Exhibit 10.6

TRADEMARK AND LICENSE SECURITY AGREEMENT

This TRADEMARK AND LICENSE SECURITY AGREEMENT (this “Agreement”), dated as of
December 22, 2008, is by and between GTC BIOTHERAPEUTICS, INC. (“Grantor”) and
GENERAL ELECTRIC CAPITAL CORPORATION (“Grantee”).

W I T N E S S E T H:

WHEREAS, Grantor and Grantee entered into that certain Amended and Restated
Master Security Agreement, dated as of December 29, 2006 (as amended as of the
date hereof and as further amended, restated, supplemented or otherwise modified
from time to time, the “Security Agreement”);

WHEREAS, Grantor and Grantee desire to amend the Security Agreement, and have
entered or will enter into that certain Consent and Amendment No. 3 to Amended
and Restated Master Security Agreement dated as of December 22, 2008 (as it may
be amended, restated, supplemented or otherwise modified from time to time, the
“Security Agreement Amendment”);

WHEREAS, in order to induce Grantee to enter into the Security Agreement
Amendment and to continue to make the loans and other credit accommodations as
provided for in the Security Agreement, Grantor has agreed to pledge the
Trademark Collateral (as defined below) to Grantee in accordance herewith, in
each case to secure the Indebtedness (as defined in the Security Agreement); and

WHEREAS, this Agreement is required by the terms of the Security Agreement
Amendment.

NOW, THEREFORE, in consideration of these premises and other good and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged, the
parties hereto agree as follows:

1. Defined Terms.

(i) Unless otherwise defined herein, capitalized terms used herein which are
defined in the Security Agreement shall have the meanings specified in the
Security Agreement.

(ii) The words “hereof”, “herein”, and “hereunder” and words of like import when
used in this Agreement shall refer to this Agreement as a whole and not to any
particular provision of this Agreement, and Section and schedule references are
to this Agreement unless otherwise specified.

(iii) All terms defined in this Agreement in the singular shall have comparable
meanings when used in the plural, and vice versa, unless otherwise specified.

(iv) “Default” means the occurrence of either of the following events: (a) any
default by Grantor under the terms of the Security Agreement or any other Debt
Document; or (b) any Event of Default.

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2. Security Interest in Trademarks. As security for prompt payment in full of
all of the Indebtedness, Grantor hereby grants to Grantee a second priority
security interest, having priority over all other security interests (other than
the security interest in favor of LFB (as defined below)) in all of Grantor’s
now owned or existing and hereafter acquired or arising (collectively, the
“Trademark Collateral”):

(i) trademarks, registered trademarks and trademark applications, trademark
registrations, trade names, service marks, registered service marks, service
mark applications, and service mark registrations (except for “intent-to-use”
applications for trademark or service mark registrations prior to the filing of
an amendment alleging use or a verified statement of use), including, without
limitation, the registered trademarks, trademark applications, registered
service marks and service mark applications and registrations listed on
Schedule A, and (a) all renewals thereof, (b) all income, royalties, damages and
payments now and hereafter due and/or payable with respect thereto, including,
without limitation, payments under all licenses entered into in connection
therewith and damages and payments for past or future infringements or dilutions
thereof, (c) the right to sue for past, present and future infringements and
dilutions thereof, and (d) all of Grantor’s rights corresponding thereto
throughout the world (all of the foregoing registered trademarks, trademark
applications, registered service marks and service mark applications, together
with the items described in clauses (a)-(d) in this paragraph 2(i), being
sometimes hereinafter individually and/or collectively referred to, alone or in
conjunction with non-U.S. Trademarks identified in Schedule C, as the
“Trademarks”);

(ii) the goodwill of Grantor’s business connected with and symbolized by the
Trademarks;

(iii) license agreements with any other party in connection with any Trademarks
or such other party’s trademarks, registered trademarks, trademark applications,
trademark registrations, trade names, service marks, registered service marks,
service mark applications and service mark registrations, whether Grantor is a
licensor or licensee under any such license agreement, including, but not
limited to, the license agreements listed on Schedule B, and the right upon the
occurrence and during the continuance of a Default to use the foregoing in
connection with the enforcement of Grantee’s rights under the Security Agreement
(all of the foregoing being hereinafter referred to collectively as the
“Licenses”). Notwithstanding the foregoing provisions of this Section 2, the
Licenses shall not include any license agreement which by its terms prohibits
(which prohibition is enforceable under applicable law) the grant of the
security interest contemplated by this Agreement for so long as such prohibition
continues; it being understood that upon request of Grantee, Grantor will in
good faith use reasonable efforts to obtain consent for the creation of a
security interest in favor of Grantee in Grantor’s rights under such license
agreement (excluding any license of non-custom computer software); and

(iv) Non-U.S. Trademarks and Licenses, including, without limitation, those
listed on Schedule C.

3. Restrictions on Future Agreements. Grantor will not, without Grantee’s prior
written consent, enter into any agreement, including, without limitation, any
license agreement, which is inconsistent with this Agreement, and Grantor
further agrees that it will not take any

 

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action, and will not permit any action to be taken by others subject to its
control, including licensees, or fail to take any action, which would affect the
validity or enforcement of the rights transferred to Grantee, under this
Agreement or any other Debt Document or the rights associated with those
Trademarks which are necessary or desirable in the operation of Grantor’s
business.

4. New Trademarks. Grantor represents and warrants that the Trademarks and
Licenses listed on Schedules A, B and C, respectively, include all of the
trademark applications and registrations and Licenses to any Trademarks which
Licenses are material to the operation of Grantor’s business (excluding any
license of non-custom computer software) now owned or held by Grantor. If, prior
to the termination of this Agreement, Grantor shall (i) obtain rights to any new
Trademark or Licenses or (ii) become entitled to the benefit of any new or
existing Trademark or License, the provisions of Section 2 shall automatically
apply thereto, and Grantor shall give to Grantee prompt written notice thereof.
Grantor hereby authorizes Grantee to modify this Agreement by (a) amending
Schedules A, B or C, as the case may be, to include any Trademarks or Licenses
which are described under this Section 4, and (b) filing, in addition to and not
in substitution for, this Agreement, a short form of this Agreement containing
on Schedules A, B or C thereto, as the case may be, such Trademarks or Licenses,
as the case may be, which are described under this Section 4. Notwithstanding
the foregoing, Grantor agrees that Grantee’s security interest shall extend to
all of the collateral listed in Section 2 and this Section 4, regardless of
whether Grantee actually amends Schedules A, B or C, respectively.

5. Royalties. Grantor hereby agrees that the use by Grantee of the Trademarks
and Licenses as authorized hereunder shall be coextensive with Grantor’s rights
thereunder and with respect thereto and without any liability for royalties or
other related charges from Grantee to Grantor.

6. Nature and Continuation of Grantee’s Security Interest. This Agreement is
made for collateral security purposes only. This Agreement shall create a
continuing security interest in the Trademarks and the Licenses and shall remain
in full force and effect until the Indebtedness has been paid in full and the
Security Agreement terminated, at such time the rights granted to Grantee
hereunder shall also terminate.

7. Right to Inspect; Further Assignments and Security Interests. Grantee shall
have the right, in accordance with the terms and conditions of the Security
Agreement, to inspect the premises of Grantor and to examine the books, records
and operations of Grantor relating to the Trademarks. Grantor agrees not to sell
or assign its respective interests in, or grant any license under (other than
granting any license in the ordinary course of business), the Trademarks without
the prior written consent of Grantee.

8. Duties of Grantor. Grantor shall have the duty to the extent desirable in the
conduct of Grantor’s business and consistent with Grantor’s current business
practices or Grantor’s reasonable business judgment: (i) to prosecute diligently
any trademark applications or registrations or service mark applications or
registrations that are part of the Trademarks pending as of the date hereof or
thereafter until the termination of this Agreement; (ii) to make applications
for trademarks and service marks as Grantor deems appropriate; (iii) to take
reasonable steps to preserve and maintain all of Grantor’s rights in the
trademark and service

 

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mark applications and trademark and service mark registrations that are part of
the Trademarks; (iv) to take appropriate actions and to file certain documents
to prevent or to cure the abandonment, lapse, or cancellation of any application
or registration of the Trademarks, or to prevent or to cure liability to any
claim of abandonment for non-use or otherwise of the Trademarks, except as
agreed to by the parties; and (v) obtain any consents, waivers or agreements
necessary to enable Grantee to exercise its remedies with respect to any and all
Trademark Collateral. Any expenses incurred in connection with the foregoing
shall be borne by Grantor. Grantor shall not abandon any trademark or service
mark which is the subject of a registration or application therefor and which is
or shall be, in the Grantor’s reasonable business judgment necessary or
economically desirable to the operation of Grantor’s business. Grantor agrees to
retain an experienced trademark attorney for the filing and prosecution of all
such applications and other proceedings. Grantee shall have no duty with respect
to the Trademarks and Licenses. Without limiting the generality of the
foregoing, Grantee shall not be under any obligation to take any steps necessary
to preserve rights in the Trademarks or Licenses against any other parties, but
may do so at its option during the continuance of a Default, and all expenses
incurred in connection therewith shall be for the sole account of Grantor and
added to the Indebtedness secured thereby.

9. Grantee’s Right to Sue; Limited License. From and after the occurrence and
during the continuance of a Default, Grantee shall have the right, but shall not
be obligated, upon prior written notice to Grantor, to bring suit to enforce the
Trademarks and the Licenses, and, if Grantee shall commence any such suit,
Grantor shall, at the request of Grantee, do any and all lawful acts and execute
any and all proper documents required by Grantee in aid of such enforcement.
Grantor shall, upon demand, promptly reimburse and indemnify Grantee for all
reasonable attorneys’ fees and other costs and expenses incurred by Grantee in
the exercise of its rights under this Section 9 (including, without limitation,
the allocated cost of in-house counsel). If, for any reason whatsoever, Grantee
is not reimbursed with respect to the costs and expenses referred to in the
preceding sentence, such costs and expenses shall be added to the Indebtedness
secured hereby. Grantor hereby grants to Grantee a license with respect to all
Trademarks and Licenses owned or used by Grantor to the extent necessary to
enable Grantee, effective upon the occurrence of any Default, to realize on the
Trademarks and Licenses and any successor or assign to enjoy the benefits of the
Trademarks and Licenses. This license shall inure to the benefit of Grantee and
its successors, assigns and transferees, whether by voluntary conveyance,
operation of law, assignment, transfer, foreclosure, deed in lieu of foreclosure
or otherwise. Such license is granted free of charge, without requirement that
any monetary payment whatsoever including, without limitation, any royalty or
license fee, be made to any Grantor or any other Person by Grantee or any other
Person.

10. Waivers. No course of dealing between Grantor and Grantee, and no failure to
exercise or delay in exercising on the part of Grantee any right, power or
privilege hereunder or under the Security Agreement or other Debt Documents
shall operate as a waiver of any of Grantee’s rights, powers or privileges. No
single or partial exercise of any right, power or privilege hereunder or under
the Security Agreement or other Debt Documents shall preclude any other or
further exercise thereof or the exercise of any other right, power or privilege.

11. Grantee’s Exercise of Rights and Remedies Upon Default. Notwithstanding
anything set forth herein to the contrary, it is hereby expressly agreed that
upon the occurrence

 

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and during the continuance of a Default, Grantee may exercise any of the rights
and remedies provided in this Agreement or any of the other Debt Documents.
Without limiting the generality of the foregoing, Grantor acknowledges and
agrees that (i) the Trademarks and Licenses comprise a portion of the Collateral
and Grantee shall have the right to exercise its rights under the Security
Agreement with respect to the Trademarks and Licenses to the same extent as with
respect to all other items of Collateral described therein, and (ii) from and
after the occurrence and during the continuation of a Default, Grantee or its
nominee may use the Trademarks and Licenses to assemble, manufacture, sell,
prepare for sale or take possession of the Collateral, or for any other purpose
in connection with the conduct of Grantor’s business. Any proceeds of any of the
Trademark Collateral may be applied by the Grantee to the payment of expenses in
connection with the enforcement of Grantee’s rights and remedies hereunder and
in connection with the Trademark Collateral, including, without limitation,
reasonable attorneys’ fees and legal expenses, and any balance of such proceeds
may be applied by Grantee toward the payment of such of the Indebtedness, and in
such order of application, as Grantee may from time to time elect (and, after
payment in full of all Indebtedness, any excess shall be delivered to Grantor or
as a court of competent jurisdiction shall direct).

12. Severability. If any provision hereof is held to be illegal or
unenforceable, such provision shall be fully severable, and the remaining
provisions hereof shall remain in full force and effect and shall not be
affected by such provision’s severance. Furthermore, in lieu of any such
provision, there shall be added automatically as a part of this Agreement a
legal and enforceable provision as similar in terms to the severed provision as
may be possible.

13. Modification. This Agreement cannot be altered, amended or modified in any
way, except as specifically provided in Sections 2 and 4 hereof or by a writing
signed by the parties hereto.

14. Cumulative Remedies; Power of Attorney. All of Grantee’s rights and remedies
with respect to the Trademarks and the Licenses, whether established hereby, by
any other agreements or by law, shall be cumulative and may be exercised
singularly or concurrently. Grantor hereby irrevocably appoints Grantee as
Grantor’s attorney-in-fact, with full authority in the place and stead of
Grantor and in the name of Grantor or otherwise to carry out the acts described
below. Upon the occurrence and during the continuance of a Default, Grantor
hereby authorizes Grantee to, in its sole discretion, (i) endorse Grantor’s name
on all applications, documents, papers and instruments necessary or desirable
for Grantee in the use of the Trademarks and the Licenses, (ii) take any other
actions with respect to the Trademarks and the Licenses as Grantee deems is in
its best interest, (iii) grant or issue any exclusive or non-exclusive license
with respect to the Trademarks to anyone on commercially reasonable terms, and
(iv) assign, pledge, convey or otherwise transfer title in or dispose of the
Trademarks and the Licenses to anyone on commercially reasonable terms. Grantor
hereby ratifies all that such attorney-in-fact shall lawfully do or cause to be
done by virtue hereof. This power of attorney is coupled with an interest and
shall be irrevocable until this Agreement shall have been terminated pursuant to
Section 6 hereof. Grantor acknowledges and agrees that this Agreement is not
intended to limit or restrict in any way the rights and remedies of Grantee
under the Security Agreement or other Debt Documents, but rather is intended to
facilitate the exercise of such rights and remedies. Grantee shall have, in
addition to all other rights and remedies given it by the terms of this
Agreement, all rights and remedies allowed by law and the rights and remedies

 

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of a secured party under the Uniform Commercial Code as enacted in any
jurisdiction in which, respectively, either (x) the Trademarks may be located or
deemed located or (y) the Licenses were granted.

15. Binding Effect; Benefits. This Agreement shall be binding upon Grantor and
its successors and assigns, and shall inure to the benefit of Grantee and its
nominees, successors and assigns. The successors and assigns of Grantor shall
include, without limitation, a receiver, trustee or debtor-in-possession of or
for Grantor; provided, however, that Grantor shall not voluntarily assign its
obligations hereunder without the prior written consent of Grantee.

16. CHOICE OF LAW; WAIVER OF JURY TRIAL; SERVICE OF PROCESS. THE VALIDITY,
INTERPRETATION AND ENFORCEMENT OF THIS AGREEMENT SHALL BE GOVERNED BY THE LAWS
OF THE STATE OF CONNECTICUT. GRANTOR AND GRANTEE HEREBY WAIVE ANY RIGHT TO A
TRIAL BY JURY IN ANY ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS
AGREEMENT. GRANTOR HEREBY IRREVOCABLY WAIVES PERSONAL SERVICE OF PROCESS AND
CONSENTS TO SERVICE OF PROCESS BY CERTIFIED OR REGISTERED MAIL, RETURN RECEIPT
REQUESTED. IN NO EVENT WILL GRANTEE BE LIABLE FOR LOST PROFITS OR OTHER SPECIAL
OR CONSEQUENTIAL DAMAGES.

17. Notices. Except as otherwise herein provided, any notice or other
communication required hereunder shall be in writing (messages sent by e-mail or
other electronic transmission (other than by telecopier) shall not constitute a
writing, however any signature on a document or other writing that is
transmitted by e-mail or telecopier shall constitute a valid signature for
purposes hereof), and shall be deemed to have been validly served, given or
delivered when received by the recipient if hand delivered, sent by commercial
overnight courier or sent by facsimile, or three (3) Business Days after deposit
in the United States mail, with proper first-class postage prepaid and addressed
to the party at its address and/or facsimile number set forth in the Security
Agreement, or to such other address as either party shall specify to the other
in writing from time to time.

18. Section Headings. The Section headings herein are for convenience of
reference only, and shall not affect in any way the interpretation of any of the
provisions hereof.

19. Execution in Counterparts. This Agreement may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of this Agreement by telefacsimile shall be equally as effective as
delivery of a manually executed counterpart of this Agreement. Any party
delivering an executed counterpart of this Agreement by telefacsimile or
electronic transmission shall also deliver a manually executed counterpart of
this Agreement, but the failure to deliver a manually executed counterpart shall
not affect the validity, enforceability, and binding effect of this Agreement.

20. Right of Recordal of Security Interest. Grantee shall have the right, but
not the obligation, at the expense of Grantor, to record this Agreement in the
United States Patent and

 

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Trademark Office and with such other United States or foreign recording
authorities deemed reasonable and proper by Grantee. Grantee shall advise
Grantor of such recordals, and Grantor shall comply with all formalities and
execute all documents deemed reasonable and proper by Grantee in connection
therewith. Upon satisfaction in full of the Indebtedness and termination of the
Security Agreement, Grantor shall have the right to effect recordal of such
satisfaction or termination at the expense of Grantor in the United States
Patent and Trademark Office and with such other United States and foreign
recording authorities deemed reasonable and proper by Grantor, and Grantee shall
comply with all formalities and execute all documents deemed reasonable and
proper by Grantor in connection therewith. Grantee and Grantor shall cooperate
to effect all such recordals hereunder. Grantor shall reimburse Grantee for all
reasonable expenses (including, without limitation, filing fees, translation
fees, fees related to retention of local patent clerks and local attorneys)
incurred by Grantee relating to such recordals within fifteen (15) days of
making such reimbursement request and providing documentation evidencing such
expenses to Grantor.

21. Intercreditor Agreement. Notwithstanding anything herein to the contrary,
the liens and security interest granted to Grantee pursuant to this Agreement
and the exercise of any right or remedy by Grantee hereunder are subject to the
provisions of that certain Subordination and Intercreditor Agreement dated as of
December 22, 2008 (the “Intercreditor Agreement”) by and among Grantor, Grantee
and LFB Biotechnologies, a société anonyme established under the laws of France
(“LFB”). In the event of any conflict between the terms of the Intercreditor
Agreement and this Agreement, the terms of the Intercreditor Agreement shall
govern and control.

[SIGNATURE PAGE FOLLOWS]

 

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Signature Page to Trademark and License Security Agreement

IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement on the
day and year first above written.

 

GRANTOR:  

GTC BIOTHERAPEUTICS, INC.,

a Massachusetts corporation

  By:  

/s/ John B. Green

  Name:   John B. Green   Title:   Senior Vice President, Chief Financial
Officer and Treasurer

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Signature Page to Trademark and License Security Agreement

 

GRANTEE:  

GENERAL ELECTRIC CAPITAL CORPORATION,

a Delaware corporation

  By:  

/s/ Jason M. Dufour

  Name:   Jason M. Dufour   Title:   Duly Authorized Signatory

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SCHEDULE A

to Trademark and License Security Agreement

TRADEMARKS

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SCHEDULE B

to Trademark and License Security Agreement

LICENSES

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SCHEDULE C

to Trademark and License Security Agreement

NON-U.S. TRADEMARKS AND LICENSES