**STOCK
        OPTION AGREEMENT**
  THIS
        STOCK OPTION AGREEMENT (“Agreement”) is made by and between LIXTE BIOTECHNOLOGY
        HOLDINGS, INC, a Delaware corporation (the “Company”), and STEPHEN
        K. CARTER (the
“Optionee”).
  WHEREAS,
        Optionee has been elected a director of the Company.
  NOW,
        THEREFORE, in consideration of the mutual benefit to be derived herefrom,
        the
        Company and Optionee agree as follows:
  1.  Grant
        of Option .
        The
        Company hereby grants to Optionee, subject to all the terms and provisions
        of
        the Stock Compensation Plan, as such Plan may be hereinafter amended, a copy
        of
        which is attached hereto and incorporated herein by this reference (the “Plan”),
        the right, privilege and option (“Option”) to purchase 200,000 shares of its
        common stock (“Stock”) at $0.33 1/3 per share, in the manner and subject to the
        conditions provided hereinafter and in the Plan and any amendments thereto
        and
        any rules and regulations thereunder.
  2.  Vesting
        and Exercise of Option .
        The
        Optionee shall be vested in 50% of the total number of shares subject to
        the
        Option on the first anniversary of the date of execution of this Agreement.
        Thereafter, the remaining shares subject to the Option shall vest in the
        Optionee and may be exercised by the Optionee on the second anniversary of
        the
        date hereof. Any exercise may be with respect to any part or all of the shares
        then vested and exercisable pursuant to such Option.
  3.  Termination
        of Option .
        Except
        as otherwise provided in this Agreement or the Plan, to the extent not
        previously exercised, the Option shall terminate upon the first to occur
        of any
        of the following events:
  a.  Five
        years from the date of the vesting of a particular tranche
        hereunder;
  b.  the
        date
        the Optionee is no longer a member of the Board of Directors of the Company.
        Any
        vested Option granted hereunder to such Optionee to expire three months after
        the date of such termination. In the event the Optionee’s termination results
        from the fact that the Optionee is “disabled,” any vested Option shall expire
        one year after the date of such termination. Any Option that has not vested
        in
        the Optionee as of the date of termination of service with the Company shall
        immediately expire and shall be null and void.
  c.  six
        months after the date of the Optionee’s death. The Option may be exercised
        (subject to the condition that no Option shall be exercisable after its
        expiration and only to the extent that the Optionee's right to exercise such
        Option was vested at the time of the Optionee's death) at any time within
        six
        months after the Optionee's death by the executors or administrators of the
        Optionee or by any person or persons who shall have acquired the Option directly
        from the Optionee by bequest or inheritance. Any Option that has not vested
        in
        the Optionee as of the date of death, shall immediately expire and shall
        be null
        and void.
  d.  the
        dissolution or liquidation of the Company; or
  
 e.  the
        breach by Optionee of any provision of the Plan or this Agreement.
  4.  Method
        of Exercise .
        An
        Option shall be exercised by written notice to the Company by the Optionee
        (or
        successor in the event of death). Such written notice shall state the number
        of
        shares with respect to which the Option is being exercised and designate
        a time,
        during normal business hours of the Company, for the delivery thereof ("Exercise
        Date"), which time shall be at least ten days after the giving of such notice
        unless an earlier date shall have been mutually agreed upon. At the time
        specified in the written notice, the Company shall deliver to the Optionee
        at
        the principal office of the Company, or such other appropriate place as may
        be
        determined by the Board, a certificate or certificates for such shares.
        Notwithstanding the foregoing, the Company may postpone delivery of any
        certificate or certificates after notice of exercise for such reasonable
        period
        as may be required to comply with any applicable listing requirements of
        any
        securities exchange. In the event an Option shall be exercisable by any person
        other than the Optionee, the required notice under this Section shall be
        accompanied by appropriate proof of the right of such person to exercise
        the
        option. The option exercise price shall be payable in full on or before the
        option Exercise Date in any one of the following alternative forms:
  a.  Full
        payment in cash or certified bank or cashier's check;
  b.  A
        full
        recourse promissory note executed by the Optionee, made payable to the Company
        bearing interest at such rate as the Board shall determine, but in no case
        less
        than the “Applicable Federal Rate” at the time the note is executed applicable
        under the Code to obligations of the same duration. The note shall contain
        such
        terms and conditions as may be determined by the Board; provided, however,
        that
        the full principal amount of the note and all unpaid interest accrued thereon
        shall be due not later than five years from the date of exercise. The Company
        may obtain from the Optionee a security interest in all shares of Stock issued
        to the Optionee under the Plan for the purpose of securing payment under
        the
        note and shall retain possession of the stock certificates representing such
        shares in order to perfect its security interest;
  c.  Full
        payment in shares of Stock or other securities of the Company having a fair
        market value on the Exercise Date in the amount equal to the option exercise
        price;
  d.  A
        combination of the consideration set forth in Sections (a), (b) and (c) hereof
        equal to the option exercise price; or
  e.  Any
        other
        method of payment including, but not limited to, the delivery by Optionee
        of an
        irrevocable direction to a securities broker approved by the Company to sell
        the
        Stock and to deliver all or part of the sales proceeds to the Company in
        payment
        of all or part of the exercise price and any withholding taxes.
  5.  Restrictions
        on Exercise and Delivery .
        The
        exercise of each Option shall be subject to the condition that, if at any
        time
        the Board shall determine, in its sole and absolute discretion,
  
 a.  the
        satisfaction of any withholding tax or other withholding liabilities, is
        necessary or desirable as a condition of, or in connection with, such exercise
        or the delivery or purchase of Stock pursuant thereto,
  b.  the
        listing, registration, or qualification of any shares deliverable upon such
        exercise is desirable or necessary, under any state or federal law, as a
        condition of, or in connection with, such exercise or the delivery or purchase
        of shares pursuant thereto, or
  c.  the
        consent or approval of any regulatory body is necessary or desirable as a
        condition of, or in connection with, such exercise or the delivery or purchase
        of shares pursuant thereto,
  then
        in
        any such event, such exercise shall not be effective unless such withholding,
        listing, registration, qualification, consent or approval shall have been
        effected or obtained free of any conditions not acceptable to the Board.
        Optionee shall execute such documents and take such other actions as are
        required by the Board to enable it to effect or obtain such withholding,
        listing, registration, qualification, consent or approval. Neither the Company
        nor any officer or member of the Board or the Committee, shall have any
        liability with respect to the non-issuance or failure to sell shares as the
        result of any suspensions of exercisability imposed pursuant to this
        Section.
  6.  Nonassignability .
        Options
        may not be sold, pledged, assigned or transferred in any manner other than
        by
        will or by the laws of intestate succession, and may be exercised during
        the
        lifetime of Optionee only by Optionee. Any transfer by Optionee of any Option
        granted under the Plan or this Agreement shall void such Option and the Company
        shall have no further obligation with respect to such Option. No Option shall
        be
        pledged or hypothecated in any way, nor shall any Option be subject to
        execution, attachment or similar process.
  7.  Restrictive
        Legends .
        Each
        certificate evidencing the shares acquired upon exercise of an Option hereunder,
        including any certificate issued to any transferee thereof, shall be imprinted
        with legends substantially in the form set forth in the Plan.
  8.  Rights
        as Shareholder .
        Neither
        Optionee nor his executor, administrator, heirs or legatees, shall be, or
        have
        any rights or privileges of a shareholder of the Company in respect of the
        Stock
        unless and until certificates representing such Stock shall have been issued
        in
        Optionee’s name.
  9.  No
        Right of Employment .
        Neither
        the grant nor exercise of any Option nor anything in the Plan or this Agreement
        shall impose upon the Company or any other corporation any obligation to
        employ
        or continue to employ any Optionee. The right of the Company and any other
        corporation to terminate any employee shall not be diminished or affected
        because an Option has been granted to such employee.
  10.  Definitions .
        Capitalized terms shall have the meaning set forth in the Plan unless otherwise
        defined herein.
  11.  Notices .
        Any
        notice to be given under the terms of this Agreement shall be addressed to
        the
        Company in care of its Secretary at its principal office, and any notice
        to be
        given to Optionee shall be addressed to such Optionee at the address maintained
        by the Company for such person or at such other address as the Optionee may
        specify in writing to the Company.
  
 12.  Binding
        Effect .
        This
        Agreement shall be binding upon and inure to the benefit of Optionee, his
        heirs
        and successors, and of the Company, its successors and assigns.
  13.  Governing
        Law .
        This
        Agreement shall be governed by the laws of the State of Delaware.
  14.  Application
        of Plan .
        The
        Company has delivered and the Optionee hereby acknowledges receipt of a copy
        of
        the Plan. The parties agree and acknowledge that the Option granted hereunder
        is
        granted pursuant to the Plan and subject to the terms and provisions thereof,
        and the rights of the Optionee are subject to modifications and termination
        in
        certain events as provided in the Plan.
  IN
        WITNESS WHEREOF, this Agreement is effective as of, and the date of grant
        shall
        be September 12, 2007.
  **LIXTE
                  BIOTECHNOLOGY HOLDINGS, INC**By:________________________________
                Name:John
                  S. Kovach
                Title:President**OPTIONEE**____________________________________
                Stephen
                  K. Carter