Exhibit 10.33


               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

         This Agreement dated as of February 12, 2001 is among DYAX CORP.
(formerly known as Biotage, Inc.), a Delaware corporation (the "COMPANY"), and
certain stockholders of the Company that are signatories hereto (including for
this purpose certain stockholders who have agreed in writing to be bound by the
terms of this Agreement).

                                 R E C I T A L S

         This Agreement amends and restates in its entirety the Amended and
Restated Registration Rights Agreement dated as of August 31, 1998 among the
Company and certain of such stockholders, as the same has been amended from time
to time prior to the date hereof (the "PRIOR AGREEMENT").

         Most stockholders of the Company who were parties to the Prior
Agreement have had their registration rights terminated thereunder because they
are eligible to sell all of their Registrable Shares pursuant to Rule 144 under
the Securities Act and, therefore, they no longer need to be parties to this
Agreement.

         Each Stockholder (as defined below) owns that number of Registrable
Shares (as defined below) of common stock, par value $0.01 per share of the
Company (the "COMMON STOCK") set forth opposite the name of such Stockholder on
SCHEDULE I hereto.

         The Company and the Stockholders (as defined below) deem it to be in
their respective best interests to set forth the rights of the Stockholders in
connection with public offerings and sales of the Common Stock.

         NOW, THEREFORE, in consideration of the premises and mutual covenants
and obligations hereinafter set forth, the Company and the Stockholders hereby
agree as follows:

         SECTION 1. CERTAIN DEFINITIONS.

         As used in this Agreement, the following terms have the following
respective meanings:

         "COMMISSION" means the Securities and Exchange Commission, or any other
Federal agency at the time administering the Securities Act and/or the Exchange
Act.

         "EXCHANGE ACT" means the Securities Exchange Act of 1934 or any similar
Federal statute, and the rules and regulations of the Commission issued under
such Act, as they each may, from time to time, be in effect.

         "INITIAL PUBLIC OFFERING" shall mean the closing of the first fully
underwritten, firm commitment public offering pursuant to an effective
Registration Statement covering the offer and sale by the Company of its Common
Stock, resulting in aggregate net proceeds to the Company (after deducting
underwriting discounts and commissions) of at least $20,000,000 and at a per
share price of at least $10.00 per share, which occurred on August 18, 2000.





         "REGISTRABLE SHARES" means (i) the shares of Common Stock listed on
SCHEDULE I hereto, and (ii) any other shares of Common Stock of the Company
issued or issuable in respect of such shares of Common Stock (because of stock
splits, stock dividends, reclassifications, recapitalizations or similar
events); PROVIDED, HOWEVER, that such shares shall no longer be deemed to be
Registrable Shares under this Agreement when any Stockholder ceases to have
rights hereunder pursuant to Section 15 hereof.

         "REGISTRATION EXPENSES" has the meaning ascribed thereto in Section 5.

         "REGISTRATION STATEMENT" means a registration statement filed by the
Company with the Commission for a public offering and sale of securities of the
Company (other than a registration statement on Form S-8 or Form S-4, or their
successors, or any other form for a limited purpose, or any registration
statement covering only securities proposed to be issued in exchange for
securities or assets of another corporation).

         "SECURITIES ACT" means the Securities Act of 1933 or any similar
Federal statute, and the rules and regulations of the Commission issued under
such Act, as they each may, from time to time, be in effect.

         "STOCKHOLDERS" means, individually and collectively, all stockholders
(or any of them) of the Company that are listed on SCHEDULE I hereto, and any
persons or entities to whom the rights granted under this Agreement are
transferred by such stockholders (or any of them), and their successors or
assigns to the extent permitted by Section 14 hereof; PROVIDED, HOWEVER, that
such persons shall only continue to be Stockholders hereunder and parties to
this Agreement for as long as they hold Registrable Shares.

         SECTION 2. REQUIRED REGISTRATIONS.

         (a) Commencing on the first anniversary of the closing of the Initial
Public Offering of the Company, a Stockholder or Stockholders holding in the
aggregate at least 50% of the Registrable Shares or stockholders holding in the
aggregate at least 50% of the Common Stock issued upon conversion of the
Company's Class A Series 5 Preferred Stock (the "SERIES 5 STOCK"), may request,
in writing, that the Company effect the registration on Form S-1 or Form SB-2
(or any successor forms) Registrable Shares having an anticipated net aggregate
offering price in excess of $5,000,000 (after deducting underwriting discounts
and commissions). Any demand registration pursuant to this Section 2 must be
underwritten on a firm commitment basis and the right of other Stockholders to
participate shall be conditioned on such Stockholders' participation in such
underwriting upon the same terms and conditions. Upon receipt of any such
request, the Company shall promptly give written notice of such proposed
registration to all Stockholders. Such Stockholders shall have the right, by
giving written notice to the Company within 30 days after the Company provides
its notice, to elect to have included in such registration such of their
Registrable Shares as such Stockholders may request in such notice of election,
subject to the approval of the underwriter managing the offering. Thereupon, the
Company shall, as expeditiously as possible, use its best efforts to effect the
registrations, on Form S-1 or Form SB-2 (or any successor form), of all
Registrable Shares which the Company has been requested to so register.


                                       2



         (b) At any time after the Company becomes eligible to file a
Registration Statement on Form S-3 (or any successor form relating to secondary
offerings), a Stockholder or Stockholders holding in the aggregate Registrable
Shares having a market value of $1,000,000, may request the Company, in writing,
to effect the registration on Form S-3 (or any successor form), of all or such
portion of the Registrable Shares as such holder or holders shall specify. Upon
receipt of any such request, the Company shall promptly give written notice of
such proposed registration to all Stockholders. Such Stockholders shall have the
right, by giving written notice to the Company within 30 days after the Company
provides its notice, to elect to have included in such registration such of
their Registrable Shares as such Stockholders may request in such notice of
election. Thereupon, the Company shall, as expeditiously as possible, use its
best efforts to effect the registration on Form S-3 (or any successor form) of
all Registrable Shares which the Company has been so requested to register.

         (c) The Company shall not be required to effect more than two
registrations pursuant to paragraph (a) above provided however the holders of
Common Stock issued upon conversion of the Company's Series 5 Stock (the "SERIES
5 STOCKHOLDERS") shall be entitled to demand the filing of a registration
statement pursuant to paragraph (a) above on not less than two occasions whether
or not they have included any of their Registrable Shares in prior Registration
Statements filed as a result of the demand by other Stockholders pursuant to
paragraph (a) above. Unless otherwise requested by the selling Stockholders, a
registration pursuant to paragraph (a) above shall not count as one of the
permitted registrations until it has become effective. Unless otherwise
requested by the selling Stockholders, the last registration pursuant to
paragraph (a) above shall not count as one of the permitted registrations unless
the holders of Registrable Shares are able to register and sell at least ninety
percent (90%) of the Registrable Shares requested to be included in such
registration. In addition, the Company shall not be required to effect any
registration (other than on Form S-3 or any successor form relating to secondary
offerings) within six months after the effective date of any other Registration
Statement of the Company. Under paragraph (b) above, the Stockholder or
Stockholders holding in the aggregate Registrable Shares having a market value
of $1,000,000 shall have the right to require the Company to effect an unlimited
number of registrations on Form S-3, however, in any one year the Company shall
not be required to effect more than one such registration on Form S-3, and any
such registration on Form S-3 shall be separated from any previous registration
by a period of at least six months.

         (d) If at the time of any request to register Registrable Shares
pursuant to this Section 2, the Company is engaged or has firm plans to engage
within 90 days of the time of the request in a registered public offering as to
which the Stockholders may include Registrable Shares pursuant to Section 3 or
is engaged in any other activity which, in the good faith determination of the
Company's Board of Directors, would be adversely affected by the requested
registration to the material detriment of the Company, then the Company may at
its option direct that such request be delayed for a period not in excess of one
hundred twenty (120) days from the effective date of such offering or the date
of commencement of such other material activity, as the case may be, such right
to delay a request to be exercised by the Company not more than once.


                                       3



         SECTION 3. INCIDENTAL REGISTRATION.

         (a) Whenever the Company proposes to file a Registration Statement
(other than pursuant to Section 2), it will, prior to such filing, give written
notice to all Stockholders of its intention to do so and, upon the written
request of a Stockholder or Stockholders given within 10 days after the Company
provides such notice (which request shall state the intended method of
disposition of such Registrable Shares), the Company shall use its best efforts
to cause all Registrable Shares which the Company has been requested to register
to be registered under the Securities Act to the extent necessary to permit
their sale or other disposition in accordance with the intended methods of
distribution specified in the request of such Stockholder(s); provided that the
Company shall have the right to postpone or withdraw any registration effected
pursuant to this Section 3 without obligation to any Stockholder.

         (b) In connection with any offering under this Section 3 involving an
underwriting, the Company shall not be required to include any Registrable
Shares in such underwriting unless the holders thereof accept the terms of the
underwriting as agreed upon between the Company and the underwriters selected by
it, and then only in such quantity as will not, in the opinion of the
underwriters, jeopardize the success of the offering by the Company. If in the
Opinion of the managing underwriter the registration of all, or part of, the
Registrable Shares which the holders have requested to be included would
materially and adversely affect such public offering, then the Company shall be
required to include in the underwriting only that number of Registrable Shares,
if any, which the managing underwriter believes may be sold without causing such
adverse effect. In the event of such a reduction in the number of shares to be
included in the underwriting, all shares other than Registrable Shares shall be
excluded from the underwriting before any Registrable Shares are excluded from
the underwriting and the holders of Registrable Shares who have requested
registration shall participate in the underwriting pro rata based upon their
total ownership of Registrable Shares (or in any other proportion as agreed upon
by such holders) and if any holder would thus be entitled to include more shares
than such holder requested to be registered, the excess shall be allocated among
other requesting holders pro rata based on their ownership of Registrable
Shares.

         SECTION 4. REGISTRATION PROCEDURES. If and whenever the Company is
required by the provisions of this Agreement to use its best efforts to effect
the registration of any of the Registrable Shares under the Securities Act, the
Company shall:

         (a) provide to the selling Stockholders drafts of the Registration
Statement and an opportunity to comment thereon and participate in the
preparation thereof prior to filing the Registration Statement with the
Commission;

         (b) file with the Commission the Registration Statement and use its
best efforts to cause the Registration Statement to become and remain effective;

         (c) as expeditiously as possible prepare and file with the Commission
any amendments and supplements to the Registration Statement and the prospectus
included in the Registration Statement as may be necessary to keep the
Registration Statement effective for a period of not less than 120 days from the
effective date;


                                       4



         (d) as expeditiously as possible furnish to each selling Stockholder
such reasonable numbers of copies of the prospectus, including a preliminary
prospectus, in conformity with the requirements of the Securities Act, and such
other documents as the selling Stockholders may reasonably request in order to
facilitate the public sale or other disposition of the Registrable Shares owned
by the selling Stockholders;

         (e) as expeditiously as possible use its best efforts to register or
qualify the Registrable Shares covered by the Registration Statement under the
securities or blue sky laws of such states as the selling Stockholders shall
reasonably request, and do any and all other acts and things that may be
necessary or desirable to enable the selling Stockholders to consummate the
public sale or other disposition in such jurisdictions of the Registrable Shares
owned by the selling Stockholders; PROVIDED, HOWEVER, that the Company shall not
be required in connection with this paragraph (e) to qualify as a foreign
corporation or execute a general consent to service of process in any
jurisdiction; and

         (f) obtain for the selling Stockholders such opinions of counsel to the
Company or comfort letters from the Company's accountants, addressed to the
selling Stockholders, as may be deemed reasonably requested by the selling
Stockholders holding a majority of the Registrable Shares included in the
Registration Statement.

         If the Company has delivered preliminary or final prospectuses to the
selling Stockholders and after having done so the prospectus is amended to
comply with the requirements of the Securities Act, the Company shall promptly
notify the selling Stockholders and, if requested, the selling Stockholders
shall immediately cease making offers of Registrable Shares and shall return all
prospectuses to the Company. The Company shall promptly provide the selling
Stockholders with revised prospectuses and, following receipt of the revised
prospectuses, the selling Stockholders shall be free to resume making offers of
the Registrable Shares.

         SECTION 5. ALLOCATION OF EXPENSES. The Company shall pay the
Registration Expenses for the registrations requested by the Stockholders
pursuant to Section 2 of this Agreement and of all registrations pursuant to
Section 3 of this Agreement. If a registration requested by the Stockholders
pursuant to paragraph (a) of Section 2 is withdrawn at the request of the
Stockholders requesting it (other than as a result of information concerning the
business or financial condition of the Company which is made known to the
Stockholders after the date on which such registration was requested) and if the
requesting Stockholders elect not to have such registration counted as a
registration requested under paragraph (a) of Section 2, the requesting
Stockholders shall pay the Registration Expenses of such registration pro rata
in accordance with the number of their Registrable Shares previously proposed to
be included in such registration. For purposes of this Agreement, the term
"Registration Expenses" shall mean all expenses incurred by the Company in
complying with this Agreement, including, without limitation, all registration
and filing fees, exchange listing fees, printing expenses, fees and
disbursements of counsel for the Company and one counsel for the selling
Stockholders, state blue sky fees and expenses, and the expense of any special
audits incident to or required by any such registration, but excluding
underwriting discounts and selling commissions. Such underwriting discounts and
selling commissions shall be borne pro rata by the selling Stockholders in
accordance with the number of their Registrable Shares included in such
registration.


                                       5



         SECTION 6. INDEMNIFICATION. In the event of any registration of any of
the Registrable Shares under the Securities Act pursuant to this Agreement, the
Company will indemnify and hold harmless the seller of such Registrable Shares,
each underwriter of such Registrable Shares and each other person if any, who
controls such seller or underwriter within the meaning of the Securities Act or
the Exchange Act against any losses, claims, damages or liabilities, joint or
several, to which such seller, underwriter or controlling person may become
subject under the Securities Act, the Exchange Act, state securities laws or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any Registration Statement
under which such Registrable Shares were registered under the Securities Act,
any preliminary prospectus or final prospectus contained in such Registration
Statement, or any amendment or supplement to such Registration Statement, or
arise out of or are based upon the omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading, and the Company will reimburse such seller, underwriter
or controlling person for any legal or any other expenses reasonably incurred by
such seller, underwriter or controlling person, respectively, in connection with
investigating or defending any such loss, claim, damage, liability or action;
PROVIDED, HOWEVER, that the Company will not be liable in any such case to the
extent that any such loss, claim, damage or liability arises out of or is based
upon any untrue statement or omission made in such Registration Statement,
preliminary prospectus or prospectus, or any such amendment or supplement, in
reliance upon and in conformity with information furnished to the Company, in
writing, by or on behalf of such seller, underwriter or controlling person
specifically for use in the preparation thereof.

         In the event of any registration of any of the Registrable Shares under
the Securities Act pursuant to this Agreement, each seller of Registrable Shares
included in such registration, severally and not jointly, will indemnify and
hold harmless the Company, each of its directors and officers and each
underwriter (if any) and each person, if any, who controls the Company or any
such underwriter within the meaning of the Securities Act or the Exchange Act,
against any losses, claims, damages or liabilities, joint or several, to which
the Company, such directors and officers, underwriter or controlling persons may
become under the Securities Act, Exchange Act, state securities laws or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of a material fact contained in any Registration Statement
under which such Registrable Shares were registered under the Securities Act,
any preliminary prospectus or final prospectus contained in the Registration
Statement, or any amendment or supplement to the Registration Statement, or
arise out of or are based upon any omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading, if the statement or omission was made in reliance upon
and in conformity with information furnished in writing to the Company by or on
behalf of such seller, specifically for use in connection with the preparation
of such Registration Statement, prospectus, amendment or supplement; PROVIDED,
HOWEVER, that the obligations of such seller hereunder shall be limited to an
amount equal to the proceeds to such seller from Registrable Shares sold in such
registration. Indemnification of any underwriter pursuant to this Section 6
shall not be interpreted as providing relief of such underwriter from any or all
of its due diligence obligations. Further, an underwriter shall not be entitled
to indemnification pursuant to this subsection in the event that it fails to
deliver to any selling Stockholder any preliminary or final or revised
prospectus, as


                                       6



required by the Rules and Regulations of the Commission. Finally, in the event
that any error in a preliminary prospectus of the Company is subsequently
corrected in the final prospectus of the Company for a particular offering, no
indemnification shall be provided pursuant to this Section unless the Company
has provided the seller of Registrable Shares against whom indemnification is
sought with sufficient copies of the final prospectus and any amendments and
supplements thereto in accordance with the Company's obligations under Section 4
of this Agreement.

         Each party entitled to indemnification under this Section 6 (the
"INDEMNIFIED PARTY") shall give notice to the party required to provide
indemnification (the "INDEMNIFYING PARTY") promptly after such Indemnified Party
has actual knowledge of any claim as to which indemnity may be sought, and shall
permit the Indemnifying Party to assume the defense of any such claim or any
litigation resulting therefrom; PROVIDED, that counsel for the Indemnifying
Party, who shall conduct the defense of such claim or litigation, shall be
approved by the Indemnified Party (whose approval shall not be unreasonably
withheld); and, PROVIDED, FURTHER, that the failure of any Indemnified Party to
give notice as provided herein shall not relieve the Indemnifying Party of its
obligations under this Agreement. The Indemnified Party may participate in such
defense at such party's expense; PROVIDED, HOWEVER, that the Indemnifying Party
shall pay such expense if representation of such Indemnified Party by the
counsel retained by the Indemnifying Party would be inappropriate due to actual
or potential differing interests between the Indemnified Party and any other
party represented by such counsel in such proceeding. No Indemnifying Party, in
the defense of any such claim or litigation shall, except with the consent of
each Indemnified Party, consent to entry of any judgment or enter into any
settlement which does not include as an unconditional term thereof the giving by
the claimant or plaintiff to such Indemnified Party of a release from all
liability in respect of such claim or litigation, and no Indemnified Party shall
consent to entry of any judgment or settle such claim or litigation without the
prior written consent of the Indemnifying Party.

         Except to the extent otherwise provided above, if the indemnification
provided for in this Section 6 is for any reason unavailable or insufficient to
hold harmless an indemnified party then each such indemnifying party in lieu of
indemnifying such indemnified party, shall contribute to the amount paid or
payable by such indemnified party as a result of the losses, claims, damages,
judgments or liabilities referred to above (i) in such proportion as is
appropriate to reflect the relative benefits received by the Company, the
holders of Registrable Shares and the underwriters from the offering of the
shares or (ii) if the allocation provided by clause (i) above is not permitted
by applicable law, in such proportion as is appropriate to reflect not only the
relative benefits referred to in clause (i) above but also the relative fault of
the Company, the holders of Registrable Shares and the underwriters in
connection with the statement or omission which resulted in such losses, claims,
damages, judgments or liabilities, as well as any other relevant equitable
considerations. The relative benefits received by the Company, the holders of
Registrable Shares and the underwriters shall be deemed to be in the same
proportion as the total net proceeds from the offering of the shares (before
deducting expenses) received by the Company and the holders of Registrable
Shares and the total underwriting discounts and commissions received by the
underwriters bear to each other. The relative fault of the Company, the holders
of Registrable Shares and the underwriters shall be determined by reference to,
among other things, whether the untrue or alleged untrue statement of a material
fact or the omission or alleged omission to state a material fact relates to
information supplied by the Company, the holder of Registrable Shares or the
underwriters and that party's relative intent,


                                       7



knowledge, access to information and opportunity to correct or prevent such
untrue statements or omissions.

         SECTION 7. INDEMNIFICATION WITH RESPECT TO UNDERWRITTEN OFFERING. In
the event that Registrable Shares are sold pursuant to a Registration Statement
in an underwritten offering pursuant to Section 2, the Company agrees to enter
into an underwriting agreement containing customary representations and
warranties with respect to the business and operations of an issuer of the
securities being registered and customary covenants and agreements to be
performed by such issuer, including without limitation customary provisions with
respect to indemnification by the Company of the underwriters of such offering.

         SECTION 8. INFORMATION BY HOLDER. Each holder of Registrable Shares
included in any registration shall furnish to the Company such information
regarding such holder and the distribution proposed by such holder as the
Company may request in writing and as shall be required in connection with any
registration, qualification or compliance referred to in this Agreement.

         SECTION 9. "STAND-OFF" AGREEMENT. Stockholders, if requested by the
Company and an underwriter of Common Stock or other securities of the Company,
shall agree not to sell or otherwise transfer or dispose of any Registrable
Shares of the Company held by such Stockholder for a specified period of time
(not to exceed 180 days) following the effective date of a Registration
Statement; PROVIDED THAT, all Stockholders holding more than five percent of the
outstanding Common Stock and all officers and directors of the Company enter
into similar agreements. Such agreement shall be in writing in a form
satisfactory to the Company and such underwriter. The Company may impose
stop-transfer instructions with respect to the Registrable Shares or other
securities subject to the foregoing restriction until the end of the stand-off
period.

         SECTION 10. RULE 144 REQUIREMENTS. With a view to making available to
the Stockholders the benefits of Rule 144 promulgated under the Securities Act
and any other rule or regulation of the Commission that may at any time permit a
Stockholder to sell securities of the Company to the public without
registration, the Company agrees to use its best efforts to:

         (a) make and keep public information available, as those terms are
understood and defined in Rule 144 under the Securities Act;

         (b) use its best efforts to file with the Commission in a timely manner
all reports and other documents required of the Company under the Securities Act
and the Exchange Act (at any time after it has become subject to such reporting
requirements); and

         (c) furnish to any holder of Registrable Shares upon request a written
statement by the Company as to its compliance with the reporting requirements of
said Rule 144 (at any time after 90 days after the closing of the first sale of
securities by the Company pursuant to a Registration Statement), and of the
Securities Act and the Exchange Act (at any time after it has become subject to
such reporting requirements), a copy of the most recent annual or quarterly
report of the Company, and such other reports and documents of the Company as
such holder may reasonably request to avail itself of said Rule 144 or any
similar rule or regulation of the Commission allowing it to sell any such
securities without registration.


                                       8



         SECTION 11. SELECTION OF UNDERWRITER. In the case of any registration
effected pursuant to Section 2, the requesting Stockholders shall have the right
to designate the managing underwriter, subject to the approval of the Company,
which approval may not be unreasonably withheld or delayed.

         SECTION 12. NO CONFLICT OF RIGHTS. The Company shall not, after the
date hereof, grant any registration rights which would adversely affect or
impair the registration rights granted hereby.

         SECTION 13. SUCCESSORS AND ASSIGNS. Except as provided in Section 14
hereof, the provisions of this Agreement shall be binding upon and inure to the
benefit of, the respective successors, assigns, heirs, executors and
administrators of the parties hereto.

         SECTION 14. ASSIGNMENT. (a) The rights granted to the Stockholders
under this Agreement may not be transferred except to (i) a member of such
Stockholder's immediate family or a trust for the exclusive benefit of one or
more persons who are members of such Stockholder's immediate family, either
during the lifetime of such Stockholder or in death by will or intestacy or (ii)
any transferee or successor who is (x) a general or limited partner, officer or
other affiliate of such Stockholder or any other affiliate of the Company
(regardless of whether such transferee is a direct or indirect competitor of the
Company) or (y) who acquires at least 80,000 Registrable Shares (equitably
adjusted to reflect stock splits, dividends, combinations and like adjustments)
(or such lesser number of shares as may constitute such Stockholder's entire
holding of Registrable Shares) and who is not directly or indirectly a
competitor of the Company or a partner, officer, director, employee or owner of
more than 1% of the outstanding securities of any publicly traded direct or
indirect competitor of the Company; PROVIDED, HOWEVER, that the Company is given
written notice by the transferee stating the name and address of the transferee
and identifying the securities with respect to which such rights are being
assigned. Notwithstanding the foregoing restrictions with respect to
competitors, a professional institutional investor owning up to 20% of the
outstanding securities of a direct or indirect competitor of the Company may be
a transferee of such rights provided that it complies with the provisions of the
previous sentence. For purposes hereof the term "affiliate" shall mean, with
respect to the Company, any officer, director or holder of 5% or more of any
class of the Company's stock and, with respect to any Stockholder, any person
who or which controls, is controlled by or under common control with such
Stockholder.

         (b) TRANSFEREES. Any transferee to whom rights under this Agreement are
transferred shall, as a condition to such transfer, deliver to the Company a
written instrument by which such transferee agrees to be bound by the
obligations imposed upon the Stockholders hereby to the same extent as if such
transferee were a Stockholder hereunder.

         (c) SUBSEQUENT TRANSFEREES. A transferee to whom rights are transferred
pursuant to this Section 14 may not again transfer such rights to any other
person or entity, other than as provided in (a) and (b) above.

         SECTION 15. TERMINATION OF REGISTRATION RIGHTS. Notwithstanding any
other provision of this Agreement, each Stockholder's rights under this
Agreement shall terminate and the Company shall not be required pursuant to this
Agreement to give notice of any proposed


                                       9



registration pursuant to Section 2 or Section 3 to any Stockholder if, based on
record holdings, such Stockholder could then sell pursuant to Rule 144 (or any
similar rule) under the Securities Act in a single 90-day period all Registrable
Shares registered in the name of such holder; PROVIDED, HOWEVER, that any Series
5 Stockholder that is a limited partnership or limited liability company shall
be entitled to include any of its Registrable Shares in a proposed registration
to the extent that such Series 5 Stockholder requires such registration for
distribution to its limited partner or member.

         SECTION 16. NOTICES. All notices, requests, consents, and other
communications under this Agreement shall be in writing and shall be delivered
by hand, telecopy or telegram, overnight courier or first class certified or
registered mail, return receipt requested, postage prepaid:

         If to the Company, to Dyax Corp., One Kendall Square, Building 600 -
5th Floor, Cambridge, MA 02139, Attn: President, or such other address or
addresses as may have been furnished in writing by the Company to the
Stockholders, with a copy to Nathaniel S. Gardiner, Esq., Palmer & Dodge LLP,
One Beacon Street, Boston, Massachusetts 02108;

         If to any Stockholder, to its address set forth on SCHEDULE I, SCHEDULE
II or SCHEDULE III (with a copy to additional parties so listed for any such
Stockholder), as the case may be, or such other address or addresses as may have
been furnished to the Company in writing by such Stockholder.

         Notices provided in accordance with this Section 16 shall be deemed
delivered on the date of personal delivery, telecopy or telegram, the next
business day after delivery by overnight courier, or 48 hours after the date of
mailing.

         SECTION 17. ENTIRE AGREEMENT. This Agreement embodies the entire
agreement and understanding between the parties hereto with respect to the
subject matter hereof and supersedes all prior agreements and understandings
relating to such subject matter, including without limitation the Prior
Agreement.

         SECTION 18. AMENDMENTS AND WAIVERS. This Agreement may be amended and
the observance of any term of this Agreement may be waived (either generally or
in a particular instance and either retroactively or prospectively), with the
written consent of the Company and the holders of a majority of the Registrable
Shares; provided, however, that no amendment may be made that would adversely
affect the distinct rights of the Series 5 Stockholders under Section 2 hereof
without the express consent of the Series 5 Stockholders holding at least 50.1%
of the Series 5 Stock. Any amendment or waiver effected in accordance with this
Section 18 shall be binding upon each holder of Registrable Shares and the
Company. No waivers of or exceptions to any term, condition or provision of this
Agreement, in any one or more instances, shall be deemed to be, or construed as,
a further or continuing waiver of any such term, condition or provision.

         SECTION 19. COUNTERPARTS. This Agreement may be executed in several
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the


                                       10



same instrument. Execution of an undertaking agreeing to be bound by the terms
of this Agreement shall be deemed to be a counterpart signature to this
Agreement.

         SECTION 20. HEADINGS. The headings of the sections, subsections and
paragraphs of this Agreement have been added for convenience only and shall not
be deemed to be a part of this Agreement.

         SECTION 21. SEVERABILITY. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision.

         SECTION 22. GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the laws of the State of Delaware.


                  [Remainder of Page Intentionally left blank]

                           [Signature Pages to follow]



                                       11



         IN WITNESS WHEREOF, the undersigned have hereunto set their hand as of
the day and year first above written.

                           COMPANY:

                           DYAX CORP.


                           By: /s/ Henry E. Blair
                               --------------------------------------------
                               Name:  Henry E. Blair
                               Title: President


                           STOCKHOLDERS:


                           ALTA BIOPHARMA PARTNERS, L.P.
                           By Alta BioPharma Management, LLC


                           By: /s/ Alix Marduel
                               --------------------------------------------
                               Name: Alix Marduel
                               Title: Managing Director


                           ALTA Embarcadero BIOPHARMA, LLC


                           By: /s/ Elaine Walker
                               --------------------------------------------
                               Name: Elaine Walker
                               Title: Under Power of Attorney


                           DYAX CHASE PARTNERS (ALTA BIO), LLC
                           By Alta Chase BioPharma Management, LLC


                           By: /s/ Alix Marduel
                               --------------------------------------------
                               Name: Alix Marduel
                               Title: Member



                                       12



                           BANCBOSTON VENTURES


                           By: /s/ Marcia T. Bates
                               --------------------------------------------
                               Name:  Marcia T. Bates
                               Title: Managing Director


                           GATEWAY VENTURE PARTNERS III, L.P.
                           By: Gateway Associates III, L.P., as
                           General Partner


                           By: /s/ Constantine E. Anagnostopoulos
                               --------------------------------------------
                               Name: Constantine E. Anagnostopoulos
                               Title: General Partner


                           GATEWAY VENTURE PARTNERS II, L.P.
                           By: Gateway Associates II, L.P., as
                           General Partner


                           By: /s/ Constantine E. Anagnostopoulos
                               --------------------------------------------
                               Name: Constantine E. Anagnostopoulos
                               Title: General Partner


                           GENZYME CORPORATION


                           By: /s/ Peter Wirth
                               --------------------------------------------
                               Name: Peter Wirth
                               Title: Executive Vice President


                           GMM I SBIC, INC.
                           By: GMM Investors Corp.,
                               as General Partner


                           By: /s/ James J. Goodman
                               -------------------------------------------
                               Name: James J. Goodman
                               Title: President



                                       13




                           H&Q HEALTHCARE INVESTORS


                           By: /s/ Kerri A. Bisner
                               --------------------------------------------
                               Name:  Kerri A. Bisner
                               Title: Secretary


                           H&Q LIFE SCIENCES INVESTORS


                           By: /s/ Kerri A. Bisner
                               --------------------------------------------
                               Name:  Kerri A. Bisner
                               Title: Secretary


                           HEALTHCARE VENTURES V, L.P.


                           By: /s/ Jeffrey Steinberg
                               --------------------------------------------
                               Name:  Jeffrey Steinberg
                               Title: Administrative Partner of Health Care
                                      Partners V, L.P.,
                                      The General Partner of HealthCare
                                      Ventures V, L.P.

                           NEW YORK LIFE INSURANCE CO.


                           By: /s/ Dennis Purcell
                               --------------------------------------------
                               Name: Dennis Purcell
                               Title:


                           PRINCE VENTURE PARTNERS IV
                           By Prince Ventures Limited Partnership,
                                    As General Partner


                           By: /s/ James W. Fordyce
                               --------------------------------------------
                               Name: James W. Fordyce
                               Title: General Partner



                                       14



                           LOEB INVESTORS CO. 106
                           By Pinpoint Partners Corporation,
                                    As General Partner


                           By: /s/ Thomas L. Kemper
                               --------------------------------------------
                               Thomas L. Kempner
                               President


                           LOEB INVESTORS CO. 106A
                           By Pinpoint Partners Corporation,
                                    As General Partner


                           By: /s/ Thomas L. Kemper
                               --------------------------------------------
                               Thomas L. Kempner
                               President


                           LOEB INVESTORS CO. 106B
                           By Pinpoint Partners Corporation,
                                    As General Partner


                           By: /s/ Thomas L. Kemper
                               --------------------------------------------
                               Thomas L. Kempner
                               President


                           LOEB INVESTORS CO. 106C
                           By Pinpoint Partners Corporation,
                                    As General Partner


                           By: /s/ Thomas L. Kemper
                               --------------------------------------------
                               Thomas L. Kempner
                               President



                                       15




                           OAK INVESTMENT PARTNERS IV,
                           LIMITED PARTNERSHIP
                           By Oak Associates IV, Limited Partnership, as
                           General Partner


                           By: /s/ Edward F. Glassmeyer
                               --------------------------------------------
                               Name: Edward F. Glassmeyer
                               Title: General Partner
                                      Managing Member of Oak Associates IV,
                                      LLC, The General Partner of Oak
                                      Investment Partners, IV, Limited
                                      Partnership

                           OAK IV AFFILIATES FUND, LIMITED
                           PARTNERSHIP
                           By Oak IV Affiliates, as General Partner


                           By: /s/ Edward F. Glassmeyer
                               --------------------------------------------
                               Name: Edward F. Glassmeyer
                               Title: General Partner
                                      General Partner of Oak IV Affiliates,
                                      the General Partner of Oak IV Affiliates
                                      Fund, Limited Partnership


                           /s/ Henry E. Blair
                           ------------------------------------------------
                           Henry E. Blair


                           L. EDWARD CANNON, CUSTODIAN
                           FOR ANDREW CRAWFORD LADNER,
                           UMUTMA



                           ------------------------------------------------
                           L. Edward Cannon


                           L. EDWARD CANNON, CUSTODIAN
                           FOR SARAH JOHANNA LADNER,
                           UMUTMA



                           ------------------------------------------------
                           L. Edward Cannon



                                       16




                           ------------------------------------------------
                           Robert A. Dishman


                           /s/ Henry R. Lewis
                           ------------------------------------------------
                           Henry R. Lewis



                                       17



                                     SCHEDULE I




                                                                     POST-IPO                        TOTAL
SHAREHOLDER                          PRE-IPO HOLDINGS                COMMON SHARES
- -------------------------------------------------------------------------------------------------------------
                                                                                           
AltaBioPharma Partners, L.P.           Preferred Class A Series 5                       855,393
- -------------------------------------------------------------------------------------------------------------
                                                                                                      855,393
- -------------------------------------------------------------------------------------------------------------
BancBoston Ventures, Inc.              Preferred Class A Series 4                       374,045
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        42,568
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                       220,751
- -------------------------------------------------------------------------------------------------------------
                                                                                                      637,364
- -------------------------------------------------------------------------------------------------------------
R. Robert Woodburn, Jr. and Anne
Bacon Blair, Trustees of the Henry
E. Blair Irrevocable Trust                           Common Stock                       114,100
- -------------------------------------------------------------------------------------------------------------
                                                                                                      114,100
- -------------------------------------------------------------------------------------------------------------
Henry E. Blair                                       Common Stock                         9,253
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                         1,678
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        14,229
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        13,040
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        21,181
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                       232,597
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                       152,980
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                         7,438
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        76,656
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                         7,915
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        18,350
- -------------------------------------------------------------------------------------------------------------
                                                                                                      555,317
- -------------------------------------------------------------------------------------------------------------
Charter Growth Capital, L.P.           Preferred Class A Series 5                       183,310
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                       183,310
- -------------------------------------------------------------------------------------------------------------
                                                                                                      366,620
- -------------------------------------------------------------------------------------------------------------
Robert A. Davoli and/or Eileen L.
McDonagh, JTWROS                                     Common Stock                       162,372
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 2                        15,411
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                       168,497
- -------------------------------------------------------------------------------------------------------------
                                                                                                      346,280
- -------------------------------------------------------------------------------------------------------------
Robert A. Dishman, PhD.                              Common Stock                        61,124
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                         2,931
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                        37,490
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                        78,240
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         3,260
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        10,000
- -------------------------------------------------------------------------------------------------------------
                                                                                                      193,045
- -------------------------------------------------------------------------------------------------------------
Dyax Chase Partners (Alta Bio), LLC    Preferred Class A Series 5                       488,512
- -------------------------------------------------------------------------------------------------------------
                                                                                                      488,512
- -------------------------------------------------------------------------------------------------------------
Genzyme Corporation                    Preferred Class A Series 5                       550,458
- -------------------------------------------------------------------------------------------------------------
                                                                                                      550,458
- -------------------------------------------------------------------------------------------------------------
GMM I SBIC, INC.                       Preferred Class A Series 4                       431,103
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        27,172
- -------------------------------------------------------------------------------------------------------------
                                                                                                      458,275
- -------------------------------------------------------------------------------------------------------------
H&Q Health Care Investors                            Common Stock                         9,206
- -------------------------------------------------------------------------------------------------------------



                                                                     POST-IPO                        TOTAL
SHAREHOLDER                          PRE-IPO HOLDINGS                COMMON SHARES
- -------------------------------------------------------------------------------------------------------------
                                                                                              
                                       Preferred Class A Series 1                        25,478
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        26,812
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                        35,860
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                       102,862
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        99,083
- -------------------------------------------------------------------------------------------------------------
                                                                                                      299,301
- -------------------------------------------------------------------------------------------------------------
H&Q Life Sciences Investors            Preferred Class A Series 1                        41,095
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        26,812
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                        29,340
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        84,160
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        66,055
- -------------------------------------------------------------------------------------------------------------
                                                                                                      247,462
- -------------------------------------------------------------------------------------------------------------
HealthCare Ventures V, L.P.            Preferred Class A Series 5                     1,651,376
- -------------------------------------------------------------------------------------------------------------
                                                                                                    1,651,376
- -------------------------------------------------------------------------------------------------------------
Sidney Knafel                          Preferred Class A Series 4                        93,511
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        41,661
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        30,000
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        88,117
- -------------------------------------------------------------------------------------------------------------
                                                                                                      253,289
- -------------------------------------------------------------------------------------------------------------
New York Life Insurance Company        Preferred Class A Series 3                       244,500
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                       374,045
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        62,492
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 5                        45,871
- -------------------------------------------------------------------------------------------------------------
                                                                                                      726,908
- -------------------------------------------------------------------------------------------------------------
Prince Venture Partners IV Limited Partnership       Common Stock                         4,410
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                         2,205
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                         2,205
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                         2,205
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                         2,205
- -------------------------------------------------------------------------------------------------------------
                                                     Common Stock                            75
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        13,561
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,780
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,780
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,780
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,780
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                        12,506
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,253
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,253
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,253
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 1                         6,253
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                       163,000
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 3                        81,500
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                       233,778
- -------------------------------------------------------------------------------------------------------------
                                       Preferred Class A Series 4                        78,240
- -------------------------------------------------------------------------------------------------------------
                                                                                                      648,022
- -------------------------------------------------------------------------------------------------------------
TOTAL REGISTRABLE SHARES                                                              8,391,722     8,391,722