peramivir by Intramuscular Administration,
Options for the Control of Influenza VI, Toronto,
2007
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IM Peramivir Time to Alleviation of Illness
J Alexander, BioCryst Pharmaceuticals,
unpublished data
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Long Acting Neuraminidase Inhibitors (LANI)- 2
Strategies
CS-8958
FLUNET
R-125489
Pro-drug Clinical
Dimer Preclinical
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Yamashita et al. 43rd ICAAC, Abstract no. F-1830,
2003
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• Double-blinded trial found that inhaled CS-8958
  administered once only was not statistically
  different than standard oseltamivir regimen.

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T-705 Summary of Pre-Clinical Findings

• Inhibitory for influenza A, B, C viruses EC50s
  0.01 - 0.5 µg/ml
• Active against flavi, arena, bunya, picorna,
  alpha, and paramyxo viruses
• Cytotoxicity for mammalian cell gt 1,000 µg/ml
• Triphosphate is inhibitor of influenza RNA
  polymerase.
• Active orally in murine models

6-fluoro-3-hydroxy-2- pyrazinecarboxamide
Furuta et al. AAC 46977, 2002 AAC 49981, 2005
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Mode of T-705 action (Hypothesis)
Nucleosidase
T-705
T-705 ribofuranose
Nucleoside- kinase
5- Nucleotidase
Phosphoribosyl - transferase
Weak inhibition of IMPDH
T-705RMP
Nucleotide- kinase
Nucleotidase
Potent inhibition of influenza viral polymerase
AAC 49981 (2005)
T-705RTP
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T-705 In Vitro Activity vs Ribavirin
Furuta Y, et al. Antimicrob Agents Chemother.
200549981-986.
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Effect of a T-705 Treatment in Mice Exposed to
Lethal A/Duck/N/1525/81 (H5N1) Virus





P lt .01 relative to control



Survival ()
Delay before starting treatment following viral
exposure, hours
Sidwell RW, et al. Antimicrob Agent Chemother.
200751845-851.
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Pharmacokinetics of Oral T-705

• Bioavailability gt 97 in mouse
• Rapid absorption in humans (Tmax lt 1 hr)
• Plasma T1/2elim from 1.3 to 3.9 hr
• Mainly excreted as T-705M1 in urine
• Single doses up to 1,600 mg or multiple up to 400
  mg tid for 7 days well tolerated

Single oral doses of T-705 over a range of 30 to
1600 mg
Toyama Chemical Co, unpublished
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Molecular Model of DAS181 (Fludase)

• Fusion construct with catalytic domain of A.
  viscosus sialidase and an epithelium-anchoring
  domain (human amphiregulin)
• Active against both a2,6- and a2,3-linked sialic
  acid receptors

Malakhov et al. AAC 501470, 2006
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Preclinical Features of DAS181

• Inhibitory for range of influenza A and B viruses
  
• In vitro EC90 values 1-14 nM
• Epithelial tag increases activity 5-30 fold
• Pretreatment (24 hr) effective
• Intranasal dosing shows
• Prophylactic and therapeutic activities in mice
• Antiviral effects with reduced inflammatory
  responses in ferrets

Malakhov et al. Antimicrob Agent Chemother
501470, 2006
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Effect of DAS181 on S. pneumo Binding to Human
Airway Epithelium (HAE) Cells

• DAS181 treatment had no significant effect on
  adherence.

Nicholls et al. J Antimicrob Chemother 62426,
2008
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DAS181 Treatment in Mice with H5N1

• Dose of 1 mg/kg/d for 7-8 d
• Inoculum of 3 MLD50
• Time-to-treatment effects on survival and lung
  titers on day 3 and 6.

Belser et al. JID 1961439, 2007
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• Literature review for reports of using
  convalescent blood products in treating pneumonia
  patients hospitalized in 1918-20
• 8 studies total of 336 treated patients
• 1,219 controls received supportive care
• None blinded, randomized, or placebo-controlled
• Overall mortality reduced from 37 to 16
  (difference 21 95 CI, 15 - 27).
• Benefit if treated lt 4 days after pneumonia Dx

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Therapeutic Effect of Human Monoclonal Antibodies
to A/Vietnam/1203/04 in Mice

• Enhanced survival with treatment start delayed up
  to 72 hr post-infection.

Simmons et al. PLoS Med 4e178, 2007
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Potential Role of Combination Antiviral Therapy
in Influenza Treatment

• Combinations evaluated in animal models
• Amantadine interferon
• M2 inhibitors ribavirin
• M2 inhibitors oseltamivir
• Oseltamivir ribavirin
• Combinations evaluated in humans
• Oral rimantadine nebulized zanamivir
• Future considerations
• Dual NAIs
• Triple therapy M2 inhibitor ribavirin (or
  other transcriptase inhibitor) IFN-a or NAI
• Inclusion of other novel agents

Ong and Hayden. J Infect Dis 196181, 2007
Hayden FG. Antivir Res 71372, 2006
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CASG Trial of Nebulized Zanamivir Rimantadine
in Hospitalized Adults
CASG Collaborative Antiviral Study Group.
Ison et al. Antiviral Ther. 20038183-190.
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Survival of mice inoculated with rg VN-1203/04
Amantadine susceptible
Single-drug therapy
Combination therapy
AM 30 OS 10
AM 30
AM 15 OS 10
Survival distribution function
Survival distribution function
AM 15
OS 10
AS 1.5
Control
OS 1
Control
Days after inoculation
Days after inoculation
Ilyushina et al. Antiviral Therapy 12363, 2007
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• Comparison of monotherapy with i.p. zanamivir
  (ZNV), celecoxib, mesalazine, or gemfibrizol to
  triple regimen of ZNV celecoxib mesalazine
  in mice
• High inoculum of A/Vietnam/1194/04 (103 LD50)
• Therapy initiated at 48 hrs post-inoculation
• No survival benefit of early therapy (4 hrs) with
  single agents except ZNV

Zheng et al. PNAS, on line 6/2008
41
Antiviral Immunomodulator Therapy for H5N1 in
Mice

• ? survival with ZNV celecoxib mesalazine
• 2/8 surviving mice in triple therapy group had
  detectable titers at day 21.

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High throughput identification of host genes
important for influenza replication by Drosophila
RNAi screen
HEK293
COX6A1 cyt-c dep transport in
mitochondria--gtPB2 PB1-F2? ATP6V0D1 ATPase
subunit --gt endocytosis M2? NXF1 mRNA
exporter--gtexport unspliced mRNAs NS1?
Functional studies Steps of virus multiplication?
Contribution to host range?
Hao et al 2008 Nature
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Influenza Antivirals Future Directions

• Goal Rapid inhibition of influenza viral
  replication at all affected sites
• Near-term parenteral NAIs
• IV zanamivir or IV/IM peramivir
• Next antiviral combinations
• NAI plus M2 inhibitors, polymerase inhibitor
  (T-705 or ribavirin), or neutralizing antibodies
• Longer-term
• Antivirals with immunomodulators
• Host function-targeted agents

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Forthcoming Book from ASM Press

• Third edition
• Updates 2002 version
• Available first quarter 2009

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Back-up Slides
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• Pre-clinical assessment of arbidol toxicity and
  antiviral activity
• Ethyl-6-bromo-4-(dimethylamino)-methyl-5-hydroxy
  -1-methyl-2-(phenylthio)methyl-indole-3-carboxyl
  ate hydrochloride monohydrate
• Previous reports of activity for influenza,
  hepatitis B and C viruses

Shi et al. Arch Virol 1521447, 2007
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• Influenza testing by CPE inhibition in MDCK cells
• Arbidol causes overt cytotoxicity at gt16 ug/ml
• Broad spectrum narrow therapeutic index

Shi et al. Arch Virol 1521447, 2007
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In Vivo Activity of Arbidol

• Murine model of A/PR/8/34(H1N1)
• Drugs by oral gavage X 6 d starting 24 hr
  pre-virus
• Up to 3 log10 ? lung virus titers
• LD50 of 314 mg/kg/d for arbidol
• Narrow TI

Shi et al. Arch Virol 1521447, 2007
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• Kinetic analysis of NA (sialidase) activity
• Whole virus suspensions of isolates from 2007-8
  and prior seasons
• Vm (reflecting enzyme activity) similar in
  susceptible and resistant isolates from 2007-8
  but both 3X ? than in earlier H1N1 viruses
• Km (reflects substrate affinity) 2X ? in
  susceptible H1N1 from 2007-8 than earlier
  intermediate for oseltamivir-resistant isolates
  

Rameix-Welti et al. PLoS Pathogens 4e1000103,
2008
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Growth of H1N1 Viruses from 2007-8 in MDCK SIAT-1
Cells

• Replication of oseltamivir-resistant H1N1 (H274Y)
  isolates not impaired in vitro compared to
  susceptible H1N1 viruses from 2007-8 or earlier.

S
R
S
R
Rameix-Welti et al. PLoS Pathogens 4e1000103,
2008
51
NA Gene Phylogeny

• NA substitutions found in majority of H1N1 from
  2007-8 include 3 near catalytic site (222, 249,
  344).
• ? NA affinity for substrate and NAIs may have
  altered HA-NA balance to ? fitness ?

Rameix-Welti et al. PLoS Pathogens 4e1000103,
2008
52
Clinical Experience Suggests No Role for
Corticosteroids in A(H5N1) Treatment

• Vietnam

a Cao T, Liem NT. N Engl J Med 2008 358 261 b
Emerg Infect Dis 2005 11 201 N Engl J Med
2004 350 1179 N Engl J Med 2006 355 2186-94.
53
Convalescent Plasma Therapy in H5N1 Disease

• Case report of 31 yo male who presented with 4
  day Hx of fever, cough, and sputum
• CXR on day 6 showed LLL pneumonia
• Tracheal aspirate H5N1 by RT-PCR and culture
• Oseltamivir 150 mg bid started day 9 of illness
  but progressive bilateral pneumonia
• Convalescent plasma infusions from H5 survivor
  (200 ml X 3) on days 12-13
• Plasma neutralizing ab titer of 180
• Hospital discharge on day 30

Zhou et al. NEJM 3571450, 2007
54
Convalescent Plasma Therapy in H5N1 Disease

• Relative contributions of exogenous plasma,
  endogenous immune responses, and oseltamivir ?
• Zhou et al. NEJM 3571450, 2007

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• H5N1 hyperinduces COX-2 and proinflam-matory
  cytokine RNAs in macrophages but not type 2
  alveolar epi cells, compared to H1N1.
• COX-2 expressed in epithelial cells of autopsy
  lung tissue of H5N1 patients