Document:

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[LETTERHEAD OF THE DAVIS COMPANIES]

August 23, 2001

Mr. Avery W. Catlin
Senior Vice President and
Chief Financial Officer                               Via Fax and Certified Mail
AVANT Immunotherapeutics, Inc.
119 Fourth Avenue
Needham, MA 02494-2725

Re:  Lease at 115-119 Fourth Avenue, Needham, MA

Dear Chip:

With reference to the Lease of space at 115 Fourth Avenue, Needham, MA dated May
1, 1996 between AVANT Immunotherapeutics, Inc. (formerly known as T Cell
Sciences, Inc.), as Lessee, and DIV Needham 53 LLC as successor in interest to
Fourth Avenue Ventures Limited Partnership, as Lessor: In accordance with
Section 1.1 and Section 4.2 of the Lease, Tenant has timely exercised its option
to extend the term of the Lease for an additional five years, from May 1, 2002
through April 30, 2007 (the "Extension Term").

In accordance with Section 4.3 of the Lease, Landlord and Tenant hereby agree
and confirm the Annual Fixed Rent for the Extension Term in accordance with
Section 4.2 of the Lease shall be as follows:

     May 1, 2002 - April 30, 2003@ net rent of $27.00/SF or $1,466,559.00 per
     year.
     May 1, 2003 - April 30, 2004@ net rent of $27.00/SF or $1,466,559.00 per
     year.
     May 1, 2004 --April 30, 2005@ net rent of $27.50/SF or $1,493,717.50 per
     year.
     May 1, 2005 -April 30, 2006@ net rent of $28.00/SF or $1,520,876.00 per
     year.
     May 1, 2006 - April 30, 2007@ net rent of $28.75/SF or $1,561,613.75 per
     year.

All other terms and conditions of the Lease shall remain unchanged and in full
force and effect. Please sign below and return a copy of this letter to me, and
this letter will serve as our Confirmation of the Extension Term Rent.

I am glad we were able to come to agreement, and look forward to working with
you during your continued tenancy. If you have any questions, or I can be of any
assistance, please do not hesitate to call me.

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Sincerely, '
DIV NEEDHAM 115 LLC
By: Davis Management Corp., Its Managing Agent

/s/ Amy B. Klein
----------------
By:  Amy E. Klein
Its: Senior Vice President

Agreed to and accepted by AVANT Immunotherapeutics, Inc.

By:   /s/  Avery W. Catlin, its: Senior VP & CFO
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                                 Duly authorized<Page>

                Confidential Treatment Requested As To Certain
                     Information Contained In This Exhibit

                           EXCLUSIVE LICENSE AGREEMENT

     This Agreement, effective October 10, 2001 (the "Effective Date"), is
between AVANT Immunotherapeutics, Inc. ("AVANT"), a Delaware corporation, and
DynPort Vaccine Company LLC ("DVC"), a Virginia Limited Liability Company.

                                 R E C I T A L S

     WHEREAS, AVANT has expertise in the expression, purification, and
characterization of the BACILLUS ANTHRACIS bacterial protein Protective Antigen
("PA") from ESCHERICHIA COLI ("E COLI");

     WHEREAS, AVANT owns materials, information and documents for the
manufacture of clinical grade recombinant PA (expressed from E COLI) in
accordance with Good Manufacturing Practices ("cGMP");

     WHEREAS, AVANT owns information and documents relating to preclinical
development of recombinant PA (expressed from E COLI);

     WHEREAS, AVANT owns a United States patent application titled "Improved
Vaccination Against Anthrax"; and

     WHEREAS, DVC desires to obtain and AVANT is willing to grant to DVC a
license to AVANT's PA technology in the field of prophylactic anthrax vaccines.

     NOW, THEREFORE, AVANT and DVC hereby agree as follows:

1. DEFINITIONS.

     1.1. "AFFILIATE" means any legal entity (such as a corporation,
partnership, or limited liability company) that is controlled by AVANT or by
DVC. For the purposes of this definition, the term "control" means (i)
beneficial ownership of at least fifty percent (50%) of the voting securities of
a corporation or other business organization with voting securities or (ii) a
fifty percent (50%) or greater interest in the net assets or profits of a
partnership or other business organization without voting securities.

     1.2. "BIOLOGICAL MATERIALS" means certain tangible biological materials
owned or licensed by AVANT, which materials are described in EXHIBIT A, as well
as tangible materials that are routinely produced through use of the original
materials, including, for example, any progeny derived from a cell line,
monoclonal antibodies produced by hybridoma cells, DNA or RNA replicated from
isolated DNA or RNA, recombinant proteins produced through use of isolated DNA
or RNA, and substances routinely purified from a source material included in the
original materials (such as recombinant proteins isolated from a cell extract or
supernatant by non-proprietary affinity purification methods). These Biological
Materials shall be listed in EXHIBIT A, which will be periodically amended to
include any additional Biological Materials that AVANT may furnish to DVC.

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     1.3. "COMBINATION PRODUCT" means a product that contains a Licensed Product
component and at least one other essential functional component. For example, a
combination vaccine for prevention of anthrax and a second disease would be a
Combination Product.

     1.4. "CONFIDENTIAL INFORMATION" means any confidential or proprietary
information furnished by one party (the "Disclosing Party") to the other party
(the "Receiving Party") in connection with this Agreement, provided that such
information is specifically designated as confidential. Such Confidential
Information shall include, without limitation, any diligence reports furnished
to AVANT under Section 3.1. and royalty reports furnished to AVANT under Section
5.2.

     1.5. "FIELD" means human prophylactic vaccines for prevention of anthrax.

     1.6. "LICENSED PRODUCT" means any product that cannot be developed,
manufactured, used, or sold without (i) infringing one or more claims under the
Patent Rights, (ii) using or incorporating some portion of one or more
Biological Materials, or (iii) using some portion of the Related Technology.
This Section 1.6. is not intended to preclude DVC from using industry standard
practices in the development of anthrax vaccines or other vaccine products, nor
to require payment to AVANT for such uses. The parties acknowledge that DVC is
working on a parallel development effort with PA expressed from BACILLUS
ANTHRACIS. Nothing in this agreement abridges DVC's rights to pursue that
development.

     1.7. "MINIMUM ROYALTY PERIOD" means the one-year period commencing on the
earliest of the January 1, April 1, July 1 or October 1 following the date of
NDA or BLA approval of a Licensed Product, and each one-year period thereafter
during the term of this Agreement.

     1.8. "NET SALES" means the gross amount received on sales by DVC and its
Affiliates and Sublicensees of Licensed Products, less the following: (i)
customary trade, quantity, or cash discounts and commissions to non-affiliated
brokers or agents to the extent actually allowed and taken; and (ii) amounts
repaid or credited by reason of rejection or return; (iii) to the extent
separately stated on purchase orders, invoices, or other documents of sale, any
taxes or other governmental charges levied on the production, sale,
transportation, delivery, or use of a Licensed Product which is paid by or on
behalf of DVC; and (iv) outbound transportation costs prepaid or allowed and
costs of insurance in transit.

     In any transfers of Licensed Products between DVC and an Affiliate or
Sublicensee, Net Sales shall be calculated based on the final sale of the
Licensed Product to an independent third party. In the event that DVC or an
Affiliate or Sublicensee receives non-monetary consideration for any Licensed
Products, Net Sales shall be calculated based on the fair market value of such
consideration. In the event that DVC or its Affiliates or Sublicensees use or
dispose of a Licensed Product in the provision of a commercial service, the
Licensed Product shall be considered sold and the Net Sales shall be calculated
based on the sales price of the Licensed Product to an independent third party
during the same Royalty Period or, in the absence of such sales, on the fair
market value of the Licensed Product as determined by the parties in good faith.

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     In the case of Combination Products, Net Sales means the gross amount
billed or invoiced on sales of the Combination Product less the deductions set
forth above, multiplied by a proration factor that is determined as follows:

          (i) If all components of the Combination Product were sold separately
     during the same or immediately preceding Royalty Period, the proration
     factor shall be determined by the formula [A / (A+B)], where A is the
     aggregate gross sales price of all Licensed Product components during such
     period when sold separately from the other essential functional components,
     and B is the aggregate gross sales price of the other essential functional
     components during such period when sold separately from the Licensed
     Product Components; or

          (ii) If all components of the Combination Product were not sold
     separately during the same or immediately preceding Royalty Period, the
     proration factor shall be determined by the formula [C / (C+D)], where C is
     the aggregate fully absorbed cost of the Licensed Product components during
     the prior Royalty Period and D is the aggregate fully absorbed cost of the
     other essential functional components during the prior Royalty Period, with
     such costs being determined in accordance with generally accepted
     accounting principles.

     1.9. "PATENT RIGHTS" means the U.S. patent applications listed on EXHIBIT
A, and any divisional, continuation, or continuation-in-part of such patent
applications to the extent the claims are directed to subject matter
specifically described therein, as well as any patent issued thereon and any
reissue or reexamination of such patent, and any foreign counterparts to such
patents and patent applications. EXHIBIT A shall be periodically amended to
include any additional Patent Rights that may arise. "AVANT PATENT RIGHTS" means
Patent Rights assigned solely to AVANT. "JOINT PATENT Rights" means Patent
Rights assigned to both AVANT and DVC.

     1.10. "RELATED TECHNOLOGY" means any know-how, technical information,
research and development information, test results, and data related to PA which
has been developed by AVANT as of the Effective Date and which is owned by
AVANT.

     1.11. "ROYALTY PERIOD" means the partial calendar quarter commencing on the
date on which the first Licensed Product is sold or used and every complete or
partial calendar quarter thereafter during which either (i) this Agreement
remains in effect or (ii) DVC has the right to complete and sell
work-in-progress and inventory of Licensed Products pursuant to Section 8.5.

     1.12. "SUBLICENSE INCOME" means any payments that DVC receives from a
Sublicensee in consideration of the sublicense of the rights granted DVC under
Section 2.1., including without limitation license fees, royalties, milestone
payments, and license maintenance fees, but excluding the following payments:
(i) payments made in consideration for the issuance of equity or debt securities
of DVC at fair market value, and (ii) payments specifically committed to the
development of Licensed Products.

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     1.13. "SUBLICENSEE" means any permitted sublicensee of the rights granted
DVC under this Agreement, as further described in Section 2.2.

2. GRANT OF RIGHTS.

     2.1. LICENSE GRANTS.

          (a) PATENT RIGHTS AND BIOLOGICAL MATERIALS. Subject to the terms of
this Agreement, AVANT hereby grants to DVC and its Affiliates an exclusive,
worldwide, royalty-bearing license (with the right to sublicense) under its
rights in the Patent Rights and Biological Materials to develop, make, have
made, use, and sell Licensed Products in the Field.

          (b) RELATED TECHNOLOGY. Subject to the terms of this Agreement, AVANT
hereby grants to DVC and its Affiliates a non-exclusive, royalty-bearing license
(with the right to sublicense) under its rights in the Related Technology to
develop, make, have made, use, and sell Licensed Products in the Field.

     2.2. SUBLICENSES. DVC shall have the right to grant sublicenses of its
rights under Section 2.1. with the consent of AVANT, which consent shall not be
unreasonably withheld or delayed. All sublicense agreements executed by DVC
pursuant to this Article 2 shall expressly bind the Sublicensee to the terms of
this Agreement and shall provide for the automatic assignment of such agreement
to AVANT if this Agreement is terminated as described in Article 8 below. DVC
shall promptly furnish AVANT with a fully executed copy of any such sublicense
agreement.

     2.3. RETAINED RIGHTS.

          (a) AVANT. AVANT retains the right to make and use Licensed Products
for research, teaching, and non-commercial patient care, without payment of
compensation to DVC. AVANT may license its retained rights under this Section to
academic research collaborators of AVANT. AVANT's retained rights for research
specifically exclude clinical research in the Field.

          (b) FEDERAL GOVERNMENT. To the extent that any invention claimed in
the Patent Rights has been partially funded by the United States federal
government, this Agreement and the grant of any rights in such Patent Rights are
subject to and governed by federal law as set forth in 35 U.S.C. Sections
201-211, and the regulations promulgated thereunder, as amended, or any
successor statutes or regulations. The parties acknowledge that these statutes
and regulations reserve to the federal government a royalty-free, non-exclusive,
non-transferrable license to practice any government-funded invention claimed in
any Patent Rights. If any term of this Agreement fails to conform with such laws
and regulations, the relevant term shall be deemed an invalid provision and
modified in accordance with Section 10.11.

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3. DVC OBLIGATIONS RELATING TO COMMERCIALIZATION.

     3.1. DILIGENCE REQUIREMENTS. DVC shall use diligent efforts, or shall cause
its Affiliates and Sublicensees to use diligent efforts, to develop Licensed
Products and to introduce Licensed Products into the commercial market;
thereafter, DVC or its Affiliates or Sublicensees shall make Licensed Products
reasonably available to the public. Specifically, DVC or Affiliate or
Sublicensee shall fulfill the following obligations:

          (1) Within thirty (30) days after the Effective Date, DVC shall
     furnish AVANT with a written research and development plan under which DVC
     intends to develop Licensed Products. Due to the sensitive nature of the
     underlying federal program, this report shall be a top level overview only
     of the development plan.

          (2) Within sixty (60) days after each anniversary of the Effective
     Date, DVC shall furnish AVANT with a written report on the progress of its
     efforts during the prior year to develop and commercialize Licensed
     Products, including without limitation research and development efforts,
     efforts to obtain regulatory approval, marketing efforts, and sales
     figures. The report shall also contain a discussion of intended efforts and
     sales projections for the current year. Due to the sensitive nature of the
     underlying federal program, this report shall be a top level overview only
     of the development progress.

          (3) No later than ***Confidential Treatment Requested as to this
     Information*** DVC shall initiate a clinical trial of a Licensed Product.

In the event that AVANT determines that DVC (or an Affiliate or Sublicensee) has
not fulfilled its obligations under this Section 3.1., AVANT shall furnish DVC
with written notice of such determination. Within sixty (60) days after receipt
of such notice, DVC shall either (i) fulfill the relevant obligation or (ii)
negotiate with AVANT a mutually acceptable schedule of revised diligence
obligations, failing which AVANT shall have the right, immediately upon written
notice to DVC, to grant additional licenses to third parties to the Patent
Rights and Biological Materials in the Field.

     3.2. INDEMNIFICATION.

          (a) INDEMNITY. DVC shall indemnify, defend, and hold harmless AVANT
and its directors, officers, employees, and agents and their respective
successors, heirs and assigns (the "Indemnitees"), against any liability,
damage, loss, or expense (including reasonable attorneys fees and expenses of
litigation) incurred by or imposed upon any of the Indemnitees in connection
with any claims, suits, actions, demands or judgments arising out of any theory
of liability (including without limitation actions in the form of tort,
warranty, or strict liability and regardless of whether such action has any
factual basis) concerning any product, process, or service that is made, used,
or sold pursuant to any right or license granted under this Agreement; provided,
however, that such indemnification shall not apply to any liability, damage,
loss, or expense to the extent directly attributable to (i) the negligent
activities or intentional misconduct of the Indemnitees or (ii) the settlement
of a claim, suit, action, or demand by Indemnitees without the prior written
approval of DVC.

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          (b) PROCEDURES. The Indemnitees agree to provide DVC with prompt
written notice of any claim, suit, action, demand, or judgment for which
indemnification is sought under this Agreement. DVC agrees, at its own expense,
to provide attorneys reasonably acceptable to AVANT to defend against any such
claim. The Indemnitees shall cooperate fully with DVC in such defense and will
permit DVC to conduct and control such defense and the disposition of such
claim, suit, or action (including all decisions relative to litigation, appeal,
and settlement); provided, however, that any Indemnitee shall have the right to
retain its own counsel, at the expense of DVC, if representation of such
Indemnitee by the counsel retained by DVC would be inappropriate because of
actual or potential differences in the interests of such Indemnitee and any
other party represented by such counsel. DVC agrees to keep AVANT informed of
the progress in the defense and disposition of such claim and to consult with
AVANT with regard to any proposed settlement.

          (c) INSURANCE. DVC shall maintain insurance that is reasonably
adequate to fulfill any potential obligation to the Indemnitees, but in any
event not less than one million dollars ($1,000,000) for injuries to any one
person arising out of a single occurrence and five million dollars ($5,000,000)
for injuries to all persons arising out of a single occurrence. DVC shall
provide AVANT, upon request, with written evidence of such insurance. DVC shall
continue to maintain such insurance after the expiration or termination of this
Agreement during any period in which DVC or any Affiliate or Sublicensee
continues to make, use, or sell a product that was a Licensed Product under this
Agreement, and thereafter for a period of five (5) years.

     3.3. USE OF AVANT NAME. In accordance with Section 7.3., DVC and its
Affiliates and Sublicensees shall not use the name "AVANT Immunotherapeutics,
Inc." or any variation of that name in connection with the marketing or sale of
any Licensed Products without the prior written consent of AVANT.

     3.4. MARKING OF LICENSED PRODUCTS. To the extent commercially feasible and
consistent with prevailing business practices, DVC shall mark, and shall cause
its Affiliates and Sublicensees to mark, all Licensed Products that are
manufactured or sold under this Agreement with the number of each issued patent
under the Patent Rights that applies to such Licensed Product.

     3.5. COMPLIANCE WITH LAW. DVC shall comply with, and shall ensure that its
Affiliates and Sublicensees comply with, all local, state, federal, and
international laws and regulations relating to the development, manufacture,
use, and sale of Licensed Products. DVC expressly agrees to comply with the
following:

          (i) DVC or its Affiliates or Sublicensees shall obtain all necessary
     approvals from the United States Food & Drug Administration and any similar
     governmental authorities of any foreign jurisdiction in which DVC or an
     Affiliate or Sublicensee intends to make, use, or sell Licensed Products.

          (ii) DVC and its Affiliates and Sublicensees shall comply with all
     United States laws and regulations controlling the export of certain
     commodities and technical data,

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     including without limitation all Export Administration Regulations of the
     United States Department of Commerce. Among other things, these laws and
     regulations prohibit, or require a license for, the export of certain types
     of commodities and technical data to specified countries. DVC hereby gives
     written assurance that it will comply with, and will cause its Affiliates
     and Sublicensees to comply with, all United States export control laws and
     regulations, that it bears sole responsibility for any violation of such
     laws and regulations by itself or its Affiliates or Sublicensees, and that
     it will indemnify, defend, and hold AVANT harmless (in accordance with
     Section 3.2.) for the consequences of any such violation.

          (iii) To the extent that any invention claimed in the Patent Rights
     has been partially funded by the United States government, and only to the
     extent required by applicable laws and regulations, DVC agrees that any
     Licensed Products used or sold in the United States will be manufactured
     substantially in the United States or its territories. Current law provides
     that if domestic manufacture is not commercially feasible under the
     circumstances, AVANT may seek a waiver of this requirement from the
     relevant federal agency on behalf of DVC.

4. CONSIDERATION FOR GRANT OF RIGHTS.

          4.1. MATERIALS FEE. DVC shall pay AVANT on the Effective Date a
payment of ***Confidential Treatment Requested as to this Information***
AVANT for its expenses incurred in connection with developing and
manufacturing cGMP PA. This payment is nonrefundable and is not creditable
against any other payments due to AVANT under this Agreement.

          4.2. LICENSE MAINTENANCE FEES. DVC shall pay AVANT on the Effective
Date a license maintenance fee of ***Confidential Treatment Requested as to
this Information***. On January 1, 2003, and on January 1 of each year
thereafter during the term of this Agreement, DVC shall pay AVANT an annual
license maintenance fee of ***Confidential Treatment Requested as to this
Information***. These license maintenance fees are nonrefundable and are not
creditable against any other payments due to AVANT under this Agreement.

          4.3. MILESTONE PAYMENTS. DVC shall pay AVANT the following milestone
payments within thirty (30) days after the occurrence of each event:

***Confidential Treatment Requested as to this Information***

These milestone payments are nonrefundable and are not creditable against any
other payments due to AVANT under this Agreement.

         4.4. ROYALTIES.

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          (a) BASE ROYALTY. In partial consideration of the rights granted
DVC under this Agreement, DVC shall pay AVANT a royalty of (i)
***Confidential Treatment Requested as to this Information*** of Licensed
Products sold to the United States federal government by DVC and its
Affiliates (but not Sublicensees) and (ii) ***Confidential Treatment
Requested as to this Information*** of Licensed Products sold to any buyer
other than the United States federal government by DVC and its Affiliates
(but not Sublicensees).

          (b) ROYALTY REDUCTION. If AVANT grants additional licenses to third
parties pursuant to Section 3.1., the royalty rates set forth in Subsection
4.5.(a) shall be adjusted, if necessary, so as not to exceed the royalty rates
charged any other licensee of the Patent Rights during the term of the
non-exclusive license.

     4.5. MINIMUM ROYALTY. Within sixty (60) days after the end of each
Minimum Royalty Period, if the actual royalty is less than ***Confidential
Treatment Requested as to this Information*** for the Minimum Royalty Period,
DVC shall pay AVANT a minimum royalty payment of ***Confidential Treatment
Requested as to this Information*** less any actual royalties paid by DVC to
AVANT for the Minimum Royalty Period.

     4.6. SUBLICENSE INCOME. DVC shall pay AVANT a total of ***Confidential
Treatment Requested as to this Information*** of all Sublicense Income.
Except for royalty-based payments, such amounts shall be due and payable
within sixty (60) days after DVC receives the relevant payment from the
Sublicensee; royalty-based payments of Sublicense Income shall be due and
payable as provided in Article 5 below.

5. ROYALTY REPORTS; PAYMENTS; RECORDS.

     5.1. FIRST SALE. DVC shall report to AVANT the date of first commercial
sale of each Licensed Product within thirty (30) days of occurrence in each
country.

     5.2. REPORTS AND PAYMENTS. Within sixty (60) days after the conclusion of
each Royalty Period, DVC shall deliver to AVANT a report containing the
following information:

          (i) the number of doses of Licensed Products sold to the United States
     federal government, and the number of doses of Licensed Products used by
     DVC and its Affiliates in the provision of services to the United States
     federal government;

          (ii) the number of doses of Licensed Products sold to independent
     third parties other than the United States federal government in each
     country, and the number of doses of Licensed Products used by DVC and its
     Affiliates in the provision of services to such parties in each country;

          (iii) calculation of total royalty payable; and

          (iv) the portion of royalty-based Sublicense Income due to AVANT for
     the applicable Royalty Period from each Sublicensee.

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All such reports shall be considered DVC Confidential Information. If no
royalties are due to AVANT for any Royalty Period, the report shall so state.
Concurrent with this report, DVC shall remit to AVANT any payment due for the
applicable Royalty Period.

     5.3. PAYMENTS IN U.S. DOLLARS. All payments due under this Agreement shall
be payable in United States dollars. Conversion of foreign currency to U.S.
dollars shall be made at the conversion rate existing in the United States (as
reported in the WALL STREET JOURNAL) on the last working day of the calendar
quarter preceding the applicable Royalty Period. Such payments shall be without
deduction of exchange, collection, or other charges.

     5.4. PAYMENTS IN OTHER CURRENCIES. If by law, regulation, or fiscal policy
of a particular country, conversion into United States dollars or transfer of
funds of a convertible currency to the United States is restricted or forbidden,
DVC shall give AVANT prompt written notice of such restriction, which notice
shall satisfy the sixty-day payment deadline described in Section 5.2. DVC shall
pay any amounts due AVANT through whatever lawful methods AVANT reasonably
designates; provided, however, that if AVANT fails to designate such payment
method within thirty (30) days after AVANT is notified of the restriction, DVC
may deposit such payment in local currency to the credit of AVANT in a
recognized banking institution selected by DVC and identified by written notice
to AVANT, and such deposit shall fulfill all obligations of DVC to AVANT with
respect to such payment.

     5.5. RECORDS. DVC shall maintain, and shall cause its Affiliates and
Sublicensees to maintain, complete and accurate records of Licensed Products
that are made, used, or sold, under this Agreement and any amounts payable to
AVANT in relation to such Licensed Products, which records shall contain
sufficient information to permit AVANT to confirm the accuracy of any reports
delivered to AVANT under Section 5.2. The relevant party shall retain such
records relating to a given Royalty Period for at least three (3) years after
the conclusion of that Royalty Period, during which time AVANT shall have the
right, at its expense, to cause its internal accountants or an independent,
certified public accountant to inspect such records during normal business hours
for the sole purpose of verifying any reports and payments delivered under this
Agreement. Such accountant shall not disclose to AVANT any information other
than information relating to accuracy of reports and payments delivered under
this Agreement. The parties shall reconcile any underpayment or overpayment
within thirty (30) days after the accountant delivers the results of the audit.
In the event that any audit performed under this Section reveals an underpayment
in excess of five percent (5%) in any Royalty Period, DVC shall bear the full
cost of such audit. AVANT may exercise its rights under this Section only once
every year and only with reasonable prior notice to DVC.

     5.6. LATE PAYMENTS. Any payments by DVC that are not paid on or before the
date such payments are due under this Agreement shall bear interest, to the
extent permitted by law, at two percentage points above the Prime Rate of
interest as reported in the WALL STREET JOURNAL on the date payment is due, with
interest calculated based on the number of days that payment is delinquent.

     5.7. METHOD OF PAYMENT. All payments under this Agreement should be made in
the name of the "AVANT Immunotherapeutics, Inc." and sent to the address
identified below. Each

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payment should reference this Agreement and identify the obligation under this
Agreement that the payment satisfies.

     5.8. WITHHOLDING AND SIMILAR TAXES. Royalty payments and other payments due
to AVANT under this Agreement shall not be reduced by reason of any withholding
or similar taxes applicable to such payments to AVANT.

6. PATENTS AND INFRINGEMENT.

     6.1. RESPONSIBILITY FOR AVANT PATENT RIGHTS. AVANT shall have primary
responsibility for the preparation, filing, prosecution, and maintenance of all
AVANT Patent Rights, using patent counsel reasonably acceptable to DVC. DVC
shall reimburse AVANT for all reasonable patent-related expenses incurred by
AVANT in accordance with Section 6.4. below. AVANT shall consult with DVC as to
the preparation, filing, prosecution, and maintenance of all such Patent Rights
reasonably prior to any deadline or action with the U.S. Patent & Trademark
Office or any foreign patent office and shall furnish DVC with copies of all
relevant documents reasonably in advance of such consultation.

     6.2. RESPONSIBILITY FOR JOINT PATENT RIGHTS. DVC shall have primary
responsibility, at its expense, for the preparation, filing, prosecution, and
maintenance of all Joint Patent Rights, using patent counsel reasonably
acceptable to AVANT. DVC shall consult with AVANT as to the preparation, filing,
prosecution, and maintenance of all such Patent Rights reasonably prior to any
deadline or action with the U.S. Patent & Trademark Office or any foreign patent
office and shall furnish AVANT with copies of all relevant documents reasonably
in advance of such consultation.

     6.3. COOPERATION. AVANT and DVC shall cooperate fully in the preparation,
filing, prosecution, and maintenance of all Patent Rights. Such cooperation
includes, without limitation, (i) promptly executing all papers and instruments
or requiring employees of AVANT or DVC to execute such papers and instruments as
reasonable and appropriate so as to enable AVANT or DVC to file, prosecute, and
maintain such Patent Rights in any country; and (ii) promptly informing the
other party of matters that may affect the preparation, filing, prosecution, or
maintenance of any such Patent Rights (such as becoming aware of an additional
inventor who is not listed as an inventor in a patent application).

     6.4. PAYMENT OF EXPENSES. Within thirty (30) days after AVANT invoices
DVC, DVC shall reimburse AVANT for all reasonable patent-related expenses
incurred by AVANT pursuant to Section 6.1., up to a maximum of
***Confidential Treatment Requested as to this Information*** for United
States patent expenses. In the event AVANT incurs patent expenses in excess
of ***Confidential Treatment Requested as to this Information*** incurs
foreign patent expenses, AVANT shall notify DVC, and DVC shall in turn notify
AVANT as to whether DVC shall reimburse AVANT for such expenses. DVC may
elect, upon sixty (60) days written notice to AVANT, to cease payment of the
expenses associated with obtaining or maintaining patent protection for one
or more Patent Rights in one or more countries. In such event, DVC's rights
under this Agreement with respect to such Patent Rights in such countries
shall become non-exclusive.

                                      -10-
<Page>

     6.5. ABANDONMENT. In the event that a party desires to abandon any patent
or patent application within the Patent Rights for which it has primary
responsibility, such party shall provide the other party with reasonable prior
written notice of such intended abandonment or decline of responsibility, and
the other party shall have the right, at its expense, to prepare, file,
prosecute, and maintain the relevant Patent Rights.

     6.6. INFRINGEMENT.

          (a) NOTIFICATION OF INFRINGEMENT. Each party agrees to provide written
notice to the other party promptly after becoming aware of any infringement of
the Patent Rights.

          (b) DVC RIGHT TO PROSECUTE. So long as DVC remains the only licensee
of the Patent Rights and Biological Materials in the Field, DVC shall have the
right, under its own control and at its own expense, to prosecute any third
party infringement of the Patent Rights in the Field. Prior to commencing any
such action, DVC shall consult with AVANT and shall consider the views of AVANT
regarding the advisability of the proposed action and its effect on the public
interest. DVC shall not enter into any settlement, consent judgment, or other
voluntary final disposition of any infringement action under this Subsection
without the prior written consent of AVANT, which consent shall not be
unreasonably withheld or delayed. Any recovery obtained in an action under this
Subsection shall be distributed as follows: (i) each party shall be reimbursed
for any expenses incurred in the action, and (ii) as to damages, DVC shall
receive seventy five percent (75%) and AVANT shall receive twenty five percent
(25%).

          (c) AVANT RIGHT TO PROSECUTE. In the event that DVC fails to initiate
an infringement action within a reasonable time after it first becomes aware of
the basis for such action, or to answer a declaratory judgment action within a
reasonable time after such action is filed, AVANT shall have the right to
prosecute such infringement or answer such declaratory judgment action, under
its sole control and at its sole expense, and any recovery obtained shall be
given to AVANT.

          (d) COOPERATION. Each party agrees to cooperate fully in any action
under this Section 6.6. which is controlled by the other party, provided that
the controlling party reimburses the cooperating party promptly for any costs
and expenses incurred by the cooperating party in connection with providing such
assistance.

7.  CONFIDENTIAL INFORMATION; PUBLICATIONS; PUBLICITY.

     7.1. CONFIDENTIAL INFORMATION.

          (a) DESIGNATION. Confidential Information that is disclosed in writing
shall be marked with a legend indicating its confidential status (such as
"Confidential" or "Proprietary"). Confidential Information that is disclosed
orally or visually shall be documented in a written notice prepared by the
Disclosing Party and delivered to the Receiving Party within thirty (30) days of
the date of disclosure; such notice shall summarize the Confidential Information
disclosed to the Receiving Party and reference the time and place of disclosure.

                                      -11-
<Page>

          (b) OBLIGATIONS. For a period of five (5) years after disclosure of
any portion of Confidential Information, the Receiving Party shall (i) maintain
such Confidential Information in strict confidence, except that the Receiving
Party may disclose or permit the disclosure of any Confidential Information to
its directors, officers, employees, consultants, and advisors who are obligated
to maintain the confidential nature of such Confidential Information and who
need to know such Confidential Information for the purposes of this Agreement;
(ii) use such Confidential Information solely for the purposes of this
Agreement; and (iii) allow its directors, officers, employees, consultants, and
advisors to reproduce the Confidential Information only to the extent necessary
for the purposes of this Agreement, with all such reproductions being considered
Confidential Information.

          (c) EXCEPTIONS. The obligations of the Receiving Party under
Subsection 7.1.(b) above shall not apply to the extent that the Receiving Party
can demonstrate that certain Confidential Information (i) was in the public
domain prior to the time of its disclosure under this Agreement; (ii) entered
the public domain after the time of its disclosure under this Agreement through
means other than an unauthorized disclosure resulting from an act or omission by
the Receiving Party; (iii) was independently developed or discovered by the
Receiving Party without use of the Confidential Information; (iv) is or was
disclosed to the Receiving Party at any time, whether prior to or after the time
of its disclosure under this Agreement, by a third party having no fiduciary
relationship with the Disclosing Party and having no obligation of
confidentiality with respect to such Confidential Information; or (v) is
required to be disclosed to comply with applicable laws or regulations, or with
a court or administrative order, provided that the Disclosing Party receives
reasonable prior written notice of such disclosure and the Receiving Party
cooperates in legal efforts to limit such disclosure.

          (d) OWNERSHIP AND RETURN. The Receiving Party acknowledges that the
Disclosing Party (or any third party entrusting its own information to the
Disclosing Party) claims ownership of its Confidential Information in the
possession of the Receiving Party. Upon the expiration or termination of this
Agreement, and at the request of the Disclosing Party, the Receiving Party shall
return to the Disclosing Party all originals, copies, and summaries of
documents, materials, and other tangible manifestations of Confidential
Information in the possession or control of the Receiving Party, except that the
Receiving Party may retain one copy of the Confidential Information in the
possession of its legal counsel solely for the purpose of monitoring its
obligations under this Agreement.

     7.2. PUBLICATIONS. AVANT and its employees will be free to publicly
disclose (through journals, lectures, or otherwise) the results of any research
in the Field or relating to the subject matter of the Patent Rights.

     7.3. PUBLICITY RESTRICTIONS. DVC shall not use the name of AVANT or any of
its directors, officers, employees, or agents, or any adaptation of such names,
or any terms of this Agreement in any promotional material or other public
announcement or disclosure without the prior written consent of AVANT. The
foregoing notwithstanding, DVC shall have the right to disclose such information
without the consent of AVANT in any prospectus, offering memorandum, or other
document or filing required by applicable securities laws or other applicable
law or regulation, provided that DVC shall have given AVANT at least ten (10)
days

                                      -12-
<Page>

prior written notice of the proposed text for the purpose of giving AVANT the
opportunity to comment on such text.

8.  TERM AND TERMINATION.

     8.1. TERM. This Agreement shall commence on the Effective Date and shall
remain in effect until (i) the expiration of all issued patents within the
Patent Rights or (ii) for a period of twenty (20) years after the Effective Date
if no such patents have issued within that twenty-year period, unless earlier
terminated in accordance with the provisions of this Agreement.

     8.2. VOLUNTARY TERMINATION BY DVC. DVC shall have the right to terminate
this Agreement, for any reason, upon ninety (90) days prior written notice to
AVANT. In the event that DVC terminates this Agreement under this Section 8.2.,
DVC shall (i) return all rights under this Agreement to AVANT; (ii) give AVANT
manufacturing materials and manufacturing, regulatory and clinical documents and
information relating to Licensed Products, along with rights, without further
obligation to DVC, for AVANT to use such materials, documents and information
for development, manufacture, use and sale of anthrax vaccines; and (iii) pay
AVANT any license maintenance fees and any milestone payments due to AVANT under
Sections 4.2. and 4.3. of this Agreement.

     8.3. TERMINATION FOR DEFAULT. In the event that either party commits a
material breach of its obligations under this Agreement and fails to cure that
breach within sixty (60) days after receiving written notice thereof, the other
party may initiate executive discussions regarding resolution of the breach. If
these good-faith discussions fail to yield a resolution of the breach within
another sixty (60) day period, the other party may terminate this Agreement upon
written notice to the party in breach.

     8.4. FORCE MAJEURE. Neither party will be responsible for delays resulting
from causes beyond the reasonable control of such party, including without
limitation fire, explosion, flood, war, strike, or riot, provided that the
nonperforming party uses commercially reasonable efforts to avoid or remove such
causes of nonperformance and continues performance under this Agreement with
reasonable dispatch whenever such causes are removed.

     8.5. EFFECT OF TERMINATION. The following provisions shall survive the
expiration or termination of this Agreement: Articles 1 and 9; Sections 3.2.,
3.5., 5.2. (obligation to provide final report and payment), 5.5., 6.4., 7.1.,
7.3., 8.5., and 10.9. Upon the early termination of this Agreement, DVC and its
Affiliates and Sublicensees may complete and sell any work-in-progress and
inventory of Licensed Products that exist as of the effective date of
termination, provided that (i) DVC is current in payment of all amounts due
AVANT under this Agreement, (ii) DVC pays AVANT the applicable royalty on such
sales of Licensed Products in accordance with the terms and conditions of this
Agreement, and (iii) DVC and its Affiliates and Sublicensees shall complete and
sell all work-in-progress and inventory of Licensed Products within six (6)
months after the effective date of termination. Upon the early termination of
this Agreement, except to the extent necessary to fulfill the provisions of the
preceding sentence, DVC and its Affiliates and Sublicensees shall stop using all
Biological Materials and return all Biological Materials to AVANT.

                                      -13-
<Page>

9.  DISPUTE RESOLUTION.

     9.1. PROCEDURES MANDATORY. The parties agree that any dispute arising out
of or relating to this Agreement shall be resolved solely by means of the
procedures set forth in this Article, and that such procedures constitute
legally binding obligations that are an essential provision of this Agreement;
provided, however, that all procedures and deadlines specified in this Article
may be modified by written agreement of the parties. If either party fails to
observe the procedures of this Article, as modified by their written agreement,
the other party may bring an action for specific performance in any court of
competent jurisdiction.

     9.2. DISPUTE RESOLUTION PROCEDURES.

          (a) NEGOTIATION. In the event of any dispute arising out of or
relating to this Agreement, the affected party shall notify the other party, and
the parties shall attempt in good faith to resolve the matter within ten (10)
days after the date of such notice (the "Notice Date"). Any disputes not
resolved by good faith discussions shall be referred to senior executives of
each party, who shall meet at a mutually acceptable time and location within
thirty (30) days after the Notice Date and attempt to negotiate a settlement.

          (b) MEDIATION. If the matter remains unresolved within sixty (60) days
after the Notice Date, or if the senior executives fail to meet within thirty
(30) days after the Notice Date, either party may initiate mediation upon
written notice to the other party, whereupon both parties shall be obligated to
engage in a mediation proceeding under the then current Center for Public
Resources ("CPR") Model Procedure for Mediation of Business Disputes, except
that specific provisions of this Section shall override inconsistent provisions
of the CPR Model Procedure. The mediator will be selected from the CPR Panels of
Neutrals. If the parties cannot agree upon the selection of a mediator within
ninety (90) days after the Notice Date, then upon the request of either party,
the CPR shall appoint the mediator. The parties shall attempt to resolve the
dispute through mediation until one of the following occurs: (i) the parties
reach a written settlement; (ii) the mediator notifies the parties in writing
that they have reached an impasse; (iii) the parties agree in writing that they
have reached an impasse; or (iv) the parties have not reached a settlement
within one hundred and twenty (120) days after the Notice Date.

          (c) TRIAL WITHOUT JURY. If the parties fail to resolve the dispute
through mediation, or if neither party elects to initiate mediation, each party
shall have the right to pursue any other remedies legally available to resolve
the dispute, provided, however, that the parties expressly waive any right to a
jury trial in any legal proceeding under this Section.

     9.3. PRESERVATION OF RIGHTS PENDING RESOLUTION.

          (a) PERFORMANCE TO CONTINUE. Each party shall continue to perform its
obligations under this Agreement pending final resolution of any dispute arising
out or relating to this Agreement; provided, however, that a party may suspend
performance of its obligations during any period in which the other party fails
or refuses to perform its obligations.

                                      -14-
<Page>

          (b) PROVISIONAL REMEDIES. Although the procedures specified in this
Article are the sole and exclusive procedures for the resolution of disputes
arising out of relating to this Agreement, either party may seek a preliminary
injunction or other provisional equitable relief if, in its reasonable judgment,
such action is necessary to avoid irreparable harm to itself or to preserve its
rights under this Agreement.

          (c) STATUTE OF LIMITATIONS. The parties agree that all applicable
statutes of limitation and time-based defenses (such as estoppel and laches)
shall be tolled while the procedures set forth in Subsections 9.2.(a) and 9.2(b)
are pending. The parties shall take any actions necessary to effectuate this
result.

10. MISCELLANEOUS.

     10.1. REPRESENTATIONS AND WARRANTIES. AVANT represents and warrants that
its employees have assigned to AVANT their entire right, title, and interest in
the Patent Rights and that it has authority to grant the rights and licenses set
forth in this Agreement. AVANT MAKES NO OTHER WARRANTIES CONCERNING THE PATENT
RIGHTS, RELATED TECHNOLOGY, AND BIOLOGICAL MATERIALS, INCLUDING WITHOUT
LIMITATION ANY EXPRESS OR IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. Specifically, AVANT makes no warranty or representation (i)
regarding the validity or scope of the Patent Rights, (ii) that the exploitation
the Patent Rights or any Licensed Product will not infringe any patents or other
intellectual property rights of a third party, and (iii) that any third party is
not currently infringing or will not infringe the Patent Rights.

     10.2. COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, and all of which
together shall be deemed to be one and the same instrument.

     10.3. HEADINGS. All headings are for convenience only and shall not affect
the meaning of any provision of this Agreement.

     10.4. BINDING EFFECT. This Agreement shall be binding upon and inure to the
benefit of the parties and their respective permitted successors and assigns.

     10.5. ASSIGNMENT. This Agreement may not be assigned by either party
without the prior written consent of the other party, except that either party
may assign this Agreement to an Affiliate or to a successor in connection with
the merger, consolidation, or sale of all or substantially all of its assets or
that portion of its business to which this Agreement relates.

     10.6. AMENDMENT AND WAIVER. This Agreement may be amended, supplemented, or
otherwise modified only by means of a written instrument signed by both parties.
Any waiver of any rights or failure to act in a specific instance shall relate
only to such instance and shall not be construed as an agreement to waive any
rights or fail to act in any other instance, whether or not similar.

                                      -15-
<Page>

     10.7. GOVERNING LAW. This Agreement shall be governed by and construed in
accordance with the laws of the State of Delaware irrespective of any conflicts
of law principles.

     10.8. NOTICE. Any notices required or permitted under this Agreement shall
be in writing, shall specifically refer to this Agreement, and shall be sent by
hand, recognized national overnight courier, confirmed facsimile transmission,
confirmed electronic mail, or registered or certified mail, postage prepaid,
return receipt requested, to the following addresses or facsimile numbers of the
parties:

     If to AVANT:

     Una S. Ryan, Ph.D.
     President and CEO
     AVANT Immunotherapeutics, Inc.
     119 Fourth Avenue
     Needham, MA 02494

     Tel: (781) 433-0771
     Fax: (781) 433-0262

                                      -16-
<Page>

     If to DVC:

     Scott Stewart
     Senior Director of Contracts
     DynPort Vaccine Company LLC
     60 Thomas Johnson Drive
     Frederick, MD 21702

     Tel: (301) 607-5000
     Fax: (301) 607-5099

All notices under this Agreement shall be deemed effective upon receipt. A party
may change its contact information immediately upon written notice to the other
party in the manner provided in this Section.

     10.11. SEVERABILITY. In the event that any provision of this Agreement
shall be held invalid or unenforceable for any reason, such invalidity or
unenforceability shall not affect any other provision of this Agreement, and the
parties shall negotiate in good faith to modify the Agreement to preserve (to
the extent possible) their original intent. If the parties fail to reach a
modified agreement within sixty (60) days after the relevant provision is held
invalid or unenforceable, then the dispute shall be resolved in accordance with
the procedures set forth in Article 9. While the dispute is pending resolution,
this Agreement shall be construed as if such provision were deleted by agreement
of the parties.

     10.12. ENTIRE AGREEMENT. This Agreement constitutes the entire agreement
between the parties with respect to its subject matter and supersedes all prior
agreements or understandings between the parties relating to its subject matter.

     IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
by their duly authorized representatives as of the date first written above.

AVANT IMMUNOTHERAPEUTICS, INC.             DYNPORT VACCINE COMPANY LLC

By: /s/ Una S. Ryan                        By: /s/ Scott K. Stewart
    -----------------------------              --------------------------------
Name:   Una S. Ryan, Ph.D.                 Name:   Scott K. Stewart
Title:  President and CEO                  Title:  Senior Director of Contracts

                                      -17-
<Page>

                                    EXHIBIT A

                 LIST OF PATENT RIGHTS AND BIOLOGICAL MATERIALS

PATENT RIGHTS

***Confidential Treatment Requested as to this Information***

BIOLOGICAL MATERIALS

***Confidential Treatment Requested as to this Information***

                                      -18-

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