Exhibit 10.6





MAXYGEN, INC.


2000 INTERNATIONAL STOCK OPTION PLAN


(amended as of March 1, 2001)





1.    PURPOSES OF THE PLAN





The purposes of the Maxygen 2000 International Stock Option Plan (the Plan) of Maxygen, Inc., a Delaware corporation (the
Company), are:





(a)    to encourage selected employees, directors and
consultants of the Companys non-U.S. direct and indirect subsidiaries to improve operations and increase revenues and profits of such subsidiaries and the Company;





(b)    to encourage such employees, directors and consultants to accept or continue employment or association with such subsidiaries; and





(c)    to increase the interest of such employees, directors and consultants in the
welfare of such subsidiaries and the Company through participation in the growth in value of the Companys common stock (the Common Stock).





Options granted under this Plan (Options) are not intended to be incentive stock options under the United States Internal Revenue Code (the Code).





2.    ELIGIBLE PERSONS





(a)    Every
person who at the date of grant of an Option is an employee of, consultant to, or director of, a Subsidiary (as defined below) that is organized under the laws of a jurisdiction outside the United States is eligible to receive Options.
Subsidiary means an entity of which the Company directly or indirectly owns at least 50% of the ordinary voting power. An employee includes an officer or director who is an employee of a Subsidiary. A consultant
includes persons employed by, or otherwise affiliated with, a consultant to a Subsidiary.





(b)    Options
may not be granted to consultants who are not natural persons unless the Company determines both (i) that such grant (A) shall be registered in a manner other than on a Form S-8 Registration Statement under the Securities Act (e.g., on a Form S-3
Registration Statement) or (B) does not require registration under the Securities Act in order to comply with the requirements of the Securities Act, if applicable and (ii) that such grant complies with the securities laws of all other relevant
jurisdictions.





3.    SHARES SUBJECT TO THIS PLAN





Subject to Section 6.1 of this Plan, the total number of shares of Common Stock that may be issued under Options shall be 1,000,000 shares, plus an annual increase to be added on the
first day of the Companys fiscal year beginning in fiscal year 2002, equal to 0.6% of the outstanding shares of capital stock on such date, or such lower number as shall be set by the Board of Directors of the Company (the Board).
The shares covered by the portion of any Option that expires or is terminated unexercised shall again become available for grants of Options.





4.    ADMINISTRATION





4.1    General.    This Plan shall be administered by the Board or by a committee of at least two Board members (the Committee) to which administration of the Plan, or
of part of the Plan, is delegated (in either case, the Administrator). Any Committee shall consist of Board members who are non-employee directors as defined in Rule 16b-3 adopted by the United States Securities and Exchange
Commission or any successor rule thereto (Rule 16b-3). To the extent that the Administrator determines it to be desirable to qualify Options




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granted hereunder as performance-based compensation within the meaning of Section 162(m) of the Code, the Plan shall be administered by a Committee of two or more outside
directors within the meaning of Section 162(m) of the Code. If administration is delegated to a Committee, the Committee shall have, in connection with the administration of the Plan, the powers theretofore possessed by the Board (and
references in this Plan to the Board shall thereafter be to the Committee), subject, however, to such resolutions not inconsistent with the provisions of the Plan, as may be adopted from time to time by the Board. The Board may abolish the Committee
at any time and revest in the Board the administration of the Plan.





4.2    Authority of
Administrator.    Subject to the other provisions of this Plan, the Administrator shall have the authority, in its sole discretion: (i) to grant Options; (ii) to determine the fair market value of the Common Stock subject
to Options; (iii) to determine the exercise price of Options granted; (iv) to determine the persons to whom, and the time or times at which, Options shall be granted, and the number of shares subject to each Option; (v) to interpret this Plan; (vi)
to prescribe, amend, and rescind rules and regulations relating to this Plan and to Options; (vii) to determine the terms and provisions of each Option granted (which need not be identical), including but not limited to, the time or times at which
Options shall be exercisable and any vesting criteria; (viii) with the consent of the optionee with respect to any adverse amendment, to modify or amend any outstanding Option; (ix) to accelerate the exercise date or vesting of any Option; (x)
to authorize any person to execute on behalf of the Company any instrument evidencing the grant of an Option; and (xi) to make all other determinations that the Administrator considers necessary or advisable for the administration of this Plan. The
Administrator may delegate non-discretionary administrative duties to such employees of the Company or its Subsidiaries as it deems proper.





4.3    Interpretation by Administrator.    All questions of interpretation, implementation, and application of this Plan and the Options shall be determined
by the Administrator in its absolute discretion. Such determinations shall be final and binding on all persons.





4.4    Rule 16b-3    With respect to persons subject to Section 16 of the United States Securities Exchange Act of 1934, as amended (the Exchange Act) who receive
Options, if any, transactions under this Plan are intended to comply with the applicable conditions of Rule 16b-3. To the extent a transaction under this Plan or an action by the Administrator fails to so comply, it shall, to the extent deemed
advisable by the Administrator, be modified to comply with Rule 16b-3. However, it shall be the responsibility of such persons, not of the Company, any Subsidiary or the Administrator, to comply with the requirements of Section 16 of the Exchange
Act. The Company, its Subsidiaries and the Administrator shall not be liable if this Plan or any transaction under this Plan fails to comply with the applicable conditions of Rule 16b-3 or if any such person incurs any liability under Section 16 of
the Exchange Act.





5.    GRANTING OF OPTIONS; OPTION AGREEMENT





5.1    Period of Grants.    No Options shall be granted under this Plan after ten years from the date of adoption of this
Plan by the Board.





5.2    Option Agreements.    Each Option shall
be evidenced by a stock option agreement (the Option Agreement), in form satisfactory to the Company, which may include an electronic form of agreement, executed or electronically accepted by the Company and the person to whom the Option
is granted. However, the failure by the Company or the optionee to execute or accept an Option Agreement shall not invalidate the grant of an Option. The vesting of the Option shall nevertheless be subject to Section 6.3.





5.3    Anticipatory Grants.    The Administrator may approve the grant of Options to
persons who are expected to become employees, directors or consultants of any Subsidiary, but are not yet employees, directors or consultants at the date of approval.




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6.    TERMS AND CONDITIONS OF OPTIONS





Each Option shall be subject to the following terms and conditions:





6.1    Changes in Capital.    Subject to Section 6.2, if the Common Stock is changed by reason of a stock split, reverse stock split, stock dividend, recapitalization, conversion,
combination or reclassification, appropriate adjustments shall be made by the Administrator in its sole discretion in (a) the number and class of securities subject to this Plan and each Option outstanding and (b) the per security exercise
price of each outstanding Option. However, the Company shall not be required to issue fractional securities as a result of any such adjustment.





6.2    Corporate Transactions.    In the event of the proposed dissolution or liquidation of the Company, the Administrator shall notify each optionee at
least 15 days before consummation of the proposed action. To the extent not previously exercised, all Options will terminate immediately before the consummation of the proposed action. In the event of a merger or consolidation of the Company with or
into another entity in which the Company is not a surviving entity or in which the stockholders of the Company just before that transaction do not, by virtue of those holdings, own securities representing at least 50 percent of the ordinary voting
power of the Company immediately after that transaction, or in the event of a sale of all or substantially all of the assets of the Company in which the stockholders of the Company receive securities of the acquiring entity or an affiliate thereof:
(a) if the successor entity so chooses, it shall assume the Options or issue equivalent options when the transaction is consummated or (b) if the successor entity chooses not to do that, then the Options shall be fully vested and exercisable for a
period of 15 days after the date notice is given under this Section 6.2 and shall terminate upon expiration of that 15-day period.





6.3    Vesting and Exercise.    Subject to Section 5, Options shall vest in accordance with a schedule related to the date of the grant of the Option, the date of first employment
or such other date as may be set by the Administrator and specified in the Option Agreement relating to the Option. The vesting schedule may be tied to the mere passage of time, continued employment or association with a Subsidiary, performance
objectives, or any other elements or criteria or combination of elements or criteria that the Administrator specifies. Nothing in this Plan shall preclude the grant of Options that are fully vested at the time of grant. No Option shall be
exercisable until an Option Agreement in form satisfactory to the Company is executed or electronically accepted by the Company and the optionee. Unless otherwise set forth in the applicable Option Agreement or as accelerated by the Board or
pursuant to this Plan, Options will become exercisable upon vesting.





6.4    Option Grant
Date.    Except in the case of advance approvals described in Section 5.3, the date of grant of an Option shall be the date as of which the Administrator approves the grant. In the case of advance approvals, the date of
grant shall be the date upon which the person becomes, as applicable, an employee, director or consultant of the Subsidiary.





6.5    Non-Assignability of Option Rights.    Except as otherwise determined by the Administrator and expressly set forth in the Option Agreement, no Option shall be assignable or
otherwise transferable by the optionee except by will or by the laws of descent and distribution. During the life of the optionee, except as otherwise determined by the Administrator and expressly set forth in the Option Agreement, an Option shall
be exercisable only by the optionee. Notwithstanding the foregoing, the optionee may, by delivering written notice to the Company, in a form satisfactory to the Company, designate a third party who, in the event of the death of the optionee, shall
thereafter be entitled to exercise the Option.





6.6    Payment.    Except as provided in the applicable Option Agreement, payment in full, in cash in United States dollars or what the Administrator determines is the then
equivalent in a non-U.S. currency that is the currency in which the Optionee is regularly paid, shall be made for all stock purchased at the time written notice of exercise of an Option is given to the Company. The proceeds of any payment shall
constitute general funds of the Company. At the time an Option is granted or exercised, the Administrator, in the exercise of its absolute




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discretion after considering any legal, tax or accounting consequences to the Company and its Subsidiaries, may authorize any one or more additional methods of payment that are permitted by
applicable law.





6.7Termination of Employment.





(a)    If, for any reason other than death, disability or cause (as defined below), an optionee is no
longer employed by the Company or any of its Subsidiaries (such event being called a Termination), Options held by that optionee at the date of Termination (to the extent then vested) may be exercised in whole or in part at any time
within 90 days after the date of the Termination, or such other period of not less than 30 days after the date of the Termination as is specified in the Option Agreement (but in no event after the Expiration Date) (the Post-Termination
Exercise Period). The Board may at any time extend the Post-Termination Exercise Period and provide for continued vesting during such extended period. If, at the date of termination, the optionee is not entitled to exercise his or her entire
Option, the shares covered by the unexercisable portion of the Option shall revert to and again become available for issuance under the Plan. If, after termination, the optionee does not exercise his or her Option within the time specified in the
Option Agreement or as otherwise determined above, the Option shall terminate, and the shares covered by such Option shall revert to and again become available for issuance under the Plan. Notwithstanding the foregoing, the Board shall have the
power to permit an Option to vest, in whole or in part, during the Post-Termination Exercise Period.





(b)    If an optionee dies or becomes disabled (as determined in good faith by the Administrator) while employed by the Company or a Subsidiary or within the period that the Option remains exercisable after Termination,
Options then held (to the extent then vested) may be exercised, in whole or in part, by the optionee, by the optionees personal representative or by the person to whom the Option is transferred by devise or the laws of descent and
distribution, at any time within 12 months after the death or 12 months after the disability of the optionee, or such other period of not less than six months from the date of death or disability as is specified in the Option Agreement (but in no
event after the Expiration Date). If, at the date of death or disability, the optionee is not entitled to exercise his or her entire Option, the shares covered by the unexercisable portion of the Option shall revert to and again become available for
issuance under the Plan. If, after death or disability, the Optionee does not exercise his or her Option within the time specified in the Option Agreement or as otherwise determined above, the Option shall terminate, and the shares covered by such
Option shall revert to and again become available for issuance under the Plan.





(c)    If
an optionee is terminated for cause, all Options then held shall terminate and no longer be exercisable at the time of Termination. All the shares covered by such Options shall revert to and again become available for issuance under the
Plan.





(d)    For purposes of this Section 6.7, employment includes service as
a director or as a consultant. If the optionee is an employee of a consultant, then that optionees employment shall be considered to have terminated on the earlier to occur of that optionees ceasing to work for the consultant
or the consultant ceasing to work for the Subsidiary.





(e)    For purposes of this Section
6.7, an optionees employment shall not be deemed to terminate by reason of sick leave, military leave or other leave of absence approved by the Administrator, if the period of any such leave does not exceed 90 days or, if longer, if the
optionees right to reemployment by the Company or any Affiliate is guaranteed by contract or statute.





(f)    For purposes of this Section 6.7, cause means Termination: (i) by reason of an optionees commission of a felony, misdemeanor or other conduct that is illegal in the jurisdiction in which the
conduct occurs, in each such case involving dishonesty, fraud or moral turpitude, (ii) by reason of an optionees dishonesty towards, fraud upon, or deliberate injury or attempted injury to the Company or any of its Subsidiaries, (iii) by
reason of an optionees willfully engaging in misconduct that is materially and demonstrably injurious to the Company or any of its Subsidiaries or (iv) by reason of an optionees breach of any agreement between the optionee, on one hand,
and the Company or a Subsidiary, on the other hand.




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6.8    Repurchase of Stock.    At
the election of the Administrator, the stock to be delivered upon exercise of any Option may be subject to a right of repurchase in favor of the Company or its assignee with respect to any employee, director or consultant whose employment, or
director or consulting relationship with any Subsidiary or the Company is terminated. Such right of repurchase shall be exercisable at the time, under the circumstances and at the price that the Administrator determines, as specified in the option
agreement signed by the optionee and the Administrator when the Option is granted. In addition to the repurchase right described above, the shares purchased under an Option may be subject to additional or greater restrictions as specified in the
Option Agreement, at the absolute discretion of the Administrator.





6.9    Withholding and
Employment Taxes.    At the time of exercise of an Option or at such other time as the amount of such obligations becomes determinable (the Tax Date), the optionee shall remit to the Company in cash any
applicable withholding, employment and other taxes or payments that may become payable to or by the Company or any Subsidiary in connection with that exercise. If authorized by the Administrator in its absolute discretion, after considering any tax
or accounting consequences to the Company and its Subsidiaries, an optionee may elect to: (i) tender to the Company previously owned shares of Common Stock or other securities of the Company, (ii) have shares of Common Stock that are acquired upon
exercise of the Option withheld by the Company to pay some or all of the amount of tax up to, for shares acquired upon exercise of the Option, the minimum withholding required by law and in no event any more, and for tendered shares, the amount of
tax and other payments required to be withheld or paid by the Company or any Subsidiary as a result of the exercise of the Option or (iii) make payment in any other manner that is permitted by applicable law. Any securities tendered or withheld in
accordance with this Section 6.9 shall be valued by the Company as of the Tax Date.





6.10    Other Provisions.    Each Option may contain such other terms, provisions and conditions, not inconsistent with this Plan, as may be determined by the Administrator.





6.11    Determination of Value.    For purposes of the Plan, the
value of Common Stock or other securities of the Company shall be determined as follows:





(a)    If the securities are listed on any established stock exchange or a national market system, including without limitation the National Market System of the National Association of Securities Dealers, Inc. Automated
Quotation System, their fair market value shall be their closing sales price or the closing bid if no sales were reported, as quoted on such system or exchange (or the largest such exchange) for the date the value is to be determined (or if there
are no sales for such date, then for the last preceding business day on which there were sales), as reported in TheWallStreet Journal or similar publication.





(b)    If the securities are regularly quoted by a recognized securities dealer but selling prices are not reported, their fair market value shall
be the mean between the high bid and low asked prices for the securities on the date the value is to be determined (or if there are no quoted prices for the date, then for the last preceding business day on which there were quoted prices).





(c)    In the absence of an established market for the securities, their fair market
value shall be determined in good faith by the Administrator, by considering such factors as the Administrator in its sole discretion deems appropriate including, for example, the recent issue price of securities of the Company, the Companys
net worth and prospective earning power, and other relevant factors, including the goodwill of the Company, the economic outlook in the Companys industry, the Companys position in the industry and its management and scientific personnel,
and the values of securities of other companies in the same or similar lines of business.





6.12    Option Term.    No Option shall be exercisable more than ten years after the date of grant, or such lesser period of time as is set forth in the Option Agreement. The end
of the maximum exercise period stated in the Option Agreement is referred to in this Plan as the Expiration Date.





6.13    Exercise Price.    The exercise price of each Option shall be not less than 85% of the fair market value (determined in accordance with Section 6.11) of the stock subject
to the Option on the date of grant.




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However, without regard to that 85% rule, in connection with the acquisition of securities or assets of another entity the Company may grant Options to employees, consultants or directors of that
entity or affiliates of that entity, to replace options or warrants they held before that acquisition exercisable for equity interests in that entity, having an exercise price that is equivalent to the exercise price of the options or warrants that
the Options replace. Equivalency for this purpose will be determined in good faith by the Administrator based on the acquisition price for that entity.





7.    MANNER OF EXERCISE





7.1    Notice.    An optionee wishing to exercise an Option or portion of an Option shall give written notice to the Company at its principal executive office, to the attention of
the officer of the Company designated by the Administrator, accompanied by payment of the exercise price as provided in Section 6.6. The date the Company receives written notice of an exercise of an Option accompanied by payment of the exercise
price will be considered the date the Option was exercised. Notwithstanding the foregoing, the Company may designate a Subsidiary or other person and one or more officers of that Subsidiary or other person to serve as the Companys agent to
perform one or more of the functions specified in this Section 7.1.





7.2    Certificates or
Notice of Ownership.    Promptly after receipt of written notice of exercise of an Option, the Company shall, without stock issue or transfer taxes to the optionee or other person entitled to exercise the Option, deliver
to the optionee or such other person a certificate or certificates for the requisite number of shares of stock or, in lieu of a certificate, electronic or paper notification of share ownership in a brokerage account. An optionee or permitted
transferee of an optionee shall not have any privileges as a stockholder with respect to any shares of stock covered by the Option until the date of issuance (as evidenced by the appropriate entry on the books of the Company or a duly authorized
transfer agent) of such shares.





8.    OTHER RELATIONSHIPS





Nothing in this Plan or any Option shall interfere with or limit in any way the right of the Company or any Subsidiary to terminate any optionees employment, consultancy or
directorship at any time.





9.    CONDITIONS TO ISSUANCE OF SHARES





Shares of Common Stock shall not be issued upon the exercise of an Option unless the exercise of the Option and the issuance and delivery of such shares complies with all relevant
provisions of law including, without limitation, all applicable securities laws.





10.    NON-EXCLUSIVITY OF THE PLAN





The adoption of this Plan shall not be construed as creating any limitations on the power of the Company or its
Subsidiaries to adopt such other incentive arrangements as it may deem desirable including, without limitation, the granting of stock options other than under this Plan.





11.    AMENDMENTS TO PLAN





The Board may at any time amend, alter,
suspend or discontinue this Plan. Without the consent of an optionee, no amendment, alteration, suspension or discontinuance may adversely affect any outstanding Options held by that optionee.





12.    EFFECTIVE DATE OF PLAN





The Plan shall become
effective upon adoption by the Board.





This Board adopted this Plan on April 10, 2000.





The Board amended this Plan on March 1, 2001.




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MAXYGEN, INC.


2000
INTERNATIONAL STOCK OPTION PLAN


STOCK OPTION AGREEMENT





This document (the Agreement) sets forth the terms of a Stock Option (the Option) granted by Maxygen, Inc., a Delaware corporation (the Company), pursuant to a Certificate of Stock
Option Grant (the Certificate) displayed at the website of AST StockPlan, Inc. The Certificate, which specifies the person to whom the Option is granted (Optionee) and other specific details of the grant, and the electronic
acceptance of the Certificate at the website of AST StockPlan, Inc., are incorporated herein by reference.





THE PARTIES AGREE AS
FOLLOWS:





1.    Grant of Option; Vesting Base Date.





1.1    Grant.    The Company hereby grants to
Optionee an opportunity to purchase shares of its Common Stock in accordance with the Companys 2000 International Stock Option Plan (the Plan) as hereinafter provided.





1.2    Vesting Base Date.    The parties hereby establish the date set forth in the Certificate as the Vesting
Base Date (as defined below).





1.3    Type of
Option.    The Option shall be a nonstatutory option for US tax purposes.





1.4.    Number of Option Shares.    The number of shares of Company Common Stock underlying the Option (the Option Shares) is as set forth in the
Certificate.





2.    Exercise Price.    The exercise
price for purchase of each share of Common Stock covered by this Option shall be the price set forth in the Certificate.





3.    Term.    Unless otherwise specified in the Certificate, this Option shall expire as provided in Section 6.7 and 6.12 of the Plan.





4.    Adjustment of Options.    The Company shall adjust the number and kind
of shares and the exercise price thereof in certain circumstances in accordance with the provisions of Section 6.1 and Section 6.2 of the Plan.





5.    Exercise of Options.





5.1    Vesting; Time of Exercise.    This Option shall vest and be exercisable according to the schedule set forth in the Certificate. Such schedule shall commence
as of the date set forth in the Certificate (the Vesting Base Date). If the Optionee reduces his or her employment commitment to the Company, such vesting schedule shall be proportionately reduced. Thus if an Optionee with an original
vesting schedule of one hundred (100) shares per month reduces his or her time commitment to the Company from one hundred percent (100%) time to eighty percent (80%) time, his or her new vesting schedule would be eighty (80) shares per month. If the
Optionee thereafter increases his or her employment commitment to the Company, such vesting schedule shall be proportionately accelerated; provided, however, that the vesting schedule shall not accelerate to a rate faster than the original
vesting schedule. Thus if the Optionee subsequently increased his or her time commitment to the Company to ninety percent (90%) time, his or her new vesting schedule would be ninety (90) shares per month.





5.2    Exercise After Termination of Status as an Employee, Director or
Consultant.    In the event of termination of Optionees continuous status as an employee, director or consultant, this Option may be exercised only in accordance with the provisions of Section 6.7 of the
Plan.





5.3    Manner of Exercise.    Optionee may
exercise this Option, or any portion of this Option, by giving written notice to the Company at its principal executive office, to the attention of the officer of the Company designated by the Plan Administrator, accompanied by payment of the
exercise price and payment of




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any applicable withholding or employment taxes. The date the Company receives written notice of an exercise hereunder accompanied by payment will be considered as the date this Option was
exercised.





5.4    Payment.    Except as otherwise
provided in the Certificate, payment of the exercise price per share is due in full upon exercise of all or any part of each installment that has accrued to Optionee. Optionee may elect, to the extent permitted by applicable statutes and
regulations, to make payment of the exercise price under one of the following alternatives: (i) payment of the exercise price per share in cash (including check) in U.S. dollars, or what the Administrator determines is the then equivalent in the
currency in which the Optionee is paid, at the time of exercise, (ii) payment pursuant to a program developed under Regulation T as promulgated by the Federal Reserve Board that, prior to the issuance of the Option Shares, results in either the
receipt of cash (or check) by the Company or the receipt of irrevocable instructions to pay the aggregate exercise price to the Company from the sales proceeds, (iii) provided that at the time of exercise the Companys Common Stock is publicly
traded and quoted regularly in the Wall Street Journal, payment by delivery of already-owned shares of Common Stock, held for the period required to avoid a charge to the Companys reported earnings, and owned free and clear of any liens,
claims, encumbrances or security interests, which Common Stock shall be valued at its fair market value on the date of exercise, or (iv) payment by a combination of the methods of payment permitted by subparagraphs 5.4(i) through 5.4(iii) above. The
proceeds of any payment shall constitute general funds of the Company.





5.5    Delivery of
Certificate/Notice of Share Ownership.    Promptly after receipt of written notice of exercise of the Option, the Company shall instruct its transfer agent to deliver to Optionee a certificate or certificates
for the requisite number of Option Shares or, in lieu thereof, paper or electronic notification of share ownership in Optionees brokerage account. The Optionee shall not have any privileges as a stockholder of the Company with respect to any
Option Shares covered by the Option until the date of issuance of the stock certificate or notice of share ownership for those Option Shares.





6.    Nonassignability of Option.    This Option is not assignable or transferable by Optionee except by will or by the laws of descent and
distribution. During the life of Optionee, the Option is exercisable only by Optionee. Any attempt to assign, pledge, transfer, hypothecate or otherwise dispose of this Option in a manner not herein permitted, and any levy of execution, attachment,
or similar process on this Option, shall be null and void.





7.    Restriction on Issuance
of Shares.





7.1    Legality of
Issuance.    The Company shall not be obligated to sell or issue any Option Shares pursuant to this Agreement if such sale or issuance, in the opinion of the Company or its counsel, might constitute a violation
by the Company of any provision of law, including without limitation the provisions of the Securities Act of 1933, as amended (the Securities Act).





7.2    Compliance with Law.    The Company shall not be obligated to take any affirmative action in order to cause the grant or exercise of
this Option or the issuance or sale of any Option Shares pursuant thereto to comply with any law.





8.    Restriction on Transfer.    Regardless of whether the sale of the Option Shares has been registered under the Securities Act or has been registered or
qualified under the securities laws of any jurisdiction, the Company may impose restrictions upon the sale, pledge or other transfer of Option Shares (including the placement of appropriate legends on stock certificates) if, in the judgment of the
Company and the Companys counsel, such restrictions are necessary or desirable in order to achieve compliance with the provisions of the Securities Act, the securities laws of any state or any other law.





9.    Stock Certificate.    Stock certificates evidencing Option Shares may
bear such restrictive legends as the Company and the Companys counsel deem necessary or advisable under applicable law or pursuant to this Agreement.




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10.    Assignment; Binding
Effect.    Subject to the limitations on assignment set forth in this Agreement, this Agreement shall be binding upon and inure to the benefit of the executors, administrators, heirs, legal representatives, and
successors of the parties hereto.





11.    Damages.    Optionee shall be liable to the Company for all costs and damages, including incidental and consequential damages, resulting from a disposition of
Option Shares that is not in conformity with the provisions of this Agreement.





12.    Governing Law.    This Agreement shall be governed by, and construed in accordance with, the laws of the State of California excluding those laws that direct
the application of the laws of another jurisdiction.





13.    Notices.    All notices and other communications under this Agreement shall be in writing or posted electronically on the AST Stockplan website. Unless and
until Optionee is notified in writing to the contrary, all notices, communications, and documents directed to the Company and related to the Agreement shall be delivered to:





Maxygen, Inc.


515 Galveston Drive


Redwood City, CA 94063


Attention: General Counsel





Unless and until the Company is notified in writing to the contrary, all notices, communications, and documents directed to Optionee and related to this Agreement shall be mailed to Optionees last known address
as shown on the Companys books or posted electronically on the AST Stockplan website. Notices and communications shall be delivered by hand, mailed by first class mail, postage prepaid, sent by reputable overnight courier or posted
electronically on the AST Stockplan website. All mailings and deliveries related to this Agreement shall be deemed received when actually received, if by hand delivery, two business days after mailing, if by mail, the next business day after being
sent by reputable overnight courier, or 30 days after the date of posting for notices posted electronically on the AST Stockplan website.





IN WITNESS WHEREOF, the parties have entered into this Stock Option Agreement as of the grant date set forth in the Certificate.





MAXYGEN, INC.





Optionee accepts and agrees to be bound by all
the terms and conditions of this Agreement and the Plan.




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