QuickLinks -- Click here to rapidly navigate through this document

Exhibit 10.3

Execution Copy

GTC BIOTHERAPEUTICS, INC.

REGISTRATION RIGHTS AGREEMENT

dated as of July 30, 2003

--------------------------------------------------------------------------------

GTC BIOTHERAPEUTICS, INC.

REGISTRATION RIGHTS AGREEMENT

        This Registration Rights Agreement (this "Agreement") is entered into as
of July 30, 2003 by and among GTC Biotherapeutics, Inc., a Massachusetts
corporation (the "Company"), and the investors signatory hereto (each, a
"Purchaser" and, collectively, the "Purchasers").

RECITALS

        A. The Company and the Purchasers entered into that certain Securities
Purchase Agreement of even date herewith among the Company and the Purchasers
(the "Securities Purchase Agreement"), and, upon the terms and subject to the
conditions of the Securities Purchase Agreement pursuant to exemptions from
registration afforded by Rule 506 promulgated under the Securities Act of 1933,
as amended (the "Securities Act"), and Section 4(2) thereunder, the Purchasers
have severally agreed to purchase the respective number of shares (collectively,
the "Shares") of the common stock, par value $0.01 per share, of the Company
(the "Common Stock") and Common Stock Purchase Warrants to purchase shares of
Common Stock (collectively, the "Warrant Shares") as is set forth on the
Schedule of Purchasers attached hereto as Exhibit A (the Shares, the Common
Stock Purchase Warrants and the Warrant Shares are herein referred to together
as the "Securities").

        B. To induce the Purchasers to execute and deliver the Securities
Purchase Agreement, the Company has agreed to provide certain registration
rights to the Purchasers under the Securities Act, and applicable state
securities laws.

        NOW, THEREFORE, in consideration of the promises and the mutual
covenants contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and each
of the Purchasers hereby agree as follows:

        1.    Certain Definitions.    As used in this Agreement, the following
terms shall have the following meanings:

        (a)   "Business Day" means any day other than Saturday, Sunday or any
other day on which commercial banks in The City of New York are required by law
to remain closed.

        (b)   "Investor" means each Purchaser and any transferee or assignee
thereof to whom Placement Agent or a Purchaser assigns its rights under this
Agreement and who agrees to become bound by the provisions of this Agreement in
accordance with Section 9 of this Agreement, and any subsequent transferee or
assignee thereof to whom a transferee or assignee assigns its rights under this
Agreement and who agrees to become bound by the provisions of this Agreement in
accordance with Section 9 of this Agreement.

        (c)   "Person" means an individual, a limited liability company, a
partnership, a joint venture, a corporation, a trust, an unincorporated
organization or association and governmental or any department or agency
thereof.

        (d)   "Prospectus" means the prospectus included in a Registration
Statement (including, without limitation, a prospectus that includes any
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon Rule 430A promulgated under the
Securities Act), as amended or supplemented by any prospectus supplement, with
respect to the terms of the offering of any portion of the Registrable
Securities covered by the Registration Statement, and all other amendments and
supplements to the Prospectus, including post-effective amendments, and all
material incorporated by reference or deemed to be incorporated by reference in
such Prospectus.

        (e)   "register," "registered," and "registration" means a registration
effected by preparing and filing one or more Registration Statements (as defined
below) in compliance with the Securities Act and pursuant to Rule 415 under the
Securities Act or any successor rule providing for offering securities on a
continuous or delayed basis ("Rule 415"), and the declaration or ordering of

--------------------------------------------------------------------------------

effectiveness of such Registration Statements by the United States Securities
and Exchange Commission (the "Commission").

        (f)    "Registrable Securities" means (i) the Shares and the Warrant
Shares and (ii) any shares of common stock of any entity issued in respect of
the Shares or Warrant Shares as a result of a merger, consolidation, sale of
assets, sale or exchange of capital stock or other similar transaction, provided
that shares of capital stock that are Registrable Securities shall cease to be
Registrable Securities upon (1) any sale pursuant to a Registration Statement or
Rule 144 under the Securities Act or eligibility for sale under Rule 144(k) or
(2) any sale or transfer to any Person which by virtue of Section 9 of this
Agreement is not entitled to the rights provided by this Agreement.

        (g)   "Registration Statement" means a registration statement or
registration statements of the Company filed under the Securities Act and
covering Registrable Securities, including (in each case) the Prospectus,
amendments and supplements to such registration statement or Prospectus,
including pre- and post-effective amendments, all exhibits thereto, and all
material incorporated by reference or deemed to be incorporated by reference in
such registration statement.

        (h)   "Trading Day" means (i) a day on which the Common Stock is traded
on a Trading Market, or (ii) if the Common Stock is not listed on a Trading
Market, a day on which the Common Stock is traded on the over-the-counter
market, as reported by the OTC Bulletin Board, or (iii) if the Common Stock is
not quoted on the OTC Bulletin Board, a day on which the Common Stock is quoted
in the over-the-counter market as reported by the National Quotation Bureau
Incorporated (or any similar organization or agency succeeding its functions of
reporting prices); provided, that in the event that the Common Stock is not
listed or quoted as set forth in (i), (ii) or (iii) hereof, then Trading Day
shall mean a Business Day.

        (i)    "Trading Market" means the following markets or exchanges on
which the Common Stock is listed or quoted for trading on the date in question:
the American Stock Exchange, the New York Stock Exchange, the Nasdaq National
Market or the Nasdaq SmallCap Market.

        (j)    Capitalized terms used herein and not otherwise defined herein
shall have the respective meanings set forth in the Securities Purchase
Agreement.

        2.    Registration    

        (a)    Mandatory Registration.    The Company shall use its reasonable
efforts to prepare and, as soon as practicable but in no event later than thirty
(30) days after the Closing Date (the "Filing Deadline"), file with the
Commission a Registration Statement on Form S-3 covering the resale of all of
the Registrable Securities. In the event that Form S-3 is unavailable for such a
registration, the Company shall use such other form as is available for such a
registration, subject to the provisions of Section 2(c) of this Agreement. The
Registration Statement and shall contain (except if otherwise agreed by the
holders of at least a majority of the Registrable Securities) the "Plan of
Distribution" attached hereto as Annex A. The Company shall use reasonable
efforts to have the Registration Statement declared effective by the Commission
as soon as practicable, but not later than ninety (90) days after the Closing
Date (the "Effectiveness Deadline"); provided, however, that if the Commission
reviews the Registration Statement and requires the Company to make
modifications thereto, then the Effectiveness Deadline shall be extended to not
later than one hundred twenty (120) days after the Closing Date.

        (b)    Allocation of Registrable Securities.    The number of
Registrable Securities included in any Registration Statement shall be allocated
pro rata among the Investors based on the number of Registrable Securities held
by each Investor at the time the Registration Statement covering such initial
number of Registrable Securities or increase thereof is declared effective by
the Commission. In the event that an Investor sells or otherwise transfers any
of such Investor's Registrable Securities, each transferee shall be allocated
the portion of the then remaining number of Registrable Securities

2

--------------------------------------------------------------------------------

included in such Registration Statement allocable to the transferor. In no event
shall the Company include any securities other than Registrable Securities on
any Registration Statement without the prior written consent of the Investors
holding at least a majority of the Registrable Securities. The Company shall not
file any registration statement other than the Registration Statement herein
required to be filed until after the date the initial Registration Statement
required to be filed hereunder has been declared effective by the Commission.

        (c)    Ineligibility for Form S-3.    If Form S-3 is not available for
the registration of the resale of Registrable Securities hereunder or the
Company is not permitted by the Securities Act or the Commission to use
Form S-3, then the Company shall (i) register the resale of the Registrable
Securities on another appropriate form reasonably acceptable to the holders of
at least a majority of the Registrable Securities and (ii) undertake to register
the Registrable Securities on Form S-3 as soon as such form is available;
provided, however, that the Company shall maintain the effectiveness of the
Registration Statement then in effect until such time as a Registration
Statement on Form S-3 covering all of the Registrable Securities has been
declared effective by the Commission.

        (d)    Sufficient Number of Securities Registered.    In the event the
number of shares registered under a Registration Statement filed pursuant to
Section 2(a) of this Agreement is for any reason insufficient to cover all of
the Registrable Securities or all of an Investor's allocated portion of the
Registrable Securities pursuant to Section 2(b) of this Agreement, the Company
shall amend the Registration Statement, or file a new Registration Statement (on
the short form available therefor, if applicable), or both, so as to cover all
of the Registrable Securities, as soon as practicable, but in no event later
than fifteen (15) days after the necessity therefor arises. The Company shall
use its reasonable efforts to cause such amendment or new Registration Statement
to become effective as soon as practicable following the filing thereof.

        (e)    Liquidated Damages.    If (i) the initial Registration Statement
required to be filed pursuant to Section 2(a) is not filed on or prior to the
Filing Deadline, or (ii) the initial Registration Statement required to be filed
pursuant to Section 2(a) is not declared effective by the Commission on or
before the Effectiveness Deadline, or (iii) after the date first declared
effective by the Commission and prior to the expiration of the Registration
Period, the Company invokes Blackout Periods, as such term is defined in
Section 3(m), that in the aggregate exceed Twenty Five (25) Trading Days (any
such failure or breach to be referred to as an "Event" and for the purposes of
clauses (i) or (ii) the date on which such Event occurs, or for purposes of
clause (iii) the date on which such Twenty Five (25) Trading Day period is
exceeded, being referred to as an "Event Date") then in addition to any other
rights available to the Investors: (x) on each such Event Date, the Company
shall pay to each Investor an amount in cash as liquidated damages and not as a
penalty, equal to 1.5% of the aggregate purchase price paid by the original
Investor pursuant to the Purchase Agreement for any Registrable Securities then
held by such Investor; and (y) on each monthly anniversary of each such Event
Date (if the applicable Event shall not have been cured by such date) until the
applicable Event is cured, the Company shall pay to each Investor an amount in
cash as liquidated damages and not as a penalty, equal to 1.5% of the aggregate
purchase price paid by the original Investor pursuant to the Purchase Agreement
for any Registrable Securities then held by such Investor. The liquidated
damages pursuant to the terms hereof shall apply on a pro rata basis for any
portion of a month prior to the cure of an Event.

        3.    Related Obligations.    At such time as the Company is obligated
to file a Registration Statement with the Commission pursuant to Section 2 of
this Agreement, the Company will use reasonable efforts to effect the
registration of all of the Registrable Securities in accordance with the
intended method of disposition thereof and, pursuant thereto, the Company shall
have the following obligations:

        (a)   The Company shall promptly prepare and file with the Commission a
Registration Statement with respect to all of the Registrable Securities (but in
no event later than the applicable Filing

3

--------------------------------------------------------------------------------

Deadline) and use its reasonable efforts to cause such Registration Statement
relating to all of the Registrable Securities required to be covered thereby to
become effective as soon as practicable after such filing (but in no event later
than the applicable Effectiveness Deadline). The Company shall, subject to the
terms of this Agreement, keep each Registration Statement effective pursuant to
Rule 415 at all times until the earliest of (i) the date as of which all of the
Investors (other than any Investors who are "affiliates" of the Company as such
term is used in Rule 144(k) promulgated under the Securities Act) may sell all
of the Registrable Securities without restriction pursuant to Rule 144(k) (or
the successor rule thereto) promulgated under the Securities Act, (ii) the five
(5) year anniversary of the Closing Date or (iii) the date on which all of the
Investors shall have sold all of the Registrable Securities (the "Registration
Period"), which Registration Statement, as of its filing and effective dates and
each day thereafter (including all amendments or supplements thereto, as of
their respective filing and effective dates and each day thereafter), shall not
contain any untrue statement of a material fact or omit to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and the prospectus contained in such Registration Statement, as of
its filing date and each day thereafter (including all amendments and
supplements thereto, as of their respective filing dates and each day
thereafter), shall not contain any untrue statement of a material fact or omit
to state a material fact required to be stated thereon, or necessary to make the
statements therein, in light of the circumstances in which they were made, not
misleading. Not less than two Trading Days prior to the filing of a Registration
Statement or any related Prospectus or any amendment or supplement thereto that
contains information that is inconsistent in any material respect with Annex A
hereto, the Company shall furnish to the Investors copies of all such documents
proposed to be filed which documents will be subject to the review of such
Investors. The Company shall not file the Registration Statement or any such
Prospectus or any amendments or supplements thereto to which the Investors
holding a majority of the Registrable Securities shall reasonably object in good
faith.

        (b)   Subject to Section 3(m) of this Agreement, the Company shall
prepare and file with the Commission such amendments (including post-effective
amendments) and supplements to the Registration Statement and the prospectus
used in connection with such Registration Statement, which prospectus is to be
filed pursuant to Rule 424 (or any successor rule thereto) promulgated under the
Securities Act, as may be necessary to keep such Registration Statement
effective at all times during the Registration Period, and, during such period,
comply with the provisions of the Securities Act. In the case of amendments and
supplements to a Registration Statement and the prospectus used in connection
with such Registration Statement that are required to be filed pursuant to this
Agreement (including pursuant to this Section 3(b)) by reason of the Company
filing a report on Form 10-K, Form 10-Q or Form 8-K or any analogous report
under the Securities Exchange Act of 1934, as amended, and the rules and
regulations thereunder, or any similar successor statute (the "Exchange Act"),
the Company shall have incorporated such report by reference into such
Registration Statement, if applicable, or shall file such amendments or
supplements with the Commission on the same day on which the Exchange Act report
is filed that created the requirement for the Company to amend or supplement
such Registration Statement and prospectus.

        (c)   The Company shall furnish to each Investor whose Registrable
Securities are included in any Registration Statement, without charge to such
Investor, (i) upon the effectiveness of each Registration Statement, such number
of copies of the prospectus included in such Registration Statement and all
amendments and supplements thereto as such Investor may reasonably request, and
(ii) such other documents, including copies of such Registration Statement and
any preliminary or final prospectus, as such Investor may reasonably request
from time to time in order to facilitate the disposition of the Registrable
Securities.

        (d)   Subject to Section 3(m) of this Agreement, the Company shall use
reasonable efforts to (i) promptly register and qualify, unless an exemption
from registration and qualification applies, the resale of the Registrable
Securities under such other securities or "blue sky" laws of all applicable

4

--------------------------------------------------------------------------------

jurisdictions in the United States as any holder of Registrable Securities
reasonably requests in writing, (ii) promptly prepare and file in those
jurisdictions, such amendments (including post-effective amendments) and
supplements to such registrations and qualifications as may be necessary to
maintain the effectiveness thereof during the Registration Period,
(iii) promptly take such other actions as may be reasonably necessary to
maintain such registrations and qualifications in effect at all times during the
Registration Period, and (iv) promptly take all other actions reasonably
necessary or advisable to qualify the Registrable Securities for sale in such
jurisdictions; provided, however, that the Company shall not be required in
connection therewith or as a condition thereto to file a general consent to
service of process in any such jurisdiction, except in such jurisdictions where
the Company is then subject to service of process. The Company shall promptly
notify each Investor who holds Registrable Securities of the receipt by the
Company of any notification with respect to the suspension of the registration
or qualification of any of the Registrable Securities for sale under the
securities or "blue sky" laws of any jurisdiction in the United States or its
receipt of notice of the initiation or threatening of any proceeding for such
purpose.

        (e)   Notwithstanding anything to the contrary set forth herein, as
promptly as practicable after becoming aware of such event, the Company shall
notify each Investor in writing of the happening of any event as a result of
which (i) the Registration Statement or any amendment or supplement thereto, as
then in effect, includes an untrue statement of a material fact or omission to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading or (ii) the prospectus related to such
Registration Statement or any amendment or supplement thereto includes an untrue
statement of a material fact or omission to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading, and, subject to
Section 3(m) of this Agreement, promptly prepare a supplement or amendment to
such Registration Statement and prospectus to correct such untrue statement or
omission, and deliver such number of copies of such supplement or amendment to
each Investor as such Investor may reasonably request. The Company shall also
promptly notify each Investor in writing (1) when a prospectus and each
prospectus supplement or amendment thereto has been filed, and when a
Registration Statement and each amendment (including post-effective amendments)
and supplement thereto has been declared effective by the Commission, (2) of any
request by the Commission for amendments or supplements to a Registration
Statement or related prospectus or related information, and (3) of the Company's
reasonable determination that an amendment (including any post-effective
amendment) or supplement to a Registration Statement or prospectus (other than
the filing of a report under the Exchange Act) would be appropriate (subject to
Section 3(m)) hereof).

        (f)    Subject to Section 3(m) of this Agreement, the Company shall use
reasonable efforts to (i) prevent the issuance of any stop order or other
suspension of effectiveness of a Registration Statement, or the suspension of
the qualification of any of the Registrable Securities for sale in any
jurisdiction, and (ii) if such an order or suspension is issued, obtain the
withdrawal of such order or suspension at the earliest practicable moment and
notify each holder of Registrable Securities of the issuance of such order and
the resolution thereof or its receipt of notice of the initiation or threat of
any proceeding for such purpose.

        (g)   Except for the information set forth on Exhibit A to the
Securities Purchase Agreement, the Company shall hold in confidence and not make
any disclosure of information concerning an Investor provided to the Company
unless (i) disclosure of such information is necessary to comply with United
States federal or state securities laws, (ii) the disclosure of such information
is necessary to avoid or correct a misstatement or omission in any Registration
Statement, prospectus or any amendment or supplement thereto, (iii) the release
of such information is ordered pursuant to a subpoena or other final,
non-appealable order from a court or governmental body of competent
jurisdiction, or (iv) such information has been made generally available to the
public other than by disclosure in violation of this Agreement or any other
agreement. The Company agrees that it shall, upon learning that disclosure of

5

--------------------------------------------------------------------------------

such information concerning an Investor is sought in or by a court or
governmental body of competent jurisdiction or through other means, unless
ordered or requested by the Commission or other governmental authority not to do
so, give prompt written notice to such Investor and allow such Investor, at the
Investor's expense, to undertake appropriate action to prevent disclosure of, or
to obtain a protective order for, such information.

        (h)   The Company shall use its reasonable efforts to (i) cause all the
Registrable Securities to be listed on each securities exchange or automated
quotation system on which securities of the same class or series issued by the
Company are then listed, or (ii) if the Company is unsuccessful in satisfying
the preceding clause (i) or clause (i) does not apply because the securities of
such class or series are not listed on any exchange or automated quotation
system, to secure the inclusion for quotation on the Nasdaq SmallCap Market for
such Registrable Securities and, without limiting the generality of the
foregoing, to arrange for at least two market makers to register with the
National Association of Securities Dealers, Inc. as such with respect to such
Registrable Securities. In addition, the Company shall provide a transfer agent
and registrar for all of the Registrable Securities not later than the effective
date of the Registration Statement. The Company shall pay all fees and expenses
in connection with satisfying its obligation under this Section 3(h).

        (i)    In connection with any sale or transfer of Registrable Securities
pursuant to a Registration Statement, the Company shall cooperate with the
Investors who hold Registrable Securities being offered and, to the extent
applicable, facilitate the timely preparation and delivery of certificates (not
bearing any restrictive legend) representing the Registrable Securities to be
offered pursuant to a Registration Statement and enable such certificates to be
in such denominations or amounts, as the case may be, as the Investors may
reasonably request, and, registered in such names as the Investors may request.

        (j)    If requested by an Investor, the Company shall (i) as soon as
practicable, incorporate in each prospectus supplement or post-effective
amendment to the Registration Statement such information as an Investor
reasonably requests to be included therein relating to the sale and distribution
of Registrable Securities, (ii) as soon as practicable, make all required
filings of such prospectus supplement or post-effective amendment after being
notified of the matters to be incorporated in such prospectus supplement or
post-effective amendment, and (iii) as soon as practicable, supplement or make
amendments to any Registration Statement and prospectus if reasonably requested
by an Investor holding any Registrable Securities.

        (k)   The Company shall comply with all applicable rules and regulations
of the Commission in connection with any registration hereunder.

        (l)    Within two (2) Business Days after a Registration Statement is
ordered effective by the Commission, the Company shall deliver to the transfer
agent for the Registrable Securities (with copies to the Investors whose
Registrable Securities are included in such Registration Statement) confirmation
that such Registration Statement has been declared effective by the Commission.

6

--------------------------------------------------------------------------------

        (m)  Notwithstanding anything to the contrary herein, at any time after
a Registration Statement has been declared effective by the Commission, the
Company may delay the disclosure of material non-public information concerning
the Company if the disclosure of such information at the time is not, in the
good faith judgment of the Board of Directors of the Company, in the best
interests of the Company (a "Blackout Period"); provided, however, that the
Company shall promptly (i) notify the Investors of the existence of material
non-public information giving rise to a Blackout Period (provided that the
Company shall not disclose the content of such material non-public information
to the Investors) and the date on which the Blackout Period will begin, and
(ii) notify the Investors of the date on which the Blackout Period ends;
provided further, that no single Blackout Period shall exceed thirty
(30) consecutive calendar days, the aggregate of all of the Blackout Period
during any three hundred sixty-five (365) day period shall not exceed an
aggregate of forty-five (45) days and the first day of any Blackout Period must
be at least two (2) trading days after the last day of any prior Blackout Period
(any Blackout Period complying with the foregoing being an "Allowable Blackout
Period"). For purposes of determining the length of a Blackout Period, the
Blackout Period shall be deemed to begin on and include the date the Investors
receive the notice referred to in clause (i) and shall end on and include the
later of the date the Investors receive the notice referred to in clause (ii)
and the date on which the Investors may again utilize the Registration Statement
and the Prospectus thereunder to sell Registrable Securities; provided, however,
that no Blackout Period shall be longer than an Allowable Blackout Period. The
provisions of Section 3(f) of this Agreement shall not be applicable during the
period of any Allowable Blackout Period. Upon expiration of the Blackout Period,
the Company shall again be bound by the first sentence of Section 3(e) of this
Agreement. Any Blackout Period that exceeds the limitation set forth in
Section 2(e) shall be subject to liquidated damages to the extent provided
therein.

        4.    Obligations of the Investors.    

        (a)   A reasonable time prior to the first anticipated filing date of a
Registration Statement, the Company shall notify each Investor of the
information the Company requires from each such Investor if such Investor elects
to have any of such Investor's Registrable Securities included in such
Registration Statement for disposition by such Investor. It shall be a condition
precedent to the obligations of the Company to complete the registration
pursuant to this Agreement with respect to the Registrable Securities of a
particular Investor that such Investor shall furnish to the Company such
information regarding itself, the Registrable Securities held by it and the
intended method of disposition of the Registrable Securities held by it as shall
be reasonably required to effect the effectiveness of the registration of such
Registrable Securities and shall execute such documents in connection with such
registration as the Company may reasonably request. Each Investor shall promptly
notify the Company of any material change with respect to such information
previously provided to the Company by such Investor.

        (b)   Each Investor agrees to cooperate with the Company as reasonably
requested by the Company in connection with the preparation and filing of any
Registration Statement hereunder, unless such Investor has notified the Company
in writing of such Investor's election to exclude all of such Investor's
Registrable Securities from such Registration Statement, in which case, such
Investor does not need to cooperate with the Company until it notifies the
Company of its desire to include one or more share of the Registrable Securities
in such Registration Statement.

        (c)   Each Investor agrees that, upon receipt of any notice from the
Company of the happening of any event of the kind described in Sections 3(f) or
3(m) of this Agreement or the first sentence of Section 3(e) of this Agreement,
such Investor will immediately discontinue disposition of Registrable Securities
pursuant to any Registration Statements covering such Registrable Securities
until such Investor's receipt of the copies of the amended or supplemented
prospectus contemplated by Section 3(f) of this Agreement or the first sentence
of Section 3(e)of this Agreement or receipt of notice that no amendment or
supplement is required and, if so directed by the Company, such Investor

7

--------------------------------------------------------------------------------

shall deliver to the Company (at the expense of the Company) or destroy (and
deliver to the Company a certificate of destruction) all copies of the
prospectus covering such Registrable Securities current at the time of receipt
of such notice in such Investor's possession. Notwithstanding anything to the
contrary in this Agreement, the Company shall cause its transfer agent to
deliver unlegended shares of Common Stock to a transferee of an Investor in
accordance with the terms of the Securities Purchase Agreement in connection
with any sale of Registrable Securities with respect to which an Investor has
entered into a contract for sale prior to the Investor's receipt of a notice
from the Company of the happening of any event of the kind described in
Section 3(f) of this Agreement or the first sentence of Section 3(e) of this
Agreement and for which the Investor has not yet settled.

        5.    Expenses of Registration.    All expenses incurred by the Company
in connection with registrations, filings or qualifications pursuant to Sections
2 and 3 of this Agreement, including, without limitation, all registration,
listing and qualifications fees, printers and accounting fees, and fees and
disbursements of counsel for the Company, shall be paid by the Company.

        6.    Indemnification.    In the event any Registrable Securities are
included in a Registration Statement under this Agreement:

        (a)   To the fullest extent permitted by law, the Company will, and
hereby does, indemnify, hold harmless and defend each Investor, the directors,
officers, members, partners, employees, agents, representatives of, and each
Person, if any, who controls any Investor within the meaning of the Securities
Act or the Exchange Act (each, an "Indemnified Person"), against any losses,
claims, damages, liabilities, judgments, fines, penalties, charges, costs,
reasonable attorneys' fees, amounts paid in settlement or expenses, joint or
several (collectively, "Claims"), incurred in investigating, preparing or
defending any action, claim, suit, inquiry, proceeding, investigation or appeal
taken from the foregoing by or before any court or governmental, administrative
or other regulatory agency, body or the Commission, whether pending or
threatened, whether or not an indemnified party is or may be a party thereto
("Indemnified Damages"), to which any of them may become subject insofar as such
Claims (or actions or proceedings, whether commenced or threatened, in respect
thereof) arise out of or are based upon (i) any untrue statement or alleged
untrue statement of a material fact in a Registration Statement or any amendment
(including post-effective amendments) or supplement thereto or in any filing
made in connection with the qualification of the offering under the securities
or other "blue sky" laws of any jurisdiction in which Registrable Securities are
offered ("Blue Sky Filing"), or the omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading, (ii) any untrue statement or alleged untrue statement of
a material fact contained in any preliminary prospectus if used prior to the
effective date of such Registration Statement, or contained in the final
prospectus (as amended or supplemented, if any), or the omission or alleged
omission to state therein any material fact necessary to make the statements
made therein, in light of the circumstances under which the statements therein
were made, not misleading, or (iii) any violation or alleged violation caused by
the Company, or its directors, officers, employees, agents or representatives
acting on its behalf, of the Securities Act, the Exchange Act, any other law,
including, without limitation, any state securities law, or any rule or
regulation thereunder relating to the offer or sale of the Registrable
Securities pursuant to a Registration Statement (the matters in the foregoing
clauses (i) through (iii) being, collectively, "Violations"). Subject to
Section 6(c) of this Agreement, the Company shall reimburse the Indemnified
Persons, promptly as such expenses are incurred and are due and payable, for any
legal fees or other reasonable expenses incurred by them in connection with
investigating or defending any such Claim. Notwithstanding anything to the
contrary contained herein, the indemnification agreement contained in this
Section 6(a): (i) shall not apply to a Claim by an Indemnified Person arising
out of or based upon a Violation which occurs in reliance upon and in conformity
with information furnished in writing to the Company by such Indemnified Person
for such Indemnified Person expressly for use in connection with the preparation
of the Registration Statement or any such amendment thereof or supplement
thereto;

8

--------------------------------------------------------------------------------

(ii) shall not be available to the extent such Claim is based on a failure of
the Investor to deliver or to cause to be delivered the prospectus made
available by the Company, including a corrected prospectus, if such prospectus
or corrected prospectus was timely made available by the Company pursuant to
Section 3(c) of this Agreement and such correct prospectus would have corrected
the Claim to which such Violation pertains; and (iii) shall not apply to amounts
paid in settlement of any Claim if such settlement is effected without the prior
written consent of the Company, which consent shall not be unreasonably withheld
or delayed. Such indemnity shall remain in full force and effect regardless of
any investigation made by or on behalf of the Indemnified Person and shall
survive the transfer of the Registrable Securities by the Investors pursuant to
Section 9 of this Agreement.

        (b)   In connection with any Registration Statement in which an Investor
is participating, each such Investor agrees to severally and not jointly
indemnify, hold harmless and defend, to the same extent and in the same manner
as is set forth in Section 6(a) of this Agreement, the Company, each of its
directors, each of its officers who signs the Registration Statement and each
Person, if any, who controls the Company within the meaning of the Securities
Act or the Exchange Act (each, an "Indemnified Party"), against any Claims or
Indemnified Damages to which any of them may become subject, under the
Securities Act, the Exchange Act or otherwise, insofar as such Claims or
Indemnified Damages arise out of or are based upon any Violation, in each case
to the extent, and only to the extent, that such Violation occurs in reliance
upon and in conformity with written information furnished to the Company by such
Investor expressly for use in connection with such Registration Statement and,
subject to Section 6(c) of this Agreement, such Investor will reimburse any
legal or other expenses reasonably incurred by an Indemnified Party in
connection with investigating or defending any such Claim; provided, however,
that the indemnity agreement contained in this Section 6(b) and the agreement
with respect to contribution contained in Section 7 of this Agreement shall not
apply to amounts paid in settlement of any Claim if such settlement is effected
without the prior written consent of such Investor, which consent shall not be
unreasonably withheld or delayed; provided, further, that the Investor shall be
liable under this Section 6(b) for only that amount of the Claims and
Indemnified Damages as does not exceed the net proceeds to such Investor as a
result of the sale of Registrable Securities giving rise to such Violation
pursuant to such Registration Statement. Such indemnification agreement shall
remain in full force and effect regardless of any investigation made by or on
behalf of such Indemnified Party and shall survive the transfer of the
Registrable Securities by the Investors pursuant to Section 9 of this Agreement.
Notwithstanding anything to the contrary contained herein, the indemnification
agreement contained in this Section 6(b) shall not inure to the benefit of any
Indemnified Party if the untrue statement or omission of material fact contained
in the preliminary prospectus was corrected on a timely basis in the prospectus,
as then amended or supplemented.

        (c)   Promptly after an Indemnified Person or Indemnified Party under
this Section 6 has knowledge of any Claim as to which such Indemnified Person
reasonably believes indemnity may be sought or promptly after such Indemnified
Person or Indemnified Party receives notice of the commencement of any action or
proceeding (including any governmental action or proceeding) involving a Claim,
such Indemnified Person or Indemnified Party shall, if a Claim in respect
thereof is to be made against any indemnifying party under this Section 6,
deliver to the indemnifying party a written notice of such Claim, and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume control of the defense thereof with counsel
mutually satisfactory to the indemnifying party and the Indemnified Person or
the Indemnified Party, as the case may be; provided, however, that an
Indemnified Person or Indemnified Party shall have the right to retain its own
counsel if, in the reasonable opinion of counsel retained by the indemnifying
party, the representation by such counsel of the Indemnified Person or
Indemnified Party and the indemnifying party would be inappropriate due to
actual or potential differing interests between such Indemnified Person or
Indemnified Party and any other party represented by such counsel in such
proceeding; provided, further, that the indemnifying party shall not be
responsible for the reasonable fees and expense of more than one (1) separate
legal

9

--------------------------------------------------------------------------------

counsel for such Indemnified Person or Indemnified Party. In the case of an
Indemnified Person, the legal counsel referred to in the immediately preceding
sentence shall be selected by the Investors holding at least a majority of the
Registrable Securities included in the Registration Statement to which the Claim
relates. The Indemnified Party or Indemnified Person shall cooperate fully with
the indemnifying party in connection with any negotiation or defense of any such
action or Claim by the indemnifying party and shall furnish to the indemnifying
party all information reasonably available to the Indemnified Party or
Indemnified Person which relates to such action or Claim. The indemnifying party
shall keep the Indemnified Party or Indemnified Person fully apprised at all
times as to the status of the defense or any settlement negotiations with
respect thereto. No indemnifying party shall be liable for any settlement of any
action, claim or proceeding effected without its prior written consent;
provided, however, that the indemnifying party shall not unreasonably withhold,
delay or condition its consent. No indemnifying party shall, without the prior
written consent of the Indemnified Party or Indemnified Person, consent to entry
of any judgment or enter into any settlement or other compromise which does not
include as an unconditional term thereof the giving by the claimant or plaintiff
to such Indemnified Party or Indemnified Person of a full release from all
liability in respect to such Claim and action and proceeding. After
indemnification as provided for under this Agreement, the rights of the
indemnifying party shall be subrogated to all rights of the Indemnified Party or
Indemnified Person with respect to all third parties, firms or corporations
relating to the matter for which indemnification has been made. The failure to
deliver written notice to the indemnifying party as provided in this Agreement
shall not relieve such indemnifying party of any liability to the Indemnified
Person or Indemnified Party under this Section 6, except to the extent that the
indemnifying party is prejudiced in its ability to defend such action.

        (d)   The indemnification required by this Section 6 shall be made by
periodic payments of the amount thereof during the course of the investigation
or defense, as and when bills are received or Indemnified Damages are incurred.

        (e)   The indemnity agreements contained herein shall be in addition to
(i) any cause of action or similar right of the Indemnified Party or Indemnified
Person against the indemnifying party or others, and (ii) any liabilities the
indemnifying party may be subject to pursuant to the law.

        7.    Contribution.    To the extent any indemnification by an
indemnifying party is prohibited or limited by law, then, in order to provide
for just and equitable contribution, the indemnifying party agrees to make the
maximum contribution with respect to any amounts for which it would otherwise be
liable under Section 6 of this Agreement to the fullest extent permitted by law;
provided, however, that (i) no contribution shall be made under circumstances
where the maker would not have been liable for indemnification under the fault
standards set forth in Section 6 of this Agreement, (ii) no Person involved in
the sale of Registrable Securities which Person is guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act) in
connection with such sale shall be entitled to contribution from any Person
involved in such sale of Registrable Securities who was not guilty of fraudulent
misrepresentation, and (iii) contribution by any seller of Registrable
Securities shall be limited in amount to the net amount of proceeds received by
such seller from the sale of such Registrable Securities pursuant to such
Registration Statement. Any party entitled to contribution will, promptly after
receipt of notice of commencement of any action, suit or proceeding against such
party in respect of which a claim for contribution may be made against another
party or parties under this Section 7, notify such party or parties from whom
contribution may be sought, but the omission so to notify such party or parties
from whom contribution may be sought shall not relieve such party from any other
obligation it or they may have thereunder or otherwise under this Section 7. No
party shall be liable for contribution with respect to any action, suit,
proceeding or claim settled without its prior written consent, which consent
shall not be unreasonably withheld, conditioned or delayed. The provisions of
this Section 7 shall remain in full force and effect, regardless of the
investigation made by

10

--------------------------------------------------------------------------------

or on behalf of the beneficiaries of this Section 7 and shall survive the
transfer of Registrable Securities by the Investors pursuant to Section 9 of
this Agreement.

        8.    Reporting.    

        (a)    Reports under the Exchange Act.    With a view to making
available to the Investors the benefits of Rule 144 promulgated under the
Securities Act or any other similar rule or regulation of the Commission that
may at any time permit the Investors to sell securities of the Company to the
public without registration ("Rule 144"), the Company shall use its reasonable
efforts to:

        (1)   make and keep public information available, as those terms are
understood and defined in Rule 144;

        (2)   file with the Commission in a timely manner all reports and other
documents required of the Company under the Securities Act and the Exchange Act;
and

        (3)   furnish to each Investor, so long as such Investor owns
Registrable Securities, promptly upon request, (A) a written statement by the
Company, if true, that it has complied with the applicable reporting
requirements of Rule 144, the Securities Act and the Exchange Act, (B) a copy of
the most recent annual or quarterly report of the Company and copies of such
other reports and documents so filed by the Company, and (C) such other
information as may be reasonably requested to permit the Investors to sell such
securities pursuant to Rule 144 without registration.

        (b)    Rule 144A Information.    The Company shall, upon request of any
Investor, make available to such Investor the information required by
Rule 144A(d)(4) (or any successor rule) under the Securities Act.

        9.    Assignment of Registration Rights.    The rights under this
Agreement shall be automatically assignable by the Investors to any transferee
of at least 100,000 Registrable Securities (subject to proportionate adjustment
for any stock split, reverse stock split, recapitalizations, or similar event)
if, (A) within three (3) Business Days of such transfer (i) the Investor agrees
in writing with the transferee or assignee to assign such rights, and a copy of
such agreement is furnished to the Company; (ii) the Company is furnished with
written notice of (a) the name and address of such transferee or assignee, and
(b) the securities with respect to which such rights are being transferred or
assigned; (B) at or before the time the Company receives the written notice
contemplated by clause A(ii) of this sentence, the transferee or assignee agrees
in writing with the Company to be bound by all of the obligations of an Investor
under this Agreement immediately following such transfer or assignment, the
further disposition of such securities by the transferee or assignee is
restricted under the Securities Act and applicable state securities laws;
(C) such transfer shall have been made in accordance with the applicable
requirements of the Securities Purchase Agreement; and (D) such transfer shall
have been conducted in accordance with all applicable federal and state
securities laws.

        10.    Amendment of Registration Rights.    Any provision of this
Agreement may be amended and the observance of any provision of this Agreement
may be waived (either generally or in a particular instance and either
retroactively or prospectively), only with the written consent of the Company
and Investors who then hold at least a majority of the Registrable Securities.
Any amendment or waiver effected in accordance with this Section 10 shall be
binding upon each Investor and the Company. No such amendment shall be effective
to the extent that it applies to less than all of the holders of the Registrable
Securities. No consideration shall be offered or paid to any Person to amend or
consent to a waiver or modification of any provision of any of this Agreement
unless the same consideration also is offered to all of the parties to this
Agreement.

11

--------------------------------------------------------------------------------

        11.    Miscellaneous.    

        (a)   If at any time during the Registration Period there is not an
effective Registration Statement covering all of the Registrable Securities and
the Company shall determine to prepare and file with the Commission a
registration statement relating to an offering for its own account or the
account of others under the Securities Act of any of its equity securities,
other than on Form S-4 or Form S-8 (each as promulgated under the Securities
Act) or their then equivalents relating to equity securities to be issued solely
in connection with any acquisition of any entity or business or equity
securities issuable in connection with stock option or other employee benefit
plans, then the Company shall send to each Investor written notice of such
determination and, if within fifteen days after receipt of such notice, any such
Investor shall so request in writing, the Company shall include in such
registration statement all or any part of such Registrable Securities such
holder requests to be registered, subject to customary underwriter cutbacks
applicable to all holders of registration rights.

        (b)   A Person is deemed to be a holder of Registrable Securities
whenever such Person owns or is deemed to own of record such Registrable
Securities. If the Company receives conflicting instructions, notices or
elections from two or more Persons with respect to the same Registrable
Securities, the Company shall act upon the basis of instructions, notice or
election received from such record owner of such Registrable Securities.

        (c)   Any notices, consents, waivers or other communications required or
permitted to be given under the terms of this Agreement must be in writing and
will be deemed to have been delivered: (i) upon receipt, when delivered
personally; (ii) upon receipt, when sent by facsimile (provided confirmation of
transmission is mechanically or electronically generated and kept on file by the
sending party); or (iii) one (1) Business Day after deposit with a nationally
recognized overnight delivery service, in each case properly addressed to the
party to receive the same. The addresses and facsimile numbers for such
communications shall be:

        If to the Company:

GTC Biotherapeutics, Inc.
175 Crossing Boulevard
Framingham, MA 01702
Telephone: (508) 270-2061
Facsimile: (508) 271-3491
Attention: Geoffrey F. Cox, Ph.D.
                  Chairman, President and Chief Executive Officer

        with a copy to:

Palmer & Dodge LLP
111 Huntington Avenue
Boston, MA 02199
Telephone: (617) 239-0100
Facsimile: (617) 227-4420
Attention: Nathaniel Gardiner, Esq.

        If to a Purchaser, to its address and facsimile number set forth on the
Schedule of Purchasers attached to the Securities Purchase Agreement as
Exhibit A, with copies to such Purchaser's representatives as set forth on the
Schedule of Purchasers, or to such other address and/or facsimile number and/or
to the attention of such other Person as the recipient party has specified by
written notice given to each other party five (5) days prior to the
effectiveness of such change. Written confirmation of receipt (A) given by the
recipient of such notice, consent, waiver or other communication,
(B) mechanically or electronically generated by the sender's facsimile machine
containing the time, date, recipient facsimile number and an image of the first
page of such

12

--------------------------------------------------------------------------------

transmission, or (C) provided by a courier or overnight courier service shall be
rebuttable evidence of personal service, receipt by facsimile or receipt from a
nationally recognized overnight delivery service in accordance with clause (i),
(ii) or (iii) above, respectively.

        (d)   Failure of any party to exercise any right or remedy under this
Agreement or otherwise, or delay by a party in exercising such right or remedy,
shall not operate as a waiver thereof.

        (e)   All questions concerning the construction, validity, enforcement
and interpretation of this Agreement shall be governed by the internal laws of
the State of New York, without giving effect to any choice of law or conflict of
law provision or rule (whether of the State of New York or any other
jurisdictions) that would cause the application of the laws of any jurisdictions
other than the State of New York. Each party hereby irrevocably submits to the
non-exclusive jurisdiction of the state and federal courts sitting in the City
of New York, Borough of Manhattan, for the adjudication of any dispute hereunder
or in connection herewith or with any transaction contemplated hereby or
discussed herein, and hereby irrevocably waives, and agrees not to assert in any
suit, action or proceeding, any claim that it is not personally subject to the
jurisdiction of any such court, that such suit, action or proceeding is brought
in an inconvenient forum or that the venue of such suit, action or proceeding is
improper. Each party hereby irrevocably waives personal service of process and
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address for such notices to it under
this Agreement and agrees that such service shall constitute good and sufficient
service of process and notice thereof. Nothing contained herein shall be deemed
to limit in any way any right to serve process in any manner permitted by law.
If any provision of this Agreement shall be invalid or unenforceable in any
jurisdiction, such invalidity or unenforceability shall not affect the validity
or enforceability of the remainder of this Agreement in that jurisdiction or the
validity or enforceability of any provision of this Agreement in any other
jurisdiction. EACH PARTY HEREBY IRREVOCABLY WAIVES ANY RIGHT IT MAY HAVE, AND
AGREES NOT TO REQUEST, A JURY TRIAL FOR THE ADJUDICATION OF ANY DISPUTE
HEREUNDER OR IN CONNECTION HEREWITH OR ARISING OUT OF THIS AGREEMENT OR ANY
TRANSACTION CONTEMPLATED HEREBY.

        (f)    This Agreement, the Securities Purchase Agreement and the
documents referenced herein and therein constitute the entire agreement among
the parties hereto with respect to the subject matter hereof and thereof. There
are no restrictions, promises, warranties or undertakings, other than those set
forth or referred to herein and therein. This Agreement, the Securities Purchase
Agreement and the documents referenced herein and therein supersede all prior
agreements and understandings among the parties hereto with respect to the
subject matter hereof and thereof.

        (g)   Subject to the requirements of Section 9 `of this Agreement, this
Agreement shall inure to the benefit of and be binding upon the permitted
successors and assigns of each of the parties hereto.

        (h)   The headings in this Agreement are for convenience of reference
only and shall not limit or otherwise affect the meaning hereof.

        (i)    This Agreement may be executed in identical counterparts, each of
which shall be deemed an original but all of which shall constitute one and the
same agreement. This Agreement, once executed by a party, may be delivered to
the other parties hereto by facsimile transmission of a copy of this Agreement
bearing the signature of the party so delivering this Agreement.

        (j)    Each party shall do and perform, or cause to be done and
performed, all such further acts and things, and shall execute and deliver all
such other agreements, certificates, instruments and documents, as the other
party may reasonably request in order to carry out the intent and accomplish the
purposes of this Agreement and the consummation of the transactions contemplated
hereby.

13

--------------------------------------------------------------------------------

        (k)   All consents and other determinations required to be made by the
Investors pursuant to this Agreement shall be made, unless otherwise specified
in this Agreement, by Investors holding at least a majority of the Registrable
Securities.

        (l)    The language used in this Agreement will be deemed to be the
language chosen by the parties to express their mutual intent and no rules of
strict construction will be applied against any party.

        (m)  This Agreement is intended for the benefit of the parties hereto
and their respective permitted successors and assigns, and is not for the
benefit of, nor may any provision hereof be enforced by, any other Person.

        (n)   The obligations of each Investor hereunder is several and not
joint with the obligations of any other Investor hereunder, and no Investor
shall be responsible in any way for the performance of the obligations of any
other Investor hereunder. Nothing contained herein or in any other agreement or
document delivered at any closing, and no action taken by any Investor pursuant
hereto or thereto, shall be deemed to constitute the Investors as a partnership,
an association, a joint venture or any other kind of entity, or create a
presumption that the Investors are in any way acting in concert with respect to
such obligations or the transactions contemplated by this Agreement. Each
Investor shall be entitled to protect and enforce its rights, including without
limitation the rights arising out of this Agreement, and it shall not be
necessary for any other Investor to be joined as an additional party in any
proceeding for such purpose.

[Remainder of page intentionally left blank.]

14

--------------------------------------------------------------------------------

        IN WITNESS WHEREOF, the parties have caused this Securities Purchase
Agreement to be duly executed as of the date first written above.

    COMPANY:
 
 
GTC Biotherapeutics, Inc.
 
 
By:
/s/  JOHN B. GREEN      

--------------------------------------------------------------------------------

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

[Signatures of Purchasers on Following Page]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
BAYSTAR CAPITAL II, LP, a Delaware limited partnership
 
 
By:
BayStar Capital Management, LLC, its general partner
 
 
By:
/s/  STEVEN M. LAMAR      

--------------------------------------------------------------------------------

    Name: Steven M. Lamar     Title: Managing Member
 
 
c/o BayStar Capital Management, LLC
80 E. Sir Francis Drake Blvd., Suite 2B
Larkspur, California 94939
Tel: (415) 834-4600
Fax: (415) 834-4601
Attn: Steven Lamar

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
CASTLE CREEK HEALTHCARE
PARTNERS LLC
 
 
By:
/s/  THOMAS A. FREI      

--------------------------------------------------------------------------------

Name: Thomas A. Frei
Title: Managing Director of the Investment Manager

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
CLARION CAPITAL CORPORATION
 
 
By:
/s/  MORTON COHEN      

--------------------------------------------------------------------------------

Name: Morton Cohen
Title: Chairman

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
DEEPHAVEN SMALL CAP GROWTH FUND LLC
 
 
By:
/s/  BRUCE LIEBERMAN      

--------------------------------------------------------------------------------

Name: Bruce Lieberman
Title: Director of Private Placements

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
GRYPHON MASTER FUND, LP
 
 
By:
/s/  E.B. LYON IV      

--------------------------------------------------------------------------------

Name: E.B. Lyon IV
Title: Authorized Agent

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
CAPITAL VENTURES INTERNATIONAL
 
 
By:
Heights Capital Management, Inc., its authorized agent
 
 
By:
/s/  MARTIN KOBINGER      

--------------------------------------------------------------------------------

Name: Martin Kobinger
Title: Investment Manager

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
SMITHFIELD FIDUCIARY LLC
 
 
By:
/s/  ADAM J. CHILL      

--------------------------------------------------------------------------------

Name: Adam J. Chill
Title: Authorized Signatory

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
MIDSUMMER INVESTMENT, LTD.
 
 
By:
/s/  MICHAEL A. AMSALEM      

--------------------------------------------------------------------------------

    Name: Michael A. Amsalem     Title: Director

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
ALL AMERICA – SMALL CAP GROWTH FUND
 
 
By:
/s/  THOMAS P. LARSEN      

--------------------------------------------------------------------------------

    Name: Thomas P. Larsen     Title: EVP Mutual of America Capital Mgt.

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
INSTITUTIONAL AGGRESSIVE EQUITY GROWTH FUND
 
 
By:
/s/  THOMAS P. LARSEN      

--------------------------------------------------------------------------------

    Name: Thomas P. Larsen     Title: EVP Mutual of America Capital Mgt.

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
AGGRESSIVE EQUITY GROWTH FUND
 
 
By:
/s/  THOMAS P. LARSEN      

--------------------------------------------------------------------------------

    Name: Thomas P. Larsen     Title: EVP Mutual of America Capital Mgt.

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
INSTITUTIONAL ALL AMERICAN SMALL CAP GROWTH FUND
 
 
By:
/s/  THOMAS P. LARSEN      

--------------------------------------------------------------------------------

    Name: Thomas P. Larsen     Title: EVP Mutual of America Capital Mgt.

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
OMICRON MASTER TRUST
 
 
By:
Omicron Capital L.P. as investment advisor     By: Omicron Capital Inc., its
general partner
 
 
By:
/s/  OLIVIER MORALI      

--------------------------------------------------------------------------------

    Name: Olivier Morali     Title: President
 
 
c/o Omicron Capital L.P.
810 Seventh Avenue, 39th Floor
New York, New York 10019
Attn: Brian Daly

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
PORTSIDE GROWTH AND OPPORTUNITY FUND
 
 
By:
/s/  JEFF SMITH      

--------------------------------------------------------------------------------

    Name: Jeff Smith     Title: Director

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
ROYAL BANK OF CANADA     By: Its Agent RBC Dominion Securities Corporation
 
 
By:
/s/  STEVEN MILKE      

--------------------------------------------------------------------------------

    Name: Steven Milke     Title: Managing Director
 
 
By:
/s/  RICHARD TAVOSO      

--------------------------------------------------------------------------------

    Name: Richard Tavoso     Title: Managing Director

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

    PURCHASER:
 
 
PANACEA FUND LLC
 
 
By:
/s/  MICHAEL S. RESNICK      

--------------------------------------------------------------------------------

    Name: Michael S. Resnick     Title: Executive Vice President, William Harris
Investors, Inc., as Manager

[Signature Page of Registration Rights Agreement of GTC Biotherapeutics, Inc.]

--------------------------------------------------------------------------------

Annex A

Plan of Distribution

        The Selling Stockholders and any of their pledgees, donees, assignees
and successors-in-interest may, from time to time, sell any or all of their
shares of Common Stock on any stock exchange, market or trading facility on
which the shares are traded or in private transactions. These sales may be at
fixed or negotiated prices. The Selling Stockholders may use any one or more of
the following methods when selling shares:

•ordinary brokerage transactions and transactions in which the broker-dealer
solicits purchasers;

•block trades in which the broker-dealer will attempt to sell the shares as
agent but may position and resell a portion of the block as principal to
facilitate the transaction;

•purchases by a broker-dealer as principal and resale by the broker-dealer for
its account;

•an exchange distribution in accordance with the rules of the applicable
exchange;

•privately negotiated transactions;

•short sales

•broker-dealers may agree with the Selling Stockholders to sell a specified
number of such shares at a stipulated price per share;

•a combination of any such methods of sale; and

•any other method permitted pursuant to applicable law.

        The Selling Stockholders may also sell shares under Rule 144 under the
Securities Act, if available, rather than under this prospectus.

        Broker-dealers engaged by the Selling Stockholders may arrange for other
brokers-dealers to participate in sales. Broker-dealers may receive commissions
or discounts from the Selling Stockholders (or, if any broker-dealer acts as
agent for the purchaser of shares, from the purchaser) in amounts to be
negotiated. The Selling Stockholders do not expect these commissions and
discounts to exceed what is customary in the types of transactions involved.

        The Selling Stockholders may from time to time pledge or grant a
security interest in some or all of the Shares or Warrant Shares owned by them
and, if they default in the performance of their secured obligations, the
pledgees or secured parties may offer and sell shares of Common Stock from time
to time under this prospectus, or under an amendment to this prospectus under
Rule 424(b)(3) or other applicable provision of the Securities Act of 1933
amending the list of selling stockholders to include the pledgee, transferee or
other successors in interest as selling stockholders under this prospectus.

        The Selling Stockholders also may transfer the shares of common stock in
other circumstances, in which case the transferees, pledgees or other successors
in interest will be the selling beneficial owners for purposes of this
prospectus.

        The Selling Stockholders and any broker-dealers or agents that are
involved in selling the shares may be deemed to be "underwriters" within the
meaning of the Securities Act in connection with such sales. In such event, any
commissions received by such broker-dealers or agents and any profit on the
resale of the shares purchased by them may be deemed to be underwriting
commissions or discounts under the Securities Act. Each Selling Stockholder has
informed the Company that: (i) it does not have any agreement or understanding,
directly or indirectly, with any person to distribute the Common Stock and
(ii) it is not a registered broker dealer under the Securities Exchange Act of
1934.

        The Company is required to pay all fees and expenses incident to the
registration of the shares. The Company has agreed to indemnify the Selling
Stockholders against certain losses, claims, damages and liabilities, including
liabilities under the Securities Act.

--------------------------------------------------------------------------------

Exhibit A

 
  Number of Shares

--------------------------------------------------------------------------------

  Number of Warrant Shares

--------------------------------------------------------------------------------

BayStar Capital II, LP   196,078   49,019 Castle Creek Healthcare Partners LLC  
294,117   73,529 Clarion Capital Corporation   100,000   25,000 Deephaven Small
Cap Growth Fund LLC   392,157   98,039 Gryphon Master Fund, LP   196,078  
49,019 Capital Ventures International   588,235   147,058 Smithfield Fiduciary
LLC   196,078   49,019 Midsummer Investment, Ltd.   200,000   50,000 All America
— Small Cap Growth Fund   95,372   23,843 Institutional Aggressive Equity Growth
Fund   10,863   2,715 Aggressive Equity Growth Fund   276,941   69,235
Institutional All America Small Cap Growth Fund   8,980   2,245 Omicron Master
Trust   137,254   34,313 Portside Growth and Opportunity Fund   392,156   98,039
Royal Bank of Canada   392,156   37,500 Panacea Fund LLC   150,000   37,500

--------------------------------------------------------------------------------

QuickLinks

Exhibit 10.3 Execution Copy

GTC BIOTHERAPEUTICS, INC. REGISTRATION RIGHTS AGREEMENT dated as of July 30,
2003
GTC BIOTHERAPEUTICS, INC. REGISTRATION RIGHTS AGREEMENT
RECITALS

Annex A

Exhibit A