FIFTH AMENDMENT TO LEASE

                                                                     EXHBIT 10.1



                           FIFTH AMENDMENT TO LEASE

      THIS FIFTH AMENDMENT TO LEASE ("Fifth Amendment") is made this 19th day of
March, 2008 (the "Effective Date"),   between DAVID D. BOHANNON   ORGANIZATION,   a
California corporation, herein referred to as "Landlord", and GERON CORPORATION,
a Delaware corporation, herein referred to as "Tenant".


                                   WITNESSETH:

      WHEREAS,   Landlord and Tenant entered into a Lease entitled "Business Park
Lease" dated January 20, 1993, for certain demised   premises   located at 194-200
Constitution Drive, Menlo Park,   California,   as more particularly   described in
said Lease, and

      WHEREAS,   the Lease has been   amended by a First   Amendment to Lease dated
July 26,   1993,   a Second   Amendment   to Lease dated   February 22, 1994, a Third
Amendment to Lease dated March 25, 1996,   and a Fourth   Amendment to Lease dated
March 23, 2004 (the "Fourth Amendment") (the Lease, as previously amended by the
foregoing amendments, is herein referred to as the "Lease"), and

      WHEREAS,   the Lease is scheduled to expire on July 31, 2008,   and Landlord
and Tenant desire to make certain amendments to the Lease and extend the demised
term of the Lease, all as more particularly set out hereinbelow.

      NOW, THEREFORE, in consideration of the covenants and conditions contained
herein, Landlord and Tenant agree to amend the Lease as follows:

      1.   The   demised   term of the   Lease is   hereby   extended   four (4)   years
commencing August 1, 2008, and the demised term shall expire on July 31, 2012 at
11:59 p.m.

      2. Effective as of the Effective Date, Section 1.3. of the Lease (Tenant's
option to extend the demised   term of the Lease),   which was   inserted   into the
Lease in   paragraph 2 of the Fourth   Amendment,   and Section   2.8. of the Lease,
which was inserted into the Lease in paragraph 4 of the Fourth Amendment,   shall
be deemed void and of no further force or effect,   as the parties have agreed to
extend the demised term of the Lease   pursuant to the   provisions   of this Fifth
Amendment.

      3. Base rent payable pursuant to Sections 2.1. and 2.2. of the Lease shall
be payable   during the extended   term as follows:   for the period from August 1,
2008,   to and   including   July 31,   2012,   base rent shall be the amount of Four
Hundred    Seventeen    Thousand   Two   Hundred    Eighty   Two   and   48/100   Dollars
($417,282.48)   per annum,   payable in twelve (12) equal monthly   installments of
Thirty   Four    Thousand    Seven   Hundred    Seventy   Three   and   54/100    Dollars
($34,773.54).

      4. In addition to the base rent set forth in Section 2.1 of the Lease,   as
revised   hereinabove,   Tenant shall continue to pay all items of additional rent
pursuant to the terms of the Lease.

      5. Tenant hereby   receives a new option to further extend the demised term
of the Lease;   therefore,   the   following   new Section 1.3. is inserted into the
Lease as of the Effective Date:


                                      -1-
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            "Section   1.3.   Provided   that Tenant is not,   at the time   Landlord
      receives Tenant's written notice to exercise the following option, and has
      not been, in default   under any of the terms and   conditions of the Lease,
      which   default has not been cured within the   applicable   cure periods set
      forth in Article 13 of the Lease,   Tenant   shall have the option to extend
      the demised   term of the Lease for one (1)   additional   period of four (4)
      years upon the following terms and conditions:

            A. Tenant shall   exercise   the option by written   notice to Landlord
      given no later than one hundred   eighty   (180) days,   nor earlier than two
      hundred seventy (270) days, prior to the expiration of the demised term;

            B. The option term will commence on August 1, 2012, and shall extend
      for a period of four (4) years, up to and including July 31, 2016;

            C. There   shall be no further   options to extend,   there shall be no
      Landlord   inducement,   and   Landlord   shall not be required to perform any
      improvements   in the demised   premises or the building   prior to or during
      the option term;

            D. The option to extend may only be exercised by Geron   Corporation,
      provided that Geron   Corporation   may exercise the option on behalf of its
      sublessee if Geron   Corporation   has   subleased   any or all of the demised
      premises and Landlord has consented to such sublease. The option cannot be
      transferred   nor   can   it be   exercised   by   Geron   Corporation   if   Geron
      Corporation has assigned its rights under this Lease to a third party.

            E. The then current   payments for additional   rent shall continue to
      be adjusted   during the option   term   pursuant   to the   provisions   of the
      Lease;

            F. The base rent for each year of the option term shall   (subject to
      the   provisions   hereof) equal the Fair M