425 1 a2066135z425.htm 425 Prepared by MERRILL CORPORATION
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MedImmune Contacts:
Lori Weiman
Senior Director, Corporate Communications
301-527-4321

Will Roberts
Manager, Investor Relations
301-527-4358

    On December 3, 2001, MedImmune announced that it has entered into a definitive merger agreement under which it will acquire Aviron through an exchange offer and merger transaction. Attached and incorporated herein by reference in its entirety as Exhibit 1 is a copy of a slide-show presentation given to investors by MedImmune to further explain the transaction.

    Filed by MedImmune, Inc.
Pursuant to Rule 425 under the Securities Act of 1933
Subject Company: Aviron
Commission File No. 000-20815

LOGO

Jennison Associates Presentation
December 2001


DISCLOSURE NOTICE:

    This presentation may contain, in addition to historical information, certain forward-looking statements that involve risks and uncertainties. Such statements reflect management's current views and are based on certain assumptions. Actual results could differ materially from those currently anticipated as a result of a number of factors, including risks and uncertainties discussed in MedImmune's and Aviron's filings with the SEC. MedImmune and Aviron are developing products for potential future marketing. There can be no assurance that such development efforts will succeed, that such products will receive required regulatory clearance or that, even if such regulatory clearance were received, such products would ultimately achieve commercial success. There can be no assurance that the offer and merger will close or that Aviron will be integrated successfully or without unanticipated costs.

    We urge Aviron stockholders and other investors to read the registration statement on Form S-4, Schedule TO, preliminary prospectus, supplements, final prospectus and other exchange offer documents which have been filed or will be filed by MedImmune with the Securities and Exchange Commission and the related solicitation/recommendation statement filed by Aviron with the SEC. These documents contain important information which should be read carefully before any decision is made with respect to the offer. Documents filed with the SEC are available for free at the SEC's website at www.sec.gov. Documents are available for free from MacKenzie Partners, Inc., 800-322-2885.


Agenda

    •
    MedImmune Overview

    •
    Aviron Acquisition

      — Transaction Details

      — Strategic Rationale

      — FluMist™ Opportunity

      — Aviron Pipeline Overview


MedImmune, Inc.

    •
    Founded 1988, IPO 1991; headquarters in Gaithersburg, MD

    •
    $10B market cap, S&P 500, S&P 100, NASDAQ 100

    •
    Profitable since "98; $1.1B in assets; $655M in cash; $204M in LTM operating cash flow (38% of revenues)

    •
    Three core marketed products; focused on infectious disease, immunology and oncology

    •
    Vertically integrated

      — 900 employees; 250-person R&D organization

      — Two manufacturing plants: MD & Netherlands

      — Three sales forces: hospital, pediatric & oncology

      — New headquarters/R&D facility early 2003

LOGO   Synagis®


LOGO

 

•  Humanized monoclonal antibody
    — Only MAb approved for infectious disease
•  Launched in U.S. September 1998
•  Prevention of serious lower respiratory tract disease caused by RSV in high risk infants
•  Approved in 46 countries; ABT ex-US distributor, co-promotes in U.S.
LOGO   Worldwide Synagis® Sales
Seasonal Comparison
(millions)

LOGO

LOGO   Ethyol®



LOGO


 


•  Cytoprotectant agent
    — Reduce cisplatin toxicities in ovarian and NSCLC (1996)
    — Prevent radiation induced xerostomia in H/N (1999)
•  MEDI regained U.S. marketing rights October '01
•  Schering-Plough ROW distributor
•  Current annualized worldwide sales $65M ($44M U.S.)


Strong R&D Pipeline

     LOGO


Aviron Acquisition


Transaction Details

    •
    $1.5B transaction value

    •
    $47.41 per AVIR share (28% premium) at 11/30/01

    •
    Stock-for-stock, tax free exchange offer

    •
    1.075 MEDI shares for each AVIR share

    •
    Equity ownership

      — 86% MEDI

      — 14% AVIR

    •
    Standard closing conditions

    •
    Anticipate closing 1Q '02


Strategic Rationale
Excellent Strategic Fit

    •
    Scientific and medical overlap

      — Infectious disease

      — Respiratory disease

      — Vaccine technology

      — Pediatrics

    •
    Leverages infrastructure and capabilities

      — Product development

      — Regulatory

      — Manufacturing/QA/QC

      — Marketing and sales


Strategic Rationale
Unique Ability to Assess and Execute

• R&D   Jim Young, PhD

• Clinical
 
Frank Top, MD
Ed Connor, MD

• Regulatory
 
Peter Patriarca, MD

• Mfg./QC/QA
 
Gail Wasserman, PhD
Ed Goley
Ben Machielse

• Marketing
 
Jeff Hackman


Strategic Rationale
Excellent Financial Fit

    •
    Dilutive in 2002

    •
    Neutral to cash EPS in 2003

    •
    Double digit accretion thereafter

    •
    Accelerates growth targets '03-'06

      — 25% annual revenue growth

      — 30% annual EPS growth


Strategic Rationale
Excellent Financial Fit

Financial Goals
   2002
   2003
   2006
Revenues   $900M   $1.1-$1.25B   >$2.1B
Cash EPS   $0.65-$0.70   $1.15-$1.20   >$2.50

2006 Operating Metrics (Goals)

    •
    77% to 80% gross margin

    •
    15% to 17% R&D

    •
    21% to 23% SG&A

    •
    Over 40% EBITDA and pre-tax margins


Strategic Rationale
Create Premier Biotech Company

    •
    Two blockbuster products

      — Synagis®

      — FluMist™

    •
    Rich pipeline

      — Antibodies and vaccines

      — Four in Phase 3, five in Phase 2

    •
    Proven ability to deliver

      — Product approvals

      — Manufacturing scale-up

      — Commercial success

      — Financial results


The FluMist Opportunity


Influenza

    •
    Most common cause of medically attended acute respiratory illness

    •
    Acute febrile illness (up to 104oF)

      — Chills, myalgia, cough, sore throat, nasal congestion, headache, malaise

    •
    High risk of mortality and other severe complications

      — Pneumonia and influenza—6th leading cause of death in the US


Impact of Influenza

    •
    Every Year in the U.S.

      — 25-50 Million People Infected

      — 20,000-50,000 Deaths

      — 70 Million Lost Work Days

      — 38 Million Lost School Days

      — Costs Nearly $15 Billion

Source: MMWR 2001
Source: American Lung Association, 3/01


Influenza-related Morbidity and Mortality

     LOGO

Glezen WP. Emerging infections: pandemic influenza. Epidemiol Rev. 1996; 18(1), 64-76.


Influenza

    •
    Vaccination is primary method for prevention

      —Annual vaccination

      — Inactivated vaccine

    •
    Three manufacturers

      —Aventis Pasteur

      — Medeva/Evans

      — American Home Products

    •
    80 million doses sold annually in U.S.

      —Growing at 10%

      — Price doubled to approximately $5 recently

      — Expected to reach $10 soon

    •
    Anticipate proprietary vaccine pricing for FluMist™

FluMist™
 
LOGO

Live   Active viral replication   X >20,000 vaccinated in ~20 studies

Attenuated
 
Mild Infection
 
X Positively viewed by pediatric community

Cold-adapted Temperature-sensitive
 
Replication restricted mainly to nasopharynx
 
X Anticipated by recommending bodies

Trivalent
 
A (H3N2, H1N1), B
 
X Significant public health impact

Dose = 0.5 ml (~107 TCID50)
0.25 ml into each nostril
 
 


Efficacy

Endpoint
   % Efficacy
   95% CI
Culture Confirmed Flu   91.7   87.7, 94.4

Febrile Illness
 
93.6
 
89.7, 96.0

Otitis Media
 
96.2
 
87.6, 98.8

Lower Respiratory Illness
 
95.2
 
62.2, 99.4
Endpoint
   % Reduction
   P-Value
Missed daycare/preschool/school days        
  Any Illness   12.8   0.07
  Culture Positive Illness   93.2   <0.001
Healthcare Provider Visits        
  Any Illness   11.2   0.02
  Culture Positive Illness   92.1   <0.001
Parental Lost Work        
  Any Illness   12.6   0.17
  Culture Positive Illness   93.0   <0.001


Frozen FluMist BLA
Under FDA Review

    •
    BLA Submission: October 31, 2000

      — 10 month PDUFA calendar

    •
    Pre-licensure inspections conducted 1H 2001

      — Clinical sites

      — Manufacturing sites

    •
    FDA advisory committee (VRBPAC): July 26-27, 2001


VRBPAC Efficacy Discussion

Question 1:   Are the data adequate to support the efficacy of FluMist?

 
 
Adults 18-64 years of age?
Yes 13-2

 
 
Children 1-17 years of age?
Yes 8-7

 
 
Children 2-17 years of age?
Yes 13-2

 
 
 


VRBPAC: Safety Discussion


Question 2:
 
Are the data adequate to support the safety of FluMist in the population in which an indication is being sought (i.e., 1-64 years)?

 
 
No 10-4

 
 
6 of 10 no votes were provisional
pending final FDA data analysis

 
 
Issues

 
 
•  Pneumonia

 
 
•  Asthma

 
 
•  Concurrent use

 
 
 


Pediatric Pneumonia

 
   FluMist
   Placebo
  
Study
  
  N
   Cases
   >21d
   N
   Cases
   >21d
  
AV006-Y1   1070   8   6   532   2   1  
AV006-Y2   917   2   1   441   0   0  
AV007   400   1   1   100   0   0  
AV0012-Y1   4298   2   1              
AV0012-Y2   5251   6   4              
AV0015   949   1   1              
AV0017   1175   3   3   70   0   0  
AV0019   6495   14   10   3238   10   6  
Total   20,555   37   27   4,381   12   7  
Percent       0.18 % 0.13 %     0.21 % 0.16 %


Asthma Episodes (All Doses)
AV019—Healthy Children

Age
   FluMist
n/N
   Placebo
n/N
   Rate per 1000
person-months
FluMist/Placebo
   p Value
1-17 years   58 / 6473   30 / 3216   4.6 / 4.8   p=0.422
1-8 years   45 / 3769   21 / 1868   5.1 / 4.8   p=0.418
18-36 months   16 / 728   2 / 369   9.3 / 2.3   p=0.019
12-17 months   1 / 171   3 / 90   2.5 / 14.4   p=0.067


Safety Database
(approximate number of participants)

 
   Pre-Aviron
Data Set
   Included in
BLA
   Included in
Safety Update
Healthy Children   2,600   6,000   18,000
Healthy Adults   4,600   3,700   4,000
High Risk   900   700   2,000
Total   8,100   10,400   24,000


Complete Response Letter

    •
    Complete response letter received 8/31/01

    •
    FDA requested additional information and clarification on clinical & manufacturing data

    •
    Response planned by December 31, 2001

    •
    FDA will re-start review clock (6 months)

    •
    Optimistic that available data will satisfy FDA


Potential Label

Indication   Prevention of influenza in healthy persons age 18mo - 64yrs

ClinPharm
 
93% Efficacy
37% ARROW flu-assoc. febrile otitis media Reduction in direct/indirect costs

Precautions/
warnings
 
Do not administer to persons with prior Hx wheezing; do not administer with other vaccines

Side Effects
 
Mild URI Sx in 20-50%
Significant fever 2-5%

Dosage/admin
 
0.5 cc intranasally (0.25 cc/nostril) 2 doses 30-60d apart for age <9yrs
LOGO   Conclusions

X Important medical advance

X New approach to immunization

X Data supports efficacy

X Draft clinical responses address major CR issues

X Primary issues that may affect timing and labeling

    •
    Concomitant immunization data

    •
    Wheezing/asthma

X Data support high likelihood of approval


FluMist™ Commercial Structure

    •
    AHP (Wyeth-Lederle Vaccines) alliance

      — U.S. co-promotion

      — AHP distributes Ex-U.S.

      — AHP records end-user sales

    •
    Aviron manufactures frozen FluMist

    •
    Aviron/AHP share manufacturing of liquid FluMist

    •
    AHP pays (reimburses) sales and marketing expenses

    •
    Co-funding of clinical development costs

    •
    Aviron receives approximately 50% of worldwide end-user sales and operating profit


R&D Programs

    •
    FluMist Enhancements

      —Liquid presentation

      —Sterile filtration for virus harvest

      —Reduced NAF

      —Plasmid rescue for development of MVS

      —Cell culture production

      —Mapping of mutations in MDV

    •
    Herpes Simplex Vaccine

    •
    Cytomegalovirus Vaccine

    •
    Parainfluenza Virus-3/bovine PIV-3 Vaccine Hybrid

    •
    RSV Vaccine/bovine PIV-3 Vaccine Hybrid


Aviron Acquisition

    •
    Excellent strategic fit

    •
    Excellent financial fit

    •
    Creates premier biotech company

      LOGO



QuickLinks

DISCLOSURE NOTICE
Agenda
MedImmune, Inc.
Strong R&D Pipeline
Aviron Acquisition
Transaction Details
Strategic Rationale Excellent Strategic Fit
Strategic Rationale Unique Ability to Assess and Execute
Strategic Rationale Excellent Financial Fit
Strategic Rationale Excellent Financial Fit
Strategic Rationale Create Premier Biotech Company
The FluMist Opportunity
Influenza
Impact of Influenza
Influenza-related Morbidity and Mortality
Influenza
Efficacy
Frozen FluMist BLA Under FDA Review
VRBPAC Efficacy Discussion
VRBPAC: Safety Discussion
Pediatric Pneumonia
Asthma Episodes (All Doses) AV019—Healthy Children
Safety Database (approximate number of participants)
Complete Response Letter
Potential Label
FluMist™ Commercial Structure
R&D Programs
Aviron Acquisition