Co-development And Commercialization Agreement, Dated As of December 9, 2005

Exhibit 10.23

Certain information in this document, marked by brackets, has been omitted and filed separately with the Securities and Exchange Commission. Confidential treatment has been requested with respect to the omitted portions.

CO-DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

This Co-Development and Commercialization Agreement (the " Agreement" ) is entered into as of December 9, 2005, by and between Hoffmann-La Roche Inc., a corporation organized and existing under the laws of the State of New Jersey, with its principal place of business at 340 Kingsland Street, Nutley, New Jersey 07110 (" Roche Nutley" ), and F. Hoffmann-La Roche Ltd, a Swiss Corporation, with its principal place of business at Grenzacherstrasse 124, CH-4070 Basel, Switzerland (" Roche Basel" ), (Roche Nutley and Roche Basel are collectively referred to as " Roche" ) and Maxygen Holdings Ltd., a company organized under the laws of Cayman Islands, British West Indies (" Maxygen" ). Roche and Maxygen are each referred to herein individually as a " Party," and collectively as the " Parties."

BACKGROUND

A. Maxygen owns or possesses certain Patent Rights (as defined below) and Know-How (as defined below) with respect to certain novel human Factor VII variants, and believes that the Factor VII variants have the potential to be used therapeutically for the treatment of bleeding disorders;

B. Maxygen desires to collaborate with a pharmaceutical company with development and commercialization expertise with regard to drugs useful for the Field (as defined below), so as to realize promptly, the therapeutic and commercial potential of the Factor VII variants, and Roche desires to collaborate with Maxygen in the development and commercialization of Factor VII variants for multiple indications in the Field, and further desires to make the commitment and investment to develop diligently and commercialize Products (as defined herein) worldwide;

C. Roche and Maxygen envision that the scope of this Agreement will include the invention and discovery of Factor VII variants, and means for making, formulating, and using such compounds; and

D. The Parties have agreed that Maxygen shall have certain rights to develop and commercialize certain of its Factor VII variants (other than Licensed Compounds and corresponding Products subject to this Agreement) for use outside the Field, itself or with a Third Party.

NOW THEREFORE, in consideration of the foregoing and of the mutual covenants hereinafter set forth and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the Parties hereby agree as follows: 1. DEFINITIONS

As used in this Agreement, the following capitalized terms shall have the following meanings, and singular forms, plural forms and derivative forms thereof shall be interpreted accordingly:

1.1 " Accounting Standards" means generally accepted accounting principles applicable internationally and/or in a particular country (e.g., International Accounting Standards, U.S. GAAP), as consistently applied by or on behalf of the relevant Party.

1.2 " Adjusted Gross Sales" means, on a Product-by-Product basis, the amount of gross sales of applicable Product invoiced by the Roche Group to independent Third Parties, less the following deductions: returns [****]; in each case, only to the extent such deductions are applied in accordance with applicable Accounting Standards, are actually incurred, are included in the amount of gross sales invoiced and separately identified on the invoice or other documentation maintained in the ordinary course of business and are not otherwise recovered by or reimbursed to the Roche Group. Notwithstanding the foregoing, amounts received by the Roche Group for the sale of Products among members of the Roche Group for resale shall not be included in the computation of Adjusted Gross Sales; provided, however, that if and when such Product is resold to Third Parties, amounts for any such sales shall be included in Adjusted Gross Sales. A " sale" shall include any transfer or other disposition for consideration, and Adjusted Gross Sales shall include the fair market value of all consideration received by the Roche Group in respect of any sale of a Product, whether such consideration is in cash payment, in kind, exchange for value or another form. Roche will use [****] to reconcile amounts included and/or deducted in Adjusted Gross Sales for a particular Product on [****] basis and credit or debit Adjusted Gross Sales accordingly.

If a member of the Roche Group provides services to a Third Party in connection with the sale or use of a Product (except where such Product is provided without consideration pursuant to Section 9.5), then Adjusted Gross Sales shall also include the fair market value of such Product and services, subject to the following paragraph. In the case of discounts on " bundles" of products and services that include Products, Roche may discount the bona fide list price of a Product by no more than the average percentage discount of all products of the Roche Group in a particular " bundle," calculated as follows:

Average percentage discount on a particular " bundle" = [1-(A/B)] x 100

where A equals the total discounted price of a particular " bundle" of products, and B equals the sum of the undiscounted bona fide list prices of each unit of every product in such " bundle" . Roche shall retain (and in the course of any audit subject to Section 9.5 provide to Maxygen) documentation, establishing such average discount with respect to each " bundle" . If Roche cannot so establish the average discount of a " bundle" , Adjusted Gross Sales shall be based on the undiscounted list price of the Product in the " bundle" . If a Product in a " bundle" is not sold separately, and no bona fide list price exists for such Product, then the Parties shall negotiate in good faith an imputed list price for such Product and Adjusted Gross Sales with respect thereto shall be based on such imputed list price.

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1.3 " Adverse Safety/Tox Results" means, with respect to a particular Product, either (i) results showing the failure of such Product to meet GLP safety and toxicity studies that are required by the FDA/EMEA prior to introduction of such a biological compound into humans, or (ii) results that provide a reasonable basis for the discontinuance by Roche of all further development or commercialization of such Product for use in the Field because the risk profile of such Product makes it unlikely that Regulatory Approval can be obtained or maintained for such Product in the Major Markets.

1.4 " Affiliate" means any corporation or other business entity that controls, is controlled by, or is under common control with a Party. A corporation or other entity shall be regarded as in control of another corporation or entity if it owns or directly or indirectly controls at least fifty percent (50%) of the outstanding shares or other voting rights of the other corporation or entity having the right to elect directors (other than Genentech, Inc. and Chugai Pharmaceutical Company Ltd, neither of which shall be a Roche Affiliate nor be entitled to the rights of a Roche Affiliate under this Agreement unless Roche in its sole discretion opts for one or both of them to be a Roche Affiliate, and Codexis, Inc., which shall not be a Maxygen Affiliate or entitled to the rights of a Maxygen Affiliate under this Agreement) or such lesser percentage that is the maximum permitted to be owned by a foreign entity in those jurisdictions where majority ownership by foreign entities is prohibited, or (a) in the absence of the ownership of at least fifty percent (50%) of the outstanding shares or other voting rights of a corporation, or (b) in the case of a non-corporate business entity, if it possesses, directly or indirectly, the power to direct or cause the direction of the management and policies of the corporation or non-corporate business entity, as applicable, whether through the ownership or control of voting securities, by contract or otherwise.

1.5 " Animal [****] Result" means with respect to a Product: (a) results showing [****] as described on Exhibit F of the Program Plan and Budget, [****] in (i) a [****] model, or (ii) [****] model, or (iii) another animal model [****] approved by [****]; or (b) a [****] decision by [****] to file an IND.

1.6 " Backup Compound" means an E Compound that Roche has designated as such pursuant to Section 3.5.1, and any replacement thereof selected by Roche. 1.7 " BLA" means a Biological License Application, as defined in the U.S. Public Health Service Act and the regulations promulgated thereunder, or any corresponding foreign application, registration or certification, filed with a Regulatory Agency with respect to a Product, or any corresponding foreign application, registration or certification. 1.8 " Budgeted Costs" means the costs and expenses budgeted and approved by the JMC, from time to time, for the conduct of the activities in the R&D Program and/or Product commercialization, which costs and expenses are expressly included in the Program Plan and Budget.

1.9 " CMC Costs" has the meaning set forth on Exhibit A .

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1.10 " Collaboration Costs" means (a) R&D Costs worldwide, and (b) M&P Costs allocated to the U.S. by the Finance Team, in each case, actually incurred and/or accrued in accordance with applicable Accounting Standards and guidelines established by the Finance Team, in connection with the conduct of R&D Program activities pursuant to the Program Plan and Budget.

1.11 " Commencement" means, with respect to a clinical trial, the date upon which the first human subject receives the first dose of the Product that is the subject of such clinical trial.

1.12 " Commercial Manufacturing Costs" has the meaning set forth on Exhibit A .

1.13 " Commercially Reasonable Efforts" means the level of efforts and resources reasonably appropriate to diligently develop and/or commercialize (as applicable) a Licensed Compound or Product in a sustained manner, consistent with the efforts and resources a similarly situated biopharmaceutical company would typically devote to a product of similar market potential, profit potential, and/or proprietary protection, based on market conditions then prevailing. 1.14 " [****] Process Result" means (i) results demonstrating in [****] a) the ability to grow cells expressing an E Compound in [****] cultures for [****] and maintain an [****], and b) the ability to reach the [****] followed by at least [****] of an E compound in a bioreactor working volume of at least [****], and (c) [****], and (d) the ability to purify an E compound with at least a [****] final recovery yield per [****] campaign as compared to the recovery yield described in " Satisfactory [****] Culture Results" with a consistent Product quality in terms of [****], and (e) complete written documentation through Standard Operating Procedures for the [****] process; or (ii) a decision by [****] to utilize a [****] process to manufacture a Product for Phase III clinical trials and commercial use. 1.15 " Completion of Phase IIa" means for a particular Initial Indication, the date immediately after the completion of the Phase IIa clinical trial program for such Initial Indication (i.e., when the clinical database is locked for such trial). As used in this Agreement, Phase IIa clinical trial means the initial Phase II clinical trial designed to demonstrate proof of concept for a Product, and may be included within a single Phase II clinical trial if no separate Phase IIb clinical trial is needed for the applicable indication.

1.16 " Compound" shall mean [****] that was made, conceived, reduced to practice or otherwise developed (a) by Maxygen on or before the Effective Date, or (b) by Maxygen or Roche or jointly by the Parties in connection with the R&D Program.

1.17 " Confidential Information" means any proprietary or confidential information disclosed by one Party to the other hereunder that (a) is in written or graphic form and marked as " Confidential" at the time it is delivered to the receiving Party, (b) is disclosed orally hereunder that is identified as confidential or proprietary when disclosed or within thirty (30) days thereafter, or (c) the proprietary or confidential nature of which would be reasonably apparent to the recipient in view of the context and/or circumstances of disclosure.

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1.18 " Control" or " Controlled" means the possession by a Party of the ability to grant a license or sublicense as provided for herein without violating the terms of any agreement or other arrangement with any Third Party that exists at the time such Party would be granting to the other Party such license or sublicense.

1.19 " Data Package" means, in respect to any Product, all (a) Regulatory Filings, (b) databases containing clinical and/or safety data relating to such Product, including, the master database, and all data in such databases, (c) pre-clinical data, including any CMC data, and/or data from any clinical trial, whether or not contained in any IND, (d) records of any and all communications with any Regulatory Agency, and (e) information relating to any adverse events whether or not reported to any Regulatory Agency. 1.20 " Derivative" means any E Compound that is [****].

1.21 " [****] Therapeutic [****] Result" means (i) results with an E Compound proving [****] in agreed animal model(s) (a) described in Exhibit E of the Program Plan and Budget, or (b) otherwise [****] agreed by [****], or (ii) a decision [****] to commence GLP toxicology studies with a Product.

1.22 " Distribution Costs" has the meaning set forth on Exhibit A .

1.23 " Dollars" or " $" means U.S. dollars.

1.24 " E Compound" means (a) any Compound that Tests Positively, and (b) any Derivative.

1.25 " Effective Date" means the later of (a) the date in the caption to this Agreement, or (b) if an HSR filing is made, the second business day immediately following the earlier of: (i) the date upon which the waiting period under the Hart Scott Rodino Antitrust Improvement Act (" HSR" ) expires or terminates early or (ii) the date upon which all requests to the Parties by the Federal Trade Commission or the Justice Department, as the case may be, with regard to the transaction contemplated by this Agreement have been satisfactorily met and no objection on the part of the Federal Trade Commission or the Justice Department remain.

1.26 " EMEA" means the European Medicines Agency, and any successor agency(ies) thereto.

1.27 " [****] Decision Point" means with respect to a decision by Maxygen to opt-out of further sharing of Collaboration Costs, the date that Maxygen gives Roche notice of such decision, which date is at least [****] before the [****], which meeting date was previously disclosed by Roche to Maxygen pursuant to Section 4.7.3.

1.28 " Entry into Humans" or " EIH" means with regard to a particular Product, the date of dosing of the first human subject in the first clinical trial of the applicable Product.

1.29 " Exit Costs" means the Collaboration Costs that will be shared by the Parties following either (a) an opt-out by Maxygen pursuant to Section 4.7, or (b) a termination by

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Roche pursuant to Section 18.4 for (i) then-ongoing clinical activities conducted pursuant to the most recent agreed update of the Program Plan and Budget, and (ii) non-cancelable obligations for other activities ongoing as of the date of opt-out or notice of termination, as applicable, conducted pursuant to the most recent update of the Program Plan and Budget [****]. Exit Costs shall not include any amounts for (x) [****], (y) cancelable obligations of other on-going activities being conducted pursuant to the most recent update of the Program Plan and Budget (except [****], or (z) any other activities [****] notice by the Party receiving such notice.

1.30 " FDA" means the U.S. Food and Drug Administration and any successor entity thereto.

1.31 " Field" means the [****]. By way of illustration, but without limitation, the Field includes: [****]. 1.32 " Finance Team" means the committee described in Section 2.5. 1.33 " First Commercial Sale" means the first sale of a Product to a Third Party following the receipt of any Regulatory Approval required for the sale of such Product.

1.34 " FTE" means a full-time equivalent person-year of effort undertaken in connection with the conduct of the R&D Program.

1.35 " Hemophilia" means hemophilia A, hemophilia B, acquired hemophilia, genetic Factor VII deficiency and Glanzman thombasthenia.

1.36 " ICH" means intracerebral hemorrhage.

1.37 " IND" means an Investigational New Drug application, as defined in the U.S. Food, Drug and Cosmetic Act and the regulations promulgated thereunder, including all subsequent filings in support of the initial filing(s), or any corresponding foreign application, registration or certification (e.g., a CTA). 1.38 " Indication" means any human bleeding disorder or injury in the Field. 1.39 " Initial Indication" means each of trauma and ICH, unless otherwise agreed to by the Parties pursuant to Section 3.1.2 (c).

1.40 " Initial Period" means the period from the Effective Date until the earlier of: (a) [****], or (b) the date [****] after the Effective Date, provided, however, if the [****] Culture Result with [****] is not achieved on or before [****], and as a result, [****], such [****] period shall be extended by a period equal to the time between [****] and the date that a [****] Culture Result is achieved, provided, further, if any E Compound other than [****] is selected as the Lead Compound, the foregoing [****] period shall be [****] and [****]. 1.41 " Invention(s)" means any and all useful ideas, concepts, methods, procedures, processes, improvements, inventions, discoveries, and reductions to practice, whether or not patentable, which arise from or are first made, conceived or first reduced to practice in the course of the joint or separate activities of the Parties conducted in connection with the R&D Program

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1.42 " Joint Management Committee" or " JMC" means the committee described in Section 2.2.

1.43 " Joint Program Team" or " JPT" means the committee described in Section 2.3.

1.44 " Know-How" means all non-patented data, information, methods, procedures, processes, materials (including any Material) and other know-how. Know-How includes but is not limited to: biological, chemical, biochemical, toxicological, pharmacological, metabolic, formulation, clinical, analytical and stability information and data (other than such information and data that is or becomes the subject of a patent or patent application). Know-How does not include any inventions otherwise included in the Patent Rights.

1.45 " Lead Compound" means the E Compound that is selected as such by [****] pursuant to Section 3.5.1, and any replacement thereof selected by [****]. 1.46 " Legal Requirement" means any present and future multinational, national, state, local or similar laws (whether under statute, rule, regulation or otherwise); requirements under permits, orders, decrees, judgments or directives, and requirements of applicable Regulatory Agencies (including, without limitation, current Good Manufacturing Practices, Good Laboratory Practices, Good Clinical Practices); and regulations pertaining to Investigational New Drug Applications (as amended or revised from time to time).

1.47 " Licensed Compound" means any E Compound that is then a Lead Compound or a Backup Compound.

1.48 " Major Country" means each of the United Kingdom, France, Germany, Italy or Spain.

1.49 " Major Markets" means all Major Countries, the U.S., Canada, Australia and Japan.

1.50 " Marketing and Promotion Costs" or " M&P Costs" has the meaning set forth on Exhibit A .

1.51 " Materials" means any chemical or biological substances including any: (a) organic or inorganic chemical or compound; (b) gene; (c) vector or construct, whether plasmid, phage, virus or any other type; (d) host organism, including bacteria and eukaryotic cells; (e) eukaryotic or prokaryotic cells, cell line or expression system; (f) protein, including any peptide or amino acid sequence, enzyme, antibody or protein conferring targeting properties and any fragment of a protein or peptide or enzyme; (g) genetic material, including any genetic control element (e.g., promoters); (h) virus; or (i) assay or reagent.

1.51.1 " Roche Materials" means any Materials provided by Roche to Maxygen pursuant to this Agreement other than those that are Maxygen Materials.

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1.51.2 " Maxygen Materials" means any Materials provided by Maxygen to Roche pursuant to this Agreement. It is understood and agreed that all Compounds shall be Maxygen Materials.

1.51.3 " Program Materials" means all Materials that are first developed or made or discovered during and in connection with the R&D Program.

1.52 " Maxygen Compound" shall mean E Compounds that Maxygen has selected to develop and/or commercialize for Hemophilia as described in Section 6.3.

1.53 " Maxygen Technology" means the Maxygen Separate Technology and Maxygen' s ownership interest in the Program Technology. 1.54 " Net Sales" means with respect to a particular Product, the amount calculated by subtracting from the amount of Adjusted Gross Sales a [****] deduction of [****] percent [****] of Adjusted Gross Sales for sales in the U.S., and [****] percent [****] of Adjusted Gross Sales for sales outside the U.S. in lieu of sales-related deductions not specifically provided for in the definition of Adjusted Gross Sales (e.g., [****])). For clarity, such deductions shall not be used in the calculation of Adjusted Gross Sales nor shall any amount for any such deductions be included in Distribution Costs, Commercialization Costs or any other category of Collaboration Costs.

1.55 " Patent Rights" means U.S. and foreign patent applications (including, without limitation, all continuations, continuations-in-part, substitutions and divisions thereof) and patents (including all reissues, renewals, extensions, confirmations, re-registrations, re-examinations, revalidations and patents of addition, supplementary protection certificates, or other governmental actions that extend the term of any of the patents).

1.56 " Phase I" means the first phase of human clinical trials using a limited number of human subjects to gain evidence of the safety and tolerability of a Product and information regarding pharmacokinetics and potential pharmacological activity for such Product, which human clinical trials are usually completed prior to the initiation of Phase II, as described with respect to the U.S. in 21 C.F.R. a7312.21(a), as may be amended, and, with respect to any other country or jurisdiction, the equivalent of such a clinical trial in such other country or jurisdiction.

1.57 " Phase II" means the second phase of human clinical trials of a Product in human subjects to gain evidence of the efficacy in one or more indications and expanded evidence of the safety of such Product, as well as an indication of the dosage regimen required, as described with respect to the U.S. in 21 C.F.R. a7312.21(b), as may be amended, and, with respect to any other country or jurisdiction, the equivalent of such a clinical trial in such other country or jurisdiction. A Phase I/II clinical trial shall be considered a Phase II trial.

1.58 " Phase III" means the third phase of human clinical trials of a Product, which are large-scale trials to gain evidence of the efficacy and safety in a number of human subjects sufficient to support registration for such Product, as described with respect to the U.S. in 21 C.F.R. a7312.21(c), as may be amended, and, with respect to any other country or jurisdiction, the equivalent of such a clinical trial in such other country or jurisdiction. A Phase II/III clinical trial shall be considered a Phase III trial.

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1.59 " Phase IV" means the phase of human clinical trials of a Product conducted after such Product receives Regulatory Approval for commercial sale and is marketed to (a) delineate additional information regarding the use of such Product for a particular indication to confirm safety in human subjects for such indication or to support marketing of such Product, as described with respect to the U.S. in 21 C.F.R. a7312.85, as may be amended, and, with respect to any other country or jurisdiction, the equivalent of such a clinical trial in such other country or jurisdiction, or (b) otherwise to support sales of such Product.

1.60 " [****] Decision Point" means with respect to a decision by Maxygen to opt-out of further sharing of Collaboration Costs, the date that Maxygen gives Roche notice of such decision, which date is at least [****].

1.61 " [****] Decision Point" means with respect to a decision by Maxygen to opt-out of further sharing of Collaboration Costs, the date that Maxygen gives Roche notice of such decision, which date is at least [****] before the [****], which [****] was previously disclosed by [****] pursuant to Section 4.7.3.

1.62 " Product" means a pharmaceutical composition intended for use in the Field (in any dosage form and/or formulation) containing one or more Licensed Compounds as an active ingredient. Products containing one or more different Licensed Compounds shall be considered as different Products.

1.63 " Product Commercialization Team" or " PCT" means the committee described in Section 2.4.

1.64 " Product Liaison Team" or " PLT" means the committee established pursuant to Section 2.7.

1.65 " Program Plan and Budget" means the overall plan and budget described in Section 3.3 governing the collaborative research and development of Products and commercialization of Products for the Initial Indications, as may be amended from time to time by the JMC. 1.66 " Program Technology" means Know-How and Patent Rights, in each case, that are (a) made or conceived or reduced to practice or otherwise developed by Maxygen or Roche or jointly by Maxygen and Roche or their respective Affiliates, in each case, in connection with the R&D Program or other activities subject to this Agreement, and (b) necessary or useful for the manufacture, use or commercialization of any Product. Notwithstanding the foregoing, Program Technology shall not include any Shuffling Technology.

1.67 " R&D Costs" shall have the meaning set forth in Exhibit A hereto.

1.68 " R&D Program" means the activities undertaken by the Parties pursuant to the Program Plan and Budget to develop at least one Product for the Initial Indications, in each case, through BLA Approval for the applicable Product, and such other activities with regard to Compounds and Products as the Parties may agree in writing.

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1.69 " R&D Program Term" shall have the meaning set forth in Section 3.4

1.70 " Regulatory Agency" means, with respect to any particular country or, where applicable, a multinational jurisdiction, the governmental authori ...