COMMON STOCK PURCHASE AGREEMENT

A.

Geron and MPI are the parties to that certain Master Agreement dated as of December 12, 2003 (the “ Master Agreement ”), and related Services Agreement Addenda under which Geron and MPI have agreed that MPI will perform certain services on behalf of Geron on the terms set forth therein.

B.

Pursuant to the fifth amendment to the Master Agreement, dated April 22, 2009 (“Amendment No. 5”), Geron may pay for the price of services performed by MPI under the Master Agreement by delivery of shares of Geron’s Common Stock (the “ Shares ”).

C.

Geron has elected to make payment for such services performed pursuant to Amendment No. 5 through the delivery of Shares, pursuant to the terms and conditions of Amendment No. 5 and this Agreement.

1.

ISSUANCE OF SHARES; ADJUSTMENTS.

1.1.

As payment of the price specified in Amendment No. 5, Geron will issue and deliver certificates for 174,798 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 MPI one or more certificates representing all of the Shares, which Shares shall be issued in the name of MPI or its designee and in such denominations as MPI shall specify.

2.2.

Geron’s obligations to issue and deliver the stock certificate(s) representing the Shares to MPI at the Closing shall be subject to the following conditions, which may be waived by Geron:

2.2.1.

the covenants and obligations that MPI 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 MPI herein shall be true and correct in all material respects as of the Closing Date.

2.3.

MPI’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 MPI:

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 MPI; 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 . MPI 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 MPI 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, DATED AS OF APRIL 22, 2009. A COPY OF THE AGREEMENT CAN BE OBTAINED FROM THE SECRETARY OF GERON.”

3.2.

Limits on Sales . MPI 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 144A compliant transaction. MPI further agrees that it will not engage in short selling with respect to the Stock.

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 MPI. Geron agrees to diligently pursue making the Registration Statement effective. Geron will notify MPI of the effectiveness of the Registration Statement within one (1) business day of receiving notice from the Commission.

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 MPI receives an opinion of counsel from Geron, which counsel shall be reasonably acceptable to MPI, that the Shares may be sold under the provisions of Rule 144 without limitation as to volume, (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, or (v) the date all Shares may be sold at any time, without volume or manner of sale limitations pursuant to Rule 144 or any similar provision then in effect under the Act in the opinion of counsel to Geron, which counsel shall be reasonably acceptable to MPI.

4.3.

Geron, at its expense, shall furnish to MPI 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 MPI may reasonably request, in order to facilitate the public sale or other disposition of all or any of the Shares by MPI, provided, however, that the obligation of Geron to deliver copies of prospectuses or preliminary prospectuses to MPI shall be subject to the receipt by Geron of reasonable assurances from MPI that MPI 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.

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. MPI shall bear the cost of fees and expenses of MPI’s counsel.

4.5.

Geron will advise MPI 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 at the earliest possible moment if such stop order should be issued.

4.6.

With a view to making available to MPI the benefits of Rule 144 (or its successor rule) and any other rule or regulation of the Commission that may at the time permit MPI 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.

MPI 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 MPI 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 s