**Exhibit99.1**

**MEDIMMUNE,INC.BOARD OF DIRECTORSCORPORATE GOVERNANCE GUIDELINES**

TheBoard of Directors (the “**Board**”)of MedImmune, Inc. (“**MedImmune**” orthe “**Company**”) has adopted theseCorporate Governance Guidelines (the “**Guidelines**”)to promote the effective functioning of the Board and its committees and tocontinue MedImmune’s commitment to maintaining the Company’s record of strongcorporate governance. These principles embrace high standards of integrity forthe conduct of the Company’s business in achieving its corporate goals whileserving the interest of the stockholders. These Guidelines were originallyadopted by the Board on November 11, 2004, and were revised on August 11, 2005and February 15, 2007, respectively.

# I. Introduction

                                                MedImmunebelieves that good corporate governance is important to ensure that the Companyis managed for the long-term benefit of its stockholders. These guidelinesprovide the framework for the governance of MedImmune, together with itsAmended and Restated Certificate of Incorporation, the By-Laws and the Chartersof the various Board committees (each of which is available on the Company’swebsite: www.medimmune.com.) The Board recognizes that there is anon-going, dynamic debate concerning corporate governance, and it will reviewthese principles and other aspects of MedImmune’s governance annually or moreoften if deemed necessary.

# II. Composition of the Board

1.                                       Sizeof Board.

                                                Thesize of the Board should facilitate substantive discussions in which eachDirector can participate meaningfully, encompass a broad range of skills,expertise, industry knowledge and diversity of opinion, and consist of amajority who, under the Marketplace Rules of the Nasdaq Global Market (the “**Nasdaq Rules**”), as adopted by the NationalAssociation of Securities Dealers, Inc., are deemed “independent directors” inthe business judgment of the Board. The Board believes it should generally haveno fewer than seven and no more than eleven members. The size of the Board maybe increased or decreased if determined to be appropriate by the Board.

2.                                       BoardMembership Criteria.

                                                TheBoard, through its Corporate Governance and Nominating Committee (the “**Governance Committee**”), utilizes a varietyof methods for identifying and evaluating potential nominees to the Board.Recommendations may come from current Board members, professional search firms,members of management, stockholders or other persons. In assessing thequalifications of potential nominees, the Governance Committee may rely onpersonal interviews or discussions with the candidate and others familiar withthe candidate’s professional background, third-party background and referencechecks and on such other due diligence information as is reasonably available.The Governance Committee must be satisfied that the candidate possesses thehighest professional and personal ethics and values and has broad experience atthe policy-making level in business, government, education or public interestbefore the Governance Committee would recommend a candidate as a nominee to theBoard.

3.                                       Electionof Directors.

                                                Eachdirector is elected each year at the Annual Meeting of Stockholders to servefor a one-year term expiring upon election of a successor at the next AnnualMeeting of Stockholders.

4.                                       IndependentDirectors.

                                                Amajority of the Board will be comprised of directors who satisfy theindependence requirements of the Nasdaq Rules. The Board will determineannually, based on all relevant facts and circumstances, whether each directorsatisfies the criteria for independence and it will disclose each of thesedeterminations in its public filings as required. Each independent directorshall notify the Chairman of the Governance Committee, as soon as practical, inthe event his or her circumstances change in a manner that may affect the Board’sevaluation of his or her independence.

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5.                                       LeadIndependent Director.

                                                Theindependent directors shall elect one director from among their membership asLead Independent Director. While the Lead Independent Director shall beappointed annually at the first meeting after the Board members are elected,the intent is for the Lead Independent Director to serve for a period of timewhich enables the Lead Independent Director to perform his or her functionswith continuity, i.e. generally three years. Responsibilities of the LeadIndependent Director shall include: leadership of executive sessions of theBoard, including setting the agenda for such executive sessions and briefingthe Chairman and the Chief Executive Officer on any issues arising out of thosesessions; working with the Chairman and Corporate Secretary to set the Boardagenda and determine the appropriate materials to be provided to the Board;consulting with other directors and advising the Chairman about the quality,quantity and timeliness of Board information and the Board’s decision makingprocesses; facilitating communication between the Board and management(although all independent directors are encouraged to freely communicate withthe Chairman, the Chief Executive Officer and other members of management atany time); retaining outside professionals on behalf of the Board as the Boardmay determine is necessary or appropriate; and performing such other functionsas the Board may direct.

6.                                       NewDirectors.

                                                TheGovernance Committee, with input from the Chairman and Chief Executive Officer,shall identify qualified individuals to become Board Members.  The Governance Committee shall makerecommendations to the full Board for approval. Stockholders may also recommendpotential candidates through the process identified below.

7.                                       StockOwnership by Directors.

                                                TheBoard believes that the number of shares of MedImmune’s stock owned by eachDirector is a personal decision but encourages MedImmune stock ownership bydirectors.

8.                                       DirectorCompensation.

                                                Directorcompensation and stock ownership are periodically reviewed by the GovernanceCommittee, usually on an annual basis. The Governance Committee’s reviewincludes a comparison of MedImmune’s director compensation practices againstthe practices of other pharmaceutical and biotechnology companies. TheGovernance Committee’s objectives include ensuring that the Company’snon-management Directors have a proprietary stake in the Company and that theinterests of the Directors continue to be closely aligned with the interests ofthe Company’s stockholders. Board members who are also employees of MedImmunewill not be separately compensated for service on the Board.

9.                                       TermLimits.

                                                TheBoard does not favor term limits for Directors, but believes that it isimportant to monitor overall Board performance.

10.                                 RetirementPolicy.

                                                TheBoard does not believe that there should be a mandatory retirement age forDirectors. The Board believes that age should not be a barrier to service ofany Director maintaining the interest, commitment and ability to serve on theBoard and that each Board member should be evaluated based on his or herabilities and contributions to the Board.

11.                                 MajorityVoting Resignation Policy.

                                                (a)Policy. In an uncontested election of directors (i.e., an election wherethe only nominees are those recommended by the Board), any nominee for directorwho receives a greater number of votes “withheld” from his or her election thanvotes “for” his or her election (a “**WithheldDirector**”) will promptly tender his or her resignation to theGovernance Committee following certification of the stockholder vote.

                                                (b)Procedures.

                                                (i)The Governance Committee will promptly consider the resignation submitted by aWithheld Director, and the Governance Committee will recommend to the Boardwhether to accept the tendered resignation or reject it. In considering whetherto accept or reject the tendered resignation, the Governance Committee willconsider all factors deemed relevant by the members of the Governance Committeeincluding, without limitation, the reasons that the Governance Committeebelieves are the reasons stockholders “withheld” votes for election from theWithheld Director, the length of service and qualifications of the WithheldDirector, the Withheld Director’s contributions to the Company, and the Company’sCorporate Governance Guidelines.

                                                (ii)The Board will act on the Governance Committee’s recommendation no later than90 days following the date of the stockholders’ meeting where the electionoccurred. In considering the Governance Committee’s recommendation, the Boardwill consider the factors considered by the Governance Committee and suchadditional information and factors the Board believes to be relevant. Followingthe Board’s decision on the Governance Committee’s recommendation, the Companywill promptly publicly disclose the decision of the Board whether to accept theresignation as tendered (providing a full explanation of the process by whichthe decision was reached and, if applicable, the reasons for rejecting thetendered resignation) in a Current Report filed with the Securities andExchange Commission.

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                                                (iii)To the extent that one or more Withheld Directors’ resignations are accepted bythe Board, the Governance Committee will recommend to the Board whether to fillsuch vacancy or vacancies or to reduce the size of the Board.

                                                (iv)Any director who tenders his or her resignation pursuant to this provision willnot participate in the Governance Committee’s recommendation or the Board’sconsideration regarding whether or not to accept the tendered resignation, orin deliberations by either the Governance Committee or the Board with respectto such matter. If the members of the Governance Committee who are alsoWithheld Directors at the same election constitute a majority of the GovernanceCommittee, then the Board will appoint a Board committee solely for the purposeof considering the tendered resignations and recommending to the Board whetherto accept or reject them, *provided that*WithheldDirectors and non-independent members of the Board shall abstain from voting inthis matter. This Board committee may, but need not, consist of all of theindependent directors who are not Withheld Directors.

                                                (v)This policy will be summarized or included in each proxy statement relating toan election of directors of the Company.

12.                                 ResignationPolicy — Change of Principal Position.

                                                Ifa Board member’s principal occupation or business association changes substantially(including retirement) following the Director’s initial election, the Directormust immediately offer his or her resignation to the Board. The Board willdetermine, by majority vote of members present at a duly-constituted meeting,whether to accept the offer of resignation. The Board may delegate responsibility for evaluating any resignationsubmitted under this Section 12 to the Governance Committee.

13.                                 Serviceon Other Public Company Boards.

                                                Directorsare expected to dedicate sufficient time and energy to performing their Boardduties.  Accordingly, absent extenuatingcircumstances reviewed and approved in advance by the Governance Committee,Directors should not serve on more than five other boards of directors ofpublicly listed companies, in addition to the Company’s Board. Service onboards of private companies, charitable or educational boards does not counttowards this limit, however the Governance Committee should evaluate theobligations and responsibilities reported by each Director as a whole toconfirm that such Director has sufficient time to dedicate to the Company.

# III. Conduct and Board Meetings

1.                                       Rolesof Board and Management.

                                                TheBoard, which is elected by the stockholders, is the ultimate decision makingbody of the Company, except for those matters reserved to the stockholders. Itselects the senior management team, which is charged with the conduct of theCompany’s business. Having selected the senior management team, the Board actsas advisor and counselor to senior management and ultimately monitorsperformance. The Board also plans for succession of the Chairman of the Boardas well as the Chief Executive Officer and certain other senior managementpositions. The Board provides oversight with respect to the strategic directionand key policies of the Company, approves major initiatives, advises on keyfinancial and business objectives, and monitors progress with respect to thesematters. In addition, the Board, directly and through its Audit Committee,provides oversight of the integrity of the financial statements of the Company;the independent accountant’s qualifications and independence; the performanceof the Company’s internal audit function and independent accountant; and thecompliance by the Company with legal requirements relating to financialdisclosure.

2.                                       BoardMeetings.

                                                TheBoard currently plans at least four regular meetings each year, with furthermeetings to occur (or action to be taken by unanimous written consent), at thediscretion of the Board. The schedule and length of the board meetings isdesigned to allow sufficient time for in-depth discussions, analysis andstrategic planning, as well as to encourage interactions between directors andMedImmune’s management.  The Chairman ofthe Board and the Chief Executive Officer, working with the Lead IndependentDirector, set the agenda for Board meetings with the understanding that certaintopic matters pertinent to the advisory and monitoring function of the Board bebrought to it periodically for review and/or decision. Any member of the Boardmay request a topic item be included on the agenda.

3.                                       Attendanceat Board Meetings.

                                                Alldirectors should make every effort to attend every meeting of the Board andevery meeting of committees of which they are members. Directors are expectedto attend the Annual Meeting of Stockholders.

4.                                       Distributionof Materials.

                                                TheBoard is provided, in advance of meetings, with agendas and written backgroundinformation and data with respect to the Board or committee agenda items, aswell as other general information relevant to the Company’s businesses. TheBoard also is provided with information between meetings and has access tomanagement and outside advisors on an as-needed basis.

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5.                                       Attendanceof Non-Directors.

                                                TheBoard encourages the Chief Executive Officer to bring members of managementinto Board meetings to (i) provide management insight into items beingdiscussed by the Board which involve the managers; (ii) make presentations tothe Board on matters which involve the managers; and (iii) bring managers withsignificant potential into contact with the Board. Attendance of managementpersonnel at Board meetings is at the discretion of the Board.

6.                                       ExecutiveSessions.

                                                Toensure free and open discussion and communication among the independentdirectors of the Board, independent directors will meet at least four times ayear in executive sessions, with no members of management present. The LeadIndependent Director will preside at the executive sessions.

7.                                       AssessingBoard Performance.

                                                TheGovernance Committee will lead the process of having an assessment of Boardeffectiveness performed on a regular basis. The Board will utilize the resultsof this self-evaluation process in assessing and determining the characteristicsand critical skills required of prospective candidates for election to theBoard as well as the appointment of Board members to committees.

8.                                       Accessto Officers and Employees.

                                                Boardmembers have complete and open access to MedImmune’s management and outsideadvisors. Board member contact with such individuals shall be handled in amanner that would not be disruptive to the business operations of MedImmune.

9.                                       Authorityto Retain Independent Advisors.

                                                TheBoard and each committee have the power to hire independent legal, financial orother advisors as they may deem appropriate, without consulting or obtainingthe approval of any officer of MedImmune in advance. MedImmune shall pay thefees and expenses of any such advisors.

10.                                 StockholderNominations.

                                                Stockholdersmay propose Director nominees for consideration by the Governance Committee bysubmitting names and supporting information to:

                                                Boardof Directorsc/o the Corporate SecretaryMedImmune, Inc.One MedImmune WayGaithersburg, Maryland 20878

                                                Thesupporting information provided to the Corporate Secretary should include thefollowing: (a) a statement that the proposer is a stockholder; (b) the name andcontact information of the candidate; (c) a resume of the candidate’seducational and professional experience and list of references; (d) a statementsetting forth any relationship between the candidate and any customer,supplier, competitor, employee or director of MedImmune or between thecandidate and the proposer; and (e) a signed consent of the candidate tobackground reference checks as part of the evaluation process, to be named in aproxy statement (if determined advisable by the Governance Committee) and toserving on the Board if nominated and elected. The Governance Committee shall give appropriate consideration tocandidates for Board membership proposed by stockholders. It shall evaluatesuch candidates in the same manner as other candidates identified to theGovernance Committee.

11.                                 Communicationwith the Board.

                                                Aspart of its corporate governance oversight, the Governance Committee hasestablished a mechanism by which stockholders may communicate with the Board.Stockholders may do so by writing to:

                                                Boardof Directorsc/o the Corporate SecretaryMedImmune, Inc.One MedImmune WayGaithersburg, Maryland 20878

12.                                 Ethicsand Conflict of Interest.

                                                TheBoard expects its Directors, Officers and other employees to act ethically atall times and to acknowledge adherence to the Company’s Global Standards ofBusiness Conduct and Ethics (the “**Code ofConduct**”). Any waiver of the Code of Conduct for Directors andExecutive Officers may be made only by the Board and must be promptly disclosedto stockholders. Directors are expected to avoid any actions or interests thatconflict with an interest of the Company, or that gives the appearance of aconflict. If any actual or potential conflict of interest arises for aDirector, the Director shall promptly inform the Chief Executive Officer andthe Chair of the Governance Committee.

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13.                                 ContinuingDirector Education.

                                                Newlyappointed Board members will receive orientation about the history ofMedImmune, its business and financial operations and expectations of the Board.Members of the Board will be provided continuing education including, but notlimited to, critical issues affecting MedImmune and its industry overall,director’s roles and responsibilities and applicable legal standards.

                                                TheCompany strongly encourages all Board members to attend continuing Directorprograms focused on good corporate governance practices, developments oncompliance issues and others areas that will assist the Directors in fulfillingtheir fiduciary obligations to the Company and its stockholders. The Companywill pay the reasonable expenses for any Board member who wishes to attendaccredited third party training programs focused on the aforementioned areas.

# IV. Committees ofthe Board

1.                                       BoardCommittees.

                                                TheBoard will have at all times an Audit Committee, a Compensation and StockCommittee and a Corporate Governance and Nominating Committee. Each of thesecommittees will consist solely of independent directors satisfying applicablelegal, regulatory and stock market requirements and will adopt a charteroutlining the responsibilities of such committee. Committee members will beappointed by the Board upon recommendations of the Governance Committee. TheBoard may, from to time to time, establish or maintain additional committees asit deems necessary or appropriate, and as of the time of the adoption of theseGuidelines the Company also has the following committees: compliance;executive; and investment. Each of these committees shall adopt a Charteroutlining the responsibilities of such committee. (All committee charters areavailable on the Company’s website*:www.medimmune.com*.)  The Boardelects the members and Chair of each committee, attempting to match thecommittee’s function and needs to individual skills and experience of theDirector for the committee.

2.                                       Frequencyand Length of Committee Meetings.

                                                Thenumber and content of committee meetings and other matters of committeegovernance are determined by each committee and its Chair in light of theresponsibilities delegated by the Board. Appropriate agenda items arerecommended by management, in consultation with the committee Chair and thecommittee members. Any Director, however, may recommend inclusion of specificagenda items for any committee meeting, regardless of whether the Director is amember of such committee. The roles of the committees are defined by theCompany’s By-Laws and by Committee Charters adopted by the Board.

3.                                       Rotationof Committee Assignments and Chairs.

                                                Committeeassignments and the designation of Committee Chairs should be based on eachDirector’s knowledge, interests and areas of expertise. The Board does notfavor mandatory rotation of committee assignments or Chairs. The Board believesexperience and continuity are more important than rotation. Committee membersand Chairs may be rotated in response to changes in the membership of the Boardand in all cases should be rotated only if rotation is likely to increasecommittee performance.

# V. Chief Executive Officer Evaluation

1.                                       ChiefExecutive Officer Performance Review.

                                                TheCompensation & Stock Committee (the “**CompensationCommittee**”) assists the Board in fulfilling the Board’s oversightresponsibilities relating to compensation of the Company’s executives, whichshall include the establishment of executive compensation policies andpractices of the Company and the adoption and administration of executivecompensation plans and programs. The Compensation Committee reviews thecompensation plans and programs of the Company and its subsidiaries, and shallmake recommendations to the Board with respect thereto. In addition, theCompensation Committee reviews and evaluates, subject to oversight by theBoard, the Chief Executive Officer’s performance.

2.                                       SuccessionPlan.

                                                TheGovernance Committee will prepare and evaluate from time to time forconsideration by the Board a plan for management succession. The Board willreview and approve succession plans for the Chief Executive Officer and othersenior executives. Succession planning will address both succession in theordinary course and contingency planning in the case of unexpected events.

# VI. Policy RegardingRelated Party Transactions

1.                                       Introductionand Definitions.

                                                TheBoard of recognizes that related person transactions present a heightened riskof conflicts of interest and/or improper valuation, or the perception thereof,and therefore has adopted this policy which shall be followed in connectionwith all related person transactions involving the Company.

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                                                Forpurposes of this policy:

                                                (a)a “**Related Person**” is:

                                                i.              each Section 16 officer (asdesignated by the Board from time to time), all other senior vice presidentsand all members (including nominees) of the Board;

                                                ii.             a stockholder owning in excess offive percent of the Company (or its controlled affiliates);

                                                iii.            a person who is an immediate familymember of any of the persons identified in 1 or 2 above (an “immediate familymember” shall mean the spouse, parents or stepparents, children orstepchildren, siblings, mothers-in-law or fathers-in-law, brothers-in-law orsisters-in-law, sons-in-law or daughters-in-law, and/or anyone (otherthan tenants or employees) sharing the household of a person identified in 1 or2 above; and

                                                iv.            an entity which is owned orcontrolled by someone listed in 1, 2 or 3 above, or an entity in which someonelisted in 1, 2 or 3 above has a substantial ownership interest or control ofsuch entity.

                                                (b)a “**Related Person Transaction**” isa transaction in which the Company was, is or will be a participant and inwhich any Related Person had, has or will have a direct or indirect interest(including any transactions requiring disclosure under Item 404 of RegulationS-K under the Securities Exchange Act of 1934), other than:

                                                i.              transactions available to allemployees generally and without discrimination; and

                                                ii.             transactions involving less than$10,000, when aggregated with all similar transactions.

2.                                       ApprovalRequired.

                                                (a)Under this policy, any related party transaction (other than the Related PartyTransactions as defined in 1(b) above) proposed to be entered into by anyemployee or consultant who is not a Related Person as defined in 1(a) above,shall only be consummated upon approval of such proposed transaction by therelevant senior vice president or higher level executive to whom the employeeor consultant directly or indirectly reports to. Transactions that (i) areavailable to all employees generally and without discrimination, (ii) arecompensation related as approved by the Company’s management, and (iii) involveless than $10,000, when aggregated with all similar transactions, are exemptfrom this approval requirement.

                                                (b)Under this policy, any Related Person Transaction shall be consummated or shallcontinue only if: (i) the Audit Committee of the Board approves or ratifiessuch transaction in accordance with the guidelines set forth in this policy andif the transaction is on terms comparable to those that could be obtained inarm’s length dealings with an unrelated third party; (ii) the transaction isapproved by the disinterested and independent members of the Board; or (iii)the transaction relates to a compensation approved by the CompensationCommittee of the Board.

3.                                       AuditCommittee Approval.

                                                TheBoard has determined that the Audit Committee is best suited to review andapprove Related Person Transactions. Accordingly, at each calendar year’s last regularly scheduled AuditCommittee meeting, management shall recommend Related Person Transactions to beentered into by the Company, including the proposed aggregate value of suchtransactions, if applicable. After review, the Audit Committee shall approve ordisapprove such transactions and at each subsequently scheduled meeting,management shall update the Committee on any material change to those proposedtransactions.

                                                Inthe event management recommends any further Related Person Transactionssubsequent to the last calendar year Audit Committee meeting, such transactionsmay be presented to the Audit Committee for approval or preliminarily enteredinto by management subject to ratification by the Audit Committee; *provided* that if ratification does notoccur, management shall make all reasonable efforts to cancel or annul thetransaction.

4.                                       CorporateOpportunity.

                                                TheBoard recognizes that situations exist where a significant opportunity may bepresented to management, employees or a member of the Board that may equally beavailable to the Company, either directly or via referral.  Before such opportunity may be consummated byan employee or a Related Person (other than an otherwise unaffiliated 5%stockholder), such opportunity shall be presented to the Board forconsideration.

5.                                       Disclosure.

                                                AllRelated Person Transactions shall be disclosed in the Company’s applicablefilings as required by the Securities Act of 1933 and the Securities ExchangeAct of 1934 and related rules. Furthermore, all Related Person Transactionsshall be disclosed to the Audit Committee and any material Related PersonTransaction shall be disclosed to the full Board.

6.                                       MedImmuneVentures, Inc.

                                                TheBoard believes that, absent extenuating circumstances, an investment made bythe Company’s venture subsidiary, MedImmune Ventures, Inc., in portfoliocompanies in which an affiliate of a Related Person has also co-invested in,does not constitute a Related Party Transaction; *provided*, *that*,the Related Person does not have or exercise sole investment control in theinvestment. The board of directors of MedImmune Ventures, Inc. is herebyempowered to evaluate and determine the appropriateness of transactions thatmay be exceptions to the general principle stipulated in this sub-Section 6.

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7.                                       OtherAgreements.

                                                Managementshall assure that all Related Person Transactions are approved in accordancewith any requirements of the Company’s financing agreements.

# VII. Global Standard of Business Conduct and Ethics

The Company’s Code of Conduct is applicable to alldirectors, officers and employees of the Company, including the principalexecutive officer, principal financial officer and principal accountingofficer. The global standards stipulated in the Code of Conduct meet the criteriafor a “Code of Ethics” under the rules of the Securities and ExchangeCommission and a “Code of Conduct” under the Nasdaq Rules. The Code of Conductis available on the Company’s website (www.medimmune.com).

 

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