EXHIBIT 10.42

                 PLAN OF REORGANIZATION AND AGREEMENT OF MERGER

        PLAN OF REORGANIZATION AND AGREEMENT OF MERGER ("this Agreement"), dated
as of March 14, 1996, among Repligen Corporation, a Delaware corporation
("Repligen"), Repligen Acquisition Corp., a Delaware corporation ("Newco"),
Glycan Pharmaceuticals, Inc., a Delaware corporation ("Glycan") and, solely for
the purposes of Article 5 hereof, the additional signatories hereto under the
caption "Stockholders" on the signature page hereof (collectively, the
"Stockholders"). As used herein, Glycan and Newco shall be referred to,
together, as the "Constituent Corporations" and, individually, as a "Constituent
Corporation".

                              W I T N E S S E T H:

        WHEREAS, each of the respective Boards of Directors of the Constituent
Corporations and Repligen deem it advisable for the general welfare and
advantage of the Constituent Corporations and their respective shareholders that
the Constituent Corporations merge into a single corporation pursuant to this
Agreement, and the Constituent Corporations respectively desire to so merge
pursuant to this Agreement and pursuant to the applicable provisions of the laws
of the State of Delaware.

        WHEREAS, the respective Boards of Directors of the Constituent
Corporations and Repligen intend that the transactions contemplated in this
Agreement constitute a "reorganization" within the meaning of Section
368(a)(2)(E) of the Internal Revenue Code of 1986, as amended (the "Code").

        NOW, THEREFORE, in consideration of the premises and of the mutual
agreements herein contained, the parties hereby agree as follows:

                                    ARTICLE 1
                                   THE MERGER

        SECTION 1.1.  The Merger.

               (i) Subject to the terms and conditions of this Agreement, at the
Effective Time (as defined below), Newco shall be merged with and into Glycan
(the "Merger") in accordance with the Delaware General Corporation Law (the
"DGCL"), whereupon the separate existence of Newco shall cease, and Glycan shall
be the surviving corporation (the "Surviving Corporation") with the name of
"Glycan Pharmaceuticals, Inc."

               (ii) The consummation of the Merger shall take place at the
Effective Time (as hereinafter defined). Newco and Glycan shall execute and
deliver to the Secretary of State of the State of Delaware a Certificate of
Merger in proper form for filing under the DGCL, and the Merger shall become
effective upon the filing of the Certificate of Merger with the Secretary of
State of the State of Delaware or at such later time as may be specified in the
Certificate of Merger, such time being herein called the "Effective Time."

               (iii) The Merger shall have the effects set forth herein and in
the DGCL. Without limiting the generality of the foregoing, at the Effective
Time (a) the Surviving Corporation shall possess all assets and property of
every description, and every interest therein, wherever located, and the rights,
privileges, immunities, powers, franchises, and authority, of a public as well
as of a private nature, of each of Glycan and Newco and all obligations
belonging to or due each of them shall be vested in the Surviving Corporation
without further act or deed; (b) title to any real estate or any interest
therein vested in either of Glycan or Newco shall not revert or in any way be
impaired by reason of the Merger; (c) all rights of creditors and all liens on
any property of Glycan and Newco shall be preserved unimpaired; and (d) the
Surviving Corporation shall be liable for all the obligations of Glycan and
Newco, and any claim existing, or action or proceeding pending, by or against
either of them, may be prosecuted to judgment with the right of appeal, as if
the Merger had not taken place.

        SECTION 1.2. Effect on Capital Stock. Upon consummation of the Merger at
the Effective Time and without any action on the part of the holders of any
shares of capital stock of Glycan or Newco:

               (i) Glycan Common Stock. Each share of Common Stock, par value
$.01 per share, of Glycan issued and outstanding immediately prior to the
Effective Time (including shares of Common Stock which shall then be held in the
treasury of Glycan) shall thereupon be exchanged for .280 shares of Common
Stock, par value $.01 per share, of Repligen. Options and warrants issued prior
to the date of this Agreement by Glycan shall be assumed by Repligen in the
manner, and shall be exercisable by the holders thereof to the extent, as
provided in Sections 4.2 and 4.3 hereof. At the Effective Time, all shares of
Common Stock of Glycan outstanding immediately prior to the effective Time shall
cease to exist and all certificates representing such shares shall be deemed
cancelled.

               (ii) Newco Common Stock. Each share of Common Stock of Newco
outstanding immediately prior to the Effective Time shall become an issued and
outstanding share of Common Stock of Glycan at the Effective Time. Each
certificate representing immediately prior to the Effective Time issued and
outstanding shares of Common Stock of Newco shall, immediately upon the
Effective Time, evidence ownership of the same number of fully paid,
nonassessable shares of Common Stock of "Glycan Pharmaceuticals, Inc."

               (iii) Treasury Stock. At the Effective Time all shares of Common
Stock of Glycan that shall be then held in its treasury shall cease to exist,
and all certificates representing such shares shall be cancelled.

               (iv) By-laws. The by-laws of Glycan as in effect at the Effective
Time shall, from and after the Effective Time, be and continue to be the by-laws
of the Surviving Corporation unless and until changed as therein provided.

               (v) Officers and Directors. At the Effective Time, the persons
named in Exhibit A hereto shall be the directors and officers of the Surviving
Corporation until their successors have been duly elected and qualified or until
earlier death, resignation or removal in accordance with Certificate of
Incorporation and elected in accordance with the by-laws of the Surviving
Corporation. Walter Herlihy will be elected to the Board of Directors of
Repligen, effective as of the Effective Time of the Merger.

               (vi) Further Action. From time to time, as and when reasonably
requested by the Surviving Corporation, or by its successors or assigns, Glycan
shall execute and deliver or cause to be executed and delivered all such
necessary deeds and other instruments, and shall take or cause to be taken all
such further actions, as the Surviving Corporation, or its successors or assigns
may deem necessary or desirable in order to vest in and confirm to the Surviving
Corporation, and its successors or assigns, title to and possession of all the
property, rights, privileges, powers and franchises referred to herein and
otherwise to carry out the intent and purposes of this Agreement.

               (vii) Appraisal Demands. Notwithstanding anything in this
Agreement to the contrary, shares of Glycan Common Stock which are outstanding
immediately prior to the Effective Time, the holders of which shall have
delivered to Glycan a written demand for appraisal of such shares in the manner
provided in Section 262 of the DGCL ("Dissenting Shares"), shall not be
converted into the right to receive, or be exchangeable for, the shares of
Repligen otherwise issuable in exchange for such shares of Glycan Common Stock
pursuant to this Section 1.2 but, instead, the holders thereof shall be entitled
to payment of the appraised value of such Dissenting Shares in accordance with
the provisions of Section 262 of the DGCL; provided, however, that (i) if any
holder of Dissenting Shares shall subsequently deliver a written withdrawal of
his demand for appraisal of such shares (with the written approval of the
Surviving Corporation, if such withdrawal is not tendered within 60 days after
the Effective Time), or (ii) if any holder fails to establish his entitlement to
appraisal rights as provided in such Section 262 of the DGCL, or (iii) if
neither any holder of Dissenting Shares nor the Surviving Corporation has filed
a petition demanding a determination of the value of all Dissenting Shares
within the time provided in Section 262 of the DGCL, such holder or holders (as
the case may be) shall forfeit the right to appraisal of such shares of Glycan
Common Stock and each of such shares shall thereupon be deemed to have been
converted into the right to receive, and to have become exchangeable for, as of
the Effective Time, the shares of Repligen otherwise issuable in exchange for
such shares of Glycan Common Stock pursuant to this Section 1.2, without any
interest thereon.


        SECTION 1.3 . Exchange of Certificates.

               (i) Exchange Agent. As of the Effective Time, Repligen shall
deposit with Bank of Boston (the "Exchange Agent"), for the benefit of the
holders of shares of Glycan's Common Stock for exchange in accordance with this
Article I, through the Exchange Agent, certificates representing the shares of
Repligen's Common Stock (such shares, together with any dividends or
distributions with respect thereto, being hereinafter referred to as the
"Exchange Fund") issuable pursuant to the Merger in exchange for outstanding
shares of Glycan's Common Stock. The Exchange Agent shall, pursuant to
irrevocable instructions from Repligen, deliver the Common Stock of Repligen
contemplated to be issued pursuant to the Merger to the (non-dissenting)
Stockholders out of the Exchange Fund. The Exchange Fund shall not be used for
any other purpose.

               (ii) Exchange Procedures. As soon as reasonably practicable after
the Effective Time, the Exchange Agent shall mail to each holder of record of a
certificate or certificates which immediately prior to the Effective Time
represented outstanding shares of Glycan's common stock (the "Certificates") (a)
a letter of transmittal (which shall specify that delivery shall be effected,
and risk of loss and title to the Certificates shall pass, only upon delivery of
the Certificates to the Exchange Agent and shall be in such form and have such
other provisions as Repligen and Glycan may reasonably specify) and (b)
instructions for use in effecting the surrender of the Certificates in exchange
for certificates representing shares of Repligen's common stock. Upon surrender
of a Certificate for cancellation to the Exchange Agent or to such other agent
or agents as may be appointed by Repligen and Newco, together with such letter
of transmittal, duly executed, and any other required documents (including a
signed counter-part of this Agreement indicating the intention of such holder to
be bound by the provisions of Article 5 hereof applicable to it), the holder of
such Certificate shall be entitled to receive in exchange therefor a certificate
representing that number of whole shares of Repligen's common stock which such
holder has the right to receive in the Merger pursuant to the provisions of this
Article I, and the Certificate so surrendered shall forthwith be canceled. In
the event of a transfer of ownership of Glycan common stock which is not
registered in the transfer records of Glycan, a certificate representing the
proper number of shares of Repligen common stock may be issued to a transferee
if the Certificate representing such Glycan common stock is presented to the
Exchange Agent, accompanied by all documents required to evidence and effect
such transfer and by evidence that any applicable stock transfer taxes have been
paid. Until surrendered as contemplated by this Section 1.3, each Certificate
shall be deemed at any time after the Effective Time to represent only the right
to receive upon such surrender the certificate representing shares of Repligen
common stock as contemplated by this Section 1.3. The Exchange Agent shall not
be entitled to vote or exercise any rights of ownership with respect to the
Repligen common stock held by it from time to time hereunder, except that it
shall receive and hold all dividends or other distributions paid or distributed
with respect thereto for the account of persons entitled thereto.

               (iii) Distributions with Respect to Unexchanged Shares. No
dividends or other distributions declared or made after the Effective Time with
respect to Repligen's common stock with a record date after the Effective Time
shall be paid to the holder of any unsurrendered Certificate with respect to the
shares of Repligen common stock represented thereby until the holder of record
of such Certificate shall surrender such Certificate, as provided above. Subject
to the effect of applicable laws, following surrender of any such Certificate,
there shall be paid to the record holder of the Certificates representing shares
of Repligen common stock issued in exchange therefor, without interest, (a) the
amount of dividends or other distributions with a record date after the
Effective Time theretofore paid with respect to such shares of Repligen common
stock, and (b) at the appropriate payment date, the amount of dividends or other
distributions with a record date after the Effective Time but prior to surrender
and a payment date subsequent to surrender payable with respect to such shares
of common stock.

               (iv) No Further Ownership Rights in Glycan Common Stock. All
shares of Repligen common stock issued upon the surrender for exchange of shares
of Glycan common stock in accordance with the terms hereof (including any cash
paid pursuant to Section 1.3(iii)) shall be deemed to have been issued in full
satisfaction of all rights pertaining to such shares of Glycan common stock,
subject, however, to the Surviving Corporation's obligation to pay any dividends
or make any other distributions with a record date prior to the Effective Time
which may have been declared or made by Glycan on such shares prior to the
Effective Time and which remain unpaid at the Effective Time, and after the
Effective Time there shall be no further registration of transfers on the stock
transfer books of the Surviving Corporation of the shares of Glycan common stock
which were outstanding immediately prior to the Effective Time. If, after the
Effective Time, Certificates are presented to the Surviving Corporation for any
reason, they shall be canceled and exchanged as provided herein.

               (v) No Fractional Shares. No fractional shares of Common Stock of
Repligen shall be issued in the Merger. The number of shares of Repligen's
common stock issuable in exchange for shares of common stock of Glycan in the
Merger shall in each case be rounded up to the nearest whole number.

               (vi) Termination of Exchange Fund. Any portion of the Exchange
Fund which remains undistributed to the former stockholders of Glycan upon the
first anniversary of the Effective Time shall be delivered to Repligen upon
demand, and any stockholders of Glycan who have not theretofore complied with
this Section 1.3 shall thereafter look only to Repligen in respect of their
claim for Repligen common stock in connection with the Merger and any dividends
or distributions with respect thereto.

               (vii) No Liability. Neither Repligen nor Glycan shall be liable
to any stockholder of Glycan or Repligen, as the case may be, for any shares of
common stock of Repligen or Glycan (or dividends or distributions with respect
thereto) delivered to a public official pursuant to any applicable abandoned
property, escheat or similar law. Any amounts remaining unclaimed by holders of
any such shares two years after the Effective Time (or such earlier date
immediately prior to such time as such amounts would otherwise escheat to or
become property of any governmental entity) shall, to the extent permitted by
applicable law, become the property of Repligen free and clear of any claims or
interest of any such holders or their successors, assigns or personal
representatives previously entitled thereto.

                                    ARTICLE 2
                            REPRESENTATIONS OF GLYCAN

        Glycan hereby represents and warrants to, and agrees with, Repligen and
Newco as follows:

        SECTION 2.1. Organization, Standing and Power. Glycan is a corporation
duly organized, validly existing and in good standing under the laws of
Delaware, has the corporate power to own and lease its properties and to carry
on its business as now being conducted and is duly qualified to do business and
is in good standing in every jurisdiction (including foreign countries) in which
the properties owned or leased by it make such qualification necessary, except
where failure to so qualify is not reasonably likely to have a material adverse
effect on the business operations or prospects of Glycan, such jurisdictions
being set forth in Schedule 2.1 hereto. Glycan has the statutory power to enter
into and perform the terms and provisions of this Agreement.

        SECTION 2.2. Due Execution. The execution, delivery and performance of
this Agreement by Glycan and the consummation by it of the transactions
contemplated hereby have been approved by all necessary corporate action on the
part Glycan and this Agreement and any other agreement or instrument delivered
in connection herewith constitutes the valid and binding obligation of Glycan
enforceable in accordance with its terms, except as such enforceability may be
limited by applicable bankruptcy, insolvency, moratorium, reorganization or
similar laws from time to time in effect which affect creditors' rights
generally and by legal and equitable limitations on the availability of specific
performance and other equitable remedies against Glycan under or by virtue of
this Agreement or such other agreement or instrument.

        SECTION 2.3. No Consents, No Defaults. The execution, delivery and
performance of this Agreement by Glycan and the consummation by it of the
transactions contemplated hereby (i) do not require the consent, waiver,
approval, license or authorization of any person or entity or public authority
which has not been obtained, (ii) do not violate, with or without the giving of
notice or the passage of time or both, in any material respect any provision of
law applicable to Glycan or any of the "Glycan Subsidiaries" (as hereinafter
defined), and (iii) do not conflict with or result in a breach or termination of
any provision of, or constitute a default in any material respect under, or
result in the creation of any lien, charge or encumbrance upon any of the
property or assets of Glycan or the Glycan Subsidiaries pursuant to their
respective certificates of incorporation or by-laws or any mortgage, deed or
trust, indenture or other agreement or instrument, or any order, judgment,
decree, statute, regulation or any other restriction of any kind or character,
to which Glycan or any of the Glycan Subsidiaries (as hereinafter defined) is a
party or by which Glycan or any of the Glycan Subsidiaries may be bound, except
where such conflict, breach or termination is not reasonably likely to have a
material adverse effect on Glycan and its Subsidiaries taken as a whole.

        SECTION 2.4. Subsidiaries. Glycan owns, directly or indirectly, all or a
majority of the outstanding shares of the corporations set forth on Schedule 2.4
hereto. The authorized capital stock, the number of shares duly issued and
outstanding and the number thereof held by Glycan, the jurisdiction of
incorporation and the jurisdictions (including foreign countries) of
qualification of each such corporation are as set forth on Schedule 2.4. The
shares of each such corporation owned by Glycan are fully paid and
nonassessable, and Glycan owns outright all such shares free and clear of all
mortgages, liens or other encumbrances, whatsoever, and none of such shares is
subject to any covenant or other restriction, preventing or limiting the right
to transfer such shares. Each such corporation is a corporation duly organized,
validly existing and in good standing under the laws of the jurisdiction of its
incorporation, has the corporate power to own and lease its properties and to
carry on its business as now being conducted and is duly qualified to do
business and is in good standing in every jurisdiction (including foreign
countries) in which the character of the properties owned or leased by it makes
such qualification necessary, except where failure to so qualify is not
reasonably likely to have a material adverse effect on the business operations
or prospects of Glycan. Such corporations, including ProsCure, Inc.
("ProsCure"), are hereinafter collectively referred to as the "Glycan
Subsidiaries". Glycan does not control, directly or indirectly, or own any
capital stock or other proprietary interest in, any corporation, partnership,
joint venture or other entity except as described in Schedule 2.4 hereto. Glycan
has delivered to Repligen true and complete copies of the certificate of
incorporation and by-laws of Glycan and each of the Glycan Subsidiaries as in
effect on the date hereof, certified by the Secretary of the respective
corporations in the case of by-laws and by the Secretary of State or other
appropriate governmental official of the appropriate jurisdiction in the case of
certificates of incorporation.

        SECTION 2.5. Capitalization. The total authorized capital stock of
Glycan consists solely of 2,000,000 shares of Common Stock, par value $.01 per
share, warrants to acquire a total of 75,000 shares of Common Stock, and options
outstanding to purchase a total of 8,000 shares of Common Stock. As of this
date, there are 870,000 shares of Glycan Common Stock issued and outstanding.
The total authorized capital stock of ProsCure consists solely of 1,700,000
shares of Common Stock, par value $.01 per share, 1,200,000 shares of Preferred
Stock, par value $.01 per share and warrants to purchase a total of 150,000
shares of Common Stock. As of this date, there are 140,000 shares of ProsCure
Common Stock, 1,060,000 shares of ProsCure Series A Preferred Stock, and 113,334
shares of ProsCure Series B Preferred Stock issued and outstanding. All
outstanding shares of capital stock of Glycan and ProsCure have been duly
authorized and validly issued and are fully paid and nonassessable and free of
pre-emptive rights, and none of them is held in treasury. Except as set forth on
Schedule 2.5, there are outstanding (i) no other shares of capital stock or
other voting securities of Glycan or ProsCure, (ii) no securities of Glycan or
ProsCure convertible into or exchangeable for shares of capital stock or voting
securities of Glycan or ProsCure, and (iii) no other options or other rights to
acquire from Glycan or ProsCure, and no obligation of Glycan or ProsCure to
issue, any capital stock, voting securities or securities convertible into or
exchangeable for capital stock or voting securities of Glycan or ProsCure (the
items in clauses (i), (ii) and (iii) being referred to collectively as the
"Glycan Securities"). There are no outstanding obligations of Glycan or ProsCure
to repurchase, redeem or otherwise acquire or purchase any Glycan Securities.

        SECTION 2.6. Officers, Directors, Shareholders. Attached hereto as
Schedule 2.6 is a list of (i) the officers and directors of Glycan and each of
the Glycan Subsidiaries and (ii) all persons owning of record or beneficially
shares of capital stock of Glycan and each of the Glycan Subsidiaries (together
with their respective stockholdings in such corporations).

        SECTION 2.7.  Financial Statements; Financial Matters.

               (i) Financial Statements. Glycan has furnished Repligen with the
unaudited balance sheet of Glycan and its consolidated subsidiaries as of
December 31, 1995 (the "Glycan Interim Balance Sheet"), and the related
unaudited consolidated statements of loss and deficit and changes in financial
position for the period then ended. Such financial statements (a) are in
accordance with the books and records of Glycan and the Glycan Subsidiaries, (b)
are correct and complete, (c) fairly present the financial position and the
results of operations of Glycan and the Glycan Subsidiaries as of the respective
dates indicated (subject, in the case of the unaudited statements, to normal,
recurring adjustments, none of which will be material), and (d) have been
prepared in accordance with generally accepted accounting principles applied on
a consistent basis.

               (ii) Except as and to the extent set forth on the Glycan Interim
Balance Sheet, Glycan and the Glycan Subsidiaries do not have any liability or
obligation of any nature (whether accrued, absolute, contingent or otherwise),
except for liabilities and obligations incurred since January 31, 1996 which (a)
were incurred in the ordinary course of business and (b) would not, individually
or in the aggregate, have a material adverse effect on the business of Glycan
and the Glycan Subsidiaries, taken as a whole.

        SECTION 2.8. Taxes. Glycan and the Glycan Subsidiaries have filed all
tax returns which are required to be filed by them; and all such returns are
true and correct. Glycan and the Glycan Subsidiaries have paid or provided
adequate reserves for all taxes which have become due pursuant to such returns
or pursuant to any assessments received by them or which any of them is
obligated to withhold from amounts owing to any employee, creditor or other
third party. The Federal income tax returns of Glycan and the Glycan
Subsidiaries have never been audited by the Internal Revenue Service. Neither
Glycan nor any of the Glycan Subsidiaries has waived any statute of limitations
in respect of taxes, or has agreed to any extension of time with respect to a
tax assessment or deficiency.

        SECTION 2.9. Real Property. Neither Glycan nor any of the Glycan
Subsidiaries owns any real estate.

        SECTION 2.10. Title. Except as shown in the Glycan Interim Balance Sheet
or in the notes thereto and except for liens, restrictions or encumbrances which
do not interfere with or adversely affect the use of properties and assets owned
by Glycan and the Glycan Subsidiaries, Glycan and each of the Glycan
Subsidiaries own outright all their respective properties and assets (other than
leased properties or assets), free and clear of all mortgages, liens,
restrictions, encumbrances, options, rights of first refusal or other claims
whatsoever.

        SECTION 2.11. Intangible Property. Glycan owns, directly or indirectly,
all patents, patent licenses, trade names, trademarks, service marks, brand
marks, brand names, copyrights, or registrations or licenses thereof or
applications therefor or interests therein, or know-how or other proprietary or
trade rights, the use of which is necessary for the business of Glycan and the
Glycan Subsidiaries as now conducted. As of the date hereof, no suits are
pending or to the knowledge of Glycan threatened against Glycan or the Glycan
Subsidiaries before any court of the United States or any state thereof in which
it is claimed that Glycan or any such subsidiary is in violation or infringement
of any United States patent, patent license, trade name, trademark, service
mark, brand mark, brand name, copyright, know-how or other proprietary or trade
rights of any third party, the outcome of which could have a materially adverse
effect on the consolidated financial condition or results of operations of
Glycan and the Glycan Subsidiaries.

        SECTION 2.12.  Material Contracts.

               (i) Except as set forth on Schedule 2.12, neither Glycan nor any
of the Glycan Subsidiaries is party to or bound by any (a) material lease or
license with respect to any property, real or personal, tangible or intangible,
whether as landlord, tenant, licensor or licensee; (b) agreement, contract, or
indenture relating to the borrowing of money by Glycan or any of the Glycan
Subsidiaries; (c) management agreement, employment, consulting or severance or
"parachute" or other similar contract or arrangement; (d) agreement with any
present or former officer, director or shareholder of Glycan or any of the
Glycan Subsidiaries; or (e) other contract, agreement or other commitment which
involve a payment by Glycan or any of such subsidiaries of more than $25,000 in
one year.

               (ii) Neither Glycan nor any of the Glycan Subsidiaries is in
material breach or material default under any agreement or commitment required
to be set forth in Schedule 2.12 (a "Material Agreement"); and there has not
occurred any event which, after the giving of notice, the lapse of time or
otherwise, would constitute any such default under, or result in any such breach
of, any such Material Agreement.

        SECTION 2.13. Litigation. Attached as Schedule 2.13 is a brief
description of all actions, suits and proceedings pending, or to the best of
Glycan's knowledge, threatened against or affecting Glycan and the Glycan
Subsidiaries or their respective properties or business, at law or in equity or
admiralty and before or by any Federal, state, province or other governmental
body or any arbitration board, domestic or foreign. Glycan has no knowledge or
notice of, or otherwise has any reason to believe that there exist, any grounds
for any other action, suit or proceeding. Neither Glycan nor any of the Glycan
Subsidiaries is, to the knowledge of Glycan, subject to or in default with
respect to any order, writ, injunction or decree of any court or Federal, state,
province or other governmental body, domestic or foreign.

        SECTION 2.14. Certain Activities. Except as set forth in Schedule 2.14
attached hereto, since December 31, 1995, neither Glycan nor any of the Glycan
Subsidiaries has done or agreed to do any of the following: (a) issue any stock
(other than pursuant to the exercise of existing stock options or warrants),
notes, or other Glycan Securities or debt instruments, or grant any options,
warrants or other rights calling for the issue thereof; (b) incur, or become
subject to, any indebtedness, obligation, or liability (absolute or contingent)
except current liabilities and obligations incurred in the ordinary course of
business; (c) pay any obligation or liability (absolute or contingent) other
than current liabilities reflected in or shown on the Glycan Interim Balance
Sheet, and current liabilities incurred since January 31, 1996 in the ordinary
course of business; (d) declare or make any payment of dividends or
distributions of any assets of any kind whatsoever to stockholders or purchase
or redeem any of its stock; (e) purchase or lease any real property; (f)
mortgage, pledge or subject to lien, charge or any other encumbrance of any of
its assets, tangible or intangible; or (g) enter into any transaction other than
in the ordinary course of business.

        SECTION 2.15. Compliance with Laws. Glycan and the Glycan Subsidiaries
have complied in all material respects with all laws, ordinances, regulations
and orders, which have application to its business, the violation of which is
reasonably likely to have a material adverse effect on its financial condition
or results of operation, and possess all governmental licenses and permits
material to and necessary in the conduct of its business, the absence of which
is reasonably likely to have a material adverse effect on its financial
condition or results of operation. All such licenses and permits are in full
force and effect, no violations are or have been recorded in respect to any such
licenses or permits, and no proceeding is pending or threatened to revoke or
limit any such licenses or permits. Each such license or permit shall remain
valid and in full force and effect upon consummation of the Merger without any
restriction or required consent or approval of any third party which will not
have been obtained on or prior to the Effective Time.

        SECTION 2.16. Bank Accounts. Glycan has supplied Repligen with a
complete list of all bank accounts maintained by Glycan and the Glycan
Subsidiaries and the signatories thereunder.

                                    ARTICLE 3
                      REPRESENTATIONS OF REPLIGEN AND NEWCO

        Repligen and Newco each hereby represent and warrant to and agree with
Glycan as follows:

        SECTION 3.1. Organization, Standing and Power of Repligen. Repligen and
Newco are corporations duly organized, validly existing, and Newco is in good
standing under the laws of the State of Delaware, and Repligen and Newco have
all requisite corporate power and authority to own, operate and lease their
properties, to carry on their businesses as now being conducted and are duly
qualified to do business and are in good standing in every jurisdiction
(including foreign countries) in which the properties owned or leased by them
make such qualification necessary, except where failure to so qualify is not
reasonably likely to have a material adverse effect on the business operations
or prospects of Repligen or Newco, such jurisdictions being set forth in
Schedule 3.1 hereto. Repligen and Newco have the statutory power to enter into
this Agreement and perform their obligations hereunder.

        SECTION 3.2. Due Execution. The execution, delivery and performance of
this Agreement by Repligen and Newco and the consummation by each of them of the
transactions contemplated hereby have been approved by all necessary corporate
action on the part of each of them and this Agreement and any other agreement or
instrument delivered in connection herewith constitutes the valid and binding
obligation of Repligen and Newco enforceable in accordance with its terms,
except as such enforceability may be limited by applicable bankruptcy,
insolvency, moratorium, reorganization or similar laws from time to time in
effect which affect creditors' rights generally and by legal and equitable
limitations on the availability of specific performance and other equitable
remedies against Repligen or Newco under or by virtue of this Agreement or such
other agreement or instrument.

        SECTION 3.3. No Consents, No Defaults. The execution, delivery and
performance of this Agreement by Repligen and Newco and the consummation by each
of them of the transactions contemplated hereby (i) do not require the consent,
waiver, approval, license or authorization of any person or entity or public
authority which has not been obtained, (ii) do not violate, with or without the
giving of notice or the passage of time or both, in any material respect any
provision of law applicable to Repligen, Newco, or either of them, and (iii) do
not conflict with or result in a breach or termination of any provision of, or
constitute a default in any material respect under, or result in the creation of
any lien, charge or encumbrance upon any of the property or assets of Repligen
or Newco pursuant to their respective certificates of incorporation or by-laws
of any mortgage, deed or trust, indenture or other agreement or instrument, or
any order, judgment, decree, statute, regulation or any other restriction of any
kind or character, to which Repligen or Newco is a party or by which Repligen or
any of its Repligen Subsidiaries (as hereinafter defined) may be bound, except
where such conflict, breach or termination is not reasonably likely to have a
material adverse effect on Repligen and Newco taken as a whole.

        SECTION 3.4. Subsidiaries. Repligen owns, directly or indirectly, all or
a majority of the outstanding shares of the corporations set forth in Schedule
3.4 hereto, including Newco. The authorized capital stock, the number of shares
duly issued and outstanding and the number thereof held directly or indirectly
by Repligen, the jurisdiction of incorporation and the jurisdiction (including
foreign countries) of qualification of each are as set forth in Schedule 3.4.
The shares of each such corporation owned, directly or indirectly, by Repligen
are fully paid and nonassessable, and Repligen owns, directly or indirectly, all
such shares free and clear of all mortgages, liens or other encumbrances
whatsoever, and none of such shares is subject to any covenant or restriction
preventing or limiting the right to transfer such shares. Each of such
corporations is a corporation duly organized, validly existing and in good
standing under the laws of the jurisdiction of its incorporation, has the
corporate power to own and lease its properties and to carry on its business as
now being conducted and is duly qualified to do business and is in good standing
in every jurisdiction (including foreign countries) in which the character of
the properties owned or leased by its makes such qualification necessary, except
where failure to qualify is not reasonable likely to have a material adverse
effect on the business operations or prospects of Repligen and the Repligen
Subsidiaries. Such corporations, together with Newco, are hereinafter also
collectively referred to as the "Repligen Subsidiaries". Repligen does not
control, directly or indirectly, or own any capital stock or other proprietary
interest in any corporation, partnership, joint venture, or other entity other
than the Repligen Subsidiaries as described in Schedule 3.4. Repligen has
delivered to Glycan true and complete copies of the certificate of incorporation
and by-laws of Repligen and each of its Repligen Subsidiaries as in effect on
the date hereof, certified by the Secretary of the respective corporations in
the case of by-laws and by the Secretary of State of the appropriate
jurisdiction in the case of certificates of incorporation.

        SECTION 3.5. Capitalization. The authorized capital stock of Repligen
consists of 25,000,000 shares of common stock and 5,000,000 shares of preferred
stock. As of February 2, 1996, there were outstanding 15,358,938 shares of
common stock; no shares of preferred stock; stock options to purchase an
aggregate of 759,401 shares of common stock of which options to purchase an
aggregate of 345,070 shares were exercisable; and warrants to purchase 2,160,400
shares of common stock. All outstanding shares of capital stock of Repligen have
been duly authorized and validly issued and are fully paid and nonassessable,
and none of them is held in the treasury of Repligen. Except as set forth in
this Section, there are outstanding (a) no other shares of capital stock or
other voting securities of Repligen, (b) no securities of Repligen convertible
into or exchangeable for shares of capital stock or voting securities of
Repligen, and (c) no other options or other rights to acquire from Repligen, and
no obligation of Repligen to issue, any capital stock, voting securities or
securities convertible into or exchangeable for capital stock or voting
securities of Repligen (the items in clauses (a), (b) and (c) being referred to
collectively as the "Repligen Securities"). There are no outstanding obligations
of Repligen to repurchase, redeem or otherwise acquire any Repligen Securities.
The authorized capital stock of Newco consists of 100 shares of common stock,
all of which are validly issued and outstanding, fully paid and nonassessable
and owned by Repligen.

        SECTION 3.6. Officers; Directors; Shareholders. Attached hereto as
Schedule 3.6 is a list of (i) the officers and directors of Repligen and each of
the Repligen Subsidiaries and (ii) all persons owning of record or, to the
knowledge of Repligen, beneficially more than 10% of Repligen's common stock.

        SECTION 3.7.  Financial Statements.

               (i) Repligen has furnished Glycan with the unaudited consolidated
balance sheet of Repligen and its consolidated subsidiaries as of January 31,
1996 (the "Repligen Interim Balance Sheet"), and the related unaudited
consolidated statements of loss and deficit and changes in financial position
for the ten months then ended. Such financial statements (a) are in accordance
with the books and records of Repligen and the Repligen Subsidiaries, (b) are
correct and complete, (c) fairly present the financial position and the results
of operations of Repligen and the Repligen Subsidiaries as of the respective
dates indicated (subject, in the case of the unaudited statements, to normal,
recurring adjustments, none of which will be material), and (d) have been
prepared in accordance with generally accepted accounting principles applied on
a consistent basis.

        (ii) Except as and to the extent set forth on the Repligen Balance Sheet
or in the SEC Reports (as defined in Section 3.16), Repligen and the Repligen
Subsidiaries do not have any liability or obligation of any nature (whether
accrued, absolute, contingent or otherwise), except for liabilities and
obligations incurred since January 31, 1996 which (a) were incurred in the
ordinary course of business and (b) would not, individually or in the aggregate,
have a material adverse effect on the business of Repligen and the Repligen
Subsidiaries, taken as a whole.

        SECTION 3.8. Taxes. Repligen and the Repligen Subsidiaries have filed
all tax returns which are required to be filed by them; and all such returns are
true and correct. Repligen and the Repligen Subsidiaries have paid or provided
adequate reserves for all taxes which have become due pursuant to such returns
or pursuant to any assessments received by them or which any of them is
obligated to withhold from amounts owing to any employee, creditor or other
third party. The Federal income tax returns of Repligen and the Repligen
Subsidiaries have never been audited by the Internal Revenue Service. Neither
Repligen nor any of the Repligen Subsidiaries has waived any statute of
limitations in respect of taxes, or has agreed to any extension of time with
respect to a tax assessment or deficiency.

        SECTION 3.9. Real Property. Neither Repligen nor any of the Repligen
Subsidiaries owns any real estate.

        SECTION 3.10. Title. Except as shown in the SEC Reports or in the
Repligen Balance Sheet or in the notes thereto and except for liens,
restrictions or encumbrances which do not interfere with or adversely affect the
use of properties and assets owned by Repligen and the Repligen Subsidiaries,
Repligen and each of the Repligen Subsidiaries own outright all their respective
properties and assets (other than leased properties or assets), free and clear
of all mortgages, liens, restrictions, encumbrances, options, rights of first
refusal or other claims whatsoever.

        SECTION 3.11. Intangible Property. Except as set forth on Schedule 3.11,
Repligen owns, directly or indirectly, all patents, patent licenses, trade
names, trademarks, service marks, brand marks, brand names, copyrights, or
registrations or licenses thereof or applications therefor or interests therein,
or know-how or other proprietary or trade rights, the use of which is necessary
for the business of Repligen and the Repligen Subsidiaries as now conducted. As
of the date hereof no suits are pending or to the knowledge of Repligen
threatened against Repligen or the Repligen Subsidiaries before any court of the
United States or any state thereof in which it is claimed that Repligen is in
violation or infringement of any United States patent, patent license, trade
name, trademark, service mark, brand mark, brand name, copyright, know-how or
other proprietary or trade rights of any third party, the outcome of which would
have a materially adverse effect on the consolidated financial condition or
results of operations of Repligen and the Repligen Subsidiaries.

        SECTION 3.12.  Material Contracts.

               (i) Except as set forth on Schedule 3.12, neither Repligen nor
any of the Repligen Subsidiaries is party to or bound by any (a) material lease
or license with respect to any property, real or personal, tangible or
intangible, whether as landlord, tenant, licensor or licensee; (b) agreement,
contract, or indenture relating to the borrowing of money by Repligen or any of
the Repligen Subsidiaries; (c) management agreement, employment, consulting,
severance, "parachute" or other similar contract or arrangement; (d) agreement
with any present or former officer, director or shareholder of Repligen or any
of the Repligen Subsidiaries; or (e) other contract, agreement or other
commitment which involve a payment by Repligen or any of the Repligen
Subsidiaries of more than $25,000 in one year.

               (ii) Except as set forth on Schedule 3.12 or as disclosed in the
SEC Reports, neither Repligen nor any of the Repligen Subsidiaries is in
material breach or material default under any agreement or commitment required
to be disclosed in Schedule 3.12 (a "Material Agreement"); and there has not
occurred any event which, after the giving of notice, the lapse of time or
otherwise, would constitute any such default under, or result in any such breach
of, any such Material Agreement.

        SECTION 3.13. Litigation. Except as set forth in Schedule 3.13 attached
hereto, as of the date hereof there are no actions, suits or proceedings pending
or, to the best of the knowledge of Repligen, threatened against Repligen or the
Repligen Subsidiaries at law or in equity or before or by any federal, state,
municipal or other governmental department, commission, board, bureau, agency or
instrumentality, the outcome of which would have a materially adverse effect on
the consolidated financial condition or results of operation of Repligen and the
Repligen Subsidiaries or have an adverse effect on the Merger.

        SECTION 3.14. Certain Activities. Except as set forth in Schedule 3.14
attached hereto or in the SEC Reports, since December 31, 1995, neither Repligen
nor any of the Repligen Subsidiaries has done or agreed to do any of the
following: (a) issue any stock (other than pursuant to the exercise of existing
stock options or warrants), notes, or other Repligen Securities or debt
instruments, or grant any options, warrants or other rights calling for the
issue thereof; (b) incur, or become subject to, any indebtedness, obligation, or
liability (absolute or contingent) except current liabilities and obligations
incurred in the ordinary course of business; (c) pay any obligation or liability
(absolute or contingent) other than current liabilities reflected in or shown on
the Repligen Interim Balance Sheet, and current liabilities incurred since
January 31, 1996 in the ordinary course of business; (d) declare or make any
payment of dividends or distributions of any assets of any kind whatsoever to
stockholders or purchase or redeem any of its stock; (e) purchase or lease any
real property; (f) mortgage, pledge or subject to lien, charge or any other
encumbrance of any of its assets, tangible or intangible; or (g) enter into any
transaction other than in the ordinary course of business.

        SECTION 3.15. Compliance with Laws. Repligen and the Repligen
Subsidiaries have complied in all material respects with all laws, ordinances,
regulations and orders, which have application to its business, the violation of
which is reasonably likely to have a material adverse effect on its financial
condition or results of operation, and possess all governmental licenses and
permits material to and necessary in the conduct of its business, the absence of
which is reasonably likely to have a material adverse effect on its financial
condition or results of operation. All such licenses and permits are in full
force and effect, no violations are or have been recorded in respect to any such
licenses or permits, and no proceeding is pending or threatened to revoke or
limit any such licenses or permits. Each such license or permit shall remain
valid and in full force and effect upon consummation of the Merger without any
restriction or required consent or approval of any third party which will not
have been obtained on or prior to the Effective Time.

        SECTION 3.16. SEC Filings. Repligen has timely filed all reports
required to be filed with the Securities and Exchange Commission pursuant to the
Securities and Exchange Act of 1934, as amended (the "Exchange Act"). Repligen
has delivered to Glycan (i) its annual reports on Form 10-K for its fiscal years
ended March 31, 1993, 1994 and 1995, (ii) its quarterly reports on Form 10-Q for
its fiscal quarters September 30, 1995 and December 31, 1995, (iii) its proxy or
information statements relating to its annual meeting of stockholders held on
September 14, 1995, and (iv) all of its other reports, statements, schedules and
registration statements filed with the SEC since September 14, 1995
(collectively the "SEC Reports"). As of its filing date, no SEC Report contained
any untrue statement of material fact or omitted to state any material fact
necessary in order to make the statements made therein, in the light of the
circumstances under which they were made, not misleading in any material
respect.

                                    ARTICLE 4
                        ADDITIONAL AGREEMENTS OF REPLIGEN

        SECTION 4.1. Certificates for Repligen Common Stock. (i) The shares of
Repligen's common stock deliverable to holders of shares of common stock of
Glycan pursuant to or as a result of the Merger will not be registered under the
Securities Act of 1933, as amended (the "Act"), and are expected to be issued
under exemptions from registration provided by Section 4(2) and Section 3(b) and
Regulation D thereunder. Accordingly, the certificates representing such shares
shall be stamped or imprinted with a legend in substantially the following form:

               "The shares represented by this certificate have not been
               registered under the Securities Act of 1933, as amended (the
               "Act"), and may not be transferred in the absence of an effective
               registration statement under the Act covering the shares or of an
               opinion of counsel to the Corporation that such transfer will not
               require registration of such shares under the Act."

        SECTION 4.2. Glycan Warrants. At the Effective Time or as soon as
reasonably practicable thereafter, Repligen shall deliver to each holder of a
valid, outstanding warrant to purchase shares of Glycan's Common Stock a valid
and enforceable substitute warrant to purchase such number of shares of
Repligen's Common Stock as the holder of such warrant would have received had he
exercised such Glycan warrant in full immediately prior to the Effective Time of
the Merger. Each substitute warrant shall contain the same basic terms and
conditions as the Glycan warrant for which it is substituted; the purchase price
per share of Repligen Common Stock under such substitute warrant shall be
determined by dividing the aggregate purchase price of all unpurchased shares of
Glycan Common Stock under such Glycan warrant by the number of whole shares of
Repligen Common Stock covered by the substitute warrant and, if necessary, shall
be rounded to the next highest cent; no fractional shares of Repligen Common
Stock shall be covered by such substitute warrant; and any such fractions shall
be eliminated in calculating the number of shares of Repligen Common Stock
covered by each substitute warrant. In order to effectuate the foregoing,
Repligen shall reserve out of its authorized but unissued shares of Common Stock
sufficient shares to provide for the exercise of the substituted warrants. None
of the substituted warrants or the shares of Repligen Common Stock issuable upon
the exercise thereof will have been registered under the Act and therefore may
not be transferred or sold unless registered under the Act or in the opinion of
counsel to Repligen an exemption from registration is available.

        SECTION 4.3. Glycan Options. At the Effective Time, all rights with
respect to Glycan Common Stock pursuant to stock options granted by Glycan under
the Glycan Stock Option Plans, including options granted under such Plans
pursuant to employment or acquisition agreements ("Glycan Options"), which are
outstanding at the Effective Time, whether or not then exercisable, shall be
converted into and become rights with respect to Repligen Common Stock and
Repligen shall assume each of such Glycan Options, in accordance with the terms
of the Stock Option Plan under which it was issued and the stock option or stock
appreciation rights agreement by which it is evidenced. From and after the
Effective Time, (i) each such Glycan Option may be exercised solely for shares
of Repligen Common Stock notwithstanding any contrary provisions of the Glycan
Stock Option Plans, (ii) the number of shares of Repligen Common Stock subject
to such Glycan Option shall be equal to the number of shares of Glycan Common
Stock subject to such Glycan Option immediately prior to the Effective Time
multiplied by the Exchange Ratio (with the product rounded down to the next
whole share), (iii) the per share exercise price shall be adjusted by dividing
the per share exercise price under each such Glycan Option by the Exchange
Ratio, and (iv) Repligen and its Compensation Committee shall be substituted for
Glycan and the Glycan Board of Directors administering the Glycan Stock Option
Plans. It is intended that the foregoing assumption shall be undertaken in a
manner that will not constitute a "modification" as defined in Section 424(b) of
the Internal Revenue Code as to any stock option which is an "incentive stock
option." The Repligen Board of Directors shall take such action as may be
required under the Glycan Stock Option Plans to effectuate the foregoing.

        SECTION 4.4. Agreements. Repligen shall simultaneously herewith enter
into employment agreements with each of Messrs. Walter Herlihy, Jim Rusche and
Dan Witt; and a Registration Rights Agreement, each in the respective form
annexed hereto as Exhibits B, C, D and E, respectively.

                                    ARTICLE 5
                         REPRESENTATION OF STOCKHOLDERS

        SECTION 5.1. Securities Laws Matters. The Stockholders acknowledge that
none of the shares of Common Stock of Repligen to be issued to them pursuant to
or as a result of the Merger (collectively, the "Merger Securities") have been
registered under the Act, but are expected to be issued under exemptions from
registration provided by Sections 4(2) and 3(b) and Regulation D thereunder. The
Stockholders understand and acknowledge that the Merger Securities must be held
by each of them indefinitely unless registered under the Act or unless, in the
opinion of counsel to Repligen, an exemption from such registration is
available. The Stockholders understand that only Repligen may file a
registration statement with respect to the Merger Securities and that, except as
provided in Section 4.1(b), Repligen is under no obligation to do so with
respect to the Merger Securities. The Stockholders acknowledge that they have
been advised that an exemption from the registration with respect to the Merger
Securities may not be available or may not permit the Stockholders to transfer
the Merger Securities in the amounts or at the times desired by the
Stockholders. In addition, the Stockholders understand and acknowledge that Rule
144 under the Act, which provides for certain limited, routine sales of
unregistered securities of public companies through securities brokers, is not
presently available with respect to the Merger Securities, may never be
available, and in any event requires that the Merger Securities be held for a
minimum of two years before they may be resold under Rule 144. Each Stockholder
hereby represents and warrants to Repligen and Newco that: (a) he or she is
acquiring and will acquire the Merger Securities for his or her own account for
investment only and not with a view to, or for sale in connection with, a
distribution within the meaning of the Act; (b) he or she has no present
intention of selling or otherwise disposing of any portion of the Merger
Securities; (c) he or she has access to all information regarding Repligen and
its present and prospective business, assets, liabilities and financial
condition and the backgrounds of the executive officers of Repligen as such
Stockholder considers important in making the decision to acquire the Merger
Securities; (d) he or she recognizes that an investment in the Merger Securities
involves special and substantial risks because, among other things, Repligen has
incurred significant operating losses since inception, has undergone major
restructurings of its operations, several of Repligen's leading clinical
candidates, including its rPF4 and CD11b programs, have been terminated or
suspended and the economic viability of Repligen's remaining clinical products
is uncertain at this time, Repligen has limited financial resources and limited
access to new funding sources, and Repligen is presently in default and seeking
to restructure several of its long-term commitments, and such other matters as
are disclosed in Repligen's Form 10-Q for the quarter ended December 31, 1995
annexed hereto as Exhibit F; (e) he or she is financially capable of bearing a
total loss of his or her investment in the Merger Securities and is able to
evaluate the merits and risks of his or her investment in the Merger Securities
and to protect his or her own interests in this transaction; (f) at no time was
he or she presented with, or solicited by any publicly issued or circulated
newspaper, magazine, mail, radio or television or any other form or general
advertising or solicitation in connection with the acquisition of the Merger
Securities; and (g) to the best of his or her knowledge, no commission, discount
or other remuneration is due or payable in connection with this transaction.

                                    ARTICLE 6
                   SURVIVAL OF REPRESENTATIONS AND WARRANTIES.

        SECTION 6.1. Survival. The representations and warranties of the parties
hereto shall not survive the Effective Time, except for the representation and
warranties of the Stockholders contained in Article 5.

                                    ARTICLE 7
                                  MISCELLANEOUS

        SECTION 7.1. Payment of Expenses. Repligen and Glycan will each pay its
own expenses, and Repligen shall pay the expenses of Newco, incident to
preparing for entering into and performing this Agreement and to the
consummation of the transactions contemplated thereby.

        SECTION 7.2. Governing Law. This Agreement shall be governed by and
construed in accordance with the internal laws of the State of Delaware (without
giving effect to its conflict of laws principles) except to the extent that the
DGCL and the other laws of the State of Delaware shall govern the Merger.

        SECTION 7.3. Cooperation, etc. Each of the parties hereto shall
cooperate with the others in every way in carrying out the transactions
contemplated herein, and delivering instruments to perfect the conveyances,
assignments and transfers contemplated herein, and in delivering all documents
and instruments deemed reasonably necessary or useful by counsel for any party
hereto.

        SECTION 7.4. Assignability. This Agreement shall not be assignable by
either party and cannot be altered or otherwise amended except pursuant to an
instrument in writing signed by each of the parties hereto pursuant to authority
of their respective Boards of Directors, provided that any party hereto may
assign this Agreement at any time after the Effective Time to any entity in
connection with a merger of such party with or into such other entity or a sale
of all or substantially all of its assets.

        SECTION 7.5. Notices. Any notice or other communication required or
permitted hereunder shall be in writing and shall be delivered personally,
telegraphed, telexed, sent by facsimile transmission or sent by certified,
registered or express mail, postage prepaid. Any such notice shall be deemed
given when so delivered personally, telegraphed, telexed or sent by facsimile
transmission or, if mailed, three days after the date of deposit in the United
States mails, as follows:

               (i)    if to Newco or Repligen to:

                      Repligen Corporation
                      One Kendall Square
                      Building 700
                      Cambridge, MA  02139
                      (Attn:  President)
                      Facsimile:  617-225-6060

                      with a copy to:

                      Stanley M. Johnson, Esq.
                      Bryan Cave
                      245 Park Avenue
                      New York, New York 10167
                      Facsimile:  212-692-1900

               (ii)   if to Glycan to:

                      One Kendall Square
                      Building 700
                      Cambridge, MA  02139
                      (Attn:  Walter C. Herlihy Ph.D)
                      Facsimile:

                      with a copy to:

                      Lawrence S. Wittenberg, Esq.
                      Testa, Hurwitz & Thibeault
                      High Street Tower
                      125 High Street
                      Boston, MA  02110

        SECTION 7.6. Execution in Counterparts. This Agreement may be executed
in one or more counterparts, each of which shall be deemed an original but all
of which together shall constitute one and the same instrument.

        SECTION 7.7. Entire Agreement. This Agreement (including the Schedules
and Exhibits) and the agreements executed in connection with the consummation of
the transactions contemplated herein contain the entire agreement among the
parties with respect to the Merger and related transactions, and supersede all
prior agreements, written or oral, with respect thereto.

        SECTION 7.8. Binding Effect; No Third Party Beneficiaries. This
Agreement shall be binding upon and inure to the benefit of the parties and
their respective successors, heirs, and legal representatives upon the execution
thereof by Repligen, Newco and Glycan. Nothing contained herein is intended or
shall be construed as creating third party beneficiaries to this Agreement.

        SECTION 7.9. Variations in Pronouns. All pronouns and any variations
thereof refer to the masculine, feminine or neuter, singular or plural, as the
context may require.

        SECTION 7.10. Exhibits and Schedules. The Exhibits and Schedules are a
part of this Agreement as if fully set forth herein. All references herein to
Sections, subsections, clauses, Exhibits and Schedules shall be deemed
references to such parts of this Agreement, unless the context shall otherwise
require.

        SECTION 7.11. Headings. The headings in this Agreement are for reference
only, and shall not affect the interpretation of this Agreement.



                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK.]






        IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed and delivered as of the day and year first above written.

ATTEST:                                     REPLIGEN ACQUISITION CORP.


___________________________            By:    _________________________________
                                              Name:
                                              Title:

ATTEST:                                     GLYCAN PHARMACEUTICALS, INC.


___________________________            By:    _________________________________
                                              Name:
                                              Title:

ATTEST:                                     REPLIGEN CORPORATION


___________________________            By:    _________________________________
                                              Name:
                                              Title:

                                            Executed by the undersigned solely
                                            to confirm their agreement with the
                                            provisions of Article 5 hereof
                                            applicable to them.

                                            STOCKHOLDERS


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


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


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





                                    EXHIBIT A

                          GLYCAN OFFICERS AND DIRECTORS


             OFFICERS AND DIRECTORS OF GLYCAN PHARMACEUTICALS, INC.

Directors

Paul Schimmel, Ph.D.
Walter C. Herlihy, Jr.
James Robert Rusche
Daniel Parker Witt

Officers

Walter C. Herlihy, Jr., President and Chief Executive Officers
James Robert Rusche, Vice President, Research and Development
Daniel P. Witt, Vice President, Business Development