DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

Exhibit 10.29

Certain confidential information contained in this document, marked by brackets, is
filed with the Securities and Exchange Commission pursuant to Rule 24b-2 of the
Securities Exchange Act of 1934, as amended.

DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

     THIS DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (“ Agreement ”) dated as of February 7, 2007 (“ Effective Date ”), is entered into between XenoPort, Inc., a Delaware corporation having its principal place of business at 3410 Central Expressway, Santa Clara, CA 95051 (“ XenoPort ”) and Glaxo Group Limited, a company existing under the laws of England and Wales, having its registered office at Glaxo Wellcome House, Berkeley Avenue, Greenford, Middlesex, UB6 0NN, England (“ GSK ”).

BACKGROUND

     A. XenoPort is developing a Transported Prodrug™ of gabapentin (as further defined below, the “ Product ”) for the treatment of restless leg syndrome (“ RLS ”) and the management of neuropathic pain. XenoPort owns or controls certain patents, know-how and other intellectual property relating to such Product;

     B. GSK desires to co-develop and co-commercialize the Product with XenoPort in the United States (as hereinafter defined), and to further develop and commercialize the Product in other countries in the Territory (as hereinafter defined), and XenoPort desires to have the Product developed and commercialized in the Territory by and with GSK, in accordance with this Agreement; and

     C. GSK desires to obtain from XenoPort certain distribution and license rights for the Product in the Territory, and XenoPort is willing to grant to GSK such rights on the terms and conditions set forth in this Agreement;

     NOW, THEREFORE, in consideration of the foregoing premises and the mutual covenants herein contained, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties (as hereinafter defined) hereby agree as follows:

ARTICLE I

DEFINITIONS

     As used in this Agreement, the following capitalized terms will have the meanings set forth in this Article 1 when used in this Agreement.

     1.1 “ Affiliate ” of a Party shall mean any Person that, directly or indirectly through one or more intermediaries, controls, is controlled by or is under common control with such Party, as the

case may be, for as long as such control exists. As used in this Section 1.1, “ control ” shall mean: (a) to possess, directly or indirectly, the power to direct the management and policies of such Person, whether through ownership of voting securities or by contract relating to voting rights or corporate governance; or (b) direct or indirect beneficial ownership of at least fifty percent (50%) (or such lesser percentage that is the maximum allowed to be owned by a foreign corporation in a particular jurisdiction) of the voting share capital in such Person. A “ Controlled Affiliate ” is an Affiliate that [... * ...] .

     1.2 “ Annual Net Sales ” shall mean total Net Sales in a country or countries in the Territory in a particular calendar year.

     1.3 “ Anti-Kickback Statute ” means the Medicare and Medicaid Anti-Kickback Statute set forth at 42 U.S.C. §1320a-7b(b).

     1.4 “ Applicable Commercial Practices Policies ” means the portions as identified by GSK of the Commercial Practices Policies of GSK applicable (and as applied generally to GSK’s own personnel) to the marketing, sale, promotion and detailing of pharmaceutical products, as amended or supplemented by GSK from time to time, a copy of which will be delivered to XenoPort prior to XenoPort Co-Promoting and Detailing the Product and/or Detailing the REQUIP™ Products in the United States and updated copies will thereafter be delivered to XenoPort as and when amended or supplemented.

     1.5 “ Applicable Laws ” means the applicable provisions of any and all national, supranational, regional, state and local laws, treaties, statutes, rules, regulations, administrative codes, guidances, ordinances, judgments, decrees, directives, injunctions, orders, permits (including Marketing Approvals) of or from any court, arbitrator, Regulatory Authority or governmental agency or authority having jurisdiction over or related to the subject item.

     1.6 “ Asian Territory ” shall mean Indonesia, Japan, Korea, Philippines, Taiwan and Thailand.

     1.7 “ Astellas ” shall mean Astellas Pharma Inc. and its Affiliates, and any other Third Parties to whom Astellas or XenoPort has granted a right to sell, market, distribute and/or promote a Product in a country in the Asian Territory. To the extent Astellas’ rights in the Asian Territory terminate and XenoPort grants rights to a Third Party, references herein to Astellas shall be deemed to reference such Third Party.

     1.8 “ Astellas Agreement ” shall mean the Distribution and License Agreement dated December 1, 2005 between XenoPort and Astellas.

     1.9 “ Astellas Know-How ” shall mean any scientific, medical, technical, marketing, regulatory and/or other information, data and materials (including, preclinical data, clinical data, clinical pharmacology data and regulatory filings and approvals submitted or obtained, together with

its supporting data and regulatory correspondence and rights to reference the same) primarily relating to the Compound and/or any Product, which is Controlled by Astellas as of the Effective Date or during the Term; provided, however, that [... * ...] .

     1.10 “ Call ” shall mean a face-to-face meeting in an individual, hospital or group setting between a Sales Representative and one or more members of the Target Audience.

     1.11 “ Change of Control ” shall mean either: (a) a sale of all or substantially all of the assets of a Party in one or a series of integrated transactions not in the ordinary course of business to a Third Party; or (b) the acquisition of a Party by a Third Party by means of any transaction or series of related transactions to which such Party is a party (including, any stock acquisition, merger or consolidation). For clarity, a Change of Control would not include any transaction or series of transactions in which the holders of voting securities of a Party outstanding immediately prior to such transaction continue to retain (either by such voting securities remaining outstanding or by such voting securities being converted into voting securities of the surviving entity), as a result of shares in the Party held by such holders prior to such transaction, fifty percent (50%) or more of the total voting power represented by the voting securities of the acquiring entity outstanding immediately after such transaction or series of transactions.

     1.12 “ Commercially Reasonable Efforts ” shall mean that level of efforts and resources consistent with the usual practice followed by a Party in the exercise of reasonable business discretion relating to other pharmaceutical products owned by it or to which it has exclusive rights, which is of similar market potential and at a similar stage in development or product life, taking into account issues of patent coverage, safety and efficacy, product profile, the competitiveness of the marketplace, the proprietary position of the compound or product, the regulatory structure involved, the profitability of the products (including, without limitation, pricing and reimbursement status achieved), and other relevant factors, including without limitation technical, legal, scientific, and/or medical factors.

     1.13 “ Compound ” shall mean that certain compound, referred to internally at XenoPort as XP13512, the structure of which is set forth on Exhibit 1.13 , and all esters, hydrates, metabolites [... * ...] , salts, solvates, isomers and/or mixtures of isomers thereof.

     1.14 “ Control ” (including any variations such as “ Controlled ” and “ Controlling ”), in the context of intellectual property rights of a Party, shall mean that such Party or its Controlled Affiliate owns or possesses rights to intellectual property sufficient to grant the applicable license under this Agreement, without violating the terms of an agreement with a Third Party.

     1.15 “ Co-Promotion ” (including any variations such as “ Co-Promote ”) shall mean those promotional and sales activities undertaken by a pharmaceutical company’s sales force in concert with at least one other pharmaceutical company’s sales force in a single territory to implement the marketing and/or sales plans with respect to a particular prescription pharmaceutical product under the same trademark in such territory.

     1.16 “ Data ” shall mean any and all research data, pharmacology data, preclinical data, clinical data and/or all regulatory documentation, information and submissions pertaining to, or made in association with an IND, Marketing Approval Application, Marketing Approval or the like for the Product, in each case that are Controlled by a Party or its Controlled Affiliates as of the Effective Date or during the Term.

     1.17 “ Detail ” (including any variations such as “ Detailing ”) shall mean that part of the activity undertaken by a Sales Representative during a Call whereby a Sales Representative, who has been trained with respect to the REQUIP™ Products or the Product, as applicable, in accordance with Section 5.4(c), makes a presentation: (a) describing [... * ...] as applicable; (b) which may also include [... * ...] ; and (c) in accordance with the [... * ...] , as applicable. [... * ...] , shall not constitute a Detail. [... * ...] as applicable, shall not constitute a Detail. As used herein, a [... * ...] in which [... * ...] (as consistent with industry norms) [... * ...] .

     1.18 “ EMEA ” shall mean the European Medicines Agency of the European Union, or any successor entity thereto performing similar functions.

     1.19 “ Existing Phase III Studies ” shall mean those certain Phase III clinical studies [... * ...]

     1.20 “ FDA ” shall mean the United States Food and Drug Administration, or any successor entity thereto performing similar functions.

     1.21 “ FD&C Act ” means the federal Food, Drug and Cosmetic Act, as amended, and the regulations promulgated thereunder from time to time.

     1.22 “ Field ” shall mean the diagnosis, palliation, treatment and/or prevention of any disease or health condition in humans.

     1.23 “ Filing ” of an MAA shall be deemed to occur on the date of receipt of written notice of acceptance from the FDA in the United States, or other relevant Regulatory Authority outside of the United States, of such MAA for substantive review. Validation of an MAA by the EMEA shall be deemed to constitute acceptance of such MAA for substantive review in a Major Market (other than the United States) and, if an MAA is submitted under the EU mutual recognition procedure and validated by the relevant Regulatory Authority in the reference member state, such MAA shall be deemed to be accepted in a Major Market (other than the United States) upon confirmation that the resulting approval in the reference member state will serve as the basis for a mutual recognition procedure in such Major Market (other than the United States).

     1.24 “ First Commercial Sale ” shall mean, on a country-by-country basis and Product-by-Product basis, the first bona fide , arm’s length sale of a Product in a country following receipt of Marketing Approval of such Product in such country for use or consumption by the general public of such Product in such country. Sales of a Product for registration samples, compassionate use sales,

named patient use, inter-company transfers to Affiliates of a Party and the like will not constitute a First Commercial Sale.

     1.25 “ GSK Know-How ” shall mean all scientific, medical, technical, marketing, regulatory and other information primarily relating to the Product (including Data), which are Controlled by GSK or its Controlled Affiliates during the Term, that are needed by or reasonably useful to XenoPort in order for XenoPort to exercise its rights or perform its obligations under this Agreement and the Astellas Agreement; provided, however, that [... * ...] .

     1.26 “ GSK Trademarks ” shall mean the Trademarks Controlled by GSK or its Controlled Affiliates as of the Effective Date or during the Term, which are used with the Products in the Field in the Territory.

     1.27 “ IND ” shall mean any Investigational New Drug Application (including any amendments thereto) filed with the FDA pursuant to 21 C.F.R. §321 before the commencement of clinical trials of a Product, or any comparable filings with any Regulatory Authority in any other jurisdiction.

     1.28 “ Major Market ” shall mean the United States, France, Germany, Italy, Spain and/or the United Kingdom.

     1.29 “ Major Pharmaceutical Company ” shall mean a company that is engaged in the business of selling pharmaceutical products, whose revenues from such sales (on a consolidated basis in the last full fiscal year prior to the closing of any Change of Control) was in excess of [... * ...] . Any Affiliate of such company shall be deemed to be a Major Pharmaceutical Company.

     1.30 “ Marketing Approval ” shall mean all approvals, licenses, registrations or authorizations of the Regulatory Authority in a country, necessary for the manufacture, use, storage, import, marketing and sale of a Product in such country. For countries where governmental or other similar approval of pricing and/or reimbursement is required for marketing in such country, Marketing Approval shall not be deemed to occur until such pricing or reimbursement approval is obtained. Notwithstanding the foregoing, Marketing Approval shall be deemed to have occurred for a particular indication for a Product in such jurisdiction upon the First Commercial Sale of such Product in such jurisdiction with labeling for such indication.

     1.31 “ Marketing Approval Application ” (or “ MAA ”) shall mean a NDA submitted to the FDA in the United States or a corresponding application for Marketing Approval that has been submitted to a Regulatory Authority in any other country in the Territory.

     1.32 “ NDA ” shall mean a New Drug Application as defined in Title 21 of the U.S. Code of Federal Regulations, Section 314.50, et seq., which is filed with the FDA in order to gain the FDA’s approval to commercialize a pharmaceutical product in the United States for the indications set forth in the New Drug Application.

     1.33 “ Net Sales ” shall mean the gross invoice price by GSK or its Affiliates or Sublicensees, as the case may be, for all Products sold by of GSK, its Affiliates or Sublicensees (“ Selling Party ”) under this Agreement in a country or countries in the Territory in arm’s length sales to Third Parties less the following deductions that are actually incurred, allowed, paid, accrued or specifically allocated to the extent that such amounts are deducted from gross invoiced sales amounts as reported by the Selling Party in its financial statements in accordance with the International Financial Reporting Standards (“ IFRS ”), applied on a consistent basis:

     (a) trade, quantity and cash discounts and allowances;

     (b) credits, rebates and charge backs or equivalents thereof (including those to managed-care entities, national, state/provincial, local and other governments, their agencies and purchasers, and to trade customers);

     (c) allowances or credits to customers on account of rejection or returns (including wholesaler and retailer returns), retroactive price reductions affecting such Product or billing errors;

     (d) freight, postage and duties, and transportation charges relating to such Product (including handling and insurance thereto) separately identified on the invoice or other documentation maintained in the ordinary course of business;

     (e) sales (such as value-added tax or its equivalent) and excise taxes, other consumption taxes, customs duties and compulsory payments to governmental authorities and any other governmental charges imposed upon the sale of a Product to Third Parties;

     (f) commissions allowed or paid to Third Party wholesalers, or other similar Third Party distributors, in each case who do not engage in marketing or promotion of the Product;

     (g)  [... * ...] bad debt reported [... * ...] in which [... * ...] or [... * ...] or [... * ...] in which [... * ...] ; and

     (h) any other items actually deducted from (and therefore not included as) gross invoiced sales amounts in determining revenue, and not otherwise included as an item of income or the like, as reported by a Selling Party in its financial statements in accordance with the IFRS, applied on a consistent basis.

     Sales between GSK and its Affiliates or Sublicensees for resale shall be excluded from the computation of Net Sales, and no payments will be payable on such sales except where such Affiliates or Sublicensees are end users. If a Product is sold or transferred for consideration other than cash, the Net Sales from such sale or transfer shall be deemed the then fair market value of such Product. [... * ...]

     In the event that [... * ...] the Net Sales [... * ...] shall be [... * ...] during the applicable reporting period [... * ...] in which [... * ...] In the event that [... * ...] then Net Sales for purposes

of [... * ...] shall be [... * ...] on the [... * ...] shall not [... * ...] If [... * ...] as provided in this paragraph, the matter shall be resolved in accordance with Section 18.2 below.

     1.34 “ Neuropathic Pain Indication ” shall mean an indication for the Product involving [... * ...] .

     1.35 “ Party ” shall mean XenoPort or GSK individually, and “ Parties ” shall mean XenoPort and GSK collectively.

     1.36 “ Patent(s) ” shall mean any patents and patent applications, together with all additions, divisions, continuations, continuations-in-part, substitutions, reissues, re-examinations, extensions, registrations, patent term extensions, supplemental protection certificates and renewals of any of the foregoing.

     1.37 “ PDMA ” means the federal Prescription Drug Marketing Act of 1987, as amended, and the regulations promulgated thereunder from time to time.

     1.38 “ Person ” means any individual, corporation, partnership, firm, association, joint venture, joint stock company, trust or other entity, or any government or regulatory administrative or political subdivision or agency, department or instrumentality thereof.

     1.39 “ Phase I ” shall mean a human clinical trial, the principal purpose of which is to demonstrate safety, tolerability and pharmacokinetics of the Product in volunteer or patient subjects, as further described in 21 C.F.R. §312.21(a) (including, any such clinical study in any country other than the United States).

     1.40 “ Phase III ” shall mean a human clinical trial, the principal purpose of which is to establish safety and efficacy of the Product in patients with the disease being studied, as further described in 21 C.F.R. §312.21(c) (including, any such clinical study in any country other than the United States), which is designed and intended to be of a size and statistical power sufficient to serve as a pivotal study to support the filing of an MAA for the indication being studied.

     1.41 “ Phase IV ” shall mean a human clinical trial conducted with respect to a Product: (a) after [... * ...] ; (b) within the [... * ...] ; and (c) intended as [... * ...] . Phase IV studies may include, for example, [... * ...] , and the like. Phase IV studies shall not include any human clinical trials: (i) [... * ...] ; and/or (ii) from which [... * ...] for the purposes of: [... * ...] or [... * ...] provided that in the case of paragraph (ii), [... * ...] .

     1.42 “ PhRMA Code ” means the PhRMA Code on Interactions with Health Care Professionals, as amended.

     1.43 “ Product ” shall mean any pharmaceutical product containing the Compound, alone or in combination with one or more other active pharmaceutical ingredients, in any dosage form or formulation.

     1.44 “ Promotional Materials ” means all written, printed, video or graphic advertising, promotional, educational and communication materials [... * ...] for marketing, advertising, promotion and sale of the Product or the REQUIP™ Products, as applicable, for use in the United States (a) [... * ...] .

     1.45 “ Regulatory Authority ” shall mean the FDA, or a regulatory body with similar regulatory authority in any other jurisdiction within the Territory.

     1.46 “ Regulatory Filing ” means all approvals, licenses, registrations, submissions and authorizations made to or received from a Regulatory Authority in a country necessary for the development, manufacture and/or commercialization of a pharmaceutical product in the Territory, including any INDs, Marketing Approval Applications and Marketing Approvals.

     1.47 “ REQUIP™ Products ” shall mean those certain pharmaceutical products Controlled by GSK or its Affiliates as of the Effective Date, which contain ropinirole HCL as an active ingredient and are known as of the Effective Date as REQUIP CR and REQUIP XL 24h.

     1.48 “ REQUIP™ Trademarks ” shall mean shall mean the Trademarks Controlled by GSK or its Affiliates as of the Effective Date and during the Term, which are used with the REQUIP™ Products in the Field in the Territory.

     1.49 “ RLS Indication ” shall mean an indication for the Product involving RLS.

     1.50 “ Sales Representative ” shall mean a professional pharmaceutical sales representative engaged or employed by either Party to conduct sales activities and other promotional efforts with respect to a Product and/or the REQUIP™ Products.

     1.51 “ Samples ” shall mean individual physician sample units of the Product or the REQUIP™ Products, as applicable.

     1.52 “ Sublicensee ” shall mean a Third Party to whom GSK has granted a right to sell, market, distribute and/or promote a Product in the Territory pursuant to Section 2.2 and “ Sublicense ” shall mean an agreement or arrangement between GSK and a Sublicensee granting such rights. As used in this Agreement, “Sublicensee” shall not include a wholesaler or reseller of a Product who does not market or promote such Product.

     1.53 “ Target Audience ” means those health care professionals legally permitted to prescribe the Product or the REQUIP™ Products, as applicable, or issue hospital orders for the Product or the REQUIP™ Products, as applicable, in each case in the United States, or those other allied professionals that are part of the treatment team and who are recognized for this purpose in the Co-Promotion Plan or the REQUIP™ Sales Plan, as applicable.

     1.54 “ Territory ” shall mean worldwide, except for the Asian Territory.

     1.55 “ Third Party ” shall mean any Person other than XenoPort, GSK and their respective Affiliates.

     1.56 “ Trademarks ” means registered and unregistered trademarks, including words and logos, and any applications for registrations thereof, and intellectual property rights residing in such trademarks, including copyrights and design rights.

     1.57 “ United States ” or “ U.S. ” means the fifty (50) states of the United States of America and the District of Columbia.

     1.58 “ XenoPort Know-How ” shall mean all scientific, medical, technical, regulatory and other information primarily relating to the Compound and the Product (including the Data), which are Controlled by XenoPort or its Controlled Affiliates as of the Effective Date or during the Term, that were generated or utilized by XenoPort or its Controlled Affiliates in developing or producing the Product or are otherwise reasonably necessary for GSK to exercise its rights or perform its obligations under this Agreement; provided, however, that [... * ...] .

     1.59 “ XenoPort Patents ” shall mean: (a) the Patents Controlled by XenoPort or its Controlled Affiliates listed on Exhibit 1.59 , together with all additions, divisions, continuations, substitutions, re-issues, re-examinations, extensions, registrations, patent term extensions, supplemental protection certificates and renewals of any such Patents; and (b) all [... * ...] .

     1.60 “ XenoPort Trademarks ” shall mean the Trademarks Controlled by XenoPort or its Controlled Affiliates and reflected in Exhibit 1.60 hereto, the applications for which have been filed in the name of XenoPort, or another mutually agreed Trademark Controlled by XenoPort or its Affiliates, in each case for use with the Products in the Field in the Territory.

     1.61 Additional Definitions. Each of the following terms shall have the meaning described in the corresponding section of this Agreement indicated below:

ARTICLE II

GRANT OF LICENSE

     2.1 License . Subject to the terms and conditions of this Agreement, XenoPort hereby grants to GSK an exclusive license, with the right to grant sublicenses as provided in Section 2.2, under the XenoPort Patents and XenoPort Know-How to develop, use, make, have made, offer for sale, sell, import, market, distribute and promote the Compound and Products, in each case solely in the Field in the Territory. The rights and licenses in this Section 2.1 shall be exclusive even as to XenoPort, except with respect to: (a) [... * ...] in accordance with [... * ...] (b) [... * ...] in accordance with [... * ...] (c) [... * ...] in accordance with [... * ...] (d) [... * ...] and (e) [... * ...] .

     2.2 Sublicensees .

     (a) GSK shall have the right to sublicense its rights under this Agreement: (i) in any country in the Territory to its Affiliates; (ii) to a Third Party in a particular country in the Territory if neither GSK nor any of its Affiliates have direct sales operations in such country; and (iii) to Third Parties to permit such Third Parties to provide services to and on behalf of GSK relating to the manufacturing or development of the Product, in each case of (i) through (iii) without the consent of XenoPort. GSK may sublicense its rights as provided in this Section 2.2(a) to such Affiliates solely for so long as such Person remains an Affiliate.

     (b) Except as otherwise provided in Section 2.2(a), GSK may engage Sublicensees and grant Sublicenses in any country in the Territory [... * ...] To the extent that [... * ...] In addition, [... * ...] to the same extent [... * ...] . Promptly following the execution of each Sublicense as provided in this Section 2.2(b), [... * ...] .

     2.3 Activities Outside the Territory.

     (a) GSK agrees that neither it, nor any of its Controlled Affiliates, will sell or provide the Compound or the Products to any Third Party if GSK or its relevant Controlled Affiliate knows, or has reason to believe, that the Compound and/or the Products, as the case may be, sold or provided to such Third Party would be sold or transferred, directly or indirectly, for use in the Asian Territory.

     (b) XenoPort agrees that it and its Affiliates will not, and that it will use Commercially Reasonable Efforts to exercise its rights under any agreements with Astellas (including the Astellas Agreement) to cause Astellas not to, sell or provide the Compound or the

Product to any Third Party if XenoPort, its relevant Affiliate or Astellas knows, or has reason to believe, that the Compound and/or the Products, as the case may be, sold or provided to such Third Party would be sold or transferred, directly or indirectly, for use in the Territory; provided, however, that nothing in this Agreement (including this Section 2.3(b)) shall be deemed to [... * ...] ; and provided, further, that: (i) XenoPort shall [... * ...] ; and (ii) XenoPort will [... * ...] and/or [... * ...] to the extent that [... * ...] and provided that [... * ...] .

     (c) Subject to [... * ...] with respect to [... * ...] , XenoPort agrees to keep GSK reasonably informed through the JDC of [... * ...] relating to [... * ...] to the extent XenoPort [... * ...] XenoPort represents to GSK that XenoPort [... * ...] In addition, XenoPort agrees to [... * ...] or the [... * ...] and/or [... * ...] and/or [... * ...] .

     2.4 No Other Rights . Except for the rights and licenses expressly granted in this Agreement, XenoPort retains all rights under its intellectual property, and no additional rights shall be deemed granted to GSK by implication, estoppel or otherwise. For clarity, the licenses and rights granted in this Agreement shall not be construed to convey any licenses or rights under the XenoPort Patents with respect to any active pharmaceutical ingredient other than the Compound.

ARTICLE III

GOVERNANCE

     3.1 Executive Steering Committee .

     (a)  Establishment . Within thirty (30) days following the HSR Clearance Date, XenoPort and GSK shall establish an Executive Steering Committee (“ Executive Steering Committee ” or “ ESC ”) to oversee, review and coordinate the activities of the Parties under this Agreement, including, the development of the Product for registration, and the marketing, commercialization and distribution of Products, in the Field in the Territory, subject to the provisions of this Article 3.

     (b)  Duties . The ESC shall:

          (i) Review and approve material changes to the Development Plan;

          (ii) Review and approve material changes to the Commercialization Plan for the United States in the event that XenoPort has exercised the Co-Promotion Option as provided in Section 5.2(a);

          (iii) Review the Commercialization Plan for each Major Market country (including, in the event that XenoPort has not exercised the Co-Promotion Option as provided in Section 5.2(a), the United States);

          (iv) Provide a forum for the Parties to exchange information and coordinate their respective activities with respect to matters pertaining to the development, manufacture, marketing and distribution of the Products in the Territory, and matters pertaining to Regulatory Filings for the Product in the Territory;

          (v) Provide a forum for resolving matters to be decided by the JDC or JCC under this Agreement;

          (vi) Provide a forum to review with XenoPort decisions by GSK regarding material development, regulatory, manufacturing and commercial matters pertaining to the Product in the Territory that are not decided by the JDC or the JCC; and

          (vii) Perform such other duties as are specifically assigned to the ESC in this Agreement.

     (c)  Subcommittees . From time to time, the ESC may establish subcommittees to oversee particular projects or activities within the scope of authority of the ESC, as it deems necessary or advisable (each, a “ Subcommittee ”). Each Subcommittee shall consist of such number of representatives of each Party as the ESC determines is appropriate from time to time. Each Subcommittee shall meet with such frequency as the ESC shall determine. Each Subcommittee shall operate by unanimous vote in all decisions, with each Party having one (1) vote and with at least one (1) representative from each Party participating in such vote. If, with respect to a matter that is subject to a Subcommittee’s decision-making authority, the Subcommittee cannot reach unanimity, the matter shall be referred to the ESC, which shall resolve such matter in accordance with Section 3.6.

     3.2 Joint Development Committee .

     (a)  Establishment . Within thirty (30) days following the HSR Clearance Date, GSK and XenoPort shall establish a joint development committee (“ Joint Development Committee ” or “ JDC ”) to plan, oversee and coordinate the conduct of the development activities for the Product in the Territory.

     (b)  Duties . The JDC shall:

          (i) Subject to oversight by the ESC, determine the Development Plan in accordance with Section 4.1;

          (ii) Subject to and within the parameters of the Development Plan:

               (A) Oversee the implementation of the Development Plan, allocate responsibilities to each Party in connection with executing the Development Plan and review each Party’s execution of its responsibilities under the Development Plan (including review of the clinical trials conducted by each Party pursuant to the Development Plan); and

               (B) Approve certain regulatory matters as provided in Section 4.7 below;

          (iii) Present any proposed revisions or amendments to the Development Plan, and the results of development efforts, to the ESC as needed, but no less frequently than once each calendar half-year;

          (iv) Oversee XenoPort’s conduct of the Clinical Studies and Activities; and

          (v) Perform such other duties as are specifically assigned to the JDC in this Agreement or delegated to the JDC by the ESC.

     3.3 Joint Commercialization Committee .

     (a)  Establishment . Within thirty (30) days after XenoPort’s election to exercise its Co-Promotion Option under Section 5.2(a) below, GSK and XenoPort shall establish a joint commercialization committee (“ Joint Commercialization Committee ” or “ JCC ”) to oversee the conduct of the commercialization, marketing and Co-Promotion activities for Products in the United States.

     (b)  Duties . The JCC shall:

          (i) Subject to oversight by the ESC, review and approve the Commercialization Plan for the United States developed by GSK in accordance with Section 5.1(b);

          (ii) Review and approve the Co-Promotion Plan developed in accordance with Sections 5.2(b) and 5.2(c); and

          (iii) Perform such other duties as are specifically assigned to the JCC in this Agreement or delegated to the JCC by the ESC.

     3.4 Committee Membership .

     (a)  Membership . Subject to Section 3.4(b), the ESC, JDC and JCC (each, a “ Committee ”) shall each be composed of an equal number of representatives from each of GSK and XenoPort, selected by such Party. Unless the Parties otherwise agree, the exact number of representatives for each of GSK and XenoPort shall be: (a) with respect to the ESC, subject to Section 3.4(b), two (2) representatives, at least one (1) of whom shall be [... * ...] , or a delegate of such [... * ...] (or representative of [... * ...] ); provided that such delegate shall [... * ...] ; and (b) with respect to the JDC and the JCC, three (3) representatives, at least one (1) of whom shall [... * ...] , or a delegate of such [... * ...] (or representative of [... * ...] ); provided that such delegate shall be [... * ...] . Either Party may replace its respective Committee representatives at any time with prior written notice to the other Party; provided that the criteria for composition of each Committee set forth in the preceding sentence continues to be satisfied following any such

replacement of a Party’s representative on any such Committee. Each Committee will be chaired by a GSK representative and GSK may, from time to time and in its sole discretion, change the representative who serves as the chairperson on any Committee with prior written notice to XenoPort.

     (b)  Withdrawal from Committees . At any time during the Term and for any reason, XenoPort shall have the right to withdraw from participation in the Committees upon written notice to GSK, which notice shall be effective immediately upon receipt (“ Withdrawal Notice ”). Following the issuance of a Withdrawal Notice and subject to this Section 3.4(b), XenoPort’s representatives to the Committees shall not participate in any meetings of the Committees, nor shall XenoPort have any right to vote on decisions within the authority of the Committees. If, at any time, following the issuance of a Withdrawal Notice, XenoPort wishes to resume participation in the Committees, XenoPort shall notify GSK in writing and, thereafter, XenoPort’s representatives to the Committees shall be entitled to attend any subsequent meeting of the Committees and to participate in the activities of, and decision-making by, the Committees as provided in this Article 3 as if a Withdrawal Notice had not been issued by XenoPort pursuant to this Section 3.4(b). Following XenoPort’s issuance of a Withdrawal Notice pursuant to this Section 3.4(b), unless and until XenoPort resumes participation in the Committees in accordance with this Section 3.4(b): (i) all meetings of the Committees shall be held at GSK’s facilities; (ii) GSK shall have the right to make the final decision on all matters within the scope of authority of the Committees; and (iii) XenoPort shall have the right to continue to receive the minutes of Committee meetings, but shall not have the right to approve the minutes for any Committee meeting held after XenoPort’s issuance of a Withdrawal Notice.

     3.5 Committee Meetings . The ESC shall meet at least once each calendar half-year, or more or less often as otherwise agreed to by the Parties. The JDC and, from and after such time as is appropriate, the JCC shall meet at least once each calendar quarter, or more or less often as otherwise agreed to by the Parties. All Committee meetings may be conducted by telephone, video-conference or in person as determined by the applicable Committee; provided, however, that each Committee shall meet in person at least twice each calendar year, unless the Parties mutually agree to meet by alternative means. Unless otherwise agreed by the Parties, all in-person meetings for each Committee shall be held on an alternating basis between XenoPort’s facilities and GSK’s facilities. Each Party shall bear its own personnel and travel costs and expenses relating to Committee meetings. With the consent of the Parties (not to be unreasonably withheld or delayed), other employee representatives of the Parties may attend any Committee meeting as non-voting observers. Minutes of each Committee meeting will be prepared by the chairperson and distributed to the members of the applicable Committee for review and comment within twenty (20) days after each meeting of the applicable Committee, and will be approved as the first order of business at the immediately succeeding Committee meeting.

     3.6 Decision-Making . Subject to Section 3.4(b), decisions of each Committee shall be [... * ...] . In the event the JDC or the JCC [... * ...] with respect to a particular matter within its authority, then upon request by either Party such matter shall be referred to the ESC for

resolution. In the event that the ESC [... * ...] with respect to a particular matter [... * ...] as requested by [... * ...] . The Parties’ [... * ...] to resolve such matter; provided, however that with respect to [... * ...] . If, [... * ...] are unable to resolve such matter [... * ...] .

     3.7 Alliance Managers . Within thirty (30) days following the HSR Clearance Date, each Party shall appoint a representative (“ Alliance Manager ”) to facilitate communications between the Parties (including coordinating the exchange of Data and Know-How of each Party as required under this Agreement) and to act as a liaison between the Parties with respect to such other matters as the Parties may mutually agree in order to maximize the efficiency of the collaboration. Each Party may replace its Alliance Manager with an alternative representative satisfying the requirements of this Section 3.7 at any time with prior written notice to the other Party.

     3.8 Scope of Governance . Notwithstanding the creation of the ESC, JDC and JCC, each Party shall retain the rights, powers and discretion granted to it hereunder, and no Committee shall be delegated or vested with rights, powers or discretion unless such delegation or vesting is expressly provided herein, or the Parties expressly so agree in writing. No Committee shall have the power to amend or modify this Agreement, and no decision of any Committee shall be in contravention of any terms and conditions of this Agreement. It is understood and agreed that issues to be formally decided by the ESC, JDC and JCC, as applicable, are only those specific issues that are expressly provided in this Agreement to be decided by the ESC, JDC and JCC, as applicable.

ARTICLE IV

DEVELOPMENT AND REGULATORY ACTIVITIES

     4.1 Development Plans .

     (a)  Initial Development Plan . An initial development plan for the collaboration is attached to this Agreement as Exhibit 4.1 (“ Development Plan ”) and sets out separately the development activities to be conducted by each Party. Within [... * ...] the HSR Clearance Date, the JDC shall review and finalize the details of the Development Plan, which shall be consistent with the Development Plan in Exhibit 4.1 .

     (b)  Changes to a Development Plan . The JDC shall review the Development Plan on an ongoing basis, and in no event less frequently than [... * ...] . The JDC may propose to the ESC revisions to the then-current Development Plan; provided, however, the [... * ...] .

     4.2 Development Activities of GSK .

     (a)  Conduct of Development Activities . Except as provided in Section 4.3 below, GSK shall, at its expense, use Commercially Reasonable Efforts to carry out all clinical development and other activities required to obtain Marketing Approvals for the Product in the Territory. GSK

shall carry out all such activities in accordance with the then-current Development Plan and the provisions of this Agreement.

     (b)  Diligence . GSK shall use Commercially Reasonable Efforts to achieve the goals of the then-current Development Plan in accordance with the timelines specified therein and to realize the commercial opportunity for the Product in other indications.

     4.3 Development Activities of XenoPort .

     (a)  Conduct of Development Activities . Except as otherwise mutually agreed, XenoPort shall, at its expense and with oversight by the JDC, continue to conduct the Existing Phase III Studies and those other clinical studies and activities listed on Exhibit 4.3 to this Agreement (collectively, the “ Clinical Studies and Activities ”). XenoPort shall make reasonable modifications to the protocols for such Clinical Studies and Activities, as requested by GSK from time to time; provided, however, that [... * ...] . Notwithstanding the foregoing, [... * ...] Existing Phase III Study [... * ...] of such modifications. In addition, XenoPort shall [... * ...] Clinical Studies and Activities [... * ...] Existing Phase III Studies, [... * ...] .

     (b)  Diligence . XenoPort shall use Commercially Reasonable Efforts to conduct and complete the Clinical Studies and Activities in order to achieve the goals of the then-current Development Plan in accordance with the timelines specified therein.

     4.4 Change in Formulation. Before [... * ...] , GSK shall discuss the proposed [... * ...] with XenoPort at the ESC and [... * ...] . Subject to the foregoing, XenoPort agrees that GSK may [... * ...] that were so discussed [... * ...] by the ESC.

     4.5 Conduct of Activities . Each Party shall conduct those activities allocated to such Party under the Development Plan in compliance in all material respects with all Applicable Laws and in accordance with good scientific and clinical practices, applicable under the Applicable Law of the country in which such activities are conducted.

     4.6 Regulatory Matters .

     (a)  Assignment of Regulatory Filings . At a reasonable time [... * ...] , XenoPort shall assign or cause to be assigned to GSK all Regulatory Filings for the Compound in the Territory; provided, however, that, [... * ...] XenoPort shall maintain [... * ...] . Notwithstanding the foregoing, it is understood that XenoPort may [... * ...] and/or [... * ...] provided that [... * ...] For such purposes, [... * ...] at which XenoPort [... * ...] .

     (b)  Responsibility for Regulatory Filings . Except for [... * ...] , GSK shall be responsible, at its expense, for filing, obtaining and maintaining all Regulatory Filings for the Compound and each Product in the Territory. [... * ...] . GSK shall also obtain any export approvals required by the FDA to import or export the Product to any country within the Territory. All such

filings will be in the name of GSK, except where otherwise required by Applicable Law in any country within the Territory.

          4.7 Regulatory Cooperation . [... * ...] , GSK shall be responsible for liaising with and managing all interactions with Regulatory Authorities in the Territory, including with respect to all Regulatory Filings for Product in the Territory, other than [... * ...] , and XenoPort shall be entitled to participate in such interactions as provided in this Section 4.7.

          (a) Involvement of XenoPort . To the extent relating to the Product within the [... * ...] or [... * ...] , GSK shall provide XenoPort with:

               (i) reasonable advanced notice [... * ...] of substantive meetings with the [... * ...] that are either scheduled with, or initiated by or under the authority of, GSK or its Affiliates;

               (ii) an opportunity to have [... * ...] representatives attend, and [... * ...] , all substantive meetings with [... * ...] ; and in any case, GSK shall keep the JDC informed as to all material interactions with Regulatory Authorities; and

               (iii) a copy of any material documents, information and correspondence submitted to [... * ...] relating to Regulatory Filings for the Product as soon as reasonably practicable, together with English translations and summaries thereof, to the extent such translations and summaries exist.

     The JDC shall approve the overall strategy and positioning of all [... * ...] Regulatory Filings with [... * ...] , based upon reasonably detailed reports and summaries of such submissions and filings presented to the JDC by GSK. In connection with such review, [... * ...] .

          (b) Involvement by GSK . With respect to the Regulatory Filings maintained by XenoPort under Section 4.6(a) and Regulatory Filings relating to the trials permitted to be conducted by XenoPort in the Territory under Section 2.3(b) above, XenoPort shall provide GSK with:

               (i) reasonable advanced notice [... * ...] of substantive meetings with the [... * ...] that are either scheduled with, or initiated by or under the authority of, XenoPort or its Affiliates relating to such Regulatory Filings;

               (ii) an opportunity to have [... * ...] representatives attend, and [... * ...] , all substantive meetings with [... * ...] relating to such Regulatory Filings; and in any case, XenoPort shall keep the JDC informed as to all material interactions with Regulatory Authorities relating to such Regulatory Filings; and

               (iii) a copy of any material documents, information and correspondence submitted to [... * ...] relating to such Regulatory Filings as soon as reasonably practicable, together with English translations and summaries thereof, to the extent such translations and summaries exist.

     (c)  Assistance by XenoPort . XenoPort will provide reasonable cooperation and assistance to GSK in the event that GSK must respond to questions from Regulatory Authorities in the Territory concerning development activities conducted by or on behalf of XenoPort with the Compound or Product, including the Clinical Studies and Activities.

     (d)  Other Regulatory Matters . Each Party will promptly provide the other Party with copies of all material documents, information and correspondence received from a Regulatory Authority (including a written summary of any material communications in which such other Party did not participate) within the Territory and, upon reasonable request, with copies of any other documents, reports and communications from or to any Regulatory Authority within the Territory relating to the Compound, the Product and/or activities under this Agreement.

     4.8 Exchange of Data and Know-How .

     (a)  By XenoPort . Promptly following the HSR Clearance Date, XenoPort will make available to GSK, at no cost or expense to GSK, all XenoPort Know-How that is necessary, or materially useful, for GSK to develop and/or commercialize the Compound and Products in the Territory, including all Data from any and all clinical trials (including the Clinical Studies and Activities) and preclinical studies and non-clinical development work for the Compound and Products that have been obtained by XenoPort as of the Effective Date.

     (b)  By Either Party . During the Term, each Party shall provide to the other Party all such Party’s Know-How (i.e., in case of XenoPort, XenoPort Know-How, and in the case of GSK, all GSK Know-How) and that has not previously been provided hereunder, in each case promptly upon request by the other Party. The Party providing such Party’s Know-How shall provide the same in electronic form to the extent the same exists in electronic form, and shall provide copies as reasonably requested and an opportunity for the other Party or its designee to inspect (and copy) all other materials comprising such Know-How (including for example, original patient report forms and other original source data). The Parties will cooperate and reasonably agree upon formats and procedures to facilitate the orderly and efficient exchange of the XenoPort Know-How and the GSK Know-How. [... * ...] ; provided that [... * ...] or [... * ...] . For the avoidance of doubt, [... * ...] . Accordingly, and consistent with the proviso in the fourth sentence of this Section 4.8(b), XenoPort shall [... * ...] .

     (c)  Provision of Data to JDC . Upon request by the JDC, each Party shall promptly provide the JDC with summaries in reasonable detail of all Data generated or obtained in the course of such Party’s performance of activities under a Development Plan.

     4.9 Sharing of Regulatory Filings. Without limiting Section 4.8 above, each Party shall permit the other to access, and shall provide the other Party with sufficient rights to reference and use in association with exercising its rights and performing its obligations under this Agreement [... * ...] , all of such Party’s, its Affiliates’ and, to the extent it has the right to do so, its Sublicensees’ Data, Regulatory Filings and regulatory communications associated with any

submissions of MAAs or other approvals for the Product respectively in the Territory. Without limiting the foregoing, XenoPort shall permit GSK to access and shall provide GSK with sufficient rights to reference and use, in support of MAAs filed and Marketing Approvals received by or on behalf of GSK, the IND of XenoPort for the Compound in the Territory. Notwithstanding the foregoing, GSK shall be obligated to [... * ...] .

     4.10 Inspection Right.

     (a)  Inspection by Astellas . To the extent any Regulatory Authority [... * ...] requests an audit of the clinical trial sites and, if GSK supplies Compound or Product to Astellas during the Term, manufacturing sites in the Territory [... * ...] , GSK shall permit such Regulatory Authority [... * ...] to enter the all relevant clinical trial sites and, if applicable, manufacturing sites of GSK and its Affiliates during normal business hours and upon reasonable advance notice to inspect and verify compliance with applicable regulatory requirements. GSK shall, at XenoPort’s expense, provide reasonable assistance for a full and correct carrying out of the inspection. Such inspection shall not relieve GSK of any of its obligations under this Agreement.

     (b)  Diligence . GSK shall use Commercially Reasonable Efforts to secure the rights set forth in Section 4.10(a) from GSK’s Sublicensees, trial sites and other contractors for the Product. In the event GSK is unable to secure such inspection rights from any of its Sublicensees, trial sites or contractors, GSK agrees to secure such rights for itself and [... * ...] GSK shall exercise such rights [... * ...] and fully report the results thereof to XenoPort and Astellas.

     4.11 Clinical Trial Register. Notwithstanding anything in this Agreement to the contrary, including Article XI, GSK shall have the right to publish in its clinical trial register the results or summaries of the results of all clinical trials for the Compound and Products conducted: (a) by either Party in the Territory pursuant to this Agreement; and (b) by [... * ...] provided, however, that [... * ...] . The Parties will discuss the process for [... * ...] .

     4.12 Reporting; Adverse Drug Reactions .

     (a)  Pharmacovigilance Agreement . Within ninety (90) days after the HSR Clearance Date, the Parties shall enter into a pharmacovigilance agreement on terms no less stringent than those required by ICH guidelines, including: (i) providing detailed procedures regarding the maintenance of core safety information and the exchange of safety data relating to the Compound and the Products for the Territory within appropriate timeframes and in an appropriate format to enable each Party to meet both expedited and periodic regulatory reporting requirements; and (ii) ensuring compliance with the reporting requirements of all applicable Regulatory Authorities on a worldwide basis for the reporting of safety data in accordance with standards stipulated in the ICH Guidelines, and all applicable regulatory and legal requirements regarding the management of safety data.

     (b)  Adverse Event Reporting . As between the Parties: (i) XenoPort shall be responsible for [... * ...] (ii) GSK shall be responsible for [... * ...] and (iii) XenoPort or Astellas shall be responsible for [... * ...] all in accordance with the Applicable Laws of the relevant countries and regulatory authorities. GSK shall ensure that its Affiliates and Sublicensees comply with such reporting obligations in the Territory, and XenoPort [... * ...]

     (c)  Global Safety Database . GSK shall maintain the global safety database with respect to the Product for the Territory and [... * ...] XenoPort agrees to [... * ...] enable GSK to maintain such global safety database for [... * ...] .

ARTICLE V

COMMERCIALIZATION AND PROMOTION

     5.1 GSK Commercialization of Product .

     (a)  GSK’s Responsibility . Except as provided below, GSK shall have sole responsibility for the commercialization, distribution, marketing and promotion of the Products in the Field in the Territory. Further, regardless of whether XenoPort exercises the Co-Promotion Option as provided in Section 5.2 below, during the Term, GSK will have the exclusive right and responsibility in the Territory for the following:

          (i) establishing pricing and reimbursement for Product;

          (ii) managed care contracting for Product;

          (iii) receiving, accepting and filling orders for Product from customers;

          (iv) distributing Product to customers;

          (v) controlling invoicing, order processing and collecting accounts receivable for sales of Product; and

          (vi) recording sales of Product in the Territory in its books of account for sales.

     (b)  Commercialization Plan . At least [... * ...] , GSK shall prepare [... * ...] a plan setting forth the strategic plan for the marketing, promotion and commercialization of the Products in such [... * ...] , which plan shall be in reasonable scope and detail (the “ Commercialization Plan ”); provided, however, that [... * ...] ; provided further that [... * ...] with respect thereto, [... * ...] . Each Commercialization Plan for [... * ...] shall be presented by GSK to the ESC or the JCC [... * ...] , as applicable. The ESC and the JCC [... * ...] shall review the Commercialization Plans for [... * ...] on an ongoing basis, and in no event less frequently than once each calendar year. Subject to Section 5.2, GSK shall carry out all marketing, promotion and

commercialization of the Products in the Territory in accordance with the then-current Commercialization Plan and the provisions of this Agreement.

     5.2 Co-Promotion Option of XenoPort .

     (a)  Exercise of Co-Promotion Option . XenoPort shall have a non-sublicensable option to Co-Promote the Product with GSK in the United States (“ Co-Promotion Option ”) in accordance with the terms and conditions of this Article 5. To facilitate such Co-Promotion Option, GSK shall notify XenoPort of its right to exercise the Co-Promotion Option [... * ...] . To exercise the Co-Promotion Option, XenoPort shall notify GSK in writing [... * ...] ; provided that [... * ...] . In the event that XenoPort exercises the Co-Promotion Option as provided in this Section 5.2(a), XenoPort will have an exclusive right to Co-Promote and Detail the Product with GSK in the United States until [... * ...] . In the event that XenoPort does not exercise the Co-Promotion Option as provided in this Section 5.2(a) or if XenoPort does not provide written notice to GSK that it is exercising the Co-Promotion Option [... * ...] , XenoPort will have no right to Co-Promote or Detail the Product with GSK in the United States, and GSK will have no further obligation with respect to the Co-Promotion Option.

     (b)  Co-Promotion Plan . In the event that XenoPort exercises the Co-Promotion Option, GSK shall prepare, in consultation with XenoPort and the JCC, the tactical plan for promoting and marketing the Product in the United States, consistent with the Commercialization Plan for the United States (“ Co-Promotion Plan ”), which shall be reviewed and approved by the JCC [... * ...] . The Co-Promotion Plan shall set out in reasonable detail: (i) [... * ...] in connection with the Co-Promotion [... * ...] (ii) [... * ...] (iii) [... * ...] and (iv) [... * ...] .

     (c)  Changes to the Co-Promotion Plan . After the submission of the initial Co-Promotion Plan, the JCC shall review and amend if necessary the Co-Promotion Plan on an ongoing basis and in no event less frequently than [... * ...] .

     (d)  Sales Efforts .

          (i) The Parties shall each use Commercially Reasonable Efforts to Co-Promote and Detail the Product in the United States pursuant to the terms and conditions hereof and the then-current Co-Promotion Plan. The JCC will agree upon and monitor each Party’s Co-Promotion and Detailing activities for each Co-Promotion Year. “ Co-Promotion Year ” shall mean, for the calendar year in which the Parties are first engaged in Co-Promotion, the portion of the calendar year remaining beginning upon the date of the First Commercial Sale in the United States, and shall mean the relevant January 1 through December 31 calendar year, or pro rata portion thereof, for all subsequent calendar years until the expiration or earlier termination of XenoPort’s right to Co-Promote the Product as provided herein.

          (ii) During any Co-Promotion Year, XenoPort shall use Commercially Reasonable Efforts to [... * ...] the Co-Promotion Plan approved by the JCC [... * ...] .

          (iii) The Co-Promotion Plan approved by the JCC for each Co-Promotion Year shall: (A) specify [... * ...] to be provided [... * ...] the number of Sales Representatives [... * ...] (B) [... * ...] in a manner that ensures [... * ...] to be provided [... * ...] and (C) to the extent [... * ...] Sales Representatives that [... * ...] .

     (e)  Sales Efforts of XenoPort . At the time XenoPort exercises the Co-Promotion Option, it shall notify GSK of the number of Sales Representatives that XenoPort elects to deploy initially for the Product, provided that [... * ...] . Promptly after such exercise of the Co-Promotion Option, XenoPort will [... * ...] of Sales Representatives that XenoPort so elects, [... * ...] in accordance with the Co-Promotion Plan [... * ...] . XenoPort shall, as requested by GSK, within [... * ...] ; provided that, subject to [... * ...] Sales Representatives that XenoPort deploys [... * ...] . In the event that XenoPort desires to increase the number of XenoPort Sales Representatives who Detail and Co-Promote Product [... * ...] in accordance with the Co-Promotion Plan, [... * ...] Co-Promoting and Detailing the Product as provided herein [... * ...] . In the event that GSK does not agree to using such Additional Sales Representatives in the Co-Promotion and Detailing of the Product, XenoPort will [... * ...] .

     (f)  Costs of Co-Promotion . If XenoPort exercises its Co-Promotion Option as provided in Section 5.2(a), the Parties shall [... * ...] . Notwithstanding the foregoing GSK shall [... * ...] in accordance with the Co-Promotion Plan [... * ...] . Such [... * ...] .

     (g)  Co-Promotion Coordination . GSK shall be responsible for developing the strategies and programs to carry out the Co-Promotion activities, including the assignment of sales activities in accordance with the Commercialization Plan for the United States and Co-Promotion Plan.

     5.3 Non-exclusive Right to Detail the REQUIP™ Products .

     (a)  Commencement of Right to Detail the REQUIP™ Products . If XenoPort exercises the Co-Promotion Option for the Product, XenoPort shall also obtain a non-sublicensable, non-exclusive right to Detail the REQUIP™ Products in the United States on and from the date on which XenoPort exercises its Co-Promotion Option, to the extent such REQUIP™ Products are approved for commercialization in the United States. Such right shall continue until [... * ...] . If GSK (or its Affiliate) has not obtained the approvals required to commercialize the REQUIP™ Products in the United States at the time that XenoPort exercises the Co-Promotion Option, the Parties [... * ...] .

     (b)  The REQUIP™ Sales Plan . GSK shall prepare and determine, in consultation with XenoPort, the tactical plan for XenoPort’s Detailing of the REQUIP™ Products by XenoPort Sales Representatives in the United States (the “ REQUIP™ Sales Plan ”) and shall provide the REQUIP™ Sales Plan to XenoPort [... * ...] . The REQUIP™ Sales Plan shall set out in reasonable detail: (i) [... * ...] in connection with [... * ...] and (ii) [... * ...] under such REQUIP™ Sales Plan, [... * ...] and which is [... * ...] . XenoPort shall be entitled to dedicate a number of Sales

Representatives elected by XenoPort, up to [... * ...] , to Detail the REQUIP™ Products in the United States. XenoPort’s right to deploy such Sales Representatives shall commence [... * ...] .

     (c)  Coordination . GSK shall be responsible for developing strategies and programs to carry out in an optimal fashion Detailing activities of the Parties with respect to the REQUIP™ Products, including the assignment of Detailing activities in accordance with the REQUIP™ Sales Plan.

     (d)  Reimbursement . GSK shall reimburse XenoPort for each Detail provided by the XenoPort Sales Representatives Co-Promoting the REQUIP™ Products in the United States in accordance with the REQUIP™ Sales Plan in an amount equal to: (i) [... * ...] and/or [... * ...] and (ii) [... * ...] . Such reimbursements shall be made to XenoPort [... * ...] .

     (e)  GSK’s Exclusive Responsibilities for the REQUIP™ Products . During the period that XenoPort is Detailing the REQUIP™ Products in the United States as provided herein, GSK will have the exclusive right and responsibility in the United States for the following:

          (i) establishing pricing and reimbursement for the REQUIP™ Products;

          (ii) managed care contracting for the REQUIP™ Products;

          (iii) receiving, accepting and filling orders for the REQUIP™ Products from customers;

          (iv) distributing the REQUIP™ Products to customers;

          (v) controlling invoicing, order processing and collecting accounts receivable for sales of the REQUIP™ Products;

          (vi) all marketing and promotion activities relating to the REQUIP™ Products other than Detailing; and

          (vii) recording sales of the REQUIP™ Products in the Territory in its books of account for sales.

     5.4 XenoPort Sales Representatives .

     (a)  Qualifications . All XenoPort Sales Representatives Co-Promoting and Detailing Product and/or Detailing the REQUIP™ Products shall be required to have comparable educational qualifications and experience as GSK requires for its own Sales Representatives. Such XenoPort Sales Representatives shall be subject to a reasonable proficiency examination relevant to the Product or the REQUIP™ Products in the same manner as GSK’s Sales Representatives.

     (b)  No Contract Sales Force . XenoPort shall not be permitted to use a contract sales force to fulfill its Co-Promotion and Detailing responsibilities with respect to the Product and/or Detailing responsibilities with respect to the REQUIP™ Products under this Agreement.

     (c)  Training . GSK shall provide the same sales training on the Product and on the REQUIP™ Products for XenoPort Sales Representatives who will be Co-Promoting and Detailing the Product and/or promoting the REQUIP™ Products, as applicable, as the training on the Product and the REQUIP™ Products that GSK provides to its own Sales Representatives who promote and Detail the Product and/or the REQUIP™ Products, as applicable, in the United States. XenoPort shall be responsible for causing its Sales Representatives to attend and successfully complete the GSK training program prior to such Sales Representatives Co-Promoting and Detailing Product and/or Detailing the REQUIP™ Products in the United States. The Parties acknowledge and agree that in order for a XenoPort Sales Representative to be deemed to have successfully completed the training, such XenoPort Sales Representative must demonstrate thorough knowledge of the medical and technical aspects of the Product and/or the REQUIP™ Products, as applicable, the Applicable Commercial Practices Policies and must achieve scores on certifications for the Product and the REQUIP™ Products, as applicable, at similar rates to those required for GSK sales representatives who are Co-Promoting and Detailing the Product and/or Detailing the REQUIP™ Products, as applicable. XenoPort Sales Representatives will be entitled to attend those sections of national and regional sales or plan of action meetings for GSK Sales Representatives, except [... * ...] . The costs of such sales training for XenoPort Sales Representatives for the Product and attendance at meetings shall [... * ...] .

     (d)  Timing . XenoPort and GSK shall cooperate to have the XenoPort Sales Representatives hired and trained as provided in this Agreement prior to [... * ...] .

     (e)  Compensation and Bonus System for Sales Representatives . The Parties acknowledge that in order to attract and retain professional Sales Representatives, there may be a degree of discrepancy between the compensation and bonus incentive structure for GSK’s Sales Representatives and the compensation and bonus incentive structure for XenoPort’s Sales Representatives. To ensure consistency of efforts between the Sales Representatives of the Parties, each Party agrees that in designing such Party’s compensation and bonus incentive structure, each Party will give due consideration to the effect that such Party’s compensation and bonus structure may have on the other Party’s sales force, provided that [... * ...] .

     (f)  XenoPort Salaries and Wages . XenoPort acknowledges and agrees that it will be solely responsible for paying all salaries, wages, benefits and other compensation that its employees, including XenoPort Sales Representatives, may be entitled to receive in connection with providing services under this Agreement.

     (g)  Support . Except as otherwise agreed, XenoPort shall be solely responsible for providing its own equipment, automobiles, offices and fixtures, working facilities, and such other facilities, services and support as may be required for XenoPort Sales Representatives Co-Promoting

and Detailing Product and/or Detailing the REQUIP™ Products as provided in this Agreement and pursuant to the Co-Promotion Plan or REQUIP™ Sales Plan, as applicable.

     (h)  No Employment by GSK . For the avoidance of doubt, XenoPort Sales Representatives will not be, and will not be considered or deemed to be, employees of GSK for any purpose. GSK is engaging XenoPort hereunder, and XenoPort will perform its obligations hereunder, strictly as an “independent contractor.” Sales Representatives and any other employee or agent that is involved in performing XenoPort’s obligations under this Agreement (collectively, “ Personnel ”) will not be, and will not be considered or deemed to be, employees of GSK for any purpose. GSK will not have any responsibility for the hiring, termination, compensation, benefits or other conditions of employment or engagement of the Personnel of XenoPort.

     (i)  GSK Benefit Plans . Personnel of XenoPort are not eligible to participate in any benefit programs offered by GSK to its employees, or in any pension plans, profit sharing plans, insurance plans or any other employee benefit plans offered from time to time by GSK to its employees. XenoPort acknowledges and agrees that GSK does not, and will not, maintain or procure any workers’ compensation or unemployment compensation insurance for or on behalf of the XenoPort’s employees, including, without limitation, XenoPort Sales Representatives. Personnel of XenoPort are not eligible to participate in any benefits programs offered by GSK to its employees, or in any pension plans, profit sharing plans, insurance plans or any other employee benefits plans offered from time to time by GSK to its employees.

     (j)  Management of Sales Representatives . XenoPort will be responsible for supervising its Sales Representatives. In connection therewith, at all times that XenoPort is Co-Promoting and Detailing the Product and/or Detailing the REQUIP™ Products, XenoPort will provide a sufficient number of full time employees to serve as district managers. XenoPort may, but will not be obligated to, designate one (1) or more full time employees to serve as regional directors having the responsibility for supervising a group of its district managers in a particular geographic region of the United States. XenoPort will provide GSK with contact information for its district managers and regional directors, and will update that information periodically or as requested by GSK from time to time. XenoPort acknowledges and agrees that it comply with this Section 5.4 in the hiring and employment of all district managers and regional directors, and that the provisions in this Section 5.4 will apply to all such district managers and regional directors.

     5.5 Co-Promotion Agreement . Promptly following XenoPort’s exercise of its Co-Promotion Option for the Product in accordance with Section 5.2(a), for the purposes of permitting GSK to comply with its obligations under Applicable Law, GSK and XenoPort shall enter into a co-promotion agreement setting out such obligations of XenoPort, including with respect to the activities of its Sales Representatives, in the Co-Promotion and Detailing of the Product and the Detailing of the REQUIP™ Products and containing terms substantially similar to the terms set out on Exhibit 5 and which is consistent with the terms and conditions of this Agreement (“ Co-Promotion Agreement ”). Notwithstanding the foregoing, the obligations imposed on XenoPort, including with respect to the activities of its Sales Representatives, in the Co-Promotion and

Detailing of the Product and the Detailing of the REQUIP™ Products, including the terms of the Co-Promotion Agreement to be executed by GSK and XenoPort as provided in this Section 5.5, shall be [... * ...] . It is understood that XenoPort may continue to exercise its rights under this Article 5 pending completion of such Co-Promotion Agreement, provided however, that [... * ...] .

     5.6 Promotional Materials .

     (a) Subject to Article XIII, GSK will own all right, title and interest in and to all Promotional Materials during and after the Term, including any intellectual property rights (including Trademarks) in the Promotional Materials other than the XenoPort Trademarks.

     (b) The determination of the content of the Promotional Materials shall be the sole responsibility of GSK. The quantity and method of distribution of the Promotional Materials in the United States for the XenoPort Sales Representatives shall be as set forth in the Co-Promotion Plan or the REQUIP™ Sales Plan, as applicable.

     (c) With respect to the Co-Promotion of the Product, XenoPort will cause its Sales Representatives to utilize only the Promotional Materials relating to Product provided to them by GSK, and will not utilize any other promotional, advertising, educational or communication materials or other materials relating to or referring to the Product. With respect to the Detailing of the REQUIP™ Products, XenoPort Sales Representatives will utilize only the Promotional Materials relating to the REQUIP™ Products provided to them by GSK, and will not utilize any other promotional, advertising, educational or communication materials or other materials relating to or referring to the REQUIP™ Products. XenoPort Sales Representatives will conduct only those promotional and other sales activities relating: (i) to the Product that have been approved in advance in accordance with the Co-Promotion Plan; and (ii) to the REQUIP™ Products that have been approved in advance in accordance with the REQUIP™ Sales Plan. XenoPort Sales Representatives shall not modify, change or alter the Promotional Materials provided by GSK in any way whatsoever, without the express prior written consent of GSK. XenoPort Sales Representatives shall use such Promotional Materials solely for the purpose of performing their obligations under this Agreement.

     5.7 Reports and Audit Rights .

     (a) XenoPort will keep accurate records in sufficient detail of the XenoPort’s Sales Representatives’ Detailing activities relating to the Product and/or the REQUIP™ Products to determine the amounts owed by GSK to XenoPort hereunder. XenoPort shall keep such records regarding such Sales Representatives’ Detailing activities during the period during which XenoPort is Co-Promoting the Product and/or the REQUIP™ Products, as applicable, and for a period of [... * ...]

     (b) During normal business hours and with not less than [... * ...] advance written notice to XenoPort, XenoPort will permit GSK or its authorized representatives to (i) have

access to the records of XenoPort Sales Representative Detailing activities maintained by XenoPort for purposes of verifying the accuracy of the invoices presented by XenoPort hereunder, and (ii) audit such records; provided, however that [... * ...] . Any and all audits undertaken by GSK pursuant