Connetics Corporation, a Delaware corporation

Exhibit 10.15

CONNETICS CORPORATION

CONSULTANT CHANGE OF CONTROL AGREEMENT

     This Consultant Change of Control Agreement (the “Agreement”) is made and entered into effective as of January 1, 2002 (the “Effective Date”), by and between G. Kirk Raab (the “Consultant”) and Connetics Corporation, a Delaware corporation (“Connetics”). Certain capitalized terms used in this Agreement are defined in Section 1 below.

R E C I T A L S

     A. It is expected that Connetics from time to time will consider the possibility of a Change of Control, as defined in this Agreement. The Board of Directors of Connetics (the “Board”) recognizes that such consideration can be a distraction to the Consultant and can cause the Consultant to consider alternative service opportunities which would be detrimental to Connetics.

     B. Connetics believes that it is in the best interests of Connetics and its stockholders to provide the Consultant with an incentive to continue his service to Connetics in his capacity as a valued consultant and to maximize the value of Connetics upon a Change of Control for the benefit of its stockholders.

     C. In order to encourage the Consultant to remain with Connetics notwithstanding the possibility of a Change of Control, Connetics believes that it is imperative to provide the Consultant with certain severance benefits upon the Consultant’s termination of his status as a consultant under certain circumstances following a Change of Control.

     D. This Agreement supersedes any and all prior agreements that have as their primary purpose the provision of benefits upon certain circumstances following a Change of Control.

AGREEMENT

     In consideration of the mutual covenants contained in this Agreement, the parties agree as follows:

     1. Definition of Terms. The following terms referred to in this Agreement shall have the following meanings:

          (a) Cause. “Cause” shall mean (i) any act of dishonesty taken by the Consultant in connection with his responsibilities as a consultant which is intended to result in personal enrichment to the Consultant, (ii) Consultant’s conviction of a felony that the Board believes has had or will have a material detrimental effect on Connetics’ reputation or business, (iii) a willful act or willful failure to act by the Consultant that constitutes misconduct and is injurious to Connetics, (iv) any material breach of any agreement with Connetics, or (v) continued willful violations by the

Consultant of the Consultant’s obligations to Connetics or responsibilities/duties as a consultant after there has been delivered to the Consultant a written demand for performance from Connetics which describes the basis for Connetics’ belief that the Consultant has not substantially performed his duties as a consultant.

          (b) Change of Control. “Change of Control” shall mean the occurrence of any of the following events:

               (i) the approval by Connetics’ shareholders of a merger or consolidation of Connetics with any other corporation, other than a merger or consolidation which would result in the voting securities of Connetics outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity) more than fifty percent (50%) of the total voting power represented by the voting securities of Connetics or such surviving entity outstanding immediately after such merger or consolidation;

               (ii) the approval by Connetics’ shareholders of a plan of complete liquidation of Connetics or an agreement for the sale or disposition by Connetics of all or substantially all of Connetics’ assets;

               (iii) any “person” (as such term is used in Sections 13(d) and 14(d) of the Securities Exchange Act of 1934, as amended) becoming the “beneficial owner” (as defined in Rule 13d-3 under said Act), directly or indirectly, of securities of Connetics representing 50% or more of the total voting power represented by Connetics’ then outstanding voting securities; or

               (iv) a change in the composition of the Board, as a result of which fewer than a majority of the directors are Incumbent Directors. “Incumbent Directors” shall mean directors who either (A) are directors of Connetics as of the date hereof, or (B) are elected, or nominated for election, to the Board with the affirmative votes of at least a majority of those directors whose election or nomination was not in connection with any transactions described in subsections (i), (ii), or (iii) or in connection with an actual or threatened proxy contest relating to the election of directors of Connetics.

          (c) Involuntary Termination. “Involuntary Termination” shall mean (i) without the Consultant’s express written consent, a significant reduction of the Consultant’s duties, position or responsibilities relative to the Consultant’s duties, position or responsibilities in effect immediately prior to such reduction, or the removal of the Consultant from such position, duties and responsibilities, unless the Consultant is provided with comparable duties, position and responsibilities; provided, however, that a reduction in duties, position or responsibilities solely by virtue of Connetics being acquired and made part of a larger entity (as, for example, when the Chief Financial Officer of Connetics remains as such following a Change of Control but is not made the Chief Financial Officer of the acquiring corporation) shall not constitute an “Involuntary Termination;” (ii) without the Consultant’s express written consent, a significant reduction, without good business reasons, of the facilities and perquisites (including office space and location) available to the Consultant immediately prior to such reduction; (iii) without the Consultant’s express written consent, a reduction by Connetics of the Consultant’s consulting fee as in effect immediately prior to such reduction; (iv) without the Consultant’s express written consent, a material reduction by Connetics in the kind or level of benefits to which the Consultant is entitled immediately prior to such reduction with the result that the Consultant’s overall benefits package is significantly reduced;

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(v) without the Consultant’s express written consent, the relocation of the Consultant to a facility or a location more than fifty (50) miles from his current location; (vi) any termination of the Consultant by Connetics that is not effected for Cause or for which the grounds relied upon are not valid; or (vii) the failure of Connetics to obtain the assumption of this Agreement by any successors contemplated in Section 7 below.

          (d) Termination Date. “Termination Date” shall mean the effective date of any notice of termination delivered by one party to the other under this Agreement.

     2. Term of Agreement. This Agreement shall terminate on the earlier of (a) the date that all obligations of the parties under this Agreement have been satisfied or (b) on the date, prior to a Change of Control, the Consultant is no longer providing services to Connetics in his capacity as a consultant.

     3. Severance Benefits In the Event of an Involuntary Termination.

          (a) Termination of Service Following A Change of Control. If the Consultant’s service with Connetics terminates as a result of an Involuntary Termination at any time within twenty-four (24) months after a Change of Control, Consultant shall be entitled to the following severance benefits:

               (i) 2.99 times the Consultant’s annual consulting fee as in effect as of the Termination Date, less applicable withholding, payable in a lump sum within thirty (30) days of the Termination Date;

               (ii) the same level of health (i.e., medical, vision and dental) coverage and benefits as in effect for the Consultant on the day immediately preceding the day of the Consultant’s termination of employment for a period of thirty-six (36) months; and

               (iii) outplacement/administrative support for a period of six (6) months following the Termination Date.

          (b) Termination Apart from a Change of Control. If the Consultant’s service with Connetics terminates other than as a result of an Involuntary Termination within twenty-four (24) months following a Change of Control, then the Consultant shall not be entitled to receive severance or other benefits as described in this Section 5(b), but may be eligible for those benefits (if any) as may then be established under Connetics’ then existing severance and benefits plans and policies at the time of such termination.

          (c) Accrued Fee and Expenses. Without regard to the reason for, or the timing of, Consultant’s termination of his consulting relationship with Connetics: (i) Connetics shall pay the Consultant any unpaid consulting fee due for periods prior to the Termination Date;; and (ii) following submission of proper expense reports by the Consultant, Connetics shall reimburse the Consultant for all expenses reasonably and necessarily incurred by the Consultant in connection with the business of Connetics prior to the Termination Date. These payments shall be made promptly upon termination of the consulting relationship and within the period of time mandated by law.

     4. Limitation on Payments. In the event that the option acceleration, severance or other benefits provided for in this Agreement or otherwise payable to the Consultant (i) constitute

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“parachute payments” within the meaning of Section 280G of the Code, and (ii) would be subject to the excise tax imposed by Section 4999 of the Code (the “Excise Tax”), then Consultant’s benefits under this Agreement shall be either

          (a) delivered in full, or

          (b) delivered to such lesser extent which would result in no portion of such benefits being subject to the Excise Tax,

whichever of the foregoing amounts, taking into account the applicable federal, state and local income taxes and the Excise Tax, results in the receipt by Consultant on an after-tax basis, of the greatest amount of benefits, notwithstanding that all or some portion of such benefits may be taxable under Section 4999 of the Code.

     Unless Connetics and the Consultant otherwise agree in writing, any determination required under this Section shall be made in writing by Connetics’ independent public accountants (the “Accountants”), whose determination shall be conclusive and binding upon the Consultant and Connetics for all purposes. For purposes of making the calculations required by this Section, the Accountants may make reasonable assumptions and approximations concerning applicable taxes and may rely on reasonable, good faith interpretations concerning the application of Section 280G and 4999 of the Code. Connetics and the Consultant shall furnish to the Accountants such information and documents as the Accountants may reasonably request in order to make a determination under this Section. Connetics shall bear all costs the Accountants may reasonably incur in connection with any calculations contemplated by this Section.

     5. Successors.

          (a) Company’s Successors. Any successor to Connetics (whether direct or indirect and whether by purchase, lease, merger, consolidation, liquidation or otherwise) to all or substantially all of Connetics’ business and/or assets shall assume Connetics’ obligations under this Agreement and agree expressly to perform Connetics’ obligations under this Agreement in the same manner and to the same extent as Connetics would be required to perform such obligations in the absence of a succession. For all purposes under this Agreement, the term “Company” shall include any successor to Connetics’ business and/or assets which executes and delivers the assumption agreement described in this subsection (a) or which becomes bound by the terms of this Agreement by operation of law.

          (b) Consultant’s Successors. Without the written consent of Connetics, Consultant shall not assign or transfer this Agreement or any right or obligation under this Agreement to any other person or entity. Notwithstanding the foregoing, the terms of this Agreement and all rights of Consultant hereunder shall inure to the benefit of, and be enforceable by, Consultant’s personal or legal representatives, executors, administrators, successors, heirs, distributees, devisees and legatees.

     6. Notices.

          (a) General. Notices and all other communications contemplated by this Agreement shall be in writing and shall be deemed to have been duly given when they are personally

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delivered or when they are mailed by U.S. registered or certified mail, return receipt requested and postage prepaid. In the case of the Consultant, mailed notices shall be addressed to the Consultant at the home address which the Consultant most recently communicated to Connetics in writing. In the case of Connetics, mailed notices shall be addressed to its corporate headquarters, and all notices shall be directed to the attention of its Secretary.

          (b) Notice of Termination. Any termination by Connetics for Cause or by the Consultant as a result of a voluntary resignation or an Involuntary Termination shall be communicated by a notice of termination to the other party to this Agreement given in accordance with this Section. Such notice shall (i) indicate the specific termination provision in this Agreement relied upon, (ii) set forth in reasonable detail the facts and circumstances claimed to provide a basis for termination under the provision so indicated, and (iii) specify the Termination Date (which shall be not more than 30 days after the giving of such notice). If the Consultant fails to include in the notice any fact or circumstance which contributes to a showing of Involuntary Termination, that failure shall not waive any right of the Consultant under this Agreement or preclude the Consultant from asserting such fact or circumstance in enforcing his rights under this Agreement.

     7. Arbitration.

          (a) Disputes. Except as provided in Section 7(c) below, the Company and Consultant agree that any dispute or controversy arising out of, relating to or in connection with the interpretation, validity, construction, performance, breach or termination of this Agreement shall be settled by binding arbitration to be held in the county of Santa Clara, California, in accordance with the Commercial Arbitration Rules, supplemented by the Supplemental Procedures for Large Complex Disputes, of the American Arbitration Association as then in effect (the “Rules”). The arbitrator may grant injunctions or other relief in such dispute or controversy. The decision of the arbitrator shall be final, conclusive and binding on the parties to the arbitration. Judgment may be entered on the arbitrator’s decision in any court of competent jurisdiction.

          (b) Consent to Personal Jurisdiction. The arbitrator(s) shall apply California law to the merits of any dispute or claim, without reference to conflicts of law rules. Consultant hereby consents to the personal jurisdiction of the state and federal courts located in California for any action or proceeding arising from or relating to this Agreement or relating to any arbitration in which the parties are participants.

          (c) Equitable Relief. The parties may apply to any court of competent jurisdiction for a temporary restraining order, preliminary injunction, or other interim or conservatory relief, as necessary, without breach of this arbitration agreement and without abridgment of the powers of the arbitrator.

          (d) Acknowledgment. CONSULTANT HAS READ AND UNDERSTANDS SECTION 7, WHICH DISCUSSES ARBITRATION. CONSULTANT UNDERSTANDS THAT BY SIGNING THIS AGREEMENT, CONSULTANT AGREES TO SUBMIT ANY CLAIMS ARISING OUT OF, RELATING TO, OR IN CONNECTION WITH THIS AGREEMENT, OR THE INTERPRETATION, VALIDITY, CONSTRUCTION, PERFORMANCE, BREACH OR TERMINATION THEREOF, TO BINDING ARBITRATION, EXCEPT AS PROVIDED IN SECTION 7 (c), AND THAT THIS ARBITRATION CLAUSE CONSTITUTES A WAIVER OF CONSULTANT’S RIGHT TO A JURY TRIAL AND RELATES TO THE RESOLUTION OF ALL

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DISPUTES RELATING TO ALL ASPECTS OF THE RELATIONSHIP BETWEEN THE PARTIES.

     8. Miscellaneous Provisions.

          (a) No Duty to Mitigate. The Consultant shall not be required to mitigate the amount of any payment contemplated by this Agreement, nor shall any such payment be reduced by any earnings that the Consultant may receive from any other source.

          (b) Waiver. No provision of this Agreement may be modified, waived or discharged unless the modification, waiver or discharge is agreed to in writing and signed by the Consultant and by an authorized officer of Connetics. No waiver by either party of any breach of, or of compliance with, any condition or provision of this Agreement by the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time.

          (c) Integration. This Agreement and any other agreement referenced in this Agreement represent the entire agreement and understanding between the parties as to the subject matter of this Agreement and supersede all prior or contemporaneous agreements, whether written or oral, with respect to this Agreement.

          (d) Choice of Law. The validity, interpretation, construction and performance of this Agreement shall be governed by the internal substantive laws, but not the conflicts of law rules, of the State of California.

          (e) Severability. 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.

          (f) Counterparts. This Agreement may be executed in counterparts, each of which shall be deemed an original, but all of which together will constitute one and the same instrument.

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     IN WITNESS WHEREOF, each of the parties has executed this Agreement, in the case of Connetics by its duly authorized officer, as of the day and year first written above.

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