Document:

Exhibit 10.1
                                                                    ------------

                                   AMENDMENT
                                       TO
                   SECOND AMENDED AND RESTATED LOAN AGREEMENT

This AMENDMENT TO SECOND AMENDED AND RESTATED LOAN AGREEMENT (this "Amendment")
is made and entered into as of the 24th day of October, 2007, by and among
NATIONAL DENTEX CORPORATION, a Massachusetts corporation ("Dentex"), its
Subsidiaries listed on the signature page(s) hereto (together with Dentex,
collectively the "Borrowers"), and BANK OF AMERICA, N.A. (the "Bank").
Capitalized terms used herein without definition shall have the meaning ascribed
to them in the Loan Agreement (as defined below).

WHEREAS, the Borrowers and the Bank are parties to that certain Second Amended
and Restated Loan Agreement dated as of November 7, 2006, as amended by that
certain Loan Modification Agreement dated as of March 29, 2007 (as the same may
be further amended and in effect from time to time, the "Loan Agreement"),
pursuant to which the Bank has extended credit to the Borrowers on the terms set
forth therein;

WHEREAS, the Borrowers have requested the Bank to amend the Minimum Consolidated
EBITDA covenant, set forth in Section 6(v) of the Loan Agreement and the Maximum
Consolidated Total Funded Debt to Consolidate EBITDA covenant set forth in
Section 6(u) of the Loan Agreement;

WHEREAS, the Bank is willing to grant and make such amendments to the Loan
Agreement on the terms and conditions set forth herein;

NOW, THEREFORE, in consideration of the foregoing, and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereby agree as follows:

     1. Amendment to ss.6(u) of the Loan Agreement. Section 6(u) of the Loan
Agreement is hereby amended by deleting such Section in its entirety and
replacing it with the following:

     "(u) Maximum Consolidated Total Funded Debt to Consolidated EBITDA. As of
the end of any fiscal quarter, the ratio of (a) Consolidated Total Funded Debt
as of such date to (b) Consolidated EBITDA for the period of four (4)
consecutive fiscal quarters ending on the date of calculation (i) prior to and
including June 30, 2008, shall not exceed 2.5:1.0 and (ii) thereafter shall not
exceed 2.0:1.0."

     2. Amendment to ss.6(v) of the Loan Agreement. Section 6(v) of the Loan
Agreement is hereby amended by deleting such Section in its entirety and
replacing it with the following:

     "6(v) Minimum Consolidated EBITDA. For the period of four (4) consecutive
fiscal quarters then ended, the Borrowers shall not permit Consolidated EBITDA
to be less than (i) $15,3000,000 on December 31, 2006, (ii) $16,300,000 on March
31, 2007, (iii) $16,300,000 on June 30, 2007, (iv) $17,000,000 on September 30,
2007, (v) $17,500,000 on December 31, 2007, (vi) $18,000,000 on March 31, 2008,
(vii) $18,500,000 on June 30, 2008, (viii) $19,000,000 on September 30, 2008,
(ix) $19,500,000 on December 31, 2008, (x) $20,000,000 on March 31, 2009, (xi)
$20,500,000 on June 30, 2009, (xii) $21,000,000 on September 30, 2009, and
(xiii) $21,500,000 on the last day of each fiscal quarter thereafter."

     3. Effective Date and Conditions to Effectiveness. This Amendment shall be
effective as of June 30, 2007, upon the receipt by the Bank of a counterpart
signature page to this Amendment duly executed and delivered by each of the
Borrowers.

     4. Representations and Warranties. Each of the Borrowers represents and
warrants as follows:

<PAGE>

     (a) The execution and delivery of this Agreement and the performance of
each of this Amendment and the Loan Agreement, as amended as of the date hereof,
are within the corporate power and authority of such Borrower and have been or
will be authorized by proper corporate proceedings, and do not (i) require any
consent or approval of the stockholders of such Borrower, (ii) contravene any
provision of the charter documents or by-laws of such Borrower or any law, rule
or regulation applicable to such Borrower, or (iii) contravene any provision of,
or constitute an event of default or event which, but for the requirement that
time elapse or notice be given, or both, would constitute an event of default
under, any other material agreement, instrument or undertaking binding on such
Borrower.

     (b) This Amendment and the Loan Agreement, as amended as of the date
hereof, and all of the terms and provisions hereof and thereof are the legal,
valid and binding obligations of such Borrower enforceable in accordance with
their respective terms except as limited by bankruptcy, insolvency,
reorganization, moratorium or other laws affecting the enforcement of creditors'
rights generally, and except as the remedy of specific performance or of
injunctive relief is subject to the discretion of the court before which any
proceeding therefor may be brought.

     (c) Except with respect to filings with the U.S. Securities and Exchange
Commission, the execution, delivery and performance of this Amendment, as of the
date hereof, do not require any approval or consent of, or filing or
registration with, any governmental or other agency or authority, or any other
party.

     (d) Each of the representations and warranties of the Borrowers contained
in the Loan Agreement (after giving effect to this Amendment) or in any document
or instrument delivered pursuant to or in connection with the Loan Agreement are
true and correct in all material respects as of the date hereof with the same
effect as if made on and as of the date hereof (except to the extent of changes
resulting from transactions contemplated or permitted by the Loan Agreement and
changes occurring in the ordinary course of business which singly or in the
aggregate do not create a Material Adverse Effect, and to the extent that such
representations and warranties relate expressly to an earlier date).

     (e) After giving effect to this Amendment, no Default or Event of Default
under the Loan Agreement has occurred and is continuing.

     5. Ratification, etc. Except as expressly amended hereby, the Loan
Agreement, the other Loan Documents and all documents, instruments and
agreements related thereto are hereby ratified and confirmed in all respects and
shall continue in full force and effect. Each Borrower hereby affirms all of its
obligations under the Loan Agreement and under each of the other Loan Documents
to which it is a party and hereby affirms its absolute and unconditional promise
to pay to the Bank the Loans and all other amounts due under the Loan Agreement
(as amended hereby) and the other Loan Documents. This Amendment and the Loan
Agreement shall hereafter be read and construed together as a single document,
and all references in the Loan Agreement or any related agreement or instrument
to the Loan Agreement shall hereafter refer to the Loan Agreement as amended by
this Amendment.

     6. Governing Law. This Amendment and the rights and obligations of the
parties hereunder shall be deemed to be a document executed under seal and shall
be construed and interpreted in accordance with the laws of the Commonwealth of
Massachusetts (excluding the laws applicable to conflicts or choice of law).

     7. Delivery By Facsimile Or Other Electronic Transmission. This Amendment,
to the extent signed and delivered by means of a facsimile machine or other
electronic transmission in which the actual signature is evident, shall be
treated in all manner and respects as an original agreement or instrument and
shall be considered to have the same binding legal effect as if it were the
original signed version thereof delivered in person. At the request of any party
hereto, each other party hereto or thereto shall re-execute original forms
hereof and deliver them to all other parties. No party hereto shall raise the
use of a facsimile machine or other electronic transmission in which the actual
signature is evident to deliver a signature or the fact that any signature or
agreement or instrument was transmitted or communicated through the use of a
facsimile machine or other electronic transmission in which the actual signature
is evident as a defense to the formation of a contract and each party forever
waives such defense.

<PAGE>

     8. Counterparts. This Amendment may be executed in any number of
counterparts and by different parties hereto on separate counterparts, each of
which when so executed and delivered shall be an original, but all of which
counterparts taken together shall be deemed to constitute one and the same
instrument.

                     [Remainder of page intentionally blank]

<PAGE>

     IN WITNESS WHEREOF, the undersigned have duly executed this Amendment as of
the date first set forth above.

NATIONAL DENTEX CORPORATION

By: /s/ Richard F. Becker, Jr.
    --------------------------
Name:  Richard F. Becker, Jr.
Title: Executive Vice President and Treasurer

GREEN DENTAL LABORATORIES, INC.,

By: /s/ Richard F. Becker, Jr.
    --------------------------
Name:  Richard F. Becker, Jr.
Title: Assistant Treasurer

KELLER GROUP, INCORPORATED

By: /s/ Richard F. Becker, Jr.
    --------------------------
Name:  Richard F. Becker, Jr.
Title: Assistant Treasurer and Assistant Secretary

KELLER LABORATORIES, INCORPORATED - MIDWEST

By: /s/ Richard F. Becker, Jr.
    --------------------------
Name:  Richard F. Becker, Jr.
Title: Assistant Treasurer and Assistant Secretary

KELLER LABORATORIES, INC. - SOUTHEAST

By: /s/ Richard F. Becker, Jr.
    -------------------------
Name:  Richard F. Becker, Jr.
Title: Assistant Treasurer and Assistant Secretary

<PAGE>

Acknowledged and Agreed:
------------------------

BANK OF AMERICA, N.A.,
as the Bank

    By: /s/ Richard J. MacDonald
        ------------------------
    Name:  Richard J. MacDonald
    Title: Vice PresidentEXHIBIT 4.1

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "SECURITIES ACT"), OR ANY STATE SECURITIES LAWS, AND HAS BEEN
ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO, OR IN CONNECTION WITH, THE SALE
OR DISTRIBUTION THEREOF. NO SUCH SALE OR DISPOSITION MAY BE EFFECTED WITHOUT AN
EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL,
REASONABLY SATISFACTORY TO THE COMPANY, THAT SUCH REGISTRATION IS NOT REQUIRED
UNDER THE SECURITIES ACT.

Warrant No.:  LAZ-300                           Number of Shares:  25,000

Date of Issuance: November 5, 2004

                                GERON CORPORATION

                         COMMON STOCK WARRANT AGREEMENT

Geron Corporation (the "Company"), for value received, hereby certifies that
Lazard Freres & Co. LLC or their registered assigns (in accordance with Section
3 below) (the "Registered Holder"), is entitled, subject to the terms set forth
below, to purchase from the Company, at any time after the date hereof and on or
before the Expiration Date (as defined in Section 5 below), up to 25,000 shares
of Common Stock of the Company, as adjusted from time to time pursuant to the
terms of this Common Stock Warrant Agreement ("Warrant"), at a purchase price of
$6.12 per share. The shares purchasable upon exercise of this Warrant are
hereinafter referred to as the "Warrant Stock." The exercise price per share of
Warrant Stock is hereinafter referred to as the "Purchase Price."

   1.  EXERCISE.

       (a) MANNER OF EXERCISE. This Warrant may be exercised by the Registered
Holder, in whole or in part, by surrendering this Warrant, with the purchase
form appended hereto as Exhibit A duly executed by such Registered Holder or by
such Registered Holder's duly authorized attorney-in-fact, at the principal
office of the Company, or at such other office or agency as the Company may
designate, accompanied by payment in full by cash, check or wire transfer of the
Purchase Price payable in respect of the number of shares of Warrant Stock
purchased upon such exercise.

           In addition to and without limiting the rights of the holder hereof
under the terms hereof, this Warrant may be exercised by being exchanged in
whole or in part at any time or from time to time prior to its expiration for a
number of shares of Common Stock having an aggregate fair market value on the
date of such exercise equal to the difference between (x) the fair market value
of the number of shares of Common Stock subject to this Warrant designated by
the holder hereof on the date of exercise and (y) the aggregate purchase price
hereunder for such shares in effect at such time. The following diagram
illustrates how many shares would then be issued upon exercise pursuant to this
Section:

        Let     FMV =   Fair market value per share at date of exercise.
                PSP =   Per share purchase price at date of exercise.
                N   =   Number of shares covered by the Warrant.
                X   =   Number of shares issued after exercise.

                X = (FMV)(N) - (PSP)(N)
                    -------------------
                                FMV

                                       1
<PAGE>

     No payment of cash or any other consideration to the Company shall be
     required from the holder of this Warrant in connection with any exercise of
     this Warrant by exchange pursuant to this Section. Such exchange shall be
     effective immediately prior to the close of business on the day on which
     this Warrant shall have been surrendered for cancellation and a written
     request from the holder hereof that the exchange pursuant to this Section
     be made or at such later as may be specified by such request. No fractional
     shares arising out of the above formula for determining the number of
     shares issuable in such exchange shall be issued, and the Company shall in
     lieu thereof make payment to the holder hereof of cash in the amount of
     such fraction multiplied by the fair market value of a share of Common
     Stock on the date of the exchange. For the purposes of this Section, the
     "fair market value" of any number of shares of Common Stock shall be
     calculated on the basis of the closing price of the Common Stock as
     reported on the Nasdaq National Market exchange.

       (b) EFFECTIVE TIME OF EXERCISE. The exercise of this Warrant shall be
deemed to have been effected immediately prior to the close of business on the
day on which this Warrant shall have been surrendered to the Company, with
payment of the applicable Purchase Price, as provided in Section 1(a) above. At
such time, the person or persons in whose name or names any certificates for
Warrant Stock shall be issuable upon such exercise as provided in Section 1(c)
below shall be deemed to have become the holder or holders of record of the
Warrant Stock represented by such certificates.

       (c) DELIVERY TO REGISTERED HOLDER. As soon as practicable after the
exercise of this Warrant, and in any event within ten (10) business days
thereafter, the Company, at its expense, will cause to be issued in the name of,
and delivered to, the Registered Holder, or as such Registered Holder (upon
payment by such Registered Holder of any applicable transfer taxes) may direct,
a certificate or certificates for the number of shares of Warrant Stock to which
such Registered Holder shall be entitled. If the Registered Holder exercises in
part and only purchases a portion of the shares covered by this Warrant, the
Company shall execute and deliver a new Warrant of like tenor for the balance of
the shares of Common Stock of the Company covered by this Warrant.

   2.  CERTAIN ADJUSTMENTS.

       (a) SALES, MERGERS AND CONSOLIDATIONS. If at any time there shall be a
sale, merger or consolidation of the Company with another corporation or a
transfer or sale of all or substantially all of the capital stock or assets of
the Company, then, as a part of such merger or consolidation, lawful provision
shall be made so that the Registered Holder shall thereafter be entitled to
receive upon exercise of this Warrant during the period specified in this
Warrant and upon payment of the Purchase Price, the number of shares of stock or
other securities or property of the Company or the successor corporation
resulting from such merger or consolidation, to which a holder of the Common
Stock deliverable upon exercise of this Warrant would have been entitled under
the provisions of the agreement in such merger or consolidation if this Warrant
had been exercised immediately before that merger or consolidation. In any such
case, appropriate adjustment (as reasonably determined in good faith by the
Company's Board of Directors) shall be made in the application of the provisions
of this Warrant with respect to the rights and interests of the Registered
Holder after the merger or consolidation to the end that the provisions of this
Warrant (including adjustment of the Purchase Price then in effect and the
number of shares of Warrant Stock) shall be applicable after that event, as near
as reasonably may be, in relation to any shares or other property deliverable
after that event upon exercise of this Warrant.

       (b) SPLITS, SUBDIVISIONS AND DIVIDENDS. In the event the Company should
at any time or from time to time fix a record date for the effectuation of a
split or subdivision of the outstanding shares of Common Stock or the
determination of the holders of Common Stock entitled to receive a dividend or
other distribution payable in additional shares of Common Stock or other
securities or rights convertible into, or entitling the holder thereof to
receive directly or indirectly, additional shares of Common Stock (hereinafter
referred to as the "Common Stock Equivalents") without payment of any
consideration by such holder for the additional shares of Common Stock or Common
Stock Equivalents (including the additional shares of Common Stock issuable upon
conversion or exercise thereof), then, as of such record date (or the date of
such distribution, split or subdivision if no record date is fixed), the per
share Purchase Price shall be appropriately decreased and the number of shares
of Warrant Stock shall be appropriately increased in proportion to such increase
(or potential increase) of outstanding shares.

                                       2
<PAGE>

       (c) COMBINATION OF SHARES. If the number of shares of Common Stock
outstanding at any time after the date hereof is decreased by a combination of
the outstanding shares of Common Stock, the per share Purchase Price shall be
appropriately increased and the number of shares of Warrant Stock shall be
appropriately decreased in proportion to such decrease in outstanding shares.

       (d) ADJUSTMENT CERTIFICATE. When any adjustment is required to be made in
the securities issuable upon exercise of this Warrant, the Company shall mail to
the Registered Holder a certificate setting forth a statement of the facts
requiring such adjustment. Such certificate shall also set forth the kind and
amount of stock or other securities or property into which this Warrant shall be
exercisable following the occurrence of any of the events specified in this
Section 2.

   3.  TRANSFER RESTRICTIONS; REPRESENTATIONS.

       (a) The Registered Holder of this Warrant acknowledges that this Warrant
and the Warrant Stock have not been registered under the Securities Act, and
agrees not to sell, pledge, distribute, offer for sale, transfer or otherwise
dispose of this Warrant or any Warrant Stock issued upon its exercise in the
absence of (i) an effective registration statement under the Securities Act as
to this Warrant or such Warrant Stock and registration or qualification of this
Warrant or such Warrant Stock or (ii) an opinion of counsel, reasonably
satisfactory to the Company, that such registration and qualification are not
required. Notwithstanding the foregoing, the Registered Holder has a right to
request registration of this Warrant and the Warrant Stock under the Securities
Act at the time of and in connection with registered public offering of the
Company's stock, at the Company's expense, and the Company will not unreasonably
deny such request. The Company shall notify the Registered Holder within 20 days
of such registered public offering to allow the Registered Holder to request
registration. This Warrant is not transferable without the prior written consent
of the Company except to an affiliate of the Registered Holder. It is understood
and agreed that the preceding sentence does not apply to, or limit the sale,
pledge, distribution, offers for sale, transfer or other disposition of Warrant
Stock after any exercise thereof pursuant to Section 1 hereof.

       (b) The Registered Holder hereby further represents and warrants to the
Company with respect to the issuance of the Warrant and the purchase of the
Warrant Stock as follows:

           (i) PURCHASE ENTIRELY FOR OWN ACCOUNT. This Warrant is issued to the
Registered Holder in reliance upon such Registered Holder's representation to
the Company, which by such Registered Holder's execution of this Warrant such
Registered Holder hereby confirms, that the Warrant and the Warrant Stock will
be acquired for investment for such Registered Holder's own account, not as a
nominee or agent, and not with a view to the resale or distribution of any part
thereof, and that such Registered Holder has no present intention of selling,
granting any participation in, or otherwise distributing the same.

           (ii) KNOWLEDGE AND EXPERIENCE; ABILITY TO BEAR ECONOMIC RISKS. The
Registered Holder has such knowledge and experience in financial and business
matters that it is capable of evaluating the merits and risks of the investment
contemplated by this Warrant and such party is able to bear the economic risk of
its investment in the Company (including a complete loss of its investment). The
Registered Holder is an "accredited investor" as defined by Rule 501 of the
Securities Act.

           (iii) RESALE. The Registered Holder understands that the Warrant
being issued hereunder and the Warrant Stock to be purchased hereunder are
characterized as "restricted securities" under the federal securities laws
inasmuch as they are being acquired from the Company in a transaction not
involving a public offering and that under such laws and applicable regulations,
such securities may be resold without registration under the Securities Act only
in certain circumstances. In this regard, the Registered Holder represents that
it is familiar with Rule 144 under the Securities Act, and understands the
resale limitations imposed thereby and by the Securities Act.

                                       3
<PAGE>

           (iv) LEGENDS. The Registered Holder acknowledges that all stock
certificates representing shares of stock issued to the Registered Holder upon
exercise of this Warrant may, if such Warrant Stock is not registered under the
Securities Act, have affixed thereto a legend substantially in the following
form:

              (x) "THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY STATE
SECURITIES LAWS. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, HYPOTHECATED
OR OTHERWISE TRANSFERRED IN THE ABSENCE OF A REGISTRATION STATEMENT IN EFFECT
WITH RESPECT TO THE SECURITIES UNDER SUCH SECURITIES ACT OR AN OPINION OF
COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT
REQUIRED OR UNLESS SOLD PURSUANT TO AN EXEMPTION TO SUCH SECURITIES ACT."

              (y) Any legend required by the laws of any state in which the
securities will be issued.

       (c) Subject to the provisions of Section 3(a) hereof, this Warrant and
all rights hereunder are transferable in whole or in part upon surrender of the
Warrant with a properly executed assignment (in the form of Exhibit B hereto) at
the principal office of the Company.

       (d) The Company will maintain a register containing the names and
addresses of the Registered Holder(s) of this Warrant. Any Registered Holder may
change such Registered Holder's address as shown on the warrant register by
written notice to the Company requesting such change.

       (e) The Company hereby represents and warrants to the Registered Holder
as follows:

           (i) The Company is a corporation validly existing and in good
standing under the laws of the State of Delaware.

           (ii) The Company has requisite corporate right, power and authority
(including the due authorization by all necessary corporate action) to enter
into this Warrant and to perform its obligations hereunder without the need for
the consent of any other person; and this Warrant has been duly authorized,
executed and delivered and constitutes legal, valid and binding obligations of
the Company enforceable against it in accordance with the terms hereof. The
execution, delivery and performance of this Warrant by the Company do not
contravene or violate any laws, rules or regulations applicable to it.

           (iii) The Company has taken such corporate action as is necessary or
appropriate to enable it to perform its obligations hereunder, including, but
not limited to, the issuance, sale and delivery of the Warrant.

           (iv) The Warrant Stock, when issued and paid for in compliance with
the provisions of this Warrant, will be validly issued, fully paid and
non-assessable.

   4.  NO IMPAIRMENT. The Company will not, by amendment of its charter or
through reorganization, consolidation, merger, dissolution, sale of assets or
any other voluntary action, avoid or seek to avoid the observance or performance
of any of the terms of this Warrant, but will assist in the carrying out of all
such terms and in the taking of all such action as may be necessary or
appropriate in order to fulfill its obligations hereunder.

   5.  TERMINATION. This Warrant (and the right to purchase securities upon
exercise hereof) shall terminate upon the fifth anniversary of the Date of
Issuance (the "Expiration Date").

   6. NOTICES OF CERTAIN TRANSACTIONS. In the event that:

       (a) the Company shall take a record of the holders of its Common Stock
(or other stock or securities at the time deliverable upon the exercise of this
Warrant) for the purpose of entitling or enabling them to receive any dividend
or other distribution, or any right to subscribe for, purchase or otherwise
acquire any shares of stock of any class or any other securities or property, or
to receive any other right; or

                                       4
<PAGE>

       (b) the Company shall effect any consolidation or merger of the Company
with or into another corporation (other than a consolidation or merger in which
the Company is the surviving entity), or any transfer of all or substantially
all of the assets of the Company, or

       (c) the Company voluntarily or involuntarily dissolves, liquidates or
winds-up its business or affairs, then, and in each such case, the Company will
mail or cause to be mailed to the Registered Holder of this Warrant a notice
specifying, as the case may be, (i) the date on which a record is to be taken
for the purpose of such dividend, distribution or right, and stating the amount
and character of such dividend, distribution or right, and (ii) the effective
date on which such reorganization, reclassification, consolidation, merger,
transfer, dissolution, liquidation or winding-up is expected to take place, and
the record date for determining shareholders entitled to vote thereon. Such
notice shall be mailed at least ten (10) calendar days prior to the record date
or effective date for the event specified in such notice.

   7.  RESERVATION OF STOCK. The Company shall at all times reserve and keep
available, solely for the issuance and delivery upon the exercise of this
Warrant, such shares of Warrant Stock or other stock or securities, as from time
to time shall be issuable upon the exercise of this Warrant.

   8.  EXCHANGE OF WARRANTS. Upon the surrender by the Registered Holder of any
Warrant, properly endorsed, to the Company at the principal office of the
Company, the Company will, subject to the provisions of Section 3(a) hereof,
issue and deliver, at the Company's expense, a new warrant in a form
substantially similar to this Warrant, in the name of such Registered Holder or
as such Registered Holder (upon payment by such Registered Holder of any
applicable transfer taxes) may direct, calling in the aggregate on the face
thereof for the number of shares of Common Stock called for on the face of the
Warrant so surrendered.

   9.  REPLACEMENT OF WARRANTS. Upon receipt of evidence reasonably satisfactory
to the Company of the loss, theft, destruction or mutilation of this Warrant
and, in the case of loss, theft or destruction, upon delivery of an indemnity
agreement, with surety if reasonably required, in an amount reasonably
satisfactory to the Company, or, in the case of mutilation, upon surrender and
cancellation of this Warrant, the Company will issue, in lieu thereof, a new
warrant in a form substantially similar to this Warrant.

   10. MAILING OF NOTICES. Any notice required or permitted by this Warrant
shall be in writing and shall be deemed sufficient upon receipt, when delivered
personally or by a nationally-recognized delivery service (such as Federal
Express or UPS) or confirmed facsimile, or forty-eight (48) hours after being
deposited in the U.S. mail as certified or registered mail with postage prepaid,
if such notice is addressed to the party to be notified at such party's address
or facsimile number as set forth below or as subsequently modified by written
notice.

   11. NO RIGHTS AS STOCKHOLDER. Until the exercise of this Warrant, the
Registered Holder of this Warrant shall not have or exercise any rights by
virtue hereof as a stockholder of the Company (including without limitation the
right to notification of stockholder meetings or the right to receive any notice
or other communication concerning the business or affairs of the Company).

   12. NO FRACTIONAL SHARES. No fractional shares of Common Stock will be issued
in connection with any exercise hereunder.

   13. AMENDMENT OR WAIVER. Any term of this Warrant may be amended or waived
only by an instrument in writing signed by the Company and the Registered
Holder.

                                       5
<PAGE>

   14. HEADINGS. The headings in this Warrant are for purposes of reference only
and shall not limit or otherwise affect the meaning of any provision of this
Warrant.

   15. SUCCESSORS AND ASSIGNS. The terms and provisions of this Warrant shall
inure to the benefit of, and be binding upon, the Company and the Registered
Holder and their respective permitted successors and assigns (in the case of the
Registered Holder, in accordance with Section 3(a) hereof).

   16. GOVERNING LAW. This Warrant shall be governed, construed and interpreted
in accordance with the laws of the State of California, without giving effect to
principles of conflicts of law thereof.

GERON CORPORATION                       REGISTERED HOLDER

By:  /s/ David L. Greenwood             By:  /s/ Jason R. Bernhard
    -----------------------                  ---------------------
Name:    David L. Greenwood             Name:    Jason Bernhard
Title:   Chief Financial Officer        Title:   Managing Director
Address: Geron Corporation              Address: Lazard Freres & Co. LLC
         230 Constitution Drive                  30 Rockefeller Plaza
         Menlo Park, CA 94025                    New York, NY 10020

Dated:                                  Dated:   November 19, 2004

                                       6
<PAGE>

                                    EXHIBIT A

                                  PURCHASE FORM

To:   GERON CORPORATION

Date: ___________________

      The undersigned, pursuant to the provisions set forth in the attached
Warrant, hereby irrevocably elects to purchase shares of the Common Stock
covered by such Warrant [and herewith makes payment of $___________,
representing the full purchase price for such shares at the price per share
provided for in such Warrant or any adjustment certificate delivered pursuant to
section 2(d) of the Warrant] or [pursuant to the net exercise provisions set
forth in section 1(a) of the Warrant].

The undersigned hereby affirms and acknowledges the investment representations
and warranties made in the Warrant are true and correct as of the date hereof,
and accepts such shares subject to the restrictions set forth in the Warrant,
copies of which are available from the Secretary of the Company.

Signature:  _______________________________________

Name:

Title:

Address:

                                       7
<PAGE>

                                    EXHIBIT B

                                 ASSIGNMENT FORM

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

NAME OF ASSIGNEE        ADDRESS                 No. OF SHARES

Signature:  _______________________________________

Witness:  ________________________________________

Dated:  _____________________

                                       8

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00131-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00131-of-00352.parquet"}]]