AGREEMENT AND PLAN OF MERGER among: TRIUS THERAPEUTICS, INC., a Delaware corporation; CUBIST PHARMACEUTICALS, INC., a Delaware corporation; and BRGO CORPORATION, a Delaware corporation Dated as of July 30, 2013

(A) all “Material Adverse Effect” qualifications and other materiality qualifications contained in such representations and warranties shall be disregarded, (B) any update of or modification to the Company Disclosure Schedule made or purported to have been made after the date of the Agreement shall be disregarded and (C) the truth and correctness of those representations or warranties that address matters only as of a specific date shall be measured (subject to the applicable materiality standard as set forth in this clause (b)(ii)) only as of such date);

(iii)                               the representations and warranties of the Company set forth in Section 3.5(b) (Absence of Changes — No Material Adverse Effect) shall have been accurate in all respects as of the date of the Agreement and shall be accurate in all respects at and as of the Offer Acceptance Time as if made on and as of such Closing Date (it being understood that any update of or modification to the Company Disclosure Schedule made or purported to have been made after the date of the Agreement shall be disregarded);

(iv)                              the representations and warranties of the Company set forth in the Agreement (other than those referred to in clauses “(i)”, “(ii)” or “(iii)” above) shall have been accurate in all respects as of the date of the Agreement, and shall be accurate in all respects at and as of the Offer Acceptance Time as if made on and as of such date, except that any inaccuracies in such representations and warranties will be disregarded if the circumstances giving rise to all such inaccuracies (considered collectively) do not constitute, and would not reasonably be expected to have, a Material Adverse Effect (it being understood that, for purposes of determining the accuracy of such representations and warranties, (A) all “Material Adverse Effect” qualifications and other materiality qualifications contained in such representations and warranties shall be disregarded, (B) any update of or modification to the Company Disclosure Schedule made or purported to have been made after the date of the Agreement shall be disregarded and (C) the truth and correctness of those representations or warranties that address matters only as of a specific date shall be measured (subject to the applicable materiality standard as set forth above) only as of such date);

(c)                                  the Company shall have complied with or performed in all material respects all of the Company’s covenants and agreements it is required to comply with or perform at or prior to the Offer Acceptance Time;

(d)                                 since the date hereof, there shall not have been any Company Material Adverse Effect that shall be continuing as of the Offer Acceptance Time;

(e)                                  the waiting period (or any extension thereof) applicable to the Offer under the HSR Act shall have expired or been terminated;

(f)                                   Parent and Purchaser shall have received a certificates executed on behalf of the Company by the Company’s Chief Executive Officer and Chief Financial Officer confirming that the conditions set forth in clauses “(b),” “(c)” and “(d)” of this Annex I have been duly satisfied;

(g)                                  there shall not have been issued by any court of competent jurisdiction or remain in effect any temporary restraining order, preliminary or permanent injunction or other order preventing the acquisition of or payment for Shares pursuant to the Offer nor shall any action

have been taken, or any Legal Requirement or order promulgated, entered, enforced, enacted, issued or deemed applicable to the Offer or the Merger by any Governmental Body which directly or indirectly prohibits, or makes illegal, the acquisition of or payment for Shares pursuant to the Offer, or the consummation of the Merger; provided, however, that Parent and Purchaser shall not be permitted to invoke this clause “(g)” unless they shall have taken all actions required under this Agreement to have any such order lifted;

(h)                                 there shall not be pending any Legal Proceeding by a Governmental Body having authority over Parent, Purchaser or the Company (1) challenging or seeking to restrain or prohibit the consummation of the Offer or the Merger, (2) seeking to restrain or prohibit Parent’s or its Affiliates ownership or operation of the business of the Company, or of Parent or Affiliates, or to compel Parent or any of its Affiliates to dispose of or hold separate all or any portion of the business or assets of the Company or of Parent or its Affiliates or (3) seeking to impose or confirm material limitations on the ability of Parent or any of its Affiliates effectively to exercise full rights of ownership of the Shares;

(i)                                     the Agreement shall not have been terminated in accordance with its terms.

The foregoing conditions are for the sole benefit of Parent and Purchaser and (except for the Minimum Condition) may be waived by Parent and Purchaser, in whole or in part at any time and from time to time, in the sole discretion of Parent and Purchaser. The failure by Parent or Purchaser at any time to exercise any of the foregoing rights shall not be deemed a waiver of any such right and each such right shall be deemed an ongoing right which may be asserted at any time and from time to time.

ANNEX II

FORM OF TENDER AND VOTING AGREEMENT

TENDER AND VOTING AGREEMENT

THIS TENDER AND VOTING AGREEMENT (this “Agreement”) dated July 30, 2013, is entered into between Cubist Pharmaceuticals, Inc., a Delaware corporation (“Parent”), BRGO Corporation, a Delaware corporation and direct or indirect wholly owned subsidiary of Parent (“Purchaser”), and [                                                  ] (“Stockholder”), with respect to (i) the shares of common stock, par value $0.0001 per share (the “Shares”), of Trius Therapeutics, Inc., a Delaware corporation (the “Company”), (ii) all securities exchangeable, exercisable or convertible into Shares, and (iii) any securities issued or exchanged with respect to such Shares, and upon any recapitalization, reclassification, merger, consolidation, spin-off, partial or complete liquidation, stock dividend, split-up or combination of the securities of the Company or upon any other change in the Company’s capital structure, in each case whether now owned or hereafter acquired by the  Stockholder (collectively, the “Securities”).

W I T N E S S E T H:

WHEREAS, Parent, Purchaser and the Company have entered into an Agreement and Plan of Merger dated as of the date hereof (as the same may be amended or supplemented, other than to lower the price to be paid in the Offer or Merger, the “Merger Agreement”) pursuant to which Purchaser has agreed to make a cash tender offer described therein and thereafter merge with and into the Company (the “Merger”) with the result that the Company becomes a wholly owned subsidiary of Parent;

WHEREAS, as of the date hereof, Stockholder beneficially owns and has the power to dispose of the Securities set forth on Schedule I hereto and has the power to vote the Shares set forth thereon;

WHEREAS, Parent and Purchaser desire to enter into this Agreement in connection with their efforts to consummate the acquisition of the Company;

WHEREAS, capitalized terms used in this Agreement and not defined have the meaning given to such terms in the Merger Agreement.

NOW, THEREFORE, in contemplation of the foregoing and in consideration of the mutual agreements, covenants, representations and warranties contained herein and intending to be legally bound hereby, the parties hereto agree as follows:

1.                                      Certain Covenants.

1.1                               Lock-Up.  Subject to Section 1.5, except as contemplated by the Merger Agreement, Stockholder hereby covenants and agrees that between the date hereof and the Termination Date, Stockholder will not (a) directly or indirectly, sell, transfer, assign, pledge, hypothecate, tender, encumber or otherwise dispose of or limit its right to vote in any manner any of the Securities, or agree to do any of the foregoing, or (b) take any action which would

have the effect of preventing or disabling Stockholder from performing its obligations under this Agreement.  Notwithstanding the foregoing, in connection with any transfer not involving or relating to any Acquisition Proposal (as defined in the Merger Agreement), Stockholder may transfer any or all of the Securities as follows: (i) in the case of a Stockholder that is an entity, to any parent entity, subsidiary or affiliate under common control with such Stockholder, or to a partner or member of Stockholder, and (ii) in the case of a Stockholder that is an individual, to Stockholder’s spouse, ancestors, descendants or any trust for any of their benefits or to a charitable trust; provided, however, that in any such case, prior to and as a condition to the effectiveness of such transfer, (x) each person to which any of such Securities or any interest in any of such Securities is or may be transferred shall have executed and delivered to Parent and Purchaser a counterpart to this Agreement pursuant to which such person shall be bound by all of the terms and provisions of this Agreement, and (y) this Agreement shall be the legal, valid and binding agreement of such person, enforceable against such person in accordance with its terms.

1.2                               RESERVED

1.3                               Certain Events.  This Agreement and the obligations hereunder will attach to the Securities and will be binding upon any person to which legal or beneficial ownership of any or all of the Securities passes, whether by operation of Law or otherwise, including without limitation, Stockholder’s successors or assigns.  This Agreement and the obligations hereunder will also attach to any additional Shares or other Securities of the Company issued to or acquired by Stockholder.

1.4                               Grant of Proxy; Voting Agreement.

(a)                                 The Stockholder has revoked or terminated any proxies, voting agreements or similar arrangements previously given or entered into with respect to the Securities and hereby irrevocably appoints Parent as proxy for Stockholder to vote the Securities for Stockholder and in Stockholder’s name, place and stead, at any annual or special meeting, or at any adjournment thereof or pursuant to any consent of the holders of the Shares, in lieu of a meeting or otherwise, whether before or after the Acceptance Time (as defined in the Merger Agreement), for the adoption of the Merger Agreement and against any Acquisition Proposal.  Stockholder may vote the Securities in its sole discretion on all other matters not referred to in this Section 1.4(a), and Parent may not exercise this proxy with respect to such other matters. The parties acknowledge and agree that neither Parent, nor Parent’s successors, assigns, subsidiaries, divisions, employees, officers, directors, stockholders, agents and affiliates shall owe any duty to, whether in law or otherwise, or incur any liability of any kind whatsoever, including without limitation, with respect to any and all claims, losses, demands, causes of action, costs, expenses (including reasonable attorney’s fees) and compensation of any kind or nature whatsoever to Stockholder in connection with or as a result of any voting by Parent of the Securities or any execution of any consent in accordance with this Section 1.4(a).  The parties acknowledge that, pursuant to the authority hereby granted under the irrevocable proxy, Parent may vote the Securities in furtherance of its own interests, and Parent is not acting as a fiduciary for Stockholder.

(b)                                 Notwithstanding the foregoing grant to Parent of the irrevocable proxy, if Parent elects not to exercise its rights to vote the Securities pursuant to the irrevocable

proxy, Stockholder agrees to vote the Securities during the term of this Agreement in favor of or give its consent to, as applicable, a proposal to adopt the Merger Agreement and otherwise as described in Section 1.4(a) at any annual or special meeting or action of the holders of the Shares in lieu of a meeting or otherwise.

(c)                                  This irrevocable proxy shall not be terminated by any act of Stockholder or by operation of law, whether by the death or incapacity of Stockholder or by the occurrence of any other event or events (including, without limiting the foregoing, the termination of any trust or estate for which Stockholder is acting as a fiduciary or fiduciaries or the dissolution or liquidation of any corporation or partnership).  If between the execution hereof and the Termination Date, Stockholder should die or become incapacitated, or if any trust or estate holding the Securities should be terminated, or if any corporation or partnership holding the Securities should be dissolved or liquidated, or if any other such similar event or events shall occur before the Termination Date, certificates representing the Securities shall be delivered by or on behalf of Stockholder in accordance with the terms and conditions of the Merger Agreement and this Agreement, and actions taken by Parent hereunder shall be as valid as if such death, incapacity, termination, dissolution, liquidation or other similar event or events had not occurred, regardless of whether or not Parent has received notice of such death, incapacity, termination, dissolution, liquidation or other event.

(d)                                 The irrevocable proxy granted pursuant to this Section 1.4 will terminate on the Termination Date.

1.5                               Tender of Securities.  Stockholder agrees, in exchange for the consideration described in the Merger Agreement, to tender the Shares beneficially owned as of the date hereof and set forth on Schedule I hereto to Purchaser in the Offer as soon as practicable following the commencement of the Offer, and in any event not later than ten (10) business days following the commencement of the Offer, or if Stockholder has not received the Offer Documents by such time, within two (2) business days following Stockholder’s receipt of such Offer Documents but in any event prior to the Expiration Date. Unless this Agreement has been terminated in accordance with its terms, Stockholder shall not withdraw any such Shares so tendered unless the Offer is terminated.

1.6                               RESERVED

1.7                               Public Announcement.  Stockholder shall consult with Parent before issuing any press releases or otherwise making any public statements with respect to the transactions contemplated herein and shall not issue any such press release or make any such public statement without the approval of Parent, except as may be required by Law, including any filings with the Securities and Exchange Commission (the “SEC”) pursuant to the Securities Exchange Act of 1934, as amended (the “Exchange Act”).  This Section 1.6 shall terminate and be null and void upon the earlier of (i) the Termination Date and (ii) consummation of the Merger.

1.8                               Disclosure.  Stockholder hereby authorizes Parent and Purchaser to publish and disclose in any announcement or disclosure required by the SEC, The Nasdaq Stock Market or any other national securities exchange and in the Offer Documents and, if necessary,

the Proxy Statement (each as defined in the Merger Agreement), (including all documents and schedules filed with the SEC in connection with either of the foregoing), its identity and ownership of the Securities and the nature of its commitments, arrangements and understandings under this Agreement.  Parent and Purchaser hereby authorize Stockholder to make such disclosure or filings as may be required by the SEC or The Nasdaq Stock Market or any other national securities exchange.

2.                                      Representations and Warranties of Stockholder.  Stockholder hereby represents and warrants to Parent and Purchaser, as of the date hereof, that:

2.1                               Ownership.  Stockholder has good and marketable title to, and is the sole legal and beneficial owner of, the Securities set forth on Schedule I hereto, in each case free and clear of all liabilities, claims, liens, options, proxies, charges, participations and encumbrances of any kind or character whatsoever, other than those arising under the securities laws or under the Company’s governance documents or under any registration rights agreement between the Company and Stockholder (collectively, “Liens”).  At the time Purchaser purchases the Shares pursuant to the Offer, Stockholder will transfer and convey to Parent or its designee good and marketable title to the Shares included in the Securities, free and clear of all Liens created by or arising through Stockholder.

2.2                               Authorization.  Stockholder has all requisite power and authority to execute and deliver this Agreement and to consummate the transactions contemplated hereby and has sole voting power and sole power of disposition, with respect to the Securities with no restrictions on its voting rights or rights of disposition pertaining thereto.  Stockholder has duly executed and delivered this Agreement and this Agreement is a legal, valid and binding agreement of Stockholder, enforceable against Stockholder in accordance with its terms, subject to (i) laws of general application relating to bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other laws affecting enforcement of creditors’ rights generally and (ii) rules of law governing specific performance, injunctive relief and other equitable remedies.  If Stockholder is married and the Securities constitute community property, this Agreement has been duly authorized, executed and delivered by Stockholder’s spouse, and this Agreement is a legal, valid and binding agreement of Stockholder’s spouse, enforceable against Stockholder’s spouse in accordance with its terms, subject to (i) laws of general application relating to bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other laws affecting enforcement of creditors’ rights generally and (ii) rules of law governing specific performance, injunctive relief and other equitable remedies.

2.3                               No Violation.  Neither the execution and delivery of this Agreement nor the consummation of the transactions contemplated hereby will (a) require Stockholder to file or register with, or obtain any permit, authorization, consent or approval of, any governmental agency, authority, administrative or regulatory body, court or other tribunal, foreign or domestic, or any other entity other than filings with the SEC pursuant to the Exchange Act, or (b) violate, or cause a breach of or default under, or conflict with any contract, agreement or understanding, any Law binding upon Stockholder, except for such violations, breaches, defaults or conflicts which are not, individually or in the aggregate, reasonably likely to have a material adverse effect on Stockholder’s ability to satisfy its obligations under this Agreement.  No proceedings are pending which, if adversely determined, will have an adverse effect on Stockholder’s ability

to vote or dispose of any of the Securities. The Stockholder has not previously assigned or sold any of the Securities set forth on Schedule I hereto to any third party.

2.4                               Stockholder Has Adequate Information.  Stockholder is a sophisticated seller with respect to the Securities and has adequate information concerning the business and financial condition of the Company to make an informed decision regarding the sale of the Securities and has independently and without reliance upon either Purchaser or Parent and based on such information as Stockholder has deemed appropriate, made its own analysis and decision to enter into this Agreement.  Stockholder acknowledges that neither Purchaser nor Parent has made and neither makes any representation or warranty, whether express or implied, of any kind or character except as expressly set forth in this Agreement.  Stockholder acknowledges that the agreements contained herein with respect to the Securities by Stockholder are irrevocable (prior to the Termination Date), and that Stockholder shall have no recourse to the Securities, Parent or Purchaser, except with respect to breaches of representations, warranties, covenants and agreements expressly set forth in this Agreement.

2.5                               No Setoff.  There are no legal or equitable defenses or counterclaims that have been asserted by or on behalf of the Company or Stockholder to reduce the amount of the Securities or affect the validity or enforceability of the Securities.

3.                                      Representations and Warranties of Parent and Purchaser.  Parent and Purchaser hereby represent and warrant to Stockholder, as of the date hereof, that:

3.1                               Authorization.  Parent and Purchaser have all requisite corporate power and authority to execute and deliver this Agreement and to consummate the transactions contemplated hereby.  Parent and Purchaser have duly executed and delivered this Agreement and this Agreement is a legal, valid and binding agreement of each of Parent and Purchaser, enforceable against each of Parent and Purchaser in accordance with its terms.

3.2                               No Violation. Neither the execution and delivery of this Agreement nor the consummation of the transactions contemplated hereby will violate, or cause a breach of or default under, any contract or agreement, any statute or law, or any judgment, decree, order, regulation or rule of any governmental agency, authority, administrative or regulatory body, court or other tribunal, foreign or domestic, or any other entity or any arbitration award binding upon Parent or Purchaser, except for such violations, breaches or defaults which are not reasonably likely to have a material adverse effect on either Parent’s or Purchaser’s ability to satisfy its obligations under this Agreement.

4.                                      Survival of Representations and Warranties.  The respective representations and warranties of Stockholder, Parent and Purchaser contained herein shall not be deemed waived or otherwise affected by any investigation made by the other party hereto.  The representations and warranties contained herein shall not survive the Termination Date, subject to Section 6.1.

5.                                      Specific Performance.  Stockholder acknowledges that Purchaser and Parent will be irreparably harmed and that there will be no adequate remedy at law for a violation of any of the covenants or agreements of Stockholder which are contained in this Agreement.  It is accordingly agreed that, in addition to any other remedies which may be available to Purchaser

and Parent upon the breach by Stockholder of such covenants and agreements, Purchaser and Parent shall have the right to obtain injunctive relief to restrain any breach or threatened breach of such covenants or agreements or otherwise to obtain specific performance of any of such covenants or agreements.

6.                                      Miscellaneous.

6.1                               Term.  This Agreement and all obligations hereunder shall terminate upon the earlier of (i) the day after the Merger is consummated, (ii) the End Date (as defined in the Merger Agreement), (iii) the date of any modification, waiver or amendment to the Merger Agreement in a manner that reduces the amount or changes the form of consideration payable thereunder to Stockholder; provided that any substitution of a cash payment paid on the Closing Date for an identical value of potential payments under the CVR Agreement (as defined in the Merger Agreement), if approved by the Company’s Board of Directors, shall not result in a termination of this Agreement, and (iv) the termination of the Merger Agreement pursuant to Section 8 thereof and, if due in connection therewith, the payment in full of the Termination Fee (the earliest of (i), (ii), (iii) and (iv), the “Termination Date”).  Upon termination of this Agreement, all obligations of the parties under this Agreement will terminate, without any liability or other obligation on the part of any party hereto to any Person in respect hereof or the transactions contemplated hereby, and no party shall have any claim against another (and no person shall have any rights against such party), whether under contract, tort or otherwise, with respect to the subject matter hereof; provided, however, that the termination of this Agreement shall not relieve any party from liability arising from any willful breach prior to such termination.

6.2                               Fiduciary Duties.   Notwithstanding anything in this Agreement to the contrary: (a) Stockholder makes no agreement or understanding herein in any capacity other than in Stockholder’s capacity as a record holder and beneficial owner of Securities, and (b) nothing herein will be construed to limit or affect any action or inaction by Stockholder or any Representative of Stockholder, as applicable, serving on the Company Board of Directors or as an officer or fiduciary of the Company, acting in such person’s capacity as a director, officer or fiduciary of the Company.

6.3                               Expenses.  Each of the parties hereto shall pay its own expenses incurred in connection with this Agreement.  Each of the parties hereto warrants and covenants to the others that it will bear all claims for brokerage fees attributable to action taken by it.

6.4                               Binding Effect.  This Agreement shall be binding upon and inure to the benefit of and be enforceable by the parties hereto and their respective representatives and permitted successors and assigns.

6.5                               Entire Agreement.  This Agreement contains the entire understanding of the parties and supersedes all prior agreements and understandings between the parties with respect to its subject matter.  This Agreement may be amended only by a written instrument duly executed by the parties hereto.

6.6                               Headings.  The headings contained in this Agreement are for reference purposes only and shall not affect in any way the meaning or interpretation of this Agreement.

6.7                               Assignment.  Without limitation of Section 1.1, this Agreement shall be binding upon and inure to the benefit of the parties named herein and their respective successors and permitted assigns.  Except as provided in Section 1.1, no party may assign either this Agreement or any of its rights, interests, or obligations hereunder without the prior written approval of the other parties; provided, however, that each of Parent and Purchaser may freely assign its rights to another direct or indirect wholly owned subsidiary of Parent or Purchaser without such prior written approval but no such assignment shall relieve Parent or Purchaser of any of its obligations hereunder.  Any purported assignment requiring consent without such consent shall be void.

6.8                               Counterparts.  This Agreement may be executed in one or more counterparts, each of which shall be an original, but each of which together shall constitute one and the same Agreement.

6.9                               Notices.  Any notice or other communication required or permitted hereunder shall be in writing and shall be deemed given when delivered in person, by overnight courier, by facsimile transmission (with receipt confirmed by telephone or by automatic transmission report) or by electronic mail (with receipt confirmed by telephone), or two business days after being sent by registered or certified mail (postage prepaid, return receipt requested), as follows:

Any party may by notice given in accordance with this Section 6.9 to the other parties to designate updated information for notices hereunder.

6.10                        Governing Law.  This Agreement shall be governed by and construed and enforced in accordance with the Laws of the State of Delaware, without regard to its principles of conflicts of Laws.

6.11                        Enforceability.  The invalidity or unenforceability of any provision or provisions of this Agreement shall not affect the validity or enforceability of any other provision of this Agreement, which shall remain in full force and effect.  Upon a determination that any term or other provision is invalid, illegal or incapable of being enforced, the parties hereto will negotiate in good faith to modify this Agreement so as to effect the original intent of the parties as closely as possible in an acceptable manner to the end that the transactions contemplated hereby are fulfilled to the fullest extent possible and, absent agreement among the parties, a court is authorized to so modify this Agreement.

6.12                        Further Assurances.  From time to time, at Parent’s request and without further consideration, Stockholder (in its capacity as such) shall execute and deliver to Parent such documents and take such action as Parent may reasonably request in order to consummate more effectively the transactions contemplated hereby.

6.13                        Remedies Not Exclusive.  All rights, powers and remedies provided under this Agreement or otherwise available in respect hereof at law or in equity will be cumulative and not alternative, and the exercise of any thereof by either party will not preclude the simultaneous or later exercise of any other such right, power or remedy by such party.

6.14                        Waiver of Jury Trial.  EACH PARTY HERETO IRREVOCABLY WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING ARISING OUT OF OR RELATED TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY.

6.15                        No Agreement Until Executed. This Agreement shall not constitute or be deemed to evidence a contract, agreement, arrangement or understanding between the parties hereto unless and until (a) the Company Board of Directors has adopted and approved the possible acquisition of the Shares by Parent and Purchaser pursuant to the Merger Agreement, (b) the Merger Agreement is executed by all parties thereto and (c) this Agreement is executed by all parties hereto.

[The rest of this page has intentionally been left blank]

IN WITNESS WHEREOF, Parent, Purchaser and Stockholder have caused this Agreement to be duly executed as of the day and year first above written.

SCHEDULE I TO
THE TENDER AND VOTING AGREEMENT

1.                                      Securities held by Stockholder:

2.                                      Address to which notices or other communications are to be sent in accordance with Section 6.9 of this Agreement:

ANNEX III

CONTINGENT VALUE RIGHTS AGREEMENT

CONTINGENT VALUE RIGHTS AGREEMENT

THIS CONTINGENT VALUE RIGHTS AGREEMENT, dated as of [·], 2013 (this “Agreement”), is entered into by and between Cubist Pharmaceuticals, Inc., a Delaware corporation (“Parent”), and Broadridge Corporate Issuer Solutions, Inc., a Pennsylvania corporation, as Rights Agent.

RECITALS

WHEREAS, Parent, BRGO Corporation, a Delaware corporation (“Sub”), and Trius Therapeutics, Inc. a Delaware corporation (the “Company”), have entered into an Agreement and Plan of Merger dated as of July 30, 2013 (as it may be amended or supplemented from time to time pursuant to the terms thereof, the “Merger Agreement”), pursuant to which Sub (a) has made a tender offer (the “Offer”) to acquire all of the outstanding shares of common stock, par value $0.0001 per share, of the Company (“Company Common Stock”) and (b) following acceptance of the shares of Company Common Stock pursuant to the Offer, will merge with and into the Company, with the Company surviving the Merger as a subsidiary of Parent;

WHEREAS, pursuant to the Merger Agreement, in each of the Offer and the Merger, Parent has agreed to provide to Company’s stockholders the right to receive contingent cash payments as hereinafter described; and

WHEREAS, pursuant to this Agreement, the maximum potential amount payable per CVR is $2.00.

NOW, THEREFORE, in consideration of the foregoing and the consummation of the transactions referred to above, Parent and Rights Agent agree, for the equal and proportionate benefit of all Holders (as hereinafter defined), as follows:

1.                                      DEFINITIONS; certain rules of construction

1.1.                            Definitions.  Capitalized terms used but not otherwise defined herein will have the meanings ascribed to them in the Merger Agreement.  As used in this Agreement, the following terms will have the following meanings:

“Acting Holders” means, at the time of determination, Holders of at least thirty-five percent (35%) of the outstanding CVRs.

“Assignee” has the meaning set forth in Section 6.3.

“Bayer Territories” means the countries listed on Exhibit B to the Collaboration and License Agreement between the Company and Bayer Pharma AG, dated July 26, 2011, as amended, as of the date of the Merger Agreement.

“Board of Directors” means the board of directors of Parent.

“Board Resolution” means a copy of a resolution certified by the secretary or an assistant secretary of Parent to have been duly adopted by the Board of Directors and to be in full force and effect on the date of such certification, and delivered to the Rights Agent.

“Business Day” means any day other than a Saturday, Sunday or a day on which banking institutions in New York, New York are authorized or obligated by law or executive order to remain closed.

“Compound” shall mean: (a) tedizolid, (b) the Company’s proprietary second-generation oxazolidinone, tedizolid phosphate; or (c) any other oxazolidinone derivative, the composition of matter, manufacture, use, importation, sale or offer for sale of which is within the scope of the

2

patent(s) and/or patent application(s) listed in Part 3.8(a) of the Company Disclosure Schedule to the Merger Agreement that relates to tedizolid or tedizolid phosphate.

“CVRs” means the rights of Holders to receive contingent cash payments pursuant to the Merger Agreement and this Agreement.

“CVR Register” has the meaning set forth in Section 2.3(b).

“CVR Shortfall” has the meaning set forth in Section 4.8.

“Diligent Efforts” means, with respect to the Product, efforts of a Person to carry out its obligations, and to cause its controlled Affiliates and Product licensees, if any, to carry out their respective obligations, using such efforts and employing such resources normally used by Persons in the pharmaceutical business similar in size and resources to Parent relating to seeking regulatory approval for a product candidate or commercialization of an approved product that is of similar market potential at a similar stage in its development or product life, taking into account issues of market exclusivity, product profile, including efficacy, safety, tolerability and convenience, the competitiveness of alternate products in the marketplace or under development, the availability of existing forms or dosages of the Product for other indications, the launch or sales of a generic or biosimilar product, the regulatory environment and the profitability of the Product (including pricing and reimbursement status) and other relevant considerations, including technical, commercial, legal, scientific and/or medical factors.

“DTC” means The Depository Trust Company or any successor thereto.

“Governmental Entity” means any foreign or domestic arbitrator, court, nation, government, any state or other political subdivision thereof and any entity exercising executive, legislative, judicial regulatory or administrative functions of, or pertaining to, government.

“Holder” means a Person in whose name a CVR is registered in the CVR Register at the applicable time.

“Independent Accountant” means an independent certified public accounting firm of nationally recognized standing designated either (i) jointly by the Acting Holders and Parent, or (ii) if such parties fail to make a designation, jointly by an independent public accounting firm selected by Parent and an independent public accounting firm selected by the Acting Holders.

“Milestone Notice” has the meaning set forth in Section 2.4.

“Net Sales” means the gross amount invoiced by or on behalf of the relevant Selling Entity for the Product sold to third parties other than any other Selling Entity, less the Permitted Deductions, all as determined in accordance with the Selling Entity’s usual and customary accounting methods consistent with the treatment of other branded prescription products commercialized by the applicable Selling Entity, which shall be in accordance with generally accepted accounting principles, including the accounting methods for translating activity denominated in foreign currencies into United States dollar amounts.  In the case of any sale of the Product between or among the Company, its Affiliates, licensees and sublicensees, for resale, Net Sales will be calculated as above only on the value charged or invoiced on the first arm’s-length sale thereafter to a third party.  For the avoidance of doubt, in the case of any sale of the Product between or among the Company, its Affiliates, licensees and sublicensees where such Affiliate or licensee is an end-user of, and does not further sell, the Product, Net Sales will be calculated on the value charged or invoiced to such Affiliate, licensee or sublicensee. In the case of any sale for value other than exclusively for money (but excluding any patient assistance programs), Net Sales will be calculated on the market price of the Product in the jurisdiction of sale during the relevant period.

3

“Net Sales Statement” means a written statement of Parent, certified by the Chief Financial Officer of Parent, setting forth with reasonable detail (i) an itemized calculation of the gross amounts invoiced by the Selling Entities for the Product sold to third parties other than any other Selling Entity, (ii) an itemized calculation of the Permitted Deductions, and (iii) to the extent that sales for the Products is recorded in currencies other than United States dollars, the exchange rates used for conversion of such foreign currency into United States dollars.

“Officer’s Certificate” means a certificate signed by the chief executive officer, president, chief financial officer, any vice president, the controller, the treasurer or the secretary, in each case of Parent, in his or her capacity as such an officer, and delivered to the Rights Agent.

“Payment Amount” means $1.00 per CVR upon achievement of the Sales Milestone plus $0.10 per CVR for each $1 million by which Net Sales exceed $125 million during the Sales Milestone Period; provided that the aggregate Payment Amount will not exceed $2.00 per CVR.

“Permitted Deductions” means the following deductions to the extent actually deducted by a Selling Entity from the gross invoiced sales price of the Product, or otherwise directly paid or incurred by the Selling Entity with respect to the applicable sale of the Product:

(1)         trade and quantity discounts actually allowed;

(2)         amounts repaid or credited by reasons of defects, recalls, returns, rebates or allowances of goods or because of retroactive price reductions specifically identifiable to the Product;

(3)         chargebacks, rebates (or the equivalent thereof) and other amounts paid on sale of the Product, including such payments mandated by programs of Governmental Entities;

(4)         rebates (or the equivalent thereof) and administrative fees paid to medical healthcare organizations, to group purchasing organizations or to trade customers in line with approved contract terms or other normal and customary understandings and arrangements;

(5)         tariffs, duties, excise, sales, value-added and other taxes (other than taxes based on net income) and charges of Governmental Entities;

(6)         deductions for uncollectible amounts on previously sold products (which adjustment shall be based on actual bad debts incurred and written off as uncollectible by the Selling Entity in a quarter, net of any recoveries of amounts previously written off as uncollectible from current or prior quarters);

(7)         discounts pursuant to indigent patient programs and patient discount programs and coupon discounts;

(8)         transportation, freight, postage, importation, shipping insurance and other handling expenses; and

(9)         required distribution commissions and fees (including fees related to services provided pursuant to distribution service agreements with wholesalers, fee-for-service wholesaler fees and inventory management fees) payable to any third party providing distribution services to the Selling Entities.

For the avoidance of doubt, if a single item falls into more than one of the categories set forth in clauses (1) through (9) above, such item may not be deducted more than once.

“Permitted Transfer” means: a transfer of CVRs (a) upon death of a Holder by will or intestacy; (b) pursuant to a court order; (c) by operation of law (including by consolidation or merger) or without consideration in connection with the dissolution, liquidation or termination of any corporation, limited liability company, partnership or other entity; or (d) in the case of CVRs held in book-entry or other similar nominee form, from a nominee to a beneficial owner and, if applicable, through an intermediary, to the extent allowable by DTC.

4

“Product” means any pharmaceutical product that contains Compound and is intended for intravenous, intramuscular, subcutaneous, oral or sublingual administration, including, in each case, all formulations and line extensions thereof.

“Review Request Period” has the meaning set forth in Section 4.4.

“Rights Agent” means the Rights Agent named in the first paragraph of this Agreement, until a successor Rights Agent will have become such pursuant to the applicable provisions of this Agreement, and thereafter “Rights Agent” will mean such successor Rights Agent.

“Sales Milestone” means cumulative Net Sales of the Product worldwide, other than in the Bayer Territories, during the Sales Milestone Period exceeding $125 million.

“Sales Milestone Period” means the period from and including January 1, 2016 through and including December 31, 2016.

“Selling Entity” means Parent, any Assignee, and each of their controlled Affiliates (including, from and after the Effective Time, the Company), licensees and sublicensees.

1.2.                            Rules of Construction.  Except as otherwise explicitly specified to the contrary, (a) references to a Section means a Section of this Agreement unless another agreement is specified, (b) the word “including” (in its various forms) means “including without limitation,” (c) references to a particular statute or regulation include all rules and regulations thereunder and any successor statute, rules or regulation, in each case as amended or otherwise modified from time to time, (d) words in the singular or plural form include the plural and singular form, respectively, (e) references to a particular Person include such Person’s successors and assigns to the extent not prohibited by this Agreement and (f) all references to dollars or “$” refer to United States dollars.

2.                                      CONTINGENT Value RIGHTS

2.1.                            CVRs.  The CVRs represent the rights of Holders to receive contingent cash payments pursuant to this Agreement.  The initial Holders will be determined pursuant to the terms of the Merger Agreement.

2.2.                            Nontransferable.  The CVRs may not be sold, assigned, transferred, pledged, encumbered or in any other manner transferred or disposed of, in whole or in part, other than through a Permitted Transfer.

2.3.                            No Certificate; Registration; Registration of Transfer; Change of Address.

(a)                                 The CVRs will not be evidenced by a certificate or other instrument.

(b)                                 The Rights Agent will keep a register (the “CVR Register”) for the purpose of registering CVRs and transfers of CVRs as herein provided.  The CVR Register will initially show one position for Cede & Co representing all the shares of Company Common Stock held by DTC on behalf of the street holders of the shares of Company Common Stock tendered by such holders in the Offer or held by such holders as of immediately prior to the Effective Time.  The Rights Agent will have no responsibility whatsoever directly to the street name holders with respect to transfers of CVRs.  With respect to any payments to be made under Section 2.4 below, the Rights Agent will accomplish the payment to any former street name holders of shares of Company Common Stock by sending one lump payment to DTC.  The Rights Agent will have no

5

responsibilities whatsoever with regard to the distribution of payments by DTC to such street name holders.

(c)                                  Subject to the restrictions on transferability set forth in Section 2.2, every request made to transfer a CVR must be in writing and accompanied by a written instrument of transfer in form reasonably satisfactory to the Rights Agent pursuant to its guidelines, duly executed by the Holder thereof, the Holder’s attorney duly authorized in writing, the Holder’s personal representative or the Holder’s survivor, and setting forth in reasonable detail the circumstances relating to the transfer.  Upon receipt of such written notice, the Rights Agent will, subject to its reasonable determination that the transfer instrument is in proper form and the transfer otherwise complies with the other terms and conditions of this Agreement (including the provisions of Section 2.2), register the transfer of the CVRs in the CVR Register.  Parent and Rights Agent may require payment of a sum sufficient to cover any stamp or other tax or governmental charge that is imposed in connection with any such registration of transfer.  The Rights Agent shall have no duty or obligation to take any action under any section of this Agreement that requires the payment by a Holder of a CVR of applicable taxes or charges unless and until the Rights Agent is satisfied that all such taxes or charges have been paid.  All duly transferred CVRs registered in the CVR Register will be the valid obligations of Parent and will entitle the transferee to the same benefits and rights under this Agreement as those held immediately prior to the transfer by the transferor.  No transfer of a CVR will be valid until registered in the CVR Register.

(d)                                 A Holder may make a written request to the Rights Agent to change such Holder’s address of record in the CVR Register.  The written request must be duly executed by the Holder.  Upon receipt of such written notice, the Rights Agent will, subject to its reasonable determination that the transfer instrument is in proper form, promptly record the change of address in the CVR Register.

2.4.                            Payment Procedures.

(a)                                 On or before February 15, 2017, Parent will deliver to the Rights Agent (i) a notice (the “Milestone Notice”) indicating whether the Sales Milestone was achieved and (ii) the Net Sales Statement for the fiscal year ended December 31, 2016 along with any letter of instruction required by the Rights Agent.  In addition, in the event that Parent does not timely file, in accordance with applicable SEC rules and regulations, with the SEC a quarterly report on Form 10-Q with respect to any of the first, second or third fiscal quarters of 2016, Parent will deliver to the Rights Agent on or before the 45th day following the completion of any such fiscal quarter of 2016 a Net Sales Statement with respect to all then completed fiscal quarters during the fiscal year ending December 31, 2016.

(b)                                 The Rights Agent will promptly, and in any event within ten Business Days of receipt of a Milestone Notice and/or Net Sales Statement as well as any letter of instruction required by the Rights Agent, send each Holder at its registered address a copy of such Milestone Notice and/or Net Sales Statement.  If a Payment Amount is payable to the Holders, then at the time the Rights Agent sends a copy of the Milestone

6

Notice to the Holders, the Rights Agent will also pay the Payment Amount to each of the Holders (the amount to which each Holder is entitled to receive will be the Payment Amount multiplied by the number of CVRs held by such Holder as reflected on the CVR Register) by check mailed to the address of each Holder as reflected in the CVR Register as of the close of business on the date of the Milestone Notice.

(c)                                  Parent shall be entitled to deduct or withhold, or cause the Rights Agent to deduct or withhold, from any Payment Amount otherwise payable pursuant to this Agreement such amounts as may be required to be deducted or withheld therefrom under the Code, the Treasury Regulations thereunder, or any other applicable Tax Law, as may be determined by Parent or the Rights Agent.  Prior to making any such Tax withholdings or causing any such Tax withholdings to be made with respect to any Holder, Parent shall instruct the Rights Agent to solicit IRS Form W-9s from Holders eligible for Tax withholding within a reasonable amount of time in order to provide the opportunity for the Holder to provide any necessary Tax forms (including an IRS Form W-9 or an applicable IRS Form W-8) in order to avoid or reduce such withholding amounts. To the extent such amounts are so deducted or withheld, such amounts shall be treated for all purposes under this Agreement as having been paid to the person to whom such amounts would otherwise have been paid, and prior to the 15th day of February in the year following any payment of such taxes by Parent or the Rights Agent, Parent shall deliver (or shall cause the Rights Agent to deliver) to the person to whom such amounts would otherwise have been paid the original Form 1099 or other reasonably acceptable evidence of such withholding.

(d)                                 Any portion of any Payment Amount that remains undistributed to the Holders six (6) months after the date of the Milestone Notice will be delivered by the Rights Agent to Parent, upon demand, and any Holder will thereafter look only to Parent for payment of such Payment Amount, without interest, but such Holder will have no greater rights against Parent than those accorded to general unsecured creditors of Parent under applicable law.

(e)                                  Neither Parent nor the Rights Agent will be liable to any person in respect of any Payment Amount delivered to a public official pursuant to any applicable abandoned property, escheat or similar law.  If, despite Parent’s and/or the Rights Agent’s commercially reasonable efforts to deliver a Payment Amount to the applicable Holder, such Payment Amount has not been paid immediately prior to the date on which such Payment Amount would otherwise escheat to or become the property of any Governmental Entity, any such Payment Amount will, to the extent permitted by applicable law, become the property of Parent, free and clear of all claims or interest of any person previously entitled thereto.  In addition to and not in limitation of any other indemnity obligation herein, Parent agrees to indemnify and hold harmless Rights Agent with respect to any liability, penalty, cost or expense Rights Agent may incur or be subject to in connection with transferring such property to Parent.

7

2.5.                            No Voting, Dividends or Interest; No Equity or Ownership Interest in Parent.

(a)                                 The CVRs will not have any voting or dividend rights, and interest will not accrue on any amounts payable on the CVRs to any Holder.

(b)                                 The CVRs will not represent any equity or ownership interest in Parent or in any constituent company to the Merger.

3.                                      THE RIGHTS AGENT

3.1.                            Certain Duties and Responsibilities.  The Rights Agent will not have any liability for any actions taken or not taken in connection with this Agreement, except to the extent of its willful misconduct, bad faith or gross negligence.

3.2.                            Certain Rights of Rights Agent.  The Rights Agent undertakes to perform such duties and only such duties as are specifically set forth in this Agreement, and no implied covenants or obligations will be read into this Agreement against the Rights Agent.  In addition:

(a)                                 the Rights Agent may rely and will be protected and held harmless by Parent in acting or refraining from acting upon any resolution, certificate, statement, instrument, opinion, report, notice, request, direction, consent, order or other paper or document believed by it to be genuine and to have been signed or presented by the proper party or parties;

(b)                                 whenever the Rights Agent will deem it desirable that a matter be proved or established prior to taking, suffering or omitting any action hereunder, the Rights Agent may rely upon an Officer’s Certificate, which certificate shall be full authorization and protection to the Rights Agent, and the Rights Agent shall, in the absence of bad faith, gross negligence or willful misconduct on its part, incur no liability and be held harmless by Parent for or in respect of any action taken, suffered or omitted to be taken by it under the provisions of this Agreement in reliance upon such certificate;

(c)                                  the Rights Agent may engage and consult with counsel of its selection and the written advice of such counsel or any opinion of counsel will be full and complete authorization and protection and shall be held harmless by Parent in respect of any action taken, suffered or omitted by it hereunder in good faith and in reliance thereon;

(d)                                 the permissive rights of the Rights Agent to do things enumerated in this Agreement will not be construed as a duty;

(e)                                  the Rights Agent will not be required to give any note or surety in respect of the execution of such powers or otherwise in respect of the premises;

(f)                                   the Rights Agent shall not be liable for or by reason of, and shall be held harmless by Parent with respect to any of the statements of fact or recitals contained in this Agreement or be required to verify the same, but all such statements and recitals are and shall be deemed to have been made by the Parent only;

8

(g)                                  the Rights Agent will have no liability and shall be held harmless by Parent in respect of the validity of this Agreement or the execution and delivery hereof (except the due execution and delivery hereof by the Rights Agent and the enforceability of this Agreement against the Rights Agent assuming the due execution and delivery hereof by Parent); nor shall it be responsible for any breach by the Parent of any covenant or condition contained in this Agreement;

(h)                                 Parent agrees to indemnify Rights Agent for, and hold Rights Agent harmless against, any loss, liability, claim, demands, suits or expense arising out of or in connection with Rights Agent’s duties under this Agreement, including the costs and expenses of defending Rights Agent against any claims, charges, demands, suits or loss, unless such loss has been determined by a court of competent jurisdiction to be a result of Rights Agent’s gross negligence, bad faith or willful or intentional misconduct;

(i)                                     Rights Agent shall not be liable for consequential damages under any provision of this Agreement or for any consequential damages arising out of any act or failure to act hereunder in the absence of bad faith, gross negligence or willful misconduct on its part;

(j)                                    Parent agrees (i) to pay the fees and expenses of the Rights Agent in connection with this Agreement as agreed upon in writing by the Rights Agent and Parent on or prior to the date hereof, and (ii) to reimburse the Rights Agent for all taxes and governmental charges, reasonable expenses and other charges of any kind and nature incurred by the Rights Agent in the execution of this Agreement (other than taxes imposed on or measured by the Rights Agent’s net income and franchise or similar taxes imposed on it (in lieu of net income taxes)).  The Rights Agent will also be entitled to reimbursement from Parent for all reasonable and necessary out-of-pocket expenses paid or incurred by it in connection with the administration by the Rights Agent of its duties hereunder; and

(k)                                 No provision of this Agreement shall require the Rights Agent to expend or risk its own funds or otherwise incur any financial liability in the performance of any of its duties hereunder or in the exercise of its rights if there shall be reasonable grounds for believing that repayment of such funds or adequate indemnification against such risk or liability is not reasonably assured to it.

3.3.                            Resignation and Removal; Appointment of Successor.

(a)                                 The Rights Agent may resign at any time by giving written notice thereof to Parent specifying a date when such resignation will take effect, which notice will be sent at least 60 days prior to the date so specified but in no event will such resignation become effective until a successor Rights Agent has been appointed.  Parent has the right to remove Rights Agent at any time by a Board Resolution specifying a date when such removal will take effect but no such removal will become effective until a successor Rights Agent has been appointed.  Notice of such removal will be given by Parent to Rights Agent, which notice will be sent at least 60 days prior to the date so specified.

(b)                                 If the Rights Agent provides notice of its intent to resign, is removed or becomes incapable of acting, Parent, by a Board Resolution, will as soon as is reasonably possible

9

appoint a qualified successor Rights Agent who, unless otherwise consented to in writing by the Holders of not less than a majority of the outstanding CVRs, shall be a stock transfer agent of national reputation or the corporate trust department of a commercial bank.  The successor Rights Agent so appointed will, forthwith upon its acceptance of such appointment in accordance with Section 3.4, become the successor Rights Agent.

(c)                                  Parent will give notice of each resignation and each removal of a Rights Agent and each appointment of a successor Rights Agent by mailing written notice of such event by first-class mail to the Holders as their names and addresses appear in the CVR Register.  Each notice will include the name and address of the successor Rights Agent.  If Parent fails to send such notice within ten days after acceptance of appointment by a successor Rights Agent, the successor Rights Agent will cause the notice to be mailed at the expense of Parent.

3.4.                            Acceptance of Appointment by Successor.  Every successor Rights Agent appointed hereunder will execute, acknowledge and deliver to Parent and to the retiring Rights Agent an instrument accepting such appointment and a counterpart of this Agreement, and thereupon such successor Rights Agent, without any further act, deed or conveyance, will become vested with all the rights, powers, trusts and duties of the retiring Rights Agent.  On request of Parent or the successor Rights Agent, the retiring Rights Agent will execute and deliver an instrument transferring to the successor Rights Agent all the rights, powers and trusts of the retiring Rights Agent.

4.                                      COVENANTS

4.1.                            List of Holders.  Parent will furnish or cause to be furnished to the Rights Agent in such form as Parent receives from the Company’s transfer agent (or other agent performing similar services for the Company), the names and addresses of the Holders within ten Business Days of the Effective Time.

4.2.                            Payment of Payment Amount.  If the Sales Milestone has been achieved in accordance with this Agreement, Parent will, promptly following the delivery of the Milestone Notice, deposit with the Rights Agent, for payment to the Holders in accordance with Section 2.4, the aggregate amount necessary to pay the Payment Amount to all Holders.  For the avoidance of doubt, the Payment Amount shall only be paid, if at all, one time under this Agreement.

4.3.                            Books and Records.  Parent shall, and shall cause its Subsidiaries to, keep true, complete and accurate records in sufficient detail to enable the Holders and their consultants or professional advisors to determine the amounts payable hereunder.

4.4.                            Audits.

(a)                                 Upon the written request of the Acting Holders provided to Parent within 120 days of the date on which the Holders are delivered the final Net Sales Statement pursuant to Section 2.4(b) of this Agreement (the “Review Request Period”), Parent shall permit, and shall cause its controlled Affiliates to permit, the Independent Accountant to have access during normal business hours to such of the records of the Company or other

10

applicable Selling Entity as may be reasonably necessary to verify the accuracy of the Net Sales Statement and the figures underlying the calculations set forth therein, including, without limitation, all written materials related to any sale transaction reasonably requested by such Independent Accountant.  The Independent Accountant shall be charged to come to a final determination with respect to those specific items in the Net Sales Statement that the parties disagree on and submit to it for resolution.  All other items in the Net Sales Statement that the parties do not submit, prior to the end of the Review Request Period, to the Independent Accountant for resolution shall be deemed to be agreed by the parties and the Independent Accountant shall not be charged with calculating or validating those agreed upon items.  If issues are submitted to the Independent Accountant for resolution, Parent shall, and shall cause to its controlled Affiliates to, furnish to the Independent Accountant such access, work papers and other documents and information related to those disputed issues as the Independent Accountant may request and as are available to Parent.  The Independent Accountant shall disclose to Parent and the Acting Holders any matters directly related to their findings to the extent necessary to verify the accuracy or completeness of the Net Sales Statements.  The fees charged by such accounting firm shall be paid by Parent.

(b)                                 If the Independent Accountant concludes that a Payment Amount that was properly due was not paid to the Holders, Parent shall pay to the Rights Agent (for further distribution to the Holders) or to each Holder the applicable Payment Amount, plus interest on such Payment Amount at the “prime rate” as published in the Wall Street Journal or similar reputable data source from time to time calculated from when the Payment Amount should have been paid (if Parent had given notice of achievement of the Sales Milestone following its actual achievement, as determined by the Independent Accountant, at the time required pursuant to the terms of this Agreement), as applicable, to the date of actual payment (such amount including interest being the “CVR Shortfall”).  The CVR Shortfall shall be paid within ten (10) days of the date the Independent Accountant delivers to Parent and the Acting Holders the Independent Accountant’s written report.  The decision of the Independent Accountant shall be final, conclusive and binding on Parent and the Holders, shall be non-appealable and shall not be subject to further review.

(c)                                  If, upon the expiration of the Review Request Period, the Acting Holders have not requested a review of the Net Sales Statement in accordance with this Section 4.8, the calculations set forth in the Net Sales Statement shall be binding and conclusive upon the Holders.

(d)                                 Each person seeking to receive information from Parent in connection with a review pursuant to this Section 4.8 shall enter into, and shall cause its accounting firm to enter into, a reasonable and mutually satisfactory confidentiality agreement with Parent or any controlled Affiliate obligating such party to retain all such information disclosed to such party in confidence pursuant to such confidentiality agreement.

(e)                                  Parent shall not, and shall cause its Affiliates not to, enter into any license or distribution agreement with any third party (other than Parent or its Affiliates) with respect to a Product unless such agreement contains provisions that would allow any

11

Independent Accountant appointed pursuant to this Section 4.4 such access to the records of the other party to such license or distribution agreement as may be reasonably necessary to perform its duties pursuant to this Section 4.4; provided that Parent and its Affiliates shall not be required to amend any of its existing licenses.  The parties hereto agree that, if Parent or its Affiliates have exercised audit rights under any license or distribution agreement prior to the Acting Holders’ request for an audit under this Section 4.4 and under such license or distribution agreement Parent and its Affiliates cannot request another audit, the results of Parent’s prior audit of such licensee or distributor shall be used for purposes of the audit requested by the Acting Holders under this Section 4.4 and that Parent shall not have any further obligation to provide access to an Independent Accountant with respect to such licensee until such time as Parent may again exercise its rights of audit under the license agreement with such licensee.

4.5.                            Milestones.  Parent shall, and shall cause its controlled Affiliates to, use Diligent Efforts to achieve the Sales Milestone.

5.                                      AMENDMENTS

5.1.                            Amendments without Consent of Holders.

(a)                                 Without the consent of any Holders or the Rights Agent, Parent, when authorized by a Board Resolution, at any time and from time to time, may enter into one or more amendments hereto, to evidence the succession of another Person to Parent and the assumption by any such successor of the covenants of Parent herein as provided in Section 6.3.

(b)                                 Without the consent of any Holders, Parent, when authorized by a Board Resolution, and the Rights Agent, in the Rights Agent’s sole and absolute discretion, at any time and from time to time, may enter into one or more amendments hereto, for any of the following purposes:

(i)                                     to evidence the succession of another Person as a successor Rights Agent and the assumption by any such successor of the covenants and obligations of the Rights Agent herein;

(ii)                                  to add to the covenants of Parent such further covenants, restrictions, conditions or provisions as Parent and the Rights Agent will consider to be for the protection of the Holders; provided that, in each case, such provisions do not adversely affect the interests of the Holders;

(iii)                               to cure any ambiguity, to correct or supplement any provision herein that may be defective or inconsistent with any other provision herein, or to make any other provisions with respect to matters or questions arising under this Agreement; provided that, in each case, such provisions do not adversely affect the interests of the Holders;

12

(iv)                              as may be necessary or appropriate to ensure that the CVRs are not subject to registration under the Securities Act or the Exchange Act;

(v)                                 to reduce the number of CVRs, in the event any Holder agrees to renounce such Holder’s rights under this Agreement in accordance with Section 6.4; or

(vi)                              any other amendments hereto for the purpose of adding, eliminating or changing any provisions of this Agreement, unless such addition, elimination or change is adverse to the interests of the Holders.

(c)                                  Promptly after the execution by Parent and the Rights Agent of any amendment pursuant to the provisions of this Section 5.1, Parent will mail (or cause the Rights Agent to mail) a notice thereof by first class mail to the Holders at their addresses as they appear on the CVR Register, setting forth such amendment.

5.2.                            Amendments with Consent of Holders.

(a)                                 Subject to Section 5.1 (which amendments pursuant to Section 5.1 may be made without the consent of the Holders), with the consent of the Holders of not less than a majority of the outstanding CVRs, whether evidenced in writing or taken at a meeting of the Holders, Parent, when authorized by a Board Resolution, and the Rights Agent may enter into one or more amendments hereto for the purpose of adding, eliminating or changing any provisions of this Agreement, even if such addition, elimination or change is materially adverse to the interest of the Holders; provided, however, that no such amendment shall, without the consent of the Holders of sixty six (66%) percent of the outstanding CVRs:

(i)                                     modify in a manner adverse to the Holders (A) any provision contained herein with respect to the termination of this Agreement or the CVRs, (B) the time for, and amount of, any payment to be made to the Holders pursuant to this Agreement, or (C) the definition of the Sales Milestone,

(ii)                                  reduce the number of CVRs, or

(iii)                               modify any provisions of this Section 5.2, except to increase the percentage of Holders from whom consent is required or to provide that certain provisions of this Agreement cannot be modified or waived without the consent of the Holder of each outstanding CVR affected thereby.

(b)                                 Promptly after the execution by Parent and the Rights Agent of any amendment pursuant to the provisions of this Section 5.2, Parent will mail (or cause the Rights Agent to mail) a notice thereof by first class mail to the Holders at their addresses as they appear on the CVR Register, setting forth such amendment.

5.3.                            Execution of Amendments.  In executing any amendment permitted by this Section 5, the Rights Agent will be entitled to receive, and will be fully protected in relying upon, an opinion of counsel selected by Parent stating that the execution of such amendment is authorized or

13

permitted by this Agreement.  The Rights Agent may, but is not obligated to, enter into any such amendment that affects the Rights Agent’s own rights, privileges, covenants or duties under this Agreement or otherwise.

5.4.                            Effect of Amendments.  Upon the execution of any amendment under this Section 5, this Agreement will be modified in accordance therewith, such amendment will form a part of this Agreement for all purposes and every Holder will be bound thereby.

6.                                      OTHER PROVISIONS OF GENERAL APPLICATION

6.1.                            Notices to Rights Agent and Parent.  Any notice or other communication required or permitted hereunder shall be in writing and shall be deemed given when delivered in person, by overnight courier, by facsimile transmission (with receipt confirmed by telephone or by automatic transmission report) or by electronic mail, or two (2) business days after being sent by registered or certified mail (postage prepaid, return receipt requested), as follows:

If to the Rights Agent, to it at:

Broadridge Corporate Issuer Solutions, Inc.

1717 Arch St

Suite 1300

Philadelphia, Pennsylvania 19103

Attn: Corporate Actions Manager

With a copy to:

Broadridge Financial Solutions, Inc.
2 Journal Square Plaza

Jersey City, New Jersey 07306
Attention:  General Counsel

If to Parent, to it at:

Cubist Pharmaceuticals, Inc.

65 Hayden Avenue

Lexington, MA 02421

Attention:  Thomas DesRosier, Senior Vice President, Chief Legal Officer,
General Counsel and Secretary

Telephone: 781 ###-###-####

with a copy to:

Ropes & Gray LLP

Prudential Tower

800 Boylston Street

Boston, Massachusetts 02199

Telephone:                                   617 ###-###-####

14

Facsimile:                                         617 ###-###-####

Email:                                                            ***@***

***@***

Attention:                                         Christopher Comeau

Paul Kinsella

The Rights Agent or Parent may specify a different address or facsimile number by giving notice in accordance with this Section 6.1.

6.2.                            Notice to Holders.  Where this Agreement provides for notice to Holders, such notice will be sufficiently given (unless otherwise herein expressly provided) if in writing and mailed, first-class postage prepaid, to each Holder affected by such event, at the Holder’s address as it appears in the CVR Register, not later than the latest date, and not earlier than the earliest date, if any, prescribed for the giving of such notice.  In any case where notice to Holders is given by mail, neither the failure to mail such notice, nor any defect in any notice so mailed, to any particular Holder will affect the sufficiency of such notice with respect to other Holders.

6.3.                            Parent Successors and Assigns.  Parent may assign, in its sole discretion and without the consent of any other party, any or all of its rights, interests and obligations hereunder to one or more direct or indirect wholly-owned subsidiaries of Parent or to any purchaser or licensee of substantial rights to the Product (each, an “Assignee”) provided that the Assignee agrees to assume and be bound by all of the terms of this Agreement.  Any such Assignee may thereafter assign, in its sole discretion and without the consent of any other party, any or all of its rights, interests and obligations hereunder to one or more additional Assignees who agree to assume and be bound by all of the terms of this Agreement; provided, however, that in connection with any assignment to an Assignee, Parent and Sub (or the other assignor) shall agree to remain liable for the performance by each Assignee(and such other assignor, if applicable) of all obligations of Parent and Sub hereunder, with such Assignee substituted for Parent and Sub under this Agreement.  This Agreement will be binding upon, inure to the benefit of and be enforceable by Parent’s successors and each Assignee, and this Agreement shall not restrict Parent’s, any Assignee’s or any of their respective successor’s ability to merge or consolidate.  Each of Parent’s successors and assigns shall expressly assume by an instrument supplemental hereto, executed and delivered to the Rights Agent, the due and punctual payment of the CVRs and the due and punctual performance and observance of all of the covenants and obligations of this Agreement to be performed or observed by Parent.

6.4.                            Benefits of Agreement.  Nothing in this Agreement, express or implied, will give to any Person (other than the Rights Agent, Parent, Parent’s successors and assignees, and the Holders) any benefit or any legal or equitable right, remedy or claim under this Agreement or under any covenant or provision herein contained, all such covenants and provisions being for the sole benefit of the, Rights Agent, Parent, Parent’s successors and assignees, and the Holders.  The rights of Holders are limited to those expressly provided in this Agreement and the Merger Agreement.  Notwithstanding anything to the contrary contained herein, any Holder may agree to renounce, in whole or in part, such Holder’s rights under this Agreement by written notice to the Rights Agent and Parent, which notice, if given, shall be irrevocable.

15

6.5.                            Governing Law.  This Agreement, the CVRs and all actions arising under or in connection therewith shall be governed by and construed in accordance with the laws of the State of Delaware, regardless of the laws that might otherwise govern under applicable principles of conflicts of law thereof.

6.6.                            Severability.  If any provision of this Agreement is held invalid or unenforceable by any court of competent jurisdiction, the other provisions of this Agreement shall remain in full force and effect.  Any provision of this Agreement held invalid or unenforceable only in part or degree shall remain in full force and effect to the extent not held invalid or unenforceable.  The parties further agree to replace such invalid or unenforceable provision of this Agreement with a valid and enforceable provision that will achieve, to the extent possible, the economic, business and other purposes of such invalid or unenforceable provision.

6.7.                            Counterparts and Signature.  This Agreement may be executed in two or more counterparts (including by facsimile or by an electronic scan delivered by electronic mail), each of which shall be deemed an original but all of which together shall be considered one and the same agreement and shall become effective when counterparts have been signed by each of the parties hereto and delivered to the other party, it being understood that the parties need not sign the same counterpart.

6.8.                            Termination.  This Agreement will be terminated and of no force or effect, the parties hereto will have no liability hereunder (other than with respect to monies due and owing by Parent to Rights Agent), and no payments will be required to be made, upon the earlier to occur of (a) the mailing by the Rights Agent to the address of each Holder as reflected in the CVR Register the full amount of all potential Payment Amounts required to be paid under the terms of this Agreement and (b) in the event the Milestone Notice indicates that the Net Sales Milestone has not been achieved, the expiration of the Review Request Period, unless there has been a request for an audit pursuant to Section 4.4 prior to the end of the Review Request Period, in which case until such audit has been completed and any CVR Shortfall determined to be payable as a result of such audit, if applicable, has been paid.  In no event will any Payment Amount become payable on account of sales of the Product consummated prior to January 1, 2016 or after December 31, 2016.

6.9.                            Entire Agreement.  This Agreement and the Merger Agreement (including the schedules, annexes and exhibits thereto and the documents and instruments referred to therein) contain the entire understanding of the parties hereto and thereto with reference to the transactions and matters contemplated hereby and thereby and supersedes all prior agreements, written or oral, among the parties with respect hereto and thereto.  If and to the extent that any provision of this Agreement is inconsistent or conflicts with the Merger Agreement, this Agreement will govern and be controlling.

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

16

IN WITNESS WHEREOF, each of the parties has caused this Agreement to be executed on its behalf by its duly authorized officers as of the day and year first above written.