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                                                                   EXHIBIT 10.19

                              CONSULTING AGREEMENT
                               (Ram Sasisekharan)

         This Consulting Agreement dated as of August 16, 2001 (this
"Agreement"), is made by and between Mimeon, Inc., a Delaware corporation (the
"Company"), and Ram Sasisekharan ("Consultant").

         WHEREAS, the Company desires to engage Consultant to perform consulting
services on behalf of the Company and Consultant desires to perform such
services on the terms and conditions hereinafter set forth.

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants set forth herein the parties hereby agree as follows:

         1.       TERM. The Company agrees to retain Consultant, and Consultant
agrees to provide services to and on behalf of the Company on the terms and
conditions set forth in this Agreement during the period commencing on the date
hereof and ending on the second anniversary of the date hereof subject to
earlier termination as provided herein. This Agreement may be renewed for one or
more additional one (1) year renewal terms by mutual agreement of the Company
and Consultant prior to the expiration of the initial term or then applicable
renewal term.

         2.       SERVICES.  Consultant shall provide services to the Company as
may be mutually determined by the Company and Consultant from time to time. In
determining and mutually agreeing upon the times and locations for the
performance by Consultant of his services hereunder, due consideration shall be
given to Consultant's commitments to the Massachusetts Institute of Technology
("M.I.T."), where he is on the faculty, or any future employer of Consultant.

         3.       COMPENSATION.

                  3.1      As compensation for his services hereunder, the
Company shall pay Consultant a consulting fee payable quarterly in arrears on
the last day of September, December, March and June of each year during the term
of this Agreement and all renewal terms of this Agreement. Such consulting fee
shall initially be $0.00, but shall increase upon the occurrence of the
following events: (i) to $25,000 per 365-day period on and after the Initial
Milestone Date (as defined below) and continuing until the Second Milestone Date
(as defined below), (ii) to $50,000 per 365-day period on and after the Second
Milestone Date and continuing until the Third Milestone Date (as defined below);
and (iii) to $100,000 per 365-day period on and after the Third Milestone Date.

         As used herein, the term "Initial Milestone Date" shall mean the date
upon which the cumulative Cash Flow (as defined below) received by the Company
shall be greater than $7,150,000; the term "Second Milestone Date" shall mean
the date upon which the cumulative Cash Flow received by the Company shall be
greater than $17,150,000; and the term "Third Milestone Date" shall mean the
earlier to occur of (i) the date upon which the cumulative Cash Flow received by
the Company shall be greater than $50,000,000, (ii) the consummation by the

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Company of an Initial Public Offering (as defined below) or (iii) the sale of
the Company in a merger or consolidation in which the Company is not the
surviving corporation or in which the Company is the surviving corporation but
becomes a wholly-owned subsidiary of another corporation, or involving the sale
of substantially all of the Company's assets. The term "Cash Flow" shall include
all funds received by the Company (other than funds which must be repaid),
including, without limitation, the proceeds of the sale of equity securities by
the Company and the committed proceeds for equity and research funding in
connection with a strategic alliance or corporate partnering transaction with a
third party in the Field of Interest (as defined below). The term "Field of
Interest" shall mean the field of sequencing of, and chemical, enzymatic or
biological synthesis, production or modification of, linear and branched sugars
and glycoconjugates. The term "Initial Public Offering" means a firm commitment
underwritten public offering of the Company's common stock pursuant to an
effective registration statement under the Securities Act of 1933, as amended,
in which the price per share is at least $5.00 (subject to equitable adjustment
in the event of stock splits and the like) and the aggregate gross proceeds to
the Company from such offering are not less than $10,000,000.

                  3.2      Consultant shall be reimbursed for all reasonable,
appropriate or necessary travel and other out-of-pocket expenses incurred in the
performance of his duties hereunder upon submission and approval of written
statements and bills in accordance with the then regular reimbursement
procedures of the Company.

         4.       TERMINATION.

                  4.1      TERMINATION EVENTS.  The engagement of Consultant by
the Company pursuant to this Agreement may be terminated under the following
circumstances:

                           (a)      DEATH.  Upon the death of Consultant, which
termination shall be effective as of the date of Consultant's death.

                           (b)      DISABILITY.  If, in the opinion of a
physician satisfactory to both Consultant and the Company, Consultant has been
unable to perform the services to be performed by Consultant under this
Agreement due to a physical or mental illness which has resulted in such
disability for not fewer than 180 consecutive days; provided, however, that if
Consultant and the Company do not agree on a physician, Consultant and the
Company shall each select a physician and these two together shall select a
third physician whose determination as to disability shall be binding on both
parties. Termination under this Section 4.2 shall be effective after 30 days'
written notice has been given to Consultant following the determination of such
a disability.

                           (c)      CAUSE.  The Company may terminate the
Consultant's engagement hereunder for Cause. For purposes of this Agreement, the
Company shall have "Cause" to terminate Consultant's engagement hereunder in the
event:

                                    (i)     (A)   Consultant shall have
willfully failed and continued to fail substantially to perform the services
required under this Agreement (other than any failure resulting from the
Consultant's incapacity due to physical or mental illness) for 30 days after a
written demand specifying such failure and demanding performance is delivered to
Consultant

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on behalf of the Company and (B) such failure to perform has had a material,
adverse effect on the business or financial condition of the Company; provided,
however, the Company shall be deemed not to have "Cause" unless and until each
of the conditions specified in clauses (A) and (B) of this sentence have been
satisfied;

                                    (ii)    Consultant shall have engaged in
(A) any material and intentional misappropriation of funds, properties or assets
of the Company, it being understood that "material" for these purposes shall
take into account both the amount of funds, properties or assets misappropriated
and the circumstances thereof or (B) any malicious damage or destruction of any
property or assets of the Company, whether resulting from Consultant's willful
actions or omissions or Consultant's gross negligence; or

                                    (iii)   Consultant shall (A) have been
convicted of a crime involving moral turpitude or constituting a felony or (B)
entered a plea of nolo contendere to any such crime, either of which has had a
material adverse effect on the business of the Company; or

         Termination under this Section 4.1(c) shall be effective after 30 days'
written notice has been given to Consultant specifying that Cause exists and
exactly what the Cause is for such termination.

                           (d)      WITHOUT CAUSE.  The Company may terminate
the Consultant's engagement hereunder without Cause upon ninety (90) days' prior
written notice to the Consultant. In the event that the Company terminates the
Consultant's engagement without Cause, the Company shall continue to pay the
Consultant the fees payable in accordance with Section 3.1 until the date six
months after the date of the notice of termination.

                           (e)      RESIGNATION.  Consultant may terminate his
engagement hereunder upon ninety (90) days' prior written notice to the Company.

                  4.2      LIQUIDATED DAMAGES.  In the event that the engagement
of Consultant by the Company is terminated pursuant to Sections 4.1(c) or (e),
Consultant shall promptly pay the Company liquidated damages equal to:

                  LD = TO (48 - M) X P
                       ---------------
                              48

                  Where:    LD    =    The liquidated damages due to the Company
                                       pursuant to this Section 4.2.

                            M     =    The number of calendar months that have
                                       elapsed, in whole or in part, since the
                                       date of this Agreement.

                            P     =    The greater of (i) $100,000 or (ii) the
                                       total amount of compensation received by
                                       Consultant pursuant to this Agreement
                                       during the calendar year preceding the
                                       termination of his engagement.

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         The Consultant acknowledges that it would be difficult to measure or
prove the actual damages that the Company would incur in the event of a
termination of Consultant's services pursuant to Sections 4.1(c) or (e) and
agrees that this formula for determining liquidated damages is a reasonable
method for estimating such damages.

                  4.3      SURVIVAL. Notwithstanding any other provision of this
Section 4, the provisions of Sections 5, 6, 7, 8, 9 and 10 hereof shall survive
the expiration or sooner termination of this Agreement.

         5.       CONFIDENTIALITY.

                  5.1      Consultant understands that the Company continually
obtains and develops valuable proprietary and confidential information
concerning its scientific or business affairs (the "Confidential Information")
which may become known to him in connection with his engagement by the Company.

                  5.2      Consultant acknowledges that all Confidential
Information, whether or not in writing and whether or not labeled or identified
as confidential or proprietary, is and shall remain the exclusive property of
the Company or the third party providing such information to Consultant or the
Company. By way of illustration, but not limitation, Confidential Information
may include Inventions (as defined in Section 6.1), trade secrets, technical
information, know-how, research and development activities of the Company,
product and marketing plans, customer and supplier information and information
disclosed to the Company or to him by third parties of a proprietary or
confidential nature or under an obligation of confidence. Confidential
Information is contained in various media, including without limitation, patent
applications, research data and observations, records of clinical trials,
computer programs in object and/or source code, technical specifications,
laboratory notebooks, supplier and customer lists, internal financial data and
other documents and records of the Company.

                  5.3      Consultant agrees that Consultant shall not, during
the term of his engagement by the Company and thereafter, publish, disclose or
otherwise make available to any third party, other than employees of the
Company, any Confidential Information except as expressly authorized in writing
by the Company. Consultant agrees that Consultant shall use such Confidential
Information only in the performance of his duties for the Company and in
accordance with any Company policies with respect to the protection of
Confidential Information. Consultant agrees not to use such Confidential
Information for his own benefit or for the benefit of any other person or
business entity.

                  5.4      Consultant agrees to exercise all reasonable
precautions to protect the integrity and confidentiality of Confidential
Information in his possession and not to remove any materials containing
Confidential Information from the Company's premises except to the extent
necessary to his performance of consulting services for the benefit of the
Company. Upon the termination of his engagement by the Company, or at any time
upon the Company's request, Consultant shall return immediately to the Company
any and all materials containing any Confidential Information then in his
possession or under his control.

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                  5.5      Confidential Information shall not include
information which (a) is or becomes generally known within the Company's
industry through no fault of Consultant; (b) was known to him at the time it was
disclosed as evidenced by his written records at the time of disclosure; (c) is
lawfully and in good faith made available to him by a third party who did not
derive it from the Company and who imposes no obligation of confidence on
Consultant; or (d) is required to be disclosed by a governmental authority or by
order of a court of competent jurisdiction, provided that reasonable advance
notice is given to the Company and Consultant cooperates with the Company in
reasonable measure to seek to secure protection for such material.

         6.       ASSIGNMENT OF INVENTIONS.

                  6.1      Consultant agrees promptly to disclose to the Company
any and all ideas, concepts, discoveries, inventions, developments, trade
secrets, methods, data, information, improvements, chemical or biological
materials and know-how that are conceived, devised, invented, developed or
reduced to practice or tangible medium by Consultant, under his direction or
jointly with others, in the course of his performing services for the Company,
whether or not during normal working hours or on the premises of the Company,
which relate, directly or indirectly, to the business of the Company and arise
out of his engagement by the Company (hereinafter "Inventions").

                  6.2      Consultant hereby assigns to the Company all of his
right, title and interest to the Inventions and any and all related patent
rights, copyrights and applications and registrations therefor. During and after
his engagement by the Company, Consultant shall cooperate with the Company, at
the Company's expense, in obtaining proprietary protection for the Inventions
and Consultant shall execute all documents which the Company shall reasonably
request in order to perfect the Company's rights in the Inventions. Consultant
hereby appoints the Company his attorney to execute and deliver any such
documents on his behalf in the event Consultant should fail or refuse to do so
within a reasonable period following the Company's request.

                  6.3      Consultant further represents that the attached
SCHEDULE A contains a complete list of all inventions in the Field of Interest,
made, conceived or first reduced to practice by Consultant, under his direction
or jointly with others prior to his engagement with the Company ("Prior
Inventions") and which are not assigned to the Company hereunder. If there is no
such SCHEDULE A attached hereto, Consultant represents that there are no such
Prior Inventions.

         7.       OTHER AGREEMENTS

                  7.1      Consultant hereby represents to the Company that,
except as provided in Section 7.3 or as identified on SCHEDULE B, Consultant is
not bound by any agreement or any other previous or existing business
relationship which conflicts with or prevents the full performance of his duties
and obligations to the Company (including his duties and obligations under this
or any other agreement with the Company) during the period of his engagement by
the Company.

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                  7.2      Consultant understands that the Company does not
desire to acquire from him any business information Consultant may have or any
trade secrets, know-how or confidential business information Consultant may have
acquired from others. Therefore, Consultant agrees that during the period of his
engagement by the Company, Consultant will not improperly use or disclose any
proprietary information or trade secrets of any former or concurrent employer,
or any other person or entity with whom Consultant has an agreement or to whom
Consultant owes a duty to keep such information in confidence. Those persons or
entities with whom Consultant has such agreements or to whom Consultant owes
such a duty are identified in Section 7.3 or on SCHEDULE B.

                  7.3      Consultant recognizes that as a faculty member of
M.I.T., Consultant is responsible for ensuring that any consulting agreement
that Consultant enters into with a for-profit entity is not in conflict with the
patent, consulting or other policies of M.I.T., and Consultant hereby represents
and warrants that Consultant has determined that this Agreement complies with
all such policies of M.I.T. If Consultant is required by M.I.T. to disclose to
M.I.T. any proposed agreements with industry, Consultant hereby represents that
Consultant has made such disclosure and obtained any necessary formal approvals
of this Agreement by M.I.T.

         8.       EXCLUSIVE COMMITMENT. Consultant agrees that during the period
of his engagement by the Company and for a period of one (1) year after
termination or cessation of such engagement for any reason, Consultant shall
not, without the Company's prior written consent, which shall not be
unreasonably withheld, become involved, as a principal, employee, partner, or
holder of more than 5% of the outstanding capital stock of any business
enterprise that has committed significant resources to the Field of Interest. In
addition, for so long as Christoph Westphal is a principal of Polaris Venture
Partners III, L.P. ("Polaris") and Polaris is a holder of capital stock of the
Company, Consultant shall not, without the prior verbal consent of Christoph
Westphal, which shall not be unreasonably withheld, perform consulting services
in the Field of Interest for or on behalf of any business enterprise.

         9.       GENERAL NON-SOLICITATION. Consultant agrees that during his
engagement with the Company and for a period of two (2) years after the
termination or cessation of such engagement for any reason, Consultant shall not
solicit, divert or take away, or attempt to divert or take away, the business or
patronage of any of the clients, customers or accounts, or prospective clients,
customers or accounts, of the Company which were contacted, solicited or served
by him while engaged by the Company; provided, that the scope of this provision
shall be limited to the business of developing or selling products or services
in the Field of Interest.

         10.      NON-SOLICITATION OF EMPLOYEES AND CONSULTANTS. Consultant
agrees that during his engagement by the Company and for a period of two (2)
years after the termination or cessation of such engagement for any reason,
Consultant shall not directly or indirectly (i) recruit, solicit or hire any
employee of the Company, or induce or attempt to induce any employee to
discontinue his or her employment relationship with the Company or (ii) without
the written consent of the Company, which shall not be unreasonably withheld,
solicit, recruit or hire any consultant then actively engaged by the Company to
perform services in the Field of Interest, or induce or attempt to induce such
consultant to terminate his or her consulting relationship with the Company.

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         11.      GENERAL.

                  11.1     The Company and Consultant agree that Consultant will
be an independent contractor for all purposes, including but not limited to
payroll and tax purposes, and that Consultant shall not in any way represent
himself to be an employee, partner or joint venturer with or of the Company.

                  11.2     All notices hereunder shall be in writing and shall
be given to the other party at the address or facsimile number set forth below,
or at such other address or facsimile number as either may specify in writing to
the other. All notices shall be effective 5 calendar days after being deposited
in the United States mail with proper postage affixed for first class registered
or certified mail, return receipt requested, or when delivered personally or
dispatched by facsimile, addressed:

                  If to the Company:         Mimeon, Inc.
                                             Bay Colony Corporate Center
                                             1000 Winter Street, Suite 3350
                                             Waltham, MA 02154
                                             Attention: Ganesh Venkataraman
                                             Telephone: 781.290.0770
                                             Facsimile: 781.290.0880

                  If to Consultant:          Ram Sasisekharan
                                             2130 Massachusetts Ave, 7B
                                             Cambridge, MA 02139
                                             Telephone: 617.258.9494
                                             Facsimile: 617.258.9409

                  11.3     This Agreement may not be assigned by either party
except that the Company may assign this Agreement in connection with the sale of
all or substantially all of the Company's assets to a publicly-held company or
the acquisition of the Company by a publicly-held company by means of merger,
consolidation or stock purchase. This Agreement shall be binding upon and shall
inure to the benefit of the parties hereto and their respective successors and
other legal representatives and, to the extent that any assignment hereof is
permitted hereunder, their assignees.

                  11.4     This Agreement supersedes all prior agreements,
written or oral, with respect to the subject matter of this Agreement. This
Agreement may be changed only by a written instrument signed by both parties
hereto.

                  11.5     In the event that any one or more of the provisions
contained herein shall, for any reason, be held to be invalid, illegal, or
unenforceable in any respect, such invalidity, illegality, or unenforceability
shall not affect any other provisions of this Agreement, and all other
provisions shall remain in full force and effect. If any of the provisions of
this Agreement is held to be excessively broad, it shall be reformed and
construed by limiting and reducing it so as to be enforceable to the maximum
extent permitted by law.

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                  11.6     No delay or omission by the Company in exercising any
right under this Agreement will operate as a waiver of that or any other right.
A waiver or consent given by the Company on any occasion is effective only in
that instance and will not be construed as a bar to or waiver of any right on
any other occasion.

                  11.7     Consultant acknowledges that the restrictions
contained in this Agreement are necessary for the protection of the business and
goodwill of the Company and are reasonable for such purpose. Consultant agrees
that any breach of this Agreement by him will cause irreparable damage to the
Company and that in the event of such breach, the Company shall be entitled, in
addition to monetary damages and to any other remedies available to the Company
under this Agreement and at law, to equitable relief, including injunctive
relief, and to payment by Consultant of all costs incurred by the Company in
enforcing of the provisions of this Agreement, including reasonable attorneys'
fees. Consultant agrees that should Consultant violate any obligation imposed on
him in this Agreement, Consultant shall continue to be bound by the obligation
until a period equal to the term of such obligation has expired without
violation of such obligation.

                  11.8     This Agreement shall be governed by, and construed
and enforced in accordance with, the substantive laws of the Commonwealth of
Massachusetts without regard to its principles of conflicts of laws. Any action,
suit or other legal proceeding which Consultant may commence to resolve any
matter arising under or relating to any provision of this Agreement shall be
commenced only in a court of the Commonwealth of Massachusetts (or, if
appropriate, a federal court located within Massachusetts), and Consultant
hereby consents to the jurisdiction of such court with respect to any action,
suit or proceeding commenced in such court by the Company.

         CONSULTANT HAS READ ALL OF THE PROVISIONS OF THIS AGREEMENT AND
CONSULTANT UNDERSTANDS, AND AGREES TO, EACH OF SUCH PROVISIONS.

         CONSULTANT UNDERSTANDS THAT THIS AGREEMENT MAY AFFECT HIS RIGHT TO
ACCEPT EMPLOYMENT WITH OR PERFORM SERVICES ON BEHALF OF OTHER COMPANIES DURING
AND AFTER THE PERIOD OF HIS ENGAGEMENT BY THE COMPANY.

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         IN WITNESS WHEREOF, the parties hereto have executed this Consulting
Agreement as a contract under seal as of the date first written above.

                                        MIMEON, INC.

                                        By:  /s/ Ganesh Venkataraman
                                           --------------------------------
                                           Ganesh Venkataraman
                                           President

                                         /s/ Ram Ssisekharan
                                        -----------------------------------
                                        Ram Sasisekharan

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                             [Letterhead of MOMENTA]

August 1, 2003

Dr.  Ram Sasisekharan
2130 Massachusetts Avenue, 7B
Cambridge, Massachusetts 02139

Dear Ram:

Reference is made to the Consulting Agreement dated August 16, 2001 between
Momenta Pharmaceuticals, Inc. (formerly Mimeon, Inc.) and you (the "Agreement").
Capitalized terms used herein and not otherwise defined shall have the meanings
given such terms in the Agreement.

Pursuant to Section 1 of the Agreement, Company and Consultant hereby agree to
extend the term of the Agreement for one additional year, from August 16, 2003
through August 15, 2004, upon the same terms and conditions, including, without
limitation, those governing compensation, as are set forth in the Agreement.

Consultant hereby represents that Consultant has not been debarred, and to the
best of Consultant's knowledge, is not under consideration to be debarred, by
the Food and Drug Administration from working in or providing services to any
pharmaceutical or biotechnology company under the Generic Drug Enforcement Act
of 1992.

Sincerely,

/s/ Alan L. Crane

Alan L. Crane
Chief Executive Officer

Agreed and accepted:

  /s/ Ram Sasisekharan
-----------------------------
Dr. Ram Sasisekharan<Page>

                                                                   EXHIBIT 10.20

                       RESTRICTED STOCK PURCHASE AGREEMENT
                               (Ram Sasisekharan)

         This Restricted Stock Purchase Agreement dated as of June 13, 2001
(this "Agreement") is made by and between Mimeon, Inc., a Delaware corporation
(the "Company"), and Ram Sasisekharan (the "Purchaser").

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

                  QUALIFIED OFFERING: A firm commitment underwritten public
offering of the Company's Common Stock pursuant to an effective registration
statement under the Securities Act of 1933, as amended (the "Act"), in which the
price per share is at least $5.00 (subject to equitable adjustment in the event
of stock splits and the like) and the aggregate gross proceeds to the Company
from such offering are not less than $10,000,000.

                  QUALIFIED SALE: The sale of all or substantially all of assets
or issued and outstanding capital stock of the Company, or merger or
consolidation involving the Company in which stockholders of the Company
immediately before such merger or consolidation do not own immediately after
such merger or consolidation capital stock or other equity interests of
surviving corporation or entity representing more than fifty percent in voting
power of capital stock or other equity interests of such surviving corporation
or entity outstanding immediately after such merger or consolidation.

                  SERVICE:  Service as an employee, officer or director of, or a
consultant or advisor the Company or its successors.

                  SHARES: The shares of Common Stock issued to Purchaser
hereunder and any other securities of the Company which may be issued in
exchange for or in respect of such shares of Common Stock, whether by way of
stock split, stock dividend, combination of shares, reclassification,
recapitalization, reorganization or any other means.

                  UNVESTED SHARES: Any Shares that are not Vested Shares.

                  VESTED: Released from the Company's Repurchase Option (as
defined in Section 5(a)).

                  VESTED SHARES: Any Shares that have vested in accordance with
Section 5(b).

         2.       PURCHASE AND SALE OF SHARES. The Company hereby sells to
Purchaser, and Purchaser hereby purchases from the Company, 809,800 shares of
the Company's common stock, $0.0001 par value per, share ("Common Stock"), for a
purchase price per share of $0.0001, and an aggregate purchase price of $80.98.
The Company acknowledges receipt from Purchaser of $80.98 in cash, in full
payment of such purchase price. Purchaser and the Company hereby agree that the
fair market value of the Shares on the date hereof is $0.0001 per share.

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         3.       REPRESENTATIONS OF PURCHASER.  Purchaser understands that the
Shares are not registered under the Act, and represents to the Company, and
agrees that the Company is entitled to rely on such representations, as follows:

                  (a)      Purchaser understands that the Shares have not been
registered under the Act, or registered or qualified under the securities or
"Blue Sky" laws of any jurisdiction, and are being sold pursuant to exemptions
contained in the Act and exemptions contained in other applicable securities or
"Blue Sky" laws. Purchaser understands further that the Company's reliance on
these exemptions is based in part on the representations made by Purchaser in
the Agreement. In this connection, Purchaser represents and warrants that the
offer and sale of the Shares were made solely in Massachusetts.

                  (b)      Purchaser understands the term "accredited investor"
as used in Regulation D promulgated under the Act and represents and warrants to
the Company that he is an "accredited investor" for purposes of acquiring the
Shares. The nature and amount of Purchaser's investment in the Shares is
consistent with Purchaser's investment objectives, abilities, and resources.
Purchaser understands that the Shares are an illiquid investment, which will not
become freely transferable by reason of any "change of circumstances" whatever.
Purchaser has adequate means of providing for Purchaser's current needs and
possible contingencies and has no need for liquidity in Purchaser's investment.

                  (c)      Purchaser is acquiring the Shares for Purchaser's own
account for investment, and not for, with a view to, or in connection with the
resale or distribution thereof. Purchaser has no present intention to sell,
hypothecate, distribute or otherwise transfer the Shares or any portion thereof
or any interest therein.

                  (d)      Purchaser understands that the Shares will constitute
"restricted securities" thin-the meaning of Rule 144 promulgated under the Act
and that, as such, the Shares must be held indefinitely unless they are
subsequently registered under the Act or unless an exemption from the
registration requirements thereof is available. Purchaser has been advised that
Rule 144, which permits the resale, subject to various terms and conditions, of
small amounts of such "restricted securities" after they have been held for one
year, does not now apply to the Company, because the Company is not now required
to file, and does not file, current reports under the Securities Exchange Act of
1934, and because information concerning the Company substantially equivalent to
that which would be available if the Company were required to file such reports
is not now publicly available. The Company may become a reporting entity at some
future date, but no assurance can be given that it will do so.

                  (e)      In connection with Purchaser's acquisition of the
Shares, Purchaser accepts the condition that the Company may maintain "stop
transfer" orders with respect to the Shares and that each certificate or other
document evidencing the Shares will bear conspicuous legends in substantially
the form set forth in Section 7 of this Agreement.

                  (f)      Purchaser has consulted Purchaser's attorney or
accountant with respect to Purchaser's purchase of the Shares. Purchaser has
fully investigated the Company and its business and financial condition and has
knowledge of the Company's current activities. Purchaser acknowledges that the
Company has granted Purchaser and Purchaser's attorney or

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accountant access to all information about the Company which they have requested
and has offered each of them access to all further information which they deemed
relevant to an investment decision with respect to the Shares. Purchaser and
Purchaser's attorney or accountant have had the opportunity to ask questions of,
and receive answers from, representatives of the Company concerning such
information and the Company's financial condition and prospects.

         4.       RESTRICTIONS ON TRANSFER.  The following restrictions on
transfer of the Shares shall apply:

                  (a)      SECURITIES LAWS. Except for purchases of Unvested
Shares by the Company as contemplated by Section 5, no Shares, nor any interest
therein, may be sold, assigned, pledged or otherwise transferred at any time or
under any circumstances unless (i) the Shares proposed to be transferred have
been registered under the Act and qualified under applicable state securities
laws, or (ii) the Company has received, or agreed to waive, an opinion of
counsel acceptable to the Company to the effect that such transfer may be
effected without registration under the Act or qualification under the
securities laws of relevant states and the proposed transferee has made such
representations and agreements as the Company shall require to assure compliance
with the Act and such laws.

                  (b)      TERMINATION OF REPURCHASE OPTION. Except for
purchases of Unvested Shares by the Company as contemplated by Section 5, no
Shares, nor any interest therein, may be sold, assigned, pledged or otherwise
transferred until the Repurchase Option shall have terminated with respect to
such Shares.

                  (c)      RIGHT OF FIRST OFFER. In the event that at any time
Purchaser desires to sell, assign or otherwise transfer any of the Vested Shares
then held by Purchaser, he shall first offer the Vested Shares desired to be
transferred to the Company by giving written notice of the proposed transfer.
The notice shall state the number of Vested Shares proposed to be transferred,
the name of the person or persons to whom it is proposed to transfer the Vested
Shares, the price at which the Vested Shares are intended to be transferred and
all other terms of the transaction, which must be bona fide. Such notice shall
constitute an offer by Purchaser to the Company for the Company to purchase such
Vested Shares on such terms and at a price per Vested Share equal to the price
stated in the notice. The Company may accept the offer as to all, but not less
than all, of the Vested Shares offered by notifying Purchaser in writing within
30 days after receipt of such notice of its acceptance of the offer. If the
offer is accepted, Purchaser shall sell the offered Vested Shares to the Company
on the terms and at the price per Vested Share as aforesaid, free of all
encumbrances, and shall deliver the certificates representing such Vested
Shares, duly endorsed in blank by Purchaser or with duly executed stock powers
attached thereto, all in form suitable for the transfer of such Vested Shares to
the Company, within 30 days of the date of acceptance of the offer to sell,
against payment therefor at the same price per Vested Share and according to the
same terms as were offered by the proposed transferee. If within the applicable
time period Purchaser does not receive notice of the Company's intention to
purchase the offered Vested Shares, the offer shall be deemed to have been
rejected. In such event, Purchaser may transfer title to the offered Vested
Shares within 90 days from the date of his written notice to the Company of his
intention to sell, but such transfer shall be made only to the proposed
transferee or transferees and at the proposed price and on such other terms as
stated

                                        3
<Page>

in such notice. Vested Shares that are so transferred to such transferee or
transferees shall remain subject to this Section 3 and as a condition to any
transfer Purchaser shall obtain a written agreement from the transferee by which
the transferee agrees to be bound by this Section 3.

                  (d)      PERMITTED TRANSFERS. Any portion or all of the Vested
Shares may, without compliance with the provisions of Section 4(c), be
transferred by Purchaser to a member of his immediate family or to a family
partnership or family trust, or on Purchaser's death may be transferred to
Purchaser's estate or to those entitled to a distribution of the Vested Shares
under the laws of descent and distribution, provided that Shares that are so
transferred shall remain subject to this Section 4 and as a condition to any
transfer Purchaser shall obtain a written agreement from the transferee by which
the transferee agrees to be bound by this Section 4.

                  (e)      REMEDIES. No sale, assignment, pledge or other
transfer of Shares shall be effective or given effect on the books of the
Company unless all of the applicable provisions of this Section 4 have been duly
complied with. If any transfer of Shares is made or attempted in violation of
the foregoing restrictions, or if Shares are not offered to the Company as
required hereby, the Company shall have the right to purchase such Shares from
the purported owner thereof or his transferee at any time before or after the
transfer, as herein provided. In addition to any other legal or equitable
remedies which it may have, the Company may enforce its rights by actions for
specific performance (to the extent permitted by law) and may refuse to
recognize any transferee as one of its stockholders for any purpose, including,
without limitation, for purposes of dividend and voting rights, until all
applicable provisions hereof have been complied with.

                  (f)      LOCK-UP. Purchaser agrees that for a period of up to
180 days from the effective date of any registration of securities of the
Company (upon request of the, Company or the underwriters managing any
underwritten offering of the Company's securities), he will not sell make any
short sale or loan of, grant any option for the purchase of, or otherwise
dispose of any Shares held by him without the prior written consent of the
Company or such underwriters, as the case may be.

                  (g)      TERMINATION OF RESTRICTIONS.  Sections 4(c) and 4(d)
shall terminate upon the earlier to occur of: (i) immediately prior to the
consummation of a Qualified Sale; or (ii) the closing of a Qualified Offering.

         5.       REPURCHASE OF UNVESTED SHARES.

                  (a)      REPURCHASE OPTION.

                           (i)      In the event of the termination of
Purchaser's Service by Purchaser or the Company for any reason, with or without
cause, the Company shall upon the date of such termination (the "Termination
Date") have an irrevocable, exclusive option (the "Repurchase Option") for a
period of 90 days from such date to repurchase all or any portion of the
Unvested Shares at the per share repurchase price of $0.0001 per share,
appropriately adjusted in the event of a stock dividend, stock split,
recapitalization, combination of shares or similar event occurring subsequent to
the date of this Agreement.

                                        4
<Page>

                           (ii)     Unless the Company notifies Purchaser within
90 days from the date of termination of Purchaser's Service that it does not
intend to exercise its Repurchase Option with respect to some or all of the
Unvested Shares, the Repurchase Option shall be deemed automatically exercised
by the Company as of the 90th day following such termination, provided that the
Company may notify Purchaser that it is exercising its Repurchase Option as of a
date prior to such 90th day. Unless Purchaser is otherwise notified by the
Company pursuant to the preceding sentence that the Company does not intend to
exercise its Repurchase Option as to some or all of the Unvested Shares to which
it applies at the time of termination, execution of this Agreement by Purchaser
constitutes written notice to Purchaser of the Company's intention to exercise
its Repurchase Option with respect to all Unvested Shares to which such
Repurchase Option applies. The Company, at its choice, may satisfy its payment
obligation to Purchaser with respect to exercise of the Repurchase Option by
either (A) delivering a check to Purchaser in the amount of the purchase price
for the Unvested Shares being repurchased, or (B) in the event Purchaser is
indebted to the Company, canceling an amount of such indebtedness equal to the
purchase price for the Unvested Shares being repurchased, or (C) by a
combination of (A) and (B) so that the combined payment and cancellation of
indebtedness equals such purchase price, provided that the Company shall use
good faith efforts to satisfy its payment obligation to Purchaser within 15 days
after Company's notice of exercise of the Repurchase Option (or deemed
exercise), and that if such check is not delivered or such cancellation is not
effective within such 15 days from such date, the amount of the Company's
unsatisfied payment obligation shall bear interest at a rate of nine percent
(9%) per annum until the Company has satisfied its payment obligation under this
paragraph (ii). In the event of any deemed automatic exercise of the Repurchase
Option pursuant to this Section 5(a)(ii) and Purchaser is then indebted to the
Company, the amount of such indebtedness equal to the purchase price of the
Unvested Shares being repurchased shall be deemed automatically canceled as of
the date of Company's notice of exercise of the Repurchase Option (or deemed
exercise). As a result of any repurchase of Unvested Shares pursuant to this
Section 5(a), the Company shall become the legal and beneficial owner of the
Unvested Shares being repurchased and shall have all rights and interest therein
or related thereto, and the Company shall have the right to transfer to its own
name the number of Unvested Shares being repurchased by the Company, without
further action by Purchaser.

                  (b)      VESTING.

                           (i)      The Shares will become vested as follows:

                                    (A)      one sixteenth (1/16) of the Shares
shall vest on September 13, 2001; and

                                    (B)      an additional one sixteenth (1/16)
of the Shares shall vest on the last day of each consecutive three-month period
thereafter until 100% of the Shares have become vested; PROVIDED, however, that
the vesting of Shares on any such vesting date shall be conditioned upon
Purchaser's continuing Service with the Company from the date hereof through
such vesting date. Fractional shares shall be rounded down to the nearest whole
share.

                                        5
<Page>

                           (ii)     Notwithstanding Section 4(b)(i), all Shares
shall be deemed to have vested immediately prior to the consummation of a
Qualified Sale.

         6.       CUSTODY OF CERTIFICATES. In order to facilitate the exercise
of the Repurchase Option, the Company or its counsel shall hold all certificates
representing Unvested Shares, together with an adequate number of undated and
otherwise blank stock powers executed by Purchaser. The Company shall have the
right to cause transfers of Unvested Shares to be effected pursuant to Section
5. After any Shares become Vested Shares, the Company shall, on request of
Purchaser, deliver to Purchaser a certificate or certificates representing such
vested Shares. After the Company sends Purchaser a notice that it does not
intend to exercise its Repurchase Option as to certain Unvested Shares, the
Company shall, upon request of Purchaser, deliver to Purchaser a certificate or
certificates representing such Unvested Shares.

         7.       LEGENDS.  Each certificate representing Shares shall
prominently bear legends in substantially the following forms:

         These securities have not been registered under the Securities Act of
         1933. They may not be sold, offered for sale, pledged or hypothecated
         in the absence of a registration statement in effect with respect to
         the securities under such Act or an opinion of counsel satisfactory to
         the Corporation that such registration is not required.

         The securities represented by this certificate have been acquired for
         investment and have not been registered or qualified under the
         securities or "Blue Sky" laws of any jurisdiction. They may not be
         offered or sold without an opinion of counsel to the Corporation to the
         effect that the proposed transaction will be exempt from registration,
         qualification, and filings in all applicable jurisdictions.

         The Corporation is authorized to issue more than one class or series of
         stock. The powers, designations, preferences and relative
         participating, optional or other special rights, and the
         qualifications, limitations or restrictions of such preferences and/or
         rights of each class of stock or series of any class set forth in the
         Certificate of Incorporation of the Corporation. The Corporation will
         furnish a copy of the Certificate of Incorporation of the Corporation
         to the holder of this certificate without charge upon request.

         The securities represented by this certificate are subject to
         restrictions on transfer and repurchase rights pursuant to the terms of
         a Restricted Stock Purchase Agreement, as amended from time to time,
         between the owner of this certificate and the Corporation. The
         Corporation will finish a copy of this agreement to the holder hereof
         without charge upon written request.

         8.       MISCELLANEOUS.

                                        6
<Page>

                  (a)      ENTIRE AGREEMENT. This Agreement constitutes the
entire agreement between the parties with respect to the subject matter hereof
and supersedes all prior agreements, negotiations, representations and
proposals, written or oral, relating to such subject matter.

                  (b)      AMENDMENTS.  Neither this Agreement nor any provision
hereof may be changed or modified except by an agreement in writing executed by
Purchaser and on behalf of the Company.

                  (c)      BINDING EFFECT OF THE AGREEMENT. This Agreement shall
inure to the benefit of, and be binding upon, the Company, Purchaser and their
respective estates, heirs, executors, transferees, successors, assigns and legal
representatives.

                  (d)      PROVISIONS SEVERABLE. In the event that any provision
of this Agreement shall be determined to be invalid, illegal or otherwise
unenforceable by any court of competent jurisdiction, the validity, legality and
enforceability of the other provisions of this Agreement shall not be affected
thereby. Any invalid, illegal or unenforceable provision of this Agreement shall
be severed, and after any such severance, all other provisions hereof shall
remain in full force and effect.

                  (e)      NOTICES. All notices under this Agreement shall be
effective (i) upon personal or facsimile delivery, (ii) two business days after
deposit in the United States mail as registered or certified mail postage fully
prepaid, or (iii) one business day after pickup by any overnight commercial
courier service, in each case sent or addressed to the Company at its principal
office and to Purchaser at his record address as carried in the stock records of
the Company or at such other address as he may from time to time designate in
writing to the Company.

                  (f)      CONSTRUCTION. A reference to a Section shall mean a
Section of this Agreement unless otherwise expressly stated. The titles and
headings herein are for reference purposes only and shall not in any manner
limit the construction of this Agreement which shall be considered as a whole.
The words "include," "includes" and "including" when used herein shall be deemed
in each case to be followed by the words "without limitation." Whenever the
context may require, any pronouns used herein shall include the corresponding
masculine, feminine or neuter forms, and the singular form of names and pronouns
shall include the plural and vice-versa.

                  (g)      NO EMPLOYMENT AGREEMENT.  This Agreement shall not be
construed as an agreement by the Company to employ Purchaser, nor is the Company
obligated to employ Purchaser by reason of this Agreement or the issuance of the
Shares to Purchaser.

                  (h)      SECTION 83(b) ELECTION. Purchaser will furnish to the
Company a copy of any election made by Purchaser under Section 83(b) of the
Internal Revenue Code of 1986, as amended, with respect to his acquisition of
the Shares.

                  (i)      APPLICABLE LAW. This Agreement shall be construed and
enforced in accordance with the laws of The Commonwealth of Massachusetts,
without regard to its Principles of conflicts of laws. Purchaser consents to
jurisdiction and venue in any state or

                                        7
<Page>

federal court in The Commonwealth of Massachusetts for the purposes of any
action relating to or arising out of this Agreement or any breach or alleged
breach hereof, and to service of process in any such action by certified or
registered mail, return receipt requested.

                  (j)      DISPOSITION OF SHARES; PURCHASE BY NOMINEE OR
DESIGNEE. Any Shares that the Company elects to purchase hereunder may be
disposed of by it in such manner as it deems appropriate with or without
restrictions on the transfer thereof, and the Company may require their transfer
to a nominee or designee as part of any purchase of the Shares from Purchaser.

                  (k)      WITHHOLDING TAXES. Purchaser acknowledges and agrees
that the Company has the right to deduct from payments of any kind otherwise due
to Purchaser any federal, state or local taxes of any kind required by law to be
withheld with respect to the purchase of the Shares by Purchaser.

         IN WITNESS WHEREOF, the parties hereto have executed this Restricted
Stock Purchase Agreement as of the date first above written.

                                        MIMEON, INC.

                                        By:   /s/ Ganesh Venkataraman
                                           -------------------------------------
                                        Name:
                                        Title:

                                              /s/ Ram Sasiekharan
                                        ----------------------------------------
                                        Ram Sasisekharan

                                        8

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