Epidemic and Pandemic Use of Antivirals

Introduction

15 September 2008

Frederick G. Hayden, M.D.

University of Virginia Health System

Charlottesville, Virginia, USA

Antiviral Agents for Influenza

Class/agent Brand name Route

M2 inhibitors Amantadine Rimantadine

Symmetrel Flumadine

PO PO

NA inhibitors Zanamivir (GG167) Oseltamivir (GS4104) Peramivir (RWJ-270201)*

Relenza Tamiflu

Inhaled/IV*

PO IV*/IM*

Ribavirin

Virazole Inhaled*/PO*

/IV*

*Investigational

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

M2 Inhibitor Prophylaxis During Pandemic Influenza

Protective efficacy

Pandemic Influenza A illness

Seroconversion

1968 H3N2

1977 H1N1

59-100%

31-71%

28-52%

19-39%

Hayden. J Infect Dis 176:S56, 1997

Influenza Prevention In Households: PEP

Antiviral (Study)

No. Contacts

(age)

Reduction in 2° influenza illness

Reduction in influenza infection

Oseltamivir (Welliver et al, 2000)

955(13+ yr)

89% 49%

Oseltamivir* (Hayden et al, 2004)

792(1+ yr)

73% 35%(Index +)

Zanamivir* (Hayden et al, 2000)

837(5+ yr)

79% 62%

Zanamivir (Monto et al, 2002)

1,291(5+ yr)

82% 59%

*Index case given treatment

Antiviral Treatment of Acute Influenza

Outcome M2I ZNV OSEL

Symptom relief Yes Yes Yes

Complications reduction ? Yes Yes

Decrease antibiotic use ? 28% 24-40%

Decrease hospitalization ? ? ~50%

Treatment of viral complications

? ? Yes

Reduction in transmission ~30% No Yes

? = No placebo-controlled study or not reported

7

Oseltamivir Treatment Effects in A(H5N1) Infection

VirusSurvivors/

Treated (%)

Survivors/

Untreated (%)

P-value

Presumed clade 1

45/82 (55%) 6/26 (23%) 0.006

Presumed clade 2

43/106 (41%) 1/30 (3%) < 0.001

Total 88/188 (47%) 7/56 (12%) < 0.001

Adapted from Writing Committee of Second WHO Consultation on Human H5 Infections. N Engl J Med 358: 261, 2008

Resistance to M2 Inhibitors (S31N) in Community Isolates of A/H3N2, 2000-07

0

10

20

30

40

50

60

70

80

90

100

2000/1 2001/2 2002/3 2003/4 2004/5 2005/6 2006/7

China

Hong Kong

Australia

Japan

Europe

USA

%

Bright et al. Lancet 2005, JAMA 2006; Klimov et al. CDC unpublished; Barr et al. Antiviral Res 2006; R Saito, Niigata Univ, unpublished

Oseltamivir Resistance in H1N1 (H274Y)

• Rare in community H1N1 isolates, 1996-2007– 0 to <1% 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

Oseltamivir Resistance in H1N1 Viruses

+4Q07- 1Q08 *2Q08-20Aug08

http://www.who.int/csr/disease/influenza/h1n1_table/en/index.html; 20 Aug 08

Region Location No. isolates tested

% resistant

AMRO+ (17%)

Canada

USA

508

1026

26%

12%

EURO+

(25%)

France

Norway

496

265

47%

67%

WPRO+

(5%)

China/HK

Japan

666

1652

12%

3%

AFRO*

(85%)

South Africa*

Other*

107

20

100%

45%

Worldwide 4Q07- 1Q08

2Q08-20Aug08

7528

788

16%

31%

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

Do We Need New Anti-Influenza Agents?

• Antiviral resistance– Global spread of M2 inhibitor resistance in

H3N2 > 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 < 1 yr, pregnancy, hospitalized, IC hosts

• Lack of parenteral agents

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

Oseltamivir resistance (H274Y)

Amantadine resistance (L26F)

Van der vries et al. NEJM 359:1074, 2008

Re

-intu

ba

tion

Ex

tub

atio

n

Intu

ba

tion

Medical Needs for Anti-Influenza Antivirals

• Greater antiviral efficacy greater clinical benefit

• Safety and efficacy in special risk populations: infants < 1 yr, pregnancy, hospitalized, immuno-compromised

• Reliable drug delivery in seriously ill patients• Manage antiviral resistance • Combinations

Influenza Virus Replication and Sites for Antiviral Inhibition

De Clercq. Nature Reviews- Drug Discovery 5:1015, 2006

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

Investigational Agents in Clinical Development

Agent Target Sponsor Route Development phase

Zanamivir NA GSK IV Phase 1, 2a

Peramivir NA Biocryst IV, IM Phase 2

CS8958 NA Sankyo, Biota

Topical Phase 2

T-705 Polymerase Toyama Oral Phase 2

DAS181 HA receptor Nexbio Topical Phase 1

Neuraminidase Inhibitors

Peramivir

NA Inhibitor Resistance Profiles

NA mutation

NA type/ subtype

Susceptibility in the NAI assay (fold )

Oselt Zana Peram A-315675

E119V A/N2 R (>50->1000)

S (1) S (1) S (1-2)

R292K A/N2 R (>1000) S (4-25) R (40-80) S (8-13)

H274Y A/N1 R (>700) S (1) R (40-100) S (3)

R152K B R (>30-750)

R (10-100) R (>400) R (150)

Mishin et al. AAC 49:4516, 2005; Wetherall et al. AAC 41:742, 2003; Abed et al. Antiviral Res 77: 163, 2008

• 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

21

Pharmacokinetic Profiles of Intravenous and Intramuscular Peramivir

Kilpatrick JM, et al. Pharmacokinetics and Safety of Peramivir by Intramuscular Administration, Options for the Control of Influenza VI, Toronto, 2007

Intravenous Intramuscular

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

IM Peramivir: Time to Alleviation of Illness

J Alexander, BioCryst Pharmaceuticals, unpublished data

23

COMMERCIAL IN CONFIDENCE

Long Acting Neuraminidase Inhibitors (LANI)- 2 Strategies

O

NH

O

NHO

O

OH

NH

NH2

OHOH

O

NH

O

NH

O

NHO

O

OH

NH

NH2

OHOH

O

NH

X

OCH3(CH2)6

O

NH

O CO2H

NHNH

OH

NH2O

OMe

OH

NH

O CO2H

NHNH

OH

NH2O

OMe

CS-8958 FLUNET

DimerPreclinical

Pro-drugClinical

R-125489

Yamashita et al. 43rd ICAAC, Abstract no. F-1830, 2003

• Double-blinded trial found that inhaled CS-8958 administered once only was not statistically different than standard oseltamivir regimen.

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 > 1,000 µg/ml

• Triphosphate is inhibitor of influenza RNA polymerase.

• Active orally in murine models

N

NF

OH

CONH2

T-705

6-fluoro-3-hydroxy-2-pyrazinecarboxamide

Furuta et al. AAC 46:977, 2002; AAC 49:981, 2005

T-705: In Vitro Activity vs Ribavirin

Compound

IC50(μM) ± SD

(A PR/8/34 H1N1 influenza)

CC50(μM) ± SD

(MDCK cells)

T-705 1.0 ± 0.9 > 6,370

Ribavirin 31.6 ± 9.2 94.3 ± 47.6

Furuta Y, et al. Antimicrob Agents Chemother. 2005;49:981-986.

Effect of a T-705 Treatment in Mice Exposed to Lethal A/Duck/N/1525/81

(H5N1) Virus

Sidwell RW, et al. Antimicrob Agent Chemother. 2007;51:845-851.

0

20

40

60

80

100

4 12 24 48 60

Control T-705, 300 mg/kg T-705, 600 mg/kg

Delay before starting treatment following viral exposure, hours

Sur

viva

l (%

)

* *

* *

*

*

* *

*P < .01 relative to control

Pharmacokinetics of Oral T-705

• Bioavailability > 97% in mouse

• Rapid absorption in humans (Tmax < 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

0.001

0.01

0.1

1

10

100

0 3 6 9 12 15 18 21 24

Time after dose (hr)T-

705 P

lasm

a Con

cent

ratio

n (μ

g/mL)

30 mg (n=6)

90 mg (n=6)

200 mg (n=6)

400 mg (n=6)

800 mg (n=6)

1600 mg (n=6)

Single oral doses of T-705 over a range of 30 to 1600 mg

Toyama Chemical Co, unpublished

Molecular Model of DAS181 (Fludase®)

• Fusion construct with

catalytic domain of A.

viscosus sialidase and

an epithelium-

anchoring domain

(human amphiregulin)

– Active against both α2,6-

and α2,3-linked sialic

acid receptorsMalakhov et al. AAC 50:1470, 2006

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 50:1470, 2006

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 62:426, 2008

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 196:1439, 2007

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-α or NAI– Inclusion of other novel agents

Ong and Hayden. J Infect Dis 196:181, 2007; Hayden FG. Antivir Res 71:372, 2006

CASG* Trial of Nebulized Zanamivir + Rimantadine in Hospitalized Adults

Measure Zanamivir + Rimantadine

Rimantadine alone P value

No or mild cough, day 3

15/16 (94%) 11/20 (55%) .01

Days of hospitalization 4.7 ± 2.3 5.2 ± 2.3 .52

Frequency of rimantadine resistance

0 3 ND

Ison et al. Antiviral Ther. 2003;8:183-190.

*CASG = Collaborative Antiviral Study Group.

39

Survival of mice inoculated with rg VN-1203/04 –Survival of mice inoculated with rg VN-1203/04 –Amantadine susceptibleAmantadine susceptible

0

0.25

0.5

0.75

1

0 5 10 15 20

0

0.25

0.5

0.75

1

0 5 10 15 20

Days after inoculationDays after inoculation Days after inoculationDays after inoculation

Su

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ibu

tio

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un

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urv

iva

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trib

uti

on

fu

nct

ion

Su

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tio

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un

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trib

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fu

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ion

AM 30AM 30

AM 15AM 15

AS 1.5AS 1.5

OS 10OS 10

ControlControl ControlControlOS 1OS 1

AM 30 + OS 10AM 30 + OS 10

AM 15 + OS 10AM 15 + OS 10

Single-drug therapySingle-drug therapy Combination therapyCombination therapy

Ilyushina et al. Antiviral Therapy 12;363, 2007

• 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

survival with ZNV + celecoxib + mesalazine

• 2/8 surviving mice in triple therapy group had detectable titers at day 21.

Antiviral + Immunomodulator Therapy for H5N1 in Mice

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

44

Forthcoming Book from ASM Press

• Third edition• Updates 2002

version• Available first

quarter 2009

Back-up Slides

• Pre-clinical assessment of arbidol toxicity and antiviral activity– Ethyl-6-bromo-4-[(dimethylamino)-methyl]-5-

hydroxy-1-methyl-2-[(phenylthio)methyl]-indole-3-carboxylate hydrochloride monohydrate

– Previous reports of activity for influenza, hepatitis B and C viruses

Shi et al. Arch Virol 152:1447, 2007

• Influenza testing by CPE inhibition in MDCK cells

• Arbidol causes overt cytotoxicity at >16 ug/ml

• Broad spectrum; narrow therapeutic index

Shi et al. Arch Virol 152:1447, 2007

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 152:1447, 2007

• 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 4:e1000103, 2008

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

SR

R

Rameix-Welti et al. PLoS Pathogens 4:e1000103, 2008

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 4:e1000103, 2008

Clinical Experience Suggests No Role for Corticosteroids in A(H5N1) Treatment

•Vietnam Survival

Steroid Rx No steroids P-value

Hanoia 12/29 (41%) 29/38 (76%) 0.008

Published casesb

3/19 (16%) 10/15 (66%) 0.007

a Cao T, Liem NT. N Engl J Med 2008; 358: 261b Emerg Infect Dis 2005; 11: 201; N Engl J Med 2004; 350: 1179; N Engl J Med 2006; 355: 2186-94.

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 1:80

– Hospital discharge on day 30

Zhou et al. NEJM 357:1450, 2007

Convalescent Plasma Therapy in H5N1 Disease

• Relative contributions of exogenous plasma, endogenous immune responses, and oseltamivir ?

Zhou et al. NEJM 357:1450, 2007

• 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