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                                                                 Exhibit 10.53


                          REGISTRATION RIGHTS AGREEMENT

      REGISTRATION RIGHTS AGREEMENT (this "Agreement"), dated as of March 20,
1998, by and between GENZYME TRANSGENICS CORPORATION, a Massachusetts
corporation (the "Company"), and the undersigned investors (together with their
affiliates and any assignee or transferee of all of their rights hereunder, the
"Initial Investors").

      WHEREAS:

      A. In connection with the Securities Purchase Agreement by and among the
parties hereto of even date herewith (the "Securities Purchase Agreement"), the
Company has agreed, upon the terms and subject to the conditions contained
therein, to issue and sell, in the aggregate, to the Initial Investors (i)
20,000 shares of its Series A Convertible Preferred Stock (the "Preferred
Stock") that are convertible into shares (the "Conversion Shares") of the
Company's common stock, par value $.01 per share (the "Common Stock"), upon the
terms and subject to the limitations and conditions set forth in the Vote of
Directors Establishing a Series of a Class of Stock with respect to such
Preferred Stock (the "Certificate of Designation") and (ii) warrants (the
"Warrants") to acquire Four Hundred Thousand (400,000) shares of Common Stock
(the "Warrant Shares"), upon the terms and subject to the limitations and
conditions set forth in the Warrants dated of even date herewith; and

      B. To induce the Initial Investors to execute and deliver the Securities
Purchase Agreement, the Company has agreed to provide certain registration
rights under the Securities Act of 1933, as amended, and the rules and
regulations thereunder, or any similar successor statute (collectively, the
"1933 Act"), and applicable state securities laws.

      NOW, THEREFORE, in consideration of the premises and the mutual covenants
contained herein and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Company and the Initial
Investors hereby agree as follows:
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      1.    DEFINITIONS.

            a. As used in this Agreement, the following terms shall have the
following meanings:

                  (i) "Investors" means the Initial Investors and any transferee
or assignee who agrees to become bound by the provisions of this Agreement in
accordance with Section 9 hereof.

                  (ii) "register," "registered," and "registration" refer to a
registration effected by preparing and filing a Registration Statement or
Statements in compliance with the 1933 Act and pursuant to Rule 415 under the
1933 Act or any successor rule providing for offering securities on a continuous
basis ("Rule 415"), and the declaration or ordering of effectiveness of such
Registration Statement by the United States Securities and Exchange Commission
(the "SEC").

                  (iii) "Registrable Securities" means the Conversion Shares and
the Warrant Shares (including any Conversion Shares issuable with respect to
Conversion Default Payments under the Certificate of Designation or in
redemption of any Preferred Stock and any Warrant Shares issuable with respect
to Exercise Default Payments under the Warrants) issued or issuable with respect
to the Warrants and the Preferred Stock and any shares of capital stock issued
or issuable, from time to time (with any adjustments), as a distribution on or
in exchange for or otherwise with respect to any of the foregoing. As to any
particular securities, such Securities shall cease to be Registrable Securities
when they have been sold pursuant to an effective registration statement or in
compliance with Rule 144 or are eligible to be sold pursuant to Rule 144(k)
under the 1933 Act (or any similar rule then in force).

                  (iv) "Registration Statement" means a registration statement
of the Company under the 1933 Act.

            b. 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 prepare, and, on or
prior to the date which is twenty (20) business days after the date of the
Closing under the Securities Purchase Agreement (the "Closing Date"), file with
the SEC a Registration Statement on Form S-3 and pursuant to Rule 415 (or, if
Form S-3 is not then available, on Form S-1 (at the time provided for in Section
2(e)), to effect a registration of all of the Registrable Securities covering
the resale of the Registrable Securities underlying the Preferred Stock and
Warrants issued or issuable pursuant to the Securities Purchase Agreement, which
Registration Statement, to the extent allowable under the 1933 Act and the Rules
promulgated thereunder (including Rule 416), shall state that such Registration
Statement also covers such indeterminate number of additional shares of Common
Stock as may become issuable upon conversion of the Preferred Stock and exercise
of the Warrants (i) to prevent dilution resulting from stock splits, stock
dividends or similar transactions or (ii) by reason of changes in the Conversion
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Price of the Preferred Stock in accordance with the terms of the Certificate of
Designation or the Exercise Price of the Warrants in accordance with the terms
thereof. The number of shares of Common Stock initially included in such
Registration Statement shall be no less than two (2) times the sum of the number
of Conversion Shares and Warrant Shares that are then issuable upon conversion
of the Preferred Stock or exercise of the Warrants without regard to any
limitation on the Investors' ability to convert the Preferred Stock or Warrants.

            b. Underwritten Offering. If any offering pursuant to a Registration
Statement pursuant to Section 2(a) hereof involves an underwritten offering, the
Investors who hold a majority in interest of the Registrable Securities subject
to such underwritten offering, with the consent of the Initial Investors, shall
have the right to select one legal counsel and an investment banker or bankers
and manager or managers to administer the offering, which investment banker or
bankers or manager or managers shall be reasonably satisfactory to the Company.

            c. Payments by the Company. The Company shall use best efforts to
(A) obtain effectiveness of the Registration Statement as soon as practicable,
(B) exclusive of Allowed Delays, maintain the effectiveness of such Registration
Statement and the ability of the Investors to sell Registrable Securities
pursuant thereto, and (C) maintain the listing of the Common Stock for quotation
on the Nasdaq, NYSE or AMEX and trading thereon after the Registration Statement
has been declared effective If (i) the Registration Statement(s) covering the
Registrable Securities required to be filed by the Company pursuant to Section
2(a) hereof is not declared effective by the SEC within ninety (90) days after
the Closing Date or if, after the Registration Statement has been declared
effective by the SEC, sales cannot be made pursuant to the Registration
Statement, or (ii) the Common Stock is not listed or included for quotation on
any one or more of the Nasdaq National Market ("Nasdaq"), the New York Stock
Exchange (the "NYSE") or the American Stock Exchange (the "AMEX") after being so
listed or included for quotation, then the Company will make payments to the
Investors in such amounts and at such times as shall be determined pursuant to
this Section 2(c) as partial relief for the damages to the Investors by reason
of any such delay in or reduction of their ability to sell the Registrable
Securities (which remedy shall not be exclusive of any other remedies available
at law or in equity). The Company shall pay to each holder of the Preferred
Stock or Registrable Securities an amount equal to the face value of the
Preferred Stock ("Aggregate Share Price") multiplied by two hundredths (.020)
(or, solely for the first month of any period of delay in the initial
effectiveness of the Registration Statement after the end of such 90-day period,
one hundredth (.010)) times the sum of: (i) the number of months (prorated for
partial months) after the end of such 90-day period and prior to the date the
Registration Statement is declared effective by the SEC; provided, however, that
there shall be excluded from such period any delays which are solely
attributable to changes required by the Investors in the Registration Statement
with respect to information relating to the Investors, including, without
limitation, changes to the plan of distribution, or to the failure of the
Investors to conduct their review of the Registration Statement pursuant to
Section 3(h) below in a reasonably prompt manner; (ii) exclusive of Allowed
Delays (as defined below), the number of months (prorated for partial months)
that sales cannot be made pursuant to the Registration Statement after the
Registration Statement has been declared effective (including, without
limitation, when sales cannot be made by reason of the Company's failure to
properly
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supplement or amend the prospectus included therein in accordance with the terms
of this Agreement or when such prospectus otherwise contains a material
misstatement or omission) and (iii) exclusive of Allowed Delays the number of
months (prorated for partial months) that the Common Stock is not listed or
included for quotation on the Nasdaq, NYSE or AMEX or that trading thereon is
halted after the Registration Statement has been declared effective. (For
example, if the Registration Statement becomes effective one (1) month after the
end of such 90-day period, the Company would pay $20,000 for each $1,000,000 of
Purchase Price. If thereafter, sales could not be made pursuant to the
Registration Statement for an additional period of one (1) month (exclusive of
Allowed Delays), the Company would pay an additional $20,000 for each $1,000,000
of Purchase Price. Such amounts shall be paid in cash or, at each Investor's
option, may be convertible into Common Stock at the "Conversion Price" (as
defined in the Certificate of Designation).

Notwithstanding anything herein to the contrary, if the Company (1) fails to
cause the Registration Statement to be declared effective on or before the date
that is one hundred eighty (180) days following the Closing Date in a manner
which would allow the sale of Registrable Securities; or (2) such Registration
Statement lapses in effect (or sales otherwise cannot be made by the Holders
thereunder, whether by reason of the Company's failure to amend or supplement
the prospectus included therein in accordance with the Registration Rights
Agreement or otherwise) for more than forty-five (45) consecutive days or
seventy-five (75) days in any twelve (12) month period after such Registration
Statement becomes effective; or (3) the Common Stock is not listed or included
for quotation on the Nasdaq, NYSE or AMEX or that trading thereon is halted
after the Registration Statement has been declared effective for more than for
an aggregate of twenty (20) trading days or more in any twelve (12) month
period; then in each case the calculation of the payments to be made to the
Holders pursuant to the third sentence of the first paragraph of this Section
2(c ) shall be based upon the Aggregate Share Price multiplied by three
hundredths (.030) for the time periods specified in such sentence.

Any shares of Common Stock issued upon conversion of the foregoing amounts shall
be Registrable Securities. If any Investor desires to convert the amounts due
hereunder into Registrable Securities, it shall so notify the Company in writing
within two (2) business days of the date on which such amounts are first payable
in cash and such amounts shall be so convertible (pursuant to the mechanics set
forth under Article __ of the Certificate of Designation), beginning on the last
day upon which the cash amount would otherwise be due in accordance with the
following sentence. Payments of cash pursuant hereto shall be made within five
(5) days after the end of each period that gives rise to such obligation,
provided that, if any such period extends for more than thirty (30) days,
interim payments shall be made for each such thirty (30) day period. The term
"Purchase Price" means the purchase price paid by the Investors for the
Preferred Stock.

If at any time during the Registration Period, counsel to the Company should
determine in good faith that the filing of the Registration Statement or the
compliance by the Company with its disclosure obligations in connection with the
Registration Statement may require the disclosure of information which the Board
of Directors of the Company has identified as material and which the Board of
Directors has determined that the Company has a bona fide
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business purpose for preserving as confidential, the Company shall promptly, (i)
notify the Investors in writing of the existence of (but in no event, without
the prior written consent of an Investor, shall the Company disclose to such
investor any of the facts or circumstances regarding) material non-public
information and (ii) advise the Investors in writing to cease all sales under
the Registration Statement until such information is disclosed to the public or
ceases to be material. In such instance, the Company's obligation to make
payments under this Section 2(c) shall be suspended for a period (an "Allowed
Delay") expiring upon the earlier to occur of (A) the date on which such
material information is disclosed to the public or ceases to be material or the
Company is able to so comply with its disclosure obligations or (B) 15 trading
days after the Company first notifies the Investor of such good faith
determination. There shall not be more than two (2) Allowed Delays in any twelve
(12) month period nor more than three (3) Allowed Delays in any twenty-four (24)
month period.

            d. Piggy-Back Registrations. If at any time prior to the expiration
of the Registration Period (as hereinafter defined) at which time no
Registration Statement is then effective with resepct to the Registrable
Securities, the Company shall file with the SEC a Registration Statement
relating to an offering for its own account or the account of others (unless
inclusion therein would require the consent of such other party, and the Company
is unable, despite exercise of good faith efforts, to obtain such consent) under
the 1933 Act of any of its equity securities (other than on Form S-4 or Form S-8
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, stock purchase or other employee
benefit plans), the Company shall send to each Investor who is entitled to
registration rights under this Section 2(d) written notice of such determination
and, if within fifteen (15) days after the effective date of such notice, such
Investor shall so request in writing, the Company shall include in such
Registration Statement all or any part of the Registrable Securities such
Investor requests to be registered, except that if, in connection with any
underwritten public offering for the account of the Company the managing
underwriter(s) thereof shall impose a limitation on the number of shares of
Common Stock which may be included in the Registration Statement because, in
such underwriter(s)' judgment, marketing or other factors dictate such
limitation is necessary to facilitate public distribution, then the Company
shall be obligated to include in such Registration Statement only such limited
portion of the Registrable Securities with respect to which such Investor has
requested inclusion hereunder as the underwriter shall permit; provided,
however, that the Company shall not exclude any Registrable Securities unless
the Company has first excluded all outstanding securities, the holders of which
are not entitled to inclusion of such securities in such Registration Statement;
and provided, further, however, that, after giving effect to the immediately
preceding proviso, any exclusion of Registrable Securities shall be made pro
rata with holders of other securities having the right to include such
securities in the Registration Statement other than holders of securities not
subject to a similar cut-back provision. No right to registration of Registrable
Securities under this Section 2(d) shall be construed to limit any registration
required under Section 2(a) hereof. If an offering in connection with which an
Investor is entitled to registration under this Section 2(d) is an underwritten
offering, then each Investor whose Registrable Securities are included in such
Registration Statement shall, unless otherwise agreed by the Company, offer and
sell such Registrable Securities in an underwritten offering using the same
underwriter or underwriters and, subject to the
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provisions of this Agreement, on the same terms and conditions as other shares
of Common Stock included in such underwritten offering.

            e. Eligibility for Form S-3. The Company represents and warrants
that it meets the registrant eligibility and transaction requirements for the
use of Form S-3 for registration of the sale by the Investors of the Registrable
Securities and the Company shall file all reports required to be filed by the
Company with the SEC in a timely manner so as to maintain such eligibility for
the use of Form S-3. In the event that the Company is advised by the SEC that it
is not eligible to use Form S-3 in connection with the registration of the
Registrable Securities, it shall file a Registration Statement covering the
Registrable Securities on Form S-1 or other available form as promptly as
practicable and not more than 20 business days after such advice from the SEC,
and the Company shall use its best efforts to obtain eligibility to use Form S-3
as promptly as practicable thereafter and shall convert, prior to its
effectiveness,the Form S-1 Registration Statement to a Form S-3 Registration
Statement as soon as it is permitted to do so thereafter.

            f. Rule 416. The Company and the Investors each acknowledge that,
absent guidance from the SEC or other definitive authority to the contrary, an
indeterminate number of Registrable Securities shall be registered pursuant to
Rule 416 under the Securities Act so as to include in such Registration
Statement any and all Registrable Securities which may become issuable (i) as a
result of stock splits, stock dividends or similar transactions and (ii) by
reason of reductions in the Conversion Price of the Preferred Stock in
accordance with the terms thereof, including, but not limited to, the terms
which cause the Conversion Price to decrease to the extent the closing bid price
of the Common Stock decreases (collectively, the "Rule 416 Securities"). In this
regard, the Company agrees to take all steps necessary to ensure that all
Registrable Securities are registered pursuant to Rule 416 under the Securities
Act in the Registration Statement and, absent guidance from the SEC or other
definitive authority to the contrary, the Company shall affirmatively support
and not take any action adverse to the position that the Registration Statements
filed hereunder cover all of the Rule 416 Securities. If the Company determines
that the Registration Statements filed hereunder do not cover all of the Rule
416 Securities, the Company shall immediately provide to each Investor written
notice (a "Rule 416 Notice") setting forth the basis for the Company's position
and the authority therefor.

      3.    OBLIGATIONS OF THE COMPANY.

      In connection with the registration of the Registrable Securities, the
Company shall have the following obligations:

            a. The Company shall prepare and, on or prior to the date which is
twenty (20) business days after the Closing Date, file with the SEC, a
Registration Statement with respect to the number of Registrable Securities
provided in Section 2(a), and thereafter use its best efforts to cause such
Registration Statement relating to Registrable Securities to become effective as
soon as possible after such filing, and keep the Registration Statement
effective pursuant to Rule 415 at all times until such date as is the earlier of
(i) the date on which all of the Registrable Securities have been sold and (ii)
the date on which the Registrable Securities (in the opinion of counsel to the
Initial Investors) may be immediately sold without restriction
<PAGE>

(including without limitation as to volume by each holder thereof) without
registration under the 1933 Act (the "Registration Period"), which Registration
Statement (including any amendments or supplements thereto and prospectuses
contained therein) 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.

            b. The Company shall prepare and file with the SEC such amendments
(including post-effective amendments) and supplements to the Registration
Statement and the prospectus used in connection with the Registration Statement
as may be necessary to keep the Registration Statement effective at all times
during the Registration Period, and, during such period, comply with the
provisions of the 1933 Act with respect to the disposition of all Registrable
Securities of the Company covered by the Registration Statement until such time
as all of such Registrable Securities have been disposed of in accordance with
the intended methods of disposition by the seller or sellers thereof as set
forth in the Registration Statement. In the event that Rule 416 is determined by
the SEC not to permit the registration of an indeterminate number of shares, and
the number of shares available under a Registration Statement filed pursuant to
this Agreement is insufficient to cover all of the Registrable Securities issued
or issuable upon conversion of the Preferred Stock or exercise of the Warrants,
the Company shall amend the Registration Statement, or file a new Registration
Statement (on the short form available therefore, if applicable), or both, so as
to cover all of the Registrable Securities, in each case, as soon as
practicable, but in any event within twenty (20) business days after the
necessity therefor arises (based on the market price of the Common Stock and
other relevant factors on which the Company reasonably elects to rely). The
Company shall use its best efforts to cause such amendment and/or new
Registration Statement to become effective as soon as practicable following the
filing thereof. The provisions of Section 2(c) above shall be applicable with
respect to such obligation, with the ninety (90) days running from the day after
the date on which the Company reasonably first determines (or reasonably should
have determined) the need therefor.

            c. The Company shall furnish to each Investor whose Registrable
Securities are included in the Registration Statement and its legal counsel (i)
promptly after the same is prepared and publicly distributed, filed with the
SEC, or received by the Company, one copy of the Registration Statement and any
amendment thereto, each preliminary prospectus and prospectus and each amendment
or supplement thereto, and, in the case of the Registration Statement referred
to in Section 2(a), each letter written by or on behalf of the Company to the
SEC or the staff of the SEC, and each item of correspondence from the SEC or the
staff of the SEC, in each case relating to such Registration Statement (other
than any portion of any thereof which contains information for which the Company
has sought confidential treatment), and (ii) such number of copies of a
prospectus, including a preliminary prospectus, and all amendments and
supplements thereto and such other documents as such Investor may reasonably
request in order to facilitate the disposition of the Registrable Securities
owned by such Investor. The Company will immediately notify each Investor by
facsimile of the effectiveness of the Registration Statement or any
post-effective amendment. The Company will promptly respond to any and all
comments received from the SEC, with a view towards causing any Registration
Statement or any amendment thereto to be declared effective by the SEC as soon
as practicable and shall promptly file an acceleration request as soon as
practicable
<PAGE>

following the resolution or clearance of all SEC comments or, if applicable,
following notification by the SEC that the Registration Statement or any
amendment thereto will not be subject to review.

            d. The Company shall use best efforts to (i) register and qualify
the Registrable Securities covered by the Registration Statement under such
other securities or "blue sky" laws of such jurisdictions in the United States
as the Investors who hold a majority-in-interest of the Registrable Securities
being offered reasonably request, (ii) 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) take such other
actions as may be necessary to maintain such registrations and qualifications in
effect at all times during the Registration Period, and (iv) 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 (a) qualify to do
business in any jurisdiction where it would not otherwise be required to qualify
but for this Section 3(d), (b) subject itself to general taxation in any such
jurisdiction, (c) file a general consent to service of process in any such
jurisdiction, (d) provide any undertakings that cause the Company undue expense
or burden, or (e) make any change in its charter or bylaws, which in each case
the Board of Directors of the Company determines to be contrary to the best
interests of the Company and its stockholders.

            e. In the event Investors who hold a two-thirds majority-in-interest
of the Registrable Securities being offered in an offering registered hereunder
select underwriters for the offering, the Company shall enter into and perform
its obligations under an underwriting agreement, in usual and customary form,
including, without limitation, customary indemnification and contribution
obligations, with the underwriters of such offering.

            f. As promptly as practicable after becoming aware of such event,
the Company shall notify each Investor of the happening of any event, of which
the Company has knowledge, as a result of which the prospectus included in the
Registration Statement, as then in effect, includes an untrue statement of a
material fact or omits to state a material fact required to be stated therein or
necessary to make the statements therein not misleading, and use its best
efforts promptly (but subject to Allowed Delays as set forth in Section 2(c)) to
prepare a supplement or amendment to the Registration Statement 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.

            g. The Company shall use its best efforts to prevent the issuance of
any stop order or other suspension of effectiveness of a Registration Statement,
and, if such an order is issued, to obtain the withdrawal of such order at the
earliest possible moment and to notify each Investor who holds Registrable
Securities being sold (or, in the event of an underwritten offering, the
managing underwriters) of the issuance of such order and the resolution thereof.

            h. The Company shall permit a single firm of counsel designated by
the Initial Investors to review the Registration Statement and all amendments
and supplements thereto (as well as all requests for acceleration or
effectiveness thereof) a reasonable period of
<PAGE>

time prior to their filing with the SEC, and not file any document in a form to
which such counsel reasonably objects and will not request acceleration of the
Registration Statement without prior notice to such counsel. The sections of the
Registration Statement covering information with respect to the Investors, the
Investors' beneficial ownership of securities of the Company or the Investors'
intended method of disposition of Registrable Securities shall conform to the
information provided to the Company by the Investors.

            i. The Company shall make generally available to its security
holders as soon as practical, but not later than ninety (90) days after the
close of the period covered thereby, an earnings statement (in form complying
with the provisions of Rule 158 under the 1933 Act) covering a twelve-month
period beginning not later than the first day of the Company's fiscal quarter
next following the effective date of the Registration Statement.

            j. At the request of any Investor, the Company shall furnish, on the
date that Registrable Securities are delivered to an underwriter, if any, for
sale in connection with the Registration Statement (i) an opinion, dated as of
such date, from counsel representing the Company for purposes of such
Registration Statement, in form, scope and substance as is customarily given in
an underwritten public offering, addressed to the underwriters and the Investors
and (ii) a letter, dated such date, from the Company's independent certified
public accountants in form and substance as is customarily given by independent
certified public accountants to underwriters in an underwritten public offering,
addressed to the underwriters and the Investors.

            k. The Company shall make available for inspection by (i) any
Investor, (ii) any underwriter participating in any disposition pursuant to the
Registration Statement, (iii) one firm of attorneys and one firm of accountants
or other agents retained by the Initial Investors, (iv) one firm of attorneys
and one firm of accountants or other agents retained by all other Investors, and
(v) one firm of attorneys retained by all such underwriters (collectively, the
"Inspectors") all pertinent financial and other records, and pertinent corporate
documents and properties of the Company (collectively, the "Records"), as shall
be reasonably deemed necessary by each Inspector to enable each Inspector to
exercise its due diligence responsibility, and cause the Company's officers,
directors and employees to supply all information which any Inspector may
reasonably request for purposes of such due diligence; provided, however, that
each Inspector shall hold in confidence and shall not make any disclosure
(except to an Investor) of any Record or other information which the Company
determines in good faith to be confidential, and of which determination the
Inspectors are so notified, unless (a) the disclosure of such Records is
necessary to avoid or correct a misstatement or omission in any Registration
Statement, (b) the release of such Records is ordered pursuant to a subpoena or
other order from a court or government body of competent jurisdiction, or (c)
the information in such Records has been made generally available to the public
other than by disclosure in violation of this or any other agreement. The
Company shall not be required to disclose any confidential information in such
Records to any Inspector until and unless such Inspector shall have entered into
confidentiality agreements (in form and substance satisfactory to the Company)
with the Company with respect thereto, substantially in the form of this Section
3(k). Each Investor agrees that it shall, upon learning that disclosure of such
Records is sought in or by a court or governmental body of competent
jurisdiction or through other
<PAGE>

means, give prompt notice to the Company and allow the Company, at its expense,
to undertake appropriate action to prevent disclosure of, or to obtain a
protective order for, the Records deemed confidential. Nothing herein (or in any
other confidentiality agreement between the Company and any Investor) shall be
deemed to limit the Investor's ability to sell Registrable Securities in a
manner which is otherwise consistent with applicable laws and regulations.

            l. 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 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, (iii) the
release of such information is ordered pursuant to a subpoena or other 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 or any other agreement. The Company agrees that
it shall, upon learning that disclosure of such information concerning an
Investor is sought in or by a court or governmental body of competent
jurisdiction or through other means, give prompt notice to such Investor prior
to making such disclosure, and allow the Investor, at its expense, to undertake
appropriate action to prevent disclosure of, or to obtain a protective order
for, such information.

            m. The Company shall (i) cause all the Registrable Securities
covered by the Registration Statement to be listed on each national securities
exchange on which securities of the same class or series issued by the Company
are then listed, if any, if the listing of such Registrable Securities is then
permitted under the rules of such exchange, or (ii) secure the designation and
quotation, of all the Registrable Securities covered by the Registration
Statement on the Nasdaq National Market System or, if not eligible for the
Nasdaq National Market System on the Nasdaq Small Cap and, without limiting the
generality of the foregoing, to arrange for at least two market makers to
register with the Nasdaq National Market System as such with respect to such
Registrable Securities.

            n. The Company shall provide a transfer agent and registrar, which
may be a single entity, for the Registrable Securities not later than the
effective date of the Registration Statement.

            o. The Company shall cooperate with the Investors who hold
Registrable Securities being offered and the managing underwriter or
underwriters, if any, to facilitate the timely preparation and delivery of
certificates representing Registrable Securities to be offered pursuant to the
Registration Statement and enable such certificates to be in such denominations
or amounts, as the case may be, as the managing underwriter or underwriters, if
any, or the Investors may reasonably request and registered in such names as the
managing underwriter or underwriters, if any, or the Investors may request, and,
within three (3) business days after a Registration Statement which includes
Registrable Securities is ordered effective by the SEC, the Company shall
deliver and shall cause legal counsel selected by the Company to deliver to the
transfer agent for the Registrable Securities (with copies to the Investors
whose Registrable Securities are included in such Registration Statement) an
<PAGE>

instruction in the form attached hereto as Exhibit 1 and an opinion from such
counsel and a letter from the Company, which letter has been acknowledged by the
Company's transfer agent as sufficient to permit the issuance of unlegended
Conversion Shares and Warrant Shares which are not subject to a stop transfer
notation in the form attached hereto as Exhibit 2.

            p. The Company shall take all other reasonable actions necessary to
expedite and facilitate disposition by the Investors of Registrable Securities
pursuant to the Registration Statement.

            q. At the request of any Investor, the Company shall prepare and
file with the SEC such amendments (including post-effective amendments) and
supplements to a Registration Statement and the prospectus used in connection
with the Registration Statement as may be necessary in order to change the plan
of distribution set forth in such Registration Statement.

            r. The Company shall comply with all applicable laws related to a
Registration Statement and offering and sale of securities and all applicable
rules and regulations of governmental authorities in connection therewith
(including without limitation the Securities Act and the Securities Exchange Act
of 1934, as amended, and the rules and regulations promulgated by the SEC.)

      4.    OBLIGATIONS OF THE INVESTORS.

      In connection with the registration of the Registrable Securities, the
Investors shall each, on a several and not a joint basis, have the following
obligations:

            a. 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 registration
of such Registrable Securities and shall execute such documents in connection
with such registration as the Company may reasonably request. At least five (5)
business days prior to the first anticipated filing date of the Registration
Statement, the Company shall notify each Investor of the information the Company
requires from each such Investor.

            b. Each Investor, by such Investor's acceptance of the Registrable
Securities, agrees to cooperate with the Company as reasonably requested by the
Company in connection with the preparation and filing of the 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 the Registration Statement.

            c. In the event Investors holding a two-thirds majority-in-interest
of the Registrable Securities being registered (with the approval of the Initial
Investors) determine to engage the services of an underwriter, each Investor
agrees to enter into and perform such Investor's obligations under an
underwriting agreement, in usual and customary form, including, without
limitation, customary indemnification and contribution obligations, with
<PAGE>

the managing underwriter of such offering and take such other actions as are
reasonably required in order to expedite or facilitate the disposition of the
Registrable Securities, unless such Investor has notified the Company in writing
of such Investor's election to exclude all of such Investor's Registrable
Securities from the Registration Statement.

            d. Each Investor agrees that, upon receipt of any notice from the
Company of the happening of any event of the kind described in Section 3(f) or
3(g), such Investor will immediately discontinue disposition of Registrable
Securities pursuant to the Registration Statement covering such Registrable
Securities until such Investor's receipt of the copies of the supplemented or
amended prospectus contemplated by Section 3(f) or 3(g) and, if so directed by
the Company, such Investor shall deliver to the Company (at the expense of the
Company) or destroy (and deliver to the Company a certificate of destruction)
all copies in such Investor's possession, of the prospectus covering such
Registrable Securities current at the time of receipt of such notice.

            e. No Investor may participate in any underwritten registration
hereunder unless such Investor (i) agrees to sell such Investor's Registrable
Securities on the basis provided in any underwriting arrangements in usual and
customary form entered into by the Company, (ii) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents reasonably required under the terms of such underwriting
arrangements, including any lock-up agreement with respect to any Registrable
Securities not being sold in such underwriting as may reasonably be requested by
the managing underwriter, and (iii) agrees to pay its pro rata share of all
underwriting discounts and commissions and any expenses in excess of those
payable by the Company pursuant to Section 5 below.

      5.    EXPENSES OF REGISTRATION.

      All reasonable expenses, other than underwriting discounts and
commissions, incurred in connection with registrations, filings or
qualifications pursuant to Sections 2 and 3, including, without limitation, all
registration, listing and qualification fees, printers and accounting fees, the
fees and disbursements of counsel for the Company shall be borne by the Company.
In addition, the Company shall pay all of the Investors' reasonable costs
(including legal fees) incurred in connection with the successful enforcement of
the Investors' rights hereunder.

      6.    INDEMNIFICATION.

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

            a. To the extent permitted by law, the Company will indemnify, hold
harmless and defend (i) each Investor who holds such Registrable Securities,
(ii) the directors, officers, partners, employees, agents and each person who
controls any Investor within the meaning of the 1933 Act or the Securities
Exchange Act of 1934, as amended (the "1934 Act"), if any, (iii) any underwriter
(as defined in the 1933 Act) for the Investors, and (iv) the directors,
officers, partners, employees and each person who controls any such underwriter
<PAGE>

within the meaning of the 1933 Act or the 1934 Act, if any (each, an
"Indemnified Person"), against any joint or several losses, claims, damages,
liabilities or expenses (collectively, together with actions, proceedings or
inquiries by any regulatory or self-regulatory organization, whether commenced
or threatened, in respect thereof, "Claims") to which any of them may become
subject insofar as such Claims arise out of or are based upon: (i) any untrue
statement or alleged untrue statement of a material fact in a Registration
Statement or the omission or alleged omission to state therein a material fact
required to be stated 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 the Company files any amendment thereof or supplement
thereto with the SEC) 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 by the Company of the 1933 Act, the
1934 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 (the matters in the foregoing clauses (i) through (iii)
being, collectively, "Violations"). Subject to the restrictions set forth in
Section 6(c) with respect to the number of legal counsel, the Company shall
reimburse each Indemnified Person, promptly as such expenses are incurred and
are due and payable, for any reasonable 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 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 any Indemnified Person
or underwriter for such Indemnified Person expressly for use in connection with
the preparation of the Registration Statement or any such amendment thereof or
supplement thereto, if such prospectus was timely made available by the Company
pursuant to Section 3(c) hereof; (ii) 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; and
(iii) with respect to any prospectus, shall not inure to the benefit of any
Indemnified Person if the untrue statement or omission of material fact
contained in a preliminary prospectus or final prospectus or any supplement
thereto was corrected on a timely basis in the prospectus, as then amended or
supplemented as required by Section 3(f), such corrected prospectus was timely
made available by the Company pursuant to Section 3(c) hereof, and the
Indemnified Person was promptly advised in writing not to use the incorrect or
incomplete prospectus prior to the use giving rise to a Violation and such
Indemnified Person, notwithstanding such advice, used it. 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.

            b. In connection with any Registration Statement in which an
Investor is participating, each such Investor agrees severally and not jointly
to indemnify, hold harmless and defend, to the same extent and in the same
manner set forth in Section 6(a), the Company, each of its directors, each of
its officers who signs the Registration Statement, each person, if any, who
controls the Company within the meaning of the 1933 Act or the 1934 Act, any
<PAGE>

underwriter and any other stockholder selling securities pursuant to the
Registration Statement or any of its directors or officers or any person who
controls such stockholder or underwriter within the meaning of the 1933 Act or
the 1934 Act (collectively and together with an Indemnified Person, an
"Indemnified Party"), against any Claim to which any of them may become subject,
under the 1933 Act, the 1934 Act or otherwise, insofar as such Claim arises out
of or is based upon any Violation by such Investor, 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) such Investor will reimburse any legal or other expenses (promptly
as such expenses are incurred and are due and payable) reasonably incurred by
them in connection with investigating or defending any such Claim; provided,
however, that the indemnity agreement contained in this Section 6(b) 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; and provided, further, that the Investor's liability
hereunder shall be limited in amount to the net amount of proceeds received by
such seller from the sale of Registrable Securities Such indemnity 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.

Notwithstanding anything to the contrary contained herein, the indemnification
agreement contained in this Section 6(b) with respect to any prospectus 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 receipt by an Indemnified Person or Indemnified
Party under this Section 6 of notice of the commencement of any action
(including any governmental action), 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 the commencement thereof, 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 such indemnifying party shall not be
entitled to assume such defense and an Indemnified Person or Indemnified Party
shall have the right to retain its own counsel with the fees and expenses to be
paid by the indemnifying party, 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. The indemnifying party shall pay for only one
separate legal counsel for the Indemnified Persons or the Indemnified Parties,
as applicable, and such legal counsel shall be selected by Investors holding a
majority-in-interest of the Registrable Securities included in the Registration
Statement to which the Claim relates (with the approval of the Initial
Investors), if the Investors are entitled to indemnification hereunder, or the
<PAGE>

Company, if the Company is entitled to indemnification hereunder, as applicable.
The failure to deliver written notice to the indemnifying party within a
reasonable time of the commencement of any such action 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
actually prejudiced in its ability to defend such action. 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 such expense,
loss, damage or liability is incurred and is due and payable.

      7.    CONTRIBUTION.

      To the extent any indemnification by an indemnifying party is prohibited
or limited by law, the indemnifying party agrees to make the maximum
contribution with respect to any amounts for which it would otherwise be liable
under Section 6 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, (ii) no seller of Registrable Securities guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be
entitled to contribution from any seller of Registrable Securities who was not
guilty of such fraudulent misrepresentation, and (iii) contribution (together
with any indemnification or other obligations under this Agreement) 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.

      8. REPORTS UNDER THE 1934 ACT.

      With a view to making available to the Investors the benefits of Rule 144
promulgated under the 1933 Act or any other similar rule or regulation of the
SEC that may at any time permit the Investors to sell securities of the Company
to the public without registration ("Rule 144"), the Company agrees, for as long
as there shall be any Series A Convertible Preferred Stock, Warrants, Conversion
Shares or Warrant Shares held by an Investor, to:

            a.    make and keep public information available, as those terms are
understood and defined in Rule 144;

            b. file with the SEC in a timely manner all reports and other
documents required of the Company under the 1933 Act and the 1934 Act so long as
the Company remains subject to such requirements (it being understood that
nothing herein shall limit the Company's obligations under Section 4(c) of the
Securities Purchase Agreement) and the filing of such reports and other
documents is required for the applicable provisions of Rule 144; and

            c. furnish to each Investor so long as such Investor owns
Registrable Securities, promptly upon request, (i) a written statement by the
Company that it has complied with the reporting requirements of Rule 144, the
1933 Act and the 1934 Act, (ii) a copy of the most recent annual or quarterly
report of the Company and such other reports and documents so filed by the
Company, and (iii) such other information as may be reasonably requested to
permit the Investors to sell such securities pursuant to Rule 144 without
registration.
<PAGE>

      9.    ASSIGNMENT OF REGISTRATION RIGHTS.

      The rights under this Agreement shall be automatically assignable by the
Investors to any transferee of all or a portion of Registrable Securities if:
(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 within a
reasonable time after such assignment, (ii) the Company is, within a reasonable
time after such transfer or assignment, furnished with written notice of (a) the
name and address of such transferee or assignee, and (b) the securities with
respect to which such registration rights are being transferred or assigned,
(iii) following such transfer or assignment, the further disposition of such
securities by the transferee or assignee is restricted under the 1933 Act and
applicable state securities laws, (iv) at or before the time the Company
receives the written notice contemplated by clause (ii) of this sentence, the
transferee or assignee agrees in writing with the Company to be bound by all of
the provisions contained herein, (v) such transfer shall have been made in
accordance with the applicable requirements of the Securities Purchase
Agreement, and (vi) such transferee shall be an "accredited investor" as that
term defined in Rule 501 of Regulation D promulgated under the 1933 Act and
shall have made appropriate representations to that effect to the Company.

      10.   AMENDMENT OF REGISTRATION RIGHTS.

      Provisions of this Agreement may be amended and the observance thereof may
be waived (either generally or in a particular instance and either retroactively
or prospectively), only with written consent of the Company, the Initial
Investors (to the extent such Initial Investors still own Registrable
Securities) and Investors who hold a two-thirds majority interest of the
Registrable Securities. Any amendment or waiver effected in accordance with this
Section 10 shall be binding upon each Investor and the Company.

      11.   MISCELLANEOUS.

            a. A person or entity is deemed to be a holder of Registrable
Securities whenever such person or entity owns of record such Registrable
Securities. If the Company receives conflicting instructions, notices or
elections from two or more persons or entities with respect to the same
Registrable Securities, the Company shall act upon the basis of instructions,
notice or election received from the registered owner of such Registrable
Securities.

            b. Any notices required or permitted to be given under the terms
hereof shall be sent by certified or registered mail (return receipt requested)
or delivered personally or by courier (including a recognized overnight delivery
service) or by facsimile and shall be effective five days after being placed in
the mail, if mailed by regular U.S. mail, or upon receipt, if delivered
personally or by courier (including a recognized overnight delivery service) or
by facsimile, in each case addressed to a party. The addresses for such
communications shall be:
<PAGE>

      If to the Company:

      Genzyme Transgenics Corporation
      One Mountain Road
      Framingham, MA 01701
      Attn: Chief Financial Officer
      Phone:  508-270-2579
      Fax:  508-270-2303

      With copy to:

      Palmer & Dodge LLP
      One Beacon Street
      Boston, MA  02108-3190
      Attn:  Lynnette C. Fallon, Esq.

If to an Investor: to the address set forth immediately below such Investor's
name on the signature pages to the Securities Purchase Agreement.

            c. 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.

            d. This Agreement shall be enforced, governed by and construed in
accordance with the laws of New York applicable to agreements made and to be
performed entirely within such State. In the event that any provision of this
Agreement is invalid or unenforceable under any applicable statute or rule of
law, then such provision shall be deemed inoperative to the extent that it may
conflict therewith and shall be deemed modified to conform with such statute or
rule of law. Any provision hereof which may prove invalid or unenforceable under
any law shall not affect the validity or enforceability of any other provision
hereof. The parties hereto hereby submit to the exclusive jurisdiction of the
United States Federal Courts located in New York with respect to any dispute
arising under this Agreement or the transactions contemplated hereby.

            e. This Agreement, the Securities Purchase Agreement (including all
schedules and exhibits thereto), and the Warrants 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 Warrants supersede all prior agreements
and understandings among the parties hereto with respect to the subject matter
hereof and thereof.

            f. Subject to the requirements of Section 9 hereof, this Agreement
shall inure to the benefit of and be binding upon the successors and assigns of
each of the parties hereto.
<PAGE>

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

            h. This Agreement may be executed in two or more 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 party hereto by facsimile transmission of a copy of this Agreement
bearing the signature of the party so delivering this Agreement.

            i. 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.

            j. Except as otherwise provided herein, all consents and other
determinations to be made by the Investors pursuant to this Agreement shall be
made by Investors holding a two-thirds majority of the Registrable Securities,
determined as if the all of the shares of Preferred Stock and Warrants then
outstanding have been converted into or exercised for Registrable Securities.

            k. 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.
<PAGE>

      IN WITNESS WHEREOF, the Company and the undersigned Initial Investors have
caused this Agreement to be duly executed as of the date first above written.


GENZYME TRANSGENICS CORPORATION


By:/s/ John B. Green
   -------------------------------
   Name:  John B. Green
   Title: Vice President, Finance

                    [SIGNATURES CONTINUED ONTO NEXT PAGE]
<PAGE>

RGC INTERNATIONAL INVESTORS, LDC

By:  Rose Glen Capital Management, L.P.
      Investment Manager

By: RGC General Partner Corp.


By:     /s/ Wayne D. Block
        -------------------------------
Name:   Wayne D. Block
Its:    Managing Director

RESIDENCE:  Cayman Islands

ADDRESS:

      c/o Rose Glen Capital Management, L.P.
      3 Bala Plaza East, Suite 200
      251 St. Asaphs Road
      Bala Cynwyd, PA  19004
      Fax:        (610) 617-0570
      Telephone:  (610) 617-5900
      Attn:  Wayne Bloch

[SIGNATURES CONTINUED ONTO NEXT PAGE]
<PAGE>

SHEPHERD INVESTMENTS INTERNATIONAL, LTD.


By:/s/ Brian J. Stark
   -------------------------------
       Name:  Brian J. Stark
       Managing Member, Staro Asset Management, LLC
       Investment Manager, Shepherd Investments International, Ltd.
   DATE: 3-20-98


RESIDENCE: British Virgin Islands

      ADDRESS: c/o Staro Asset Management, LLC
               1500 West Market Street, Suite 200
               Mequon, WI 53092
               Fax: (414) 241-7704; and
               Tel: (414) 241-7728 x15
               Attn: Mr. Brian Davidson


STARK INTERNATIONAL


By:/s/ Brian J. Stark
   -------------------------------
       Name:  Brian J. Stark
       Managing Member, Staro Asset Management, LLC
       Investment Manager, Stark International
   DATE:  3-20-98


RESIDENCE: Bermuda

      ADDRESS:    c/o Staro Asset Management, LLC
                  1500 West Market Street, Suite 200
                  Mequon, WI 53092
                  Fax:  (414) 241-7704; and
                  Tel:  (414) 241-7728 x15
                  Attn:  Mr. Brian Davidson