Document:

Exhibit 4.2

    EXHIBIT
      4.2

    
 

    Right
      to

    Purchase
      ______

    Shares
      of

    Common
      Stock,

    par
      value
      $0.001

    per
      share

     

    AMENDED
      AND RESTATED COMMON STOCK PURCHASE WARRANT A

     

    THIS
      CERTIFIES THAT, for value received, __________ or its registered
      assigns (the “Holder”), is entitled to purchase from Geron Corporation, a
      Delaware corporation (the "Company"), at any time or from time to time during
      the period specified in Paragraph 2 hereof, ____________ (_______) fully paid
      and nonassessable shares of the Company's common stock, par value $0.001 per
      share (the "Common Stock"), at a per share exercise price equal to the lesser
      of
      (i) 120% of the average of the closing bid price of the Common Stock on the
      Principal Exchange (as defined in that certain Securities Purchase Agreement,
      dated December 13, 2006, by and among the Company and the Buyers listed on
      the
      execution page thereof (the "Purchase Agreement")) for the five (5) Trading
      Day
      (as defined in the Purchase Agreement) period immediately prior to the Exercise
      Period Start Date (as defined below) and (ii) $12.14 (the "Exercise Price").
      The
      term "Warrant Shares," as used herein, refers to the shares of Common Stock
      purchasable hereunder. The Warrant Shares and the Exercise Price are subject
      to
      adjustment as provided in Paragraph 4 hereof. The term "Warrants" means this
      Warrant and the warrants (including the B Warrants and the C Warrants (each
      as
      defined in the Purchase Agreement)) issued pursuant to the Purchase Agreement.
      

     

    This
      Warrant is subject to the following terms, provisions, and
      conditions:

     

    1.  Manner
      of Exercise; Issuance of Certificates; Payment for Warrant Shares

     

    (a) 
      Subject to the provisions hereof, this Warrant may be exercised by the Holder,
      in whole or in part, by the surrender of this Warrant, together with a completed
      exercise agreement in the form attached hereto (the "Exercise Agreement"),
      to
      the Company during normal business hours on any business day at the Company's
      principal executive offices (or such other office or agency of the Company
      as it
      may designate by notice to the Holder), and upon (i) payment to the Company
      in
      cash, by certified or official bank check or by wire transfer for the account
      of
      the Company of the Exercise Price for the Warrant Shares specified in the
      Exercise Agreement or (ii) delivery to the Company of a written notice of an
      election to effect a "Cashless Exercise" (as defined in Paragraph 10(c) below)
      for the Warrant Shares specified in the Exercise Agreement (a “Conversion”). The
      Company may elect to provide that any exercise of the Warrant shall be a
      Conversion (a “Company-Elected Conversion”). The Company shall provide written
      notice of such election (a “Company Conversion Election”) by the end of the
      business day following the date of the receipt of the Exercise Agreement. The
      Warrant Shares purchased by the Holder shall be deemed to be issued to the
      Holder or such holder's designee, as the record owner of such shares, as of
      the
      close of business on the date on which this Warrant shall have been

    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

       

         
        
          	 	
                  
                    surrendered,
                      the completed Exercise Agreement shall have been delivered,
                      and payment
                      shall have been made for such shares (or an election to effect
                      a
                      Conversion or a Company Conversion Election shall have been
                      made) as set
                      forth above. In the event of any exercise of the rights represented
                      by
                      this Warrant in accordance with and subject to the terms and
                      conditions
                      hereof (whether by payment of the exercise price, Conversion
                      or
                      Company-Elected Conversion), the Warrant Shares shall be issued
                      and
                      delivered to the Depository Trust Company account on the Holder’s behalf
                      via the Deposit Withdrawal Agent Commission system ("DWAC Transfer")
                      within a reasonable time, not exceeding two (2) trading days
                      after such
                      exercise (or, if DWAC Transfer is not available or Holder requests
                      in
                      writing otherwise, certificates for the Warrant Shares shall
                      be issued,
                      dated the date of such exercise and delivered to the Holder
                      hereof within
                      a reasonable time, not exceeding three (3) trading days after
                      such
                      exercise), and the Holder hereof shall be deemed for all purposes
                      to be
                      the holder of the Warrant Shares so purchased as of the date
                      of such
                      exercise. If the Warrant Shares are issued pursuant to a Company-Elected
                      Conversion, the number of Warrant Shares to be issued within
                      the time
                      period specified in the preceding sentence shall equal the
                      number of
                      Warrant Shares to be delivered if such Cashless Exercise was
                      made at the
                      Holder’s election (the “Estimated Warrant Shares”); provided,
                      however, that within three (3) trading days after the number of
                      Warrant Shares to be issued pursuant to Paragraph 10(c) is
                      able to be
                      calculated (i) if the number of Estimated Warrant Shares exceeds
                      the
                      number of Warrant Shares to be delivered pursuant to Paragraph
                      10(c)
                      hereof, Holder shall return to the Company the number of Warrant
                      Shares
                      which exceed the number of Warrant Shares to which Holder is
                      entitled
                      pursuant to Paragraph 10(c); and (ii) if the Estimated Warrant
                      Shares are
                      less than the number of Warrant Shares to be delivered pursuant
                      to
                      Paragraph 10(c) hereof, the Company shall issue to Holder the
                      number of
                      Warrant Shares equal to the difference between the Estimated
                      Warrant
                      Shares and the Warrant Shares to be delivered pursuant to Paragraph
                      10(c).
                      Any certificates requested shall be delivered in such denominations
                      as may
                      be requested by the Holder and shall be registered in the name
                      of the
                      Holder or such other name as shall be designated by the Holder.
                      If this
                      Warrant shall have been exercised only in part, then, unless
                      this Warrant
                      has expired, the Company shall, at its expense, at the time
                      of delivery of
                      such certificates, deliver to the Holder a new Warrant representing
                      the
                      number of shares with respect to which this Warrant shall not
                      then have
                      been exercised. In the event an Exercise Agreement is delivered
                      and the
                      Company is unable to issue the Warrant Shares, the Holder may,
                      at its
                      option, rescind such Exercise Agreement and such rescission
                      will not
                      effect the Holder's right to an extension of the Exercise Period
                      pursuant
                      to Section 4.13 of the Purchase Agreement. In any event, if
                      the Company is
                      unable to issue the Warrant Shares via DWAC transfer (or otherwise
                      without
                      restrictive legend), because (i) the Securities and Exchange
                      Commission
                      (the “Commission”) has issued a stop order with respect to the
                      registration statement relating to the Shares (the “Registration
                      Statement”), (ii) the Commission otherwise has suspended or withdrawn
                      the
                      effectiveness of the Registration Statement, either temporarily
                      or
                      permanently, (iii) the Company has suspended or withdrawn the
                      effectiveness of the Registration Statement, either temporarily
                      or
                      permanently, (iv) no exemption from the registration requirements
                      is
                      otherwise available (including, without limitation, under Section
                      3(a)(9)
                      of the Act by  virtue of a Conversion or Company-Elected
                      Conversion) or (v) otherwise, the Company shall not be required to
                      make any cash payments to the Holder in lieu of issuance of
                      the Warrant
                      Shares. Further, subject to Section 4.13 of the Purchase Agreement,
                      the
                      Warrant shall not be exercisable if (i) the Registration Statement
                      is not
                      effective at the time of exercise or (ii) an exemption from
                      the
                      registration requirements of the Securities Act, as amended
                      (the "Act"),
                      is not available; provided, however, that for purposes of Section
                      4.13 of
                      the Purchase Agreement and the extension of the Exercise Period
                      pursuant
                      thereto, (x) the Company will have been deemed unable to issue
                      Warrant
                      Shares without restrictive legend and (y) the Warrant shall
                      be deemed to
                      have been exercised, if at the time the Holder attempts to
                      deliver an
                      Exercise Agreement, (1) the Registration Statement is not effective
                      and
                      (2) no exemption from the registration requirements of the
                      Act is
                      available (including, without limitation, under Section 3(a)(9)
                      of the Act
                      by virtue of a Conversion or Company-Elected
                      Conversion).

                  

                

        
             

      
        
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    (b)  Notwithstanding
      anything in this Warrant to the contrary, in no event shall the Holder be
      entitled to exercise a number of Warrants (or portions thereof) in excess of
      the
      number of Warrants (or portions thereof) upon exercise of which the sum of
      (i)
      the number of shares of Common Stock beneficially owned by the Holder and its
      affiliates (other than shares of Common Stock which, but for this proviso,
      may
      be deemed beneficially owned through the ownership of the unexercised Warrants
      and the unexercised or unconverted portion of any other securities of the
      Company subject to a limitation on conversion or exercise analogous to the
      limitation contained herein) and (ii) the number of shares of Common Stock
      issuable upon exercise of the Warrants (or portions thereof) with respect to
      which the determination described herein is being made, would result in
      beneficial ownership by the Holder and its affiliates of more than 4.9% of
      the
      outstanding shares of Common Stock. For purposes of the immediately preceding
      sentence, beneficial ownership shall be determined in accordance with Section
      13(d) of the Securities Exchange Act of 1934, as amended, and Regulations 13D-G
      thereunder, except as otherwise provided in this paragraph (b). Notwithstanding
      anything in this Warrant to the contrary, the restrictions on exercise of this
      Warrant set forth in this paragraph shall not be amended without (i) the written
      consent of the Holder and the Company and (ii) the approval of the holders
      of a
      majority of the Common Stock present, or represented by proxy, and voting at
      any
      meeting called to vote on the amendment of such restriction. 

     

    2.  Period
      of Exercise. This Warrant is exercisable at any
      time or from time to time on or after the earlier of (i) June 13, 2007 and
      (ii)
      immediately prior to the closing of a Fundamental Transaction (as defined below)
      (“Exercise Period Start Date”), and before 5:00 p.m., New York City time on
      December 15, 2010 (the "Exercise Period"); provided, however, that the Exercise
      Period may be extended pursuant to Section 4.13 of the Purchase
      Agreement.

     

    3.  Certain
      Agreements of the Company. The Company hereby
      covenants and agrees as follows:

     

    (a)  Shares
      to be Fully Paid. All Warrant Shares will, upon
      issuance in accordance with the terms of this Warrant, be validly issued, fully
      paid, and nonassessable and free from all taxes, liens, and charges with respect
      to the issue thereof.

     

    
      
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    (b)  Reservation
      of Shares. During the Exercise Period, the Company
      shall at all times have authorized, and reserved for the purpose of issuance
      upon exercise of this Warrant, a sufficient number of shares of Common Stock
      to
      provide for the full exercise of this Warrant.

     

    (c)  Listing.
      The Company shall promptly secure the listing of the Warrant Shares upon each
      national securities exchange or automated quotation system, if any, upon which
      shares of Common Stock are then listed (subject to official notice of issuance
      upon exercise of this Warrant) and shall maintain, so long as any other shares
      of Common Stock shall be so listed, such listing of all Warrant Shares; and
      the
      Company shall so list on each national securities exchange or automated
      quotation system, as the case may be, and shall maintain such listing of, any
      other shares of capital stock of the Company issuable upon the exercise of
      this
      Warrant if and so long as any shares of the same class shall be listed on such
      national securities exchange or automated quotation system.

     

    (d)  Certain
      Actions Prohibited. The Company will not, by
      amendment of its charter or through any reorganization, transfer of assets,
      consolidation, merger, dissolution, issue or sale of securities, or any other
      voluntary action, avoid or seek to avoid the observance or performance of any
      of
      the terms to be observed or performed by it hereunder, but will at all times
      in
      good faith assist in the carrying out of all the provisions of this Warrant
      and
      in the taking of all such action as may reasonably be requested by the Holder
      in
      order to protect the exercise privilege of the Holder against dilution or other
      impairment, consistent with the tenor and purpose of this Warrant. Without
      limiting the generality of the foregoing, the Company (i) will not increase
      the
      par value of any shares of Common Stock receivable upon the exercise of this
      Warrant above the Exercise Price then in effect, and (ii) will take all such
      actions as may be necessary or appropriate in order that the Company may validly
      and legally issue fully paid and nonassessable shares of Common Stock upon
      the
      exercise of this Warrant. 

     

    (e)  Successors
      and Assigns. This Warrant will be binding upon any
      entity succeeding to the Company by merger, consolidation, or acquisition of
      all
      or substantially all the Company's assets. 

     

    4.  Antidilution
      Provisions. During the Exercise Period, the
      Exercise Price and the number of Warrant Shares shall be subject to adjustment
      from time to time as provided in this Paragraph 4. In the event that any
      adjustment of the Exercise Price as required herein results in a fraction of
      a
      cent, such Exercise Price shall be rounded up to the nearest cent.

     

    (a)  Subdivision
      or Combination of Common Stock. If the Company at
      any time subdivides (by any stock split, stock dividend, recapitalization,
      reorganization, reclassification or otherwise) the shares of Common Stock
      acquirable hereunder into a greater number of shares, then, after the date
      of
      record for effecting such subdivision, the Exercise Price in effect immediately
      prior to such subdivision will be proportionately reduced. If the Company at
      any
      time combines (by reverse stock split, recapitalization, reorganization,
      reclassification or otherwise) the shares of Common Stock acquirable hereunder
      into a smaller number of shares, then, after the date of record for effecting
      such combination, the Exercise Price in effect immediately prior to such
      combination  will
      be proportionately increased. "Common Stock," for purposes of this Paragraph
      4,
      includes the Common Stock, par value $0.001 per share, and any additional class
      of stock
      of
      the Company having no preference as to dividends or distributions on
      liquidation, provided that the shares purchasable pursuant to this Warrant
      shall
      include only
      shares of Common Stock, par value $0.001 per share, in respect of which this
      Warrant is exercisable, or shares resulting from any subdivision or combination
      of such  Common
      Stock, or in the case of any reorganization, reclassification, consolidation,
      merger, or sale of the character referred to in Paragraph 4(c) hereof, the
      stock
      or other securities
      or property provided for in such Paragraph.

     

    
      
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    (b)  Adjustment
      in Number of Shares. Upon each adjustment of the
      Exercise Price pursuant to the provisions of this Paragraph 4, the number of
      shares of Common Stock issuable upon exercise of this Warrant shall be adjusted
      by multiplying a number equal to the Exercise Price in effect immediately prior
      to such adjustment by the number of shares of Common Stock issuable upon
      exercise of this Warrant immediately prior to such adjustment and dividing
      the
      product so obtained by the adjusted Exercise Price.

     

    (c)  Consolidation,
      Merger or Sale. In case of (i) any consolidation
      of the Company with, or merger of the Company into any other corporation or
      entity, or (ii) any sale or conveyance of all or substantially all of the assets
      of the Company other than in connection with a plan of complete liquidation
      of
      the Company (each of clause (i) and (ii) shall be referred to as a “Fundamental
      Transaction”), then as a condition of such Fundamental Transaction, adequate
      provision will be made whereby the Holder will thereafter (at any time or from
      time to time during the remainder of the Exercise Period) have the right to
      acquire and receive upon exercise of this Warrant in lieu of the shares of
      Common Stock immediately theretofor acquirable upon the exercise of this
      Warrant, such shares of stock, securities or assets as may be issued or payable
      with respect to or in exchange for the number of shares of Common Stock
      immediately theretofore acquirable and receivable upon exercise of this Warrant
      had such Fundamental Transaction not taken place.

     

    In
      any
      such case, the Company will make appropriate provision to insure that the
      provisions of this Paragraph 4 hereof will thereafter be applicable as nearly
      as
      may be in relation to any shares of stock or securities thereafter deliverable
      upon the exercise of this Warrant. The Company will not effect any Fundamental
      Transaction unless, prior to the consummation thereof, (i) the successor or
      acquiring entity (if other than the Company), (ii) any other entity whose stock,
      securities or assets the holders of the Common Stock of the Company are entitled
      to receive as a result of such Fundamental Transaction, and (iii) any parent,
      subsidiary or affiliate of such successor, acquiring entity or other entity
      whose common stock this Warrant shall be exercisable into by virtue of the
      penultimate paragraph of this Paragraph 4(c) (any or all of such entities being
      hereafter referred to as a “Successor Entity”) assumes by written instrument the
      obligations under this Paragraph 4 and the obligations to deliver to the Holder
      such shares of stock, securities or assets as, in accordance with the foregoing
      provisions, the Holder may be entitled to acquire.

     

    
      
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    Furthermore,
      in the event of a transaction contemplated by this Paragraph 4(c) involving
      the
      acquisition of the Company by a Public Acquirer (as defined below) for
      consideration consisting of all or part cash, at the option of the Holder,
      in
      lieu of any cash in respect of shares of Common Stock underlying this Warrant,
      this Warrant (or such proportion thereof as is equal to the proportion of cash
      to stock to be paid for the Company) shall thereafter be exercisable for the
      common stock of the Public Acquirer for the remainder of the Exercise Period
      (and otherwise in accordance with the terms hereof), with the number of shares
      thereafter underlying this Warrant determined by multiplying the number of
      shares for which this Warrant is exercisable immediately prior to such
      transaction by a fraction, the numerator of which is the cash consideration
      per
      share paid for the Company and the denominator of which is the Market Price
      of
      the Public Acquirer’s common stock, where “Market Price” means the average
      closing price of the Public Acquirer’s common stock over the five trading days
      immediately following the closing date of the transaction. In the case of a
      transaction involving partial cash consideration, the proportion of this Warrant
      as is equal to the proportion of stock to cash in such transaction shall
      thereafter be exercisable for stock of the Public Acquirer in accordance with
      the preceding terms of this Paragraph 4(c), with the number of shares underlying
      this Warrant adjusted to reflect the number of shares of common stock of the
      Public Acquirer to be issued for each share of Common Stock of the Company.
      Following any adjustment hereunder, the Exercise Price shall be proportionately
      adjusted, by multiplying the Exercise Price then in effect by a fraction, the
      numerator of which is the number of shares issuable prior to the adjustment
      and
      the denominator of which is the number of shares issuable after the adjustment.
      “Public Acquirer” means any entity that has publicly traded common stock whether
      publicly traded in the United States or in any other jurisdiction, it being
      understood that (1) “common stock” as used in this Paragraph 4(c) includes
      common equity equivalents, trust shares, limited partnership interests, ordinary
      shares, American Depositary Receipts, American Depositary Shares, and any other
      similar securities or derivate thereof, and (2) the Company shall be deemed
      to
      have been acquired by a Public Acquirer where any Successor Entity has publicly
      traded common stock whether traded in the United States or any other
      jurisdiction, even if such Successor Entity is not the direct acquirer or
      successor to the Company. Following any transaction contemplated by this
      Paragraph 4(c) the term Warrant Shares shall be deemed to refer to the
shares
      for which this Warrant is thereafter exercisable in accordance with the
      provisions hereof.

     

    In
      addition, if holders of Common Stock are given a choice as to the securities,
      cash (which shall be treated in accordance with the preceding paragraph) or
      property to be received in a Fundamental Transaction (including a right to
      elect
      to receive any particular one or combination of more than one of the foregoing),
      then the Holder shall be given the same choice of consideration upon any
      exercise of this Warrant following such Fundamental Transaction, which choice
      of
      consideration can be made at the time of exercise at any time prior to the
      expiration of the Exercise Period.

     

    
      
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    (d)  Distribution
      of Assets. In case the Company shall declare or
      make any distribution of its assets (including cash) to holders of Common Stock
      as a partial liquidating dividend, by way of return of capital or otherwise,
      then, after the date of record for determining stockholders entitled to such
      distribution, but prior to the date of distribution, the Holder shall be
      entitled upon exercise of this Warrant for the purchase of any or all of the
      shares of Common Stock subject hereto, to receive the amount of such assets
      which would have been payable to the holder had such holder been the holder
      of
      such shares of Common Stock on the record date for the determination of
      stockholders entitled to such distribution.

     

    (e)  Notice
      of Adjustment. Upon the occurrence of any event
      which requires any adjustment of the Exercise Price, then, and in each such
      case, the Company shall give notice thereof to the Holder, which notice shall
      state the Exercise Price resulting from such adjustment and the increase or
      decrease in the number of Warrant Shares purchasable at such price upon
      exercise, setting forth in reasonable detail the method of calculation and
      the
      facts upon which such calculation is based. Such calculation shall be certified
      by the chief financial officer of the Company.

     

    (f)  Minimum
      Adjustment of Exercise Price. No adjustment of the
      Exercise Price shall be made in an amount of less than 1% of the Exercise Price
      in effect at the time such adjustment is otherwise required to be made, but
      any
      such lesser adjustment shall be carried forward and shall be made at the time
      and together with the next subsequent adjustment which, together with any
      adjustments so carried forward, shall amount to not less than 1% of such
      Exercise Price.

     

    (g)  No
      Fractional Shares. No fractional shares of Common
      Stock are to be issued upon the exercise of this Warrant. If the exercise of
      this Warrant would result in a fractional share of Common Stock, such fractional
      share shall be disregarded and the number of shares of Common Stock issuable
      upon exercise of the Warrant shall be the next higher number of shares.

     

    (h)  Other
      Notices. In case at any time:

     

    (i)  the
      Company shall declare any dividend upon the Common Stock payable in shares
      of
      stock of any class or make any other distribution (including dividends or
      distributions payable in cash out of retained earnings) to the holders of the
      Common Stock;

     

    (ii)  the
      Company shall offer for subscription pro rata to the holders of the Common
      Stock
      any additional shares of stock of any class or other rights;

     

    (iii)  there
      shall be any capital reorganization of the Company, or reclassification of
      the
      Common Stock, or consolidation or merger of the Company with or into, or sale
      of
      all or substantially all its assets to, another corporation or entity;
      or

     

    
      
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      (iv)  there shall be a voluntary or involuntary dissolution,
      liquidation or winding-up of the Company;

     

    then,
      in
      each such case, the Company shall give to the Holder (a) notice of the date
      on
      which the books of the Company shall close or a record shall be taken for
      determining the holders of Common Stock entitled to receive any such dividend,
      distribution, or subscription rights or for determining the holders of Common
      Stock entitled to vote in respect of any such reorganization, reclassification,
      consolidation, merger, sale, dissolution, liquidation or winding-up and (b)
      in
      the case of any such reorganization, reclassification, consolidation, merger,
      sale, dissolution, liquidation or winding-up, notice of the date (or, if not
      then known, a reasonable approximation thereof by the Company) when the same
      shall take place. Such notice shall also specify the date on which the holders
      of Common Stock shall be entitled to receive such dividend, distribution, or
      subscription rights or to exchange their Common Stock for stock or other
      securities or property deliverable upon such reorganization, reclassification,
      consolidation, merger, sale, dissolution, liquidation, or winding-up, as the
      case may be. Such notice shall be given at least 15 days prior to the record
      date or the date on which the Company's books are closed in respect thereto.
      Failure to give any such notice or any defect therein shall not affect the
      validity of the proceedings referred to in clauses (i), (ii), (iii) and (iv)
      above.

     

    (i)  Certain
      Events. If any event occurs of the type
      contemplated by the adjustment provisions of this Paragraph 4 but not expressly
      provided for by such provisions, the Company will give notice of such event
      as
      provided in Paragraph 4(e) hereof, and the Company's Board of Directors will
      make an appropriate adjustment in the Exercise Price and the number of shares
      of
      Common Stock acquirable upon exercise of this Warrant so that the rights of
      the
      Holder shall be neither enhanced nor diminished by such event.

     

    (j)  Withholding
      Taxes. In the event that an adjustment to the
      Exercise Price (or a failure to adjust the Exercise Price) results in a
      constructive distribution to the Holder of the Warrants under Section 305 of
      the
      Internal Revenue Code of 1986, as amended, the Company may withhold, to the
      extent required by applicable law, any applicable United States federal
      withholding tax from any subsequent distributions of cash or property made
      to
      the Holder, including any Common Stock issued by the Company upon the exercise
      of this Warrant. 

     

    5.  Issue
      Tax. The issuance of certificates for Warrant
      Shares upon the exercise of this Warrant shall be made without charge to the
      Holder or such shares for any issuance tax or other costs in respect thereof,
      provided that the Company shall not be required to pay any tax which may be
      payable in respect of any transfer involved in the issuance and delivery of
      any
      certificate in a name other than the Holder.

     

    6.  No
      Rights or Liabilities as a Stockholder. This
      Warrant shall not entitle the Holder to any voting rights or other rights as
      a
      stockholder of the Company. No provision of this Warrant, in the absence of
      affirmative action by the Holder to purchase Warrant Shares, and no mere
      enumeration herein of the rights or privileges of the Holder, shall give rise
      to
      any liability of such holder for the Exercise Price or as a stockholder of
      the
      Company, whether such liability is asserted by the Company or by creditors
      of
      the Company.

     

    
      
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    7.  Transfer,
      Exchange, and Replacement of Warrant.

     

    (a)  Transfer.
      This Warrant and the rights granted to the Holder are transferable, in whole
      or
      in part, upon surrender of this Warrant, together with a properly executed
      assignment in the form attached hereto, at the office or agency of the Company
      referred to in Paragraph 7(e) below. Until due presentment for registration
      of
      transfer on the books of the Company, the Company may treat the registered
      Holder as the owner and Holder for all purposes, and the Company shall not
      be
      affected by any notice to the contrary. 

     

    (b)  Warrant
      Exchangeable for Different Denominations. This
      Warrant is exchangeable, upon the surrender hereof by the Holder at the office
      or agency of the Company referred to in Paragraph 7(e) below, for new Warrants
      of like tenor representing in the aggregate the right to purchase the number
      of
      shares of Common Stock which may be purchased hereunder, each of such new
      Warrants to represent the right to purchase such number of shares as shall
      be
      designated by the Holder at the time of such surrender.

     

    (c)  Replacement
      of Warrant. Upon receipt of evidence reasonably
      satisfactory to the Company of the loss, theft, destruction, or mutilation
      of
      this Warrant and, in the case of any such loss, theft, or destruction, upon
      delivery of an indemnity agreement reasonably satisfactory in form and amount
      to
      the Company, or, in the case of any such mutilation, upon surrender and
      cancellation of this Warrant, the Company, at its expense, will execute and
      deliver, in lieu thereof, a new Warrant of like tenor.

     

    (d)  Cancellation;
      Payment of Expenses. Upon the surrender of this
      Warrant in connection with any transfer, exchange, or replacement as provided
      in
      this Paragraph 7, this Warrant shall be promptly canceled by the Company. The
      Company shall pay all taxes (other than securities transfer taxes) and all
      other
      expenses (other than legal expenses, if any, incurred by the Holder or
      transferees) and charges payable in connection with the preparation, execution,
      and delivery of Warrants pursuant to this Paragraph 7.

     

    (e)  Register.
      The Company shall maintain, at its principal executive offices (or such other
      office or agency of the Company as it may designate by notice to the Holder),
      a
      register for this Warrant, in which the Company shall record the name and
      address of the person in whose name this Warrant has been issued, as well as
      the
      name and address of each transferee and each prior owner of this Warrant.

     

    8.  Notices.
      All notices, requests, and other communications required or permitted to be
      given or delivered hereunder to the Holder shall be in writing, and shall be
      personally delivered, or shall be sent by certified or registered mail or by
      recognized overnight mail courier, postage prepaid and addressed, to such holder
      at the address shown for such holder on the books of the Company, or at such
      other address as shall have been furnished to the Company by notice from such
      Holder. All
      notices, requests, and other communications required or permitted to be given
      or
      delivered hereunder to the Company shall be in writing, and shall be personally
      delivered,  or
      shall
      be sent by certified or
      registered mail or by recognized overnight mail courier, postage prepaid and
      addressed, to the office of the Company at 230 Constitution Drive, Menlo
      Park, California 94025, Attn: David Greenwood, fax no. (650) 473-7701 with
      copies to Latham & Watkins LLP, 140 Scott Drive, Menlo Park, California
      94025, Attn: Alan C. Mendelson,
      Esq., fax no. (650) 463-2600, or at such other address as shall have been
      furnished to the Holder by notice from the Company. Any such notice, request,
      or
      other communication
      may be sent by facsimile, but shall in such case be subsequently confirmed
      by a
      writing personally delivered or sent by certified or registered mail or by
      recognized
      overnight mail courier as provided above. All notices, requests, and other
      communications shall be deemed to have been given either at the time of the
      receipt thereof
      by the person entitled to receive such notice at the address of such person
      for
      purposes of this Paragraph 8, or, if mailed by registered or certified mail
      or
      with a recognized
      overnight mail courier upon deposit with the United States Post Office or such
      overnight mail courier, if postage is prepaid and the mailing is properly
      addressed, as the
      case
      may be.

     

    
      
        9

      

      
        
        

        
          

        

      

      
        
        

      

    

     

     

    9.  Governing
      Law. THIS WARRANT SHALL BE GOVERNED BY AND
      CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE APPLICABLE TO
      AGREEMENTS MADE AND TO BE PERFORMED IN THE STATE OF DELAWARE (WITHOUT REGARD
      TO
      PRINCIPLES OF CONFLICT OF LAWS). BOTH PARTIES IRREVOCABLY CONSENT TO THE
      EXCLUSIVE JURISDICTION OF THE UNITED STATES FEDERAL COURTS AND THE STATE COURTS
      LOCATED IN DELAWARE WITH RESPECT TO ANY SUIT OR PROCEEDING BASED ON OR ARISING
      UNDER THIS AGREEMENT, THE AGREEMENTS ENTERED INTO IN CONNECTION HEREWITH OR
      THE
      TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY AND IRREVOCABLY AGREE THAT ALL
      CLAIMS IN RESPECT OF SUCH SUIT OR PROCEEDING MAY BE DETERMINED IN SUCH COURTS.
      BOTH PARTIES IRREVOCABLY WAIVE THE DEFENSE OF AN INCONVENIENT FORUM TO THE
      MAINTENANCE OF SUCH SUIT OR PROCEEDING. BOTH PARTIES FURTHER AGREE THAT SERVICE
      OF PROCESS UPON A PARTY MAILED BY FIRST CLASS MAIL SHALL BE DEEMED IN EVERY
      RESPECT EFFECTIVE SERVICE OF PROCESS UPON THE PARTY IN ANY SUCH SUIT OR
      PROCEEDING. NOTHING HEREIN SHALL AFFECT EITHER PARTY'S RIGHT TO SERVE PROCESS
      IN
      ANY OTHER MANNER PERMITTED BY LAW. BOTH PARTIES AGREE THAT A FINAL
      NON-APPEALABLE JUDGMENT IN ANY SUCH SUIT OR PROCEEDING SHALL BE CONCLUSIVE
      AND
      MAY BE ENFORCED IN OTHER JURISDICTIONS BY SUIT ON SUCH JUDGMENT OR IN ANY OTHER
      LAWFUL MANNER. 

     

    10.  Miscellaneous.

     

    (a)  Amendments.
      This Warrant and any provision hereof may only be amended by an instrument
      in
      writing signed by the Company and the Holder.

     

    (b)  Descriptive
      Headings. The descriptive headings of the several
      paragraphs of this Warrant are inserted for purposes of reference only, and
      shall not affect the meaning or construction of any of the provisions
      hereof.

     

    
      
        10

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    (c)  Cashless
      Exercise. This Warrant may be exercised by presentation and
      surrender of this Warrant to the Company at its principal executive offices
      with
      a written notice of the holder's intention to effect a cashless exercise,
      including a calculation of the number of shares of Common Stock to be issued
      upon such exercise in accordance with the terms hereof, or in connection with
      a
      Company-Elected Conversion (a "Cashless Exercise"). In the event of a Cashless
      Exercise, the Holder shall be entitled to receive a certificate for the number
      of Warrant Shares equal to the quotient obtained by dividing [(A-B) (X)] by
      (A),
      where:

     

    

    (A)
      = the
      closing price on the trading day immediately preceding the date of such
      election; provided, however, that if the Cashless Exercise is in
      connection with a Company-Elected Conversion, “A” in the formula above shall
      equal the volume-weighted average price of the Company’s common stock as
      reported by Bloomberg L.P., or any successor performing similar functions for
      the five (5) trading days beginning the day immediately following the date
      of
      the Company-Elected Conversion.

    

    (B)
      = the
      Exercise Price of this Warrant, as adjusted; and

    

    (X)
      = the
      number of Warrant Shares issuable upon exercise of this Warrant in accordance
      with the terms of this Warrant by means of a cash exercise rather than a
      cashless exercise.

     

    (d)  Remedies.
      The Company acknowledges that a breach by it of its obligations hereunder will
      cause irreparable harm to the Holder by vitiating the intent and purpose of
      the
      transactions contemplated hereby. Accordingly, the Company acknowledges that
      the
      remedy at law for a breach of its obligations under this Warrant will be
      inadequate and agrees, in the event of a breach or threatened breach by the
      Company of the provisions of this Warrant, that the Holder shall be entitled,
      in
      addition to all other available remedies in law or in equity, to an injunction
      or injunctions to prevent or cure any breaches of the provisions of this
      Agreement and to enforce specifically the terms and provisions of this Warrant,
      without the necessity of showing economic loss and without any bond or other
      security being required.

     

    [REMAINDER
      OF THIS PAGE INTENTIONALLY LEFT BLANK]

    
      
        11

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    EXHIBIT
      4.2

     

    IN
      WITNESS WHEREOF, the Company has caused this Warrant to be signed by
      its duly authorized officer.

     

    
      	 	 	 
	 	GERON
              CORPORATION
	 
 	 
 	 
 
	 	By:  	 
	 	
              
                

              

              Name: 
                David L. Greenwood

            
	 	
              Title:    Executive Vice President
                and 

                  
Chief
                Financial Officer

            
	 	 
	 	 
	 	Dated as of March 13,
              2007

    

                                                                                                                                      
      

    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

    

    FORM
      OF EXERCISE AGREEMENT

     

    Dated:
      ________ __, 200_

     

    To:
      GERON
      CORPORATION

     

    The
      undersigned, pursuant to the provisions set forth in the Warrant attached
      hereto, hereby agrees to purchase ________ shares of Common Stock covered by
      such Warrant, and makes payment herewith in full therefor at the price per
      share
      provided by such Warrant in cash or by certified or official bank check in
      the
      amount of, or by surrender of securities issued by the Company (including a
      portion of the Warrant) having a market value (in the case of a portion of
      this
      Warrant, determined in accordance with Paragraph 10(c) of the Warrant) equal
      to
      $_________. Please issue a certificate or certificates for such shares of Common
      Stock in the name of and pay any cash for any fractional share to:

    
       

      

        
          	 	
                  Name:
                    

                
	 	
                  Signature:
                    

                
	 	
                  Address:

                
	 	
                
	 	 
	 	 
	 	
                  Note:
                    The
                    above signature should correspond exactly with the name on the
                    face of the
                    Warrant attached hereto.

                

        

      

       

      and,
        if
        said number of shares of Common Stock shall not be all the shares purchasable
        under the Warrant attached hereto, a new Warrant is to be issued in the name
        of
        said undersigned covering the balance of the shares purchasable thereunder
        less
        any fraction of a share paid in cash.

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      FORM
        OF ASSIGNMENT

       

      FOR
        VALUE
        RECEIVED, the undersigned hereby sells, assigns, and transfers all the rights
        of
        the undersigned under the Warrant attached hereto, with respect to the number
        of
        shares of Common Stock covered thereby set forth hereinbelow, to:

      

        
          	
                  Name
                    of Assignee

                	
                  Address

                	
                  No
                    of Shares

                
	 	 	 
	 	 	 

        

      

       

       
        ,
        and
        hereby irrevocably constitutes and appoints
        _____________________________________ as agent and attorney-in-fact to transfer
        said Warrant on the books of the within-named corporation, with full power
        of
        substitution in the premises.

       

      

        
          	
                  Dated:
                    ________ __, 200_

                
	
                  In
                    the presence of:

                
	
                  _________________________

                

        

      

       

      
        
          	 	
                  Name:
                    

                
	 	
                  Signature:

                
	 	Title
                  of Signing Officer or Agent (if any):
	 	
                  Address:

                
	 	
                
	 	 
	 	 
	 	
                  Note:
                    The
                    above signature should correspond exactly with the name on the
                    face of the
                    Warrant attached
                    hereto.Exhibit 4.3

    EXHIBIT
      4.3

     

     

    Right
      to

    Purchase
      ________

    Shares
      of

    Common
      Stock,

    par
      value
      $0.001

    per
      share

     

    AMENDED
      AND RESTATED COMMON STOCK PURCHASE WARRANT C

     

    THIS
      CERTIFIES THAT, for value received, __________ or its registered
      assigns (the “Holder”), is entitled to purchase from Geron Corporation, a
      Delaware corporation (the "Company"), at any time or from time to time during
      the period specified in Paragraph 2 hereof, ____________ (_______) fully
      paid and nonassessable shares of the Company's common stock, par value $0.001
      per share (the "Common Stock"), at an exercise price of $0.01 per share (the
      "Exercise Price"). The term "Warrant Shares," as used herein, refers to the
      shares of Common Stock purchasable hereunder. The Warrant Shares are subject
      to
      adjustment as provided in Paragraph 4 hereof. The term "Warrants" means
      this Warrant and the other warrants (including the A Warrants and the B
      Warrants (each as defined in the Purchase Agreement)) issued pursuant to that
      certain Securities Purchase Agreement, dated December 13, 2006, by and among
      the
      Company and the Buyers listed on the execution page thereof (the "Purchase
      Agreement").

     

    This
      Warrant is subject to the following terms, provisions, and
      conditions:

     

    1.  Manner
      of Exercise; Issuance of Certificates; Payment for Warrant Shares

     

    (a)  Subject
      to the provisions hereof, this Warrant may be exercised by the Holder, in whole
      or in part, by the surrender of this Warrant, together with a completed exercise
      agreement in the form attached hereto (the "Exercise Agreement"), to the Company
      during normal business hours on any business day at the Company's principal
      executive offices (or such other office or agency of the Company as it may
      designate by notice to the Holder), and upon (i) payment to the Company in
      cash,
      by certified or official bank check or by wire transfer for the account of
      the
      Company of the Exercise Price for the Warrant Shares specified in the Exercise
      Agreement or (ii) delivery to the Company of a written notice of an election
      to
      effect a "Cashless Exercise" (as defined in Paragraph 10(c) below) for the
      Warrant Shares specified in the Exercise Agreement (a “Conversion”). The Company
      may elect to provide that any exercise of the Warrant shall be a Conversion
      (a
“Company-Elected Conversion”). The Company shall provide written notice of such
      election (a “Company Conversion Election”) by the end of the business day
      following the date of the receipt of the Exercise Agreement. The Warrant Shares
      purchased by the Holder shall be deemed to be issued to the Holder or such
      holder's designee, as the record owner of such shares, as of the close of
      business on the date on which this Warrant shall have been surrendered, the
      completed Exercise Agreement shall have been delivered, and payment shall have
      been made for such shares (or an election to effect a Conversion or a Company
      Conversion Election shall have been made) as set forth above. In the event
      of
      any exercise of the rights represented by this Warrant in accordance with
      and 

     

    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

       

      
        	 	
                
                  subject
                    to the terms and conditions hereof (whether by payment of the
                    exercise
                    price, Conversion or Company-Elected Conversion), the Warrant
                    Shares shall
                    be issued and delivered to the Depository Trust Company account
                    on the
                    Holder’s behalf via the Deposit Withdrawal Agent Commission system ("DWAC
                    Transfer") within a reasonable time, not exceeding two (2) trading
                    days
                    after such exercise (or, if DWAC Transfer is not available or
                    Holder
                    requests in writing otherwise, certificates for the Warrant Shares
                    shall
                    be issued, dated the date of such exercise and delivered to the
                    Holder
                    hereof within a reasonable time, not exceeding three (3) trading
                    days
                    after such exercise), and the Holder hereof shall be deemed for
                    all
                    purposes to be the holder of the Warrant Shares so purchased
                    as of the
                    date of such exercise. If the Warrant Shares are issued pursuant
                    to a
                    Company-Elected Conversion, the number of Warrant Shares to be
                    issued
                    within the time period specified in the preceding sentence shall
                    equal the
                    number of Warrant Shares to be delivered if such Cashless Exercise
                    was
                    made at the Holder’s election (the “Estimated Warrant Shares”);
                    provided, however, that within three (3) trading days after the
                    number of Warrant Shares to be issued pursuant to Paragraph 10(c)
                    is able
                    to be calculated (i) if the number of Estimated Warrant Shares
                    exceeds the
                    number of Warrant Shares to be delivered pursuant to Paragraph
                    10(c)
                    hereof, Holder shall return to the Company the number of Warrant
                    Shares
                    which exceed the number of Warrant Shares to which Holder is
                    entitled
                    pursuant to Paragraph 10(c); and (ii) if the Estimated Warrant
                    Shares are
                    less than the number of Warrant Shares to be delivered pursuant
                    to
                    Paragraph 10(c) hereof, the Company shall issue to Holder the
                    number of
                    Warrant Shares equal to the difference between the Estimated
                    Warrant
                    Shares and the Warrant Shares to be delivered pursuant to Paragraph
                    10(c).
                    Any certificates requested shall be delivered in such denominations
                    as may
                    be requested by the Holder and shall be registered in the name
                    of the
                    Holder or such other name as shall be designated by the Holder.
                    If this
                    Warrant shall have been exercised only in part, then, unless
                    this Warrant
                    has expired, the Company shall, at its expense, at the time of
                    delivery of
                    such certificates, deliver to the Holder a new Warrant representing
                    the
                    number of shares with respect to which this Warrant shall not
                    then have
                    been exercised. In the event an Exercise Agreement is delivered
                    and the
                    Company is unable to issue the Warrant Shares, the Holder may,
                    at its
                    option, rescind such Exercise Agreement and such rescission will
                    not
                    effect the Holder's right to an extension of the Exercise Period
                    pursuant
                    to Section 4.13 of the Purchase Agreement. In any event, if the
                    Company is
                    unable to issue the Warrant Shares via DWAC transfer (or otherwise
                    without
                    restrictive legend), because (i) the Securities and Exchange
                    Commission
                    (the “Commission”) has issued a stop order with respect to the
                    registration statement relating to the Shares (the “Registration
                    Statement”), (ii) the Commission otherwise has suspended or withdrawn the
                    effectiveness of the Registration Statement, either temporarily
                    or
                    permanently, (iii) the Company has suspended or withdrawn the
                    effectiveness of the Registration Statement, either temporarily
                    or
                    permanently, (iv) no exemption from the registration requirements
                    is
                    otherwise available (including, without limitation, under Section
                    3(a)(9)
                    of the Act by virtue of a Conversion or Company-Elected
                    Conversion) or (v) otherwise, the Company shall not be required to
                    make any cash payments to the Holder in lieu of issuance of the
                    Warrant
                    Shares. Further, subject to Section 4.13 of the Purchase Agreement,
                    the
                    Warrant shall not be exercisable if (i) the Registration Statement
                    is not
                    effective at the time of exercise or (ii) an exemption from the
                    registration requirements of the Securities Act, as amended (the
                    "Act"),
                    is not available; provided, however, that for purposes of Section
                    4.13 of
                    the Purchase Agreement and the extension of the Exercise Period
                    pursuant
                    thereto, (x) the Company will have been deemed unable to issue
                    Warrant
                    Shares without restrictive legend and (y) the Warrant shall be
                    deemed to
                    have been exercised, if at the time the Holder attempts to deliver
                    an
                    Exercise Agreement, (1) the Registration Statement is not effective
                    and
                    (2) no exemption from the registration requirements of the Act
                    is
                    available (including, without limitation, under Section 3(a)(9) of
                    the Act by virtue of a Conversion or Company-Elected Conversion).
                    

                

              

      

       

                      

      
        
          2

        

        
          
          

          
            

          

        

        
          
          

        

      

       

    

    (b)  Notwithstanding
      anything in this Warrant to the contrary, in no event shall the Holder be
      entitled to exercise a number of Warrants (or portions thereof) in excess of
      the
      number of Warrants (or portions thereof) upon exercise of which the sum of
      (i)
      the number of shares of Common Stock beneficially owned by the Holder and its
      affiliates (other than shares of Common Stock which, but for this proviso,
      may
      be deemed beneficially owned through the ownership of the unexercised Warrants
      and the unexercised or unconverted portion of any other securities of the
      Company subject to a limitation on conversion or exercise analogous to the
      limitation contained herein) and (ii) the number of shares of Common Stock
      issuable upon exercise of the Warrants (or portions thereof) with respect to
      which the determination described herein is being made, would result in
      beneficial ownership by the Holder and its affiliates of more than 4.9% of
      the
      outstanding shares of Common Stock. For purposes of the immediately preceding
      sentence, beneficial ownership shall be determined in accordance with Section
      13(d) of the Securities Exchange Act of 1934, as amended, and Regulations 13D-G
      thereunder, except as otherwise provided in this paragraph (b). Notwithstanding
      anything in this Warrant to the contrary, the restrictions on exercise of this
      Warrant set forth in this paragraph shall not be amended without (i) the written
      consent of the Holder and the Company and (ii) the approval of the holders
      of a
      majority of the Common Stock present, or represented by proxy, and voting at
      any
      meeting called to vote on the amendment of such restriction. 

     

    2.  Period
      of Exercise. This Warrant is exercisable at
      any time or from time to time on or after the date on which this Warrant is
      issued and delivered pursuant to the terms of the Purchase Agreement (the "Issue
      Date") and before 5:00 p.m., New York City time on the second (2nd) anniversary
      of the Issue Date (the "Exercise Period"); provided, however, that the Exercise
      Period may be extended pursuant to Section 4.13 of the Purchase
      Agreement.

     

    3.  Certain
      Agreements of the Company. The Company hereby
      covenants and agrees as follows:

     

    (a)  Shares
      to be Fully Paid. All Warrant Shares will, upon
      issuance in accordance with the terms of this Warrant, be validly issued, fully
      paid, and nonassessable and free from all taxes, liens, and charges with respect
      to the issue thereof.

     

    
      
        3

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    (b)  Reservation
      of Shares. During the Exercise Period, the Company
      shall at all times have authorized, and reserved for the purpose of issuance
      upon exercise of this Warrant, a sufficient number of shares of Common Stock
      to
      provide for the full exercise of this Warrant.

     

    (c)  Listing.
      The Company shall promptly secure the listing of the Warrant Shares upon each
      national securities exchange or automated quotation system, if any, upon which
      shares of Common Stock are then listed (subject to official notice of issuance
      upon exercise of this Warrant) and shall maintain, so long as any other shares
      of Common Stock shall be so listed, such listing of all Warrant Shares; and
      the
      Company shall so list on each national securities exchange or automated
      quotation system, as the case may be, and shall maintain such listing of, any
      other shares of capital stock of the Company issuable upon the exercise of
      this
      Warrant if and so long as any shares of the same class shall be listed on such
      national securities exchange or automated quotation system.

     

    (d)  Certain
      Actions Prohibited. The Company will not, by
      amendment of its charter or through any reorganization, transfer of assets,
      consolidation, merger, dissolution, issue or sale of securities, or any other
      voluntary action, avoid or seek to avoid the observance or performance of any
      of
      the terms to be observed or performed by it hereunder, but will at all times
      in
      good faith assist in the carrying out of all the provisions of this Warrant
      and
      in the taking of all such action as may reasonably be requested by the Holder
      in
      order to protect the exercise privilege of the Holder against dilution or other
      impairment, consistent with the tenor and purpose of this Warrant. Without
      limiting the generality of the foregoing, the Company (i) will not increase
      the
      par value of any shares of Common Stock receivable upon the exercise of this
      Warrant above the Exercise Price then in effect, and (ii) will take all such
      actions as may be necessary or appropriate in order that the Company may validly
      and legally issue fully paid and nonassessable shares of Common Stock upon
      the
      exercise of this Warrant. 

     

    (e)  Successors
      and Assigns. This Warrant will be binding upon any
      entity succeeding to the Company by merger, consolidation, or acquisition of
      all
      or substantially all the Company's assets. 

     

    4.  Antidilution
      Provisions. During the Exercise Period, the
      number of Warrant Shares shall be subject to adjustment from time to time as
      provided in this Paragraph 4.

     

    (a)  Subdivision
      or Combination of Common Stock. If the
      Company at any time subdivides (by any stock split, stock dividend,
      recapitalization, reorganization, reclassification or otherwise) the shares
      of
      Common Stock acquirable hereunder into a greater number of shares, then, after
      the date of record for effecting such subdivision, the number of shares of
      Common Stock issuable upon exercise of this Warrant prior to such subdivision
      will be increased accordingly.

     

    
      
        4

      

      
        
        

        
          

        

      

      
        
        

      

    

     

     If
      the Company at any time combines (by reverse stock split, recapitalization,
      reorganization, reclassification or otherwise) the shares of Common Stock
      acquirable hereunder into a smaller number of shares, then, after the date
      of
      record for effecting such combination, the number of shares of Common Stock
      issuable upon exercise of this Warrant prior to such subdivision will be
      decreased accordingly. "Common Stock," for purposes of
      this Paragraph 4, includes the Common Stock, par value $0.001 per share, and
      any
      additional class of stock of the Company having no preference as to dividends
      or
      distributions on liquidation, provided that the shares purchasable pursuant
      to
      this Warrant shall include only shares of Common Stock, par value $0.001 per
      share, in respect of which this Warrant is exercisable, or shares resulting
      from
      any subdivision or combination of such Common Stock, or in the case of any
      reorganization, reclassification, consolidation, merger, or sale of the
      character referred to in Paragraph 4(c) hereof, the stock or other securities
      or
      property provided for in such Paragraph.

     

    (b)  Consolidation,
      Merger or Sale. In case of (i) any consolidation
      of the Company with, or merger of the Company into any other corporation or
      entity, or (ii) any sale or conveyance of all or substantially all of the assets
      of the Company other than in connection with a plan of complete liquidation
      of
      the Company (each of clause (i) and (ii) shall be referred to as a “Fundamental
      Transaction”), then as a condition of such Fundamental Transaction, adequate
      provision will be made whereby the Holder will thereafter (at any time or from
      time to time during the remainder of the Exercise Period) have the right to
      acquire and receive upon exercise of this Warrant in lieu of the shares of
      Common Stock immediately theretofor acquirable upon the exercise of this
      Warrant, such shares of stock, securities or assets as may be issued or payable
      with respect to or in exchange for the number of shares of Common Stock
      immediately theretofore acquirable and receivable upon exercise of this Warrant
      had such Fundamental Transaction not taken place.

     

    In
      any
      such case, the Company will make appropriate provision to insure that the
      provisions of this Paragraph 4 hereof will thereafter be applicable as nearly
      as
      may be in relation to any shares of stock or securities thereafter deliverable
      upon the exercise of this Warrant. The Company will not effect any Fundamental
      Transaction unless, prior to the consummation thereof, (i) the successor or
      acquiring entity (if other than the Company), (ii) any other entity whose stock,
      securities or assets the holders of the Common Stock of the Company are entitled
      to receive as a result of such Fundamental Transaction, and (iii) any parent,
      subsidiary or affiliate of such successor, acquiring entity or other entity
      whose common stock this Warrant shall be exercisable into by virtue of the
      penultimate paragraph of this Paragraph 4(c) (any or all of such entities being
      hereafter referred to as a “Successor Entity”) assumes by written instrument the
      obligations under this Paragraph 4 and the obligations to deliver to the Holder
      such shares of stock, securities or assets as, in accordance with the foregoing
      provisions, the Holder may be entitled to acquire.

     

    Furthermore,
      in the event of a transaction contemplated by this Paragraph 4(c) involving
      the
      acquisition of the Company by a Public Acquirer (as defined below) for
      consideration consisting of all or part cash, at the option of the Holder,
      in
      lieu of any cash in respect of shares of Common Stock underlying this Warrant,
      this Warrant (or such proportion thereof as is equal to the proportion of cash
      to stock to be paid for the Company) shall thereafter be exercisable for the
      common stock of the Public Acquirer for the remainder of the Exercise
      Period  (and
      otherwise in accordance with the terms hereof), with the number of shares
      thereafter underlying this Warrant determined by multiplying the number of
      shares for which this Warrant is exercisable immediately prior to such
      transaction by a fraction, the numerator of which is the cash consideration
      per
      share paid for the Company and the denominator of which is the Market Price
      of
      the Public Acquirer’s common stock, where “Market Price” means the average
      closing price of the Public Acquirer’s common stock over the five trading days
      immediately following the closing date of the transaction. In the case of a
      transaction involving partial cash consideration, the proportion of this Warrant
      as is equal to the proportion of stock to cash in such transaction shall
      thereafter be exercisable for stock of the Public Acquirer in accordance with
      the preceding terms of this Paragraph 4(c), with the number of shares underlying
      this Warrant adjusted to reflect the number of shares of common stock of the
      Public Acquirer to be issued for each share of Common Stock of the Company.
      Following any adjustment hereunder, the Exercise Price shall be proportionately
      adjusted, by multiplying the Exercise Price then in effect by a fraction, the
      numerator of which is the number of shares issuable prior to the adjustment
      and
      the denominator of which is the number of shares issuable after the adjustment.
      “Public Acquirer” means any entity that has publicly traded common stock whether
      publicly traded in the United States or in any other jurisdiction, it being
      understood that (1) “common stock” as used in this Paragraph 4(c) includes
      common equity equivalents, trust shares, limited partnership interests, ordinary
      shares, American Depositary Receipts, American Depositary Shares, and any other
      similar securities or derivate thereof, and (2) the Company shall be deemed
      to
      have been acquired by a Public Acquirer where any Successor Entity has publicly
      traded common stock whether traded in the United States or any other
      jurisdiction, even if such Successor Entity is not the direct acquirer or
      successor to the Company. Following any transaction contemplated by this
      Paragraph 4(c) the term Warrant Shares shall be deemed to refer to the shares
      for which this Warrant is thereafter exercisable in accordance with the
      provisions hereof.

     

    
      
        5

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    In
      addition, if holders of Common Stock are given a choice as to the securities,
      cash (which shall be treated in accordance with the preceding paragraph) or
      property to be received in a Fundamental Transaction (including a right to
      elect
      to receive any particular one or combination of more than one of the foregoing),
      then the Holder shall be given the same choice of consideration upon any
      exercise of this Warrant following such Fundamental Transaction, which choice
      of
      consideration can be made at the time of exercise at any time prior to the
      expiration of the Exercise Period.

     

    (c)  Distribution
      of Assets. In case the Company shall declare or
      make any distribution of its assets (including cash) to holders of Common Stock
      as a partial liquidating dividend, by way of return of capital or otherwise,
      then, after the date of record for determining stockholders entitled to such
      distribution, but prior to the date of distribution, the Holder shall be
      entitled upon exercise of this Warrant for the purchase of any or all of the
      shares of Common Stock subject hereto, to receive the amount of such assets
      which would have been payable to the holder had such holder been the holder
      of
      such shares of Common Stock on the record date for the determination of
      stockholders entitled to such distribution.

     

    
      
        6

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    (d)  Notice
      of Adjustment. Upon the occurrence of any event
      which requires any adjustment of the Exercise Price, then, and in each such
      case, the Company shall give notice thereof to the Holder, which notice shall
      state the Exercise Price resulting from such adjustment and the increase or
      decrease in the number of Warrant Shares purchasable at such price upon
      exercise, setting forth in reasonable detail the method of calculation and
      the
      facts upon which such calculation is based. Such calculation shall be certified
      by the chief financial officer of the Company.

     

    (e)  Minimum
      Adjustment of Exercise Price. No adjustment of the
      Exercise Price shall be made in an amount of less than 1% of the Exercise Price
      in effect at the time such adjustment is otherwise required to be made, but
      any
      such lesser adjustment shall be carried forward and shall be made at the time
      and together with the next subsequent adjustment which, together with any
      adjustments so carried forward, shall amount to not less than 1% of such
      Exercise Price.

     

    (f)  No
      Fractional Shares. No fractional shares of Common
      Stock are to be issued upon the exercise of this Warrant. If the exercise of
      this Warrant would result in a fractional share of Common Stock, such fractional
      share shall be disregarded and the number of shares of Common Stock issuable
      upon exercise of the Warrant shall be the next higher number of shares.

     

    (g)  Other
      Notices. In case at any time:

     

    (i)  the
      Company shall declare any dividend upon the Common Stock payable in shares
      of
      stock of any class or make any other distribution (including dividends or
      distributions payable in cash out of retained earnings) to the holders of the
      Common Stock;

     

    (ii)  the
      Company shall offer for subscription pro rata to the holders of the Common
      Stock
      any additional shares of stock of any class or other rights;

     

    (iii)  there
      shall be any capital reorganization of the Company, or reclassification of
      the
      Common Stock, or consolidation or merger of the Company with or into, or sale
      of
      all or substantially all its assets to, another corporation or entity;
      or

     

    (iv)  there
      shall be a voluntary or involuntary dissolution, liquidation or winding-up
      of
      the Company;

     

    then,
      in
      each such case, the Company shall give to the Holder (a) notice of the date
      on
      which the books of the Company shall close or a record shall be taken for
      determining the holders of Common Stock entitled to receive any such dividend,
      distribution, or subscription rights or for determining the holders of Common
      Stock entitled to vote in respect of any such reorganization, reclassification,
      consolidation, merger, sale, dissolution, liquidation or winding-up and (b)
      in
      the case of any such reorganization, reclassification, consolidation, merger,
      sale, dissolution, liquidation or winding-up, notice of the date (or, if not
      then known, a reasonable approximation thereof by the Company) when the same
      shall take place. 

     

    
      
        7

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    Such
      notice shall also specify the date on which the holders of Common Stock shall
      be
      entitled to receive such dividend, distribution, or subscription rights or
      to
      exchange their Common Stock for stock or other securities or property
      deliverable upon such reorganization, reclassification, consolidation, merger,
      sale, dissolution, liquidation, or winding-up, as the case may be. Such notice
      shall be given at least 30 days prior to the record date or the date on which
      the Company's books are closed in respect thereto. Failure to give any such
      notice or any defect therein shall not affect the validity of the proceedings
      referred to in clauses (i), (ii), (iii) and (iv) above.

     

    (h)  Certain
      Events. If any event occurs of the type
      contemplated by the adjustment provisions of this Paragraph 4 but not expressly
      provided for by such provisions, the Company will give notice of such event
      as
      provided in Paragraph 4(e) hereof, and the Company's Board of Directors will
      make an appropriate adjustment in the Exercise Price and the number of shares
      of
      Common Stock acquirable upon exercise of this Warrant so that the rights of
      the
      Holder shall be neither enhanced nor diminished by such event.

     

    (i)  Withholding
      Taxes. In the event that an adjustment to the
      Exercise Price (or a failure to adjust the Exercise Price) results in a
      constructive distribution to the Holder of the Warrants under Section 305 of
      the
      Internal Revenue Code of 1986, as amended, the Company may withhold, to the
      extent required by applicable law, any applicable United States federal
      withholding tax from any subsequent distributions of cash or property made
      to
      the Holder, including any Common Stock issued by the Company upon the exercise
      of this Warrant. 

     

    5.  Issue
      Tax. The issuance of certificates for Warrant
      Shares upon the exercise of this Warrant shall be made without charge to the
      Holder or such shares for any issuance tax or other costs in respect thereof,
      provided that the Company shall not be required to pay any tax which may be
      payable in respect of any transfer involved in the issuance and delivery of
      any
      certificate in a name other than the Holder.

     

    6.  No
      Rights or Liabilities as a Stockholder. This
      Warrant shall not entitle the Holder to any voting rights, dividend rights
      or
      other rights as a stockholder of the Company. No provision of this Warrant,
      in
      the absence of affirmative action by the Holder to purchase Warrant Shares,
      and
      no mere enumeration herein of the rights or privileges of the Holder, shall
      give
      rise to any liability of such holder for the Exercise Price or as a stockholder
      of the Company, whether such liability is asserted by the Company or by
      creditors of the Company.

     

    7.  Transfer,
      Exchange, and Replacement of Warrant.

     

    (a)  Transfer.
      This Warrant and the rights granted to the Holder are transferable, in whole
      or
      in part, upon surrender of this Warrant, together with a properly executed
      assignment in the form attached hereto, at the office or agency of the Company
      referred to in Paragraph 7(e) below. Until due presentment for registration
      of
      transfer on the books of the Company, the Company may treat the registered
      Holder as the owner and Holder for all purposes, and the Company shall not
      be
      affected by any notice to the contrary. 

     

    
      
        8

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    (b)  Warrant
      Exchangeable for Different Denominations. This
      Warrant is exchangeable, upon the surrender hereof by the Holder at the office
      or agency of the Company referred to in Paragraph 7(e) below, for new Warrants
      of like tenor representing in the aggregate the right to purchase the number
      of
      shares of Common Stock which may be purchased hereunder, each of such new
      Warrants to represent the right to purchase such number of shares as shall
      be
      designated by the Holder at the time of such surrender.

     

    (c)  Replacement
      of Warrant. Upon receipt of evidence reasonably
      satisfactory to the Company of the loss, theft, destruction, or mutilation
      of
      this Warrant and, in the case of any such loss, theft, or destruction, upon
      delivery of an indemnity agreement reasonably satisfactory in form and amount
      to
      the Company, or, in the case of any such mutilation, upon surrender and
      cancellation of this Warrant, the Company, at its expense, will execute and
      deliver, in lieu thereof, a new Warrant of like tenor.

     

    (d)  Cancellation;
      Payment of Expenses. Upon the surrender of this
      Warrant in connection with any transfer, exchange, or replacement as provided
      in
      this Paragraph 7, this Warrant shall be promptly canceled by the Company. The
      Company shall pay all taxes (other than securities transfer taxes) and all
      other
      expenses (other than legal expenses, if any, incurred by the Holder or
      transferees) and charges payable in connection with the preparation, execution,
      and delivery of Warrants pursuant to this Paragraph 7.

     

    (e)  Register.
      The Company shall maintain, at its principal executive offices (or such other
      office or agency of the Company as it may designate by notice to the Holder),
      a
      register for this Warrant, in which the Company shall record the name and
      address of the person in whose name this Warrant has been issued, as well as
      the
      name and address of each transferee and each prior owner of this Warrant.

     

    8.  Notices.
      All notices, requests, and other communications required or permitted to be
      given or delivered hereunder to the Holder shall be in writing, and shall be
      personally delivered, or shall be sent by certified or registered mail or by
      recognized overnight mail courier, postage prepaid and addressed, to such holder
      at the address shown for such holder on the books of the Company, or at such
      other address as shall have been furnished to the Company by notice from such
      Holder. All notices, requests, and other communications required or permitted
      to
      be given or delivered hereunder to the Company shall be in writing, and shall
      be
      personally delivered, or shall be sent by certified or registered mail or by
      recognized overnight mail courier, postage prepaid and addressed, to the office
      of the Company at 230 Constitution Drive, Menlo Park, California 94025, Attn:
      David Greenwood, fax no. (650) 473-7701 with copies to Latham & Watkins LLP,
      140 Scott Drive, Menlo Park, California 94025, Attn: Alan C. Mendelson, Esq.,
      fax no. (650) 463-2600, or at such other address as shall have been furnished
      to
      the Holder by notice from the Company. Any such notice, request, or other
      communication may be sent by facsimile, but shall in such case be subsequently
      confirmed by a writing personally delivered or sent by certified or registered
      mail or by recognized overnight mail courier as provided above. All notices,
      requests, and other communications shall be deemed to have been given either
      at
      the time of the receipt thereof by the person entitled to receive such notice
      at
      the address of such person for purposes of this Paragraph 8, or, if mailed
      by
      registered or certified mail or with a recognized overnight mail courier upon
      deposit with the United States Post Office or such overnight mail courier,
      if
      postage is prepaid and the mailing is properly addressed, as the case may
      be.

     

    
      
        9

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    9.  Governing
      Law. THIS WARRANT SHALL BE GOVERNED BY AND
      CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE APPLICABLE TO
      AGREEMENTS MADE AND TO BE PERFORMED IN THE STATE OF DELAWARE (WITHOUT REGARD
      TO
      PRINCIPLES OF CONFLICT OF LAWS). BOTH PARTIES IRREVOCABLY CONSENT TO THE
      EXCLUSIVE JURISDICTION OF THE UNITED STATES FEDERAL COURTS AND THE STATE COURTS
      LOCATED IN DELAWARE WITH RESPECT TO ANY SUIT OR PROCEEDING BASED ON OR ARISING
      UNDER THIS AGREEMENT, THE AGREEMENTS ENTERED INTO IN CONNECTION HEREWITH OR
      THE
      TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY AND IRREVOCABLY AGREE THAT ALL
      CLAIMS IN RESPECT OF SUCH SUIT OR PROCEEDING MAY BE DETERMINED IN SUCH COURTS.
      BOTH PARTIES IRREVOCABLY WAIVE THE DEFENSE OF AN INCONVENIENT FORUM TO THE
      MAINTENANCE OF SUCH SUIT OR PROCEEDING. BOTH PARTIES FURTHER AGREE THAT SERVICE
      OF PROCESS UPON A PARTY MAILED BY FIRST CLASS MAIL SHALL BE DEEMED IN EVERY
      RESPECT EFFECTIVE SERVICE OF PROCESS UPON THE PARTY IN ANY SUCH SUIT OR
      PROCEEDING. NOTHING HEREIN SHALL AFFECT EITHER PARTY'S RIGHT TO SERVE PROCESS
      IN
      ANY OTHER MANNER PERMITTED BY LAW. BOTH PARTIES AGREE THAT A FINAL
      NON-APPEALABLE JUDGMENT IN ANY SUCH SUIT OR PROCEEDING SHALL BE CONCLUSIVE
      AND
      MAY BE ENFORCED IN OTHER JURISDICTIONS BY SUIT ON SUCH JUDGMENT OR IN ANY OTHER
      LAWFUL MANNER. 

     

    10.  Miscellaneous.

     

    (a)  Amendments.
      This Warrant and any provision hereof may only be amended by an instrument
      in
      writing signed by the Company and the Holder.

     

    (b)  Descriptive
      Headings.The descriptive headings of the several
      paragraphs of this Warrant are inserted for purposes of reference only, and
      shall not affect the meaning or construction of any of the provisions
      hereof.

     

    (c)  Cashless
      Exercise. This Warrant may be exercised by presentation and
      surrender of this Warrant to the Company at its principal executive offices
      with
      a written notice of the holder's intention to effect a cashless exercise,
      including a calculation of the number of shares of Common Stock to be issued
      upon such exercise in accordance with the terms hereof, or in connection with
      a
      Company-Elected Conversion (a "Cashless Exercise"). In the event of a Cashless
      Exercise, the Holder shall be entitled to receive a certificate for the number
      of Warrant Shares equal to the quotient obtained by dividing [(A-B) (X)] by
      (A),
      where:

     

    

    (A)
      = the
      closing price on the trading day immediately preceding the date of such
      election; provided, however,that if the Cashless Exercise is in
      connection with a Company-Elected Conversion, “A” in the formula above shall
      equal the volume-weighted average price of the Company’s common stock as
      reported by Bloomberg L.P., or any successor performing similar functions for
      the five (5) trading days beginning the day immediately following the date
      of
      the Company-Elected Conversion.

     

    
      
        10

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    (B)
=
      the
      Exercise Price of this Warrant, as adjusted; and

    

    (X)
      = the
      number of Warrant Shares issuable upon exercise of this Warrant in accordance
      with the terms of this Warrant by means of a cash exercise rather than a
      cashless exercise.

     

    (d)  Remedies.
      The Company acknowledges that a breach by it of its obligations
      hereunder will cause irreparable harm to the Holder by vitiating the intent
      and
      purpose of the transactions contemplated hereby. Accordingly, the Company
      acknowledges that the remedy at law for a breach of its obligations under this
      Warrant will be inadequate and agrees, in the event of a breach or threatened
      breach by the Company of the provisions of this Warrant, that the Holder shall
      be entitled, in addition to all other available remedies in law or in equity,
      to
      an injunction or injunctions to prevent or cure any breaches of the provisions
      of this Agreement and to enforce specifically the terms and provisions of this
      Warrant, without the necessity of showing economic loss and without any bond
      or
      other security being required.

     

    [REMAINDER
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        11

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    EXHIBIT
      4.3

     

      IN
        WITNESS WHEREOF, the Company has caused this Warrant to be signed by
        its duly authorized officer.

       

      
        	 	 	 
	 	GERON
                CORPORATION
	 
 	 
 	 
 
	 	By:  	 
	 	
                
                  

                

                Name: 
                  David L. Greenwood

              
	 	
                Title:    Executive Vice President
                  and 

                    
Chief
                  Financial Officer

              
	 	 
	 	 
	 	Dated as of March 13,
                2007

      

                                                                                                                                        
        

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      FORM
        OF EXERCISE AGREEMENT

       

      Dated:
        ________ __, 200_

       

      To:
        GERON
        CORPORATION

       

      The
        undersigned, pursuant to the provisions set forth in the Warrant attached
        hereto, hereby agrees to purchase ________ shares of Common Stock covered
        by
        such Warrant, and makes payment herewith in full therefor at the price per
        share
        provided by such Warrant in cash or by certified or official bank check in
        the
        amount of, or by surrender of securities issued by the Company (including
        a
        portion of the Warrant) having a market value (in the case of a portion of
        this
        Warrant, determined in accordance with Paragraph 10(c) of the Warrant) equal
        to
        $_________. Please issue a certificate or certificates for such shares of
        Common
        Stock in the name of and pay any cash for any fractional share to:

      
         

        

          
            	 	
                    Name:
                      

                  
	 	
                    Signature:
                      

                  
	 	
                    Address:

                  
	 	
                  
	 	 
	 	 
	 	
                    Note:
                      The
                      above signature should correspond exactly with the name on
                      the face of the
                      Warrant attached hereto.

                  

          

        

         

        and,
          if
          said number of shares of Common Stock shall not be all the shares purchasable
          under the Warrant attached hereto, a new Warrant is to be issued in the
          name of
          said undersigned covering the balance of the shares purchasable thereunder
          less
          any fraction of a share paid in cash.

         

        
          
            
            

          

          
            
            

            
              

            

          

          
            
            

          

        

        FORM
          OF ASSIGNMENT

         

        FOR
          VALUE
          RECEIVED, the undersigned hereby sells, assigns, and transfers all the
          rights of
          the undersigned under the Warrant attached hereto, with respect to the
          number of
          shares of Common Stock covered thereby set forth hereinbelow, to:

        

          
            	
                    Name
                      of Assignee

                  	
                    Address

                  	
                    No
                      of Shares

                  
	 	 	 
	 	 	 

          

        

         

         
          ,
          and
          hereby irrevocably constitutes and appoints
          _____________________________________ as agent and attorney-in-fact to
          transfer
          said Warrant on the books of the within-named corporation, with full power
          of
          substitution in the premises.

         

        

          
            	
                    Dated:
                      ________ __, 200_

                  
	
                    In
                      the presence of:

                  
	
                    _________________________

                  

          

        

         

        
          
            	 	
                    Name:
                      

                  
	 	
                    Signature:

                  
	 	Title
                    of Signing Officer or Agent (if any):
	 	
                    Address:

                  
	 	
                  
	 	 
	 	 
	 	
                    Note:
                      The
                      above signature should correspond exactly with the name on
                      the face of the
                      Warrant attached
                      hereto.

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