Registration Statement

EXHIBIT 4.1

SUPERGEN, INC.

2008 EMPLOYEE STOCK PURCHASE PLAN

(as amended March 17, 2011)

1.                                        Purpose .  The purpose of the Plan is to provide employees of the Company and its Designated Subsidiaries with an opportunity to purchase Common Stock of the Company through accumulated payroll deductions.  It is the Company’s intention to have the Plan qualify as an “Employee Stock Purchase Plan” under Section 423 of the Internal Revenue Code of 1986, as amended.  The provisions of the Plan, accordingly, will be construed so as to extend and limit Plan participation in a manner consistent with the requirements of Section 423 of the Code.

2.                                        Definitions

(a)                                   “ Administrator ” means the Board or any committee appointed by the Board.

(b)                                  “ Board ” means the Board of Directors of the Company.

(c)                                   “ Code ” means the Internal Revenue Code of 1986, as amended.  Any reference to a section of the Code herein will be a reference to any successor or amended section of the Code.

(d)                                  “ Common Stock ” means the common stock of the Company.

(e)                                   “ Company ” means SuperGen, Inc., a Delaware corporation, and any Designated Subsidiary of the Company.

(f)                                     “ Compensation ” means all base straight time gross earnings, bonuses and commissions, exclusive of payments for overtime, shift premium and other compensation.

(g)                                  “ Designated Subsidiary ” means any Subsidiary which has been designated by the Administrator from time to time in its sole discretion as eligible to participate in the Plan.

(h)                                  “ Employee ” means any individual who is an Employee of the Company for tax purposes whose customary employment with the Company is at least twenty (20) hours per week and more than five (5) months in any calendar year.  For purposes of the Plan, the employment relationship will be treated as continuing intact while the individual is on sick leave or other leave of absence approved by the Company.  Where the period of leave exceeds 90 days and the individual’s right to reemployment is not guaranteed either by statute or by contract, the employment relationship will be deemed to have terminated on the 91st day of such leave.

(i)                                      “ Enrollment Date ” means the first day of each Offering Period.

(j)                                      “ Exercise Date ” means the last Trading Day of each Offering Period.

(k)                                   “ Fair Market Value ” means, as of any date, the value of Common Stock determined as follows:

(i)              If the Common Stock is listed on any established stock exchange or a national market system, including without limitation the Nasdaq Global Select Market, the Nasdaq Global Market or the Nasdaq Capital Market of The Nasdaq Stock Market, its Fair Market Value will be the closing sales price for such stock (or the closing bid, if no sales were reported) as quoted on such exchange or system for the last market trading day on the date of such determination, as reported in The Wall Street Journal or such other source as the Administrator deems reliable;

(ii)           If the Common Stock is regularly quoted by a recognized securities dealer but selling prices are not reported, its Fair Market Value will be the mean of the closing bid and asked prices for the Common Stock on the date of such determination, as reported in The Wall Street Journal or such other source as the Administrator deems reliable; or

(iii)        In the absence of an established market for the Common Stock, the Fair Market Value thereof will be determined in good faith by the Administrator.

(l)                                      “ Offering Period ” means a period of approximately six (6) months during which an option granted pursuant to the Plan may be exercised, commencing on the first Trading Day on or after May 15 and terminating on the last Trading Day in the period ending the following November 14, or commencing on the first Trading Day on or after November 15 and terminating on the last Trading Day in the period ending the following May 14. The duration of Offering Periods may be changed pursuant to Section 4 of this Plan.

(m)                                “ Plan ” means this SuperGen, Inc. 2008 Employee Stock Purchase Plan.

(n)                                  “ Purchase Price ” means an amount equal to eighty-five percent (85%) of the Fair Market Value of a share of Common Stock on the Enrollment Date or on the Exercise Date, whichever is lower.

(o)                                  “ Reserves ” means the number of shares of Common Stock covered by each option under the Plan which have not yet been exercised and the number of shares of Common Stock which have been authorized for issuance under the Plan but not yet placed under option.

(p)                                  “ Subsidiary ” means a corporation, domestic or foreign, of which not less than fifty percent (50%) of the voting shares are held by the Company or a Subsidiary, whether or not such corporation now exists or is hereafter organized or acquired by the Company or a Subsidiary.

(q)                                  “ Trading Day ” means a day on which the national stock exchanges and the Nasdaq System are open for trading.

3.                                        Eligibility

(a)                                   Any Employee who is employed by the Company on a given Enrollment Date will be eligible to participate in the Plan.

(b)                                  Any provisions of the Plan to the contrary notwithstanding, no Employee will be granted an option under the Plan (i) to the extent that, immediately after the grant, such Employee (or any other person whose stock would be attributed to such Employee pursuant to Section 424(d) of the Code)

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would own capital stock of the Company and/or hold outstanding options to purchase such stock possessing five percent (5%) or more of the total combined voting power or value of all classes of the capital stock of the Company or of any Subsidiary, or (ii) to the extent that his or her rights to purchase stock under all employee stock purchase plans of the Company and any Subsidiaries accrues at a rate which exceeds Twenty-Five Thousand Dollars ($25,000) worth of stock (determined at the Fair Market Value of the stock at the time such option is granted) for each calendar year in which such option is outstanding at any time.

4.                                        Offering Periods .  The Plan will be implemented by consecutive Offering Periods with a new Offering Period commencing on the first Trading Day on or after May 15 and November 15 of each year, or on such other date as the Administrator will determine, and continuing thereafter until terminated in accordance with Section 20 hereof.  The Administrator will have the power to change the duration of Offering Periods (including the commencement dates thereof) with respect to future offerings without stockholder approval if such change is announced at least five (5) days prior to the scheduled beginning of the first Offering Period to be affected thereafter.

5.                                        Participation

(a)                                   An eligible Employee may participate in the Plan by (i) completing a subscription agreement authorizing payroll deductions in the form of Exhibit A to this Plan and filing it with the Company’s payroll office prior to the applicable Enrollment Date or (ii) following an electronic or other enrollment procedure prescribed by the Administrator.

(b)                                  Payroll deductions for a participant will commence on the first payroll following the Enrollment Date and will end on the last payroll in the Offering Period to which such authorization is applicable, unless sooner terminated by the participant as provided in Section 10 hereof.

6.                                        Payroll Deductions

(a)                                   At the time a participant files his or her subscription agreement, he or she will elect to have payroll deductions made on each pay day during the Offering Period in an amount not exceeding twenty percent (20%) of the Compensation which he or she receives on each pay day during the Offering Period.

(b)                                  A participant may not make any additional payments into such account.

(c)                                   A participant may discontinue his or her participation in the Plan as provided in Section 10 hereof, or may decrease the rate of his or her payroll deductions during the Offering Period by completing and submitting to the Company’s payroll office a new subscription agreement authorizing a change in payroll deduction rate.  The Administrator may, in its sole discretion, limit the number of participation rate changes during any Offering Period.  The change in rate will be effective with the first full payroll period following five (5) business days after the Company’s receipt of the new subscription agreement unless the Company elects to process a given change in participation more quickly.  A participant’s subscription agreement will remain in effect for successive Offering Periods unless terminated as provided in Section 10 hereof.

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(d)                                  Notwithstanding the foregoing, to the extent necessary to comply with Section 423(b)(8) of the Code and Section 3(b) hereof, a participant’s payroll deductions may be decreased to zero percent (0%) at any time during an Offering Period.

(e)                                   At the time the option is exercised, in whole or in part, or at the time some or all of the Common Stock issued under the Plan is disposed of, the participant must make adequate provision for the Company’s federal, state, or other tax withholding obligations, if any, which arise upon the exercise of the option or the disposition of the Common Stock.  At any time, the Company may, but will not be obligated to, withhold from the participant’s compensation the amount necessary for the Company to meet applicable withholding obligations, including any withholding required to make available to the Company any tax deductions or benefits attributable to the sale or early disposition of Common Stock by the Employee.

7.                                        Grant of Option .  On the Enrollment Date of each Offering Period, each eligible Employee participating in such Offering Period will be granted an option to purchase on the Exercise Date of such Offering Period (at the applicable Purchase Price) up to a number of shares of the Common Stock determined by dividing such Employee’s payroll deductions accumulated prior to such Exercise Date and retained in the Participant’s account as of the Exercise Date by the applicable Purchase Price; provided that in no event will an Employee be permitted to purchase during each Offering Period more than 1,500 shares (subject to any adjustment pursuant to Section 19 hereof), and provided further that such purchase will be subject to the limitations set forth in Sections 3(b) and 12 hereof.  The Administrator may, for future Offering Periods, increase or decrease, in its sole discretion, the maximum number of shares of Common Stock that an Employee may purchase during each Offering Period.  Exercise of the option will occur as provided in Section 8 hereof, unless the participant has withdrawn pursuant to Section 10 hereof.  The option will expire on the last day of the Offering Period.

8.                                        Exercise of Option .  Unless a participant withdraws from the Plan as provided in Section 10 hereof, his or her option for the purchase of shares will be exercised automatically on the Exercise Date, and the maximum number of full shares subject to option will be purchased for such participant at the applicable Purchase Price with the accumulated payroll deductions in his or her account.  No fractional shares will be purchased; any payroll deductions accumulated in a participant’s account which are not sufficient to purchase a full share will be retained in the participant’s account for the subsequent Offering Period, subject to earlier withdrawal by the participant as provided in Section 10 hereof.  Any other monies left over in a participant’s account after the Exercise Date will be returned to the participant. During a participant’s lifetime, a participant’s option to purchase shares hereunder is exercisable only by him or her.

9.                                        Delivery .  As soon as reasonably practicable after each Exercise Date on which a purchase of shares of Common Stock occurs, the Company will arrange the delivery to each participant of the shares purchased upon exercise of his or her option in a form determined by the Administrator (in its sole discretion).  No participant will have any voting, dividend or other stockholder rights with respect to shares of Common Stock subject to any option granted under the Plan until such shares have been purchased and delivered to the participant as provided in this Section 9.

10.                                  Withdrawal

(a)                                   A participant may withdraw all but not less than all the payroll deductions credited to his or her account and not yet used to exercise his or her option under the Plan at any time by (i) giving written notice to the Company’s payroll office in the form of Exhibit B to this Plan or (ii) following an

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electronic or other withdrawal procedure prescribed by the Administrator.  All of the participant’s payroll deductions credited to his or her account will be paid to such participant promptly after receipt of notice of withdrawal and such participant’s option for the Offering Period will be automatically terminated, and no further payroll deductions for the purchase of shares will be made for such Offering Period.  If a participant withdraws from an Offering Period, payroll deductions will not resume at the beginning of the succeeding Offering Period unless the participant delivers to the Company a new subscription agreement.

(b)                                  A participant’s withdrawal from an Offering Period will not have any effect upon his or her eligibility to participate in any similar plan which may hereafter be adopted by the Company or in succeeding Offering Periods which commence after the termination of the Offering Period from which the participant withdraws.

11.                                  Termination of Employment .  Upon a participant’s ceasing to be an Employee for any reason, he or she will be deemed to have elected to withdraw from the Plan and the payroll deductions credited to such participant’s account during the Offering Period but not yet used to exercise the option will be returned to such participant or, in the case of his or her death, to the person or persons entitled thereto under Section 15 hereof, and such participant’s option will be automatically terminated.  The preceding sentence notwithstanding, a participant who receives payment in lieu of notice of termination of employment will be treated as continuing to be an Employee for the participant’s customary number of hours per week of employment during the period in which the participant is subject to such payment in lieu of notice.

12.                                  Interest .  No interest will accrue on the payroll deductions of a participant in the Plan.

13.                                  Stock

(a)                                   The maximum number of shares of the Company’s Common Stock which will be made available for sale under the Plan will be five hundred thousand (500,000) shares, subject to adjustment upon changes in capitalization of the Company as provided in Section 19 hereof.  If, on a given Exercise Date, the number of shares with respect to which options are to be exercised exceeds the number of shares then available under the Plan, the Company will make a pro rata allocation of the shares remaining available for purchase in as uniform a manner as is reasonably practicable and as it determines to be equitable.

(b)                                  Until the shares are issued (as evidenced by the appropriate entry on the books of the Company or of a duly authorized transfer agent of the Company), a participant will have only the rights of an unsecured creditor with respect to such shares, and no right to vote or receive dividends or any other rights as a stockholder will exist with respect to such shares.

(c)                                   Shares of Common Stock to be delivered to a participant under the Plan will be registered in the name of the participant or in the name of the participant and his or her spouse.

14.                                  Administration .  The Plan will be administered by the Board or a committee appointed by the Board.  The Administrator will have full and exclusive discretionary authority to construe, interpret and apply the terms of the Plan, to determine eligibility and to adjudicate all disputed claims filed under the Plan.  Every finding, decision and determination made by the Administrator will, to the full extent permitted by law, be final and binding upon all parties.

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15.                                  Designation of Beneficiary

(a)                                   A participant may file a written designation of a beneficiary who is to receive any shares of Common Stock and cash, if any, from the participant’s account under the Plan in the event of such participant’s death subsequent to an Exercise Date on which the option is exercised but prior to delivery to such participant of such shares and cash.  In addition, a participant may file a written designation of a beneficiary who is to receive any cash from the participant’s account under the Plan in the event of such participant’s death prior to exercise of the option.  If a participant is married and the designated beneficiary is not the spouse, spousal consent will be required for such designation to be effective.

(b)                                  Such designation of beneficiary may be changed by the participant at any time by written notice.  In the event of the death of a participant and in the absence of a beneficiary validly designated under the Plan who is living at the time of such participant’s death, the Company will deliver such shares and/or cash to the executor or administrator of the estate of the participant, or if no such executor or administrator has been appointed (to the knowledge of the Company), the Company, in its discretion, may deliver such shares and/or cash to the spouse or to any one or more dependents or relatives of the participant, or if no spouse, dependent or relative is known to the Company, then to such other person as the Company may designate.

16.                                  Transferability .  Neither payroll deductions credited to a participant’s account nor any rights with regard to the exercise of an option or to receive shares under the Plan may be assigned, transferred, pledged or otherwise disposed of in any way (other than by will, the laws of descent and distribution or as provided in Section 15 hereof) by the participant.  Any such attempt at assignment, transfer, pledge or other disposition will be without effect, except that the Company may treat such act as an election to withdraw funds from an Offering Period in accordance with Section 10 hereof.

17.                                  Use of Funds .  All payroll deductions received or held by the Company under the Plan may be used by the Company for any corporate purpose, and the Company will not be obligated to segregate such payroll deductions.  Until shares of Common Stock are issued, participants will only have the rights of an unsecured creditor with respect to such shares.

18.                                  Reports .  Individual accounts will be maintained for each participant in the Plan.  Statements of account will be given to participating Employees at least annually, which statements will set forth the amounts of payroll deductions, the Purchase Price, the number of shares purchased and the remaining cash balance, if any.

19.                                  Adjustments Upon Changes in Capitalization, Dissolution, Liquidation, Merger or Asset Sale

(a)                                   Changes in Capitalization .  Subject to any required action by the stockholders of the Company, the Reserves, the maximum number of shares each participant may purchase per Offering Period (pursuant to Section 7), as well as the price per share and the number of shares of Common Stock covered by each option under the Plan which has not yet been exercised will be proportionately adjusted for any increase or decrease in the number of issued shares of Common Stock resulting from a stock split, reverse stock split, stock dividend, combination or reclassification of the Common Stock, or any other increase or decrease in the number of shares of Common Stock effected without receipt of consideration by the Company; provided, however, that conversion of any convertible securities of the Company will not be deemed to have been “effected without receipt of consideration.”  Such adjustment will be made by the Administrator, whose determination in that respect will be final, binding and conclusive.  Except as expressly provided herein, no issuance by the Company of shares of stock of any class, or securities convertible into shares of stock of any

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class, will affect, and no adjustment by reason thereof will be made with respect to, the number or price of shares of Common Stock subject to an option.

(b)                                  Dissolution or Liquidation .  In the event of the proposed dissolution or liquidation of the Company, the Offering Period then in progress will be shortened by setting a new Exercise Date (the “ New Exercise Date ”), and will terminate immediately prior to the consummation of such proposed dissolution or liquidation, unless provided otherwise by the Administrator.  The New Exercise Date will be before the date of the Company’s proposed dissolution or liquidation.  The Administrator will notify each participant in writing, at least ten (10) business days prior to the New Exercise Date, that the Exercise Date for the participant’s option has been changed to the New Exercise Date and that the participant’s option will be exercised automatically on the New Exercise Date, unless prior to such date the participant has withdrawn from the Offering Period as provided in Section 10 hereof.

(c)                                   Merger or Asset Sale .  In the event of a proposed sale of all or substantially all of the assets of the Company, or the merger of the Company with or into another corporation, each outstanding option will be assumed or an equivalent option substituted by the successor corporation or a Parent or Subsidiary of the successor corporation.  In the event that the successor corporation refuses to assume or substitute for the option, the Offering Period then in progress will be shortened by setting a new Exercise Date (the “ New Exercise Date ”).  The New Exercise Date will be before the date of the Company’s proposed sale or merger.  The Administrator will notify each participant in writing, at least ten (10) business days prior to the New Exercise Date, that the Exercise Date for the participant’s option has been changed to the New Exercise Date and that the participant’s option will be exercised automatically on the New Exercise Date, unless prior to such date the participant has withdrawn from the Offering Period as provided in Section 10 hereof.

20.                                  Amendment or Termination

(a)                                   The Administrator may at any time and for any reason terminate, suspend or amend the Plan.  Except as provided in Section 19 hereof, no such termination can affect options previously granted, provided that an Offering Period may be terminated by the Administrator on any Exercise Date if the Administrator determines that the termination of the Plan is in the best interests of the Company and its stockholders.  Except as provided in Section 19 hereof, no amendment may make any change in any option theretofore granted which adversely affects the rights of any participant.  To the extent necessary to comply with Section 423 of the Code (or any other applicable law, regulation or stock exchange rule), the Company will obtain stockholder approval in such a manner and to such a degree as required.

(b)                                  Without stockholder consent and without regard to whether any participant rights may be considered to have been “adversely affected” as described in Section 20(a), the Administrator will be entitled to change the Offering Periods, limit the frequency and/or number of changes in the amount withheld during an Offering Period, establish the exchange ratio applicable to amounts withheld in a currency other than U.S. dollars, permit payroll withholding in excess of the amount designated by a participant in order to adjust for delays or mistakes in the Company’s processing of properly completed withholding elections, establish reasonable waiting and adjustment periods and/or accounting and crediting procedures to ensure that amounts applied toward the purchase of Common Stock for each participant properly correspond with amounts withheld from the participant’s Compensation, and establish such other limitations or procedures as the Administrator determines in its sole discretion advisable which are consistent with the Plan.

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(c)                                   In the event the Administrator determines that the ongoing operation of the Plan may result in unfavorable financial accounting consequences, the Administrator may, in its discretion and, to the extent necessary or desirable, modify, amend or terminate the Plan to reduce or eliminate such accounting consequence including, but not limited to:

(i)              amending the Plan to conform with the safe harbor definition under Statement of Financial Accounting Standards 123(R), including with respect to an Offering Period underway at the time;

(ii)           altering the Purchase Price for any Offering Period including an Offering Period underway at the time of the change in Purchase Price;

(iii)        shortening any Offering Period by setting a New Exercise Date, including an Offering Period underway at the time of the Administrator action;

(iv)       reducing the maximum percentage of Compensation a participant may elect to set aside as payroll deductions; and

(v)          reducing the maximum number of Shares a participant may purchase during any Offering Period.

Such modifications or amendments will not require stockholder approval or the consent of any Plan participants.

21.                                  Notices .  All notices or other communications by a participant to the Company under or in connection with the Plan will be deemed to have been duly given when received in the form and manner specified by the Company at the location, or by the person, designated by the Company for the receipt thereof.

22.                                  Conditions Upon Issuance of Shares .  Shares of Common Stock will not be issued with respect to an option unless the exercise of such option and the issuance and delivery of such shares pursuant thereto will comply with all applicable provisions of law, domestic or foreign, including, without limitation, the Securities Act of 1933, as amended, the Securities Exchange Act of 1934, as amended, the rules and regulations promulgated thereunder, and the requirements of any stock exchange upon which the shares may then be listed, and will be further subject to the approval of counsel for the Company with respect to such compliance.

As a condition to the exercise of an option, the Company may require the person exercising such option to represent and warrant at the time of any such exercise that the shares are being purchased only for investment and without any present intention to sell or distribute such shares if, in the opinion of counsel for the Company, such a representation is required by any of the aforementioned applicable provisions of law.

23.                                  Term of Plan .  The Plan will become effective upon the earlier to occur of its adoption by the Board or its approval by the stockholders of the Company.  It will continue in effect for a term of ten (10) years unless sooner terminated under Section 20 hereof.

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24.                                  Stockholder Approval .  The Plan will be subject to approval by the stockholders of the Company within twelve (12) months after the date the Plan is adopted by the Board.  Such stockholder approval will be obtained in the manner and to the degree required under applicable laws.

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EXHIBIT A

SUPERGEN, INC.

2008 EMPLOYEE STOCK PURCHASE PLAN

SUBSCRIPTION AGREEMENT

1.                                                                                                               hereby elects to participate in the SuperGen, Inc. 2008 Employee Stock Purchase Plan (the “ Plan ”) and subscribes to purchase shares of the Company’s Common Stock in accordance with this Subscription Agreement and the Plan.

2.                                        I hereby authorize payroll deductions from each paycheck in the amount of $                    or            % of my Compensation on each payday (from 1% to 20%) during the Offering Period in accordance with the Plan.

3.                                        I hereby authorize a change in payroll deductions from each paycheck to the amount of $                   or             % of my Compensation on each payday (from 0% to 20%) during the Offering Period in accordance with the Plan.

4.                                        I understand that said payroll deductions will be accumulated for the purchase of shares of Common Stock at the applicable Purchase Price determined in accordance with the Plan.  I understand that if I do not withdraw from an Offering Period, any accumulated payroll deductions will be used to automatically exercise my option.

5.                                        I have received a copy of the complete Plan.  I understand that my participation in the Plan is in all respects subject to the terms of the Plan.  I understand that my ability to exercise the option under this Subscription Agreement is subject to stockholder approval of the Plan.

6.                                        Shares purchased for me under the Plan should be issued in the name(s) of (Employee or Employee and Spouse only):                                               .

7.                                        I understand that if I dispose of any shares received by me pursuant to the Plan within two (2) years after the Enrollment Date (the first day of the Offering Period during which I purchased such shares), I will be treated for federal income tax purposes as having received ordinary income at the time of such disposition in an amount equal to the excess of the fair market value of the shares at the time such shares were purchased by me over the price which I paid for the shares.  I hereby agree to notify

the Company in writing within thirty (30) days after the date of any disposition of shares and I will make adequate provision for Federal, state or other tax withholding obligations, if any, which arise upon the disposition of the Common Stock .  The Company may, but will not be obligated to, withhold from my compensation the amount necessary to meet any applicable withholding obligation including any withholding necessary to make available to the Company any tax deductions or benefits attributable to sale or early disposition of Common Stock by me. If I dispose of such shares at any time after the expiration of the two (2)-year holding period, I understand that I will be treated for federal income tax purposes as having received income only at the time of such disposition, and that such income will be taxed as ordinary income only to the extent of an amount equal to the lesser of (i) the excess of the fair market value of the shares at the time of such disposition over the purchase price which I paid for the shares, or (ii) fifteen percent (15%) of the fair market value of the shares on the first day of the Offering Period.  The remainder of the gain, if any, recognized on such disposition will be taxed as capital gain.

8.                                        I hereby agree to be bound by the terms of the Plan.  The effectiveness of this Subscription Agreement is dependent upon my eligibility to participate in the Plan.

9.                                        In the event of my death, I hereby designate the following as my beneficiary(ies) to receive all payments and shares due me under the Plan:

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I UNDERSTAND THAT THIS SUBSCRIPTION AGREEMENT WILL REMAIN IN EFFECT THROUGHOUT SUCCESSIVE OFFERING PERIODS UNLESS TERMINATED BY ME.

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EXHIBIT B

SUPERGEN, INC.

2008 EMPLOYEE STOCK PURCHASE PLAN

NOTICE OF WITHDRAWAL

The undersigned participant in the Offering Period of the SuperGen, Inc. 2008 Employee Stock Purchase Plan which began on                        20    (the “ Enrollment Date ”) hereby notifies the Company that he or she hereby withdraws from the Offering Period.  He or she hereby directs the Company to pay to the undersigned as promptly as practicable all the payroll deductions credited to his or her account with respect to such Offering Period.  The undersigned understands and agrees that his or her option for such Offering Period will be automatically terminated.  The undersigned understands further that no further payroll deductions will be made for the purchase of shares in the current Offering Period and the undersigned will be eligible to participate in succeeding Offering Periods only by delivering to the Company a new Subscription Agreement.

EXHIBIT 4.2

ADOPTED                              2010

ASTEX THERAPEUTICS LIMITED

THE ASTEX THERAPEUTICS LIMITED
2010 SHARE OPTION SCHEME

RULES OF THE ASTEX THERAPEUTICS LIMITED 2010 SHARE OPTION SCHEME

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RULES OF THE ASTEX THERAPEUTICS LIMITED

2010 SHARE OPTION SCHEME

INTRODUCTION

Astex Therapeutics Limited wants to ensure that it can recruit and retain employees and consultants who will enhance shareholder value.  It has therefore decided to implement a share scheme on the terms set out in these Rules. In doing so, its primary intention is to recruit new employees and consultants and to motivate existing employees and consultants to remain with the Company and its subsidiaries.

This Scheme comprises three Parts.  Options granted under Part A are intended to be qualifying options under the Enterprise Management Incentives code set out in Schedule 5 of the Income Tax (Earnings and Pensions) Act 2003.  Options granted under Part B are not qualifying options and are, for tax purposes, unapproved.  Parts A and B are “employee share schemes” within the definition in section 1166 of the Companies Act 2006.  Options granted under Part C are also unapproved for tax purposes and can be granted to consultants who are not employees of the Company and its subsidiaries but provide services to or are non-executive directors of the Company and its subsidiaries.

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References to any statutory provision are to that provision as amended or re-enacted from time to time, and, unless the context otherwise requires, words in the singular shall include the plural and vice versa, and words importing the masculine gender shall include the feminine and vice versa.

2.                                       GRANT OF OPTIONS

2.1                                  Subject to Rule 2.8, the Grantor may grant an Option to an Executive at any time.

2.2                                 Where the Grantor grants an EMI Option which is in excess of the Individual Limit the excess shall be an Unapproved Option.

2.3                                 Where the Grantor grants an EMI Option which is in excess of the Company Limit the excess shall be an Unapproved Option.

2.4                                 If an Option is deemed to be an Unapproved Option pursuant to Rules 2.2 and 2.3 and/or Rule 2.3, it shall be deemed to have been granted under Part B of these Rules.

2.5                                  The right to exercise an Option may be subject to conditions imposed by the Grantor in accordance with Rule 3.

2.6                                  As soon as practicable after the Grantor decides to grant an Option to an Executive the Grantor and the Executive and if the Grantor so directs, the Company shall enter into an enforceable Agreement which shall state:

(a)                                   the Date of Grant of the Option;

(b)                                  that the Option is an EMI Option (as the case may be);

(c)                                   that the Option is granted under the provisions of Schedule 5 (in respect of an EMI Option);

(d)                                  the number, or maximum number, of Shares that may be acquired;

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(e)            the Exercise Price payable for each Share subject to the Option or the method by which that price is to be determined;

(f)             any conditions imposed or dates determined by the Directors pursuant to Rule 3; and

(g)            when and how the Option may be exercised.

such Agreement shall include any other details required pursuant to paragraph 37 of Schedule 5.

2.7            Subject to the right of a deceased Optionholder’s personal representatives to exercise an Option in accordance with Rule 6.3, every Option shall be personal to the Executive to whom it is granted and shall not be capable of being transferred, assigned or charged.

2.8            The Grantor may grant an EMI Option to an Executive only if all of the following conditions are satisfied at the Date of Grant immediately prior to the grant of the proposed EMI Option:

(a)             the Directors have satisfied themselves that it is being granted for commercial reasons in order to recruit or retain an employee and not as part of a scheme or arrangement the main purpose, or one of the main purposes, of which is the avoidance of tax;

(b)            the total Market Value of Shares in the Company in respect of which unexercised EMI Options subsist, shall not exceed £3 million or such other value as shall be specified at that time in paragraph 7 of Schedule 5;

(c)             the Company or a Group Company as the case may be meets the trading activities requirement of paragraphs 13 or 14 of Schedule 5;

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(d)            the gross assets of the Company do not exceed £30 million (or such other amount as may at that time be specified in paragraph 12 of Schedule 5).  For these purposes “gross assets” means:

(i)             the sum of all the fixed and current assets of the Company; or

(ii)            if the Company is a member of a group of companies, the sum of the fixed and current assets of all the Group Companies excluding any member’s rights against, or shares in or securities of, another Group Company) determined in accordance with HMRC Statement of Practice 2/06 or its successors; and

(e)             the qualifying subsidiaries requirement of paragraph 10 of Schedule 5 is satisfied.

2.9            For the purposes of Rule 2.8(b) above, the Market Value of a Share shall be determined in accordance with paragraphs 5(6) to 5(8) of Schedule 5 in respect of the day on which each of the relevant unexercised EMI Options was granted.

2.10          No warranty or representation is given that any Option granted under this Scheme is, at its Date of Grant or will remain at any or all times thereafter, an EMI Option.  Neither the Company nor any Group Company nor any of their respective members or officers shall have any liability to any Executive or Optionholder if and to the extent that any of the reliefs or tax advantages offered by Chapter 9 of ITEPA, and/or by Schedule 5, are not available

3.              CONDITIONS OF EXERCISE

3.1            The Grantor may at the Date of Grant determine that the right to exercise an Option shall be conditional upon the occurrence of an Exit.

3.2            The Grantor may at the Date of Grant determine that the right to exercise an Option shall be conditional upon the satisfaction of an objective condition

12

imposed by the Grantor at the Date of Grant, provided that such performance condition is capable of being satisfied within ten years of the Date of Grant.

3.3            When granting an Option, the Grantor may, if in its discretion it thinks fit determine any date or dates prior to the day before the tenth anniversary of its Date of Grant on which the Option is first exercisable in whole or in part, and, where on any date only part is exercisable, the number of Shares in respect of which such partial exercise may be made.

3.4            If, after the Grantor has imposed any condition to be satisfied pursuant to Rule 3.2, events occur which cause the Directors to consider the condition has become unreasonable, unfair or impractical, the Grantor may, in its discretion (provided such discretion is exercised fairly and reasonably) amend, relax or waive such condition provided that any condition which is amended or relaxed will be no more and no less difficult to satisfy than when it was originally imposed or last amended or relaxed.

3.5            The Grantor shall notify all relevant Optionholders in writing of any amendment, relaxation or waiver of any conditions made pursuant to Rule 3.4.

3.6            Once a performance condition has been specified in relation to an Option in accordance with Rule 3.2, the Grantor may (with the prior consent of the Directors), waive that condition altogether.

4.              INDIVIDUAL LIMITS

4.1            Any EMI Option granted to an Executive by the Grantor shall be limited and take effect so that, immediately following such grant, the aggregate Market Value of:

(a)            all shares in respect of which EMI Options or other options which are qualifying options within the meaning given in paragraph 1 of Schedule

13

5 are then held by him and granted by reason of his employment with any one or more Group Companies;

(b)            all other shares in respect of which EMI Options or other options which are qualifying options within the meaning given in paragraph 1 of Schedule 5 were granted to him within the preceding three years by reason of his employment with any one or more Group Companies, whether or not such EMI Options have been exercised or released; and

(c)            all shares in respect of which options were granted to him under a company share option plan approved by HMRC under Schedule 4 to ITEPA by reason of his employment with the Employer Company or any other Group Company, which options have neither lapsed nor been exercised or released,

shall not exceed £120,000 or such other amount as may from time to time be specified in paragraph 6(1) of Schedule 5.

4.2            For the purposes of Rule 4.1, the Market Value of the Shares or shares shall be their Market Value at the date or dates on which the relevant EMI Options or other options were granted or such earlier time or times as may be agreed with HMRC.

5.              SCHEME LIMITS

5.1            No Option shall be granted if and to the extent that immediately after such grant (“ the relevant time ”) the aggregate number of Shares in respect of which options or rights to subscribe for or acquire Shares would then have been granted (and not subsequently lapsed, cancelled or surrendered) under this Scheme or any other share scheme of the Company would on or after the date of adoption of this Scheme exceed 700,000.

5.2            If the grant of an Option would, immediately following its grant, cause the limit in Rule 5.1 to be exceeded, such Option shall take effect as an Option

14

over the maximum number of Shares which does not cause the relevant limit to be exceeded.  If more than one Option is granted on the same Date of Grant the number of Shares to which each Option would otherwise be subject shall be reduced pro rata.

6.              RIGHTS OF EXERCISE AND LAPSE OF OPTIONS

6.1            If there is in force at the relevant time a Shareholders’ Agreement, an Option may be exercised only if the Optionholder has entered into a Deed of Adherence if required by an Investor Majority (such term as defined in the Shareholders Agreeement).

6.2            Save as provided in Rules 6.4 (Death), 6.5 (Disqualifying Events), 8 (Sale), 9 (Winding Up) and 10 (Exchange of Options) an Option may not be exercised before whichever is the latest of:

(a)            the date stated in the Agreement;

(b)            any date or dates which may have been specified in accordance with Rule 3.3; and

(c)            the date on which any condition specified pursuant to Rules 3.1 and 3.2 (as amended, relaxed or waived pursuant to Rule 3.4) has been satisfied,

but in any event may not be exercised later than the day before the tenth anniversary of the Date of Grant.

6.3            Save as provided in Rules 6.4 (Death), 6.5 (Disqualifying Events), 6.6 (Good Leavers), 8 (Sale etc), 9 (Winding Up) and 10 (Exchange of Options), an Option may be exercised by an Optionholder only while he is an Executive.

6.4            Subject to Rule 6.2, an Option may be exercised by the personal representatives of a deceased Optionholder during the period of one year following the date of death.

15

6.5            Unless and to the extent the Directors decide otherwise, an Option may be exercised during the period of 40 days following a Disqualifying Event.

6.6            Subject to Rule 6.2, if an Optionholder ceases to hold any office or employment with a Group Company on account of:

(a)            injury, ill-health or disability (evidenced to the satisfaction of the Directors);

(b)            the Optionholder’s resignation pursuant to a period of maternity leave;

(c)            redundancy (within the meaning of the Employment Rights Act 1996);

(d)            retirement at normal retirement age (including late retirement) or early retirement with the consent of the Group Company which employs the Optionholder;

(e)            the transfer of the undertaking or part-undertaking in which the Optionholder is employed to a person other than a Group Company;

(f)             the Company by which the Optionholder is employed ceasing to be a Group Company; or

(g)            any other reason which the Directors consider reasonably justifies the exercise of the Option,

the Option may be exercised within the period of 6 months after such event.

6.7            An Option shall lapse on the occurrence of the earliest of the following:

(a)            the day before the tenth anniversary of the Date of Grant;

(b)            the expiry of the period (if any) allowed for the satisfaction of any condition of exercise pursuant to Rule 3 without such condition having been satisfied or the date on which it becomes apparent to the Directors

16

in their absolute discretion that any such condition has become incapable of being satisfied;

(c)            the expiry of the applicable periods specified in Rules 6.4 (Death) and 6.6 (Good Leavers), except that if an Optionholder dies while time is running under Rule 6.6, the Option shall not lapse until the expiry of the period in Rule 6.4;

(d)            unless and to the extent the Directors decide otherwise, the expiry of the period specified in Rule 6.5 (Disqualifying Events);

(e)            subject to Rule 10 (Exchange of Options) the expiry of the applicable periods specified in Rules 8.1, 9.1 or 9.2 (Reconstructions etc);

(f)             the expiry of the applicable periods specified in Rule 9.3 (Winding Up);

(g)            save as provided in Rules 6.4 (Death), 6.5 (Disqualifying Events), 6.6 (Good Leavers) and 8 (Sale) the date on which the Optionholder ceases to hold any office or employment with a Group Company;

(h)            the date on which a resolution is passed, or an order is made by the Court, for the compulsory winding up of the Company; and

(i)             the date on which the Optionholder becomes bankrupt or does or omits to do anything as a result of which he is deprived of the legal or beneficial ownership of the Option.

7.              EXERCISE OF OPTIONS

7.1            An Option shall be exercisable in whole or in part by notice in writing (in the form prescribed by the Company from time to time) given by the Optionholder (or his personal representatives as the case may be) to the Company.  The notice of exercise of the Option shall be accompanied by a remittance in cleared funds for the aggregate of the Exercise Prices payable or (at the Directors discretion)

17

an undertaking, in such form as the Directors may from time to time prescribe, to make such payment.

7.2            Subject to Rules 7.3 and 7.4, within 30 days of the Option exercise the Directors shall procure the transfer or issue of the shares in respect of which the Option has been validly exercised and shall issue a definitive certificate or such other acknowledgement of shareholding as is from time to time permitted in respect of the Shares transferred, unless the Directors consider that such allotment or transfer would not be lawful in the relevant jurisdiction.

7.3            Each Option shall be granted subject to the condition that the Optionholder shall meet the Company’s or Grantor’s secondary National Insurance Contributions due on the exercise or release of the Option.  For this purpose, the Optionholder may be required, if requested by the Company or Grantor at any time before the exercise or release of the Option, to enter into an election to transfer liability for such National Insurance Contributions in a form approved by HMRC and acceptable to the Company or Grantor and to enter into such arrangements as may be approved by HMRC in order to secure the transfer of the liability.

7.4            If any Group Company or Grantor is liable to account for tax or social security contributions (in any jurisdiction) for which an Optionholder is liable by virtue of the exercise of the Option that or any other Group Company or the Grantor or the trustee of any trust which is intended to be an employee share scheme pursuant to Section 1166 of the Companies Act 2006 may:

(a)            withhold the appropriate amount of tax or social security from the Optionholder’s remuneration; or

(b)            make such other arrangements as it considers necessary (including the sale of Shares on behalf of the Optionholder) to finance the amounts in (a) above,

unless the Optionholder discharges the liability himself at the date of exercise.

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7.5            Shares allotted under this Scheme shall rank pari passu in all respects with the Shares of the same class for the time being in issue save as regards any rights attaching to such Shares by reference to a record date prior to the date of allotment and in the case of a transfer of existing Shares the transferee shall not acquire any rights attaching to such Shares by reference to a record date prior to the date of such transfer.

7.6            The Directors may in their sole and absolute discretion require an Optionholder, on demand, to enter into a Section 431 Election, and no Shares shall be issued or transferred on exercise of an Option whilst the holder of that Option is in breach of this Rule 7.6.

7.7            If an Option is exercised in connection with a Sale, the Grantor may, instead of requiring payment for the aggregate of the Exercise Prices for the relevant Shares accept arrangements satisfactory to them for such aggregate Exercise Price to be settled out of the proceeds of sale of those Shares.

7.8            If an Option is exercised in connection with an Admission, the Grantor may, instead of requiring payment for the aggregate of the Exercise Prices for the relevant Shares accept arrangements satisfactory to them for the sale of some or all of the relevant Shares in connection with the Admission and the payment of the aggregate Exercise Price out of the proceeds of sale (net of any costs of sale).

8.              SALE

8.1            If the Directors in their discretion so decide prior to a Sale, any Option may be exercised immediately before and conditionally upon such Sale or within six months thereafter or such shorter period as the Directors may notify in writing to the Optionholders provided that if the Directors in their discretion so determine such exercise of an Option shall be conditional upon the prior written agreement of the relevant Optionholder with the Company to sell immediately upon exercise of his Option the Shares acquired on exercise to such person as may be

19

specified by the Directors on terms that are not materially less advantageous than the terms upon which the other Shares are to be or have been disposed of under the Sale. Any conditions imposed pursuant to Rules 3.1, 3.2, 3.3 and 3.4, shall cease to apply unless the Directors decide otherwise.

8.2            Any Optionholder who wishes to exercise an Option pursuant to Rule 8.1, shall do so by serving a Conditional Exercise Notice on the Company specifying the number of Shares over which the Optionholder wishes to exercise his Option (which shall not in any event exceed the number of Shares in respect of which the Option subsists). If the Sale does not take place any Conditional Exercise Notice served in anticipation of the Sale shall be of no effect.

8.3            A Conditional Exercise Notice given in accordance with Rule 8.2 may not be withdrawn.

8.4            The service of a Conditional Exercise Notice in accordance with Rule 8.2 shall constitute the Company the Optionholder’s agent for the sale of all the Shares specified in the Conditional Exercise Notice to the Purchaser on terms which are no less favourable than the terms on which the other Shares are acquired by the Purchaser from the other shareholders of the Company.

8.5            If the Company is able to sell the Shares to the Purchaser in accordance with Rule 8.4 the Directors may appoint any person nominated by them to be the attorney of an Optionholder to sign any agreement and to complete, execute and deliver in the name of and on behalf of the Optionholder any stock transfer form and any other documents necessary to transfer the Shares over which the Option is exercised to the Purchaser against payment of the purchase money or other consideration to the Company.

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8.6            The Directors shall notify Optionholders of any impending Sale and of any time limit of less than six months imposed under Rule 8.1 in sufficient time before a binding agreement for the Sale (whether conditional or unconditional) is signed to allow the Optionholders an opportunity to exercise their Options, being at least 5 business days before the date on which such agreement is signed.

8.7            The Company may receive the purchase money or other consideration on behalf of an Optionholder and give a valid discharge to the Purchaser for it.  The Company shall be entitled to deduct and retain out of the purchase money such amounts as may be required to meet any liability of the Optionholder pursuant to Rule 7.4 and in the event that non cash consideration is received for the Sale the Company shall be entitled to sell such proportion of the non cash consideration as shall be required to meet the Optionholder’s liability under Rule 7.4.

9.              WINDING-UP

9.1            If an order is made or an effective resolution is passed for the winding up of the Company each Option (to the extent it remains unexercised at the date of such order or resolution) may be exercised (subject to any applicable performance conditions set in accordance with Rule 3.2 being met or waived) within fourteen days after the date on which an order is made or an effective resolution is passed for the winding up of the Company and, to the extent not exercised all Options shall lapse at the expiry of such fourteen day period.

10.           EXCHANGE OF OPTIONS

10.1          In the event of a Sale which is also a “company reorganisation” (as such term is defined in paragraph 39 of Schedule 5) an Optionholder may (with the consent of the acquiring company) release his Option in consideration of the

21

grant of a Replacement Option within the period which begins on the date of the Sale and ends fourteen days later.

10.2          If, in the event of a Qualifying Exchange of Shares, an Optionholder is irrevocably offered the grant of a Replacement Option on the occurrence of that Qualifying Exchange of Shares, then:

(a)       his Option shall, upon such offer being made, cease to be exercisable without the consent of the Directors until such time as the Replacement Option is granted following the Qualifying Exchange of Shares; and

(b)      his Option shall lapse on the Qualifying Exchange of Shares occurring if the Optionholder has not by then accepted the offer so made to him provided that if such an offer of a Replacement Option has been made and accepted, the Company shall be obliged to procure the grant of such Replacement Option and the Optionholder shall be obliged to agree to the release of his Option in exchange for such grant within a period of fourteen days beginning with the time when the “new company” referred to in paragraph 40(1)(a) of Schedule 5 obtains Control of the Company pursuant to the Qualifying Exchange of Shares.

10.3          For the avoidance of doubt it is declared that a Replacement Option shall not be exercisable in accordance with Rule 8.2 by virtue of the event by reason of which that Replacement Option was granted.

10.4          If a Replacement Option is granted to an Optionholder pursuant to this Rule 10, these Rules shall apply to that Replacement Option as if it had been granted at the time when the released Option was granted and as if in these Rules:

(a)                                   references to “the Company” were references to the company to the shares of which such Replacement Option relates;

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(b)                                  references to “Shares” were references to those shares;

(c)                                   references to the “Option” were to the Replacement Option which is an option to subscribe for or to acquire those shares;

(d)                                  references to the “Exercise Price” were references to the amount per share payable on exercise of such Replacement Option; and

(e)                                   the expressions “Optionholder”, “the Directors”, and “Shares” were defined in Rule 1 on the basis of the foregoing substituted references.

11.           VARIATION OF SHARE CAPITAL

11.1          In the event of any capitalisation, rights issue, consolidation, subdivision, reduction or other variation of the share capital of the Company:

(a)                                   the number of Shares comprised in an Option;

(b)                                  the Exercise Price in respect of such Shares; and

(c)                                   where an Option has been exercised pursuant to the provisions of these Rules but no Shares have been allotted or transferred in satisfaction of such exercise, the number of Shares to be so allotted or transferred and the Exercise Price in respect of such Shares,

may, subject (where required) to the prior approval of HMRC, be varied in such manner as the Directors shall determine and (save in the event of a capitalisation) the Auditors shall confirm in writing to be in their opinion fair and reasonable, provided that no variation shall be made which would result in the Exercise Price for an allotted Share being less than its nominal value.

11.2          The Directors may take such steps as they consider necessary to notify Optionholders of any adjustment made under this Rule 11 and to call in, cancel, endorse, issue or re-issue any Agreement consequent upon such adjustment.

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12.           ADMINISTRATION

12.1          The Directors shall have power from time to time to make and vary such regulations (not being inconsistent with this Scheme) for the implementation and administration of this Scheme and/or the Agreement as they think fit.

12.2          The decision of the Directors shall be final and binding in all matters relating to this Scheme (other than in the case of matters to be determined or confirmed by the Auditors in accordance with this Scheme).

12.3          The costs of establishing and administering this Scheme shall be borne by the Company.

12.4          The Company may, but shall not be obliged to, provide Executives or Optionholders with copies of any notices circulars or other documents sent to shareholders of the Company.

12.5          Within 92 days (or such longer period as may from time to time be permitted by Schedule 5) of granting an EMI Option under this Scheme notice shall be given to HMRC by the Employer Company which shall contain:

(a)                                   information required by HMRC pursuant to paragraph 44 of Schedule 5;

(b)                                  a declaration from a director or the Company Secretary of the Employer Company, that in his opinion the requirements of Schedule 5 have been met in relation to an Option under this Scheme and that to the best of his knowledge, the information provided is correct and complete; and

(c)                                   a declaration from the Optionholder to whom the Option is granted that he meets the Committed Time requirement.

13.           AMENDMENTS

13.1          Notwithstanding Rule 13.2, if HMRC raise a notice of enquiry pursuant to paragraph 46 of Schedule 5 and conclude that the requirements of Schedule 5

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have not been met in relation to this Scheme and/or the Agreement (as the case may be) the Directors may alter the Rules of this Scheme as may be necessary to ensure that the requirements of Schedule 5 have been met.

13.2          The Directors may amend the Rules of this Scheme by a resolution of the Directors provided that where any alteration would abrogate or adversely affect the subsisting rights of an Optionholder it will not be effective unless such alteration is made with the consent in writing of the Optionholder.

14.           GENERAL

14.1          This Scheme shall commence upon the date the Company adopts this Scheme and the Company in general meeting or the Directors in their absolute discretion may at any time terminate this Scheme.  On termination no further Options may be granted but such termination shall be without prejudice to any accrued rights in existence at the date thereof.

14.2          The Company will at all times keep available sufficient Shares, or shall ensure that sufficient Shares will be available, to satisfy the exercise to the full extent still possible of all Options not lapsed pursuant to the provisions of these Rules, taking account of any other obligations of the Company to issue Shares.

14.3          Notwithstanding any other provision of this Scheme:

(a)                                   this Scheme shall not form part of any contract of employment between any Group Company and any employee of any such company and the rights and obligations of any individual under the terms of his office or employment with any Group Company shall not be affected by his participation in this Scheme or any right which he may have to participate in it and this Scheme shall afford such an individual no additional rights to compensation or damages in consequence of the termination of such office or employment for any reason whatsoever, including if such termination of employment was lawful or unlawful;

25

(b)                                  no Optionholder shall be entitled to any compensation or damages for any loss or potential loss which he may suffer by reason of being unable to exercise an Option in consequence of the loss or termination of his office or employment with any Group Company for any reason whatsoever including if such termination of employment was lawful or unlawful;

(c)                                   this Scheme shall not confer on any person any legal or equitable rights (other than those constituting the Options themselves) against any Group Company directly or indirectly, or give rise to any cause of action at law or in equity against any Group Company.

14.3          Any Group Company may, pursuant to section 1 of the Contracts (Rights of Third Parties) Act 1999, enforce in its own right Rules 7.3, 7.4 and 14.4 notwithstanding that it is not a party to these Rules or any Agreement.

14.4          Except as provided in Rule 14.3, a person who is not a party to these Rules or any Agreement has no right under the Contracts (Rights of Third Parties) Act 1999 to enforce any provision of these Rules or any Agreement but this does not affect any right or remedy of a third party which exists or is available apart from that Act

14.4          Save as otherwise provided in this Scheme any notice or communication to be given by the Company to any Executive or Optionholder may be personally delivered or sent by fax or by ordinary post to his last known address. It shall be the responsibility of the Optionholder to notify the Company of any change of address. Where a notice or communication is sent by post it shall be deemed to have been received 48 hours after the same was put into the post properly addressed and stamped and where a notice or communication is sent by fax it shall be deemed to have been received at the time when it was sent.  Share certificates and other communications sent by post will be sent at the risk of the Executive or Optionholder concerned and the Company shall have no liability

26

whatsoever to any such person in respect of any notification, document, share certificate or other communication so given, sent or made.

14.5          Any notice to be given to the Company shall be delivered or sent by either post or fax to the Company at its registered office and shall be effective upon receipt.

14.6         This Scheme and all Options granted under it shall be governed by and construed in accordance with English law.

PART B

15            DIFFERENCES FROM PART A

15.1         The provisions of Part A shall apply to an Option granted under this Part B but subject to the following provisions of this Part B.

15.2         Any Option granted pursuant to this Part B of the Scheme shall be an Unapproved Option.

15.2          In Rule 1.1, the following definitions shall apply:

(a)             “Executive” means a bona fide employee of a Group Company (including any director employed on a service contract);

(b)            “Share” means a share in the capital of the Company

15.3          The following Rules shall not apply:

(a)             2,2, 2.3, 2.4, 2.8, 2.9, 4.1, 4.2, 6.3, 10.1, 12.5, 13.1

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15.3          Rule 2.6 shall be read and construed as if Rule 2.6(b) and Rule 2.6(c) shall not apply and as if the words “and in the case of an EMI Option” were deleted.

15.4          Rule 6.5 shall apply to Options granted under this Part B as if such Disqualifying Event applies to any Option granted under this Part B as it would to an EMI Option

15.5          Rule 10.2 shall apply to Options granted under this Part B as if such options were EMI Options and the Replacement Options were also EMI Options.

PART C

16            DIFFERENCES FROM PART B

16.1          The provisions of Part B shall apply to an Option granted under this Part C but subject to the following provisions of this Part C.

16.2          In Rule 1.1, the following definitions shall apply:

“ Consultant ” means a person firm or company engaged by the Company or the Subsidiary to supply goods and/or services to one or more Group Companies;

“ Consultant’s Employee ” means any employee or director of a Consultant;

“ Executive ” means:

(a)            a Non-Executive Director; or

(b)            a Consultant; or

(c)             a Consultant’s Employee.

“ Leaver ” means an Optionholder who:

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(a)                                    if he is a Non-Executive Director, ceases for any reason whatsoever (including death) to be a director of any Group Company;

(b)                                   if he is a Consultant, ceases for any reason whatsoever (including death or liquidation) to be engaged to supply goods and/or services to any Group Company; and

(c)                                    if he is a Consultant’s Employee, either:

(i)             he ceases for any reason whatsoever (including death) to hold the employment or directorship with the Consultant by reference to which he was eligible to receive the Option; or

(ii)            that Consultant ceases for any reason whatsoever (including death or liquidation) to be engaged to supply goods and/or services to any Group Company.

“ Non-Executive Director ” means a director of any Group Company who is not eligible to receive Options under Parts A or B of these Rules;

16.3          If the Executive:

(a)    becomes a Leaver prior to the date on which he is entitled to exercise his Option, the Option shall lapse on the date he becomes a Leaver.

(b)    (subject to 16.4 below) becomes a Leaver after the date on which he is entitled to exercise his Option, the Option may be exercised in accordance with Rule 6 (for the avoidance of doubt, ignoring Rule 6.3 which does not apply to this Part C).

16.4          If the Executive becomes a Leaver by reason of any breach by the Executive of the contract pursuant to which the Executive’s services are provided to the Company or the Subsidiary, the Option shall not be exercised at all and shall lapse in its entirety on the occurrence of such breach.

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16.5          If the Optionholder derives any value from the grant of an Option, or the issue of shares arising on exercise of an Option, and that value becomes subject to UK Value Added Tax or its equivalent in any other jurisdiction, the value attributable to the Option grant or, as the case may be, the shares issued on exercise of an Option, shall be exclusive of any such tax, and the Optionholder shall be liable to pay such tax to the Company on presentation of an appropriate invoice (together with any related interest, fines, costs or penalties which may become payable).

16.6          If any sum is due from a Consultant’s Employee under Rules 7.3 or 7.4, any Group Company may deduct that sum from any monies due and payable to the Consultant by reference to which the Consultant’s Employee was eligible to receive the Option (and it shall be the responsibility of that Consultant to recover the amount deducted from the Consultant’s Employee).

(b)                                   procure that his employer makes all appropriate returns of information to HMRC or the equivalent authority in any other jurisdiction in respect of any Options granted to him (including, for the avoidance of doubt, Form 42 in the UK);

16.8          An Option held by an Optionholder that is a body corporate shall lapse if:

(a)                                    That Optionholder is placed into, or a resolution is passed or an order is made for the Optionholder to be placed into, receivership, liquidation, administration, administrative receivership (or the equivalent under the laws of any countries outside the United Kingdom); or

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(b)                                   A resolution is passed or an order is made for the winding up of the Optionholder; or

(c)                                    The Optionholder enters into any composition or arrangement with its creditors.

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EXHIBIT 4.3

[OPTION HOLDER]

and

SUPERGEN, INC.

REPLACEMENT OPTION AGREEMENT

relating to the

Astex Therapeutics Limited 2010 Share Option Scheme

THIS REPLACEMENT OPTION AGREEMENT is made on

2011

BETWEEN

(1)            [OPTION HOLDER] of [                            ] (the “Optionholder”); and

(2)            SUPERGEN, INC. whose registered office is at 4140 Dublin Boulevard, Suite 200, Dublin, CA 94568 USA (the “Acquiring Company”);

INTRODUCTION

(A)           The Optionholder is the holder of an EMI option granted by Astex Therapeutics Limited (the “Company”) under the rules of the Astex Therapeutics Limited 2010 Share Option Scheme (the “Plan”), the details of which are set out in Schedule 1 (the “Old Option”).

(B)            The Acquiring Company has acquired all of the shares in the Company by means of a scheme of arrangement (the “Scheme”).  Pursuant to rule 10 of the Plan rules, the Acquiring Company would like to grant a new replacement option (the “ New Option”) to the Optionholder.

(C)            The Optionholder released the rights under the Old Option in consideration for the grant of the New Option in a Form of Election in response to a rollover proposal made in a letter to Optionholders dated [          ] conditional upon the Scheme being effective.

(D)           Not all of the requirements under rule 10 of the Plan rules are satisfied and the New Option will be an unapproved option rather than an EMI option.

AGREED TERMS

1.              Grant of New Option

1.1            The Acquiring Company grants the New Option under the terms of the Plan so that the Optionholder has an option to acquire the number of ordinary shares in the Acquiring Company at the Exercise Price as is set out in Schedule 2.

1.2            Subject to clause 1.1, the Acquiring Company and the Optionholder agree that the terms and conditions of the New Option are the same as the terms and conditions for the Old Option and that the Option Agreement for the Old Option shall be referred to for such details.

1.3            The New Option is granted and exercisable subject to the terms and conditions set out in the rules of the Plan, save that all references to the Company in the rules of the Plan shall be read and construed as references to the Acquiring Company. Exercise of the New Option shall be conditional upon the Optionholder making good any tax liability (including employer’s national insurance contributions) in relation to the New Option in accordance with rule 7 of the Plan.

1.4            The Optionholder confirms that he/she understands that the New Option will be taxed as an unapproved option rather than an EMI option.

1.5            The New Option may not be exercised later than the day before the tenth anniversary of the Date of Grant of the Old Option.

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2.              GENERAL PROVISIONS

2.1            This agreement may be executed in any number of counterparts all of which taken together shall constitute one and the same instrument.  Any party to this agreement may enter into this agreement by executing any such counterpart.

2.2            This agreement shall be governed by and construed in accordance with English law and the parties irrevocably submit to the non-exclusive jurisdiction of the English Courts to settle any claims, disputes or issues which may arise out of this agreement.

This Replacement Option Agreement has been executed and delivered as a deed on the date written above.

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EXHIBIT 4.4

[OPTION HOLDER]

and

SUPERGEN, INC.

REPLACEMENT OPTION AGREEMENT

relating to the

Astex Therapeutics Limited 2010 Share Option Scheme

THIS REPLACEMENT OPTION AGREEMENT is made on

2011

BETWEEN

(1)            [OPTION HOLDER] of [                            ] (the “Optionholder”); and

(2)            SUPERGEN, INC. whose registered office is at 4140 Dublin Boulevard, Suite 200, Dublin, CA 94568 USA (the “Acquiring Company”);

INTRODUCTION

(A)           The Optionholder is the holder of an unapproved option granted by Astex Therapeutics Limited (the “Company”) under the rules of the Astex Therapeutics Limited 2010 Share Option Scheme (the “Plan”), the details of which are set out in Schedule 1 (the “Old Option”).

(B)            The Acquiring Company has acquired all of the shares in the Company by means of a scheme of arrangement (the “Scheme”).  Pursuant to rules 10 and 15 of the Plan rules, the Acquiring Company would like to grant a new replacement option (the “ New Option”) to the Optionholder.

(C)            The Optionholder released the rights under the Old Option in consideration for the grant of the New Option in a Form of Election in response to a rollover proposal made in a letter to Optionholders dated [          ] conditional upon the Scheme being effective.

AGREED TERMS

1.              Grant of New Option

1.1            The Acquiring Company grants the New Option under the terms of the Plan so that the Optionholder has an option to acquire the number of ordinary shares in the Acquiring Company at the Exercise Price as is set out in Schedule 2.

1.2            Subject to clause 1.1, the Acquiring Company and the Optionholder agree that the terms and conditions of the New Option are the same as the terms and conditions for the Old Option and that the Option Agreement for the Old Option shall be referred to for such details.

1.3            The New Option is granted and exercisable subject to the terms and conditions set out in the rules of the Plan, save that all references to the Company in the rules of the Plan shall be read and construed as references to the Acquiring Company. Exercise of the New Option shall be conditional upon the Optionholder making good any tax liability (including employer’s national insurance contributions) in relation to the New Option in accordance with rule 7 of the Plan.

1.4            The New Option may not be exercised later than the day before the tenth anniversary of the Date of Grant of the Old Option.

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2.              GENERAL PROVISIONS

2.1            This agreement may be executed in any number of counterparts all of which taken together shall constitute one and the same instrument.  Any party to this agreement may enter into this agreement by executing any such counterpart.

2.2            This agreement shall be governed by and construed in accordance with English law and the parties irrevocably submit to the non-exclusive jurisdiction of the English Courts to settle any claims, disputes or issues which may arise out of this agreement.

This Replacement Option Agreement has been executed and delivered as a deed on the date written above.

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EXHIBIT 4.5

[OPTION HOLDER]

and

SUPERGEN, INC.

REPLACEMENT OPTION AGREEMENT

relating to the

Astex Therapeutics Limited 2010 Share Option Scheme

THIS REPLACEMENT OPTION AGREEMENT is made on

2011

BETWEEN

(1)            [OPTION HOLDER] of [                            ] (the “Optionholder”); and

(2)            SUPERGEN, INC. whose registered office is at 4140 Dublin Boulevard, Suite 200, Dublin, CA 94568 USA (the “Acquiring Company”);

INTRODUCTION

(A)           The Optionholder is the holder of an unapproved option granted by Astex Therapeutics Limited (the “Company”) under the rules of the Astex Therapeutics Limited 2010 Share Option Scheme (the “Plan”), the details of which are set out in Schedule 1 (the “Old Option”).

(B)            The Acquiring Company has acquired all of the shares in the Company by means of a scheme of arrangement (the “Scheme”).  Pursuant to rules 10, 15 and 16 of the Plan rules, the Acquiring Company would like to grant a new replacement option (the “ New Option”) to the Optionholder.

(C)            The Optionholder released the rights under the Old Option in consideration for the grant of the New Option in a Form of Election in response to a rollover proposal made in a letter to Optionholders dated [          ] conditional upon the Scheme being effective.

AGREED TERMS

1.              Grant of New Option

1.1            The Acquiring Company grants the New Option under the terms of the Plan so that the Optionholder has an option to acquire the number of ordinary shares in the Acquiring Company at the Exercise Price as is set out in Schedule 2.

1.2            Subject to clause 1.1, the Acquiring Company and the Optionholder agree that the terms and conditions of the New Option are the same as the terms and conditions for the Old Option and that the Option Agreement for the Old Option shall be referred to for such details.

1.3            The New Option is granted and exercisable subject to the terms and conditions set out in the rules of the Plan, save that all references to the Company in the rules of the Plan shall be read and construed as references to the Acquiring Company. Exercise of the New Option shall be conditional upon the Optionholder making good any tax liability (including employer’s national insurance contributions) in relation to the New Option in accordance with rule 7 of the Plan.

1.4            The New Option may not be exercised later than the day before the tenth anniversary of the Date of Grant of the Old Option.

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2.              GENERAL PROVISIONS

2.1            This agreement may be executed in any number of counterparts all of which taken together shall constitute one and the same instrument.  Any party to this agreement may enter into this agreement by executing any such counterpart.

2.2            This agreement shall be governed by and construed in accordance with English law and the parties irrevocably submit to the non-exclusive jurisdiction of the English Courts to settle any claims, disputes or issues which may arise out of this agreement.

This Replacement Option Agreement has been executed and delivered as a deed on the date written above.

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6

EXHIBIT 4.6

ASTEX TECHNOLOGY LIMITED

ENTERPRISE MANAGEMENT INCENTIVE

(“EMI”)

S CHEME

SCHEDULE ONE

SCHEME RULES

(Adopted by the Company on 27 th  March 2002)

Ernst & Young, 1 Colmore Row, Birmingham B3 2DB

RULES OF THE ASTEX TECHNOLOGY LIMITED

ENTERPRISE MANAGEMENT INCENTIVE SCHEME

CONTENTS

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