EXHIBIT 4.1 

COMMON STOCK PURCHASE AGREEMENT


     THIS COMMON
STOCK PURCHASE AGREEMENT (“Agreement”) is made and entered into as of May 11,
2009 (the “Effective
Date”), by and between GERON CORPORATION,
a Delaware corporation having its principal place of business at 230
Constitution Drive, Menlo Park, California 94025 (“Geron”), and DP Clinical,
Inc., a Maryland corporation with offices at 1803 Research Boulevard, Suite 404,
Rockville, Maryland 20850 (“[COMPANY]”). 

	       A.     	Geron and COMPANY are the parties
      to that certain Master Agreement dated as of October 27, 2006 (the
      “Master Agreement”), and related Addendum Agreements under which Geron
      and COMPANY have agreed that COMPANY will perform certain services on
      behalf of Geron on the terms set forth therein.
	 
	       B.	Pursuant to the Master Agreement,
      Geron may pay for the price of such services by delivery of shares of
      Geron’s Common Stock (the “Shares”).
	 
	       C.	Geron has elected to make payment
      for such services through the delivery of Shares, pursuant to the terms
      and conditions of the Master Agreement and this
  Agreement.


THE PARTIES AGREE AS FOLLOWS:


	1.	ISSUANCE OF SHARES;
      ADJUSTMENTS.
	 
		1.1.	As payment of the price
      specified in the Services Agreement Addenda, Geron will issue and deliver
      certificates for 205,252 Shares. Upon issuance and delivery of the
      certificate(s) for the Shares, all Shares shall be duly authorized and
      validly issued and represent fully paid shares of Geron’s Common
      Stock.
	 
	2.	CLOSING;
      DELIVERY.
	 
		2.1.	The consummation of the
      transaction contemplated by this Agreement (a “Closing”) shall be held at
      such time and place as is mutually agreed upon between the parties, but in
      any event Geron shall make commercially reasonable efforts to accomplish
      the Closing no later than five (5) business days after the Effective Date
      hereof (the “Closing Date”). At the Closing, Geron shall deliver to
      COMPANY one or more certificates representing all of the Shares, which
      Shares shall be issued in the name of COMPANY or its designee and in such
      denominations as COMPANY shall specify.
	 
	 	2.2.	Geron’s obligations to
      issue and deliver the stock certificate(s) representing the Shares to
      COMPANY at the Closing shall be subject to the following conditions, which
      may be waived by Geron:
	          	            	              	
			2.2.1.	the covenants and obligations
      that COMPANY is required to perform or to comply with pursuant to this
      Agreement, at or prior to the Closing, must have been duly performed and
      complied with in all material respects; and
	 
			2.2.2.	the representations and
      warranties made by COMPANY herein shall be true and correct in all
      material respects as of the Closing Date.
	 
		2.3.	COMPANY’s obligation to
      accept delivery of the stock certificate(s) representing the Shares at the
      Closing shall be subject to the following conditions, any one or more of
      which may be waived by COMPANY:
	 
			2.3.1.	the covenants and obligations
      that Geron is required to perform or to comply with pursuant to this
      Agreement, at or prior to the Closing, must have been duly performed and
      complied with in all material respects;









			2.3.2.	Geron shall have available
      under its Certificate of Incorporation sufficient authorized shares of
      Common Stock to issue the Shares to COMPANY; and
	 
			2.3.3.	the representation and warranties
      made by Geron herein shall be true and correct in all material respects as
      of any Closing Date.
		            	              	
	3.	RESTRICTIONS ON
      RESALE OF SHARES.
	          	
		3.1.	Legends.
      COMPANY understands and acknowledges
      that the Shares are not registered under the Securities Act of 1933 (the
      “Act”), and that under the Act and other applicable laws COMPANY may be
      required to hold such Shares for an indefinite period of time. Each stock
      certificate representing Shares shall bear the following legends:
    
	 
			“THE SECURITIES
      REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
      1933, AS AMENDED (THE “ACT”). ANY TRANSFER OF SUCH SECURITIES SHALL BE
      INVALID UNLESS A REGISTRATION STATEMENT UNDER THE ACT IS IN EFFECT AS TO
      SUCH TRANSFER OR, IN THE OPINION OF COUNSEL REASONABLY ACCEPTABLE TO
      GERON, SUCH REGISTRATION IS UNNECESSARY FOR SUCH TRANSFER TO COMPLY WITH
      THE ACT. THE SECURITIES REPRESENTED HEREBY ARE SUBJECT TO THE TERMS OF THE
      COMMON STOCK PURCHASE AGREEMENT BY AND BETWEEN GERON AND COMPANY, DATED AS
      OF MAY 11, 2009. A COPY OF THE AGREEMENT CAN BE OBTAINED FROM THE
      SECRETARY OF GERON.”
	 
		3.2.	Limits on Sales.
      COMPANY agrees that if it decides to
      resell some or all of the Shares, it will do so only through orderly sales
      executed through a top-tier brokerage house, and in an appropriate manner
      based upon whether the shares are registered or unregistered,
      i.e.,
      on the Nasdaq Global Market or in a Rule 144 or Rule 144A compliant
      transaction. COMPANY further agrees that it will not engage in short
      selling with respect to the Stock.
	 
		3.3.	Further Limitations.
      Geron shall not be required (i) to
      transfer on its books any Shares that have been sold or otherwise
      transferred in violation of any of the provisions of this Agreement or
      applicable securities laws; or (ii) to treat as owner of such Shares or to
      accord the right to vote or pay dividends to any purchaser or other
      transferee to whom such Shares shall have been so transferred in violation
      of any of the provisions of this Agreement or applicable securities
      laws.
	 
	4.	REGISTRATION
      RIGHTS
	 
		4.1.	Geron agrees to make
      commercially reasonable efforts to file with the Securities and Exchange
      Commission (the “Commission”) within ten (10)
      business days after the Closing Date, a registration statement under the
      Act (the “Registration
      Statement”), on Form S-3 or other
      appropriate form, so as to permit a non-underwritten public offering and
      resale of the Shares under the Act by COMPANY. Geron agrees to diligently
      pursue making the Registration Statement effective. Geron will make
      commercially reasonable efforts to notify COMPANY of the effectiveness of
      the Registration Statement within one (1) business day of receiving notice
      from the Commission declaring the Registration Statement effective.
    
	 
		4.2.	Geron will make
      commercially reasonable efforts to maintain the Registration Statement and
      any post-effective amendment thereto filed under this Section 4 effective
      under the Act until the earliest of (i) the date that none of the Shares
      covered by such Registration Statement are issued and outstanding, (ii)
      the date that all of the Shares have been sold pursuant to such
      Registration Statement, (iii) the date COMPANY receives an opinion of
      counsel from Geron, which counsel shall be reasonably acceptable to
      COMPANY, that the Shares may be sold under the provisions of Rule 144 or
      any similar provision then in effect under the Act, or (without limitation
      as to volume, or (iv) the date that all Shares have been otherwise
      transferred to persons who may trade such shares without restriction under
      the Act, and Geron has delivered a new certificate or other evidence of
      ownership for such securities not bearing a restrictive legend.
  
	 		
		4.3.	Geron, at its
      expense, shall furnish to COMPANY with respect to the Shares registered
      under the Registration Statement such reasonable number of copies of the
      Registration Statement, prospectuses and preliminary prospectuses in
      conformity with the requirements of the Act and such other documents as
      COMPANY may reasonably request, in order to facilitate the public sale or
      other disposition of all or any of the Shares by COMPANY, provided,
      however, that the obligation of Geron to deliver copies of prospectuses or
      preliminary prospectuses to COMPANY shall be subject to the receipt by
      Geron of reasonable assurances from COMPANY that COMPANY will comply with
      the applicable provisions of the Act and of such other securities or blue
      sky laws as may be applicable in connection with any use of such
      prospectuses or preliminary prospectuses.


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	 	4.4.	All fees, disbursements and
      out-of-pocket expenses and costs incurred by Geron in connection with the
      preparation and filing of the Registration Statement under Section 4.1 and
      in complying with applicable securities and Blue Sky laws (including,
      without limitation, all attorneys' fees of Geron) shall be borne by Geron.
      COMPANY shall bear the cost of all fees and expenses of COMPANY’s
      counsel.
		            	
	 	4.5.	Geron will advise COMPANY
      promptly after it shall receive notice or obtain knowledge of the issuance
      of any stop order by the Commission delaying or suspending the
      effectiveness of the Registration Statement or of the initiation of any
      proceeding for that purpose, and Geron will use its commercially
      reasonable efforts to prevent the issuance of any stop order or to obtain
      its withdrawal as promptly as possible if such stop order should be
      issued.
	 
	 	4.6.	With a view to making available
      to COMPANY the benefits of Rule 144 (or its successor rule) and any other
      rule or regulation of the Commission that may at the time permit COMPANY
      to sell the Shares to the public without registration, Geron covenants and
      agrees to make commercially reasonable efforts to: (i) make and keep
      public information available, as those terms are understood and defined in
      Rule 144, until the earliest of (A) such date as all of the Shares may be
      resold pursuant to Rule 144 or any other rule of similar effect or (B)
      such date as all of the Shares shall have been resold; and (ii) file with
      the Commission in a timely manner all reports and other documents required
      of Geron under the Act and under the Securities Exchange Act of 1934, as
      amended (the “Exchange
      Act”).
	 
	 	4.7.	COMPANY will cooperate with Geron
      in all respects in connection with this Agreement, including timely
      supplying all information reasonably requested by Geron (which shall
      include all information regarding COMPANY and proposed manner of sale of
      the Shares required to be disclosed in any Registration Statement) and
      executing and returning all documents reasonably requested in connection
      with the registration and sale of the Shares and entering into and
      performing their obligations under any underwriting agreement, if the
      offering is an underwritten offering, in usual and customary form, with
      the managing underwriter or underwriters of such underwritten offering.
      Nothing in this Agreement shall obligate COMPANY to consent to be named as
      an underwriter in any Registration Statement.
	 
	5. 	INDEMNIFICATION.
	          	
	 	5.1.	
      Geron agrees to indemnify and hold harmless
      COMPANY (and each person, if any, who controls COMPANY within the meaning
      of Section 15 of the Act, and each officer and director of COMPANY)
      against any and all losses, claims, damages or liabilities (or actions or
      proceedings in respect thereof), joint or several, directly or indirectly
      based upon or arising out of (i) any untrue statement or alleged untrue
      statement of any material fact contained in the Registration Statement,
      any preliminary prospectus, final prospectus or summary prospectus
      contained therein or used in connection with the offering of the Shares,
      or any amendment or supplement thereto, or (ii) any omission or alleged
      omission to state a material fact required to be stated therein or
      necessary to make the statements therein not misleading; and Geron will
      reimburse each such indemnified party for any legal or any other expenses
      reasonably incurred by them in connection with investigating, preparing,
      pursuing or defending any such loss, claim, damage, liability, action or
      proceeding, except insofar as any such loss, claim, damage, liability,
      action, proceeding or expense arises out of or is based upon (A) an untrue
      statement or alleged untrue statement or omission or alleged omission made
      in the Registration Statement, any such preliminary prospectus, final prospectus, summary prospectus, amendment or
      supplement in reliance upon and in conformity with written information
      furnished to Geron by or on behalf of COMPANY or such other person
      expressly for use in the preparation thereof, (B) the failure of COMPANY
      to comply with its covenants and agreements contained in Sections 7.1 or
      7.5.2 hereof or (C) any misstatement or omission in any prospectus that is
      corrected in any subsequent prospectus that was delivered to COMPANY prior
      to the pertinent sale or sales by COMPANY. Such indemnity shall remain in
      full force and effect, regardless of any investigation made by such
      indemnified party and shall survive the transfer of the Shares by
      COMPANY.



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		5.2.	COMPANY agrees to indemnify and hold harmless Geron (and
      each person, if any, who controls Geron within the meaning of Section 15
      of the Act, and each officer and director of Geron) from and against
      losses, claims, damages or liabilities (or actions or proceedings in
      respect thereof), joint or several, directly or indirectly based upon or
      arising out of, (i) any failure of COMPANY to comply with the covenants
      and agreements contained in Sections 7.1 and 7.5.2 hereof or (ii) any
      untrue statement of a material fact contained in the Registration
      Statement or any omission of a material fact required to be stated in the
      Registration Statement or necessary in order to make the statements in the
      Registration Statement not misleading if such untrue statement or omission
      was made in reliance upon and in conformity with written information
      furnished to Geron by or on behalf of COMPANY specifically for use in
      preparation of the Registration Statement; provided, however, that COMPANY
      shall not be liable in any such case for (A) any untrue statement or
      omission in the Registration Statement, prospectus, or other such document
      which statement is corrected by COMPANY and delivered to Geron prior to
      the sale from which such loss occurred, (B) any untrue statement or
      omission in any prospectus which is corrected by COMPANY in any subsequent
      prospectus, or supplement or amendment thereto, and delivered to Geron
      prior to the sale or sales from which a loss or liability arose, or (C)
      any failure by Geron to fulfill any of its obligations under Section 5.1
      hereof.
		            	
		5.3.	Promptly after receipt by any indemnified person of a
      notice of a claim or the beginning of any action in respect of which
      indemnity is to be sought against an indemnifying person pursuant to this
      Section 5, such indemnified person shall notify the indemnifying person in
      writing of such claim or of the commencement of such action, but the
      omission to so notify the indemnifying party will not relieve it from any
      liability which it may have to any indemnified party under this Section 5
      (except to the extent that such omission materially and adversely affects
      the indemnifying party’s ability to defend such action) or from any
      liability otherwise than under this Section 5. Subject to the provisions
      hereinafter stated, in case any such action shall be brought against an
      indemnified person, the indemnifying person shall be entitled to
      participate therein, and, to the extent that it shall elect by written
      notice delivered to the indemnified party promptly after receiving the
      aforesaid notice from such indemnified party, shall be entitled to assume
      the defense thereof, with counsel reasonably satisfactory to such
      indemnified person. After notice from the indemnifying person to such
      indemnified person of its election to assume the defense thereof, such
      indemnifying person shall not be liable to such indemnified person for any
      legal expense subsequently incurred by such indemnified person in
      connection with the defense thereof, provided, however, that if there
      exists or shall exist a conflict of interest that would make
      inappropriate, in the reasonable opinion of counsel to the indemnified
      person, for the same counsel to represent both the indemnified person and
      such indemnifying person or any affiliate or associate thereof, the
      indemnified person shall be entitled to retain its own counsel at the
      expense of such indemnifying person; provided, however, that no
      indemnifying person shall be responsible for the fees and expenses of more
      than one separate counsel (together with appropriate local counsel) for
      all indemnified parties. In no event shall any indemnifying person be
      liable in respect to any amounts paid in settlement of any action unless
      the indemnifying person shall have approved the terms of such settlement.
      No indemnifying person shall, without the prior written consent of the
      indemnified person, effect any settlement of any pending or threatened
      proceeding in respect of which any indemnified person is or could have
      been a party and indemnification could have been sought hereunder by such
      indemnified person, unless such settlement includes an unconditional
      release of such indemnified person from all liability on claims that are
      the subject matter of such proceeding.
		 
		5.4.	The provisions of this Section 5 shall survive the
      termination of this Agreement.
	 		
	6.	REPRESENTATIONS AND
      ACKNOWLEDGEMENT OF GERON.
	          		
		Geron hereby represents,
      warrants and covenants to COMPANY as follows:
	 		
		6.1.	Organization, Good Standing and
      Qualification. Geron is a corporation duly
      organized, validly existing and in good standing under the laws of the
      State of Delaware and has all requisite corporate power and authority to
      carry on its business as now conducted and as presently proposed to be
      conducted. Geron is duly qualified to transact business and is in good
      standing as a foreign corporation in each jurisdiction in which the
      failure to so qualify would have a material adverse effect on its business
      or properties.


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		6.2.	Authorization.
      All corporate action on the part of
      Geron, its officers, directors and stockholders necessary for the
      authorization, execution and delivery of this Agreement, the performance
      of all obligations of Geron hereunder and the authorization, issuance and
      delivery of the Shares has been taken or will be taken prior to the
      Closing, and this Agreement, when executed and delivered will constitute
      valid and legally binding obligations of Geron, enforceable against Geron
      in accordance with its terms, except as limited by applicable bankruptcy,
      insolvency, reorganization, moratorium, fraudulent conveyance and other
      laws of general application affecting enforcement of creditors’ rights
      generally, as limited by laws relating to the availability of specific
      performance, injunctive relief or other equitable remedies.
	 
		6.3.	Valid Issuance of Common
      Stock. The Shares, when issued, sold
      and delivered in accordance with the terms hereof for the consideration
      expressed herein, will be duly and validly authorized and issued, fully
      paid and nonassessable and free of restrictions on transfer other than
      restrictions on transfer under this Agreement and applicable state and
      federal securities laws.
	 
		6.4.	Legal Proceedings and
      Orders. There is no action, suit,
      proceeding or investigation pending or threatened against Geron that
      questions the validity of this Agreement or the right of Geron to enter
      into this Agreement or to consummate the transactions contemplated hereby,
      nor is Geron aware of any basis for any of the foregoing. Geron is neither
      a party nor subject to the provisions of any order, writ, injunction,
      judgment or decree of any court or government agency or instrumentality
      that would affect the ability of Geron to enter into this Agreement or to
      consummate the transactions contemplated hereby.
	          	            	
	7.	REPRESENTATIONS AND
      ACKNOWLEDGMENTS OF COMPANY.
	 
		COMPANY hereby
      represents, warrants, acknowledges and agrees that:
	 
		7.1.	Investment. COMPANY is acquiring the Shares for COMPANY’s own
      account, and not directly or indirectly for the account of any other
      person. COMPANY is acquiring the Shares for investment and not with a view
      to distribution or resale thereof, except in compliance with the Act and
      any applicable state law regulating securities.
	 
		7.2.	Access to Information.
      COMPANY has consulted with its own
      attorney, accountant, or investment advisor as COMPANY has deemed
      advisable with respect to the investment and has determined its
      suitability for COMPANY. COMPANY has had the opportunity to ask questions
      of, and to receive answers from, appropriate executive officers of Geron
      with respect to the terms and conditions of the transactions contemplated
      hereby and with respect to the business, affairs, financial condition and
      results of operations of Geron. In connection with the transactions
      contemplated hereunder, Geron may disclose to COMPANY information which
      may constitute material, non-public information regarding Geron, and
      COMPANY agrees to maintain in confidence any such information; provided,
      however, such information shall not include information (a) that is or
      becomes part of the public domain, (b) that was in COMPANY’s possession
      without any obligation of confidentiality prior to the date Geron
      disclosed such information to COMPANY, or (c) that is supplied to COMPANY
      by a third party which is not subject to any restriction of
      confidentiality or non-disclosure. COMPANY has had access to such
      financial and other information as is necessary in order for COMPANY to
      make a fully informed decision as to investment in Geron, and has had the
      opportunity to obtain any additional information necessary to verify any
      of such information to which COMPANY has had access. COMPANY acknowledges
      that neither Geron nor any of its officers, directors, employees, agents,
      representatives, or advisors have made any representation or warranty
      other than those specifically expressed herein.
	 		
		7.3.	Business and Financial
      Expertise. COMPANY further represents and warrants
      that it has such business or financial expertise as to be able to evaluate
      its investment in Geron and purchase of the Shares.
	 		
		7.4.	Speculative Investment.
      COMPANY acknowledges that the investment in Geron
      represented by the Shares is highly speculative in nature and is subject
      to a high degree of risk of loss in whole or in part; the amount of such
      investment is within COMPANY’s risk capital means and is not so great in
      relation to COMPANY’s total financial resources as would jeopardize the
      personal financial needs of COMPANY in the event such investment were lost
      in whole or in part.


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		7.5.	Unregistered
      Securities. COMPANY acknowledges
      that:
	 
			7.5.1.	COMPANY must bear the economic
      risk of investment for an indefinite period of time because the Shares
      have not been registered under the Act and therefore cannot and will not
      be sold unless they are subsequently registered under the Act or an
      exemption from such registration is available. Geron has made no
      agreements, covenants or undertakings whatsoever to register any of the
      Shares under the Act, except as provided in Section 4 above. Geron has
      made no representations, warranties or covenants whatsoever as to whether
      any exemption from the Act, including, without limitation, any exemption
      for limited sales in routine brokers’ transactions pursuant to Rule 144
      under the Act, will become available and any such exemption pursuant to
      Rule 144, if available at all, will not be available unless: (i) a public
      trading market then exists in Geron’s common stock, (ii) Geron has
      complied with the information requirements of Rule 144, and (iii) all
      other terms and conditions of Rule 144 have been satisfied.
	 
			7.5.2.	Transfer of the Shares has not
      been registered or qualified under any applicable state law regulating
      securities and, therefore, the Shares cannot and will not be sold unless
      they are subsequently registered or qualified under any such act or an
      exemption therefrom is available. Geron has made no agreements, covenants
      or undertakings whatsoever to register or qualify any of the Shares under
      any such act. Geron has made no representations, warranties or covenants
      whatsoever as to whether any exemption from any such act will become
      available.
	 
			7.5.3.	COMPANY hereby certifies that it
      is an “Accredited
      Investor” as that term is defined
      in Rule 501 under the Act.
	          	            	              	
		7.6.	Authorization.
      COMPANY has full right, power,
      authority and capacity to enter into this Agreement and to consummate the
      transactions contemplated hereby and thereby and has taken all necessary
      action to authorize the execution, delivery and performance of this
      Agreement. Upon execution and delivery, this Agreement will constitute a
      valid and binding obligation of COMPANY enforceable against COMPANY in
      accordance with its terms, except as such enforceability may be limited by
      applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent
      transfer, liquidation or similar laws relating to, or affecting generally,
      the enforcement of creditor's rights and remedies or by other equitable
      principles of general application from time to time in
effect.
	 
	8.	TAX ADVICE.
      COMPANY acknowledges that COMPANY has
      not relied and will not rely upon Geron or Geron’s counsel with respect to
      any tax consequences related to the ownership, purchase, or disposition of
      the Shares. COMPANY assumes full responsibility for all such consequences
      and for the preparation and filing of all tax returns and elections which
      may or must be filed in connection with the Shares.
	 
	9.	NOTICES.
      Any notice or other communication
      required or permitted hereunder shall be in writing and shall be deemed to
      have been duly given on the date of delivery if delivered personally or by
      facsimile, or one day, not including Saturdays, Sundays, or national
      holidays, after sending if sent by national overnight delivery service, or
      five days, not including Saturdays, Sundays, or national holidays, after
      mailing if mailed by first class United States mail, certified or
      registered with return receipt requested, postage prepaid, and addressed
      as follows:



	To Geron at:  	Geron
      Corporation  
	  	230
      Constitution Drive  
	  	Menlo
      Park, California 94025  
	  	Attention: Senior Director, Legal  
	 	Telephone:
    		(650)
      473-7700  
	  	Facsimile:
    		(650)
      473-7750  
	    
	To COMPANY at:  	DP
      Clinical, Inc. 
	  	1803
      Research Boulevard, Suite 404 
	  	Rockville,
      Maryland 20850 
	  	Attention:
      Devindar Poonian 
	  	Telephone: 301-
      294-6226 
		Facsimile: 301-294-2233 




	10.	BINDING EFFECT.
      This Agreement shall be binding upon
      the heirs, legal representatives and successors of Geron and of
      COMPANY.
	          	
	11.	GOVERNING LAW.
      This Agreement shall be governed by and
      construed in accordance with the laws of the State of California.
    


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	12.	INVALID PROVISIONS.
      In the event that any provision of this
      Agreement is found to be invalid or otherwise unenforceable by a court or
      other tribunal of competent jurisdiction, such invalidity or
      unenforceability shall not be construed as rendering any other provision
      contained herein invalid or unenforceable, and all such other provisions
      shall be given full force and effect to the same extent as though the
      invalid and unenforceable provision was not contained herein.

	          	
	13.	COUNTERPARTS. This Agreement may be executed in any number of
      identical counterparts, each of which shall be deemed an original, but all
      of which together shall constitute one and the same instrument.
  
	 
	14.	AMENDMENTS. This Agreement or any provision hereof may be changed,
      waived, or terminated only by a statement in writing signed by the party
      against whom such change, waiver or termination is sought to be
      enforced.
	 
	15.	FUTURE
      COOPERATION. Each of the parties hereto
      agrees to cooperate at all times from and after the date hereof with
      respect to all of the matters described herein, and to execute such
      further assignments, releases, assumptions, amendments of the Agreement,
      notifications and other documents as may be reasonably requested for the
      purpose of giving effect to, or evidencing or giving notice of, the
      transactions contemplated by this Agreement.
	 
	16.	ENTIRE AGREEMENT.
      This Agreement and the Master Agreement
      constitute the entire agreement of the parties pertaining to the Shares
      and supersede all prior and contemporaneous agreements, representations,
      and understandings of the parties with respect
  thereto.


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     IN
WITNESS WHEREOF, the parties hereto have executed this Common Stock Purchase
Agreement as of the date first above written. 


	Geron Corporation  
	  
	  
	     /s/ David L.
      Greenwood  	 
	By: 
    		David
      L. Greenwood  
	Title: 		Executive Vice President and Chief 
    
	  		Financial Officer  
	  
	DP Clinical, Inc. 
    
	  
	  
	     /s/ Devinder
      Poonian  	 
	By: 
    		Devinder Poonian  
	Title: 	     	President and Chief Executive Officer 
      



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