SUBSCRIPTION AGREEMENT

Exhibit 10.2

SUBSCRIPTION AGREEMENT

GTC Biotherapeutics, Inc.

175 Crossing Boulevard

Framingham, MA 01702

The undersigned (the “Investor”) hereby confirms its agreement with you as follows:

1. This Subscription Agreement (this “Agreement”) is made as of the date set forth below between GTC Biotherapeutics, Inc., a Massachusetts corporation (the “Company”), and the Investor.

2. The Company has authorized the sale and issuance to certain investors of up to an aggregate of 9,101,912 units (the “Units”), each consisting of (i) one share (the “Shares”) of its Common Stock, par value $0.01 per share (the “Common Stock”) and (ii) one warrant (the “Warrants”) to purchase 0.4 Shares of Common Stock (and the fractional amount being the “Warrant Ratio”), in substantially the form attached hereto as Exhibit A, subject to adjustment by the Company’s Board of Directors, or a committee thereof, for a purchase price of $1.83 per Unit (the “Purchase Price”). The shares issuable upon the exercise of the Warrants are referred to herein as the “Warrant Shares” and, together with the Units, the Shares and the Warrants, are referred to herein as the “Securities”.

3. The offering and sale of the Securities (the “Offering”) are being made pursuant to an effective Registration Statement on Form S-3 (including the Prospectus contained therein (the “Base Prospectus”) and the exhibits thereto and the documents incorporated therein by reference, the “Registration Statement”) filed by the Company with the Securities and Exchange Commission (the “Commission”), if applicable, certain preliminary prospectuses and/or “free writing prospectuses” (as that term is defined in Rule 405 under the Securities Act of 1933, as amended), that have or will be filed with the Commission and delivered to the Investor on or prior to the date hereof (the “Time of Sale Prospectus”), and a Prospectus Supplement (the “Prospectus Supplement”) containing certain supplemental information regarding the Shares and terms of the Offering that will be filed with the Commission and delivered, or otherwise made available, to the Investor along with the Company’s counterpart to this Agreement.

4. The Company and the Investor agree that the Investor will purchase from the Company and the Company will issue and sell to the Investor the Units as set forth below for the aggregate purchase price set forth below. The Units shall be purchased pursuant to the Terms and Conditions for Purchase of Units attached hereto as Annex I and incorporated herein by this reference as if fully set forth herein.

5. The manner of settlement of the Shares included in the Units and purchased by the Investor shall be determined by such Investor as follows (check one):

THE CITIBANK PRIVATE BANK

153 East 53^rd Street

New York, NY 10043

ABA # 021-000-089

Account Name: GTC Biotherapeutics, Inc.

Account Number: 49486662

– OR –

IT IS THE INVESTOR’S RESPONSIBILITY TO (A) MAKE THE NECESSARY WIRE TRANSFER OR CONFIRM THE PROPER ACCOUNT BALANCE IN A TIMELY MANNER AND (B) ARRANGE FOR SETTLEMENT BY WAY OF DWAC OR DVP IN A TIMELY MANNER. IF THE INVESTOR DOES NOT DELIVER THE AGGREGATE PURCHASE PRICE FOR THE UNITS OR DOES NOT MAKE PROPER ARRANGEMENTS FOR SETTLEMENT IN A TIMELY MANNER, THE SHARES AND WARRANTS MAY NOT BE DELIVERED AT CLOSING TO THE INVESTOR OR THE INVESTOR MAY BE EXCLUDED FROM THE CLOSING ALTOGETHER.

6. The executed Warrant shall be delivered in accordance with the terms thereof.

- 2 -

7. The Investor represents that, except as set forth below, (a) it has had no position, office or other material relationship within the past three years with the Company or any of its affiliates and (b) it has no direct or indirect affiliation or association with any NASD member. Exceptions:

(If no exceptions, write “none.” If left blank, response will be deemed to be “none.”)

Purchase Price Per Unit:      $                                

Aggregate Purchase Price: $                                

Please confirm that the foregoing correctly sets forth the agreement between us by signing in the space provided below for that purpose.

Agreed and Accepted

this          day of December 2005

- 3 -

ANNEX I

TERMS AND CONDITIONS FOR PURCHASE OF UNITS

1. Authorization and Sale of the Units. Subject to the terms and conditions of this Agreement, the Company has authorized the sale of the Units, which consist of the Shares and the Warrants.

2. Agreement to Sell and Purchase the Units; Placement Agents.

2.1 At the Closing (as defined in Section 3.1), the Company will sell to the Investor, and the Investor will purchase from the Company, upon the terms and conditions set forth herein, the number of Units set forth on the last page of the Agreement to which these Terms and Conditions for Purchase of Units are attached as Annex I (the “Signature Page”) for the aggregate purchase price therefor set forth on the Signature Page.

2.2 The Company proposes to enter into substantially this same form of Subscription Agreement with certain other investors (the “Other Investors”) and expects to complete sales of Units to them. The Investor and the Other Investors are hereinafter sometimes collectively referred to as the “Investors,” and this Agreement and the Subscription Agreements executed by the Other Investors are hereinafter sometimes collectively referred to as the “Agreements.”

2.3 Investor acknowledges that the Company intends to pay SG Cowen & Co., LLC and Rodman & Renshaw, LLC (together, the “Placement Agents”) a fee (the “Placement Fee”) in respect of the sale of Units to the Investor.

2.4 The Company has entered into a Placement Agent Agreement (the “Placement Agreement”) with the Placement Agents that contains certain representations and warranties of the Company to the Placement Agents. A copy of the Placement Agreement is available upon request.

3. Closings and Delivery of the Units and Funds.

3.1 Closing. The completion of the purchase and sale of the Units (the “Closing”) will occur at a place and time (the “Closing Date”) to be specified by the Company and the Placement Agents, and of which the Investors will be notified in advance by the Placement Agents. At the Closing, (a) the Company will cause the Transfer Agent to deliver to the Investor the number of Shares (and Units) set forth on the Signature Page registered in the name of the Investor or, if so indicated on the Investor Questionnaire attached hereto as Exhibit B, in the name of a nominee designated by the Investor, (b) the Company shall cause to be delivered to the Investor a Warrant to purchase the number of whole Warrant Shares determined by multiplying the number of Shares (and Units) set forth on the signature page by the Warrant Ratio and rounding down to the nearest whole number and (c) the aggregate purchase price for the Units being purchased by the Investor will be delivered by or on behalf of the Investor to the Company.

3.2 (a) Conditions to the Company’s Obligations. The Company’s obligation to issue the Shares and the Warrants to the Investor will be subject to the receipt by the Company of the purchase price for the Units being purchased hereunder as set forth on the Signature Page and the

- 4 -

accuracy of the representations and warranties made by the Investor and the fulfillment of those undertakings of the Investor to be fulfilled prior to the Closing Date.

(b) Conditions to the Investor’s Obligations. The Investor’s obligation to purchase the Units will be subject to the accuracy of the representations and warranties made by the Company and the fulfillment of those undertakings of the Company to be fulfilled prior to the Closing Date, including, without limitation, those contained in the Placement Agent Agreement (collectively, the “Company Closing Conditions”). The Investor’s obligations are expressly not conditioned on the purchase by any or all of the other Investors of the Units that they have agreed to purchase from the Company.

3.3 Delivery of Funds.

(a) Delivery by Electronic Book-Entry at The Depository Trust Company. If the Investor elects to settle the Shares purchased by such Investor through delivery by electronic book-entry at DTC, no later than one (1) business day after the execution of this Agreement by the Investor and the Company, the Investor shall remit by wire transfer the amount of funds equal to the aggregate purchase price for the shares being purchased by the Investor to the following account designated by the Company and the Placement Agents pursuant to the terms of that certain Escrow Agreement (the “Escrow Agreement”) dated as of December 7, 2005, by and among the Company, the Placement Agents and Brown Raysman Millstein Felder & Steiner LLP (the “Escrow Agent”):

THE CITIBANK PRIVATE BANK

153 East 53^rd Street

New York, NY 10043

ABA # 021-000-089

Account Name: GTC Biotherapeutics, Inc.

Account Number: 49486662

Such funds shall be held in escrow until the Closing and delivered by the Escrow Agent on behalf of the Investors to the Company upon the satisfaction, in the sole judgment of the Placement Agents, of the Company Closing Conditions. The Placement Agents shall have no rights in or to any of the escrowed funds, unless the Placement Agents and the Escrow Agent are notified in writing by the Company in connection with the Closing that a portion of the escrowed funds shall be applied to the Placement Fee. The Company and the Investor agree to indemnify and hold the Escrow Agent harmless from and against any and all losses, costs, damages, expenses and claims (including, without limitation, court costs and reasonable attorneys fees) (“Losses”) arising under this Section 3.3 or otherwise with respect to the funds held in escrow pursuant hereto or arising under the Escrow Agreement, unless it is finally determined that such Losses resulted directly from the willful misconduct or gross negligence of the Escrow Agent. Anything in this Agreement to the contrary notwithstanding, in no event shall the Escrow Agent be liable for any special, indirect or consequential loss or damage of any kind whatsoever (including but not limited to lost profits), even if the Escrow Agent has been advised of the likelihood of such loss or damage and regardless of the form of action.

Investor shall also furnish to the Placement Agents a completed W-9 form (or, in the case of an Investor who is not a United States citizen or resident, a W-8 form).

- 5 -

Investor acknowledges that the Escrow Agent acts as counsel to the Placement Agents, and shall have the right to continue to represent the Placement Agents, in any action, proceeding, claim, litigation, dispute, arbitration or negotiation in connection with the Offering, and Investor hereby consents thereto and waives any objection to the continued representation of the Placement Agents by the Escrow Agent in connection therewith based upon the services of the Escrow Agent under the Escrow Agreement, without waiving any duty or obligation the Escrow Agent may have to any other person.

(b) Delivery Versus Payment through The Depository Trust Company. If the Investor elects to settle the Shares purchased by such Investor by delivery versus payment through DTC, no later than one (1) business day after the execution of this Agreement by the Investor and the Company, the Investor shall confirm that the account or accounts at SG Cowen & Co., LLC to be credited with the Shares being purchased by the Investor have a minimum balance equal to the aggregate purchase price for the Units being purchased by the Investor.

3.4 Delivery of Shares.

(a) Delivery by Electronic Book-Entry at The Depository Trust Company. If the Investor elects to settle the Shares purchased by such Investor through delivery by electronic book-entry at DTC, no later than one (1) business day after the execution of this Agreement by the Investor and the Company, the Investor shall direct the broker-dealer at which the account or accounts to be credited with the Shares being purchased by such Investor are maintained, which broker/dealer shall be a DTC participant, to set up a Deposit/Withdrawal at Custodian (“DWAC”) instructing American Stock Transfer & Trust Company, the Company’s transfer agent, to credit such account or accounts with the Shares by means of an electronic book-entry delivery. Such DWAC shall indicate the settlement date for the deposit of the Shares, which date shall be provided to the Investor by the Placement Agents. Simultaneously with the delivery to the Company by the Escrow Agent of the funds held in escrow pursuant to Section 3.3 above, the Company shall direct its transfer agent to credit the Investor’s account or accounts with the Shares pursuant to the information contained in the DWAC.

(b) Delivery Versus Payment through The Depository Trust Company. If the Investor elects to settle the Shares purchased by such Investor by delivery versus payment through DTC, no later than one (1) business day after the execution of this Agreement by the Investor and the Company, the Investor shall notify SG Cowen & Co., LLC of the account or accounts at SG Cowen & Co., LLC to be credited with the Shares being purchased by such Investor. On the Closing Date, the Company shall deliver the Shares to the Investor directly to the account(s) at SG Cowen & Co., LLC identified by Investor and simultaneously therewith payment shall be made from such account(s) to the Company through DTC.

- 6 -

4. Representations, Warranties and Covenants of the Investor.

4.1 The Investor represents and warrants to, and covenants with, the Company that (a) the Investor is knowledgeable, sophisticated and experienced in making, and is qualified to make decisions with respect to, investments in shares presenting an investment decision like that involved in the purchase of the Units, including investments in securities issued by the Company and investments in comparable companies, and has requested, received, reviewed and considered all information it deemed relevant in making an informed decision to purchase the Units, (b) the Investor has answered all questions on the Signature Page for use in preparation of the Prospectus Supplement and the answers thereto are true and correct as of the date hereof and will be true and correct as of the Closing Date, (c) the Investor, in connection with its decision to purchase the number of Units set forth on the Signature Page, relied only upon the Base Prospectus, the Time of Sale Prospectus, if any, the Company’s regular reports on Forms 10-K, 10-Q and 8-K as filed by the Company with the Commission, and the representations and warranties of the Company contained herein and (d) the Investor is an “accredited investor” within the meaning of Rule 501(a)(1), (2) or (3) under the Securities Act of 1933, as amended (the “Securities Act”).

4.2 The Investor acknowledges, represents and agrees that no action has been or will be taken in any jurisdiction outside the United States by the Company or any Placement Agent that would permit an offering of the Units, or possession or distribution of offering materials in connection with the issue of the Units in any jurisdiction outside the United States where action for that purpose is required. Each Investor outside the United States will comply with all applicable laws and regulations in each foreign jurisdiction in which it purchases, offers, sells or delivers Units or has in its possession or distributes any offering material, in all cases at its own expense. The Placement Agents are not authorized to make and have not made any representation or use of any information in connection with the issue, placement, purchase and sale of the Units, except as set forth or incorporated by reference in the Base Prospectus, the Time of Sale Prospectus, if any, or the Prospectus Supplement.

4.3 The Investor further represents and warrants to, and covenants with, the Company that (a) the Investor has full right, power, authority and capacity to enter into this Agreement and to consummate the transactions contemplated hereby and has taken all necessary action to authorize the execution, delivery and performance of this Agreement, and (b) this Agreement constitutes a valid and binding obligation of the Investor enforceable against the Investor in accordance with its terms, except as enforceability may be limited by applicable bankruptcy, insolvency, reorganization, moratorium or similar laws affecting creditors’ and contracting parties’ rights generally and except as enforceability may be subject to general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law) and except as the indemnification agreements of the Investors herein may be legally unenforceable.

4.4 The Investor understands that nothing in this Agreement or any other materials presented to the Investor in connection with the purchase and sale of the Shares constitutes legal, tax or investment advice. The Investor has consulted such legal, tax and investment advisors as it, in its sole discretion, has deemed necessary or appropriate in connection with its purchase of Units.

4.5 The Investor represents that the final Base Prospectus, dated November 14, 2005, which is a part of the Company’s Registration Statement, has been delivered or otherwise made available to the Investor for its review prior to or in connection with the receipt of this Agreement.

- 7 -

The Investor acknowledges that the Prospectus Supplement and, if applicable, the Time of Sale Prospectus will be delivered, or otherwise made available to the Investor before this Agreement will be deemed to be effective.

4.6 The Investor represents, warrants and agrees that, since the earlier to occur of (i) the date on which the Placement Agents first contacted the Investor about the Offering and (ii) the date that is the tenth (10^th) trading day prior to the date of this Agreement, it has not engaged in any short selling of the Company’s securities, or established or increased any “put equivalent position” as defined in Rule 16(a)-1(h) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”) with respect to the Company’s securities.

4.7 The Investor understands that, upon receipt of a written notice (without notice of the nature or details of the events) from the Company of the commencement of a Black Out Period (as defined below) (each a “Black Out Notice”), the Investor will promptly discontinue disposition of the Warrant Shares pursuant to the Registration Statement until the earlier of (i) the end of the Black Out Period and (ii) the date on which the Investor is advised by the Company of the termination of the Black Out Period and the Investor receives copies of a supplemented or amended prospectus (or until the Investor is advised by the Company that the use of the Prospectus Supplement may be resumed).

5. Representations, Warranties and Covenants of the Company. The Company represents and warrants to, and agrees with, the Investor that:

5.1 (a) The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement on Form S-3 (Registration File No. 333-129166) under the Securities Act, which became effective on November 14, 2005, for the registration under the Securities Act of the Securities. At the time of such filing, the Company met the requirements of Form S-3 under the Securities Act. Such registration statement meets the requirements set forth in Rule 415(a)(1)(x) under the Securities Act and complies with said Rule. The Company will file with the Commission pursuant to Rule 424(b) under the Securities Act, and the rules and regulations (the “Rules and Regulations”) of the Commission promulgated thereunder, a supplement to the form of prospectus included in such registration statement relating to the placement of the Units and the plan of distribution thereof and has advised the Representative of all further information (financial and other) with respect to the Company required to be set forth therein. Such registration statement, including the exhibits thereto, as amended at the date of this Agreement, is hereinafter called the “Registration Statement”; such prospectus in the form in which it appears in the Registration Statement is hereinafter called the “Base Prospectus”; and the supplemented form of prospectus, in the form in which it will be filed with the Commission pursuant to Rule 424(b) (including the Base Prospectus as so supplemented) is hereinafter called the “Prospectus Supplement.” Any reference in this Agreement to the Registration Statement, the Base Prospectus or the Prospectus Supplement shall be deemed to refer to and include the documents incorporated by reference therein (the “Incorporated Documents”) pursuant to Item 12 of Form S-3 which were filed under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), on or before the date of this Agreement, or the issue date of the Base Prospectus or the Prospectus Supplement, as the case may be; and any reference in this Agreement to the terms “amend,” “amendment” or “supplement” with respect to the Registration Statement, the Base Prospectus or the Prospectus Supplement shall be deemed to refer to and include the filing of any document under the Exchange Act after the date of this Agreement, or the issue date of the Base Prospectus or the Prospectus Supplement, as the case may be, deemed to be incorporated therein by reference. All

- 8 -

references in this Agreement to financial statements and schedules and other information which is “contained,” “included,” “described,” “referenced,” “set forth” or “stated” in the Registration Statement, the Base Prospectus or the Prospectus Supplement (and all other references of like import) shall be deemed to mean and include all such financial statements and schedules and other information which is or is deemed to be incorporated by reference in the Registration Statement, the Base Prospectus or the Prospectus Supplement, as the case may be. No stop order suspending the effectiveness of the Registration Statement or the use of the Base Prospectus or the Prospectus Supplement has been issued, and no proceeding for any such purpose is pending or has been initiated or, to the Company’s knowledge, is threatened by the Commission.

5.2 The Registration Statement (and any further documents to be filed with the Commission) contains all exhibits and schedules as required by the Securities Act. Each of the Registration Statement and any post-effective amendment thereto, at the time it became effective, complied in all material respects with the Securities Act and the Exchange Act and the applicable Rules and Regulations and did not and, as amended or supplemented, if applicable, will 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. The Base Prospectus, the Time of Sale Prospectus, if any, and the Prospectus Supplement, each as of its respective date, comply in all material respects with the Securities Act and the Exchange Act and the applicable Rules and Regulations. Each of the Base Prospectus, the Time of Sale Prospectus, if any, and the Prospectus Supplement, as amended or supplemented, did not and will not contain as of the date thereof any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading. The Incorporated Documents, when they were filed with the Commission, conformed in all material respects to the requirements of the Exchange Act and the applicable Rules and Regulations, and none of such documents, when they were filed with the Commission, contained any untrue statement of a material fact or omitted to state a material fact necessary to make the statements therein (with respect to the Incorporated Documents incorporated by reference in the Base Prospectus or Prospectus Supplement, in light of the circumstances under which they were made) not misleading; and any further documents so filed and incorporated by reference in the Base Prospectus, the Time of Sale Prospectus, if any, or Prospectus Supplement, when such documents are filed with the Commission, will conform in all material respects to the requirements of the Exchange Act and the applicable Rules and Regulations, as applicable, and will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in light of the circumstances under which they were made, not misleading. Notwithstanding the foregoing, the Company makes no representations or warranties as to information, if any, contained in or omitted from the Time of Sale Prospectus, if any, or the Prospectus Supplement or any amendment thereof or supplement thereto in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Placement Agent specifically for use in the Registration Statement, the Time of Sale Prospectus, if any, or the Prospectus Supplement, which information the parties hereto agree is limited to the Placement Agents’ Information as defined in Section 16 of the Placement Agent Agreement. No post-effective amendment to the Registration Statement reflecting any facts or events arising after the date thereof which represent, individually or in the aggregate, a fundamental change in the information set forth therein is required to be filed with the Commission. There are no documents required to be filed with the Commission in connection with the transaction contemplated hereby that (x) have not been filed as required pursuant to the Securities Act or (y) will not be filed within the requisite time period. There are no contracts or other documents required to be described in the Base Prospectus, the Time of Sale

- 9 -

Prospectus, if any, or Prospectus Supplement, or to be filed as exhibits or schedules to the Registration Statement, which have not been described or filed as required.

5.3 To the extent necessary to ensure that the Registration Statement is available for sales of the Warrant Shares by the Investors, the Company shall use its reasonable best efforts to keep the Registration Statement continuously effective, supplemented, amended and current until all Warrant Shares have been issued or all Warrants have expired, whichever occurs earlier; provided that such obligation shall expire before such date if the Company delivers to the Investor a written opinion of counsel to the Company that all Investors may resell the Warrant Shares without registration under the Act and without restrictions as to the manner, timing and volume of such sale. Notwithstanding the foregoing, the Company shall not be required to amend or supplement the Registration Statement, any related prospectus or any document incorporated therein by reference and may suspend the availability of the Registration Statement (a “Black Out Period”) for a period of time not to exceed 30 days in each instance and an aggregate of 60 days in any calendar year, (i) upon the occurrence or existence of any pending corporate development or any other material event as a result of which the Registration Statement, any related prospectus or any document incorporated by reference therein as then amended or supplemented would, in the Company’s good faith judgment, contain an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, and (ii) (A) the Company determines in good faith and in its reasonable judgment that the disclosure of such event as such time would not be in the best interests of the Company or (B) the disclosure otherwise relates to a material business transaction which has not yet been publicly disclosed. If a Black Out Period is in effect on the Termination Date (as such term is defined in the Warrant), then the Termination Date shall be extended for the number of calendar days covered by such Black Out Period.

5.4 The Company has been duly organized and is validly existing as a corporation in good standing (or the equivalent thereof, if any) under the laws of its jurisdiction of incorporation, is duly qualified to do business and is in good standing (or the equivalent thereof, if any) as a foreign corporation in each jurisdiction in which its ownership or lease of property or the conduct of its businesses requires such qualification, and has all power and authority necessary to own or hold its properties and to conduct the businesses in which it is engaged, except where the failure to be so qualified and in good standing or have such power or authority would not have, individually or in the aggregate, a material adverse effect on the condition (financial or otherwise), results of operations, business, properties or prospects of the Company and its subsidiaries taken as a whole (a “Material Adverse Effect”).

5.5 The Securities to be issued and sold by the Company hereunder and under any additional Subscription Agreements have been duly and validly authorized and, when issued and delivered against payment therefor as provided herein, will be duly and validly issued, fully paid and nonassessable and free of any preemptive or similar rights. The Securities conform to the description thereof contained in the Base Prospectus, the Prospectus Supplement and the Time of Sale Prospectus, if any.

5.6 The Company has an authorized capitalization as set forth in the Base Prospectus, the Prospectus Supplement and the Time of Sale Prospectus, if any. All of the issued and outstanding shares of capital stock of the Company have been duly and validly authorized and issued, are fully paid and non-assessable, have been issued in compliance with federal and state securities

- 10 -

laws, and conform to the description thereof contained in the Base Prospectus, the Prospectus Supplement and the Time of Sale Prospectus, if any. None of the outstanding shares of Common Stock was issued in violation of any preemptive rights, rights of first refusal or other similar rights to subscribe for or purchase securities of the Company. There are no authorized or outstanding options, warrants, preemptive rights, rights of first refusal or other rights to purchase, or equity or debt securities convertible into or exchangeable or exercisable for, any capital stock of the Company that have been granted by the Company other than those referenced in the Base Prospectus and the Time of Sale Prospectus, if any. The description of the Company’s stock option, stock bonus and other stock plans or arrangements, and the options or other rights granted thereunder, as described in the Base Prospectus and the Time of Sale Prospectus, if any, accurately and fairly present the information required to be shown with respect to such plans, arrangements, options and rights.

5.7 The Company has the full right, power and authority to enter into this Subscription Agreement and to perform and to discharge its obligations hereunder; and this Agreement has been duly authorized, executed and delivered by the Company, and constitutes a valid and binding obligation of the Company enforceable in accordance with its terms, except as limited by (1) applicable bankruptcy, insolvency, reorganization, moratorium and other laws of general application affecting the enforcement of creditors’ rights generally, (ii) general principles of equity, regardless of whether asserted in a proceeding at equity or law, and may be limited by federal or state securities laws and public policy considerations in respect thereof.

5.8 The execution, delivery and performance of this Agreement by the Company and the consummation of the transactions contemplated hereby will not conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, any indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which the Company is a party or by which the Company is bound or to which any of the property or assets of the Company is subject, nor will such actions result in any violation of the provisions of the charter or by-laws of the Company or any statute, law, rule or regulation or any judgment, order or decree of any court or governmental agency or body having jurisdiction over the Company or any of its properties or assets, except for such breach, violation or default that, individually or in the aggregate, would not reasonably be expected to have a Material Adverse Effect.

5.9 No consent, approval, authorization, filing with or order of or registration with, any court or governmental agency or body is required in connection with the transactions contemplated herein, except such as have been obtained or made under the Securities Act or the Exchange Act and such as may be required under the securities, or blue sky, laws of any jurisdiction in connection with the offer and sale of the Units by the Company in the manner contemplated herein and in the Base Prospectus, the Time of Sale Prospectus, if any, and the Prospectus Supplement.

5.10 The financial statements, together with the related notes and schedules, of the Company included in the Base Prospectus, the Prospectus Supplement or the Registration Statement, the Time of Sale Prospectus, if any, or incorporated by reference therein, as the case may be, present fairly the financial condition, results of operations and cash flows of the Company and its consolidated subsidiaries and other consolidated entities as of the dates and for the periods indicated, comply in all material respects with the Securities Act and the Rules and Regulations thereunder, and have been prepared in conformity with generally accepted accounting principles applied on a consistent basis throughout the periods involved. No other financial statements or supporting schedules or exhibits are

- 11 -

required by the Securities Act or the Rules and Regulations thereunder to be included in the Base Prospectus, the Prospectus Supplement or the Registration Statement, the Time of Sale Prospectus, if any, or incorporated by reference therein, as the case may be.

5.11 Except as set forth in the Base Prospectus and the Time of Sale Prospectus, if any, there is no legal or governmental proceeding pending to which the Company is a party or of which any property or assets of the Company is the subject which is required to be described in the Base Prospectus or the Time of Sale Prospectus, if any, and is not described therein, or which, individually or in the aggregate, if determined adversely to the Company, would have a Material Adverse Effect or would prevent or adversely affect the ability of the Company to perform its obligations under this Agreement; and to the best of the Company’s knowledge, no such proceedings are threatened or contemplated by governmental authorities or threatened by others.

5.12 The Company has made all filings, applications and submissions required by, and possesses all approvals, licenses, certificates, certifications, clearances, consents, exemptions, marks, notifications, orders, permits and other authorizations issued by, the appropriate federal, state or foreign regulatory authorities (including, without limitation, the Food and Drug Administration of the U.S. Department of Health and Human Services (the “FDA”), and any other foreign, federal, state or local government or regulatory authorities performing functions similar to those performed by the FDA) necessary to conduct its businesses (collectively, “Permits”), except for such Permits which the failure to obtain would not have a Material Adverse Effect (the “Immaterial Permits”), and is in compliance in all material respects with the terms and conditions of all such Permits other than the Immaterial Permits (the “Required Permits”); all of such Required Permits held by the Company are valid and in full force and effect; there is no pending or, to the Company’s knowledge, threatened action, suit, claim or proceeding which may cause any such Required Permit to be limited, revoked, cancelled, suspended, modified or not renewed and the Company has not received any notice of proceedings relating to the limitation, revocation, cancellation, suspension, modification or non-renewal of any such Required Permit which, individually or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would have a Material Adverse Effect, whether or not arising from transactions in the ordinary course of business, except as set forth in or contemplated by the Base Prospectus or the Prospectus Supplement.

6. Survival of Representations, Warranties and Agreements. Notwithstanding any investigation made by any party to this Agreement or by the Placement Agents, all covenants, agreements, representations and warranties made by the Company and the Investor herein will survive for two years after the Closing

7. Notices. All notices, requests, consents and other communications hereunder will be in writing, will be mailed (a) if within the domestic United States by first-class registered or certified airmail, or nationally recognized overnight express courier, postage prepaid, or by facsimile or (b) if delivered from outside the United States, by International Federal Express or facsimile, and will be deemed given (i) if delivered by first-class registered or certified mail domestic, three business days after so mailed, (ii) if delivered by nationally recognized overnight carrier, one business day after so mailed, (iii) if delivered by International Federal Express, two business days after so mailed and (iv) if delivered by facsimile, upon electric confirmation of receipt and will be delivered and addressed as follows:

GTC Biotherapeutics, Inc.

175 Crossing Boulevard

Framingham, MA 01702

Attention: President

Phone: (508)  ###-###-####

Telecopy: (508)  ###-###-####

- 12 -

with copies to:

Edwards Angell Palmer & Dodge LLP

111 Huntington Avenue

Boston, MA 02199

Attention: Nathaniel S. Gardiner, Esq.

Phone: (617)  ###-###-####

Telecopy: (617)  ###-###-####

(b) if to the Investor, at its address on the Signature Page hereto, or at such other address or addresses as may have been furnished to the Company in writing.

8. Changes. This Agreement may not be modified or amended except pursuant to an instrument in writing signed by the Company and the Investor.

9. Headings. The headings of the various sections of this Agreement have been inserted for convenience of reference only and will not be deemed to be part of this Agreement.

10. Severability. In case any provision contained in this Agreement should be invalid, illegal or unenforceable in any respect, the validity, legality and enforceability of the remaining provisions contained herein will not in any way be affected or impaired thereby.

11. Governing Law. This Agreement will be governed by, and construed in accordance with, the internal laws of the State of New York, without giving effect to the principles of conflicts of law that would require the application of the laws of any other jurisdiction.

12. Counterparts. This Agreement may be executed in two or more counterparts, each of which will constitute an original, but all of which, when taken together, will constitute but one instrument, and will become effective when one or more counterparts have been signed by each party hereto and delivered to the other parties. The Company and the Investor acknowledge and agree that the Company shall deliver its counterpart to the Investor along with the Prospectus Supplement (or if no physical Prospectus Supplement is delivered, when an electronic version of the Prospectus Supplement is available to the Investor).

13. Confirmation of Sale. The Investor acknowledges and agrees that such Investor’s receipt of the Company’s counterpart to this Agreement, together with the Prospectus Supplement (or if the Prospectus Supplement is otherwise made available to the Investor), shall constitute written confirmation of the Company’s sale of Shares to such Investor.

- 13 -

14. Termination. In the event that the Placement Agreement is terminated by the Placement Agents pursuant to the terms thereof, this Agreement shall terminate without any further action on the part of the parties hereto.

The Company has filed a registration statement (Registration No. 333-129166, including a base prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the base prospectus in that registration statement and other documents the Company has filed with the SEC for more complete information about the Company and this offering. You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, the Company or any placement agent participating in the offering will arrange to send you the Base Prospectus if you request it by calling toll-free ###-###-####.

- 14 -

EXHIBIT A

FORM OF WARRANT

[See Exhibit 4.1 hereto]

EXHIBIT B

GTC BIOTHERAPEUTICS, INC.

INVESTOR QUESTIONNAIRE

Pursuant to Section 3 of Annex I to the Agreement, please provide us with the following information: