RIGHTS AGREEMENT dated as of May 16, 2012 between HUMAN GENOME SCIENCES, INC. and AMERICAN STOCK TRANSFER & TRUST COMPANY, LLC as Rights Agent

Exhibit 4.1

RIGHTS AGREEMENT

dated as of

May 16, 2012

between

HUMAN GENOME SCIENCES, INC.

and

AMERICAN STOCK TRANSFER & TRUST COMPANY, LLC

as Rights Agent

Table of Contents


		Page
ARTICLE I DEFINITIONS			1
1.1	Definitions		1
ARTICLE II THE RIGHTS			7
2.1	Summary of Rights		7
2.2	Legend on Common Stock Certificates		7
2.3	Exercise of Rights; Separation of Rights		8
2.4	Adjustments to Exercise Price; Number of Rights		10
2.5	Date on Which Exercise is Effective		12
2.6	Execution, Authentication, Delivery and Dating of Rights Certificates		12
2.7	Registration of Transfer and Exchange		12
2.8	Mutilated, Destroyed, Lost and Stolen Rights Certificates		13
2.9	Persons Deemed Owners		14
2.10	Delivery and Cancellation of Certificates		14
2.11	Agreement of Rights Holders		14
ARTICLE III ADJUSTMENTS TO THE RIGHTS IN THE EVENT OF CERTAIN TRANSACTIONS			15
3.1	Flip-in		15
3.2	Flip-over		18
ARTICLE IV THE RIGHTS AGENT			19
4.1	General		19
4.2	Merger or Consolidation or Change of Name of Rights Agent		20
4.3	Duties of Rights Agent		21
4.4	Change of Rights Agent		22
ARTICLE V MISCELLANEOUS			23
5.1	Redemption		23
5.2	Expiration		24
5.3	Issuance of New Rights Certificates		24
5.4	Supplements and Amendments		24
5.5	Fractional Shares		25
5.6	Rights of Action		25
5.7	Holder of Rights Not Deemed a Stockholder		26
5.8	Notice of Proposed Actions		26
5.9	Notices		26
5.10	Suspension of Exercisability or Exchangeability		27
5.11	Costs of Enforcement		27
5.12	Successors		28
5.13	Benefits of this Agreement		28
5.14	Determination and Actions by the Board of Directors, etc.		28
5.15	Descriptive Headings		28
5.16	Governing Law		28
5.17	Counterparts		29
5.18	Severability		29

Exhibits


Exhibit A		Form of Rights Certificate (together with Form of Election to Exercise)
Exhibit B		Form of Certificate of Designation

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RIGHTS AGREEMENT

RIGHTS AGREEMENT (as amended from time to time, this “Agreement”), dated as of May 16, 2012 between Human Genome Sciences, Inc., a Delaware corporation (the “Company”), and American Stock Transfer & Trust Company, LLC, a New York limited liability trust company, as Rights Agent (the “Rights Agent,” which term shall include any successor Rights Agent hereunder).

WITNESSETH:

WHEREAS, on May 16, 2012 (the “Rights Dividend Declaration Date”), the Board of Directors of the Company (a) authorized and declared a dividend of one right (“Right”) in respect of each share of Common Stock (as hereinafter defined) outstanding as of the close of business on May 29, 2012 (the “Record Time”) and (b) authorized the issuance of one Right in respect of each share of Common Stock issued after the Record Time and prior to the Separation Time (as hereinafter defined) and, to the extent provided in Section 5.3, each share of Common Stock issued after the Separation Time;

WHEREAS, subject to the terms and conditions hereof, each Right entitles the holder thereof, after the Separation Time, to purchase securities or assets of the Company (or, in certain cases, securities of certain other entities) pursuant to the terms and subject to the conditions set forth herein; and

WHEREAS, the Company desires to appoint the Rights Agent to act on behalf of the Company, and the Rights Agent is willing so to act, in connection with the issuance, transfer, exchange and replacement of Rights Certificates (as hereinafter defined), the exercise of Rights and other matters referred to herein;

NOW THEREFORE, in consideration of the premises and the respective agreements set forth herein, the parties hereby agree as follows:

ARTICLE I

DEFINITIONS

1.1 Definitions.

For purposes of this Agreement, the following terms have the meanings indicated:

“Acquiring Person” shall mean any Person who is a Beneficial Owner of 15% or more of the outstanding shares of Common Stock without the prior approval of the Board of Directors; provided, however, that the term “Acquiring Person” shall not include any Person (i) who shall become the Beneficial Owner of 15% or more of the outstanding shares of Common Stock solely as a result of an acquisition by the Company of shares of Common Stock, which by reducing the number of shares of Common Stock outstanding, increases the proportionate percentage of Common Stock Beneficially Owned by such Person, until such time as such Person, after becoming aware that such Person has become the Beneficial Owner of 15% or more of the outstanding shares of Common Stock, shall become the Beneficial Owner of additional shares of

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Common Stock representing 1% or more of the shares of Common Stock then outstanding or (ii) who has reported or is required to report such ownership (but less than 20%) on Schedule 13G under the Exchange Act (or any comparable or successor report) or on Schedule 13D under the Exchange Act (or any comparable or successor report) which Schedule 13D does not state any intention to or reserve the right to control or influence the management or policies of the Company or engage in any of the actions specified in Item 4 of such schedule (other than the disposition of the Common Stock). In addition, the Company, any Subsidiary of the Company and any employee stock ownership or other employee benefit plan of the Company or a Subsidiary of the Company shall not be an Acquiring Person. The Board shall not be required to make any determination with respect to a potential Acquiring Person until five (5) Business Days after the date on which all Board members first received notice of the change of Beneficial Ownership at issue.

“Affiliate” and “Associate” shall have the respective meanings ascribed to such terms in Rule 12b-2 under the Exchange Act.

“Agreement” shall have the meaning set forth in the preamble.

A Person shall be deemed the “Beneficial Owner,” and to have “Beneficial Ownership” of, and to “Beneficially Own,”

(i) any securities of which such Person or any of such Person’s Affiliates or Associates is or may be deemed to be the beneficial owner pursuant to Rule 13d-3 and 13d-5 under the Exchange Act;

(ii) any securities as to which such Person or any of such Person’s Affiliates or Associates has the right to become beneficial owner (whether such right is exercisable immediately or only after the passage of time or the occurrence of conditions) pursuant to any agreement, arrangement or understanding (other than customary agreements with and between underwriters and selling group members with respect to a bona fide public offering of securities), or upon the exercise of conversion rights, exchange rights, rights (other than the Rights), warrants or options, or otherwise;

(iii) any securities that such Person or any of such Person’s Affiliates or Associates are determined to Constructively Own;

provided, however, that a Person shall not be deemed the “Beneficial Owner,” or to have “Beneficial Ownership” of, or to “Beneficially Own,” any security (A) solely because such security has been tendered pursuant to a tender or exchange offer made by such Person or any of such Person’s Affiliates or Associates until such tendered security is accepted for payment or exchange, (B) solely because such Person or any of such Person’s Affiliates or Associates has or shares the power to vote or direct the voting of such security pursuant to a revocable proxy or consent given in response to a public proxy or consent solicitation made to more than ten holders of shares of a class of stock of the Company registered under Section 12 of the Exchange Act and pursuant to, and in accordance with, the applicable rules and regulations under the Exchange Act,

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except if such power (or the arrangements relating thereto) is then reportable under Item 6 of Schedule 13D under the Exchange Act (or any similar provision of a comparable or successor report), (C) issuable upon exercise of Rights at any time prior to the occurrence of a Flip-over Transaction or Event or the Flip-in Date, or (D) issuable upon exercise of Rights from and after the occurrence of a Flip-over Transaction or Event or the Flip-in Date, which Rights were acquired by such Person or any of such Person’s Affiliates or Associates prior to the Separation Time or pursuant to Section 2.3(b) or Section 5.3 hereof (the “Original Rights”) or pursuant to Section 2.4 hereof in connection with an adjustment made with respect to any Original Rights. Notwithstanding the foregoing, no officer or director of the Company shall be deemed to Beneficially Own any securities of any other Person by virtue of any actions such officer or director takes in such capacity. For purposes of this Agreement, in determining the percentage of the outstanding shares of Common Stock with respect to which a Person is the Beneficial Owner, all shares as to which such Person is deemed the Beneficial Owner shall be deemed outstanding.

“Book Entry” shall mean an uncertificated book entry for the Common Stock.

“Business Day” shall mean any day other than a Saturday, Sunday or a day on which banking institutions in the City of New York are generally authorized or obligated by law or executive order to close.

“Close of Business” on any given date shall mean 5:00 p.m. New York City time on such date or, if such date is not a Business Day, 5:00 p.m. New York City time on the next succeeding Business Day.

“Common Stock” shall mean the shares of Common Stock, par value $0.01 per share, of the Company.

“Company” shall have the meaning set forth in the preamble.

A Person shall be deemed to “Constructively Own” shares of Common Stock in respect of which such Person has a Synthetic Long Position, calculated in the manner set forth below. The number of shares of Common Stock in respect of a Synthetic Long Position that shall be deemed to be Constructively Owned is the notional or other number of shares of Common Stock in respect of such Synthetic Long Position that is specified in a filing by such Person or any of such Person’s Affiliates or Associates with the Securities and Exchange Commission or in the documentation evidencing such Synthetic Long Position as the basis upon which the value or settlement amount of such right or derivative, or the opportunity of the holder of such right or derivative to profit or share in any profit, is to be calculated in whole or in part, and in any case (or if no such number of shares of Common Stock is specified in any filing or documentation), as determined by the Board of Directors of the Company in good faith to be the number of shares of Common Stock to which such Synthetic Long Position relates.

“Election to Exercise” shall have the meaning set forth in Section 2.3(d).

“Exchange Act” shall mean the Securities Exchange Act of 1934, as amended.

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“Exchange Ratio” shall have the meaning set forth in Section 3.1(c) hereof.

“Exchange Time” shall mean the time at which the right to exercise the Rights shall terminate pursuant to Section 3.1(c) hereof.

“Exercise Price” shall mean, as of any date, the price at which a holder may purchase the securities issuable upon exercise of one whole Right. Until adjustment thereof in accordance with the terms hereof, the Exercise Price shall equal $37.50.

“Expansion Factor” shall have the meaning set forth in Section 2.4(a) hereof.

“Expiration Time” shall mean the earliest of (i) the Exchange Time, (ii) the Redemption Time and (iii) the close of business on the twelve-month anniversary of the Record Time.

“Flip-in Date” shall mean the Business Day after any Stock Acquisition Date or such earlier or later date as the Board of Directors of the Company may from time to time fix by resolution adopted prior to the Flip-in Date that would otherwise have occurred.

“Flip-over Entity,” for purposes of Section 3.2, shall mean (i) in the case of a Flip-over Transaction or Event described in clause (i) of the definition thereof, the Person issuing any securities into which shares of Common Stock are being converted or exchanged and, if no such securities are being issued, the other party to such Flip-over Transaction or Event and (ii) in the case of a Flip-over Transaction or Event referred to in clause (ii) of the definition thereof, the Person receiving the greatest portion of the (A) assets or (B) operating income or cash flow being transferred in such Flip-over Transaction or Event, provided in all cases if the common stock of such Person is not at such time and has not been continuously over the preceding twelve-month period registered under Section 12 of the Exchange Act, and such Person is a direct or indirect Subsidiary of another Person the common stock of which is and has been so registered, then such other Person shall be the Flip-over Entity.

“Flip-over Stock” shall mean the validly authorized and issued, fully paid, non-assessable and freely tradeable shares of capital stock (or similar equity interest) with the greatest voting power in respect of the election of directors (or other persons similarly responsible for direction of the business and affairs) of the Flip-over Entity, which Flip-over Stock shall not be subject to any liens, encumbrances, rights of first refusal or other adverse claims.

“Flip-over Transaction or Event” shall mean a transaction or series of transactions after the Stock Acquisition Date in which, directly or indirectly, (i) the Company shall consolidate with, or merge with and into, any other Person (other than a Subsidiary of the Company in a transaction that complies with Section 3.1(f) hereof), and the Company shall not be the continuing or surviving corporation of such consolidation or merger, (ii) any Person (other than a Subsidiary of the Company in a transaction that complies with Section 3.1(f) hereof) shall consolidate with, or merge with or into, the Company, and the Company shall be the continuing or surviving corporation of such consolidation or merger and, in connection with such

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consolidation or merger, all or part of the outstanding shares of Common Stock shall be changed into or exchanged for stock or other securities of any other Person or cash or any other property, or (iii) the Company shall sell or otherwise transfer (or one or more of its Subsidiaries shall sell or otherwise transfer) assets (A) aggregating more than 50% of the assets (measured by either book value or fair market value) or (B) generating more than 50% of the operating income or cash flow, of the Company and its Subsidiaries (taken as a whole) to any Person or Persons (other than the Company or one or more of its Subsidiaries in one or more transactions each of which complies with Section 3.1(f) hereof).

“Market Price” per share of any securities on any date shall mean the average of the daily closing prices per share of such securities (determined as described below) on each of the twenty (20) consecutive Trading Days through and including the Trading Day immediately preceding such date; provided, however, that if an event of a type analogous to any of the events described in Section 2.4 hereof shall have caused the closing prices used to determine the Market Price on any Trading Days during such period of twenty (20) Trading Days not to be fully comparable with the closing price on such date, each such closing price so used shall be appropriately adjusted in order to make it fully comparable with the closing price on such date. The closing price per share of any securities on any date shall be the last reported sale price, regular way, or, in case no such sale takes place or is quoted on such date, the average of the closing bid and asked prices, regular way, for each share of such securities, in either case as reported in the principal consolidated transaction reporting system with respect to securities listed or admitted to trading on the NASDAQ Stock Market or, if the securities are not listed or admitted to trading on the NASDAQ Stock Market, as reported in the principal consolidated transaction reporting system with respect to securities listed on the principal national securities exchange on which the securities are listed or admitted to trading or, if the securities are not listed or admitted to trading on the NASDAQ Stock Market, or such other system then in use, or, if on any such date the securities are not listed or admitted to trading on any national securities exchange or quoted by any such organization, the average of the closing bid and asked prices as furnished by a professional market maker making a market in the securities selected by the Board of Directors of the Company; provided, however, that if on any such date the securities are not listed or admitted to trading on a national securities exchange or traded in the over-the counter market, the closing price per share of such securities on such date shall mean the fair value per share of securities on such date as determined in good faith by the Board of Directors of the Company, after consultation with a nationally recognized investment banking firm, and set forth in a certificate delivered to the Rights Agent.

“Person” shall mean any individual, firm, partnership, association, group (as such term is used in Rule 13d-5 under the Exchange Act.

“Preferred Stock” shall mean the series of Series A Junior Participating Preferred Stock, par value $0.01 per share, of the Company created by a Certificate of Designation in substantially the form set forth in Exhibit B hereto appropriately completed.

“Record Time” shall have the meaning set forth in the Recitals.

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“Redemption Price” shall mean an amount equal to one cent, $0.01, as such amount may be appropriately adjusted to reflect any stock split, stock dividend or similar transaction occurring after the date hereof.

“Redemption Time” shall mean the time at which the right to exercise the Rights shall terminate pursuant to Section 5.1 hereof.

“Right” shall have the meaning set forth in the Recitals.

“Rights Agent” shall have the meaning set forth in the Preamble.

“Rights Certificate” shall have the meaning set forth in Section 2.3(c) hereof.

“Rights Dividend Declaration Date” shall have the meaning set forth in the Recitals.

“Rights Register” shall have the meaning set forth in Section 2.7(a) hereof.

“Separation Time” shall mean the Close of Business on the earliest of (i) the tenth Business Day (or such later date as the Board of Directors of the Company may from time to time fix by resolution adopted prior to the Separation Time that would otherwise have occurred) after the date on which any Person commences a tender or exchange offer following the date hereof which, if consummated, would result in such Person’s becoming an Acquiring Person; (ii) immediately prior to the acceptance for payment of the Common Stock tendered pursuant to any tender offer or exchange offer commenced by or on behalf of any Person (other than the Company or its Subsidiaries) prior to, and pending as of, the date hereof, if upon consummation thereof, such Person would become an Acquiring Person; and (iii) the tenth Business Day after the Stock Acquisition Date; provided, that if the foregoing results in the Separation Time being prior to the Record Time, the Separation Time shall be the Record Time and provided further, that if any tender or exchange offer referred to in clause (i) of this paragraph is cancelled, terminated or otherwise withdrawn prior to the Separation Time without the purchase of any shares of Common Stock pursuant thereto, such offer shall be deemed, for purposes of this paragraph, never to have been made.

“Stock Acquisition Date” shall mean the first date of public announcement following the date hereof by the Company (by any means) or by an Acquiring Person (including by means of filing a Schedule 13D or Schedule 13G under the Exchange Act (or any comparable or successor report or schedule) or an amendment thereto) that a Person has become an Acquiring Person.

“Subsidiary” of any specified Person shall mean any corporation or other entity of which a majority of the voting power of the equity securities or a majority of the equity interest is Beneficially Owned, directly or indirectly, by such Person.

“Synthetic Long Position” shall mean any option, warrant, convertible security, stock appreciation right, swap agreement or other security, contract right or derivative position, whether or not presently exercisable, that has an exercise or conversion privilege or a settlement

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payment or mechanism at a price related to the value of Common Stock or a value determined in whole or part with reference to, or derived in whole or in part from, the value of Common Stock and that increases in value as the value of Common Stock increases or that provides to the holder an opportunity, directly or indirectly, to profit or share in any profit derived from any increase in the value of Common Stock, in any case without regard to whether (i) such derivative conveys any voting rights in such securities to such Person or any of such Person’s Affiliates or Associates, (ii) such derivative is required to be, or capable of being, settled through delivery of such securities, or (iii) such Person or any of such Person’s Affiliates or Associates may have entered into other transactions that hedge the economic effect of such derivative. A Synthetic Long Position shall not include any interests, rights, options or other securities set forth in Rule 16a-1(c)(1)-(5) or (7) of the General Rules and Regulations under the Exchange Act.

“Trading Day,” when used with respect to any securities, shall mean a day on which the New York Stock Exchange is open for the transaction of business or, if such securities are not listed or admitted to trading on the New York Stock Exchange, a day on which the principal national securities exchange on which such securities are listed or admitted to trading is open for the transaction of business or, if such securities are not listed or admitted to trading on any national securities exchange, a Business Day.

“Trading Regulation” shall have the meaning set forth in Section 2.3(c).

ARTICLE II

THE RIGHTS

2.1 Summary of Rights.

As soon as practicable after the Record Time, the Company will make available a letter summarizing the terms of the Rights to any holder of Rights who may so request from time to time prior to the Expiration Time.

2.2 Legend on Common Stock Certificates.

Confirmation or account statements sent to holders of Common Stock in Book Entry form, or, in the case of certificated shares of Common Stock, certificates representing shares of Common Stock, in each case issued after the Record Time but prior to the earlier of the Separation Time or the Expiration Time shall evidence one Right for each share of Common Stock represented thereby and shall have impressed on, printed on, written on or otherwise affixed to them a statement or legend in substantially the following form:

Until the Separation Time (as defined in the Rights Agreement referred to below), this certificate also evidences and entitles the holder hereof to certain Rights as set forth in a Rights Agreement, dated as of May 16, 2012 (as such may be amended from time to time, the “Rights Agreement”), between Human Genome Sciences, Inc. (the “Company”) and American Stock Transfer & Trust Company, as Rights Agent, the terms of which are hereby

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incorporated herein by reference and a copy of which is on file at the principal executive offices of the Company. Under certain circumstances, as set forth in the Rights Agreement, such Rights may be redeemed, may become exercisable for securities or assets of the Company or securities of another entity, may be exchanged for shares of Common Stock or other securities or assets of the Company, may expire, may become void (if they are “Beneficially Owned” by an “Acquiring Person” or an Affiliate or Associate thereof, as such terms are defined in the Rights Agreement, or by any transferee of any of the foregoing) or may be evidenced by separate certificates and may no longer be evidenced by this certificate. The Company will mail or arrange for the mailing of a copy of the Rights Agreement to the holder of this certificate without charge after the receipt of a written request therefor.

Shares of Common Stock that are issued and outstanding as of the Record Time shall evidence one Right for each share of Common Stock evidenced thereby notwithstanding the absence of the foregoing statement or legend.

2.3 Exercise of Rights; Separation of Rights.

(a) Subject to Sections 3.1, 5.1 and 5.10 and subject to adjustment as herein set forth, each Right will entitle the holder thereof, after the Separation Time and prior to the Expiration Time, to purchase, for the Exercise Price, one one-hundredth of a share of Preferred Stock.

(b) Until the Separation Time, (i) no Right may be exercised, (ii) in the case of certificated shares of Common Stock, each Right will be evidenced by the certificate for the associated share of Common Stock, and, in the case of uncertificated shares of Common Stock, each Right will be evidenced by the balances indicated in the Book Entry account system of the transfer agent for the Common Stock registered in the names of the holders thereof, and (iii) the Rights will be transferable only together with, and will be transferred by a transfer of, such associated share (including a transfer to the Company).

(c) Subject to the terms and conditions hereof, after the Separation Time and prior to the Expiration Time, the Rights (i) may be exercised and (ii) may be transferred independently of shares of Common Stock. Promptly following the Separation Time, (provided that the Board of Directors of the Company has not elected to exchange all of the then outstanding Rights pursuant to Section 3.1(c)), the Rights Agent, if requested by the Company and provided with all necessary information, will mail to each holder of record of Common Stock as of the Separation Time (other than any Person whose Rights have become void pursuant to Section 3.1(b)), at such holder’s address as shown by the records of the Company (the Company hereby agreeing to furnish copies of such records to the Rights Agent for this purpose), a certificate (a “Rights Certificate”) in substantially the form of Exhibit A hereto appropriately completed, representing the number of Rights held by such holder at the Separation Time and having such marks of

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identification or designation and such legends, summaries or endorsements printed thereon as the Company may deem appropriate and as are not inconsistent with the provisions of this Agreement, or as may be required to comply with any law or with any rule or regulation made pursuant thereto or with any rule or regulation of any national securities exchange or quotation system on which the Rights may from time to time be listed or traded (“Trading Regulation”), or to conform to usage; provided, however, that the Company shall have no obligation to distribute Rights Certificates to any Acquiring Person or Affiliate or Associate of an Acquiring Person or any transferee of any of the foregoing. Receipt of a Rights Certificate by any Person shall not preclude a later determination that such Rights are void pursuant to Section 3.1(b).

(d) Subject to the terms and conditions hereof, Rights may be exercised on any Business Day after the Separation Time and prior to the Expiration Time by submitting to the Rights Agent the Rights Certificate evidencing such Rights with an Election to Exercise (an “Election to Exercise”) substantially in the form attached to the Rights Certificate duly completed, accompanied by payment in cash, or by certified or official bank check or money order payable to the order of the Company, of a sum equal to the Exercise Price multiplied by the number of Rights being exercised and a sum sufficient to cover any transfer tax or charge which may be payable in respect of any transfer involved in the transfer or delivery of Rights Certificates or the issuance or delivery of certificates for shares or depositary receipts (or both), or entry in the Book Entry account system of the transfer agent, in a name other than that of the holder of the Rights being exercised.

(e) Upon receipt of a Rights Certificate, with an Election to Exercise accompanied by payment as set forth in Section 2.3(d), and subject to the terms and conditions hereof, the Rights Agent will thereupon promptly (i)(A) in the case of certificated shares of Common Stock, Preferred Stock, or other securities, requisition from a transfer agent stock certificates evidencing such number of shares or other securities to be purchased (the Company hereby irrevocably authorizing its transfer agents to comply with all such requisitions), and, in the case of uncertificated shares of Common Stock, Preferred Stock, or other securities, inform the transfer agent of the number of shares or other securities to be purchased, which number shall be registered in the Book Entry account system of the transfer agent for the Common Stock registered in the names of the holders thereof, and (B) if the Company elects pursuant to Section 5.5 not to issue certificates representing fractional shares, requisition from the depositary selected by the Company depositary receipts representing the fractional shares to be purchased, inform the transfer agent of the entries to be made in the transfer agent’s Book Entry account system with respect to the fractional shares, or requisition from the Company the amount of cash to be paid in lieu of fractional shares in accordance with Section 5.5 and (ii) after receipt of such depositary receipts, cash, and/or certificates (in the case of certificated shares of Common Stock) or receipt of confirmation from the transfer agent that the number of shares or other securities has been registered in the Book Entry account system of the transfer agent (in the case of uncertificated shares of Common Stock), deliver the same to or upon the order of the registered holder of such Rights Certificate, registered (in the case of certificates or depositary receipts) in such name or names as may be designated by such holder. The Company reserves the right to require prior to the occurrence of a Flip-over Transaction or Event or a Flip-in Date that, upon any exercise of Rights, a number of Rights be exercised so that only whole shares would be issued.

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(f) In case the holder of any Rights shall exercise less than all the Rights evidenced by such holder’s Rights Certificate, a new Rights Certificate evidencing the Rights remaining unexercised will be issued by the Rights Agent to such holder or to such holder’s duly authorized assigns, subject to Section 5.5 hereof.

(g) The Company covenants and agrees that it will (i) take all such action as may be necessary to ensure that all shares delivered upon exercise of Rights shall, at the time of delivery of the certificates or entries in the Book Entry account system of the transfer agent for such shares (subject to payment of the Exercise Price), be duly and validly authorized, executed, issued and delivered and fully paid and nonassessable; (ii) take all such action as may be necessary to comply with any applicable requirements of the Securities Act of 1933 or the Exchange Act, and the rules and regulations thereunder, and any other applicable law, rule or regulation, in connection with the issuance of any shares upon exercise of Rights; and (iii) pay when due and payable any and all federal and state transfer taxes and charges which may be payable in respect of the original issuance or delivery of the Rights Certificates or of any shares issued upon the exercise of Rights, provided, that the Company shall not be required to pay any transfer tax or charge which may be payable in respect of any transfer involved in the transfer or delivery of Rights Certificates or the issuance or delivery of certificates or entries in the Book Entry account system of the transfer agent for shares in a name other than that of the holder of the Rights being transferred or exercised.

(h) Notwithstanding anything in this Agreement to the contrary, neither the Rights Agent nor the Company shall be obligated to undertake any action with respect to the exercise or assignment of a Rights Certificate unless the registered holder of such Rights Certificate shall have (i) properly completed and duly signed the certificate following the form of assignment or the form of election to exercise, as applicable, set forth on the reverse side of the Rights Certificate surrendered for such exercise or assignment. (ii) provided such additional evidence of the identity of the Beneficial Owner (or former Beneficial Owner) thereof and of the Rights evidenced thereby, and the Affiliates and Associates of such Beneficial Owner or former Beneficial Owner, as the Company or the Rights Agent may reasonably request and (iii) paid a sum sufficient to cover any tax or charge that may be imposed in connection with any transfer, split up, combination or exchange of Rights Certificates as required under Section 2.3(d) hereof.

2.4 Adjustments to Exercise Price; Number of Rights.

(a) In the event the Company shall at any time after the Rights Dividend Declaration Date and prior to the Separation Time (i) declare or pay a dividend on Common Stock payable in Common Stock, (ii) subdivide the outstanding Common Stock or (iii) combine the outstanding Common Stock into a smaller number of shares of Common Stock, (x) the Exercise Price in effect after such adjustment will be equal to the Exercise Price in effect immediately prior to such adjustment divided by the number of shares of Common Stock including any fractional shares in lieu of which such holder received cash (the “Expansion Factor”) that a holder of one share of Common Stock immediately prior to such dividend, subdivision or combination would hold thereafter as a result thereof and (y) each Right held prior to such adjustment will become

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that number of Rights equal to the Expansion Factor, and the adjusted number of Rights will be deemed to be distributed among the shares of Common Stock with respect to which the original Rights were associated (if they remain outstanding) and the shares issued in respect of such dividend, subdivision or combination, so that each such share of Common Stock will have exactly one Right associated with it. Each adjustment made pursuant to this paragraph shall be made as of the payment or effective date for the applicable dividend, subdivision or combination.

In the event the Company shall at any time after the Rights Dividend Declaration Date and prior to the Separation Time issue any shares of Common Stock otherwise than in a transaction referred to in the preceding paragraph, each such share of Common Stock so issued shall automatically have one new Right associated with it, which Right shall be evidenced by the certificate representing such share (in the case of certificated shares of Common Stock), and shall be evidenced by the balances indicated in the Book Entry account system of the transfer agent for the Common Stock registered in the names of the holders thereof (in the case of uncertificated shares of Common Stock). To the extent provided in Section 5.3, Rights shall be issued by the Company in respect of shares of Common Stock that are issued or sold by the Company after the Separation Time.

(b) In the event the Company shall at any time after the Rights Dividend Declaration Date and prior to the Separation Time issue or distribute any securities or assets in respect of, in lieu of or in exchange for Common Stock (other than pursuant to any non-extraordinary periodic cash dividend or a dividend paid solely in Common Stock) whether by dividend, in a reclassification or recapitalization (including any such transaction involving a merger, consolidation or share exchange), or otherwise, the Company shall make such adjustments, if any, in the Exercise Price, number of Rights and/or securities or other property purchasable upon exercise of Rights as the Board of Directors of the Company, in its sole discretion, may deem to be appropriate under the circumstances in order to adequately protect the interests of the holders of Rights generally, and the Company and the Rights Agent shall amend this Agreement as necessary to provide for such adjustments.

(c) Anything herein to the contrary notwithstanding, no adjustment to the Exercise Price shall be required unless such adjustment would require an increase or decrease of at least 1% of the Exercise Price; provided, however, that any adjustments that by reason of this Section 2.4(c) are not required to be made shall be carried forward and taken into account in any subsequent adjustment. Each adjustment to the Exercise Price made pursuant to this Section 2.4 shall be calculated to the nearest cent or to the nearest thousandth of a share of Common Stock or one-hundred-thousandth of a share of Preferred Stock, as the case may be. Notwithstanding the first sentence of this Section 2.4(c), any adjustment required by this Section 2.4 shall be made no later than the Expiration Time. Whenever an adjustment to the Exercise Price is made pursuant to this Section 2.4, the Company shall (i) promptly prepare a certificate setting forth such adjustment and a brief statement of the facts accounting for such adjustment, (ii) promptly file with the Rights Agent and with each transfer agent for the Common Stock a copy of such certificate, and (iii) if a Separation Time has occurred, mail a brief summary thereof to each holder of a Rights Certificate in accordance with Section 5.9 hereof.

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(d) Rights Certificates shall represent the securities purchasable under the terms of this Agreement, including any adjustment or change in the securities purchasable upon exercise of the Rights, even though such certificates may continue to express the securities purchasable at the time of issuance of the initial Rights Certificates.

2.5 Date on Which Exercise is Effective.

Each person in whose name any certificate or entry in the Book Entry account system of the transfer agent for shares is issued upon the exercise of Rights shall for all purposes be deemed to have become the holder of record of the shares represented thereby on the date upon which the Rights Certificate evidencing such Rights was duly surrendered and payment of the Exercise Price for such Rights (and any applicable taxes and other governmental charges payable by the exercising holder hereunder) was made; provided, however, that if the date of such surrender and payment is a date upon which the stock transfer books of the Company are closed, such person shall be deemed to have become the record holder of such shares on, and such certificate or entry in the Book Entry account system of the transfer agent shall be dated, the next succeeding Business Day on which the stock transfer books of the Company are open.

2.6 Execution, Authentication, Delivery and Dating of Rights Certificates.

(a) The Rights Certificates shall be executed on behalf of the Company by its Chairman of the Board, Chief Executive Officer or one of its Vice Presidents, and countersigned by its Secretary, an Assistant Secretary or its Chief Financial Officer. The signature of any of these officers on the Rights Certificates may be manual or facsimile.

Rights Certificates bearing the manual or facsimile signatures of individuals who were at any time the proper officers of the Company shall bind the Company, notwithstanding that such individuals or any of them have ceased to hold such offices prior to the countersignature and delivery of such Rights Certificates.

Promptly after the Company learns of the Separation Time, the Company will notify the Rights Agent of such Separation Time and will deliver Rights Certificates executed by the Company to the Rights Agent for counter-signature, and, subject to Section 3.1(b), the Rights Agent shall manually countersign and deliver such Rights Certificates to the holders of the Rights pursuant to Section 2.3(c) hereof. No Rights Certificate shall be valid for any purpose unless manually countersigned by the Rights Agent.

(b) Each Rights Certificate shall be dated the date of countersignature thereof.

2.7 Registration of Transfer and Exchange.

(a) After the Separation Time, the Company will cause to be kept a register (the “Rights Register”) in which, subject to such reasonable regulations as it may prescribe, the Company will provide for the registration and transfer of Rights. The Rights Agent is hereby appointed “Rights Registrar” for the purpose of maintaining the Rights Register for the Company

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and registering Rights and transfers of Rights after the Separation Time as herein provided. In the event that the Rights Agent shall cease to be the Rights Registrar, the Rights Agent will have the right to examine the Rights Register at all reasonable times after the Separation Time.

After the Separation Time and prior to the Expiration Time, upon surrender for registration of transfer or exchange of any Rights Certificate, and subject to the provisions of Section 2.7(c) and (d), the Company will execute, and the Rights Agent will countersign and deliver, in the name of the holder or the designated transferee or transferees, as required pursuant to the holder’s instructions, one or more new Rights Certificates evidencing the same aggregate number of Rights as did the Rights Certificate so surrendered.

(b) Except as otherwise provided in Section 3.1(b), all Rights issued upon any registration of transfer or exchange of Rights Certificates shall be the valid obligations of the Company, and such Rights shall be entitled to the same benefits under this Agreement as the Rights surrendered upon such registration of transfer or exchange.

(c) Every Rights Certificate surrendered for registration of transfer or exchange shall be duly endorsed, or be accompanied by a written instrument of transfer in form satisfactory to the Company or the Rights Agent, as the case may be, duly executed by the holder thereof or such holder’s attorney duly authorized in writing. As a condition to the issuance of any new Rights Certificate under this Section 2.7, the Company may require the payment of a sum sufficient to cover any tax or other governmental charge that may be imposed in relation thereto.

(d) The Company shall not be required to register the transfer or exchange of any Rights after such Rights have become void under Section 3.1(b), been exchanged under Section 3.1(c) or been redeemed under Section 5.1.

2.8 Mutilated, Destroyed, Lost and Stolen Rights Certificates.

(a) If any mutilated Rights Certificate is surrendered to the Rights Agent prior to the Expiration Time, then, subject to Sections 3.1(b), 3.1(c) and 5.1, the Company shall execute and the Rights Agent shall countersign and deliver in exchange therefor a new Rights Certificate evidencing the same number of Rights as did the Rights Certificate so surrendered.

(b) If there shall be delivered to the Company and the Rights Agent prior to the Expiration Time (i) evidence to their satisfaction of the destruction, loss or theft of any Rights Certificate and (ii) such security or indemnity as may be required by them to save each of them and any of their agents harmless, then, subject to Sections 3.1(b), 3.1(c) and 5.1 and in the absence of notice to the Company or the Rights Agent that such Rights Certificate has been acquired by a bona fide purchaser, the Company shall execute and upon its request the Rights Agent shall countersign and deliver, in lieu of any such destroyed, lost or stolen Rights Certificate, a new Rights Certificate evidencing the same number of Rights as did the Rights Certificate so destroyed, lost or stolen.

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(c) As a condition to the issuance of any new Rights Certificate under this Section 2.8, the Company may require the payment of a sum sufficient to cover any tax or other governmental charge that may be imposed in relation thereto and any other expenses (including the fees and expenses of the Rights Agent) connected therewith.

(d) Every new Rights Certificate issued pursuant to this Section 2.8 in lieu of any destroyed, lost or stolen Rights Certificate shall evidence an original additional contractual obligation of the Company, whether or not the destroyed, lost or stolen Rights Certificate shall be at any time enforceable by anyone, and, subject to Section 3.1(b) shall be entitled to all the benefits of this Agreement equally and proportionately with any and all other Rights duly issued hereunder.

2.9 Persons Deemed Owners.

Prior to due presentment of a Rights Certificate (or, prior to the Separation Time, the associated Common Stock certificate or entry in the Book Entry account system of the transfer agent) for registration of transfer, the Company, the Rights Agent and any agent of the Company or the Rights Agent may deem and treat the person in whose name such Rights Certificate (or, prior to the Separation Time, such Common Stock certificate or entry in the Book Entry account system of the transfer agent) is registered as the absolute owner thereof and of the Rights evidenced thereby for all purposes whatsoever, including the payment of the Redemption Price and neither the Company nor the Rights Agent shall be affected by any notice to the contrary. As used in this Agreement, unless the context otherwise requires, the term “holder” of any Rights shall mean the registered holder of such Rights (or, prior to the Separation Time, the associated shares of Common Stock).

2.10 Delivery and Cancellation of Certificates.

All Rights Certificates surrendered upon exercise or for registration of transfer or redemption or exchange shall, if surrendered to the Company or any of its agents other than the Rights Agent, be delivered to the Rights Agent and, in any case, shall be promptly cancelled by the Rights Agent. The Company may at any time deliver to the Rights Agent for cancellation any Rights Certificates previously countersigned and delivered hereunder which the Company may have acquired in any manner whatsoever, and all Rights Certificates so delivered shall be promptly cancelled by the Rights Agent. No Rights Certificates shall be countersigned in lieu of or in exchange for any Rights Certificates cancelled as provided in this Section 2.10, except as expressly permitted by this Agreement. The Rights Agent shall destroy all cancelled Rights Certificates and deliver a certificate of destruction to the Company.

2.11 Agreement of Rights Holders.

Every holder of Rights by accepting the same consents and agrees with the Company and the Rights Agent and with every other holder of Rights that:

(a) prior to the Separation Time, each Right will be transferable only together with, and will be transferred by a transfer of, the associated share of Common Stock;

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(b) after the Separation Time, the Rights Certificates will be transferable only on the Rights Register as provided herein;

(c) prior to due presentment of a Rights Certificate (or, prior to the Separation Time, the associated Common Stock certificate or entry in the Book Entry account system of the transfer agent) for registration of transfer, the Company, the Rights Agent and any agent of the Company or the Rights Agent may deem and treat the person in whose name the Rights Certificate (or, prior to the Separation Time, the associated Common Stock certificate or entry in the Book Entry account system of the transfer agent) is registered as the absolute owner thereof and of the Rights evidenced thereby for all purposes whatsoever, and neither the Company nor the Rights Agent shall be affected by any notice to the contrary;

(d) Rights beneficially owned by certain Persons will, under the circumstances set forth in Section 3.1(b), become void;

(e) this Agreement may be supplemented or amended from time to time pursuant to Section 2.4(b) or 5.4 hereof; and

(f) notwithstanding anything in this Agreement to the contrary, neither the Company nor the Rights Agent shall have any liability to any holder of a Right or other Person as a result of its inability to perform any of its obligations under this Agreement by reason of any preliminary or permanent injunction or other order, decree or ruling issued by a court of competent jurisdiction or by a governmental, regulatory or administrative agency or commission, or any statute, rule, regulation or executive order promulgated or enacted by any governmental authority, prohibiting or otherwise restraining performance of such obligation; provided, however, the Company must use its best efforts to have any such order, decree or ruling lifted or otherwise overturned as soon as possible.

ARTICLE III

ADJUSTMENTS TO THE RIGHTS IN

THE EVENT OF CERTAIN TRANSACTIONS

3.1 Flip-in.

(a) In the event that prior to the Expiration Time a Flip-in Date shall occur (unless the event causing the Flip-in Date is a Flip-over Transaction or Event), then, except as provided in this Section 3.1, each Right shall constitute the right to purchase from the Company, upon exercise thereof in accordance with the terms hereof (but subject to Section 5.10), that number of shares of Common Stock having an aggregate Market Price on the Stock Acquisition Date that gave rise to the Flip-in Date equal to twice the Exercise Price for an amount in cash equal to the Exercise Price (such right to be appropriately adjusted in order to protect the interests of the holders of Rights generally in the event that on or after the date hereof an event of a type analogous to any of the events described in Section 2.4(a) or (b) shall have occurred with respect to the Common Stock).

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(b) Notwithstanding the foregoing, any Rights that are or were Beneficially Owned on or after the Stock Acquisition Date by an Acquiring Person or an Affiliate or Associate thereof or by any transferee, direct or indirect, of any of the foregoing shall become void and any holder of such Rights (including transferees) shall thereafter have no right to exercise or transfer such Rights under any provision of this Agreement. If any Rights Certificate is presented for assignment or exercise and the Person presenting the same will not complete the certification set forth at the end of the form of assignment or notice of election to exercise and provide such additional evidence of the identity of the Beneficial Owner and its Affiliates and Associates (or former Beneficial Owners and their Affiliates and Associates) as the Company shall reasonably request, then the Company shall be entitled conclusively to deem the Beneficial Owner thereof to be an Acquiring Person or an Affiliate or Associate thereof or a transferee of any of the foregoing and accordingly will deem the Rights evidenced thereby to be void and not transferable or exercisable.

(c) At any time after a Flip-in Date and prior to (i) the time that an Acquiring Person becomes the Beneficial Owner of more than 50% of the outstanding shares of Common Stock or (ii) the occurrence of a Flip-over Transaction or Event, the Board of Directors of the Company may, at its option, elect to exchange all or part of the then outstanding Rights (which shall not include Rights that have become void pursuant to the provisions of Section 3.1(b)) for shares of Common Stock at an exchange ratio of one share of Common Stock per Right, appropriately adjusted in order to protect the interests of holders of Rights generally in the event that after the date hereof an event of a type analogous to any of the events described in Section 2.4(a) or (b) shall have occurred with respect to the Common Stock (such exchange ratio, as adjusted from time to time, being hereinafter referred to as the “Exchange Ratio”).

Immediately upon the action of the Board of Directors of the Company electing to exchange the Rights, without any further action and without any notice, the right to exercise the Rights will terminate and each Right (other than Rights that have become void pursuant to Section 3.1(b)) will thereafter represent only the right to receive a number of shares of Common Stock equal to the Exchange Ratio. The exchange of the Rights by the Board of Directors may be made effective at such time, on such basis and with such conditions as the Board of Directors in its sole discretion may establish. Promptly after the action of the Board of Directors electing to exchange the Rights, the Company shall give notice thereof (specifying the steps to be taken to receive shares of Common Stock in exchange for Rights) to the Rights Agent and the holders of the Rights (other than Rights that have become void pursuant to Section 3.1(b)) outstanding immediately prior thereto by mailing such notice in accordance with Section 5.9. Any partial exchange shall be effected pro rata based on the number of Rights (other than Rights that have become void pursuant to Section 3.1(b)) held by each holder of Rights.

Each Person in whose name any certificate or entry in the Book Entry account system of the transfer agent for shares of Common Stock is issued upon the exchange of Rights pursuant to this Section 3.1(c) or Section 3.1(d) shall for all purposes be deemed to have become the holder

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of record of the shares represented thereby on, and such certificate or entry in the Book Entry account system of the transfer agent shall be dated, the date upon which the Rights Certificate evidencing such Rights was duly surrendered and payment of any applicable taxes and other governmental charges payable by the holder was made; provided, however, that if the date of such surrender and payment is a date upon which the stock transfer books of the Company are closed, such Person shall be deemed to have become the record holder of such shares on, and such certificate or entry in the Book Entry account system of the transfer agent shall be dated, the next succeeding Business Day on which the stock transfer books of the Company are open.

Following the action of the Board of Directors of the Company ordering the exchange of any Rights pursuant to this Section 3.1(c), the Company may implement such procedures in its sole discretion as it deems appropriate for the purpose of ensuring that the Common Stock (or such other consideration) issuable upon an exchange pursuant to this Section 3.1(c) not be received by holders of Rights that have become void pursuant to 3.1(b) hereof. In furtherance thereof, if so directed by the Company, shares of Common Stock (or other consideration) potentially issuable to holders of Rights upon an exchange pursuant to this Section 3.1(c), who have not verified to the satisfaction of the Company, in its sole discretion, that they are not Acquiring Persons, may be deposited in a trust established by the Company pending receipt of appropriate verification.

(d) Whenever the Company shall become obligated under Section 3.1(a) or (c) to issue shares of Common Stock upon exercise of or in exchange for Rights, the Company, at its option, may substitute therefor shares of Preferred Stock, at a ratio of one one-hundredth of a share of Preferred Stock for each share of Common Stock so issuable, as appropriately adjusted to reflect stock splits, stock dividends and other similar transactions after the date hereof.

(e) In the event that there shall not be sufficient authorized but unissued shares of Common Stock or Preferred Stock of the Company to permit the exercise or exchange of the Rights in accordance with Section 3.1(a) or (c), and the Company elects not to, or is otherwise unable to, make the exchange referred to in Section 3.1(c), the Company shall either (i) call a meeting of stockholders seeking approval to cause sufficient additional shares to be authorized (provided that if such approval is not obtained the Company will take the action specified in clause (ii) of this sentence) or (ii) take such action as shall be necessary to ensure and provide, to the extent permitted by applicable law and any agreements or instruments in effect on the Stock Acquisition Date to which it is a party, that each Right shall thereafter constitute the right to receive, (x) at the Company’s option, either (A) in return for the Exercise Price, debt or equity securities or other assets (or a combination thereof) having a fair value equal to twice the Exercise Price, or (B) without payment of consideration (except as otherwise required by applicable law), debt or equity securities or other assets (or a combination thereof) having a fair value equal to the Exercise Price, or (y) if the Board of Directors of the Company elects to exchange the Rights in accordance with Section 3.1(c), debt or equity securities or other assets (or a combination thereof) having a fair value equal to the product of the Market Price of a share of Common Stock on the Flip-in Date times the Exchange Ratio in effect on the Flip-in Date, where in any case set forth in (x) or (y) above the fair value of such debt or equity securities or other assets shall be as determined in good faith by the Board of Directors of the Company, after consultation with a nationally recognized investment banking firm.

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(f) The Company covenants and agrees that, after the Separation Time, it will not, except as permitted by Section 3.1(c), Section 5.1, Section 5.4 or Section 5.10 hereof, take (or permit any Subsidiary to take) any action if at the time such action is taken it is reasonably foreseeable that such action will diminish substantially or otherwise eliminate the benefits to the holders of the Rights intended to be afforded by the Rights.

3.2 Flip-over.

(a) After the Separation Time and prior to the Expiration Time, the Company shall not enter into any agreement with respect to, consummate or permit to occur any Flip-over Transaction or Event unless and until it shall have entered into a supplemental agreement with the Flip-over Entity, for the benefit of the holders of the Rights, providing that, upon consummation or occurrence of the Flip-over Transaction or Event (i) each Right (other than Rights that have become void pursuant to Section 3.1(b)) shall thereafter constitute the right to purchase from the Flip-over Entity, upon exercise thereof in accordance with the terms hereof, that number of shares of Flip-over Stock of the Flip-over Entity having an aggregate Market Price on the date of consummation or occurrence of such Flip-over Transaction or Event equal to twice the Exercise Price for an amount in cash equal to the Exercise Price (such right to be appropriately adjusted in order to protect the interests of the holders of Rights generally in the event that after such date of consummation or occurrence an event of a type analogous to any of the events described in Section 2.4(a) or (b) shall have occurred with respect to the Flip-over Stock), (ii) the Flip-over Entity shall thereafter be liable for, and shall assume, by virtue of such Flip-over Transaction or Event and such supplemental agreement, all the obligations and duties of the Company pursuant to this Agreement, (iii) the term “Company” shall thereafter be deemed to refer to such Flip-over Entity, (iv) the Flip-over Entity shall take such steps (including, but not limited to, the reservation of a sufficient number of shares of its Flip-over Stock) in connection with the consummation of any such transaction as may be necessary to assure that the provisions hereof shall thereafter be applicable, as nearly as reasonably may be, in relation to its shares of Flip-over Stock thereafter deliverable upon the exercise of the Rights and (v) the provisions of Section 3.1(a) shall be of no effect following the first occurrence of any Flip-over Transaction or Event.

(b) The Company shall not consummate or permit to occur any Flip-over Transaction or Event unless the Flip-over Entity shall have a sufficient number of authorized shares of its Flip-over Stock that have not been issued or reserved for issuance to permit the exercise in full of the Rights in accordance with this Section 3.2 and unless prior thereto the Company and such Flip-over Entity shall have executed and delivered to the Rights Agent a supplemental agreement providing for the terms set forth in Section 3.2(a) and further providing that, as soon as practicable after the date of the Flip-over Transaction or Event, the Flip-over Entity will:

(i) prepare and file a registration statement under the Act, with respect to the Rights and the Flip-over Stock purchasable upon exercise of the Rights on an appropriate form,

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and will use its best efforts to cause such registration statement to (A) become effective as soon as practicable after such filing and (B) remain effective (with a prospectus at all times meeting the requirements of the Act) until the Expiration Time;

(ii) take all such other action as may be necessary to enable the Flip-over Entity to issue the Flip-over Stock purchasable upon exercise of the Rights, including but not limited to the registration or qualification of such Flip-over Stock under all requisite securities laws of jurisdictions of the various states and the listing of such Flip-over Stock on such exchanges and trading markets as may be necessary or appropriate; and

(iii) will deliver to holders of the Rights historical financial statements for the Flip-over Entity and each of its Affiliates which comply in all respects with the requirements for registration on Form 10 (or any successor form) under the Exchange Act.

The provisions of this Section 3.2 shall apply to successive Flip-over Transactions or Events. In the event that a Flip-over Transaction or Event shall occur at any time after the occurrence of a Flip-in Date, the Rights which have not theretofore been exercised shall thereafter become exercisable in the manner described in Section 3.2(a).

(c) After the Separation Time and prior to the Expiration Time, unless the Rights will be redeemed pursuant to Section 5.1 hereof in connection therewith, the Company shall not enter into any agreement with respect to, consummate or permit to occur any Flip-over Transaction or Event if (i) at the time of or immediately after such Flip-over Transaction or Event there are any rights, warrants or securities outstanding or any other arrangements, agreements or instruments that would eliminate or otherwise diminish in any material respect the benefits intended to be afforded by this Rights Agreement to the holders of Rights upon consummation of such transaction or (ii) prior to, simultaneously with or immediately after such Flip-over Transaction or Event, the stockholders of the Person who constitutes, or would constitute, the Flip-over Entity for purposes of Section 3.2(a) hereof shall have received a distribution of Rights previously owned by such Person or any of its Affiliates and Associates.

ARTICLE IV

THE RIGHTS AGENT

4.1 General.

(a) The Company hereby appoints the Rights Agent to act as agent for the Company in accordance with the terms and conditions hereof, and the Rights Agent hereby accepts such appointment. The Company agrees to pay to the Rights Agent reasonable compensation for all services rendered by it hereunder and, from time to time, on demand of the Rights Agent, its reasonable expenses and counsel fees and other disbursements incurred in the administration and execution of this Agreement and the exercise and performance of its duties hereunder. The

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Company also agrees to indemnify the Rights Agent for, and to hold it harmless against, any loss, liability, or expense, incurred without gross negligence, bad faith or willful misconduct on the part of the Rights Agent, for anything done or omitted to be done by the Rights Agent in connection with the acceptance and administration of this Agreement, including the costs and expenses of defending against any claim of liability.

(b) The Rights Agent shall be protected and shall incur no liability for or in respect of any action taken, suffered or omitted by it in connection with its administration of this Agreement in reliance upon any certificate or entry in the Book Entry account system for the transfer agent for securities purchasable upon exercise of Rights, Rights Certificate, certificate or entry in the Book Entry account system of the transfer agent for other securities of the Company, instrument of assignment or transfer, power of attorney, endorsement, affidavit, letter, notice, direction, consent, certificate, statement, or other paper or document believed by it to be genuine and to be signed, executed and, where necessary, verified or acknowledged, by the proper person or persons.

4.2 Merger or Consolidation or Change of Name of Rights Agent.

(a) Any Person into which the Rights Agent or any successor Rights Agent may be merged, converted or with which it may be consolidated, or any Person resulting from any merger, conversion or consolidation to which the Rights Agent or any successor Rights Agent is a party, or any Person succeeding to the shareholder services business of the Rights Agent or any successor Rights Agent, will be the successor to the Rights Agent under this Agreement without the execution or filing of any paper or any further act on the part of any of the parties hereto, provided that such Person would be eligible for appointment as a successor Rights Agent under the provisions of Section 4.4 hereof. In case at the time such successor Rights Agent succeeds to the agency created by this Agreement any of the Rights Certificates have been countersigned but not delivered, any such successor Rights Agent may adopt the countersignature of the predecessor Rights Agent and deliver such Rights Certificates so countersigned; and in case at that time any of the Rights Certificates have not been countersigned, any successor Rights Agent may countersign such Rights Certificates either in the name of the predecessor Rights Agent or in the name of the successor Rights Agent; and in all such cases such Rights Certificates will have the full force provided in the Rights Certificates and in this Agreement.

(b) In case at any time the name of the Rights Agent is changed and at such time any of the Rights Certificates shall have been countersigned but not delivered, the Rights Agent may adopt the countersignature under its prior name and deliver Rights Certificates so countersigned; and in case at that time any of the Rights Certificates shall not have been countersigned, the Rights Agent may countersign such Rights Certificates either in its prior name or in its changed name; and in all such cases such Rights Certificates shall have the full force provided in the Rights Certificates and in this Agreement.

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4.3 Duties of Rights Agent.

The Rights Agent undertakes the duties and obligations imposed by this Agreement upon the following terms and conditions, by all of which the Company and the holders of Rights Certificates, by their acceptance thereof, shall be bound:

(a) The Rights Agent may consult with legal counsel (who may be legal counsel for the Company), and the opinion of such counsel will be full and complete authorization and protection to the Rights Agent as to any action taken or omitted by it in good faith and in accordance with such opinion.

(b) Whenever in the performance of its duties under this Agreement the Rights Agent deems it necessary or desirable that any fact or matter be proved or established by the Company prior to taking or suffering any action hereunder, such fact or matter (unless other evidence in respect thereof be herein specifically prescribed) may be deemed to be conclusively proved and established by a certificate signed by a person believed by the Rights Agent to be the Chairman of the Board, the Chief Executive Officer, the President or any Vice President and by the Treasurer or any Assistant Treasurer or the Secretary or any Assistant Secretary of the Company and delivered to the Rights Agent; and such certificate will be full authorization to the Rights Agent for any action taken or suffered in good faith by it under the provisions of this Agreement in reliance upon such certificate.

(c) The Rights Agent will be liable hereunder only for its and its directors’, officers’, employees’, affiliates’, agents’, advisors’ and representatives’ gross negligence, bad faith or willful misconduct.

(d) The Rights Agent will not be liable for or by reason of any of the statements of fact or recitals contained in this Agreement or in the certificates or entries in the Book Entry account system of the transfer agent for securities purchasable upon exercise of Rights or the Rights Certificates (except its countersignature thereof) or be required to verify the same, but all such statements and recitals are and will be deemed to have been made by the Company only.

(e) The Rights Agent will not be under any responsibility in respect of the validity of this Agreement or the execution and delivery hereof (except the due authorization, execution and delivery hereof by the Rights Agent) or in respect of the validity or execution of any certificate or entry in the Book Entry account system of the transfer agent for securities purchasable upon exercise of Rights or Rights Certificate (except its countersignature thereof); nor will it be responsible for any breach by the Company of any covenant or condition contained in this Agreement or in any Rights Certificate; nor will it be responsible for any change in the exercisability of the Rights (including the Rights becoming void pursuant to Section 3.1(b) hereof) or any adjustment required under the provisions of Section 2.4, 3.1 or 3.2 hereof or responsible for the manner, method or amount of any such adjustment or the ascertaining of the existence of facts that would require any such adjustment (except with respect to the exercise of Rights after receipt of the certificate or entry in the Book Entry account system of the transfer agent contemplated by Section 2.4 describing any such adjustment); nor will it by any act hereunder be deemed to make any representation or warranty as to the authorization or reservation of any securities purchasable upon exercise of Rights or any Rights or as to whether any securities purchasable upon exercise of Rights will, when issued, be duly and validly authorized, executed, issued and delivered and fully paid and nonassessable.

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(f) The Company agrees that it will perform, execute, acknowledge and deliver or cause to be performed, executed, acknowledged and delivered all such further and other acts, instruments and assurances as may reasonably be required by the Rights Agent for the carrying out or performing by the Rights Agent of the provisions of this Agreement.

(g) The Rights Agent is hereby authorized and directed to accept instructions with respect to the performance of its duties hereunder from any person believed by the Rights Agent to be the Chairman of the Board, the President or any Vice President or the Secretary or any Assistant Secretary or the Treasurer or any Assistant Treasurer of the Company, and to apply to such persons for advice or instructions in connection with its duties, and it shall not be liable for any action taken or suffered by it in good faith in accordance with instructions of any such person.

(h) The Rights Agent and any stockholder, director, officer or employee of the Rights Agent may buy, sell or deal in Common Stock, Rights or other securities of the Company or become pecuniarily interested in any transaction in which the Company may be interested, or contract with or lend money to the Company or otherwise act as fully and freely as though it were not Rights Agent under this Agreement. Nothing herein shall preclude the Rights Agent from acting in any other capacity for the Company or for any other legal entity.

(i) The Rights Agent may execute and exercise any of the rights or powers hereby vested in it or perform any duty hereunder either itself or by or through its attorneys or agents, and the Rights Agent will not be answerable or accountable for any act, default, neglect or misconduct of any such attorneys or agents or for any loss to the Company resulting from any such act, default, neglect or misconduct, provided reasonable care was exercised in the selection and continued employment thereof.

4.4 Change of Rights Agent.

The Rights Agent may resign and be discharged from its duties under this Agreement upon 90 days’ notice (or such lesser notice as is acceptable to the Company) in writing mailed to the Company and to each transfer agent of Common Stock by registered or certified mail, and to the holders of the Rights in accordance with Section 5.9. The Company may remove the Rights Agent upon thirty (30) days’ notice in writing, mailed to the Rights Agent and to each transfer agent of the Common Stock by registered or certified mail, and to the holders of the Rights in accordance with Section 5.9. If the Rights Agent should resign or be removed or otherwise become incapable of acting, the Company will appoint a successor to the Rights Agent. If the Company fails to make such appointment within a period of thirty (30) days after such removal or after it has been notified in writing of such resignation or incapacity by the resigning or incapacitated Rights Agent or by the holder of any Rights (which holder shall, with such notice, submit such holder’s Rights Certificate for inspection by the Company), then the holder of any Rights may apply to any court of competent jurisdiction for the appointment of a new Rights

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Agent. Any successor Rights Agent, whether appointed by the Company or by such a court, shall be (a) a legal business entity organized and doing business under the laws of the United States or any state of the United States, in good standing, which is authorized under such laws to exercise the powers of the Rights Agent contemplated by this Agreement and is subject to supervision or examination by federal or state authority and which has at the time of its appointment as Rights Agent a combined capital and surplus of at least $50,000,000 or (b) an affiliate of a legal business entity described in clause (a) of this sentence. After appointment, the successor Rights Agent will be vested with the same powers, rights, duties and responsibilities as if it had been originally named as Rights Agent without further act or deed; but the predecessor Rights Agent shall deliver and transfer to the successor Rights Agent any property at the time held by it hereunder, and execute and deliver any further assurance, conveyance, act or deed necessary for the purpose. Not later than the effective date of any such appointment, the Company will file notice thereof in writing with the predecessor Rights Agent and each transfer agent of the Common Stock, and mail a notice thereof in writing to the holders of the Rights. Failure to give any notice provided for in this Section 4.4, however, or any defect therein, shall not affect the legality or validity of the resignation or removal of the Rights Agent or the appointment of the successor Rights Agent, as the case may be.

ARTICLE V

MISCELLANEOUS

5.1 Redemption.

(a) The Board of Directors of the Company may, at its option, at any time prior to the earlier of (i) the Close of Business on the tenth Business Day following the Stock Acquisition Date (or, if the Stock Acquisition Date shall have occurred prior to the Record Time, the Close of Business on the tenth Business Day following the Record Time) or (ii) the twelve-month anniversary of the Record Time, elect to redeem all (but not less than all) the then outstanding Rights at the Redemption Price and the Company, at its option, may pay the Redemption Price either in cash or shares of Common Stock or other securities of the Company deemed by the Board of Directors, in the exercise of its sole discretion, to be at least equivalent in value to the Redemption Price. Notwithstanding anything herein to the contrary, the Rights shall not be exercisable after the first occurrence of an event described in Section 3.1(a) until such time as the Company’s right of redemption hereunder has expired. The redemption of the Rights by the action of the Board of Directors of the Company may be made effective at such time, on such basis and with such conditions as the Board of Directors of the Company in its sole discretion may establish.

(b) Immediately upon the action of the Board of Directors of the Company electing to redeem the Rights (or, if the resolution of the Board of Directors electing to redeem the Rights states that the redemption will not be effective until the occurrence of a specified future time or event, upon the occurrence of such future time or event), without any further action and without any notice, the right to exercise the Rights will terminate and each Right, whether or not previously exercised, will thereafter represent only the right to receive the Redemption Price in cash or securities, as determined by the Board of Directors. Promptly after the Rights are

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redeemed, the Company shall give notice of such redemption to the Rights Agent and the holders of the then outstanding Rights by mailing such notice in accordance with Section 5.9; provided, however, that the failure to give, or any defect in, any such notice shall not affect the validity of such redemption.

(c) Neither the Company nor any of its Affiliates or Associates may redeem, acquire or purchase for value any Rights at any time in any manner other than that specifically set forth in this Section 5.1 and other than in connection with the purchase or repurchase by any of them of Common Stock prior to the Separation Time.

5.2 Expiration.

The Rights and this Agreement shall expire at the Expiration Time and no Person shall have any rights pursuant to this Agreement or any Right after the Expiration Time, except, if the Rights are exchanged or redeemed, as provided in Section 3.1 or 5.1 hereof, respectively.

5.3 Issuance of New Rights Certificates.

Notwithstanding any of the provisions of this Agreement or of the Rights to the contrary, the Company may, at its option, issue new Rights Certificates evidencing Rights in such form as may be approved by its Board of Directors to reflect any adjustment or change in the number or kind or class of shares of stock purchasable upon exercise of Rights made in accordance with the provisions of this Agreement. In addition, in connection with the issuance or sale of shares of Common Stock by the Company following the Separation Time and prior to the Expiration Time (a) for any such issuance or sales made pursuant to the terms of securities convertible or redeemable into shares of Common Stock or to options, in each case issued or granted prior to, and outstanding at, the Separation Time, the Company shall issue to the holders of such shares of Common Stock, Rights Certificates representing the appropriate number of Rights in connection with the issuance or sale of such shares of Common Stock and (b) for any such issuance or sales made in any other case, the Company may, if deemed necessary or appropriate by the Board of Directors of the Company, issue Rights Certificates representing the appropriate number of Rights in connection with the issuance or sale of such shares of Common Stock; provided, however, in each case, (i) no such Rights Certificate shall be issued, if, and to the extent that, the Company shall be advised by counsel that such issuance would create a significant risk of material adverse tax consequences to the Company or to the Person to whom such Rights Certificates would be issued, (ii) no such Rights Certificates shall be issued if, and to the extent that, appropriate adjustment shall have otherwise been made in lieu of the issuance thereof, and (iii) the Company shall have no obligation to distribute Rights Certificates to any Acquiring Person or Affiliate or Associate of an Acquiring Person or any transferee of any of the foregoing.

5.4 Supplements and Amendments.

(a) The Company and the Rights Agent may from time to time supplement or amend this Agreement without the approval of any holders of Rights (i) prior to the Separation Time, in any respect and (ii) on or after the Separation Time, and subject to the provisions of Section 5.4(b)

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hereof, to make any changes that the Company may deem necessary or desirable (x) that shall not materially adversely affect the interests of the holders of Rights generally (other than the Acquiring Person or any Affiliate or Associate thereof), (y) in order to cure any ambiguity or to correct or supplement any provision contained herein which may be inconsistent with any other provisions herein or otherwise defective, including, without limitation, any change in order to satisfy any applicable law, rule or regulation, including any Trading Regulation on any applicable exchange so as to allow trading of the Company’s securities thereon, or (z) to shorten or lengthen any time period hereunder. Upon delivery of a certificate from an appropriate officer of the Company that states that the proposed supplement or amendment is in compliance with the terms of this Section 5.4(a), the Rights Agent will duly execute and deliver any supplement or amendment hereto requested by the Company which satisfies the terms of the preceding sentence or Section 2.4(b) or Section 3.2(a), provided that any supplement or amendment (other than to Article IV) shall become effective immediately upon execution by the Company, whether or not also executed by the Rights Agent. Prior to the Separation Time, the interests of the holders of Rights shall be deemed coincident with the interests of the holders of Common Stock.

(b) Notwithstanding anything herein to the contrary, no supplement or amendment shall be made to this Agreement at a time when the Rights are not redeemable, except as contemplated by clause (y) of Section 5.4(a) hereof.

5.5 Fractional Shares.

If the Company elects not to issue certificates representing fractional shares (other than fractions that are integral multiples of one one-hundredth of a share of Preferred Stock) upon exercise or redemption of Rights, the Company shall, in lieu thereof, in the sole discretion of the Board of Directors, (a) evidence such fractional shares by depositary receipts issued pursuant to an appropriate agreement between the Company and a depositary selected by it, providing that each holder of a depositary receipt shall have all of the rights, privileges and preferences to which such holder would be entitled as a beneficial owner of such fractional share, (b) evidence such fractional shares in accordance with the transfer agent’s Book Entry account system, or (c) pay to the registered holder of such Rights the appropriate fraction of the Market Price per share in cash.

5.6 Rights of Action.

Subject to the terms of this Agreement (including Sections 3.1(b), 5.10 and 5.14), rights of action in respect of this Agreement, other than rights of action vested solely in the Rights Agent, the Board of Directors of the Company or the Company, are vested in the respective holders of the Rights; and any holder of any Rights, without the consent of the Rights Agent or of the holder of any other Rights, may, on such holder’s own behalf and for such holder’s own benefit and the benefit of other holders of Rights, enforce, and may institute and maintain any suit, action or proceeding against the Company to enforce, or otherwise act in respect of, such holder’s right to exercise such holder’s Rights in the manner provided in such holder’s Rights Certificate and in this Agreement. Without limiting the foregoing or any remedies available to the holders of Rights, it is specifically acknowledged that the holders of Rights would not have an adequate remedy at law for any breach of this Agreement and will be entitled to specific performance of the obligations under, and injunctive relief against actual or threatened violations of, the obligations of any Person subject to this Agreement.

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5.7 Holder of Rights Not Deemed a Stockholder.

No holder, as such, of any Rights shall be entitled to vote, receive dividends or be deemed for any purpose the holder of shares or any other securities which may at any time be issuable on the exercise of such Rights, nor shall anything contained herein or in any Rights Certificate be construed to confer upon the holder of any Rights, as such, any of the rights of a stockholder of the Company or any right to vote for the election of directors or upon any matter submitted to stockholders at any meeting thereof, or to give or withhold consent to any corporate action, or to receive notice of meetings or other actions affecting stockholders (except as provided in Section 5.8 hereof), or to receive dividends or subscription rights, or otherwise, until such Rights shall have been exercised or exchanged in accordance with the provisions hereof.

5.8 Notice of Proposed Actions.

(a) In case the Company shall propose after the Separation Time and prior to the Expiration Time (i) to effect or permit a Flip-over Transaction or Event or (ii) to effect the liquidation, dissolution or winding up of the Company, then, in each such case, the Company shall give to each holder of a Right, in accordance with Section 5.9 hereof, a notice of such proposed action, which shall specify the date on which such Flip-over Transaction or Event, liquidation, dissolution, or winding up is to take place, and such notice shall be so given at least twenty (20) Business Days prior to the date of the taking of such proposed action.

(b) In the event that a Flip-in Date shall occur, the Company shall as soon as practicable thereafter give to each holder of a Rights Certificate, to the extent feasible and in accordance with Section 5.9 hereof, a notice of the occurrence of such event, which shall specify the event and the consequences of the event to holders of Rights under Section 3.1(a) hereof.

5.9 Notices.

Notices or demands authorized or required by this Agreement to be given or made by the Rights Agent or by the holder of any Rights to or on the Company shall be sufficiently given or made if delivered or sent by first-class mail, postage prepaid, addressed (until another address is filed in writing with the Rights Agent) as follows:

American Stock Transfer & Trust Company, LLC

▇▇▇▇ ▇▇^▇▇ ▇▇▇▇▇▇

▇▇▇▇▇▇▇▇, ▇▇ ▇▇▇▇▇

Attn: Client Administrator

with a copy, (which shall not constitute notice) to:

American Stock Transfer & Trust Company, LLC

▇▇▇▇ ▇▇^▇▇ ▇▇▇▇▇▇

▇▇▇▇▇▇▇▇, ▇▇ ▇▇▇▇▇

Attn: General Counsel

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Any notice or demand authorized or required by this Agreement to be given or made by the Company or by the holder of any Rights to or on the Rights Agent shall be sufficiently given or made if delivered or sent by first-class mail, postage prepaid, addressed (until another address is filed in writing with the Company) as follows:

Human Genome Sciences, Inc.

▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇

▇▇▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇▇ ▇▇▇▇▇-▇▇▇▇

Attention: General Counsel

Notices or demands authorized or required by this Agreement to be given or made by the Company or the Rights Agent to or on the holder of any Rights shall be sufficiently given or made if delivered or sent by first-class mail, postage prepaid, addressed to such holder at the address of such holder as it appears upon the registry books of the Rights Agent or, prior to the Separation Time, on the registry books of the transfer agent for the Common Stock. Any notice that is mailed in the manner herein provided shall be deemed given, whether or not the holder receives the notice.

5.10 Suspension of Exercisability or Exchangeability.

To the extent that the Board of Directors of the Company determines in good faith that some action will or need be taken pursuant to, or in order to properly give effect to, Section 2.3, 3.1 or 4.4 or to comply with federal or state securities laws or applicable Trading Regulations, the Company may suspend the exercisability or exchangeability of the Rights for a reasonable period sufficient to allow it to take such action or comply with such laws or Trading Regulations. In the event of any such suspension, the Company shall issue as promptly as practicable a public announcement stating that the exercisability or exchangeability of the Rights has been temporarily suspended. Notice thereof pursuant to Section 5.9 shall not be required. Upon such suspension, any rights of action vested in a holder of Rights shall be similarly suspended.

Failure to give a notice pursuant to the provisions of this Agreement shall not affect the validity of any action taken hereunder.

5.11 Costs of Enforcement.

The Company agrees that if the Company or any other Person the securities of which are purchasable upon exercise of Rights fails to fulfill any of its obligations pursuant to this Agreement, then the Company or such Person will reimburse the holder of any Rights for the costs and expenses (including legal fees) incurred by such holder in actions to enforce such holder’s rights pursuant to any Rights or this Agreement.

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5.12 Successors.

All the covenants and provisions of this Agreement by or for the benefit of the Company or the Rights Agent shall bind and inure to the benefit of their respective successors and assigns hereunder.

5.13 Benefits of this Agreement.

Nothing in this Agreement shall be construed to give to any Person other than the Company, the Rights Agent and the holders of the Rights any legal or equitable right, remedy or claim under this Agreement and this Agreement shall be for the sole and exclusive benefit of the Company, the Rights Agent and the holders of the Rights.

5.14 Determination and Actions by the Board of Directors, etc.

The Board of Directors of the Company shall have the exclusive power and authority to administer this Agreement and to exercise all rights and powers specifically granted to the Board or to the Company, or as may be necessary or advisable in the administration of this Agreement, including, without limitation, the right and power to (i) interpret the provisions of this Agreement and (ii) make all determinations deemed necessary or advisable for the administration or implementation of this Agreement, including the right to determine the Rights to be void pursuant to Section 3.1, after taking into account the purpose of this Agreement and the Company’s interest maintaining an orderly trading market in the outstanding shares of Common Stock. All such actions, interpretations and determinations (including, for purposes of clause (y) below, all omissions with respect to the foregoing) done or made by the Board of Directors of the Company (including by a committee of the Board to the extent permitted by applicable law), shall (x) be final, conclusive and binding on the Company, the Rights Agent, the holders of the Rights and all other Persons, and (y) not subject the Board of Directors of the Company or any of the directors on the Board of Directors of the Company to any liability to the holders of the Rights.

5.15 Descriptive Headings.

Descriptive headings appear herein for convenience only and shall not control or affect the meaning or construction of any of the provisions hereof.

5.16 Governing Law.

THIS AGREEMENT AND EACH RIGHT ISSUED HEREUNDER SHALL BE DEEMED TO BE A CONTRACT MADE UNDER THE LAWS OF THE STATE OF DELAWARE AND FOR ALL PURPOSES SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF SUCH STATE APPLICABLE TO CONTRACTS TO BE MADE AND PERFORMED ENTIRELY WITHIN SUCH STATE.

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5.17 Counterparts.

This Agreement may be executed in any number of counterparts and each of such counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument.

5.18 Severability.

If any term or provision hereof or the application thereof to any circumstance shall, in any jurisdiction and to any extent, be invalid or unenforceable, such term or provision shall be ineffective as to such jurisdiction to the extent of such invalidity or unenforceability without invalidating or rendering unenforceable the remaining terms and provisions hereof or the application of such term or provision to circumstances other than those as to which it is held invalid or unenforceable; provided, however, that notwithstanding anything in this Agreement to the contrary, if any such term, provision, covenant or restriction is held by such court or authority to be invalid, void or unenforceable and the Board of Directors of the Company determines in its good faith judgment that severing the invalid language from this Agreement would adversely affect the purpose or effect of this Agreement, the right of redemption set forth in Section 5.1 hereof shall be reinstated and shall not expire until the Close of Business on the tenth Business Day following the date of such determination by the Board of Directors of the Company.

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IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly executed as of the date first above written.


“COMPANY”	Human Genome Sciences, Inc.

	By:	/s/ H. ▇▇▇▇▇▇ ▇▇▇▇▇▇▇
	Name:	H. ▇▇▇▇▇▇ ▇▇▇▇▇▇▇
	Title:	President and Chief Executive Officer

“RIGHTS AGENT”	American Stock Transfer & Trust Company, LLC

	By:	/s/ ▇▇▇▇▇ Caroppoll
	Name:	▇▇▇▇▇ Caroppoll
	Title:	Senior Vice President

EXHIBIT A

[Form of Rights Certificate]

Certificate No. W- Rights

NOT EXERCISABLE AFTER May 29, 2013 OR SUCH EARLIER DATE AS THE RIGHTS ARE REDEEMED, EXCHANGED OR TERMINATED. THE RIGHTS ARE SUBJECT TO REDEMPTION OR MANDATORY EXCHANGE, AT THE OPTION OF THE COMPANY, ON THE TERMS SET FORTH IN THE RIGHTS AGREEMENT. RIGHTS BENEFICIALLY OWNED BY ACQUIRING PERSONS OR AFFILIATES OR ASSOCIATES THEREOF (AS SUCH TERMS ARE DEFINED IN THE RIGHTS AGREEMENT) OR TRANSFEREES OF ANY OF THE FOREGOING WILL BE VOID.

Rights Certificate

Human Genome Sciences, Inc.

This certifies that , or registered assigns, is the registered holder of the number of Rights set forth above, each of which entitles the registered holder thereof, subject to the terms, provisions and conditions of the Rights Agreement, dated as of May 16, 2012 (as amended from time to time, the “Rights Agreement”), between Human Genome Sciences, Inc., a Delaware corporation (the “Company”), and American Stock Transfer & Trust Company, a New York corporation, as Rights Agent (the “Rights Agent”, which term shall include any successor Rights Agent under the Rights Agreement), to purchase from the Company at any time after the Separation Time (as such term is defined in the Rights Agreement) and prior to the close of business on May 29, 2013 one one-hundredth of a fully paid share of Series A Junior Participating Preferred Stock, par value $0.01 per share (the “Preferred Stock”), of the Company (subject to adjustment as provided in the Rights Agreement) at the Exercise Price referred to below, upon presentation and surrender of this Rights Certificate with the Form of Election to Exercise duly executed at the principal office of the Rights Agent in The City of New York. The Exercise Price shall initially be $37.50 per Right and shall be subject to adjustment in certain events as provided in the Rights Agreement.

In certain circumstances described in the Rights Agreement, the Rights evidenced hereby may entitle the registered holder thereof to purchase securities of an entity other than the Company or securities of the Company other than Preferred Stock or assets of the Company, all as provided in the Rights Agreement.

A - 1

This Rights Certificate is subject to all of the terms, provisions and conditions of the Rights Agreement, which terms, provisions and conditions are hereby incorporated herein by reference and made a part hereof and to which Rights Agreement reference is hereby made for a full description of the rights, limitations of rights, obligations, duties and immunities hereunder of the Rights Agent, the Company and the holders of the Rights Certificates. Copies of the Rights Agreement are on file at the principal office of the Company and are available without cost upon written request.

This Rights Certificate, with or without other Rights Certificates, upon surrender at the office of the Rights Agent designated for such purpose, may be exchanged for another Rights Certificate or Rights Certificates of like tenor evidencing an aggregate number of Rights equal to the aggregate number of Rights evidenced by the Rights Certificate or Rights Certificates surrendered. If this Rights Certificate shall be exercised in part, the registered holder shall be entitled to receive, upon surrender hereof, another Rights Certificate or Rights Certificates for the number of whole Rights not exercised.

Subject to the provisions of the Rights Agreement, each Right evidenced by this Certificate may be (a) redeemed by the Company under certain circumstances, at its option, at a redemption price of $0.01 per Right or (b) exchanged by the Company under certain circumstances, at its option, for one share of Common Stock or one one hundredth of a share of Preferred Stock per Right (or, in certain cases, other securities or assets of the Company), subject in each case to adjustment in certain events as provided in the Rights Agreement.

No holder of this Rights Certificate, as such, shall be entitled to vote or receive dividends or be deemed for any purpose the holder of any securities which may at any time be issuable on the exercise hereof, nor shall anything contained in the Rights Agreement or herein be construed to confer upon the holder hereof, as such, any of the rights of a stockholder of the Company or any right to vote for the election of directors or upon any matter submitted to stockholders at any meeting thereof, or to give or withhold consent to any corporate action, or to receive notice of meetings or other actions affecting stockholders (except as provided in the Rights Agreement), or to receive dividends or subscription rights, or otherwise, until the Rights evidenced by this Rights Certificate shall have been exercised or exchanged as provided in the Rights Agreement.

This Rights Certificate shall not be valid or obligatory for any purpose until it shall have been countersigned by the Rights Agent.

A - 2

WITNESS the facsimile signature of the proper officers of the Company and its corporate seal.


Date:

ATTEST:						Human Genome Sciences, Inc.

						By:
Secretary

Countersigned:

By:
Authorized Signature

A - 3

[Form of Reverse Side of Rights Certificate]

FORM OF ASSIGNMENT

(To be executed by the registered holder if such

holder desires to transfer this Rights Certificate.)

FOR VALUE RECEIVED hereby sells, assigns and transfers unto

(Please print name and address of transferee)

this Rights Certificate, together with all right, title and interest therein, and does hereby irrevocably constitute and appoint Attorney, to transfer the within Rights Certificate on the books of the within-named Company, with full power of substitution.


Dated:

Signature Guaranteed:

Signature

(Signature must correspond to name as written upon the face of this Rights Certificate in every particular, without alteration or enlargement or any change whatsoever)

A - 4

Signatures must be guaranteed by an eligible guarantor institution (banks, stockbrokers, savings and loan associations and credit unions with membership in an approved signature guarantee Medallion program), pursuant to Exchange Act Rule 17Ad-15.

(To be completed if true)

The undersigned hereby represents, for the benefit of all holders of Rights and shares of Common Stock, that the Rights evidenced by this Rights Certificate are not, and, to the knowledge of the undersigned, have never been, Beneficially Owned by an Acquiring Person or an Affiliate or Associate thereof (as defined in the Rights Agreement).

Signature

NOTICE

In the event the certification set forth above is not completed in connection with a purported assignment, the Company will deem the Beneficial Owner of the Rights evidenced by the enclosed Rights Certificate to be an Acquiring Person or an Affiliate or Associate thereof (as defined in the Rights Agreement) or a transferee of any of the foregoing and accordingly will deem the Rights evidenced by such Rights Certificate to be void and not transferable or exercisable.

A - 5

[To be attached to each Rights Certificate]

FORM OF ELECTION TO EXERCISE

(To be executed if holder desires to

exercise the Rights Certificate.)

TO:	HUMAN GENOME SCIENCES, INC.

The undersigned hereby irrevocably elects to exercise whole Rights represented by the attached Rights Certificate to purchase the shares of Series A Junior Participating Preferred Stock issuable upon the exercise of such Rights and requests that certificates for such shares be issued, or book entries in the Book Entry account system of the transfer agent be made, in the name of:



Address:


Social Security or Other Taxpayer
Identification Number:

If such number of Rights shall not be all the Rights evidenced by this Rights Certificate, a new Rights Certificate for the balance of such Rights shall be registered in the name of and delivered to:



Address:


Social Security or Other Taxpayer
Identification Number:


Dated:

Signature Guaranteed:

Signature

(Signature must correspond to name as written upon the face of this Rights Certificate in every particular, without alteration or enlargement or any change whatsoever)

A - 6

(To be completed if true)

Signature

NOTICE

A - 7

EXHIBIT B

FORM OF CERTIFICATE OF DESIGNATION, PREFERENCES AND RIGHTS

OF SERIES A JUNIOR PARTICIPATING PREFERRED STOCK

HUMAN GENOME SCIENCES, INC.

Human Genome Sciences, Inc., a Delaware corporation having its principal office in Rockville, Maryland (the “Corporation”), hereby certifies to the Delaware Secretary of State that:

FIRST: Pursuant to the authority expressly vested in the Board of Directors of the Corporation by the Certificate of Incorporation of the Corporation, the Board of Directors has duly reclassified 4,000,000 shares of the undesignated Preferred Stock (par value $0.01 per share) of the Corporation into 4,000,000 shares of a class designated as Series A Junior Participating Preferred Stock (par value $0.01 per share) of the Corporation (hereinafter called this “Series”) and has provided for the issuance of such shares.

SECOND: The following is a description of the preferences and other rights, voting powers, restrictions, qualifications, terms and conditions of the Series A Junior Participating Preferred Stock of the Corporation.

(i) The designation of the Series A Junior Participating Preferred Stock described in Article FIRST hereof shall be “Preferred Stock.” Each share of this Series shall be identical in all respects with the other shares of this Series except as to the dates from and after which dividends thereon shall be cumulative.

(ii) The number of shares in this Series shall initially be 4,000,000, which number may from time to time be increased or decreased (but not below the number then outstanding) by the Board of Directors. Shares of this Series purchased by the Corporation shall be cancelled and shall revert to authorized but unissued shares of Preferred Stock undesignated as to series. Shares of this Series may be issued in fractional shares, which fractional shares shall entitle the holder, in proportion to such holder’s fractional share, to all rights of a holder of a whole share of this Series.

(iii) The holders of full or fractional shares of this Series shall be entitled to receive, when and as declared by the Board of Directors, but only out of funds legally available therefor, dividends, (A) on each date that dividends or other distributions (other than dividends or distributions payable in Common Stock of

B - 1

the Corporation) are payable on or in respect of Common Stock comprising part of the Reference Package (as defined below), in an amount per whole share of this Series equal to the aggregate amount of dividends or other distributions (other than dividends or distributions payable in Common Stock of the Corporation) that would be payable on such date to a holder of the Reference Package and (B) on the last day of March, June, September and December in each year, in an amount per whole share of this Series equal to the excess (if any) of $0.09375 over the aggregate dividends paid per whole share of this Series during the three month period ending on such last day. Each such dividend shall be paid to the holders of record of shares of this Series on the date, not exceeding sixty days preceding such dividend or distribution payment date, fixed for the purpose by the Board of Directors in advance of payment of each particular dividend or distribution. Dividends on each full and each fractional share of this Series shall be cumulative from the date such full or fractional share is originally issued; provided that any such full or fractional share originally issued after a dividend record date and on or prior to the dividend payment date to which such record date relates shall not be entitled to receive the dividend payable on such dividend payment date or any amount in respect of the period from such original issuance to such dividend payment date.

The term “Reference Package” shall initially mean 100 shares of Common Stock, par value $0.01 per share (“Common Stock”), of the Corporation. In the event the Corporation shall at any time after the close of business on May 29, 2012 (A) declare or pay a dividend on any Common Stock payable in Common Stock, (B) subdivide any Common Stock or (C) combine any Common Stock into a smaller number of shares, then and in each such case the Reference Package after such event shall be the Common Stock that a holder of the Reference Package immediately prior to such event would hold thereafter as a result thereof.

Holders of shares of this Series shall not be entitled to any dividends, whether payable in cash, property or stock, in excess of full cumulative dividends, as herein provided on this Series.

So long as any shares of this Series are outstanding, no dividend (other than a dividend in Common Stock or in any other stock ranking junior to this Series as to dividends and upon liquidation) shall be declared or paid or set aside for payment or

B - 2

other distribution declared or made upon the Common Stock or upon any other stock ranking junior to this Series as to dividends or upon liquidation, nor shall any Common Stock nor any other stock of the Corporation ranking junior to or on a parity with this Series as to dividends or upon liquidation be redeemed, purchased or otherwise acquired for any consideration (or any moneys be paid to or made available for a sinking fund for the redemption of any shares of any such stock) by the Corporation (except by conversion into or exchange for stock of the Corporation ranking junior to this Series as to dividends and upon liquidation), unless, in each case, the full cumulative dividends (including the dividend to be due upon payment of such dividend, distribution, redemption, purchase or other acquisition) on all outstanding shares of this Series shall have been, or shall contemporaneously be, paid.

(iv) In the event of any merger, consolidation, reclassification or other transaction in which the shares of Common Stock are exchanged for or changed into other stock or securities, cash and/or any other property, then in any such case the shares of this Series shall at the same time be similarly exchanged or changed in an amount per whole share equal to the aggregate amount of stock, securities, cash and/or any other property (payable in kind), as the case may be, that a holder of the Reference Package would be entitled to receive as a result of such transaction.

(v) In the event of any liquidation, dissolution or winding up of the affairs of the Corporation, whether voluntary or involuntary, the holders of full and fractional shares of this Series shall be entitled, before any distribution or payment is made on any date to the holders of the Common Stock or any other stock of the Corporation ranking junior to this Series upon liquidation, to be paid in full an amount per whole share of this Series equal to the greater of (A) $3,750 or (B) the aggregate amount distributed or to be distributed prior to such date in connection with such liquidation, dissolution or winding up to a holder of the Reference Package (such greater amount being hereinafter referred to as the “Liquidation Preference”), together with accrued dividends to such distribution or payment date, whether or not earned or declared. If such payment shall have been made in full to all holders of shares of this Series, the holders of shares of this Series as such shall have no right or claim to any of the remaining assets of the Corporation.

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In the event the assets of the Corporation available for distribution to the holders of shares of this Series upon any liquidation, dissolution or winding up of the Corporation, whether voluntary or involuntary, shall be insufficient to pay in full all amounts to which such holders are entitled pursuant to the first paragraph of this Section (v), no such distribution shall be made on account of any shares of any other class or series of Preferred Stock ranking on a parity with the shares of this Series upon such liquidation, dissolution or winding up unless proportionate distributive amounts shall be paid on account of the shares of this Series, ratably in proportion to the full distributable amounts for which holders of all such parity shares are respectively entitled upon such liquidation, dissolution or winding up.

Upon the liquidation, dissolution or winding up of the Corporation, the holders of shares of this Series then outstanding shall be entitled to be paid out of assets of the Corporation available for distribution to its stockholders all amounts to which such holders are entitled pursuant to the first paragraph of this Section (v) before any payment shall be made to the holders of Common Stock or any other stock of the Corporation ranking junior upon liquidation to this Series.

For the purposes of this Section (v), the consolidation or merger of, or binding share exchange by, the Corporation with any other corporation shall not be deemed to constitute a liquidation, dissolution or winding up of the Corporation.

(vi) The shares of this Series shall not be redeemable.

(vii) In addition to any other vote or consent of stockholders required by law or by the Certificate of Incorporation of the Corporation, each whole share of this Series shall, on any matter, vote as a class with any other capital stock comprising part of the Reference Package and voting on such matter and shall have the number of votes thereon that a holder of the Reference Package would have.

(viii) In the event any shares of this Series shall be reacquired, the shares so reacquired shall revert to the status of authorized but unissued shares of this Series available for future issuance and reclassification by the Corporation.

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IN WITNESS WHEREOF, the undersigned has executed and subscribed this Certificate and does affirm the foregoing as true under the penalties of perjury this day of , 20 .

[Name], [Title]

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RIGHTS AGREEMENT dated as of May 16, 2012 between HUMAN GENOME SCIENCES, INC. and AMERICAN STOCK TRANSFER & TRUST COMPANY, LLC as Rights Agent

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