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                                                                   EXHIBIT 10.22

                                        CONFIDENTIAL MATERIALS OMITTED AND
                                        FILED SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

                                LICENSE AGREEMENT

     This License Agreement (this "AGREEMENT"), effective as of October 16, 2002
(the "EFFECTIVE DATE"), is entered into by and between XOMA Ireland Limited, a
company with limited liability organized under the laws of the Republic of
Ireland having offices at Shannon Airport House, Shannon, County Clare, Ireland
(with its Affiliates, "XOMA"), and DYAX Corp., a corporation organized under the
laws of the State of Delaware having offices at 300 Technology Square,
Cambridge, Massachusetts 02139, U.S.A. (with its Affiliates, "DYAX").

                                   BACKGROUND

     A.      XOMA is the owner or exclusive licensee of certain patent rights
and know-how relating to bacterial cell expression, and DYAX wishes to acquire
non-exclusive licenses under such patent rights and know-how; and

     B.      XOMA is willing to grant DYAX non-exclusive licenses, on the terms
and conditions set forth below, in order to permit DYAX to engage in certain
research, development and commercial activities; and

     C.      DYAX is the owner or exclusive licensee of certain patent rights
relating to phage display technologies (generally known as the Ladner and
related patent rights), and XOMA wishes to acquire non-exclusive licenses under
such patent rights; and

     D.      DYAX is willing to grant XOMA non-exclusive licenses, on the terms
and conditions set forth below, in order to permit XOMA to engage in certain
research, development and commercial activities.

     NOW, THEREFORE, in consideration of the promises and the mutual covenants
hereinafter recited, the parties agree as follows:

                                    ARTICLE 1

                                   DEFINITIONS

     In this Agreement, the following terms shall have the meanings set forth in
this Article.

     1.1     "AFFILIATE" means any corporation or other entity which is directly
or indirectly controlling, controlled by or under common control with a party
hereto. For purposes of this Agreement, "CONTROL" (including, with correlative
meanings, the terms "CONTROLLED" and "CONTROLLING") means the possession,
directly or indirectly, of the power to direct or cause the direction of the
management or policies of the subject corporation or other entity, whether

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through the ownership of voting securities, by agreement or otherwise.

     1.2     "ANTIBODY PHAGE DISPLAY" means the authorized use of Licensed
Antibody Phage Display Materials to conduct Research and Development.

     1.3     "CHANGE IN CONTROL" means, with respect to DYAX Corp. or XOMA Ltd.,
any transaction or series of transactions as a result of which any person or
group (as defined under the U.S. Securities Exchange Act of 1934, as amended)
becomes, directly or indirectly, the beneficial owner of more than fifty percent
(50%) of the total voting power of such entity's equity securities or otherwise
gains control of such entity.

     1.4     "COMMERCIAL ANTIBODY PHAGE DISPLAY BUSINESS" means, with respect to
immunoglobulin or antibody phage display services, immunoglobulin or antibody
phage display libraries, immunoglobulin or antibody phage display products or
immunoglobulin or antibody phage display materials, the out-licensing,
commercial manufacture, sale, offer for sale, import for sale or export for sale
of such immunoglobulin or antibody phage display services, libraries, products
and materials.

     1.5     "CONFIDENTIAL INFORMATION" means any proprietary or confidential
information or material disclosed by a party to the other party pursuant to this
Agreement, which is (i) disclosed in tangible form hereunder and is designated
thereon as "Confidential" at the time it is delivered to the receiving party, or
(ii) disclosed orally hereunder and identified as confidential or proprietary
when disclosed and such disclosure of confidential information is confirmed in
writing within thirty (30) days by the disclosing party.

     1.6     "DEVELOPMENT PARTNER" means a Third Party from whom a party either
in-licenses a target for development and/or commercialization by the
in-licensing party or with whom a party shares the economic risk of development
or commercialization of a target or product being developed or commercialized on
behalf of the applicable party.

     1.7     "DISPOSE" means to transfer, assign, lease, or in any other fashion
dispose of control, ownership or possession, but shall not mean to license or
sell. "DISPOSITION" shall have the correlative meaning.

     1.8     "DYAX COLLABORATOR" means any person or entity who is an authorized
end-user of Licensed Antibody Phage Display Materials, the intended recipient of
Licensed Immunoglobulins or Licensed Immunoglobulin Information transferred from
DYAX and/or a person or entity on whose behalf DYAX knowingly engages in
Antibody Phage Display; PROVIDED, HOWEVER, that such person or entity shall not
be deemed to be a DYAX Collaborator unless and until the requirements of
Section 2.5 are complied with. Except as expressly set

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forth on SCHEDULE 2.9(i), no person or entity shall be deemed to be a DYAX
Collaborator if such person or entity is engaged in a Commercial Antibody Phage
Display Business unless, pursuant to a written agreement (other than this
Agreement), executed after the Effective Date, XOMA has granted to such person
or entity a valid license or covenant not to sue under the XOMA Patent Rights
which explicitly extends to the activities identified in this third to last
sentence of Section 1.8. XOMA shall provide DYAX prompt written notice of those
written agreements or covenants not to sue which satisfy the requirements of the
prior sentence. No person or entity may claim the status of DYAX Collaborator
with respect to any acts or activities which are unrelated to the use of
Licensed Antibody Phage Display Materials provided by DYAX.

     1.9     "DYAX PATENT RIGHTS" means the patent applications and patents
listed on SCHEDULE 1.9 hereto and, solely to the extent any Valid Claim would
cover or be included in the license grants provided for herein, all divisions,
continuations, continuations-in-part, applications claiming priority thereto,
and substitutions thereof; all foreign patent applications corresponding to the
preceding applications; all U.S. and foreign patents issuing on any of the
preceding applications, including extensions, reissues and re-examinations; and
any other patent rights owned or licensed by DYAX, whether now existing or
obtained in the future, which DYAX has the right to license or sublicense and
which would be infringed by the activities of XOMA contemplated hereunder but
for this Agreement. DYAX Patent Rights shall also include (i) any improvements
of the foregoing that are owned or controlled by DYAX and (ii) any patents or
patent applications, whether now existing or obtained in the future, owned or
controlled by DYAX containing a claim that is dominating over the foregoing
patent rights (i.e., is necessarily infringed by the practicing of a claim in
one of the foregoing applications).

     1.10    "FIRST COMMERCIAL SALE" shall mean the initial transfer by DYAX
(either directly or through a Third Party, including without limitation any
joint venture or similar arrangement in which DYAX and/or a Development Partner
of DYAX is a participant) of a Product for value and not for demonstration,
testing or promotional purposes.

     1.11    "IMMUNOGLOBULIN" means any molecule, including without limitation,
full immunoglobulin molecules (e.g., IgG, IgM, IgE, IgA and IgD molecules) and
ScFv, Fv and Fab molecules, that has an amino acid sequence by virtue of which
it specifically interacts with an antigen and wherein that amino acid sequence
consists essentially of a functionally operating region of an antibody variable
region including, without limitation, any naturally occurring or recombinant
form of such a molecule.

     1.12    "LICENSED ANTIBODY PHAGE DISPLAY MATERIALS" means (i) any
collection or library of polynucleotide sequences, created by and under the
exclusive control of DYAX, which encodes at least one Immunoglobulin and which
is contained in filamentous bacteriophage and/or bacteriophage or phagemid
cloning vectors capable of propagation in bacteria; or

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(ii) any collection or library of bacteriophage, created by or under the
exclusive control of DYAX, wherein an Immunoglobulin is expressed as a fusion
protein comprising an Immunoglobulin or at least a functionally operating region
of an antibody variable region and an outer surface polypeptide of a
bacteriophage. For the avoidance of doubt, and without expanding the definition
thereof, specifically excluded from the definition of Licensed Antibody Phage
Display Materials are (x) any article of manufacture or composition of matter
suitable for display, expression or secretion of an Immunoglobulin in or from
any organism or system other than bacteria and (y) any materials or composition
of matter otherwise meeting the definition of Licensed Antibody Phage Display
Materials but created by or under the control of any entity, other than DYAX,
engaged in a Commercial Antibody Phage Display Business; PROVIDED, that,
notwithstanding the foregoing, any materials or composition of matter otherwise
meeting the definition of Licensed Antibody Phage Display Materials but created
by or under the exclusive control of a DYAX Collaborator shall constitute
Licensed Antibody Phage Display Materials, but only to the extent derived by
such DYAX Collaborator exclusively from Licensed Antibody Phage Display
Materials created by or under the exclusive control of DYAX and properly
transferred by DYAX to such DYAX Collaborator in accordance with the applicable
provisions of this Agreement and such DYAX Collaborator acknowledges that the
transfer restrictions and other provisions hereof apply thereto.

     1.13    "LICENSED IMMUNOGLOBULIN" means any Immunoglobulin discovered,
isolated or characterized by DYAX or a DYAX Collaborator (as defined above)
through the use of Licensed Antibody Phage Display Materials.

     1.14    "LICENSED IMMUNOGLOBULIN INFORMATION" means any data, know-how or
other information relating, concerning or pertaining to a Licensed
Immunoglobulin, including, without limitation, data, know-how or other
information characterizing or constituting such Licensed Immunoglobulin's
polynucleotide or amino acid sequence, purported function or utility, antigen
binding affinity, or physical or biochemical property.

     1.15    "NET SALES" means, solely with respect to sales by DYAX (either
directly or through a Third Party, including without limitation any joint
venture or similar arrangement in which DYAX and/or a Development Partner of
DYAX is a participant), the gross amount invoiced by DYAX (or such joint venture
or similar arrangement) to an independent Third Party less the following items:

     (a)     Trade, cash and quantity discounts actually allowed and taken
             directly with respect to such sales;

     (b)     Excises, sales taxes or other taxes imposed upon and paid directly
             with respect to such sales (excluding national, state or local
             taxes based income);

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     (c)     Amounts repaid or credited by reason of rejections, defects,
             recalls or returns or because of rebates or retroactive price
             reduction; and

     (d)     Freight, transportation and insurance.

Net Sales shall not include any consideration received by DYAX (or any such
joint venture or similar arrangement) in respect of the sale, use or other
disposition of such Product in a country as part of a clinical trial prior to
the receipt of all regulatory approvals required to commerce full commercial
sales of such Product in such country, except sales under "treatment INDs,"
"named patient sales," "compassionate use sales," or their equivalents pursuant
to which DYAX (or any such joint venture or similar arrangement) is entitled,
under applicable laws, regulations and regulatory policies, to recover costs
incurred in providing such Product to patients.

     1.16    "PRODUCT" means any composition of matter or article of
manufacture, including without limitation any diagnostic, prophylactic or
therapeutic product, which (a) contains a Licensed Immunoglobulin; or (b) was
discovered or created by, arose out of or is related to use of Licensed Antibody
Phage Display Materials or the conduct of Antibody Phage Display by DYAX or a
DYAX Collaborator; or (c) is sold by or on behalf of DYAX or a DYAX Collaborator
under conditions which, if unlicensed, would constitute infringement of the XOMA
Patent Rights.

     1.17    "RESEARCH AND DEVELOPMENT" means the identification, selection,
isolation, purification, characterization, study and/or testing of an
Immunoglobulin for any purpose, including, without limitation, the discovery and
development of human therapeutics or diagnostics. Included within the definition
of "Research and Development" shall be all IN VITRO screening or assays
customarily performed in pre-clinical and clinical research and uses associated
with obtaining FDA or equivalent agency regulatory approval. "Research and
Development" shall not include commercial or industrial manufacture or any
activities solely directed to the creation of such capacities.

     1.18    "RESEARCH QUANTITIES" means those quantities of an Immunoglobulin
reasonably required for Research and Development purposes.

     1.19    "THIRD PARTY" means any person or entity other than DYAX or XOMA.

     1.20    "VALID CLAIM" means (i) a claim of an issued and unexpired patent
included within the DYAX Patent Rights or the XOMA Patent Rights, as the case
may be, which has not been held invalid in a final decision of a court of
competent jurisdiction from which no appeal may be taken, and which has not been
disclaimed or admitted to be invalid or unenforceable through reissue or
otherwise, or (ii) a claim of a pending patent application

                                       -5-
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within the DYAX Patent Rights or the XOMA Patent Rights, as the case may be.

     1.21    "XOMA FIELD OF USE" means all fields except for IN VIVO diagnostics
for so long as the license granted by DYAX to Bracco Holding, B.V. and Bracco
International, B.V. for IN VIVO diagnostics remains exclusive.

     1.22    "XOMA KNOW-HOW" means unpatented and/or unpatentable technical
information, including ideas, concepts, inventions, discoveries, data, designs,
formulas, specifications, procedures for experiments and tests and other
protocols, results of experimentation and testing, fermentation and purification
techniques, and assay protocols, whether now existing or obtained in the future,
owned by XOMA which XOMA has the right to license or sublicense and which may be
necessary for the practice of the XOMA Patent Rights or which would be
misappropriated by the activities of DYAX or the DYAX Collaborators contemplated
hereunder but for this Agreement. XOMA Know-How shall not include the XOMA
Patent Rights. All XOMA Know-How shall be confidential information of XOMA.

     1.23    "XOMA PATENT RIGHTS" means the patent applications and patents
listed on SCHEDULE 1.23 hereto and, solely to the extent any Valid Claim would
cover or be included in the license grants provided for herein, all divisions,
continuations, continuations-in-part, applications claiming priority thereto,
and substitutions thereof; all foreign patent applications corresponding to the
preceding applications; all U.S. and foreign patents issuing on any of the
preceding applications, including extensions, reissues and re-examinations; and
any other patent rights owned by XOMA which XOMA has the right to license or
sublicense and which would be infringed by the activities contemplated hereunder
but for this Agreement. XOMA Patent Rights shall also include (i) any
improvements of the foregoing that are owned or controlled by XOMA and (ii) any
patents or patent applications, whether now existing or obtained in the future,
owned or controlled by XOMA containing a claim that is dominating over the
foregoing patent rights (i.e., is necessarily infringed by the practicing of a
claim in one of the foregoing applications).

     The above definitions are intended to encompass the defined terms in both
the singular and plural forms.

                                    ARTICLE 2

                          XOMA GRANT OF RIGHTS TO DYAX

     2.1     LICENSE GRANTS. Subject to the other terms and conditions of this
Agreement, XOMA hereby grants to DYAX a worldwide, non-exclusive,
non-transferable (other than as

                                       -6-
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provided in Section 9.2) license, without any right to sublicense, under the
XOMA Patent Rights and the XOMA Know-How to:

     (a)     solely on its own behalf and on behalf of a DYAX Collaborator, make
             or have made Licensed Antibody Phage Display Materials;

     (b)     solely on its own behalf, on behalf of a Development Partner of
             DYAX and on behalf of a DYAX Collaborator and in any event solely
             for Research and Development purposes, conduct Antibody Phage
             Display;

     (c)     solely on its own behalf, on behalf of a Development Partner of
             DYAX and on behalf of a DYAX Collaborator, make or have made
             Research Quantities of a Licensed Immunoglobulin;

     (d)     solely on its own behalf and on behalf of a DYAX Collaborator,
             transfer Antibody Phage Display Materials;

     (e)     solely on its own behalf, on behalf of a Development Partner of
             DYAX and on behalf of a DYAX Collaborator, transfer Research
             Quantities of a Licensed Immunoglobulin or Licensed Immunoglobulin
             Information to a DYAX Collaborator or a Development Partner of
             DYAX;

     (f)     solely on its own behalf and on behalf of a DYAX Collaborator,
             sell, offer to sell, import and export Licensed Immunoglobulins;

     (g)     solely on its own behalf, on behalf of a Development Partner of
             DYAX and on behalf of a DYAX Collaborator, use Licensed
             Immunoglobulins; and

     (h)     solely on its own behalf and on behalf of a Development Partner of
             DYAX make or have made for commercial purposes, use, offer for
             sale, sell, import and export Products for use in the treatment,
             prophylaxis, diagnosis or monitoring of a human disease state or
             condition.

     For the sake of clarity, (i) the licenses granted in Section 2.1 are
personal to DYAX and are to be used on behalf of any DYAX Collaborator or
Development Partner of DYAX only in respect of or in connection with the
activities that such DYAX Collaborator or Development Partner of DYAX is engaged
in that are the basis for meeting the definition of DYAX Collaborator or
Development Partner of DYAX, as the case may be, and not any other activities,
and (ii) without limiting the foregoing, the license granted in Section 2.1(h)
is not to be used on behalf of any DYAX Collaborator or any other Third Party
that is not a Development Partner of DYAX.

                                       -7-
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     2.2     XOMA TRANSFER TO DYAX. Within thirty (30) days of the Effective
Date, XOMA shall transfer to DYAX, at a reasonable place and time of DYAX's
direction, the materials identified on SCHEDULE 2.2.

     2.3     COVENANT NOT TO SUE. In partial consideration for the payments set
forth in Sections 4.1 and 4.2, XOMA covenants that it shall not initiate or
permit any Third Party over whom it has control to initiate or assist in any way
in the initiation or prosecution of any action asserting a claim of infringement
under the XOMA Patent Rights or misappropriation of the XOMA Know-How against
DYAX, any Development Partner of DYAX or any DYAX Collaborator solely to the
extent reasonably necessary to permit the authorized use of Licensed Antibody
Phage Display Materials, Licensed Immunoglobulins or Licensed Immunoglobulin
Information for activities or in a manner otherwise permitted under the
provisions of this Agreement. The parties agree that the covenant not to sue
provided by this Section 2.3 (i) is a covenant that transfers with any
assignment or sale of, or grant of an exclusive license (with the right to
enforce) under, the applicable XOMA Patent Rights by XOMA and (ii) without
limiting or expanding the provisions of Section 9.2, shall be binding upon any
permitted successors or assigns of XOMA. XOMA agrees to use commercially
reasonable efforts to assist DYAX in recording in a form reasonably acceptable
to XOMA the covenant not to sue provided by this Section 2.3, as permitted, with
the U.S. Patent and Trademark Office. The covenant not to sue provided by this
Section 2.3:

     (a)     shall not extend to infringement of the XOMA Patent Rights or
             misappropriation of the XOMA Know-How arising out of making or the
             means or methods used to make any amount of a Licensed
             Immunoglobulin or Product other than Research Quantities (except as
             authorized by Section 2.1(h));

     (b)     shall become void and without effect as to any entity or person who
             claims its benefit but fails to materially discharge or comply with
             any term of its written agreement with DYAX provided for in
             Section 2.5;

     (c)     is personal to DYAX, such Development Partner of DYAX and such DYAX
             Collaborator and cannot be assigned or transferred; and

     (d)     does not constitute a release or waiver of past, present or future
             infringement of the XOMA Patent Rights or misappropriation of the
             XOMA Know-How by DYAX or any Third Party, including, without
             limitation, any DYAX Collaborator acting outside of the scope of
             the written agreement with DYAX provided for in Section 2.5.

     2.4     NO IMPLIED RIGHTS. Only the rights and licenses granted pursuant to
the express terms of this Agreement shall be of any legal force or effect. No
license or other rights

                                       -8-
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shall be deemed to have been granted to DYAX, a Development Partner of DYAX or a
DYAX Collaborator other than as expressly provided for in this Agreement. For
the avoidance of doubt, the grants of rights made pursuant to Sections 2.1 and
2.3 do not include, and expressly exclude, the following:

     (a)     any right or license to engage in any activities on behalf of or in
             collaboration with any Third Party, other than a Development
             Partner of DYAX or a DYAX Collaborator;

     (b)     any right or license to make or have made any amount (other than
             Research Quantities or except as authorized under Section 2.1(h))
             of a Licensed Immunoglobulin or Product by practicing the XOMA
             Patent Rights or the XOMA Know-How; PROVIDED, HOWEVER, that DYAX
             or, as applicable, a DYAX Collaborator shall be permitted to make
             or have made any Licensed Immunoglobulin by any means of its
             selection other than those which otherwise infringe a Valid Claim
             of the XOMA Patent Rights or utilize the XOMA Know-How; and/or

     (c)     any right to release any Third Party, including a Development
             Partner of DYAX or a DYAX Collaborator, from any claim of
             infringement under the XOMA Patent Rights.

     2.5     TRANSFER RESTRICTIONS. (a) DYAX shall not (i) undertake any
Antibody Phage Display Activities on behalf of a Third Party or (ii) Dispose of
Licensed Antibody Phage Display Materials, a Licensed Immunoglobulin, Licensed
Immunoglobulin Information or the product of the practice of any method within
the scope of the XOMA Patents ("TRANSFERRED MATERIALS") to any Third Party until
(in the case of either clause (i) or clause (ii)) such time as it has provided
to such Third Party the redacted copy of this Agreement referred to in
Section 5.2 and the form of notice set out at SCHEDULE 2.5.

     (b)     If DYAX enters into a written arrangement with any Third Party
arising out of or relating to activities as to which it or such Third Party does
or intends to claim the benefits of any of the licenses or other grants provided
for by this Agreement, such written arrangement shall contain provisions (i)
pursuant to which the recipient of any Transferred Materials agrees to abide by
each of the limitations, restrictions and other obligations provided for by this
Agreement, including, without limitation, the restrictions on use of Transferred
Materials for purposes other than Research and Development; (ii) implementing a
covenant not to use Transferred Materials for any purpose other than for
Research and Development purposes otherwise authorized by this Agreement; (iii)
providing that the "first sale" doctrine does not apply to any Disposition and
(iv) permitting a DYAX Collaborator to further Dispose of Transferred Materials
only to a Third Party who otherwise meets the definition of a DYAX

                                       -9-
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Collaborator and who executes a written agreement in which its undertakes all of
the obligations applied to the transferring party. XOMA shall be, and the
agreements subject to this Section 2.5 shall provide that XOMA shall be, an
intended third party beneficiary with respect to the foregoing provisions.

     2.6     REPORTS, RECORDS AND AUDITS. (a) Thirty (30) days after the end of
each calendar quarter, commencing with the first calendar quarter commencing
after the Effective Date, DYAX shall deliver to XOMA a written report which
shall specify the name, address and contact person for each and every DYAX
Collaborator and any person or entity receiving Licensed Antibody Phage Display
Materials or a Licensed Immunoglobulin. The reports delivered by DYAX to XOMA
pursuant to this Section 2.6(a) shall be Confidential Information of DYAX.

     (b)     Not later than thirty (30) days after the end of each calendar
year, commencing with the first calendar year to commence after the Effective
Date, as and to the extent publicly disclosed by DYAX (whether in press
releases, government filings or otherwise), DYAX shall deliver to XOMA written
materials pertaining to the current status of activities or compositions of
matter as to which DYAX claims the right of license hereunder.

     (c)     DYAX shall maintain records fully and properly reflecting those
activities to be reported to XOMA pursuant to Sections 2.6(a) and (b) (the
"RECORDS"), in sufficient detail and in good scientific manner appropriate for
patent, regulatory and manufacturing purposes for at least three (3) years. Upon
the written request of XOMA and not more than once in each calendar year, DYAX
shall permit an independent consultant appointed by XOMA, at XOMA's expense, to
have access during normal business hours to such of the records of DYAX as may
be reasonably necessary to verify compliance with the terms of this Agreement,
as well as the accuracy of the reports hereunder. DYAX shall certify any
statements by DYAX personnel as to their accuracy and correctness. The
consultant shall not be permitted to see or receive any specific information
concerning targets or antibodies of either DYAX or any of its collaborators and
shall disclose to XOMA only the results and conclusions of its review and the
specific details concerning any discrepancies. No other information shall be
shared by the consultant without the prior consent of DYAX unless disclosure is
required by law, regulation or judicial order.

     2.7     OWNERSHIP; ENFORCEMENT. At all times XOMA will retain ownership of
the XOMA Patent Rights and may use and commercialize such XOMA Patent Rights
itself or with any Third Party. XOMA retains the right, at its sole discretion,
to enforce, maintain and otherwise protect the XOMA Know-How and the XOMA Patent
Rights. In addition to the requirements of Section 2.6, DYAX shall give XOMA
prompt notice of any infringement of any of the XOMA Patent Rights by a Third
Party engaging in a Commercial Antibody Phage Display Business which comes to
DYAX's attention during the term of this Agreement.

                                      -10-
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                                        CONFIDENTIAL MATERIALS OMITTED AND
                                        FILED SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

     DYAX will reasonably cooperate with XOMA with respect to any actions XOMA
may choose to take related to the enforcement, maintenance or protection of the
XOMA Patent Rights.

     2.8     OPPOSITIONS AND/OR APPEALS TO OPPOSITIONS. DYAX hereby agrees not
to enter into any opposition to and/or appeal from any decision by the patent
authorities of any country on the XOMA Patent Rights and shall not assist or
otherwise cooperate with another party in any such opposition or appeal.

     2.9     RELEASE FROM PAST INFRINGEMENT. XOMA releases DYAX from any claims,
demands, and rights of action arising out of and/or based upon any act or
omission committed by DYAX prior to the Effective Date, including, without
limitation, claims of infringement under the XOMA Patent Rights (the "RELEASE"),
and XOMA releases those Third Parties identified upon SCHEDULE 2.9(i) from any
claims, demands, and rights of action arising out of and based upon any
infringement of the XOMA Patent Rights (the "THIRD PARTY RELEASE"); PROVIDED,
HOWEVER, that the Release and Third Party Release provided for in this
Section 2.9 shall extend only to claims, demands or rights of action existing as
of the Effective Date and which arose solely out of those activities specified
in SCHEDULE 2.9(ii). Nothing in this Section 2.9 shall be deemed to be a release
of any claim, demand or right of action XOMA may now or in the future have
against [*****] or any of their collaborators (except, in the case of any such
collaborator that is also a collaborator of DYAX, to the extent such
collaborator's activities with DYAX are directly and exclusively within the
scope of the Third Party Release). The Release and the Third Party Release shall
become irrevocable only upon receipt by XOMA of payment in full by DYAX of all
installments of the amounts set forth in Section 4.1 and shall be revoked in
their entirety and null and void AB INITIO, immediately and without further
action of the parties, in the event any installment of such amounts is not
received by XOMA on or prior to the fifteenth day following written notice to
DYAX from XOMA of DYAX's breach in the payment of the full amount of such
installment on or prior to the payment date for such installment as set forth in
Section 4.1, regardless of any payment received thereafter.

                                    ARTICLE 3

                          DYAX GRANT OF RIGHTS TO XOMA

     3.1     LICENSE GRANTS. Subject to the other terms and conditions of this
Agreement, DYAX hereby grants to XOMA, on its own behalf and on behalf of its
Development Partners, a fully paid up, non-exclusive, royalty-free, worldwide
license under the DYAX Patent Rights, to discover, isolate, optimize, develop,
offer to use, use, offer for sale, sell, make, have made, export and import
Immunoglobulins or products containing or comprising an Immunoglobulin

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in the XOMA Field of Use, including without limitation the right to conduct
phage display under the DYAX Patent Rights but excluding the conduct of phage
display as a Commercial Antibody Phage Display Business. XOMA shall not have the
right to sublicense its license rights under the DYAX Patent Rights to any Third
Party. XOMA may not transfer to any Third Party any phage display library the
use of which by XOMA is otherwise licensed hereunder if the use thereof by such
Third Party would infringe a Valid Claim of the DYAX Patent Rights. For the
avoidance of doubt, nothing herein is intended to prevent XOMA from transferring
any Immunoglobulin or any product containing or comprising an Immunoglobulin to
a Development Partner of XOMA or a Third Party working on behalf of XOMA or a
Development Partner of XOMA to make, have made, use, sell, have sold and import
products, PROVIDED that the use of such Immunoglobulin or product by the
Development Partner or Third Party does not infringe a Valid Claim of the DYAX
Patent Rights. XOMA is licensed hereby to use phage display materials, including
without limitation phage display libraries, received from any Third Party, free
from any contractual obligations or limitations otherwise applicable thereto, so
long as XOMA otherwise abides by the terms and conditions of this Agreement. Any
use of such phage display materials by XOMA shall be governed in all respects by
the provisions of this Agreement and not the provisions of any agreements
between DYAX and any Third Party providing phage display materials to XOMA.
Furthermore, for the avoidance of doubt, solely within the XOMA Field of Use,
DYAX grants to XOMA, consistent with the other terms and conditions of this
Agreement, a fully paid-up, non-exclusive, royalty-free worldwide right and
license to use the DYAX Materials (as defined below).

     3.2     COVENANT NOT TO SUE. DYAX covenants that it shall not initiate or
permit any Third Party over whom it has control to initiate or assist in any way
in the initiation or prosecution of any action asserting a claim of infringement
under the DYAX Patent Rights against XOMA or any Development Partner of XOMA or
misappropriation of the DYAX Materials against XOMA solely to the extent such
claims arise out of (a) use of the DYAX Materials by XOMA as permitted under the
provisions of this Agreement or (b) the discovery, isolation, optimization or
development by XOMA, or the manufacture, use, offer for use, sale, offer for
sale, importation and exportation, of any Immunoglobulin or product containing
or comprising an Immunoglobulin which were discovered under conditions which but
for this license would constitute misappropriation or infringement of the DYAX
Patent Rights.

     3.3     DYAX TRANSFER TO XOMA. (a) Within thirty (30) days after a written
request by XOMA provided to DYAX within 18 months of the Effective Date, DYAX
shall transfer to XOMA all of the materials, including without limitation the
Licensed Antibody Phage Display Materials, specified on SCHEDULE 3.3 (the "DYAX
Materials"). DYAX shall provide up to two person-days of DYAX scientific staff
time at DYAX's facilities during the first three months after transfer of the
DYAX Materials to XOMA (which period may be extended by mutual consent of the
parties, which consent shall not be unreasonably withheld) at no ex-

                                      -12-
<Page>

pense to XOMA. Thereafter, XOMA will be able to consult with DYAX scientific
staff at $2,500/person-day (based on an eight hour day) beyond the two
person-days. The cost of all reasonable travel-related expenses will be fully
reimbursed to DYAX by XOMA. The DYAX Materials shall be Confidential Information
subject to Article 5.

     (b)     DYAX represents and warrants that the DYAX Materials comprise the
Licensed Antibody Phage Display Materials, including the know-how and protocols
for using such Licensed Antibody Phage Display Materials, that DYAX customarily
provides to licensees of antibody phage display libraries for screening
purposes.

     3.4     OWNERSHIP; ENFORCEMENT. At all times DYAX will retain ownership or
control of the DYAX Patent Rights and may use and commercialize such DYAX Patent
Rights itself or with any Third Party. DYAX retains the right, at its sole
discretion, to enforce, maintain and otherwise protect the DYAX Patent Rights.
XOMA will reasonably cooperate with DYAX with respect to any actions DYAX may
choose to take related to the enforcement, maintenance or protection of the DYAX
Patent Rights.

     3.5     OPPOSITIONS AND/OR APPEALS TO OPPOSITIONS. XOMA hereby agrees not
to enter into any oppositions to and/or appeal from any decision by the patent
authorities of any country on the DYAX Patent Rights and shall not assist or
otherwise cooperate with another party in any such opposition or appeal.

                                    ARTICLE 4

                                    PAYMENTS

     4.1     TECHNOLOGY ACCESS AND RELEASE FEE. In consideration for the rights
granted to DYAX and DYAX Collaborators pursuant to Sections 2.1, 2.2, 2.3 and
2.9, DYAX shall pay XOMA a fee of Three Million Five Hundred Thousand United
States Dollars (US$3,500,000) payable in cash in six installments, with the
first such installment, in the amount of Two Hundred and Fifty Thousand United
States Dollars (US$250,000), due within five (5) business days of the Effective
Date; the second such installment, in the amount of One Million Two Hundred and
Fifty Thousand United States Dollars (US$1,250,000), due on or before December
15, 2002; and an additional installment, each in the amount of Five Hundred
Thousand United States Dollars (US$500,000), due on or before the fifteenth day
of the last month of each of four consecutive calendar quarters, commencing with
the quarter beginning January 1, 2003. Technology transfer is included in the
access fee and includes up to two person-days of XOMA scientific staff time at
XOMA's facilities prior to December 31, 2002 (which period may be extended by
mutual consent of the parties, which consent shall not be unreasonably
withheld). Thereafter, DYAX will be able to consult with XOMA scientific staff
at

                                      -13-
<Page>

                                        CONFIDENTIAL MATERIALS OMITTED AND
                                        FILED SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

$2,500/person-day (based on an eight hour day) beyond the two person-days. The
cost of all reasonable travel-related expenses will be fully reimbursed to XOMA
by DYAX.

     4.2     ROYALTIES. (a) During the term of this Agreement, DYAX shall pay to
XOMA a royalty in cash equal to [*****] percent ([*****]%) of the Net Sales of
any Product(s) in each calendar quarter, commencing with the first calendar
quarter ending after the Effective Date. Notwithstanding the foregoing, no
royalty shall be payable on Net Sales by or on behalf of a DYAX Collaborator
that is not a Development Partner of DYAX where neither DYAX nor any Development
Partner of DYAX directly or indirectly sells the Product.

     (b)     Royalties due under this Article 4 shall be payable on a
country-by-country and Product-by-Product basis from the First Commercial Sale
of such Product until the expiration of the last-to-expire XOMA Patent Right in
such country with respect to which a Valid Claim covers the manufacture, use,
sale, offer for sale, import or export of such Product or the tenth anniversary
of such First Commercial Sale, whichever is later.

     4.3     COMMERCIALLY REASONABLE EFFORTS. DYAX will use its commercially
reasonable efforts to exploit the XOMA Patent Rights, generate and use Licensed
Antibody Phage Display Materials, conduct Antibody Phage Display, discover,
identify, characterize, develop and commercially launch Licensed Immunoglobulins
and Products and/or maximize the amounts available to be shared with XOMA
pursuant to this Article 4. DYAX shall also use commercially reasonable efforts
to collect or receive any payments or other consideration due to it relating to
any activities that would give rise to an obligation under Section 4.2.

     4.4     PAYMENTS; CURRENCY. All payments due hereunder shall be paid by
wire transfer in United States dollars in immediately available funds to an
account designated by XOMA. Payments required pursuant to Section 4.2 hereof
shall be due and payable to XOMA when the corresponding Net Sales are received
by DYAX (or any joint venture or similar arrangement in which DYAX is a
participant) and shall be paid within thirty (30) days of the end of each
calendar quarter. If any currency conversion shall be required in connection
with the payment of any royalties hereunder, such conversion shall be made by
using the exchange rate for the purchase of U.S. dollars quoted in the U.S.
version of the Wall Street Journal on the last business day of the calendar
quarter to which such payments relate.

     4.5     PAYMENT REPORTS. After the First Commercial Sale of a Product on
which royalties are required to be paid hereunder, DYAX shall make quarterly
written reports to XOMA within thirty (30) days after the end of each calendar
quarter, stating in each such report, by country, the number, description, and
aggregate Net Sales of each Product sold during the calendar quarter. XOMA shall
treat all such reports as Confidential Information of DYAX. Concurrently with
the making of such reports, DYAX shall pay XOMA the amounts specified in
Section 4.2 hereof.

<Page>

     4.6     PAYMENT RECORDS AND INSPECTION. DYAX shall keep complete, true and
accurate books of account and records for the purpose of determining the amounts
payable under this Agreement. Such books and records shall be kept at the
principal place of business of DYAX for at least three (3) years following the
end of the calendar quarter to which they pertain. Upon the written request of
XOMA and not more than once in each calendar year, DYAX shall permit an
independent consultant appointed by XOMA and reasonably acceptable to DYAX to
have access during normal business hours to such of the records of DYAX as may
be reasonably necessary to verify the accuracy of the royalty reports hereunder
for any year ending not more than thirty-six (36) months prior to the date of
such request, unless a discrepancy is found. The consultant shall disclose to
XOMA only the results and conclusions of its review and the specific details
concerning any discrepancies. No other information shall be shared by the
consultant without the prior consent of DYAX unless disclosure is required by
law, regulation or judicial order. The consultant may be obliged to execute a
reasonable confidentiality agreement prior to commencing any such inspection.
Inspections conducted under this Section 4.6 shall be at the expense of XOMA,
unless an underpayment exceeding five percent (5%) of the amount stated for the
full period covered by the inspection is identified, in which case all
out-of-pocket costs relating to the inspection will be paid promptly by DYAX.
Any underpayments or unpaid amounts discovered by such inspections or otherwise
will be paid promptly by DYAX, with interest from the date(s) such amount(s)
were due at a rate equal to the lesser of the prime rate reported by the Bank of
America plus two percent (2%) or the highest interest rate permitted under
applicable law.

                                    ARTICLE 5

                                 CONFIDENTIALITY

     5.1     CONFIDENTIAL INFORMATION. Except as expressly provided herein, the
parties agree that, for the term of this Agreement and for five (5) years
thereafter, the receiving party shall keep completely confidential and shall not
publish or otherwise disclose and shall not use for any purpose except for the
purposes contemplated by this Agreement any Confidential Information furnished
to it by the disclosing party hereto, except to the extent that it can be
established by the receiving party by written proof that such Confidential
Information:

     (a)     was already known to the receiving party, other than under an
             obligation of confidentiality, at the time of disclosure;

     (b)     was generally available to the public or otherwise part of the
             public domain at the time of its disclosure to the receiving party;

                                      -15-
<Page>

     (c)     became generally available to the public or otherwise part of the
             public domain after its disclosure other than through any act or
             omission of the receiving party in breach of this Agreement; or

     (d)     was subsequently lawfully disclosed to the receiving party by a
             person other than a party hereto.

     5.2     PERMITTED USE AND DISCLOSURES. Each party hereto may use or
disclose information disclosed to it by the other party to the extent such use
or disclosure is reasonably necessary in complying with applicable law or
government regulations or conducting clinical trials; PROVIDED, HOWEVER, that if
a party is required to make any such disclosure of another party's Confidential
Information, other than pursuant to a confidentiality agreement, it will give
reasonable advance notice to the latter party of such disclosure and, will use
its reasonable efforts to secure confidential treatment of such information
prior to its disclosure (whether through protective orders or otherwise).
Attached hereto as SCHEDULE 5.2 is a redacted copy of this Agreement which DYAX
shall be free, without obtaining any consent from XOMA, to provide to Third
Parties who indicate an interest in becoming a DYAX Collaborator or a
Development Partner of DYAX.

     5.3     CONFIDENTIAL TERMS. Except as expressly provided herein, each party
agrees not to disclose any terms of this Agreement to any Third Party without
the consent of the other party; PROVIDED, that disclosures may be made as
required by securities or other applicable laws, or to a party's accountants,
attorneys and other professional advisors.

     5.4     AGREEMENT ANNOUNCEMENT. The parties hereby agree to the release of
a press release in the form attached hereto as SCHEDULE 5.4 upon full execution
of this Agreement and that the consummation of this Agreement, as well as such
terms as are expressly described in such press release, shall be deemed to be in
the public domain.

                                    ARTICLE 6

                         REPRESENTATIONS AND WARRANTIES

     6.1     REPRESENTATIONS AND WARRANTIES. (a) XOMA represents and warrants to
DYAX that: (i) it is the sole and exclusive owner or exclusive licensee of all
right, title and interest in the XOMA Patent Rights; (ii) XOMA has the legal
right, authority and power to enter into this Agreement; (iii) this Agreement
shall constitute a valid and binding obligation of XOMA enforceable in
accordance with its terms; and (iv) the performance of obligations under this
Agreement by XOMA shall not result in a breach of any agreements, contracts or
other arrangements to which it is a party.

                                      -16-
<Page>

     (b)     DYAX represents and warrants to XOMA that: (i) it is the sole and
exclusive owner or exclusive licensee of all right, title and interest in the
DYAX Patent Rights, (ii) DYAX has the legal right, authority and power to enter
into this Agreement; (iii) this Agreement shall constitute a valid and binding
obligation of DYAX enforceable in accordance with its terms; and (iv) the
performance of obligations under this Agreement by DYAX shall not result in a
breach of any agreements, contracts or other arrangements to which it is a
party.

     6.2     DISCLAIMER.  Nothing in this Agreement is or shall be construed as:

     (a)     A warranty or representation by XOMA or DYAX as to the validity or
             scope of any claim or patent within the XOMA Patent Rights or the
             DYAX Patent Rights, as the case may be;

     (b)     A warranty or representation that anything made, used, sold, or
             otherwise disposed of under any license granted in this Agreement
             is or will be free from infringement of any patent rights or other
             intellectual property right of any Third Party;

     (c)     An obligation to bring or prosecute actions or suits against Third
             Parties for infringement of any of the XOMA Patent Rights or the
             DYAX Patent Rights;

     (d)     An obligation to maintain any patent or to continue to prosecute
             any patent application included within the XOMA Patent Rights or
             the DYAX Patent Rights in any country; or

     (e)     Granting by implication, estoppel, or otherwise any licenses or
             rights under patents or other rights of XOMA, DYAX or Third
             Parties, regardless of whether such patents or other rights are
             dominant or subordinate to any patent within the XOMA Patent Rights
             or the DYAX Patent Rights, as the case may be.

     6.3     NO OTHER WARRANTIES. EXCEPT AS OTHERWISE SET FORTH IN SECTION 6.1
ABOVE, NEITHER PARTY HERETO MAKES ANY WARRANTIES WITH RESPECT TO ANY OF THE
PATENT RIGHTS, MATERIALS OR KNOW-HOW LICENSED HEREUNDER, EXPRESS OR IMPLIED,
EITHER IN FACT OR BY OPERATION OF LAW, BY STATUTE OR OTHERWISE, AND EACH PARTY
SPECIFICALLY DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OF MERCHANTABILITY, OF
FITNESS FOR A PARTICULAR PURPOSE, OF VALIDITY OF SUCH PATENT RIGHTS, MATERIALS
OR KNOW-HOW, ARISING FROM COURSE OF DEALING OR OF NON-INFRINGEMENT OF THE
INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY.

                                      -17-
<Page>

     6.4 CERTAIN AGREEMENTS. DYAX represents and warrants that it has in its
possession, and agrees that throughout the term of this Agreement it will
maintain in an accessible location, true, complete and legible copies of each of
the agreements set forth on Schedule 2.9 as in effect on the Effective Date,
including all schedules, exhibits and other similar documents necessary for the
correct interpretation of the provisions thereof.

                                    ARTICLE 7

                                 INDEMNIFICATION

     7.1     INDEMNIFICATION OF XOMA BY DYAX. DYAX agrees to indemnify, defend
and hold XOMA and its directors, officers, employees and agents (the "XOMA
INDEMNIFIED PARTIES") harmless from and against any and all liabilities, losses
and expenses (including, without limitation, attorneys and professional fees and
other costs of litigation), resulting from any claims, demands or causes of
action by any party other than DYAX (each, a "XOMA LIABILITY") arising out of
(i) the possession, manufacture, use, sale or other disposition of Product,
Antibody Phage Display Materials, Licensed Immunoglobulin or the provision of
any service or goods relating thereto by DYAX or any customer, vendor or other
representative of DYAX, whether based on breach of warranty, negligence, product
liability or otherwise, or (ii) the exercise of any right granted to DYAX
pursuant to this Agreement, except to the extent, in each case, that such XOMA
Liability is caused by the negligence or willful misconduct of XOMA.

     7.2     INDEMNIFICATION OF DYAX BY XOMA. XOMA agrees to indemnify, defend
and hold DYAX and its directors, officers, employees and agents (the "DYAX
INDEMNIFIED PARTIES") harmless from and against any and all liabilities, losses
and expenses (including, without limitation, attorneys and professional fees and
other costs of litigation), resulting from any claims, demands or causes of
action by any party other than XOMA (each, a "DYAX LIABILITY") arising out of
(i) the possession, manufacture, use, sale or other disposition of products or
materials resulting from the practice by XOMA of the DYAX Patent Rights, the use
by XOMA of DYAX Materials or the provision of any service or goods relating
thereto by XOMA or any customer, vendor or other representative of XOMA, whether
based on breach of warranty, negligence, product liability or otherwise, or (ii)
the exercise of any right granted to XOMA pursuant to this Agreement, except to
the extent, in each case, that such DYAX Liability is caused by the negligence
or willful misconduct of DYAX.

     7.3     PROCEDURE. (a) To receive the benefit of indemnification under
Section 7.1, a XOMA Indemnified Party must (i) promptly notify DYAX in writing
of a claim or suit; PROVIDED, that failure to give such notice shall not relieve
DYAX of its indemnification obligations except where, and solely to the extent
that, such failure actually and materially preju-

                                      -18-
<Page>

dices the rights of DYAX; (ii) provide reasonable cooperation (at DYAX's
expense); and (iii) tender to DYAX (and its insurer) full authority to defend or
settle the claim or suit; PROVIDED that no settlement requiring any admission by
the XOMA Indemnified Party or that imposes any obligation on the XOMA
Indemnified Party shall be made without the XOMA Indemnified Party's consent.
DYAX shall not have any obligation to indemnify the other party in connection
with any settlement made without DYAX's written consent. The XOMA Indemnified
Party has the right to participate at its own expense in the claim or suit and
in selecting counsel therefor. The XOMA Indemnified Party shall cooperate with
DYAX (and its insurer), as reasonably requested.

     (b)     To receive the benefit of indemnification under Section 7.2, a DYAX
Indemnified Party must (i) promptly notify XOMA in writing of a claim or suit;
PROVIDED, that failure to give such notice shall not relieve XOMA of its
indemnification obligations except where, and solely to the extent that, such
failure actually and materially prejudices the rights of XOMA; (ii) provide
reasonable cooperation (at XOMA's expense); and (iii) tender to XOMA (and its
insurer) full authority to defend or settle the claim or suit; PROVIDED that no
settlement requiring any admission by the DYAX Indemnified Party or that imposes
any obligation on the DYAX Indemnified Party shall be made without the DYAX
Indemnified Party's consent. XOMA shall not have any obligation to indemnify the
other party in connection with any settlement made without XOMA's written
consent. The DYAX Indemnified Party has the right to participate at its own
expense in the claim or suit and in selecting counsel therefor. The DYAX
Indemnified Party shall cooperate with XOMA (and its insurer), as reasonably
requested.

                                    ARTICLE 8

                              TERM AND TERMINATION

     8.1     TERM. Subject to Sections 8.5 and 8.6 hereof, the term of this
Agreement will commence on the Effective Date and (a) with regard to the license
rights granted to XOMA by DYAX pursuant to Article 3, this Agreement shall
remain in full force and effect until the last to expire of the DYAX Patent
Rights, unless earlier terminated by DYAX pursuant to Section 8.2, 8.3 or 8.4;
PROVIDED, HOWEVER, that upon such expiration and absent any earlier termination
pursuant to Section 8.2, 8.3 or 8.4, XOMA shall have a royalty-free, fully paid
up right and license to continue to use the DYAX Materials as permitted by
Article 3; and (b) with regard to the license and other rights granted to DYAX
and any DYAX Collaborators or Development Partners of DYAX by XOMA pursuant to
Article 2, this Agreement shall remain in full force and effect until the last
to expire of the XOMA Patent Rights or the tenth anniversary of the First
Commercial Sale of the last Product to be launched, whichever is later, unless
earlier terminated by XOMA pursuant to Section 8.2, 8.3 or 8.4; PROVIDED,

                                      -19-
<Page>

HOWEVER, that, to the extent any of the XOMA Know-How is not included in the
XOMA Patent Rights, upon such expiration and absent any earlier termination
pursuant to Section 8.2, 8.3 or 8.4, DYAX shall have a royalty-free, fully paid
up right and license to continue to use the XOMA Know-How as permitted by
Article 2.

     8.2     TERMINATION FOR MATERIAL BREACH. With regard to (a) the license
rights granted to XOMA by DYAX pursuant to Article 3, or (b) the license and
other rights granted to DYAX and any DYAX Collaborators or Development Partners
of DYAX by XOMA pursuant to Article 2, this Agreement may be terminated by
either DYAX or XOMA upon any material breach by XOMA or DYAX, as the case may
be, of any material obligation or condition of the Agreement, in either case
effective fifteen (15) days after giving notice to the breaching party of such
termination in the case of a payment breach and sixty (60) days after giving
written notice to the breaching party of such termination in the case of any
other breach, which notice shall describe such breach in reasonable detail. The
foregoing notwithstanding, if such breach is cured or shown to be non-existent
within the aforesaid fifteen (15) or sixty (60) day period, the notice shall be
deemed automatically withdrawn and of no effect and the notifying party shall
provide written notice to the breaching party of the withdrawal. A termination
of the breaching party's rights and licenses pursuant to this Section 8.2 shall
not effect the non-breaching party's rights and licenses, which shall continue
until otherwise terminated in accordance with this Agreement.

     8.3     TERMINATION FOR INSOLVENCY. If voluntary or involuntary proceedings
by or against either party are instituted in bankruptcy under any insolvency
law, or a receiver or custodian is appointed for either party, or proceedings
are instituted by or against either party for corporate reorganization or the
dissolution of such party, which proceedings, if involuntary, shall not have
been dismissed within sixty (60) days after the date of filing, or if either
party makes an assignment for the benefit of creditors, or substantially all of
the assets of either party are seized or attached and not released within sixty
(60) days thereafter, the other party may immediately terminate this Agreement
effective upon notice of such termination.

     8.4     CONTESTED VALIDITY. If DYAX, a DYAX Collaborator or any person or
entity controlled by any of the foregoing contests the validity or
enforceability of any of the XOMA Patent Rights licensed hereunder, XOMA shall
have the right to terminate all of the rights and licenses hereby granted to
DYAX and any DYAX Collaborator under the XOMA Patent Rights; PROVIDED, HOWEVER,
that in the event a DYAX Collaborator contests the validity or enforceability of
any of the XOMA Patent Rights licensed hereunder other than at the direction,
and without the assistance or other involvement, of DYAX, then the foregoing
termination right of XOMA shall apply only to the rights hereby granted to such
DYAX Collaborator. If XOMA or any person or entity controlled by XOMA contests
the validity or enforceability of

                                      -20-
<Page>

any of the DYAX Patent Rights licensed hereunder, DYAX shall have the right to
terminate all of the rights and licenses hereby granted to XOMA under the DYAX
Patent Rights.

     8.5     EFFECT OF TERMINATION. (a) Termination of this Agreement shall not
release any party hereto from any liability which, at the time of such
termination, has already accrued to the other party or which is attributable to
a period prior to such termination nor preclude either party from pursuing any
rights and remedies it may have hereunder or at law or in equity with respect to
any breach of this Agreement. It is understood and agreed that monetary damages
may not be a sufficient remedy for any breach of this Agreement and that the
non-breaching party may be entitled to injunctive relief as a remedy for any
such breach. Such remedy shall not be deemed to be the exclusive remedy for any
such breach of this Agreement, but shall be in addition to all other remedies
available at law or in equity.

     (b)     Upon any termination of this Agreement, DYAX and XOMA shall
promptly return to the other party all Confidential Information received from
the other party (except that each party may retain one copy for its files solely
for the purpose of determining its rights and obligations hereunder).

     (c)     Except as expressly provided in Sections 8.1 and 8.2, all licenses
granted under Article 2 hereof shall terminate and be of no further effect upon
the termination of this Agreement.

     8.6     SURVIVAL. Sections 2.6(c), 2.7, 2.8, 2.9, 3.3, 3.4, 4.2, 4.4, 4.5,
4.6, 8.2, 8.5 and 8.6, and Articles 1, 5, 6, 7 and 9 of this Agreement shall
survive any termination hereof. Without limiting the foregoing, Article 2 of
this Agreement shall survive any termination hereof by DYAX, and Article 3 of
this Agreement shall survive any termination hereof by XOMA.

                                    ARTICLE 9

                            MISCELLANEOUS PROVISIONS

     9.1     GOVERNING LAWS. This Agreement and any dispute, including without
limitation any arbitration, arising from the performance or breach hereof shall
be governed by and construed and enforced in accordance with the laws of the
state of New York, without reference to conflicts of laws principles.

     9.2     ASSIGNMENT. Neither party may transfer or assign this Agreement,
directly or indirectly, or any of its rights hereunder without the prior written
consent of the other party, other than (a) to one or more Affiliates, (b) to a
successor of XOMA Ltd. under a Change in

                                      -21-
<Page>

                                        CONFIDENTIAL MATERIALS OMITTED AND
                                        FILED SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

Control of XOMA Ltd. or to a successor of DYAX Corp. under a Change in Control
of DYAX Corp. to which Section 9.3 does not apply, or (c) to a Third Party in
connection with the transfer or sale of all or substantially all or its business
relating to antibody selection, development and production and the provision of
related services (other than (i) with respect to such a transfer or sale by
DYAX, such a transfer or sale to any Person listed or described in Section 9.3
and (ii) with respect to such a transfer or sale by XOMA, such a transfer or
sale to [*****]. Any such attempted transfer or assignment in violation of this
Section 9.2 shall be void; PROVIDED, that in the event of a permitted Change in
Control, the original party's (or its successor's) obligations hereunder shall
continue. This Agreement shall be binding upon and inure to the benefit of the
parties and their permitted successors and assigns.

     9.3     CERTAIN CHANGES IN CONTROL. Notwithstanding any other provision of
this Agreement to the contrary, the license and other rights granted pursuant to
Article 2 shall automatically terminate, without further action by the parties,
in the event of (a) a transaction or series of related transactions in which
[*****] is a party and which results in a Change of Control of DYAX, or (b) a
transaction or series of related transactions in which DYAX is a party and which
results in a Change in Control of a person or entity described in clause (a)
above.

     9.4     WAIVER. No waiver of any rights shall be effective unless consented
to in writing by the party to be charged and the waiver of any breach or default
shall not constitute a waiver of any other right hereunder or any subsequent
breach or default.

     9.5     SEVERABILITY. In the event that any provisions of this Agreement
are determined to be invalid or unenforceable by a court of competent
jurisdiction, the remainder of the Agreement shall remain in full force and
effect without said provision.

     9.6     NOTICES. All notices, requests and other communications hereunder
shall be in writing and shall be delivered or sent in each case to the
respective address specified below, or such other address as may be specified in
writing to the other party hereto, and shall be effective on receipt:

     DYAX:               DYAX Corp.
                         300 Technology Square
                         Cambridge, MA  02139
                         U.S.A.
                         Attn: Chief Executive Officer

<Page>

     XOMA:               XOMA Ireland Limited
                         Shannon Airport House
                         Shannon, County Clare
                         Ireland
                         Attn: Company Secretary

     with a copy (which shall not constitute notice) to:

                         XOMA (US) LLC
                         2910 Seventh Street
                         Berkeley, CA  94710
                         U.S.A.
                         Attn: Company Secretary

     9.7     INDEPENDENT CONTRACTORS. Both parties are independent contractors
under this Agreement. Nothing contained in this Agreement is intended nor is to
be construed so as to constitute XOMA or DYAX as partners or joint venturers
with respect to this Agreement. Except as expressly provided herein, neither
party shall have any express or implied right or authority to assume or create
any obligations on behalf of or in the name of the other party or to bind the
other party to any other contract, agreement, or undertaking with any third
party.

     9.8     COMPLIANCE WITH LAWS. In exercising their rights under this
license, the parties shall comply in all material respects with the requirements
of any and all applicable laws, regulations, rules and orders of any
governmental body having jurisdiction over the exercise of rights under this
Agreement.

     9.9     BANKRUPTCY. All rights and licenses granted under or pursuant to
this Agreement by one party to the other are, for all purposes of Section 365(n)
of Title XI of the United States Code ("TITLE XI"), licenses of rights to
"intellectual property" as defined in Title XI. During the term of this
Agreement each party shall create and maintain current copies to the extent
practicable of all such intellectual property. If a bankruptcy proceeding is
commenced by or against one party under Title XI, the other party shall be
entitled to a copy of any and all such intellectual property and all embodiments
of such intellectual property, and the same, if not in the possession of such
other party, shall be promptly delivered to it (a) upon such party's written
request following the commencement of such bankruptcy proceeding, unless the
party subject to such bankruptcy proceeding, or its trustee or receiver, elects
within thirty (30) days to continue to perform all of its obligations under this
Agreement, or (b) if not delivered as provided under clause (a) above, upon such
other party's request following the rejection of this Agreement by or on behalf
of the party subject to such bankruptcy proceeding. If a party has taken
possession of all applicable embodiments of the intellectual property of the
other party pursuant to this Section 9.9 and the trustee in bankruptcy of the
other party

                                      -23-
<Page>

does not reject this Agreement, the party in possession of such intellectual
property shall return such embodiments upon request. If a party seeks or
involuntarily is placed under Title XI and the trustee rejects this Agreement as
contemplated under 11 U.S.C. 365(n)(1), the other party hereby elects, pursuant
to Section 365(n) of Title XI, to retain all rights granted to it under this
Agreement to the extent permitted by law.

     9.10    USE OF NAME. Neither party shall use the name or trademarks of the
other party, except to the extent that a party is permitted to use the
Confidential Information of the other party pursuant to Article 5, without the
prior written consent of such other party.

     9.11    FURTHER ACTIONS. Each party agrees to execute, acknowledge and
deliver such further instruments, and do such other acts, as may be necessary
and appropriate in order to carry out the purposes and intent of this Agreement.

     9.12    ENTIRE AGREEMENT; AMENDMENT. This Agreement constitutes the entire
and exclusive Agreement between the parties with respect to the subject matter
hereof and supersedes and cancels all previous discussions, agreements,
commitments and writings in respect thereof. No amendment or addition to this
Agreement shall be effective unless reduced to writing and executed by the
authorized representatives of the parties.

     9.13    ARBITRATION. (a) Solely with respect to any dispute between the
parties to this Agreement (other than any dispute which arises out of or relates
to infringement, validity and/or enforceability of the XOMA Patent Rights or the
DYAX Patent Rights) upon ten (10) days written notice, any party involved in the
dispute may initiate arbitration by giving notice to that effect to the other
party or parties involved in the dispute and by filing the notice with the
American Arbitration Association or its successor organization ("AAA") in
accordance with its Commercial Arbitration Rules. Such dispute shall then be
settled by arbitration in New York, New York, in accordance with the Commercial
Arbitration Rules of the AAA or other rules agreed to by the parties involved in
the dispute, by a panel of three neutral arbitrators, who shall be selected by
the parties involved in the dispute using the procedures for arbitrator
selection of the AAA.

     (b)     The parties acknowledge that this Agreement evidences a transaction
involving interstate commerce. Insofar as it applies, the United States
Arbitration Act shall govern the interpretation of, enforcement of, and
proceedings pursuant to the arbitration clause in this Agreement. Except insofar
as the United States Arbitration Act applies to such matters, the agreement to
arbitrate set forth in this Section 9.13 shall be construed, and the legal
relations among the parties shall be determined in accordance with, the
substantive laws of the State of New York.

                                      -24-
<Page>

     (c)     The panel shall render its decision and award, including a
statement of reasons upon which such award is based, within thirty (30) days
after the arbitration hearing. The decision of the panel shall be determined by
majority vote among the arbitrators, shall be in writing and shall be binding
upon the parties involved in the dispute, final and non-appealable. Judgment
upon the award rendered by the panel may be entered in any court having
jurisdiction thereof in accordance with Section 9.14(a).

     (d)     Except as provided under the United States Arbitration Act and with
respect to the infringement, validity and/or enforceability of the XOMA Patent
Rights or the DYAX Patent Rights, no action at law or in equity based upon any
dispute that is subject to arbitration under this Section 9.13 shall be
instituted.

     (e)     All expenses of any arbitration pursuant to this Section 9.13,
including fees and expenses of the parties' attorneys, fees and expenses of the
arbitrators, and fees and expenses of any witness or the cost of any proof
produced at the request of the arbitrators, shall be paid by the non-prevailing
party.

     9.14    VENUE; JURISDICTION. (a) Any action or proceeding brought by either
party seeking to enforce any provision of, or based on any right arising out of,
this Agreement must be brought against any of the parties in the courts of the
State of New York. Each party (i) hereby irrevocably submits to the jurisdiction
of the state courts of the State of New York and to the jurisdiction of any
United States District Court in the State of New York, for the purpose of any
suit, action, or other proceeding arising out of or based upon this Agreement or
the subject matter hereof brought by any party or its successors or assigns,
(ii) hereby waives, and agrees not to assert, by way of motion, as a defense, or
otherwise, in any such suit, action, or proceeding, any claim that it is not
subject personally to the jurisdiction of the above-named courts, that its
property is exempt or immune from attachment or execution, that the suit, action
or proceeding is brought in an inconvenient forum, that the venue of the suit,
action, or proceeding is improper or that this Agreement or the subject matter
hereof may not be enforced in or by such court, and (iii) hereby waives and
agrees not to seek any review by any court of any other jurisdiction that may be
called upon to grant an enforcement of the judgment of any such New York state
or federal court.

     (b)     Process in any action or proceeding seeking to enforce any
provision of, or based on any right arising out of, this Agreement may be served
on any party anywhere in the world. Each party consents to service of process by
registered mail at the address to which notices are to be given pursuant to
Section 9.6. Nothing herein shall affect the right of a party to serve process
in any other manner permitted by applicable law. Each party further agrees that
final judgment against it in any such action or proceeding arising out of or
relating to this Agreement shall be conclusive and may be enforced in any other
jurisdiction within or outside

                                      -25-
<Page>

the United States of America by suit on the judgment, a certified or exemplified
copy of which shall be conclusive evidence of the fact and of the amount of its
liability.

     (c)     Each party agrees that it shall not, and that it shall instruct
those in its control not to, take any action to frustrate or prevent the
enforcement of any writ, decree, final judgment, award (arbitral or otherwise)
or order entered against it with respect to this Agreement, the XOMA Patent
Rights or the DYAX Patent Rights and shall agree to be bound thereby as if
issued or executed by a competent judicial tribunal having personal jurisdiction
situated in its country of residence or domicile.

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

                                      -26-
<Page>

     IN WITNESS WHEREOF, XOMA and DYAX have executed this Agreement in duplicate
originals by duly authorized officers.


DYAX CORP.                                                 XOMA IRELAND LIMITED


By: /s/ Jack Morgan                     By: /s/ Alan Kane
    ----------------------------            ------------------------------------
    Name: Jack Morgan                       Alan Kane, Director
    Title: Senior Vice President,           duly authorized for and on behalf of
           Corporate Development and        XOMA Ireland Limited in the presence
           Business Operations              of:


                                            /s/ Authorized Person
                                            ------------------------------------

                                      -27-
<Page>

                                  SCHEDULE 1.9

                               DYAX PATENT RIGHTS

<Table>
<Caption>
                        APPLICATION/
   COUNTRY               PATENT NO.        FILING DATE      PATENT NO.     ISSUE DATE
   -------              ------------       -----------      ----------     ----------
<S>                   <C>                   <C>              <C>             <C>
US                        07/664,989*           3/1/91       5,223,409        6/29/93

US                              9,319          1/26/93       5,403,484         4/4/95

US                         08/057,667          6/18/93       5,571,698        11/5/96

US div                     08/415,922           4/3/95       5,837,500       11/17/98

US div                     08/993,776         12/18/97

US div                     09/192,067         11/16/98

US div                     09/192,068         11/16/98

PCT                        US89/03731           9/1/89
                        W09002809 pub          3/22/90

EPO                       89/910702.3           9/1/89         436,597         4/2/97
                         EP436597 pub          7/17/91

EPO div                   96/112867.5           8/9/96         Allowed
                           768377 pub      4/16/97 pub

Japan                        89510087           9/1/89
                      JP4502700 (pub)          5/21/92

Canada                        610,176           9/1/89       1,340,288       12/29/98

Ireland                     IR89/2834           9/4/89

Israel                          91501           9/1/89           91501        6/11/98

Israel                         3 divs          5/29/97

PCT                        US92/01456          2/27/92
                      W09215677 (pub)          9/17/92

EPO                       92/908057.0          2/27/92

Canada                        2105300          2/27/92

Japan                        92507558          2/27/92
</Table>

<Page>

<Table>
<Caption>
                        APPLICATION/
   COUNTRY               PATENT NO.        FILING DATE      PATENT NO.     ISSUE DATE
   -------              ------------       -----------      ----------     ----------
<S>                   <C>                   <C>              <C>             <C>
PCT                        US92/01539          2/28/92
                            W09215679          9/17/92
                                (pub)

EPO                       92/908799.7          2/28/92

Canada                        2105303          2/28/92

Japan                        92508216          2/28/92
</Table>

* CIP of US SN487,063 filed 3/2/90 which is a CIP of US SN240,160 filed 9/2/88
All Protein Engineering Corporation patent rights have been assigned to Dyax
Corp.

                                       -2-
<Page>

                                  SCHEDULE 1.23

                               XOMA PATENT RIGHTS

TITLE:         MODULAR ASSEMBLY OF ANTIBODY GENES, ANTIBODIES PREPARED THEREBY
               AND USE

INVENTORS:     ROBINSON, LIU, HORWITZ, WALL, BETTER

1)   BASED ON PCT/US86/02269, WHICH IS A CONTINUATION-IN-PART OF U.S. SERIAL
     NO. 06/793,980 FILED NOVEMBER 1, 1985 (ABANDONED).

<Table>
<Caption>
     COUNTRY                SERIAL NO.                  PATENT NO.
     -------                ----------                  ----------
     <S>                    <C>                         <C>
     *United States         06/793,980
     Australia              65981/86                    Issued  606,320
     Canada                 521,909                     Abandoned
     Denmark                3385/87                     Pending
     Taiwan                 75105650                    Issued  51922
     *United States         U.S. National Phase of
                            PCT/US86/02269
</Table>

2)   BASED ON PCT/US88/02514, WHICH CORRESPONDS TO U.S. SERIAL NO. 07/077,528
     WHICH IS A CONTINUATION-IN-PART OF PCT/US86/02269 (ABANDONED), WHICH IS A
     CONTINUATION-IN-PART OF U.S. SERIAL NO. 06/793,980 (ABANDONED).

<Table>
<Caption>
     COUNTRY                SERIAL NO.                  PATENT NO.
     -------                ----------                  ----------
     <S>                    <C>                         <C>
     Australia              23244/88                    Issued   632,462
     Canada                 572,398                     Granted 1,341,235
     Denmark                192/90                      Pending
     Europe                 EP 88907510.7               Granted EP/0371998
                            EP 93100041.8               Granted EP/0550400
                            EP 95119798.7               Granted EP/0731167

     Austria
     Belgium
     France
     Germany
     Italy
     Luxembourg
     Netherlands
     Sweden
     Switzerland/
     Liechtenstein
     United Kingdom
</Table>

<Page>

<Table>
     <S>                    <C>                         <C>
     Japan                  506481/88                   Granted 2991720
     *United States         07/077,528
</Table>

* Cases abandoned in favor of a continuing application.

                                       -2-
<Page>

3)   BASED ON U.S. SERIAL NO. 07/501,092 FILED MARCH 29, 1990, WHICH IS A
     CONTINUATION-IN-PART OF U.S. SERIAL NO. 07/077,528 (MODULAR ASSEMBLY OF
     ANTIBODY GENES, ANTIBODIES PREPARED THEREBY AND USE; ROBINSON LIU, HORWITZ,
     WALL, BETTER) AND OF U.S. SERIAL NO. 07/142,039 (NOVEL PLASMID VECTOR WITH
     PECTATE LYASE SIGNAL SEQUENCE; LEI, WILCOX).

<Table>
<Caption>
     COUNTRY                SERIAL NO.                  PATENT NO.
     -------                ----------                  ----------
     <S>                    <C>                         <C>
     *United States         07/501,092
     *United States         07/987,555
     *United States         07/870,404
     *United States         08/020,671
     United States          08/235,225                  5,618,920
     United States          08/299,085                  5,595,898
     United States          08/357,234                  5,576,195
     United States          08/472,696                  5,846,818
     United States          08/472,691                  6,204,023
     United States          08/467,140                  5,698,435
     United States          08/450,731                  5,693,493
     United States          08/466,203                  5,698,417
     *United States         09/722,315
     United States          09/722,425
     United States          10/040,945
</Table>

TITLE:     ARAB PROMOTERS AND METHOD OF PRODUCING POLYPEPTIDES, INCLUDING
           CECROPINS, BY MICROBIOLOGICAL TECHNIQUES

INVENTORS: LAI, LEE, LIN, RAY, WILCOX

           BASED ON PCT/US86/00131 WHICH IS A CONTINUATION-IN-PART OF U.S.
           SERIAL NO. 06/695,309 FILED JANUARY 28, 1985 (ABANDONED)

<Table>
<Caption>
     COUNTRY                SERIAL NO.                  PATENT NO.
     -------                ----------                  ----------
     <S>                    <C>                         <C>
     Europe                 EP 86900983.7               Granted EP/0211047
       Austria
       Belgium
       France
       Germany
       Italy
       Luxembourg
       Netherlands
       Sweden
       Switzerland/
        Liechtenstein
       United Kingdom
</Table>

                                       -3-
<Page>

<Table>
     <S>                    <C>                         <C>
     Finland                863891                      Granted 94774
     Japan                  500818/86                   Granted 2095930
     Japan                  094753/94                   Granted 2121896
     Norway                 863806                      Granted 175870
     *United States         06/695,309
     *United States         06/797,472
     United States          07/474,304                  Granted 5,028,530
</Table>

* Cases abandoned in favor of a continuing application.

                                       -4-
<Page>

TITLE:     NOVEL PLASMID VECTOR WITH PECTATE LYASE SIGNAL SEQUENCE

INVENTORS: LEI, WILCOX

           BASED ON U.S. SERIAL NO. 07/142,039 FILED JANUARY 11, 1988 AND
           PCT/US89/00077

<Table>
<Caption>
     COUNTRY                SERIAL NO.                  PATENT NO.
     -------                ----------                  ----------
     <S>                    <C>                         <C>
     Australia              29377/89                    Issued/627443
     Canada                 587,885                     1,338,807
     Europe                 EP 89901763.6               Granted EP/0396612
      Austria
      Belgium
      France
      Germany
      Italy
      Luxembourg
      Netherlands
      Sweden
      Switzerland/
       Liechtenstein
      United Kingdom
     Japan                  501661/89                   Granted 2980626
     *United States         07/142,039
</Table>

                                       -5-
<Page>

                                        CONFIDENTIAL MATERIALS OMITTED AND FILED
                                        SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

                                  SCHEDULE 2.2

     [*****]


                   [Redacted portions consist of one page.]


<Page>

                                  SCHEDULE 2.5

                                 FORM OF NOTICE

XOMA owns a number of patents covering various aspects of bacterial antibody
expression and phage display.

XOMA has licensed these patents on a non-exclusive basis to DYAX.

Under the license agreement with XOMA:

-    DYAX cannot provide phage display services or transfer phage display
     materials, products or information to you without first showing you a
     redacted copy of its license from XOMA and this notice.

-    If you and DYAX enter into a written agreement by which you become a "DYAX
     Collaborator," then you will be permitted to use DYAX phage display
     services, DYAX phage display materials, products and information to
     research, develop and commercialize antibody products.

-    Collaborators do not, however, have the right to produce commercial
     quantities of such antibodies using XOMA's patented technology. Rather,
     collaborators only have the right to make research and development
     quantities of antibodies using the XOMA patent rights. Thereafter, unless
     the collaborator obtains a commercial production license from XOMA (which
     may be available), the collaborator must produce commercial quantities of
     antibodies using a method that does not infringe XOMA patent rights.

-    Therefore, if you and DYAX enter into a written agreement, that agreement
     must contain certain provisions specified in the license agreement with
     XOMA, including:

          -    Terms pursuant to which you, as the recipient of any transferred
               materials, would agree to abide by each of the limitations,
               restrictions and other obligations provided for by the license
               agreement with XOMA, including, without limitation, the
               restrictions on use of such transferred materials for purposes
               other than research and development.

          -    A covenant not to use transferred materials for any purpose other
               than for research and development purposes otherwise authorized
               by the license agreement with XOMA.

          -    A provision that the "first sale" doctrine does not apply to any
               disposition of transferred materials.

<Page>

          -    An agreement by you to further dispose of transferred materials
               only to a third party who otherwise meets the definition of a
               "DYAX Collaborator" set forth in the license agreement with XOMA
               and who executes a written agreement in which it undertakes all
               of the obligations applied to the transferring party.

                                       -2-
<Page>

                                        CONFIDENTIAL MATERIALS OMITTED AND FILED
                                        SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

                                  SCHEDULE 2.9

     [*****]


                   [Redacted portions consist of three pages.]


<Page>

                                        CONFIDENTIAL MATERIALS OMITTED AND FILED
                                        SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION. ASTERISKS DENOTE
                                        SUCH OMISSION.

                                  SCHEDULE 3.3

     [*****]


                   [Redacted portions consist of one page.]


<Page>

                                  SCHEDULE 5.4

                                  PRESS RELEASE

XOMA CONTACT:                             DYAX CONTACT:
Laura Zobkiw, Corporate Communications    Jack Morgan, Senior Vice President,
                                          Corporate Development and Business
                                          Operations
Tel: (510) 204-7200                       Tel: (617) 250-5762
Email: Investorrelations@xoma.com         Email: jmorgan@dyax.com


                XOMA and Dyax Cross-License Antibody Technologies
                - Dyax Becomes Third Licensee of XOMA Technology
                       Among Antibody Library Companies -


BERKELEY, CA AND CAMBRIDGE, MA - OCTOBER 16, 2002 - XOMA Ltd. (Nasdaq: XOMA) and
Dyax Corp. (Nasdaq: DYAX) announced today they have entered into a
cross-licensing agreement for antibody-related technologies. Under the
agreement, Dyax receives a license to use XOMA's antibody expression technology
for developing antibody products for itself and for Dyax collaborators. Dyax
also receives a license for the production of antibodies under the XOMA patents.
XOMA will receive license and royalty payments from Dyax in addition to a Dyax
antibody library and a license to Dyax's phage display patents known as the
Ladner patents.

The agreement also provides for a release of Dyax and its collaborators from
claims under the XOMA patents arising from any past activities using Dyax
technology to the extent they also used XOMA's antibody expression technology
and allows Dyax to use the XOMA technology in combination with its own
technology in any future collaborations.

"We are very pleased to enter into this antibody related licensing arrangement
with Dyax, a company with excellent capabilities in the important field of
antibody discovery and selection," said Jack Castello, Chairman, President and
Chief Executive Officer, XOMA Ltd. "Our license to Dyax, being the third such
license this year with a significant antibody library company, further validates
the fundamental position our antibody expression technology holds in the phage
display arena. We are also pleased to expand our target discovery and
therapeutic

<Page>

antibody development capabilities with the Dyax antibody library and
a license to the Ladner patents, which are fundamental to the practice of
antibody phage display."

"Through this agreement, Dyax is pleased to add XOMA's bacterial antibody
expression technology to the package of technology and services we are able to
provide to our current and future antibody technology customers," said Henry E.
Blair, Chairman and CEO of Dyax Corp. "We are especially pleased to gain access
to this key technology for Dyax's internal therapeutic product development and
manufacturing programs."

ABOUT XOMA AND ITS ANTIBODY EXPRESSION TECHNOLOGY

Bacterial antibody expression is an enabling technology used to discover and
screen, as well as develop and manufacture, recombinant antibodies for
commercial purposes. Expression of antibodies by phage display technology
depends upon the expression and secretion of antibody domains from bacteria as
properly folded, functional proteins. XOMA scientists were the first to
demonstrate the secretion of antibody domains directly from bacterial cells as
fully functional, properly folded molecules. XOMA has received six U.S. patents
to date that broadly cover the secretion of functional immunoglobulins from
bacteria, including antibody fragments such as Fab and single-chain antibodies.
Corresponding foreign patents have also been granted. Access to XOMA's patent
estate is necessary for the practice of antibody phage display and other
antibody screening applications.

XOMA develops and manufactures innovative biopharmaceuticals for disease targets
that include cancer, immunological and inflammatory disorders, and infectious
diseases. XOMA's programs include collaborations with: Genentech, Inc. on the
Raptiva(TM) antibody for psoriasis (Phase III), rheumatoid arthritis (Phase II)
and other indications; Onyx Pharmaceuticals, Inc. to develop and manufacture its
ONYX-015 product for various cancers (Phase II and III); Baxter Healthcare
Corporation to develop NEUPREX(R) (rBPI-21) for Crohn's disease (Phase II) and
other indications; and Millennium Pharmaceuticals, Inc. on two biotherapeutic
agents for certain vascular inflammation indications (preclinical).
Earlier-stage development programs include compounds to treat cancer,
retinopathies, autoimmune diseases and infections. For more information about
XOMA's pipeline and activities, please visit XOMA's web site at www.xoma.com.

ABOUT DYAX AND ITS PHAGE DISPLAY TECHNOLOGY
Dyax's Ladner patents have the earliest priority date for phage display patents
in the United States and are the core patents in phage display technology. With
4 granted patents in the United States, Dyax has over 60 licensees to the Ladner
patents, making this patent licensing program one of the most successful in the
biotechnology industry. Access to the Ladner pat-

                                       -2-
<Page>

ents is necessary to the practice of any display technology, including the
display of antibodies, peptides, and proteins on any cell, spore, or virus,
including bacteriophage.

Dyax Corp. is a biopharmaceutical company focused on the discovery, development
and commercialization of therapeutic products. The Company uses its patented
phage display technology to rapidly identify a broad range of protein, peptide,
and antibody compounds that bind with high affinity and high specificity to
targets of interest, with the objective of selecting those compounds with the
greatest potential for advancement into clinical development. Dyax currently has
two recombinant proteins in phase I and II clinical trials. DX-88 is being
studied in two indications (hereditary angioedema and cardiopulmonary bypass),
while DX-890 is being studied for cystic fibrosis. Dyax leverages its technology
broadly through licenses and collaborations in therapeutics and in non-core
areas of affinity separations, diagnostics and imaging, and research reagents.
Through its subsidiary, Biotage, Inc., Dyax develops, manufactures and sells
chromatography separations systems and products worldwide for drug discovery and
purification.

AS TO XOMA: STATEMENTS MADE IN THIS NEWS RELEASE RELATED TO COLLABORATIVE
ARRANGEMENTS AND DEVELOPMENT CAPABILITIES, OR THAT OTHERWISE RELATE TO FUTURE
PERIODS, ARE FORWARD-LOOKING STATEMENTS WITHIN THE MEANING OF SECTION 27A OF THE
SECURITIES ACT OF 1933 AND SECTION 21E OF THE SECURITIES EXCHANGE ACT OF 1934.
THESE STATEMENTS ARE BASED ON ASSUMPTIONS THAT MAY NOT PROVE ACCURATE. ACTUAL
RESULTS COULD DIFFER MATERIALLY FROM THOSE ANTICIPATED DUE TO CERTAIN RISKS
INHERENT IN THE BIOTECHNOLOGY INDUSTRY AND FOR COMPANIES ENGAGED IN THE
DEVELOPMENT OF NEW PRODUCTS IN A REGULATED MARKET. THESE RISKS, INCLUDING THOSE
RELATED TO CHANGES IN THE STATUS OF EXISTING COLLABORATIVE RELATIONSHIPS, THE
AVAILABILITY OF FUTURE COLLABORATIVE RELATIONSHIPS, THE ABILITY OF COLLABORATORS
AND OTHER PARTNERS TO MEET THEIR OBLIGATIONS, THE TIMING OR RESULTS OF PENDING
OR FUTURE CLINICAL TRIALS, MARKET DEMAND FOR PRODUCTS, ACTIONS BY THE FOOD AND
DRUG ADMINISTRATION OR THE US PATENT AND TRADEMARK OFFICE, AND UNCERTAINTIES
REGARDING THE STATUS OF BIOTECHNOLOGY PATENTS, ARE DISCUSSED IN XOMA'S MOST
RECENT ANNUAL REPORT ON FORM 10-K AND IN OTHER SEC FILINGS. CONSIDER SUCH RISKS
CAREFULLY IN EVALUATING XOMA'S PROSPECTS.

AS TO DYAX: THIS PRESS RELEASE CONTAINS FORWARD-LOOKING STATEMENTS, INCLUDING
STATEMENTS REGARDING COLLABORATIVE ARRANGEMENTS AND DYAX'S TECHNOLOGY.
STATEMENTS THAT ARE NOT HISTORICAL FACTS ARE BASED ON DYAX'S CURRENT
EXPECTATIONS, BELIEFS, ASSUMPTIONS, ESTIMATES, FORECASTS AND PROJECTIONS ABOUT
THE INDUSTRY AND MARKETS IN WHICH DYAX COMPETES. THE STATEMENTS CONTAINED IN
THIS RELEASE ARE NOT GUARANTEES OF FUTURE PERFORMANCE AND INVOLVE CERTAIN RISKS,
UNCERTAINTIES AND ASSUMPTIONS, WHICH ARE DIFFICULT TO PREDICT. THEREFORE, ACTUAL
OUTCOMES AND RESULTS MAY DIFFER MATERIALLY FROM WHAT IS EXPRESSED IN SUCH
FORWARD-LOOKING STATEMENTS. IMPORTANT FACTORS WHICH MAY AFFECT DYAX'S
COLLABORATIVE ARRANGEMENTS AND ITS TECHNOLOGY IN-

                                       -3-
<Page>

CLUDE THE RISKS THAT DYAX MAY NOT BE ABLE TO OBTAIN AND MAINTAIN INTELLECTUAL
PROPERTY PROTECTION FOR ITS PRODUCTS AND TECHNOLOGIES; OTHERS MAY DEVELOP
TECHNOLOGIES OR PRODUCTS SUPERIOR TO DYAX'S TECHNOLOGIES OR PRODUCTS; AND OTHER
RISK FACTORS DESCRIBED OR REFERRED TO IN DYAX'S MOST RECENT ANNUAL REPORT ON
FORM 10-K AND OTHER PERIODIC REPORTS FILED WITH THE SECURITIES AND EXCHANGE
COMMISSION. DYAX CAUTIONS INVESTORS NOT TO PLACE UNDUE RELIANCE ON THE
FORWARD-LOOKING STATEMENTS CONTAINED IN THIS RELEASE. THESE STATEMENTS SPEAK
ONLY AS OF THE DATE OF THIS RELEASE, AND DYAX UNDERTAKES NO OBLIGATIONS TO
UPDATE OR REVISE THESE STATEMENTS, EXCEPT AS MAY BE REQUIRED BY LAW. DYAX AND
THE DYAX LOGO ARE THE REGISTERED TRADEMARKS OF DYAX CORP.

                                      # # #