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                                                                   EXHIBIT 10.38

                           LOAN AND SECURITY AGREEMENT

     THIS LOAN AND SECURITY AGREEMENT (this "Agreement") dated as of
December 28, 2004, between SILICON VALLEY BANK, a California chartered bank,
with its principal place of business at 3003 Tasman Drive, Santa Clara,
California 95054 and with a loan production office located at One Newton
Executive Park, Suite 200, 2221 Washington Street, Newton, Massachusetts 02462,
doing business under the name "Silicon Valley East" ("Bank") and MOMENTA
PHARMACEUTICALS, INC., a Delaware corporation ("Borrower"), provides the terms
on which Bank shall lend to Borrower and Borrower shall repay Bank. The parties
agree as follows:

     1      ACCOUNTING AND OTHER TERMS

     Accounting terms not defined in this Agreement shall be construed following
GAAP. Calculations and determinations must be made following GAAP. The term
"financial statements" includes the notes and schedules. The terms "including"
and "includes" always mean "including (or includes) without limitation," in this
or any Loan Document. Capitalized terms in this Agreement shall have the
meanings set forth in Article 13. All other terms contained in this Agreement,
unless otherwise indicated, shall have the meaning provided by the Code, to the
extent such terms are defined therein.

     2      LOAN AND TERMS OF PAYMENT

     2.1    PROMISE TO PAY. Borrower hereby unconditionally promises to pay Bank
the unpaid principal amount of all Credit Extensions and interest on the unpaid
principal amount of the Credit Extensions as and when due in accordance with
this Agreement.

     2.1.1  EQUIPMENT FACILITY.

           (a)    EQUIPMENT ADVANCES. Subject to the terms and conditions of
this Agreement, Bank agrees to lend to Borrower, from the Closing Date through
September 30, 2005 (the "Draw Period"), equipment advances (each an "Equipment
Advance" and collectively the "Equipment Advances") in an aggregate amount not
to exceed the Equipment Line. When repaid, the Equipment Advances may not be
re-borrowed. The proceeds of the Equipment Advances shall be used solely to
reimburse Borrower for the purchase of Eligible Equipment purchased within
ninety (90) days (determined based upon the applicable invoice date of such
Eligible Equipment) of the Equipment Advance and to purchase new Eligible
Equipment. Notwithstanding the foregoing, the initial Equipment Advance
hereunder may be used to reimburse Borrower for Eligible Equipment purchased on
or after April 1, 2004. Bank's obligation to lend hereunder shall terminate on
the earlier of (i) the occurrence and continuance of an Event of Default, or
(ii) the last day of the Draw Period. For purposes of this Section, the minimum
amount of each Equipment Advance shall be One Hundred Thousand Dollars
($100,000.00). Each Equipment Advance may not exceed one hundred percent (100%)
of the Original Stated Cost of the Financed Equipment.

           (b)    PRINCIPAL AND INTEREST PAYMENTS ON PAYMENT DATES. For each
Equipment Advance, Borrower shall make consecutive equal monthly payments of
principal and interest, calculated by the Bank based upon: (1) the amount of the
Equipment Advance, (2) the Basic Rate, and (3) an amortization schedule equal to
the Repayment Period (individually, the "Scheduled Payment", and collectively,
"Scheduled Payments"), commencing on the first Payment Date of the month
following the month in which the Funding Date occurs (or commencing on the
Funding Date if the Funding Date is the first Business Day of the month) with
respect to such Equipment Advance and continuing on each Payment Date
thereafter. All unpaid principal and accrued interest is due and payable in full
on the last Payment Date with respect to such Equipment Advance. Payments
received after 3:00 p.m. Eastern time are considered received at the opening of
business on the next Business Day. When a payment is due on a day that is not a
Business Day, the payment is due the next Business Day and additional fees or
interest, as applicable, shall continue to accrue.

           (c)    INTEREST RATE. Borrower shall pay interest on each Payment
Date on the unpaid principal amount of each Equipment Advance until the
Equipment Advance has been paid in full, at the per annum rate of

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interest equal to the Basic Rate fixed on the Funding Date for each Equipment
Advance. Interest is computed on the basis of a 360 day year for the actual
number of days elapsed. Any amounts outstanding during the continuance of an
Event of Default shall bear interest at a per annum rate equal to the Basic Rate
plus three percent (3.0%)(the "Default Rate").

           (d)    BORROWING PROCEDURE. To obtain an Equipment Advance, Borrower
shall deliver to Bank a completed supplement in substantially the form attached
as EXHIBIT B ("Loan Supplement"), signed by a Responsible Officer, or his or her
designee, copies of invoices for the Financed Equipment, described on Annex A to
the applicable Loan Supplement, together with a UCC Financing Statement
authorization covering the Financed Equipment described on Annex A to the
applicable Loan Supplement and such additional information regarding the
Financed Equipment as Bank may reasonably request at least five (5) Business
Days before the proposed funding date (the "Funding Date"). On each Funding
Date, Bank shall specify in the Loan Supplement for each Equipment Advance, the
Basic Rate, and the Payment Dates. If Borrower satisfies the conditions of each
Equipment Advance, Bank shall disburse such Equipment Advance by transfer to
Borrower's deposit account at Bank.

           (e)    DEBIT OF ACCOUNTS. Bank may debit Borrower's operating
accounts, including Account Number __________, for principal and interest
payments when due. Bank shall promptly notify Borrower after it debits
Borrower's accounts. These debits shall not constitute a set-off.

     2.1.2  UNDISBURSED  CREDIT  EXTENSIONS.  The Bank's  obligation to lend the
undisbursed portion of the Equipment Line shall terminate if, in Bank's sole
discretion, there has been a Material Adverse Change.

     2.2    FEES. Borrower shall pay to Bank:

           (a)    BANK EXPENSES. All Bank Expenses (including reasonable
attorneys' fees and expenses incurred through and after the Closing Date), when
due.

     2.3    ADDITIONAL COSTS. If any new law or regulation increases Bank's
costs or reduces its income for any Equipment Advance, Borrower shall pay the
increase in cost or reduction in income or additional expense; provided,
however, that Borrower shall not be liable for any amount attributable to any
period before 180 days prior to the date Bank notifies Borrower of such
increased costs. Bank agrees that it shall allocate any increased costs among
its customers similarly affected in good faith and in a manner consistent with
Bank's customary practice.

     3      CONDITIONS OF LOANS

     3.1    CONDITIONS PRECEDENT TO INITIAL CREDIT EXTENSION. The Bank's
obligation to make the initial Credit Extension is subject to the condition
precedent that Bank shall have received, in form and substance satisfactory to
Bank, the following:

           (a)    this Agreement;

           (b)    a certificate of the Secretary of Borrower with respect to
articles, bylaws, incumbency and resolutions authorizing the execution and
delivery of this Agreement;

           (c)    perfection certificate by Borrower;

           (d)    a legal opinion of Borrower's counsel (authority and
enforceability), in form and substance acceptable to Bank;

           (e)    insurance certificate;

           (f)    payment of the fees and Bank Expenses then due specified in
Section 2.2 hereof;

           (g)    Certificate of Foreign Qualification (Massachusetts);

           (h)    Certificate of Good Standing/Legal Existence (Delaware); and

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           (i)    such other documents, and completion of such other matters, as
Bank may reasonably deem necessary or appropriate.

     3.2    CONDITIONS PRECEDENT TO ALL CREDIT EXTENSIONS. Bank's obligation to
make each Credit Extension, including the initial Credit Extension, is subject
to the following:

           (a)    timely receipt of a completed Loan Supplement and UCC
financing statement covering the Financed Equipment described on ANNEX A to the
Loan Supplement; and

           (b)    the representations and warranties in Section 5 must be true
in all material respects on the date of the Loan Supplement and on the effective
date of each Credit Extension (except to the extent such representations and
warranties relate to a specific date) and no Event of Default shall have
occurred and be continuing as of such effective date, or result from the Credit
Extension. Each Credit Extension (except to the extent such representations and
warranties relate to a specific date) is Borrower's representation and warranty
on that date that the representations and warranties in Section 5 remain true in
all material respects; and

           (c)    the Bank shall have the opportunity to confirm that upon
filing the UCC-1 financing statement covering the Equipment described on the
Loan Supplement, that the Bank shall have a first perfected security interest in
such Equipment.

     4      CREATION OF SECURITY INTEREST

     4.1    GRANT OF SECURITY INTEREST. Borrower hereby grants Bank, to secure
the payment and performance in full of all of the Obligations and the
performance of each of Borrower's duties under the Loan Documents, a continuing
security interest in, and pledges to the Bank, the Collateral, wherever located,
whether now owned or hereafter acquired or arising, and all proceeds and
products thereof. Borrower warrants and represents that the security interest
granted herein shall be a first priority security interest in the Collateral.

If the Agreement is terminated, Bank's lien and security interest in the
Collateral shall continue until Borrower fully satisfies its Obligations.

     4.2    AUTHORIZATION TO FILE FINANCING STATEMENTS. Borrower hereby
authorizes Bank to file financing statements, without notice to Borrower, with
all appropriate jurisdictions in order to perfect or protect Bank's interest or
rights hereunder, including a notice that any disposition of the Collateral,
except in accordance with this Agreement, by either the Borrower or any other
Person, shall be deemed to violate the rights of the Bank under the Code.

     5      REPRESENTATIONS AND WARRANTIES

     Borrower represents and warrants as follows:

     5.1    DUE ORGANIZATION AND AUTHORIZATION. Borrower and each Subsidiary is
duly existing and in good standing in its state of formation and qualified and
licensed to do business in, and in good standing in, any state in which the
conduct of its business or its ownership of property requires that it be
qualified except where the failure to do so could not reasonably be expected to
cause a Material Adverse Change. In connection with this Agreement, the Borrower
delivered to the Bank a certificate signed by the Borrower and entitled
"Perfection Certificate". The Borrower represents and warrants to the Bank that:
(a) the Borrower's exact legal name is that indicated on the Perfection
Certificate and on the signature page hereof; and (b) the Borrower is an
organization of the type, and is organized in the jurisdiction, set forth in the
Perfection Certificate; and (c) the Perfection Certificate accurately sets forth
the Borrower's organizational identification number or accurately states that
the Borrower has none; and (d) the Perfection Certificate accurately sets forth
the Borrower's place of business, or, if more than one, its chief executive
office as well as the Borrower's mailing address if different, and (e) all other
information set forth on the Perfection Certificate pertaining to the Borrower
is accurate and complete in all material respects. If the Borrower does not now
have an organizational identification number, but later obtains one, Borrower
shall forthwith notify the Bank of such organizational identification number.

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     The execution, delivery and performance of the Loan Documents have been
duly authorized, and do not conflict with Borrower's organizational documents,
nor constitute an event of default under any material agreement by which
Borrower is bound. Borrower is not in default under any agreement to which or by
which it is bound in which the default could reasonably be expected to cause a
Material Adverse Change.

     5.2    COLLATERAL. Borrower owns the Collateral, free of Liens except for
Permitted Liens. The Collateral is not in the possession of any third party
bailee (such as a warehouse). Except as hereafter disclosed to the Bank in
writing by Borrower, none of the components of the Collateral shall be
maintained at locations other than as provided in the Perfection Certificate. In
the event that Borrower, after the date hereof, intends to store or otherwise
deliver any portion of the Collateral to a bailee, then Borrower will first
receive the written consent of Bank and such bailee must acknowledge in writing
that the bailee is holding such Collateral for the benefit of Bank.

     5.3    LITIGATION. Except as shown in the Perfection Certificate, there are
no actions or proceedings pending or, to the knowledge of Borrower's Responsible
Officers, threatened in writing by or against Borrower or any Subsidiary in
which an adverse decision could reasonably be expected to cause a Material
Adverse Change.

     5.4    NO MATERIAL DEVIATION IN FINANCIAL STATEMENTS. All consolidated
financial statements for Borrower and any Subsidiary delivered to Bank fairly
present in all material respects Borrower's consolidated financial condition and
Borrower's consolidated results of operations for the period for which the same
have been furnished. There has not been any material deterioration in Borrower's
consolidated financial condition since the date of the most recent financial
statements of Borrower delivered by Borrower to Bank.

     5.5    SOLVENCY. The Borrower is not left with unreasonably small capital
after the transactions in this Agreement; and Borrower is able to pay its debts
(including trade debts) as they mature.

     5.6    REGULATORY COMPLIANCE. Borrower is not an "investment company" or a
company "controlled" by an "investment company" under the Investment Company
Act. Borrower is not engaged as one of its important activities in extending
credit for margin stock (under Regulations T and U of the Federal Reserve Board
of Governors). Borrower has complied in all material respects with the Federal
Fair Labor Standards Act. Borrower has not violated any laws, ordinances or
rules, the violation of which could reasonably be expected to cause a Material
Adverse Change. Borrower and each Subsidiary has timely filed all required tax
returns or extensions thereof and paid, or made adequate provision to pay, all
material taxes, except those being contested in good faith with adequate
reserves under GAAP. Borrower and each Subsidiary has obtained all consents,
approvals and authorizations of, made all declarations or filings with, and
given all notices to, all government authorities that are necessary to continue
its business as currently conducted except where the failure to make such
declarations, notices or filings would not reasonably be expected to cause a
Material Adverse Change.

     5.7    INTENTIONALLY DELETED.

     5.8    FULL DISCLOSURE. No written representation, warranty or other
statement of Borrower in any certificate or written instruments given to Bank
taken together with all such written certificates and written instruments given
to Bank contains any untrue statement of a material fact or omits to state a
material fact necessary to make the statements contained in the certificates or
instruments not misleading (it being recognized by Bank that the projections and
forecasts provided by Borrower in good faith and based upon reasonable
assumptions are not viewed as facts and that actual results during the period or
periods covered by such projections and forecasts may differ from the projected
or forecasted results).

     6      AFFIRMATIVE COVENANTS

     Borrower shall do all of the following:

     6.1    GOVERNMENT COMPLIANCE. Borrower shall maintain its legal existence
and good standing in its jurisdiction of formation and maintain qualification in
each jurisdiction in which the failure to so qualify would reasonably be
expected to have a material adverse effect on Borrower's business or operations.
Borrower shall comply, and have each Subsidiary comply, with all laws,
ordinances and regulations to which it is subject, where noncompliance with
which would reasonably be expected to cause a Material Adverse Change.

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     6.2    FINANCIAL STATEMENTS, REPORTS, CERTIFICATES. Borrower shall deliver
to Bank: (i) within five (5) days of filing, copies of or electronic notice of
links to all statements, reports and notices made available to Borrower's
security holders or to any holders of Subordinated Debt and all reports on Form
10-K, and 10-Q filed with the Securities and Exchange Commission; (ii) a prompt
report of any legal actions pending or threatened in writing against Borrower or
any Subsidiary that could reasonably be expected to result in damages or costs
to Borrower or any Subsidiary of One Million Dollars ($1,000,000.00) or more;
and (iii) other financial information reasonably requested by Bank.

     6.3    INTENTIONALLY DELETED.

     6.4    TAXES. Borrower shall make timely payment of all material federal,
state, and local taxes or assessments (other than taxes and assessments which
Borrower is contesting in good faith, with adequate reserves maintained in
accordance with GAAP) and will deliver to Bank, on demand, appropriate
certificates attesting to such payments.

     6.5    INSURANCE. Borrower shall keep the Collateral insured for risks and
in amounts, and as Bank may reasonably request. Insurance policies shall be in a
form, with companies, and in amounts that are satisfactory to Bank. All property
policies with respect to the Collateral shall have a lender's loss payable
endorsement showing Bank as an additional loss payee and all liability policies
shall show the Bank as an additional insured and all policies shall provide that
the insurer must give Bank at least twenty (20) days notice before canceling its
policy. At Bank's request, Borrower shall deliver certified copies of policies
and evidence of all premium payments. Proceeds payable under any property policy
on account of the Collateral shall, at Bank's option, be payable to Bank on
account of the Obligations. Notwithstanding the foregoing, so long as no Event
of Default has occurred and is continuing, Borrower shall have the option of
applying the proceeds on account of the Collateral of any property policy up to
$500,000.00, in the aggregate, toward the replacement or repair of destroyed or
damaged property; provided that (i) any such replaced or repaired property (a)
shall be of equal or like value as the replaced or repaired Collateral and (b)
shall be deemed Collateral in which Bank has been granted a first priority
security interest and (ii) after the occurrence and during the continuation of
an Event of Default all proceeds payable on account of the Collateral under such
property policy shall, at the option of the Bank, be payable to Bank on account
of the Obligations. If Borrower fails to obtain insurance as required under
Section 6.5 or to pay any amount or furnish any required proof of payment to
third persons and the Bank, Bank may make all or part of such payment or obtain
such insurance policies required in this Section 6.5, and take any reasonable
action under the policies Bank deems prudent.

     6.6    ACCOUNTS. Borrower shall maintain its primary operating account with
Bank.

     6.7    FURTHER ASSURANCES. Borrower shall execute any further instruments
and take further action as Bank reasonably requests to perfect or continue
Bank's security interest in the Collateral or to effect the purposes of this
Agreement.

     6.8    LANDLORD'S WAIVER. The Borrower shall use its commercially
reasonable efforts to deliver the landlord's waiver for its office located at
675 West Kendall Street, Cambridge, Massachusetts, within thirty (30) days of
the Closing Date

     7      NEGATIVE COVENANTS

     Borrower shall not do any of the following without the Bank's prior written
consent which shall not be unreasonably withheld.

     7.1    DISPOSITIONS. Convey, sell, lease, transfer, assign or otherwise
dispose of (collectively a "Transfer"), all or any part the Collateral.

     7.2    CHANGES IN BUSINESS LOCATIONS. Borrower shall not, without prior
written notice to Bank: (i) relocate its chief executive office, or (ii) change
its jurisdiction of organization, or (iii) change its organizational structure
or type, or (iv) change its legal name, or (v) change any organizational number
(if any) assigned by its jurisdiction of organization.

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     7.3    INTENTIONALLY DELETED.

     7.4    INDEBTEDNESS. Create, incur, assume, or be liable for any
Indebtedness, other than Permitted Indebtedness.

     7.5    ENCUMBRANCE. Create, incur, or allow any Lien on any of Collateral,
except for Permitted Liens, or permit any Collateral not to be subject to the
first priority security interest granted herein. The Collateral may also be
subject to Permitted Liens.

     7.6    INTENTIONALLY DELETED.

     7.7    TRANSACTIONS WITH AFFILIATES. Directly or indirectly enter into or
permit to exist any material transaction with any Affiliate of Borrower, except
for transactions that are in the ordinary course of Borrower's business, upon
fair and reasonable terms that are no less favorable to Borrower than would be
obtained in an arm's length transaction with a non-affiliated Person.

     7.8    SUBORDINATED DEBT. Make or permit any payment on any Subordinated
Debt, except under the terms of the Subordinated Debt, or amend any material
provision in any document relating to the Subordinated Debt, without Bank's
prior written consent.

     7.9    COMPLIANCE. Become an "investment company" or a company controlled
by an "investment company", under the Investment Company Act of 1940 or
undertake as one of its important activities extending credit to purchase or
carry margin stock, or use the proceeds of any Credit Extension for that
purpose; fail to meet the minimum funding requirements of ERISA, permit a
Reportable Event or Prohibited Transaction, as defined in ERISA, to occur; fail
to comply with the Federal Fair Labor Standards Act or violate any other law or
regulation, if the violation could reasonably be expected to cause a Material
Adverse Change.

     8      EVENTS OF DEFAULT

     Any one of the following is an Event of Default:

     8.1    PAYMENT DEFAULT. Borrower fails to pay any of the Obligations within
three (3) Business Days after their due date. During such three (3) Business Day
period the failure to cure the default shall not constitute an Event of Default
(but no Credit Extension shall be made during such period);

     8.2    COVENANT DEFAULT. (i) Borrower fails or neglects to perform any
obligation in Section 6 or violates any covenant in Section 7; or (ii) Borrower
fails or neglects to perform, keep, or observe any other material term,
provision, condition, covenant or agreement contained in this Agreement, any
Loan Documents, or in any present or future agreement between Borrower and Bank
and as to any default under such other material term, provision, condition,
covenant or agreement that can be cured, has failed to cure the default within
ten (10) days after the occurrence thereof; provided, however, that if the
default cannot by its nature be cured within the ten (10) day period or cannot
after diligent attempts by Borrower be cured within such ten (10) day period,
and such default is likely to be cured within a reasonable time, then Borrower
shall have an additional period (which shall not in any case exceed thirty (30)
days) to attempt to cure such default, and within such reasonable time period
the failure to cure the default shall not be deemed an Event of Default (but no
Credit Extensions shall be made during such cure period). Grace periods provided
under this section shall not apply, among other things, to financial covenants
or any other covenants that are required to be satisfied, completed or tested by
a date certain;

     8.3    MATERIAL ADVERSE CHANGE. A Material Adverse Change occurs;

     8.4    ATTACHMENT. (i) Any material portion of Borrower's assets is
attached, seized, levied on, or comes into possession of a trustee or receiver
and the attachment, seizure or levy is not removed in ten (10) days; (ii) the
service of process upon the Borrower seeking to attach, by trustee or similar
process, any funds of the Borrower in excess of One Hundred Thousand Dollars
($100,000.00) on deposit with the Bank, or any entity under control of Bank
(including a subsidiary), provided however, if such service of process is
dismissed by Borrower within ten (10) days, then this default shall be deemed
cured; (iii) Borrower is enjoined, restrained, or prevented by court order

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from conducting a material part of its business; (iv) a judgment or other claim
becomes a Lien on a material portion of Borrower's assets; or (v) a notice of
lien, levy, or assessment is filed against any Collateral or a material portion
of Borrower's assets by any government agency and not paid within ten (10) days
after Borrower receives notice. These are not Events of Default if stayed or if
a bond is posted pending contest by Borrower (but no Credit Extensions shall be
made during the cure, stay or contest period);

     8.5    INSOLVENCY. (i) Borrower is unable to pay its debts (including trade
debts) as they become due or otherwise becomes insolvent; (ii) Borrower begins a
voluntary Insolvency Proceeding; or (iii) an Insolvency Proceeding is begun
against Borrower and not dismissed or stayed within forty-five (45) days (but no
Credit Extensions shall be made before any Insolvency Proceeding is dismissed);

     8.6    OTHER AGREEMENTS. If there is a default in any agreement to which
Borrower is a party with a third party or parties resulting in the acceleration
of the maturity of any Indebtedness for borrowed money in an amount in excess of
One Million Dollars ($1,000,000) or that could be reasonably expected to result
in a Material Adverse Change;

     8.7    JUDGMENTS. If a judgment or judgments for the payment of money in an
amount, individually or in the aggregate, of at least One Million Dollars
($1,000,000) shall be rendered against Borrower and shall remain unsatisfied and
unstayed for a period of thirty (30) days (provided that no Credit Extensions
will be made prior to the satisfaction or stay of such judgment);

     8.8    MISREPRESENTATIONS. If Borrower or any Person acting for Borrower
makes any material misrepresentation or material misstatement now or later in
any warranty or representation in this Agreement or in any writing delivered to
Bank or to induce Bank to enter this Agreement or any Loan Document;

     8.9    SUBORDINATED DEBT. A default or breach occurs under any agreement
between Borrower and any creditor of Borrower that signed a subordination
agreement with Bank, or any creditor that has signed a subordination agreement
with Bank breaches any terms of the subordination agreement; and

     8.10   SVB LOAN ARRANGEMENT. The occurrence of any Event of Default under
the SVB Loan Arrangement.

     9      BANK'S RIGHTS AND REMEDIES

     9.1    RIGHTS AND REMEDIES. When an Event of Default occurs and continues
Bank may, without notice or demand, do any or all of the following:

           (a)    Declare all Obligations immediately due and payable (but if an
Event of Default described in Section 8.5 occurs all Obligations are immediately
due and payable without any action by Bank);

           (b)    Stop advancing money or extending credit for Borrower's
benefit under this Agreement or under any other agreement between Borrower and
Bank;

           (c)    Make any payments and do any acts it considers necessary or
reasonable to protect its security interest in the Collateral. Borrower shall
assemble the Collateral if Bank requests and make it available as Bank
designates. Subject to the rights of third parties, to the extent such third
parties' rights are senior to the Bank, Bank may enter premises where the
Collateral is located, take and maintain possession of any part of the
Collateral, and pay, purchase, contest, or compromise any Lien which appears to
be prior or superior to its security interest and pay all expenses incurred.
Subject to the rights of third parties, to the extent such third parties' rights
are senior to the Bank, Borrower grants Bank a license to enter and occupy any
of its premises, without charge, to exercise any of Bank's rights or remedies;

           (d)    Apply to the Obligations any (i) balances and deposits of
Borrower it holds, or (ii) any amount held by Bank owing to or for the credit or
the account of Borrower; and

           (e)    Exercise all rights and remedies and dispose of the Collateral
according to the Code.

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     9.2    POWER OF ATTORNEY. Borrower hereby irrevocably appoints Bank as its
lawful attorney-in-fact, to be effective upon the occurrence and during the
continuance of an Event of Default and until the Obligations have been satisfied
in full and Bank is under no further obligation to make Credit Extensions
hereunder, to: (i) make, settle, and adjust all claims under Borrower's
insurance policies relating to the Collateral for commercially reasonable
amounts; and (ii) transfer the Collateral into the name of Bank or a third party
as the Code permits. Borrower hereby appoints Bank as its lawful
attorney-in-fact to sign Borrower's name on any documents necessary to perfect
or continue the perfection of any security interest regardless of whether an
Event of Default has occurred until all Obligations have been satisfied in full
and Bank is under no further obligation to make Credit Extensions hereunder.
Bank's foregoing appointment as Borrower's attorney in fact, and all of Bank's
rights and powers, coupled with an interest, are irrevocable until all
Obligations have been fully repaid and performed and Bank's obligation to
provide Credit Extensions terminates.

     9.3    INTENTIONALLY DELETED.

     9.4    BANK EXPENSES. Any amounts owing by Borrower and paid by Bank on
Borrower's behalf as provided herein shall constitute Bank Expenses and are due
and payable upon demand, and shall thereafter bear interest at the then
applicable rate and be secured by the Collateral. No payments by Bank shall be
deemed an agreement to make similar payments in the future or Bank's waiver of
any Event of Default.

     9.5    BANK'S LIABILITY FOR COLLATERAL. So long as the Bank complies with
reasonable banking practices regarding the safekeeping of collateral, (i) the
Bank shall not be liable or responsible, except as a result of its gross
negligence or willful misconduct, for: (a) the safekeeping of the Collateral;
(b) any loss or damage to the Collateral; (c) any diminution in the value of the
Collateral; or (d) any act or default of any carrier, warehouseman, bailee, or
other Person, and (ii) subject to the foregoing, Borrower bears all risk of
loss, damage or destruction of the Collateral.

     9.6    REMEDIES CUMULATIVE. Bank's rights and remedies under this
Agreement, the Loan Documents, and all other agreements are cumulative. Bank has
all rights and remedies provided under the Code, by law, or in equity. Bank's
exercise of one right or remedy is not an election, and Bank's waiver of any
Event of Default is not a continuing waiver. Bank's delay is not a waiver,
election, or acquiescence. No waiver hereunder shall be effective unless signed
by Bank and then is only effective for the specific instance and purpose for
which it was given.

     9.7    DEMAND WAIVER. Except as provided herein or by law, Borrower waives
(a) demand, (b) notice of default or dishonor, (c) notice of payment and
nonpayment, (d) notice of any default, nonpayment at maturity, release,
compromise, settlement, extension, or renewal of accounts, documents,
instruments, chattel paper, or guarantees held by Bank on which Borrower is
liable.

     10     NOTICES

     All notices or demands by any party to this Agreement or any other related
agreement must be in writing and be personally delivered or sent by an overnight
delivery service, by certified mail, postage prepaid, return receipt requested,
or by telefacsimile at the addresses listed below. Either Bank or Borrower may
change its notice address by giving the other party written notice.

            If to Borrower:      Momenta Pharmaceuticals, Inc.
                                 675 West Kendall Street
                                 Cambridge, Massachusetts 02142
                                 Attn: Mr. Richard Shea, Chief Financial Officer
                                 FAX: (617) 621-0431

            with a copy to:      Wilmer Cutler Pickering Hale and Dorr LLP
                                 60 State Street
                                 Boston, Massachusetts 02109
                                 Attn: Steven D. Singer, Esquire
                                 Fax: (617) 526- 5000

                                       -8-
<Page>

            If to Bank:          Silicon Valley Bank
                                 One Newton Executive Park, Suite 200
                                 2221 Washington Street
                                 Newton, Massachusetts 02462
                                 Attn: R. Bryan Jadot
                                 Fax:  (617) 969-5973

            with a copy to:      Riemer & Braunstein LLP
                                 Three Center Plaza
                                 Boston, Massachusetts 02108
                                 Attn: David A. Ephraim, Esquire
                                 FAX: (617) 880-3456

     11     CHOICE OF LAW, VENUE AND JURY TRIAL WAIVER

     Massachusetts law governs the Loan Documents without regard to principles
of conflicts of law. Borrower and Bank each submit to the exclusive jurisdiction
of the State and Federal courts in Massachusetts; provided, however, that if for
any reason Bank cannot avail itself of such courts in the Commonwealth of
Massachusetts, Borrower accepts jurisdiction of the courts and venue in Santa
Clara County, California. NOTWITHSTANDING THE FOREGOING, THE BANK SHALL HAVE THE
RIGHT TO BRING ANY ACTION OR PROCEEDING AGAINST THE BORROWER OR ITS PROPERTY IN
THE COURTS OF ANY OTHER JURISDICTION WHICH THE BANK DEEMS NECESSARY OR
APPROPRIATE IN ORDER TO REALIZE ON THE COLLATERAL OR TO OTHERWISE ENFORCE THE
BANK'S RIGHTS AGAINST THE BORROWER OR ITS PROPERTY.

BORROWER AND BANK EACH WAIVE THEIR RIGHT TO A JURY TRIAL OF ANY CLAIM OR CAUSE
OF ACTION ARISING OUT OF OR BASED UPON THIS AGREEMENT, THE LOAN DOCUMENTS OR ANY
CONTEMPLATED TRANSACTION, INCLUDING CONTRACT, TORT, BREACH OF DUTY AND ALL OTHER
CLAIMS. THIS WAIVER IS A MATERIAL INDUCEMENT FOR BOTH PARTIES TO ENTER INTO THIS
AGREEMENT. EACH PARTY HAS REVIEWED THIS WAIVER WITH ITS COUNSEL.

     12     GENERAL PROVISIONS

     12.1   SUCCESSORS AND ASSIGNS. This Agreement binds and is for the benefit
of the successors and permitted assigns of each party. Borrower may not assign
this Agreement or any rights or Obligations under it without Bank's prior
written consent which may be granted or withheld in Bank's reasonable
discretion. Bank has the right, without the consent of or prior notice to
Borrower, to sell, transfer, negotiate, or grant participation in all or any
part of, or any interest in, Bank's obligations, rights and benefits under this
Agreement, the Loan Documents or any related agreement. Bank shall provide
subsequent notice of any assignment of any of its rights under this Agreement.

     12.2   INDEMNIFICATION. Borrower hereby indemnifies, defends and holds the
Bank and its directors, officers, employees and agents harmless against: (a) all
obligations, demands, claims, and liabilities asserted by any other party or
Person in connection with the transactions contemplated by the Loan Documents;
and (b) all losses or Bank Expenses incurred, or paid by Bank from, following,
or consequential to transactions between Bank and Borrower arising or in
connection with the Loan Documents (including reasonable attorneys' fees and
expenses), except in the cases of clauses (a) and (b) for all obligations,
demands, claims, liabilities, losses and Bank Expenses caused by Bank's gross
negligence or willful misconduct.

     12.3   RIGHT OF SET-OFF. Borrower hereby grants to Bank a right of setoff
for all Obligations to Bank, whether now existing or hereafter arising upon and
against all deposits, credits, collateral and property, now or hereafter in the
possession, custody, safekeeping or control of Bank or any entity under the
control of the Bank (including a Bank subsidiary) or in transit to any of them.
At any time after the occurrence and during the

                                       -9-
<Page>

continuance of an Event of Default, without demand or notice, Bank may set off
the same or any part thereof and apply the same to any of the Obligations. ANY
AND ALL RIGHTS TO REQUIRE BANK TO EXERCISE ITS RIGHTS OR REMEDIES WITH RESPECT
TO ANY OTHER COLLATERAL WHICH SECURES THE OBLIGATIONS, PRIOR TO EXERCISING ITS
RIGHT OF SETOFF WITH RESPECT TO SUCH DEPOSITS, CREDITS OR OTHER PROPERTY OF THE
BORROWER ARE HEREBY KNOWINGLY, VOLUNTARILY AND IRREVOCABLY WAIVED.

     12.4   TIME OF ESSENCE. Time is of the essence for the performance of all
Obligations in this Agreement.

     12.5   SEVERABILITY OF PROVISION. Each provision of this Agreement is
severable from every other provision in determining the enforceability of any
provision.

     12.6   AMENDMENTS IN WRITING; INTEGRATION. All amendments to this Agreement
must be in writing signed by both Bank and Borrower. This Agreement and the Loan
Documents represent the entire agreement about this subject matter, and
supersede prior negotiations or agreements. All prior agreements,
understandings, representations, warranties, and negotiations between the
parties about the subject matter of this Agreement and the Loan Documents merge
into this Agreement and the Loan Documents.

     12.7   COUNTERPARTS. This Agreement may be executed in any number of
counterparts and by different parties on separate counterparts, each of which,
when executed and delivered, are an original, and all taken together, constitute
one Agreement.

     12.8   SURVIVAL. All covenants, representations and warranties made in this
Agreement continue in full force while any Obligations remain outstanding. The
obligation of Borrower in Section 12.2 to indemnify Bank shall survive until the
statute of limitations with respect to such claim or cause of action shall have
run.

     12.9   CONFIDENTIALITY. In handling any confidential information, Bank
shall exercise the same degree of care that it exercises for its own proprietary
information, but disclosure of information may be made: (i) to Bank's
subsidiaries or affiliates in connection with their business with Borrower,
subject to the limitations contained herein; (ii) to prospective transferees or
purchasers of any interest in the Credit Extensions (provided, however, Bank
shall prior to such disclosure use best efforts in obtaining such prospective
transferee's or purchaser's agreement to the terms of this provision); (iii) as
required by law, regulation, subpoena, or other order, (iv) as required in
connection with Bank's examination or audit; and (v) as Bank considers
appropriate in exercising remedies under this Agreement. Confidential
information does not include information that either: (a) is in the public
domain or in Bank's possession when disclosed to Bank, or becomes part of the
public domain after disclosure to Bank without resulting from disclosure by Bank
and through no fault of Bank; or (b) is first disclosed to Bank by a third
party, if Bank does not know that the third party is prohibited from disclosing
the information.

     13     DEFINITIONS

     13.1   DEFINITIONS. In this Agreement:

     "AFFILIATE" is a Person that owns or controls directly or indirectly the
Person, any Person that controls or is controlled by or is under common control
with the Person, and each of that Person's senior executive officers, directors,
partners and, for any Person that is a limited liability company, that Person's
managers and members.

     "BANK EXPENSES" are all audit fees and expenses and reasonable costs or
expenses (including reasonable attorneys' fees and expenses) for preparing,
negotiating, administering, defending and enforcing the Loan Documents
(including appeals or Insolvency Proceedings).

     "BASIC RATE" is fixed for each Equipment Advance, as of the Funding Date
for such Equipment Advance, at the per annum rate of interest (based on a year
of 360 days) equal to the sum of: (a) the U.S. Treasury note yield to maturity
for a term equal to the Treasury Note Maturity (interpolated if no rate is
listed for such specific month) as quoted in Bloomberg on the day the Loan
Supplement is prepared, plus (b) the Loan Margin.

                                      -10-
<Page>

     "BORROWER'S BOOKS" are all Borrower's books and records including ledgers,
records regarding Borrower's assets or liabilities, the Collateral, business
operations or financial condition and all computer programs or storage or any
equipment containing the information.

     "BUSINESS DAY" is any day that is not a Saturday, Sunday or a day on which
the Bank is closed.

     "CLOSING DATE" is the date of this Agreement.

     "CODE" is the Uniform Commercial Code as adopted in Massachusetts, as
amended and as may be amended and in effect from time to time.

     "COLLATERAL" is any and all properties, rights and assets of the Borrower
as described on EXHIBIT A.

     "CONTINGENT OBLIGATION" is, for any Person, any direct or indirect
liability, contingent or not, of that Person for (i) any indebtedness, lease,
dividend, letter of credit or other obligation of another such as an obligation
directly or indirectly guaranteed, endorsed, co-made, discounted or sold with
recourse by that Person, or for which that Person is directly or indirectly
liable; (ii) any obligations for undrawn letters of credit for the account of
that Person; and (iii) all obligations from any interest rate, currency or
commodity swap agreement, interest rate cap or collar agreement, or other
agreement or arrangement designated to protect a Person against fluctuation in
interest rates, currency exchange rates or commodity prices; but "Contingent
Obligation" does not include endorsements in the ordinary course of business.
The amount of a Contingent Obligation is the stated or determined amount of the
primary obligation for which the Contingent Obligation is made or, if not
determinable, the maximum reasonably anticipated liability for it determined by
the Person in good faith; but the amount may not exceed the maximum of the
obligations under any guarantee or other support arrangement.

     "CREDIT EXTENSION" is each Equipment Advance or any other extension of
credit by Bank for Borrower's benefit, pursuant to this Agreement.

     "DRAW PERIOD" is defined in Section 2.1.1(a).

     "ELIGIBLE EQUIPMENT" is Equipment, including new or used (a) general
purpose computer equipment, office equipment, test and laboratory equipment,
furnishings, subject to the limitations set forth herein, and (b) Other
Equipment that complies with all of Borrower's representations and warranties to
Bank.

     "EQUIPMENT" is all present and future machinery, equipment, lab test
equipment, and furniture in which Borrower has any interest.

     "EQUIPMENT ADVANCE" is defined in Section 2.1.1(a).

     "EQUIPMENT LINE" is an Equipment Advance or Equipment Advances of up to
Three Million Dollars ($ 3,000,000.00).

     "ERISA" is the Employment Retirement Income Security Act of 1974, and its
regulations.

     "FINANCED EQUIPMENT" is all present and future Eligible Equipment in which
Borrower has any interest, the purchase of which is financed by an Equipment
Advance.

     "FUNDING DATE" is any date on which an Equipment Advance is made to or on
account of Borrower.

     "GAAP" is generally accepted accounting principles.

     "GUARANTOR" is any present or future guarantor of the Obligations.

     "INDEBTEDNESS" is (a) indebtedness for borrowed money or the deferred price
of property or services, such as reimbursement and other obligations for surety
bonds and letters of credit, (b) obligations evidenced by notes, bonds,
debentures or similar instruments, (c) capital lease obligations and (d)
Contingent Obligations.

                                      -11-
<Page>

     "INSOLVENCY PROCEEDING" is any proceeding by or against any Person under
the United States Bankruptcy Code, or any other bankruptcy or insolvency law,
including assignments for the benefit of creditors, compositions, extensions
generally with its creditors, or proceedings seeking reorganization,
arrangement, or other relief.

     "INVESTMENT" is any beneficial ownership of (including stock, partnership
interest or other securities) any Person, or any loan, advance or capital
contribution to any Person.

     "LIEN" is a mortgage, lien, deed of trust, charge, pledge, security
interest or other encumbrance.

     "LOAN AMOUNT" in respect of each Equipment Advance is the original
principal amount of such Equipment Advance.

     "LOAN DOCUMENTS" are, collectively, this Agreement, any note, or notes or
guaranties executed by Borrower or Guarantor, and any other present or future
agreement between Borrower and/or for the benefit of Bank in connection with
this Agreement, all as amended, extended or restated.

     "LOAN MARGIN" is 500 basis points.

     "MATERIAL ADVERSE CHANGE " is: (i) A material impairment in the perfection
or priority of Bank's security interest in the Collateral or in the value of
such Collateral; or (ii) a material adverse change in the business, operations,
or condition (financial or otherwise) of the Borrower.

     "OBLIGATIONS" are debts, principal, interest, Bank Expenses and other
amounts Borrower owes Bank now or later under this Agreement, or the SVB Loan
Arrangement, including letters of credit, cash management services, and foreign
exchange contracts, if any, and including interest accruing after Insolvency
Proceedings begin and debts, liabilities, or obligations of Borrower assigned to
Bank.

     "ORIGINAL STATED COST" is (i), the original cost to the Borrower of the
item of new Eligible Equipment, or (ii) the fair market value assigned to such
item of used Eligible Equipment by mutual agreement of Borrower and Bank at the
time of making of the Equipment Advance.

     "OTHER EQUIPMENT" is leasehold improvements, transferable software
licenses, and soft costs, including sales tax, freight and installation
expenses. Unless otherwise agreed to by Bank, not more than twenty percent
(20.0%) of the proceeds of the Equipment Line shall be used to finance Other
Equipment.

     "PAYMENT DATE" is the first Business Day of each calendar month.

     PERMITTED INDEBTEDNESS" is:

                    (a)     Borrower's indebtedness to Bank under this
          Agreement, the SVB Loan Arrangement, or the Loan Documents;

                    (b)     Indebtedness existing on the Closing Date and shown
          on the Perfection Certificate;

                    (c)     Subordinated Debt;

                    (d)     Indebtedness to trade creditors incurred in the
          ordinary course of business; and

                    (e)     Indebtedness secured by Permitted Liens;

                    (f)     Extensions, refinancings, modifications, amendments
          and restatements of any items of Permitted Indebtedness (a) through
          (e) above, provided that the principal amount thereof is not increased
          or the terms thereof are not modified to impose more burdensome terms
          upon Borrower or its Subsidiary, as the case may be;

                                      -12-
<Page>

                    (g)     Other Indebtedness not otherwise permitted by
          Section 7.4 not exceeding One Million Dollars ($1,000,000.00), in the
          aggregate, outstanding at any time; and

                    (h)     Capital leases.

     "PERMITTED LIENS" are:

                    (a)     Liens existing on the Closing Date and shown on the
          Perfection Certificate or arising under this Agreement or other Loan
          Documents;

                    (b)     Liens for taxes, fees, assessments or other
          government charges or levies, either not delinquent or being contested
          in good faith and for which Borrower maintains adequate reserves on
          its Books;

                    (c)     Purchase money Liens (i) on Equipment acquired or
          held by Borrower incurred for financing the acquisition of the
          Equipment (now or in the future), or (ii) existing on equipment when
          acquired, IF the Lien is confined to the property and improvements and
          the proceeds of the equipment;

                    (d)     Leases or subleases and licenses or sublicenses
          granted in the ordinary course of Borrower's business or granted in
          connection with the consummation of collaborations, joint ventures, or
          financing arrangements with the Borrower's business partners in the
          ordinary course of business; and

                    (e)     Liens incurred in the extension, renewal or
          refinancing of the indebtedness secured by Liens described in (a)
          through (d), BUT any extension, renewal or replacement Lien must be
          limited to the property encumbered by the existing Lien and the
          principal amount of the indebtedness may not increase.

     "PERSON" is any individual, sole proprietorship, partnership, limited
liability company, joint venture, company, trust, unincorporated organization,
association, corporation, institution, public benefit corporation, firm, joint
stock company, estate, entity or government agency.

     "REPAYMENT PERIOD" as to each Equipment Advance, is a period of time equal
to forty-two (42) consecutive months commencing on the first Business Day of the
month following the month in which the Funding Date occurs (or commencing on the
Funding Date if the Funding Date is the first Business Day of the month).

     "RESPONSIBLE OFFICER" is each of the Chief Executive Officer and Chief
Financial Officer of Borrower.

     "SCHEDULED PAYMENT" is defined in Section 2.1.1(b).

     "SUBORDINATED DEBT" is debt incurred by Borrower subordinated to Borrower's
debt to Bank (pursuant to a subordination agreement entered into between the
Bank, the Borrower and the subordinated creditor), on terms acceptable to Bank.

     "SUBSIDIARY" is any Person, corporation, partnership, limited liability
company, joint venture, or any other business entity of which more than 50% of
the voting stock or other equity interests is owned or controlled, directly or
indirectly, by the Person or one or more Affiliates of the Person.

     "SVB LOAN ARRANGEMENT" is that certain Loan and Security Agreement dated as
of December 27, 2002, by and between Borrower and Bank, as amended, restated and
modified from time to time.

     "TREASURY NOTE MATURITY" is forty-two (42) months.

                                      -13-
<Page>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as a sealed instrument under the laws of the Commonwealth of
Massachusetts as of the date first above written.

BORROWER:

MOMENTA PHARMACEUTICALS, INC.

By:  /s/ Richard P. Shea
     -------------------
Name: Richard P. Shea
      ---------------
Title: Vice President and Chief Executive Officer
       ------------------------------------------

BANK:
SILICON VALLEY BANK, d/b/a
SILICON VALLEY EAST

By:  /s/ R. Bryan Jadot
     ------------------
Name:  R. Bryan Jadot
       --------------
Title:  Vice President
       ---------------

SILICON VALLEY BANK

By:  [illegible]
     -----------
Name:  [illegible]
       -----------
Title: [illegible]
       -----------
(Signed in Santa Clara County, California)

                                       S-1
<Page>

                                    EXHIBIT A

     The Collateral consists of all of Borrower's right, title and interest in
and to the following:

     1.     Each item of equipment, or personal property financed with a
"Equipment Advance" pursuant to that certain Loan and Security Agreement, dated
as of _______________, 2004 (the "Loan Agreement"), by and between Borrower and
Bank, including, without limitation, the property described in ANNEX A hereto,
whether now owned or hereafter acquired, together with all substitutions,
renewals or replacements of and additions, improvements, and accessions to any
and all of the foregoing, and all proceeds from sales, renewals, releases or
other dispositions thereof.

     2.     All Borrower's books relating to the foregoing and any and all
claims, rights and interest in any of the above and all substitutions for,
additions, attachments, accessories, accessions and improvements to and
replacements, products, proceeds and insurance proceeds of any or all of the
foregoing.

                                   Exhibit A-1
<Page>

                              ANNEX A TO EXHIBIT A

     The Financed Equipment being financed with the Equipment Advance is listed
below. Upon the funding of such Equipment Advance, this schedule automatically
shall be deemed to be a part of the Collateral.

<Table>
<Caption>
     Description of Equipment            Make               Model                 Serial #        Invoice#
     -----------------------------------------------------------------------------------------------------
     <S>                                 <C>                <C>                   <C>             <C>

</Table>

                                   Exhibit A-2
<Page>

                                    EXHIBIT B
                        FORM OF LOAN AGREEMENT SUPPLEMENT

                        LOAN AGREEMENT SUPPLEMENT No. [ ]

     LOAN AGREEMENT SUPPLEMENT No. [ ], dated _______________, 200_
("Supplement"), to the Loan and Security Agreement dated as of _______________,
2004 (the "Loan Agreement) by and between the undersigned Momenta
Pharmaceuticals, Inc. ("Borrower"), and Silicon Valley Bank ("Bank").

     Capitalized terms used herein but not otherwise defined herein are used
with the respective meanings given to such terms in the Loan Agreement.

To secure the prompt payment by Borrower of all amounts from time to time
outstanding under the Loan Agreement, and the performance by Borrower of all the
terms contained in the Loan Agreement, Borrower grants Bank, a first priority
security interest in each item of equipment and other property described in
Annex A hereto, which equipment and other property shall be deemed to be
additional Financed Equipment and Collateral. The Loan Agreement is hereby
incorporated by reference herein and is hereby ratified, approved and confirmed.
Annex A (Equipment Schedule) and Annex B (Loan Terms Schedule) are attached
hereto. The proceeds of the Loan should be transferred to Borrower's account
with Bank set forth below:

          Bank Name:                        Silicon Valley Bank
          Account No.:                      _______________

Borrower hereby certifies that (a) the foregoing information is true and correct
and authorizes Bank to endorse in its respective books and records, the Basic
Rate applicable to the Funding Date of the Loan contemplated in this Loan
Agreement Supplement and the principal amount set forth in the Loan Terms
Schedule; (b) the representations and warranties made by Borrower in the Loan
Agreement are true and correct on the date hereof and shall be true and correct
on such Funding Date. No Event of Default has occurred and is continuing under
the Loan Agreement. This Supplement may be executed by Borrower and Bank in
separate counterparts, each of which when so executed and delivered shall be an
original, but all such counterparts shall together constitute but one and the
same instrument.

     This Supplement is delivered as of this day and year first above written.

SILICON VALLEY BANK                               MOMENTA PHARMACEUTICALS, INC.

By:                                               By:
   -----------------------------------               ---------------------------
   Name:                                             Name:
   Title:                                            Title:

Annex A - Description of Financed Equipment
Annex B - Loan Terms Schedule

                                   Exhibit D-1
<Page>

                              ANNEX A TO EXHIBIT B

     The Financed Equipment being financed with the Equipment Advance which this
Loan Agreement Supplement is being executed is listed below. Upon the funding of
such Equipment Advance, this schedule automatically shall be deemed to be a part
of the Collateral.

<Table>
<Caption>
    Description of Equipment            Make               Model                 Serial #        Invoice#
    -----------------------------------------------------------------------------------------------------
    <S>                                 <C>                <C>                   <C>             <C>

</Table>

                                   Exhibit D-2
<Page>

                              ANNEX B TO EXHIBIT B

                           LOAN TERMS SCHEDULE #______

Loan Funding Date:  _____________, 200_

Original Loan Amount:  $____________

Basic Rate:  ______%

Scheduled Payment Dates and Amounts*:

<Table>
     <S>                                                                   <C>
     One (1) payment of $_______ due ______________
     ______  payment of $_______ due monthly in advance from ______        through ________.
     One (1) payment of $_______ due ______________
</Table>

Maturity Date:  ____________

<Table>
        Payment No.               Payment Date
           <S>                    <C>
             1

             2

             3

             4

           . . .
             35

            [36]

           . . .
</Table>

*/   The amount of each Scheduled Payment shall change as the Loan Amount
     changes.

                                   Exhibit D-3<Page>

                                                                   Exhibit 10.47

<Table>
<S>                                       <C>                                   <C>
MOMENTA PHARMACEUTICALS, INC.             675 WEST KENDALL STREET               T: 617.491.9700 F: 617.621.0431
                                          CAMBRIDGE, MA 02142                   WWW.MOMENTAPHARMA.COM
</Table>

[MOMENTA LOGO]

                                November 2, 2004

Joseph Tyler
22 Forster Street
Somerville, Massachusetts 02145

Dear Joe:

In connection with the termination of your employment with Momenta
Pharmaceuticals, Inc. (the "Company") effective as of November 15, 2004 (the
"Termination Date"), in particular from your position of Vice President of
Manufacturing, you are eligible to receive the benefits described in this
letter.

By signing and returning this letter, you will be entering into a binding
agreement with the Company and will be agreeing to the terms and conditions set
forth in the numbered paragraphs below, including the release of claims set
forth in paragraph 4. Therefore, you are advised to consult with an attorney
before signing this letter and you may take up to twenty-one (21) days to do so.
If you sign this letter, you may change your mind and revoke your agreement
during the seven (7) day period after you have signed it. If you do not so
revoke, this letter will become a binding agreement between you and the Company
after the expiration of the seven (7) day revocation period.

Regardless of whether you sign this letter you will receive payment upon your
termination for any unused vacation time accrued through the Termination Date
and you may elect to continue receiving group medical insurance pursuant to the
federal "COBRA" law, 29 U.S.C. Section 1161 ET SEQ. All premium costs shall be
paid by you on a monthly basis for as long as, and to the extent that, you
remain eligible for COBRA continuation. You should consult the COBRA materials
to be provided by the Company for details regarding these benefits. All other
benefits, including life insurance and long term disability, will cease upon
your Termination Date. Pursuant to the Company's Amended and Restated 2002 Stock
Incentive Plan, you will have up to thirty (30) days after the Termination Date
to exercise any previously vested stock rights you may have (the "Exercise
Period") unless extended as set forth below. All unvested stock rights will be
cancelled on the Termination Date.

If, after reviewing this letter agreement with an attorney, you find the terms
and conditions are satisfactory to you, you should sign and return this letter
to Richard P. Shea in the enclosed envelope by November 23, 2004.

The following numbered paragraphs set forth the terms and conditions which will
apply if and only if you timely sign and return this letter agreement and do not
revoke it within the seven (7) day period:

<Page>

1.    TERMINATION DATE - Your effective date of termination from the Company is
      November 15, 2004 (the "Termination Date").

2.    OPTION ACCELERATION - In consideration for the release of claims set forth
      in Paragraph 4 and your agreeing that you will use your best efforts to
      facilitate the effective transition of your departure and the integration
      of your replacement, the Company has agreed to a one-year acceleration of
      the vesting of your stock options that are unvested as of the Termination
      Date. In addition, subject to the Company's Chief Executive Officer's
      assessment of your performance during such transition period and for a
      reasonable time thereafter, at the Company's sole discretion, you may be
      entitled to additional acceleration of the vesting of your stock options
      unvested as of the Termination Date, however such acceleration shall not
      in any event exceed an additional one-year acceleration. If applicable,
      you will be notified of such additional accelerated options in writing by
      the earlier of the 8th day after the execution of this letter agreement or
      December 1, 2004.

3.    EXTENSION TO EXERCISE PERIOD - As further consideration for the release of
      claims set forth in Paragraph 4 and your agreeing to use your best efforts
      to facilitate the effective transition of your departure and the
      integration of your replacement, the Company has agreed to amend the
      Exercise Period to provide you with a ninety (90) day exercise period (the
      "Extended Exercise Period") to exercise both previously vested and any
      accelerated options.

4.    RELEASE - In consideration of the consideration set forth herein, which
      you acknowledge you would not otherwise be entitled to receive, you hereby
      fully, forever, irrevocably and unconditionally release, remise and
      discharge the Company, its officers, directors, stockholders, corporate
      affiliates, subsidiaries, parent companies, agents and employees (each in
      their individual and corporate capacities) (hereinafter, the "Released
      Parties") from any and all claims, charges, complaints, demands, actions,
      causes of action, suits, rights, debts, sums of money, costs, accounts,
      reckonings, covenants, contracts, agreements, promises, doings, omissions,
      damages, executions, obligations, liabilities, and expenses (including
      attorneys' fees and costs), of every kind and nature which you ever had or
      now have against the Released Parties arising out of your employment with
      and/or separation from the Company, including, but not limited to, all
      employment discrimination claims under Title VII of the Civil Rights Act
      of 1964, 42 U.S.C. Section 2000e ET SEQ., the Age Discrimination in
      Employment Act, 29 U.S.C. Section 621 ET SEQ., the Americans With
      Disabilities Act of 1990, 42 U.S.C., Section 12101 ET SEQ., the Family and
      Medical Leave Act, 29 U.S.C. Section 2601 ET SEQ., the Worker Adjustment
      and Retraining Notification Act ("WARN"), 29 U.S.C. Section 2101 ET SEQ.,
      and the Rehabilitation Act of 1973, 29 U.S.C. Section 701 ET SEQ., all as
      amended; all claims arising out of the Fair Credit Reporting Act, 15
      U.S.C. Section 1681 ET SEQ., the Employee Retirement Income Security Act
      of 1974 ("ERISA"), 29 U.S.C. Section 1001 ET seq., the Massachusetts Fair
      Employment Practices Act., M.G.L. c.151B, Section 1 ET SEQ., the
      Massachusetts Civil Rights Act, M.G.L. c.12 Sections 11H and 11I, the
      Massachusetts Equal Rights Act, M.G.L. c.93, Section 102 and M.G.L. c.214,
      Section 1C, the Massachusetts Labor and Industries Act, M.G.L. c.149,
      Section 1 ET SEQ., the

                                                                               2
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      Massachusetts Privacy Act, M.G.L. c. 214, Section 1B, and the
      Massachusetts Maternity Leave Act , M.G.L. c. 149, Section 105(d), all as
      amended; all common law claims including, but not limited to, actions in
      tort, defamation and breach of contract; all claims to any non-vested
      ownership interest in the Company, contractual or otherwise, including but
      not limited to claims to stock or stock options except as provided in
      Paragraphs 2 and 3; and any claim or damage arising out of your employment
      with or separation from the Company (including a claim for retaliation)
      under any common law theory or any federal, state or local statute or
      ordinance not expressly referenced above; provided, however, that nothing
      in this letter agreement prevents you from filing, cooperating with, or
      participating in any proceeding before the EEOC or a state Fair Employment
      Practices Agency (except that you acknowledge that you may not be able to
      recover any monetary benefits in connection with any such claim, charge or
      proceeding or from enforcing the terms of this letter agreement).

5.    NON-DISCLOSURE, NON-COMPETITION AND NON-SOLICITATION OBLIGATIONS - You
      acknowledge and reaffirm your obligation to keep confidential and not to
      disclose any and all non-public information concerning the Company which
      you acquired during the course of your employment with the Company,
      including, but not limited to, any non-public information concerning the
      Company's business affairs, business prospects and financial condition as
      is stated more fully in the Employee Nondisclosure, Noncompetition and
      Assignment of Intellectual Property Agreement you executed at the
      inception of your employment which remains in full force and effect. You
      further acknowledge and reaffirm your obligations under the Employee
      Nondisclosure, Noncompetition and Assignment of Intellectual Property
      Agreement you previously executed for the benefit of the Company at the
      inception of your employment, which also remain(s) in full force and
      effect, a copy of which is attached hereto for your convenience.

6.    RETURN OF COMPANY PROPERTY - You confirm that you have returned to the
      Company all keys, files, records (and copies thereof), equipment
      (including, but not limited to, computer hardware, software and printers,
      wireless handheld devices, cellular phones, pagers, etc.), parking passes,
      Company identification, Company vehicles and any other Company-owned
      property in your possession or control and have left intact all electronic
      Company documents, including but not limited to those which you developed
      or help develop during your employment. You further confirm that you have
      cancelled all accounts for your benefit, if any, in the Company's name,
      including but not limited to, credit cards, telephone charge cards,
      cellular phone and/or pager accounts and computer accounts.

7.    BUSINESS EXPENSES AND COMPENSATION - You acknowledge that you have been
      reimbursed by the Company for all business expenses incurred in
      conjunction with the performance of your employment and that no other
      reimbursements are owed to you. You further acknowledge that you have
      received payment in full for all services rendered in conjunction with
      your employment by the Company and that no other compensation is owed to
      you.

                                                                               3
<Page>

8.    NON-DISPARAGEMENT - You understand and agree that you shall not make any
      false, disparaging or derogatory statements to any media outlet, industry
      group, financial institution or current or former employee, consultant,
      vendor, client or customer of the Company regarding the Company or any of
      its directors, officers, employees, agents, representatives or about the
      Company's business affairs and financial condition. The Company agrees
      that it will direct its officers and managers with knowledge of this
      letter agreement and Company's Senior Directors not to make any
      disparaging or derogatory statements about you. The Company will also
      direct its officers and managers with knowledge of this letter agreement
      and Company's Senior Directors to respond to any inquiries from
      prospective employers by confirming your title and dates of employment
      only.

9.    COOPERATION WITH CLAIMS OR ACTIONS - You agree to make yourself available
      upon receiving reasonable notice to cooperate with the Company in the
      defense or prosecution of any claims or actions which may be brought
      against or on behalf of the Company. You agree that you will notify the
      Company promptly in the event that you are served with a subpoena or are
      asked to provide a third party with information concerning any actual or
      potential complaint or claim against the Company or being brought by the
      Company. You agree that, if called to testify in any proceeding in court,
      at arbitration or before an administrative agency, you will testify
      truthfully under all circumstances. Subject to the foregoing, you agree to
      make yourself available upon receiving reasonable notice to meet with
      counsel for the Company in connection with the Company's preparation of
      its claims or defenses.

10.   AMENDMENT - This letter agreement shall be binding upon the parties and
      may not be modified in any manner, except by an instrument in writing of
      concurrent or subsequent date signed by duly authorized representatives of
      the parties hereto. This letter agreement is binding upon and shall inure
      to the benefit of the parties and their respective agents, assigns, heirs,
      executors, successors and administrators.

11.   WAIVER OF RIGHTS - No delay or omission by the Company in exercising any
      right under this letter agreement shall operate as a waiver of that or any
      other right. A waiver or consent given by the Company on any one occasion
      shall be effective only in that instance and shall not be construed as a
      bar or waiver of any right on any other occasion.

12.   VALIDITY - Should any provision of this letter agreement be declared or be
      determined by any court of competent jurisdiction to be illegal or
      invalid, the validity of the remaining parts, terms or provisions shall
      not be affected thereby and said illegal or invalid part, term or
      provision shall be deemed not to be a part of this letter agreement.

13.   CONFIDENTIALITY - You understand and agree that as a condition of the
      stock option provisions set forth in paragraphs 2 and 3 and of the terms
      and conditions herein described, the terms and contents of this letter
      agreement, and the contents

                                                                               4
<Page>

      of the negotiations and discussions resulting in this letter agreement,
      shall be maintained as confidential by you and your agents and
      representatives and shall not be disclosed except to the extent required
      by federal or state law or as otherwise agreed to in writing by the
      Company. You further understand that Company may be required to file this
      letter agreement with the Securities Exchange Commission and/or other
      governmental agencies.

14.   NATURE OF AGREEMENT - You understand and agree that this letter agreement
      is a separation agreement and does not constitute an admission of
      liability or wrongdoing on the part of the Company.

15.   ACKNOWLEDGMENTS - You acknowledge that you have been given at least
      twenty-one (21) days to consider this letter agreement and that the
      Company advised you to consult with an attorney of your own choosing prior
      to signing this letter agreement. You understand that you may revoke this
      letter agreement for a period of seven (7) days after you sign this letter
      agreement, and the letter agreement shall not be effective or enforceable
      until the expiration of this seven (7) day revocation period. YOU
      UNDERSTAND AND AGREE THAT BY ENTERING INTO THIS LETTER AGREEMENT YOU ARE
      WAIVING ANY AND ALL RIGHTS OR CLAIMS YOU MIGHT HAVE UNDER THE AGE
      DISCRIMINATION IN EMPLOYMENT ACT, AS AMENDED BY THE OLDER WORKERS BENEFIT
      PROTECTION ACT, AND THAT YOU HAVE RECEIVED CONSIDERATION BEYOND THAT TO
      WHICH YOU WERE PREVIOUSLY ENTITLED.

16.   VOLUNTARY ASSENT - You affirm that no other promises or agreements of any
      kind have been made to or with you by any person or entity whatsoever to
      cause you to sign this letter agreement, and that you fully understand the
      meaning and intent of this letter agreement. You state and represent that
      you have had an opportunity to fully discuss and review the terms of this
      letter agreement with an attorney. You further state and represent that
      you have carefully read this letter agreement understand the contents
      herein, freely and voluntarily assent to all of the terms and conditions
      hereof, and sign your name of your own free act.

17.   APPLICABLE LAW - This letter agreement shall be interpreted and construed
      by the laws of the Commonwealth of Massachusetts, without regard to
      conflict of laws provisions. You hereby irrevocably submit to and
      acknowledge and recognize the jurisdiction of the courts of the
      Commonwealth of Massachusetts, or if appropriate, a federal court located
      in Massachusetts (which courts, for purposes of this letter agreement, are
      the only courts of competent jurisdiction), over any suit, action or other
      proceeding arising out of, under or in connection with this letter
      agreement or the subject matter hereof.

18.   ENTIRE AGREEMENT - This letter agreement contains and constitutes the
      entire understanding and agreement between the parties hereto with respect
      to your termination of employment and the settlement of claims against the
      Company and cancels all previous oral and written negotiations,
      agreements, commitments and writings in connection therewith. Nothing in
      this paragraph, however, shall modify, cancel or supersede your
      obligations set forth in paragraph 5 herein.

                                                                               5
<Page>

If you have any questions about the matters covered in this letter, please call
me.

                                        Very truly yours,

                                        Momenta Pharmaceuticals, Inc.

                                        By: /s/ Alan L. Crane
                                            -----------------

                                        Name:  Alan L. Crane

                                        Title: Chief Executive Officer

I hereby agree to the terms and conditions set forth above. I have been given at
least twenty-one (21) days to consider this agreement and I have chosen to
execute this on the date below. I intend that this letter agreement become a
binding agreement between me and the Company if I do not revoke my acceptance in
seven (7) days.

/s/ Joseph Tyler                        Date: November 15, 2004
----------------------------                  -----------------
Employee Name:

To be returned by November 23, 2004.

                                                                               6

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