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                                                            Exhibit 10.4



                     MILLENNIUM PHARMACEUTICALS, INC.

                      REGISTRATION RIGHTS AGREEMENT

     This REGISTRATION RIGHTS AGREEMENT (this "AGREEMENT") is entered
into as of June 22, 2000 by and among Millennium Pharmaceuticals, Inc., a
Delaware corporation (the "COMPANY"), and Aventis Pharmaceuticals Inc., a
Delaware corporation ("PURCHASER").

                                 RECITALS

     WHEREAS, the Company and the Purchaser have entered into an
Investment Agreement, dated as of June 22, 2000 (the "INVESTMENT
AGREEMENT"), pursuant to which the Purchaser has agreed to purchase
shares (the "SHARES") of common stock, par value $.001 per share, of the
Company, upon the terms and conditions set forth therein;

     WHEREAS, in order to induce the Purchaser to enter into the
Investment Agreement, the Company has agreed to provide the registration
rights set forth in this Agreement for the benefit of Purchaser and its
direct and indirect transferees upon the terms and conditions set forth
herein; and

     WHEREAS, the execution and delivery of this Agreement is a condition
to the Purchaser's obligations pursuant to the Investment Agreement.

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

     1. DEFINITIONS. Capitalized terms used herein without definition
shall have the meanings assigned to such terms in the Investment
Agreement. For the purposes of this Agreement:

     "COMMISSION" means the U.S. Securities and Exchange Commission or
any other governmental authority from time to time administering the
Securities Act.

     "COMMON STOCK" means the common stock, par value $.001 per share, of
the Company.

     "DTC" means the Depository Trust Company.

     "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended, or any successor federal statute and the rules and the
regulations of the Commission promulgated thereunder, all as the same
shall be in effect from time to time.

     "HOLDER" means any Person owning or having the right to acquire
Registrable Securities, including an Affiliate or any successor, assignee
or transferee of Purchaser or a Holder that has received Registrable
Securities in accordance with Section 13 hereof.

     "NASD" means the National Association of Securities Dealers, Inc.


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     "PERSON" means any natural person, firm, partnership, association,
corporation, company, joint venture, unincorporated association, trust,
business trust, government or department or agency of a government,
limited liability company or other entity.

     "PROSPECTUS" means the prospectus included in any Registration
Statement (including without limitation, a prospectus that discloses
information previously omitted from a prospectus filed as part of an
effective registration statement in reliance upon Rule 430A), as amended
or supplemented by any prospectus supplement, with respect to the terms
of the offering or any portion of the Registrable Securities covered by
such Registration Statement and all other amendments and supplements to
the prospectus, including post-effective amendments, and all material
incorporated by reference or deemed to be incorporated by reference in
such prospectus.

     "REGISTRABLE SECURITIES" means (a) the Shares of Common Stock
received by the Purchaser pursuant to the Investment Agreement and (b)
any capital stock or other securities of the Company issued or issuable
with respect to the Shares, (i) upon any conversion or exchange thereof,
(ii) by way of stock dividend or other distribution, stock split or
reverse stock split, or (iii) in connection with a combination of shares,
recapitalization, merger, consolidation, exchange offer or other
reorganization. As to any particular Registrable Securities, once issued
such securities shall cease to be Registrable Securities when (A) a
Registration Statement with respect to the sale of such securities shall
have become effective under the Securities Act and such securities shall
have been disposed of in accordance with such Registration Statement, (B)
such securities shall have been distributed to the public in reliance
upon Rule 144 (or any successor provision) under the Securities Act,
provided that at the time such securities are proposed to be disposed of,
they may be sold under Rule 144 without any limitation on the amount of
such securities which may be sold or (C) they shall have ceased to be
outstanding.

     "REGISTRATION EXPENSES" means all fees and expenses incident to the
performance of or compliance with the provisions of this Agreement,
whether or not any Registration Statement is filed or becomes effective,
including, without limitation, all (a) registration and filing fees
(including, without limitation, (i) fees with respect to filings required
to be made and other expenses associated with the NASD and any other
applicable exchange in connection with an underwritten offering, and (ii)
fees and expenses of compliance with state securities or blue sky laws
(including, without limitation, fees and distributions of counsel for the
underwriter or underwriters in connection with blue sky qualifications of
the Registrable Securities and determination of eligibility of the
Registrable Securities for investment under the laws of such
jurisdictions as are provided in Section 5(e)), (b) printing expenses
(including, without limitation, expenses of printing certificates for
Registrable Securities in a form eligible for deposit with DTC and of
printing prospectuses), (c) fees and disbursements of all independent
certified public accountants referred to in Section 5 (including, without
limitation, the reasonable expenses of any special audit and "cold
comfort" letters required by or incident to such performance), (d) the
fees and expenses of any "qualified independent underwriter" or other
independent appraiser participating in an offering pursuant to the NASD
Rules of Conduct and the corresponding rules of any other applicable
exchange, (e) liability insurance under the Securities Act or any other
securities laws, if the Company desires such insurance, (f) fees and
expenses of all attorneys, advisers, appraisers and other persons
retained by the Company or any Subsidiary of the Company, (g) internal
expenses of the Company and its Subsidiaries (including, without
limitation, all salaries and expenses of officers and employees of the

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Company and its Subsidiaries, other general overhead expenses of the
Company and its Subsidiaries, and other expenses for the performance of
legal or accounting duties), (h) the expense of any annual audit and the
preparation of historical and pro forma financial statements or other
data normally prepared by the Company in the ordinary course of business,
(i) the expenses relating to printing, word processing and distributing
all Registration Statements, underwriting agreements, securities sales
agreements, and any other documents necessary in order to comply with
this Agreement, (j) any fees and disbursements of any other underwriters
and broker-dealers customarily paid by issuers or sellers of securities,
and (k) the fees and disbursements of not more than one (1) counsel
(together with appropriate local counsel) chosen by the Holders of a
majority of the Registrable Securities to be included in such
Registration Statement; PROVIDED, HOWEVER, that in all cases in which the
Company is required to pay Registration Expenses hereunder, Registration
Expenses shall exclude any underwriting discounts, selling commissions or
any transfer taxes payable in respect of the sale of the Registrable
Securities by the Holders thereof.

     "REGISTRATION STATEMENT" means any registration statement of the
Company that covers any of the Registrable Securities pursuant to the
provisions of this Agreement, and all amendments and supplements to any
such registration statement, including post-effective amendments, in each
case including the Prospectus, all exhibits and all material incorporated
by reference or deemed to be incorporated by reference in such
registration statement.

     "RULE 144" means Rule 144 (or any successor provision) under the
Securities Act.

     "SECURITIES ACT" means the Securities Act of 1933, as amended, or
any successor federal statute, and the rules and regulations of the
Commission promulgated thereunder, all as the same shall be in effect
from time to time.

     "SPECIAL REGISTRATION" means the registration of share of equity
securities and/or options or other rights in respect thereof to be
offered solely to directors, members of management, employees,
consultants or sales agents, distributors or similar representatives of
the Company or its direct or indirect Subsidiaries, solely on Form S-8 or
any successor form, a registration on Form S-4 with respect to any
merger, consolidation or acquisition, or a registration on another form
not available for registering Registrable Securities for sale to the
public.

     "UNDERWRITTEN REGISTRATION" or "UNDERWRITTEN OFFERING" means a
registration in which securities of the Company (including Registrable
Securities) are sold to an underwriter for reoffering to the public.

     2. DEMAND REGISTRATION.

        (a) REQUEST FOR REGISTRATION. Subject to the provisions of
Sections 2(d) and 8, at any time or from time to time as of the date
hereof, Holders of Registrable Securities shall have the right to make a
written request that the Company effect a registration under the
Securities Act of all or part of its Registrable Securities of the
Holders making such request. A request for registration pursuant to this
Section 2 (a "DEMAND REGISTRATION") shall specify the approximate number
of Registrable Securities requested to be registered, the anticipated per

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share price range for such offering and the intended method or
disposition thereof by such Holders.

        (b) OBLIGATION TO EFFECT REGISTRATION. Within five (5) days after
receipt by the Company of any request for Demand Registration, the
Company shall promptly give written notice of such requested registration
to all Holders. Such Holders shall have the right, by giving written
notice to the Company within twenty (20) days after the Company provides
its notice, to elect to have included in such registration such of their
Registrable Securities as such Holders may request in such notice of
election. Thereupon, the Company shall, as expeditiously as possible, use
reasonable best efforts to effect the registration under the Securities
Act of all Registrable Securities that the Company has been requested to
so register.

        (c) REGISTRATION STATEMENT FORM. Registrations under this Section
2 shall be on such appropriate form of Registration Statement of the
Commission as shall be selected by the Company and available to it under
the Securities Act. The Company agrees to include in any such
Registration Statement all information which, in the opinion of counsel
to the Company, is required to be included therein under the Securities
Act.

        (d) LIMITATIONS ON REGISTRATION. The Company shall not be
required to effect more than two (2) Demand Registrations pursuant to
this Section 2. 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) during the period starting with the date sixty
(60) days prior to the Company's estimated date of filing of, and ending
on the date ninety (90) days immediately following the effective date of,
any registration statement (other than a Special Registration) pertaining
to the securities of the Company, provided that the Company is actively
employing in good faith all reasonable efforts to cause such registration
statement to become effective. Notwithstanding any other provision of
this Agreement, the Company shall not be required to effect the Demand
Registration of any Registrable Securities prior to the second
anniversary of the First Closing Date of the Investment Agreement.

        (e) INCLUSION OF OTHER SECURITIES. The Company shall not register
securities (other than Registrable Securities) for sale for the account
of any Person in any request for Demand Registration, unless permitted to
do so by the written consent of the Holders of at least a majority of the
Registrable Securities proposed to be sold in such Demand Registration.

        (f) EFFECTIVE REGISTRATION STATEMENT. A Demand Registration shall
not be deemed to have been effected unless a Registration Statement
covering all of the Registrable Securities requested to be included in
such registration by the Holders thereof and as reduced, if necessary, in
accordance with Section 2(g) hereto has been declared effective by the
Commission and remains continually effective for the period specified in
Section 5(b).

        (g) SUSPENSION. If the Board of Directors of the Company, in its
good faith judgment, determines that any registration under the
Securities Act of Registrable Securities should not be made or continued
because it would materially interfere with any material financing,
acquisition, corporation reorganization, merger, or other transaction
involving the Company or any of its subsidiaries (a "VALID BUSINESS
REASON"), (i) the Company may postpone filing a Registration Statement
relating to a Demand Registration until such Valid Business


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Reason no longer exists, but in no event for more than 60 days,
and (ii) in case a Registration Statement has been filed relating to a
Demand Registration, the Company may cause such Registration Statement to
be withdrawn and its effectiveness terminated or may postpone amending or
supplementing such Registration Statement until such Valid Business
Reason no longer exists, but in no event for more than 60 days (the
"POSTPONEMENT PERIOD"); PROVIDED, HOWEVER, that in no event shall the
Company be permitted to postpone or withdraw a Registration Statement
within 120 days after the expiration of any Postponement Period.

        (h) ALLOCATION. If any Demand Registration involves an
underwritten offering and the managing underwriter of such offering shall
advise the Company that, in its view, the number of securities requested
to be included in such registration exceeds the largest number (the
"SECTION 2(h) NUMBER") that can be sold in an orderly manner in such
offering within a price range acceptable to the Holders of Registrable
Securities requesting the registration, the Company shall include in such
registration:

        (i) first, all Registrable Securities requested to be included in
such Registration by the Holders of Registrable Securities requesting
such registration; PROVIDED, HOWEVER, that, if the number of such
Registrable Securities exceeds the Section 2(h) Number, the number of
such Registrable Securities (not to exceed the Section 2(h) Number) shall
be allocated on a pro rata basis among all Holders of Registrable
Securities requesting such registration based on the number of
Registrable Securities that each holder requesting registration then owns
and the number of Registrable Securities then owned by all such Holders
requesting such registration; and

        (ii) second, to the extent that consent has been granted in
accordance with Section 2(e) and the number of Registrable Securities to
be included by all Holders of Registrable Securities requesting such
registration is less than the Section 2(h) Number, securities that the
Company proposes to register.

     3. PIGGYBACK REGISTRATION.

        (a) INCLUSION IN PIGGYBACK REGISTRATION. If the Company at any
time proposes to register any of its securities under the Securities Act
(other than pursuant to Section 2 or a Special Registration), whether or
not for sale for its own account, (a "COMPANY REGISTRATION") it shall
each such time, prior to such filing, give prompt written notice to all
Holders of Registrable Securities of its intention to do so and, upon the
written request of any Holder of Registrable Securities given to the
Company within twenty (20) days after the Company has provided such
notice (which request shall state the intended method of disposition of
such Registrable Securities), the Company shall use reasonable best
efforts to cause all Registrable Securities that the Company has been
requested by the Holders thereof to register to be so registered under
the Securities Act to the extent necessary to permit their disposition in
accordance with the intended methods of distribution specified in the
request of such Holder or Holders; PROVIDED, that if at any time after
giving written notice of its intention to register any securities and
prior to the effective date of the Registration Statement filed in
connection with such registration, the Company shall determine for any
reason not to register such securities, the Company may, at its election,
give written notice of such determination to each Holder that was
previously notified of such registration, and, thereupon, shall not
register any Registrable Securities in connection with


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such registration (but shall nevertheless pay the Registration
Expenses in connection therewith), without prejudice, however, to the
rights of any Holders to request that a registration be effect under
Section 2 and PROVIDED FURTHER, that no registration effected under this
Section 3 shall relieve the Company from its obligations to effect
Registration upon request under Section 2 and PROVIDED FURTHER, that the
Holders of Registrable Securities shall have no right to participate in,
or receive notice of, a Company Registration prior to the second
anniversary of the First Closing Date of the Investment Agreement.

        (b) TERMS OF UNDERWRITING. In connection with any offering under
this Section 3 involving an underwritten offering, the Company shall not
be required to include any Registrable Securities in such offering unless
the Holder thereof accepts the terms, if any, of the underwriting as
agreed upon between the Company and the underwriters selected by it
provided that such terms must be reasonably satisfactory in substance and
form to the Holder and consistent with this Agreement, and then only in
such quantity as will not, in the opinion of the managing underwriter,
jeopardize the success of the offering by the Company.

        (c) ALLOCATION. If any Company Registration involves an
underwritten offering and the managing underwriter of such offering shall
advise the Company that, in its view, the number of securities requested
to be included in such registration exceeds the largest number (the
"SECTION 3(c) NUMBER") that can be sold in an orderly manner in such
offering within a price range acceptable to the Company, the Company
shall include in such registration:

           (i) first, all securities that the Company proposes to register
for its own account (the "COMPANY SECURITIES"); and

        (ii) second, to the extent that the number of Company Securities
is less than the Section 3(c) Number, the remaining securities to be
included in such registration shall be allocated on a pro rate basis
among (i) all Holders of Registrable Securities requesting that
Registrable Securities be included in such Registration, and (ii) all
other holders ("Other Holders") of the Company's securities who have been
granted "piggy-back" registration rights with respect to such securities
(the "Other Securities") and have requested that such Other Securities be
included in such registration, based on the number of Registrable
Securities and Other Securities that each such Holder and Other Holder
requesting such registration bears to the aggregate number of Registrable
Securities and Other Securities then owned by all such Holders and Other
Holders requesting such registration.

     4. ALLOCATION OF EXPENSES. The Company will pay all Registration
Expenses of all registrations under this Agreement.

     5. OBLIGATIONS OF THE COMPANY. If and whenever the Company is
required to use best efforts to effect the registration under the
Securities Act of any Registrable Securities pursuant to Section 2 and 3
of this Agreement, the Company shall:

        (a) file with the Commission, as soon as practicable, a
Registration Statement with respect to such Registrable Securities, make
all required filings with the NASD and any other applicable exchange, and
use best efforts to cause such Registration Statement to become effective
at the earliest possible date and remain effective;

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        (b) prepare and file with the Commission such amendments and
supplements to the Registration Statement and the Prospectus used in
connection therewith and such other documents as may be necessary to keep
the Registration Statement effective until the consummation of the
disposition by the Holders of all the Registrable Securities covered by
such Registration Statement and otherwise comply with the provisions of
the Securities Act with respect to the disposition of all securities
covered by such Registration Statement;

        (c) furnish to counsel (if any) selected by the Holders of a
majority of the Registrable Securities covered by such Registration
Statement and to counsel for the underwriters in any underwritten
offering copies of all documents proposed to be filed with the Commission
in connection with such registration a reasonable time prior to the
proposed filing thereof and give reasonable consideration in good faith
to any comments of such Holders, counsel and underwriters;

        (d) furnish to each seller of such securities, without charge,
such number of conformed copies of such Registration Statement and of
each such amendment and supplement thereto (in each case, including all
exhibits (including all exhibits incorporated by reference), financial
statements, schedules, and all documents incorporated therein, deemed to
be incorporated therein by reference or filed therewith, except that the
Company shall not be obligated to furnish any seller of securities with
more than two copies of such exhibits and documents), such numbers of
copies of the Prospectus included in such Registration Statement
(including each preliminary prospectus) in conformity with the
requirements of the Securities Act, and such other documents, as such
seller may reasonably request in order to facilitate the disposition of
the Registrable Securities owned by such seller;

        (e) use its reasonable best efforts to register or qualify and
cooperate with the Holders of Registrable Securities, the underwriters
and their respective counsels in connection with the registration or
qualification (or exemption from such registration or qualification) of
the securities covered by such Registration Statement under such other
securities or blue sky laws of such jurisdictions as each seller shall
request; PROVIDED, HOWEVER, that where Registrable Securities are offered
other than through an underwritten offering, the Company agrees to cause
its counsel to perform blue sky investigations and file registrations and
qualification required to be filed pursuant to this Section 5(e); keep
each such registration or qualification (or exemption therefrom)
effective during the period such Registration Statement is required to be
effective hereunder and do any and all other acts and things which may be
necessary or advisable to enable such seller to consummate the
disposition in such jurisdictions of the securities owned by such seller,
except that the Company shall not for any such purpose be required to
qualify generally to do business as a foreign corporation in any
jurisdiction wherein it is not so qualified, subject itself to taxation
in any jurisdiction wherein it is not so subject, or take any action
which would subject it to general service of process in any jurisdiction
wherein it is not so subject;

        (f) in connection with an underwritten public offering only,
furnish to each seller in a signed counterpart, addressed to the sellers,
of

              (i) an opinion of counsel for the Company experienced in
     securities law matters, dated the effective date of the Registration
     Statement, and



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              (ii) a "cold comfort" letter signed by the independent public
     accountants who have issued an audit report on the Company's
     financial statements included in the Registration Statement, subject
     to such seller having executed and delivered to the independent
     public accountants such certificates and documents as such
     accountants shall reasonably request,

covering substantially the same matters with respect to the
Registration Statement (and the Prospectus included therein) and, in the
case of such accountants' letter, with respect to events subsequent to
the date of such financial statements, as are customarily covered in
opinions of issuer's counsel and in accountants' letters delivered to the
underwriters in underwritten public offerings of securities;

        (g) (i) notify each Holder of Registrable Securities subject to
such Registration Statement if such Registration Statement, at the time
it or any amendment thereto became effective, (x) contained an untrue
statement of a material fact or omitted to state a material fact required
to be stated therein or necessary to make the statements therein not
misleading upon discovery by the Company of such material misstatement or
omission or (y) upon discovery by the Company of the happening of any
event as a result of which the Company believes there would be such a
material misstatement or omission, and, as promptly as practicable,
prepare and file with the Commission a post-effective amendment to such
Registration Statement and use reasonable best efforts to cause such
post-effective amendment to become effective such that such Registration
Statement, as so amended, shall not contain an untrue statement or a
material fact or omit to state a material fact required to be stated
therein or necessary to make the statements therein not misleading, and
(ii) notify each Holder of Registrable Securities subject to such
Registration Statement, at any time when a Prospectus related therefor is
required to be delivered under the Securities Act, if the Prospectus
included in such Registration Statement, as then in effect includes an
untrue statement of a material fact or omits to state a material fact
required to be stated therein or necessary to make the statements
therein, in light of the circumstances under which they were made, not
misleading upon discovery by the Company of such material misstatement or
omission or upon the discovery by the Company of the happening of any
event as a result of which the Company believes that there would be a
material misstatement or omission, and, as promptly as is practicable,
prepare and furnish to such Holder a reasonable number of copies of a
supplement to or an amendment of such Prospectus as may be necessary so
that, as thereafter delivered to the purchasers of such securities, such
Prospectus shall not include an untrue statement of a material fact or
omit to state a material fact required to be stated therein or necessary
to make the statements therein, in light of the circumstances under which
they were made, not misleading;

        (h) otherwise use its reasonable best efforts to comply with all
applicable rules and regulations of the Commission, and make available to
its security holders, as soon as reasonably practicable, an earnings
statement of the Company complying with the provisions of Section 11(a)
of the Securities Act and Rule 158 under the Securities Act (or any
similar rule promulgated under the Securities Act) no later than 45 days
after the end of any 12-month period (or 90 days after the end of any
12-month period if such period is a fiscal year) (i) commencing at the
end of any fiscal quarter in which Registrable Securities are sold to an
underwriter or to underwriters in a firm commitment or best efforts
underwritten offering, and (ii) if not sold to an underwriter or to
underwriters in such an offering, commencing on the first day of the
first fiscal


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quarter of the Company after the effective date of the relevant
Registration Statement, which statements shall cover said 12-month
periods;

        (i) promptly notify each Holder of Registrable Securities covered
by such Registration Statement, their counsel and the underwriters (i)
when such Registration Statement, or any post-effective amendment to such
Registration Statement, shall have become effective, or any amendment of
or supplement to the Prospectus used in connection therewith shall be
filed, (ii) of any request by the Commission to amend such Registration
Statement or to amend or supplement such Prospectus or for additional
information, (iii) of the issuance by the Commission of any stop order
suspending the effectiveness of such Registration Statement or of any
order preventing or suspending the use of any preliminary prospectus or
the initiation or threatening of any proceedings for any of such
purposes, (iv) of the suspension of the qualification of such securities
for offering or sale in any jurisdiction, or of the institution of any
proceedings for any of such purposes and (v) if at any time when a
Prospectus is to be required by the Securities Act to be delivered in
connection with the sale of the Registrable Securities, the
representations and warranties of the Company contained in any agreement
(including the underwriting agreement contemplated in Section 6(b)
below), to the knowledge of the Company, cease to be true and correct in
any material respect;

        (j) use its reasonable best efforts to prevent the issuance of
any order suspending the effectiveness of the Registration Statement or
of any order preventing or suspending the use of a Prospectus or
suspending the qualification (or exemption from qualification) of any of
the Registrable Securities covered thereby for sale in any jurisdiction,
and, if any such order is issued, to obtain the withdrawal of any such
order at the earliest possible moment;

        (k) if requested by the managing underwriter, if any, (i)
promptly incorporate in a prospectus supplement or post-effective
amendment such information as the managing underwriter, if any,
reasonably requests to be included therein to comply with applicable law,
and (ii) make all required filings of such prospectus supplement or such
post-effective amendment as soon as practicable after the Company has
received notification of the matters to be incorporated in such
prospectus supplement or post-effective amendment;

        (l) cooperate with the Holders and the managing underwriter, if
any, to facilitate the timely preparation and delivery of certificates
representing Registrable Securities to be sold, which certificates shall
not bear any restrictive legends whatsoever and shall be in a form
eligible for deposit with DTC, and enable such Registrable Securities to
be in such denominations and registered in such names as the
underwriters, if any, or Holders may reasonably request at least two (2)
business days prior to any sale of Registrable Securities in a firm
commitment underwritten public offering;

        (m) use its reasonable best efforts to cause the Registrable
Securities covered by a Registration Statement to be registered with, and
to obtain the consent or approval of, each governmental agency or
authority, whether federal, state, local or foreign, which may be
required to effect such registration or the offering or sale in
connection therewith or to enable the sellers to offer, or to consummate
the disposition of, the Registrable Securities subject to such
Registration Statement, except as may be required solely as a consequence
of the nature of such


                                   -9-
<PAGE>

seller's business, in which case the Company will cooperate with
all reasonable respects with the filing of the Registration Statement and
the granting of such approvals;

        (n) prior to the effective date of the Registration Statement,
(i) provide the registrar for the Common Stock or such other Registrable
Securities with printed certificates for such securities in a form
eligible for deposit with DTC and (ii) provide a CUSIP number for such
securities; and

        (o) agree not to file or make any amendment to any Registration
Statement with respect to any Registrable Securities, or any amendment of
or supplement to the Prospectus used in connection therewith, which
refers to any seller of any securities covered thereby by name, or
otherwise identifies such seller as the holder of any securities of the
Company, without the consent of such seller, such consent not to be
unreasonably withheld, except that no such consent shall be required for
any disclosure that is required by law.

     6. UNDERWRITTEN OFFERINGS. The provisions of this Section 6 do
not establish additional registration rights but instead set forth
procedures applicable, in addition to those set forth in Sections 2, 3
and 5, to any registration that is an underwritten offering.

        (a) UNDERWRITTEN OFFERINGS EXCLUSIVE. Whenever a request for
Demand Registration is for an underwritten offering, only securities that
are to be distributed by the underwriters may be included in the
Registration.

        (b) UNDERWRITING AGREEMENT. If requested by the underwriters for
any underwritten offering by Holders pursuant to a request for Demand
Registration, the Company shall enter into an underwriting agreement with
such underwriters for such offering, such agreement to be reasonably
satisfactory in substance and form to the Holders of a majority of the
Registrable Securities to be covered by such registration and to the
underwriters and to contain such representations and warranties by the
Company and such other terms and provisions as are customarily contained
in agreements of this type, including, but not limited to, indemnities to
the effect and to the extent provided in Section 10, provisions for the
delivery of officers' certificates, opinions of counsel and accountants'
"cold comfort" letters, and hold-back arrangements. The Holders of
Registrable Securities to be distributed by such underwriters shall be
parties to such underwriting agreement and may, at their option, require
that any or all the representations and warranties by, and the agreements
on the part of, the Company to and for the benefit of such underwriters
be made to and for the benefit of such Holders and that any or all of the
conditions precedent to the obligations of such underwriters under such
underwriting agreements shall also be conditions precedent to the
obligations of such Holders. No such Holders shall be required by the
Company to make any representations or warranties to, or agreements with,
the Company or the underwriters other than as set forth in Section 6(d)
and representations, warranties or agreements regarding such Holder and
such Holders's intended method of distribution.

        (c) SELECTION OF UNDERWRITERS. Whenever a request for Demand
Registration is for an underwritten offering, the Holders of a majority
of the Registrable Securities to be Registered pursuant to such offering
shall have the right to select one or more underwriters to administer the
offering, subject to the consent of the Company, which shall not be
unreasonably


                                  -10-
<PAGE>

withheld. If the Company at any time proposes to register any of
its securities under the Securities Act for sale for its own account and
such securities are to be distributed by or through one or more
underwriters, the Company shall have the right to select one or more
underwriters to administer the offering, subject to the consent of the
Holders of a majority of the Registrable Securities to be registered
pursuant to such offering, which shall not be unreasonably withheld. In
all cases in this Section 6(c), at least one of the underwriters chosen
by the Holders or the Company shall be an underwriter of
nationally-recognized standing.

        (d) HOLD BACK AGREEMENTS. If and whenever the Company proposes to
register any of its equity securities under the Securities Act, whether
or not for its own account (other than pursuant to a Special
Registration), or is required to use its best efforts to effect the
registration of any Registrable Securities under the Securities Act
Pursuant to Section 2 or 3, each Holder, if required by the managing
underwriter in an underwritten offering, agrees by acquisition of such
Registrable Securities not to effect (other than pursuant to such
registration) any public sale or distribution, including, without
limitation, any sale pursuant to Rule 144, of any Registrable Securities,
any other equity securities of the Company or any securities convertible
into or exchangeable or exercisable for any equity securities of the
Company during the ten (10) days prior to, and for ninety (90) days
after, the effective date of such registration, to the extent timely
notified in writing by the Company or the managing underwriter, and the
Company agrees to cause each director and executive officer of the
Company to enter into a similar agreement with the Company. The foregoing
provisions shall not apply to any Holder if such Holder is prevented by
applicable statute or regulation from entering into any such agreement;
PROVIDED, HOWEVER, that any such Holder shall undertake, in its request
to participate in any such underwritten offering, not to effect any
public sale or distribution of any applicable class of Registrable
Securities commencing on the date of sale of such applicable class of
Registrable Securities unless it has provided forty-five (45) days prior
written notice of such sale or distribution to the underwriter or
underwriters. The Company further agrees not to effect (other than
pursuant to such registration or pursuant to a Special Registration) any
public sale or distribution, or to file any Registration Statement (other
than such registration or Special Registration) covering any, of its
equity securities, or any securities convertible into or exchangeable or
exercisable for such securities, during the ten (10) days prior to, and
for ninety (90) days after, the effective date of such registration if
required by the managing underwriter.

        7. PREPARATION, REASONABLE INVESTIGATION. In connection with the
preparation and filing of each Registration Statement registering
Registrable Securities under the Securities Act, the Company shall give
the Holders of Registrable Securities to be so registered and their
underwriters, if any, and their respective counsel and accountants, the
opportunity to participate in the preparation of such Registration
Statement, each Prospectus included therein or filed with the Commission,
and each amendment thereof or supplement thereto, and shall give each of
them such access to all pertinent financial, corporate, and other
documents and properties of the Company and its Subsidiaries, and such
opportunities to discuss the business of the Company with its officers,
directors, employees and the independent public accountants who have
issued audit reports on its financial statements as shall be necessary,
in the opinion of such Holders' and such underwriters' respective
counsel, to conduct a reasonable investigation within the meaning of the
Securities Act.

                                  -11-
<PAGE>

        8. OTHER REGISTRATION. If and whenever the Company is required to
use its best efforts to effect the registration under the Securities Act
of any Registrable Securities pursuant to Section 2 or 3, and if such
registration shall not have been withdrawn or abandoned, the Company
shall not be obligated to and shall not file any Registration Statement
with respect to any of its securities (including Registrable Securities)
under the Securities Act (other than a Special Registration), whether of
its own accord or at the request or demand of any holder or holders of
such securities, until a period of 180 days shall have elapsed from the
effective date of such previous registration, PROVIDED that the Company
shall not be excused from filing a Registration Statement by virtue of
this Section 8 more than once in a 360 day period.

     9. CERTAIN OBLIGATIONS OF HOLDERS.

        (a) The Company may require each Holder of any Registrable
Securities as to which any registration is being effected to furnish to
the Company such information regarding such Holder and the intended
method of disposition of such securities as the Company may from time to
time reasonably request in writing and as shall be required to effect the
registration of such Holder's Registrable Securities. Each such Holder
agrees to furnish promptly to the Company all information required to be
disclosed in order to make the information previously furnished to the
Company by such Holder not materially misleading.

        (b) Each Holder of Registrable Securities covered by a
Registration Statement agrees that, upon receipt of any notice from the
Company pursuant to Section 5(g), such Holder shall promptly discontinue
the disposition of Registrable Securities pursuant to such Registration
Statement until such Holder shall have received, in the case of clause
(i) of Section 5(g), notice from the Company that such Registration
Statement has been amended, as contemplated by Section 5(g), and, in the
case of clause (ii) of Section 5(g), copies of the supplemented or
amended Prospectus contemplated by Section 5(g). If so directed by the
Company, each Holder will deliver to the Company (at the Company's
expense) all copies, other than permanent file copies, in such Holder's
possession of the Prospectus covering such Registrable Securities at the
time of receipt of such notice. In the event that the Company shall give
any such notice, the period mentioned in Section 5(b) shall be extended
by the number of days during the period from and including the date of
the giving of such notice to and including the date when each seller of
any Registrable Securities covered by such Registration Statement shall
have received copies of the supplemented or amended Prospectus covering
such Registrable Securities contemplated by Section 5(g).

     10. INDEMNIFICATION AND CONTRIBUTION.

        (a) In the event of any registration of any of the Registrable
Securities under the Securities Act pursuant to this Agreement, the
Company will indemnify and hold harmless the seller of such securities,
its directors, officers, and employees, each other Person who
participates as an underwriter, broker or dealer in the offering or sale
of such securities, and each other person, if any, who controls such
seller, underwriter, broker, dealer or any such participating Person
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 or any such director, officer, employee, underwriter, broker,
dealer, participating Person, or controlling Person may become subject
under the Securities Act, the Exchange Act, state securities or blue sky
laws, or


                                  -12-
<PAGE>

otherwise, insofar as such losses, claims, damages, or liabilities (or
actions or proceedings 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 Securities were registered under the Securities Act, any
preliminary prospectus, or Prospectus contained in the 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 shall reimburse
such seller and each such director, officer, employee, underwriter,
broker, dealer, participating Person, and controlling Person in
connection with investigating or defending any such loss, claim, damage,
liability, action or proceeding as such expenses are incurred; PROVIDED,
HOWEVER, that the Company will not be liable in any such case to the
extent that any such loss, claim, damage, liability or expense 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, participating Person or controlling Person
specifically for use in the preparation thereof.

        (b) In the event of any registration of any of the Registrable
Securities under the Securities Act pursuant to this Agreement, each
seller of such securities, 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,
underwriters, or controlling Persons may become subject under the
Securities Act, Exchange Act, state securities or blue sky laws, or
otherwise, insofar as such losses, claims, damages, or liabilities (or
actions or proceedings 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 securities were
registered under the Securities Act, any preliminary prospectus or
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 relating to such seller furnished in writing
to the Company by or on behalf of such seller expressly for use in
connection with the preparation of such Registration Statement,
preliminary prospectus, Prospectus, amendment, or supplement; PROVIDED,
HOWEVER, that the liability of each such seller hereunder shall be in
proportion to and limited to the net amount received by such seller
(after deducting any underwriting discount and expenses) from the sale of
Registrable Securities sold in connection with such registration.

        (c) Each party entitled to indemnification under this Section 10
(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


                                  -13-
<PAGE>

relieve the Indemnifying Party of its obligations under this
Section 10, except to the extent that the Indemnifying Party is adversely
affected by such failure. 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 or conflicts 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 that 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 litigations, 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, which
consent shall not be unreasonably withheld.

        (d) If for any reason the foregoing indemnity is unavailable, or
is insufficient to hold harmless an Indemnified Party, other than by
reason of the exceptions provided in this Section 10, then the
Indemnifying Party shall, in lieu of indemnifying such Indemnified Party,
contribute to the amount paid or payable by the Indemnifying Party as a
result of such losses, claims, damages liabilities or expenses in such
proportion as is appropriate to reflect the relative fault of the
Indemnifying Party on the one hand and the Indemnified Party on the other
in connection with the statements or omissions which resulted in such
losses, claims, damages, or liabilities, as well as any other relevant
equitable considerations. The relative fault 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 or the
Holders of Registrable Securities covered by the Registration Statement
in question and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or
omission.

        (e) The Company and the Holders agree that it would not be just
and equitable if contribution pursuant to this Section 10 were determined
by pro rata allocation or by any other method of allocation which does
not take account of the equitable considerations referred to in Section
10(d). The amount paid or payable by an Indemnified Party as a result of
the losses, claims, damages and liabilities referred to in Section 10(d)
shall be deemed to include, subject to the limitations set forth above,
any legal or other expenses reasonably incurred by such Indemnified Party
in connection with investigating or defending any such claim or
litigation. Notwithstanding anything to the contrary in this Section 10,
(A) no such Holder will be required to contribute any amount in excess of
the proceeds it received from the sale of its Registrable Securities
pursuant to such Registration Statement, (B) no Person guilty of
fraudulent misrepresentation, within the meaning of Section 11(f) of the
Securities Act, shall be entitled to contribution from any Person who was
not guilty of such fraudulent misrepresentation and (C) no party shall be
liable for contribution under this Section 10 except to the extent and
under such circumstances as such party would have been liable to
indemnify under this Section 10 if such indemnification were enforceable
under applicable law. Any party entitled to contribution will, promptly
after receipt of notice of commencement of any action, suit or proceeding
against such party in respect to which a claim for contribution may be
made against another party or parties under this Section, notify such
party or parties from whom contribution may be sought, but the omission
so to notify such party or parties from whom contribution may be sought
shall not


                                  -14-
<PAGE>

relieve such party from any other obligation it or they may have
thereunder or otherwise under this Section. No party shall be liable for
contribution with respect to any action, suit, proceeding or claim
settled without its prior written consent, which consent shall not be
unreasonably withheld.

     11. INDEMNIFICATION WITH RESPECT TO UNDERWRITTEN OFFERING. In the
event that Registrable Securities are sold pursuant to a Registration
Statement in an underwritten offering, 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.

     12. REPORTS UNDER SECURITIES EXCHANGE ACT OF 1934. With a view to
making available to the Holders 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 Holder to sell Registrable
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) 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; and

        (c) furnish to any Holder, so long as such Holder owns any
Registrable Securities, forthwith upon request (i) a written statement by the
Company that it has complied with the reporting requirements of Rule 144
under the Securities Act, any other such applicable reporting requirements
under the Securities Act and all applicable reporting requirements under the
Exchange Act, (ii) a copy of the most recent annual or quarterly report of
the Company. and such other reports and documents so filed by the Company,
and (iii) such other information as may be reasonably requested in availing
any Holder of any rule or regulation of the Commission which permits the
selling of any such securities without Registration or pursuant to such form.

        13. SUCCESSORS, ASSIGNS AND TRANSFEREES. This Agreement shall be
binding upon and shall inure to the benefit of each party hereto, and
their respective successors, assigns and transferees. The Purchaser or
any other Holder under this Agreement may assign its rights under this
Agreement to any Affiliate of the Purchaser or any such Holder; PROVIDED,
HOWEVER, that the Company is given written notice from the Purchaser or
any such Holder at the time of such transfer or assignment or within a
reasonable time after said transfer or assignment stating the name and
address of the transferee or assign and identifying the securities with
respect to which the rights hereunder are being transferred. As a
condition to the effectiveness of any transfer permitted hereunder the
transferee or assign shall agree, in writing, upon request of the
Company, to be bound by the provisions of this Agreement. Provided that
the Purchaser or any Holder and any transferee or assignee has complied
with the foregoing conditions, this Agreement shall survive any transfer
of Registrable Securities to and shall inure to the benefit of an
Affiliate of the Purchaser or any such Holder. In addition, and whether
or not any express


                                  -15-
<PAGE>

transfer or assignment shall have been made, the provisions of
this Agreement which are for the benefits of the parties hereto other
than the Company shall also be for the benefit of and enforceable by any
subsequent Holder or Registrable Securities.

     14. MISCELLANEOUS.

        (a) NO INCONSISTENT AGREEMENTS. The Company will not hereafter
enter into any agreement with respect to its securities which is
inconsistent with or violates the rights granted to the Holders in this
Agreement.

        (b) ADJUSTMENTS AFFECTING REGISTRABLE SECURITIES. The Company
will not take any action, or permit any change to occur, with respect to
its securities that would adversely affect the ability of the Holders to
include such Registrable Securities in a registration undertaken pursuant
to this Agreement or which would adversely affect the marketability of
such Registrable Securities in any such registration (including, without
limitation, effecting a stock split or a combination of shares).

        (c) SPECIFIC PERFORMANCE; OTHER RIGHTS. The parties recognize
that various of the rights of the Purchaser and any other Holder under
this Agreement are unique and agree that irreparable damage would occur
in the event that any of the provisions of this Agreement were not
performed in accordance with their specific terms or were otherwise
breached. Accordingly, the parties agree that each of the Purchaser and
any such Holder shall, in addition to such other remedies as may be
available to it at law or in equity, have the right to enforce its rights
hereunder by actions for injunctive relief and specific performance in
any court of the United States or any state thereof having jurisdiction,
to the extent permitted by law. The Company hereby waives any requirement
for security or the posting of any bond in connection with any temporary
or permanent award of injunctive, mandatory or other equitable relief.

        (d) SEVERABILITY. If any term, provision, covenant or restriction
of this Agreement is held by a court of competent jurisdiction to be
invalid, void or unenforceable, the remainder of the terms, provisions,
covenants and restrictions of this Agreement shall remain in full force
and effect and shall in no way be affected, impaired or invalidated. It
is hereby stipulated and declared to be the intention of the parties that
they would have executed the remaining terms, provisions, covenants, and
restrictions without including any of such which may be hereafter
declared invalid, void or unenforceable.

        (e) NOTICES. All notices and other communications required or
permitted under this Agreement shall be effective upon receipt and shall
be in writing and may be delivered in person, by telecopy, overnight
delivery service or registered or certified United States mail, addressed
to the Company or the Purchaser (or to any other Holder not a party
hereto on the date hereof, to the address of such Holder in the stock
record books of the Company), as the case may be, at their respective
addresses set forth below:

           (i)  If to the Company to:

                Millennium Pharmaceuticals, Inc.
                75 Sidney Street
                Cambridge, Massachusetts 02139-4815

                                  -16-
<PAGE>

                Attn: General Counsel
                Telephone: (617) 679-7000
                Facsimile: (617) 621-0264

                and to:

                Hale and Dorr LLP
                60 State Street
                Boston, Massachusetts 01209
                Attn: Steven Singer
                Telephone: (617) 526-6000
                Facsimile: (617) 526-5000

           (ii) If to Purchaser to:

                Aventis Pharmaceuticals Inc.
                Route 202-206
                P.O. Box 6800
                Bridgewater, NJ 08867

                Attn: Vice President, Legal Corporate Development
                Telephone: (908) 231-3537
                Facsimile: (908) 231-4480

                With copies to:

                Morgan, Lewis & Bockius LLP
                502 Carnegie Center
                Princeton, NJ 08540
                Attn: Randall B. Sunberg

                      Telephone: (609) 919-6600
                      Facsimile: (609) 919-6639

All notices and other communications shall be effective upon the
earlier of actual receipt thereof by the person to whom notice is
directed or (a) in the case of notices and communications sent by
personal delivery or telecopy, one business day after such notice or
communication arrives at the applicable address or was successfully sent
to the applicable telecopy number, (b) in the case of notices and
communications sent by overnight delivery service, at noon (local time)
on the second business day following the day such notice or
communications was delivered to such delivery service, and (c) in the
case of notices and communications sent by United States mail, seven days
after such notice or communication shall have been deposited in the
United States mail. Any notice delivered to a party hereunder shall be
sent simultaneously, by the same means, to such party's counsel as set
forth above.

        (f) ENTIRE AGREEMENT. This Agreement contain the entire
understanding of the parties with respect to the matters covered hereby.



                                  -17-
<PAGE>

        (g) AMENDMENTS AND WAIVERS. This Agreement may be amended as to
the Holders and their successors and assigns (determined as provided in
Section 13), and the Company may take any action herein prohibited, or
omit to perform any act required to be performed by it, only if the
Company shall obtain the written consent of the Holders of 75% of the
Registrable Securities. This Agreement may not be waived, changed,
modified, or discharged orally, but only by an agreement in writing
signed by the party or parties against whom enforcement of any waiver,
change, modification or discharge is sought or by parties with the right
to consent to such waiver, change, modification or discharge on behalf of
such party; PROVIDED, HOWEVER, that any consent required by the Holders
shall require the consent in writing of no less than the Holders of 75%
of the Registrable Securities.

        (h) HEADINGS; COUNTERPARTS. Headings in this Agreement are for
purposes of reference only and shall not limit or otherwise affect the
meaning hereof. This Agreement may be executed in any number of
counterparts, each of which shall be an original, but all of which
together shall constitute one and the same instrument, and shall become
effective when one or more of the counterparts have been signed by each
party and delivered to the other parties, it being understood that all
parties need not sign the same counterpart.

        (i) GENDER. Whenever used herein the singular number shall
include the plural, the plural shall include the singular, and the use of
any gender shall include all genders.

        (j) FURTHER ASSURANCES. Each of the parties hereto agrees to
execute and deliver those writings and documents reasonably required to
more fully carry out the purposes of this Agreement and the transactions
contemplated hereby.

        (k) GOVERNING LAW. THIS AGREEMENT SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE OF DELAWARE WITHOUT
REGARD TO CONFLICTS OF LAW PRINCIPLES.

        (l) NO THIRD PARTY BENEFICIARIES. Except as provided by Sections
10 and 13, nothing contained in this Agreement is intended to confer upon
any Person other than the parties hereto and their respective successors
and permitted assigns and transferees, any benefit, right or remedies
under or by reason of this Agreement.

        (m) CONSENT TO JURISDICTION. Each of the parties hereto
irrevocably submits to the personal exclusive jurisdiction of the United
States District Court for the District of Delaware for the purposes of
any suit, action or other proceeding arising out of this Agreement or any
transaction contemplated hereby (and, to the extent permitted under
applicable rules of procedure, agrees not to commence any action, suit or
proceeding relating hereto except in such court). Each of the parties
hereto further agrees that service of any process, summons, notice or
document hand delivered or sent by registered mail to such party's
respective address set forth in Section 14(e) will be effective service
of process for any action, suit or proceeding in Delaware with respect to
any matters to which it has submitted to jurisdiction as set forth in the
immediately preceding sentence. Each of the parties hereto irrevocably
and unconditionally waives any objection to the laying of venue of any
action, suit or proceeding arising out of this Agreement or the
transactions contemplated hereby in the United States District court for
the District of Delaware, and hereby further irrevocably and
unconditionally waives and agrees not


                                  -18-
<PAGE>

to plead or claim in such court that any such action, suit or
proceeding brought in such court has been brought in an inconvenient
forum.



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                                  -19-
<PAGE>


        IN WITNESS WHEREOF, each of the parties has executed this
Agreement or caused this Agreement to be executed on its behalf as of the
day and year first above written.

MILLENNIUM PHARMACEUTICALS, INC.               AVENTIS PHARMACEUTICALS INC.

By: /s/ STEVEN H. HOLTZMAN                     By: /s/ FRANK DOUGLAS, M.D.
Title: Chief Business Officer                  Title: Executive Vice President