Document:

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                                                                   EXHIBIT 10.23

                                  BIOGEN, INC.
                    1987 SCIENTIFIC BOARD STOCK OPTION PLAN
      (As amended and restated through December 14, 2001, effective as of
                               December 31, 2001)

I.   PURPOSE OF THE PLAN

     The Plan is intended to encourage ownership of shares of the Common Stock
by members of the Scientific Board of the Company and to provide an additional
incentive to those Scientific Board members to promote the success of the
Company and its Affiliates.

II.  DEFINITIONS

     1.   "Affiliate" means (a) a corporation in respect of which the Company
owns directly or indirectly fifty percent (50%) or more of the voting shares
thereof or which is otherwise controlled by the Company; or (b) to the extent
not inconsistent with Section 424 of the Code, an unincorporated trade or
business controlled by the Company which has elected, for federal income tax
purposes, to be either (i) classified as an association taxable as a corporation
or (ii) disregarded as an entity separate from its owner (as provided in Section
301.7701-3 of the federal income tax regulations). For purposes of this
definition, the Company shall be deemed to control another entity if the Company
possesses, directly or indirectly, the power to direct or cause the direction of
the management and policies of such entity, whether through ownership of voting
securities, by contract or otherwise.

     2.   "Code" means the Internal Revenue Code of 1986, as amended from time
to time.

     3.   "Committee" means the Stock and Option Plan Administration Committee
of the Board of Directors of the Company or, if such committee ceases to exist,
the Board of Directors of the Company or a committee thereof to which
responsibility for administering the Plan shall have been delegated.

     4.   "Common Stock" means the common stock of the Company, par value $0.01
per share.

     5.   "Company" means Biogen, Inc., a Massachusetts corporation.

     6.   "Exchange Act" means the United States Securities Exchange Act of
1934, as amended from time to time.

     7.   "Fair Market Value" shall have the meaning set forth in Section VI.A.

     8.   "Member" means a member of the Scientific Board of the Company.

     9.   "Option" means a stock option granted under the Plan.

     10.  "Option Certificate" means a certificate delivered to an Option holder
by the

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Company pursuant to the Plan, in such form as the Committee shall approve, which
sets forth the terms and conditions of an Option.

     11.  "Plan" means this 1987 Scientific Board Stock Option Plan, as amended
and restated from time to time.

     12.  "Securities Act" means the United States Securities Act of 1933, as
amended from time to time.

III  SHARES SUBJECT TO THE PLAN

     The aggregate number of shares as to which Options may be granted from time
to time shall be 3,000,000 shares of the Common Stock.

     If any Option ceases to be "outstanding", in whole or in part, other than
by reason of the exercise of such Option, the shares which were subject to such
Option shall be available for the granting of other Options. Any Option shall be
treated as "outstanding" until such Option is exercised in full, terminates
under the provisions of the Plan or expires by reason of lapse of time.

     The aggregate number of shares as to which Options may be granted shall be
subject to change only by means of an amendment adopted in accordance with
Article XI, subject to the provisions of Article VIII.

IV.  ADMINISTRATION OF THE PLAN

     The Plan shall be administered by the Committee. The membership of the
Committee shall be determined, and shall be subject to change without cause and
without notice from time to time, by the Board of Directors of the Company.

     The Committee is authorized to interpret the provisions of the Plan or of
any Option and to make all rules and determinations necessary or advisable for
the administration of the Plan. The interpretation and construction by the
Committee of any provision of the Plan or of any Option granted under it shall
be final. The Committee's determinations under the Plan do not need to be
uniform and may be made by it selectively among persons who receive, or are
eligible to receive, Options under the Plan (whether or not such persons are
similarly situated). Subject to the provisions of the Plan, Options may be
granted upon such terms and conditions as the Committee may prescribe.

V.   ELIGIBILITY FOR PARTICIPATION

     The Committee shall determine which Members shall be eligible to
participate in the Plan. Without limited the generality of the foregoing,
Options may be awarded for reasons of performance, merit, bonus or upon new
Members joining the Scientific Board of the Company.

     The Committee may grant to one or more such Members one or more Options,
and shall

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designate the number of shares to be optioned under each Option so granted;
provided, however, that no Options shall be granted after December 31, 2002.

VI.  TERMS AND CONDITIONS OF OPTIONS

     No Option issued pursuant to the Plan shall be an incentive stock option
under Section 422 of the Code. No purported grant of any Option shall be
effective until such Option shall have been approved by the Committee. The
Committee may provide that Options be granted subject to such conditions as the
Committee may deem appropriate, including without limitation, subsequent
approval by the shareholders of the Company of the Plan or any amendments
thereto. Each Option shall be subject to at least the following terms and
conditions:

     A.   OPTION PRICE: Each Option Certificate shall state the Option price per
share of the Common Stock covered by such Option grant. Except as otherwise
determined by the Committee, the Option price per share for Options granted
under the Plan shall be equal to the fair market value per share of Common Stock
(the "Fair Market Value") on the date of grant of the Option; provided, however,
that in no event shall the Option price be less than the par value per share of
the Common Stock. Fair Market Value shall be calculated as follows: (i) if the
Common Stock is listed on a national securities exchange or traded on the Nasdaq
National Market or the Nasdaq SmallCap Market AND sale prices are regularly
reported for the Common Stock, then the Fair Market Value shall be the
arithmetic mean between the "high" and "low" sale prices for the Common Stock
reported on the applicable composite tape or other comparable reporting system
on the date of grant, or if the date of grant is not a trading day, on the most
recent trading day immediately prior to the date of grant; or (ii) if sale
prices are not regularly reported for the Common Stock as described in clause
(i) above but bid and asked prices for the Common Stock are regularly reported,
then the Fair Market Value shall be the arithmetic mean between the closing or
last bid and asked prices for the Common Stock on the date of grant or, if the
date of grant is not a trading day, on the most recent trading day immediately
prior to the date of grant; or (iii) if sale prices are not regularly reported
for the Common Stock as described in clause (i) or (ii) above, then the Fair
Market Value shall be such value as the Committee in good faith determines.

     B.   NUMBER OF SHARES: Each Option Certificate shall state the number of
shares of the Common Stock to which it pertains.

     C.   TERM OF OPTION: Each Option Certificate shall state the term of the
Option which shall be ten (10) years from the date of the grant thereof or at
such earlier or later time as the Committee shall expressly state in the Option
Certificate.

     D.   DATE OF EXERCISE: Each Option Certificate shall state the date or
dates on which the Option becomes exercisable, and may provide that the Option
rights accrue or become exercisable in installments over a period of months or
years, or upon the attainment of stated goals or events or through other
circumstances or programs approved by the Committee. The Committee shall have
the right to accelerate the date of exercise of any installment of any Option.

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     E.   CANCELLATION AND REPURCHASE RIGHTS: An Option Certificate may
stipulate that an Option which becomes exercisable shall be subject to
cancellation or that shares purchased upon the exercise of such Option shall be
subject to repurchase rights in favor of the Company. In such event the
Committee shall determine the date or dates, or event or events, upon which such
cancellation or repurchase rights shall become effective or shall lapse, as the
case may be and those provisions shall be set forth in the Option Certificate.

     F.   MEDIUM OF PAYMENT: The option price shall be payable upon the exercise
of the Option. It shall be payable (a) in United States dollars in cash or by
check, (b) if permitted by the Committee, in shares of the Common Stock held by
the Option holder for at least six months having a fair market value (determined
in the manner provided in Section VI.A as of the date of exercise) equal to the
cash exercise price of the Option, (c) at the discretion of the Committee, by
delivery of the Option holder's personal note, for full, partial or no recourse,
bearing interest payable not less than annually at market rate on the date of
exercise and no less than 100% of the applicable Federal rate, as defined in
Section 1274(d) of the Code, with or without the pledge of shares of the Common
Stock as collateral, (d) at the discretion of the Committee, in accordance with
a cashless exercise program established with a securities brokerage firm, or (e)
at the discretion of the Committee, by any combination of (a), (b), (c) and (d)
above.

     G.   EXERCISE OF OPTION AND ISSUE OF SHARES: Options shall be exercised by
giving written notice to the Company or its designee, together with provision
for payment of the Option price in accordance with Section VI.F. Such written
notice shall be signed by the person exercising the Option, shall state the
number of shares of the Common Stock with respect to which the Option is being
exercised, and shall contain any warranty required by Article VII of the Plan.
The issuance of the shares of the Common Stock upon exercise of the Option may
be delayed by the Company if any law or regulation may be delayed by the Company
if any law or regulation requires the Company to take any action with respect to
the shares prior to the issuance thereof. Without limiting the generality of the
foregoing, nothing contained herein shall be deemed to require the Company to
issue any shares of the Common Stock if prohibited by law or applicable
regulation.

     The shares of the Common Stock shall, upon issuance, be paid-up,
non-assessable shares.

     H.   ASSIGNABILITY AND TRANSFERABILITY OF OPTION: By its terms, an Option
granted to an Option holder shall not be transferable by such Option holder
other than (i) by will or by the laws of descent and distribution, or (ii)
pursuant to a qualified domestic relations order, as defined by the Code or
Title 1 of the Employee Retirement Income Security Act or the rules thereunder,
or (iii) as otherwise determined by the Committee. The designation of a
beneficiary of an Option by an Option holder shall not be deemed a transfer
prohibited by this Section. Except as provided in the preceding sentence, an
Option shall be exercisable, during an Option holder's lifetime, only by the
Option holder (or his or her legal representative) and shall not be assigned,
pledged, or hypothecated in any way (whether by operation of law or otherwise)
and shall not be subject to execution, attachment or similar process. Any
attempted transfer, assignment, pledge, hypothecation, or other disposition of
any Option or of any rights granted thereunder contrary to the provisions of
this Section, or the levy of any attachment or similar process upon an Option or
other such rights, shall be null and void.

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     I.   OTHER PROVISIONS: The Option Certificates shall be subject to such
other terms and conditions, including, without limitation, restrictions upon the
exercise of the Option, as the Committee shall deem advisable.

     J.   TAX WITHHOLDING: In the event that any federal, state, or local income
taxes, employment taxes, Federal Insurance Contributions Act withholdings or
other amounts are required by applicable law or governmental regulation to be
withheld from the Option holder's salary in connection with the exercise of an
Option, the Option holder shall advance in cash to the Company, or to any
Affiliate of the Company which employs or employed the Option holder, the amount
of such withholdings unless a different withholding arrangement, including the
use of shares of the Common Stock, is authorized by the Committee (and permitted
by law); provided, however, that with respect to persons subject to Section 16
of the Exchange Act, any such withholding arrangement shall be in compliance
with any applicable provisions of Rule 16b-3 promulgated under Section 16 of the
Exchange Act. If the Committee allows withholding through use of shares of the
Common Stock, it shall be only to the statutory minimum amount. For purposes
hereof, the fair market value of the shares withheld for purposes of payroll
withholding shall be determined in the manner provided in Section VI.A as of the
date of exercise. If the fair market value of the shares withheld is less than
the amount of payroll withholdings required, the Option holder may be required
to advance the difference in cash to the Company or the Affiliate employer.

     K.   RIGHTS AS A SHAREHOLDER: No Option holder shall have rights as a
shareholder with respect to any shares of the Common Stock covered by such
Option except as to such shares as have been registered in the Company's share
register in the name of such person upon the due exercise of the Option.

VII. PURCHASE FOR INVESTMENT

     If and to the extent that the issuance of shares pursuant to the exercise
of Options is deemed by the Company to be subject to the Securities Act, or to
the securities law of any other jurisdiction, the Company shall be under no
obligation to issue shares covered by such exercise unless the person or persons
who exercises or who exercise such Option shall make such warranty or take such
action as may be required by any applicable securities law of any applicable
jurisdiction and shall, in the case of the applicability of the Securities Act,
in the absence of an effective registration under the Securities Act with
respect to such shares, warrant to the Company, at the time of such exercise,
that such person is or that they are acquiring the shares to be issued to such
person or to them, pursuant to such exercise of the Option, for investment and
not with a view to, or for sale in connection with, the distribution of any such
shares; and in such events the person or persons acquiring such shares shall be
bound by the provisions of a legend endorsed upon any share certificates
expressing the requirements of any applicable non-United States securities law,
or, in cases deemed governed by the Securities Act, substantially the following
legend, which shall be endorsed upon the certificate or certificates evidencing
the shares issued by the Company pursuant to such exercise:

          "The securities represented by this certificate have not been
          registered

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          under the securities laws of any country, including the United States
          Securities Act of 1933, as amended, and the Company may refuse to
          permit the sale or transfer of all or any of the shares until (1) the
          Company has received an opinion of counsel satisfactory to the Company
          that any such transfer is exempt from registration under all
          applicable securities laws or (2) in the case of sales or transfers to
          which the united Sates Securities Act of 1933, as amended, is
          applicable, unless a registration statement with respect to such
          shares shall be effective under such Act, as amended."

Without limiting the generality of the foregoing, the Company may delay issuance
of the shares until completion of any action or obtaining of any consent which
the Company deems necessary under any applicable law (including without
limitation state securities or "blue sky" laws).

VIII. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION

     In the event that outstanding shares of the Common Stock are changed into
or exchanged for a different number or kind of shares or other securities of the
Company or of another corporation by reason of any reorganization, merger,
consolidation, recapitalization, reclassification, change in par value, stock
split-up, combination of shares or dividend payable in capital stock, or the
like, appropriate adjustment shall be made in the number and kind of shares for
the purchase of which Options may be granted under the Plan, and, in addition,
appropriate adjustment shall be made in the number and kind of shares and in the
option price per share subject to outstanding Options so that each Option holder
shall be in a position equivalent to the position the Option holder would have
been in had the Option holder exercised the Option immediately prior to the
applicable event.

IX.  DISSOLUTION OR LIQUIDATION OF THE COMPANY

     Upon the dissolution or liquidation of the Company other than in connection
with a transaction to which the preceding Article VIII is applicable, all
Options granted hereunder shall terminate and become null and void; provided,
however, that if the rights hereunder of an Option holder or one who acquired an
Option by will or by the laws of descent and distribution have not otherwise
terminated and expired, the Option holder or such person shall have the right
immediately prior to such dissolution or liquidation to exercise any Option
granted hereunder to the extent that the right to purchase shares thereunder has
accrued as of the date of exercise immediately prior to such dissolution or
liquidation.

X.   TERMINATION OF THE PLAN

     Unless the Committee shall decide to reduce or, subject to shareholder
approval, if required under Article XI, to extend the duration of the Plan, the
Plan shall terminate on December 31, 2002. Termination of the Plan shall not
affect any Options granted or any Option Certificates or agreements executed
prior to the effective date of termination.

XI.  AMENDMENT OF THE PLAN

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     The Plan may be amended by the Committee or the Board of Directors of the
Company; provided, however, that if the scope of any amendment is such as to
require shareholder approval then such amendment shall require approval by the
shareholders. Any amendment shall not affect any Options theretofore granted and
any Option Certificates or agreements theretofore executed by the Company and
any Option holder unless such amendment shall expressly so provide. No amendment
shall adversely affect any Option holder with respect to an outstanding Option
without the written consent of such Option holder. With the consent of the
Option holder affected, the Committee may amend any outstanding Option
Certificate or agreement in a manner not inconsistent with the Plan, including,
without limitation, to accelerate the date of exercise of any installment of any
Option.

XII. EMPLOYMENT RELATIONSHIP

     Nothing herein contained shall be deemed to prevent the Company or an
Affiliate from terminating the employment or consultancy of any Member, nor to
present any Member from terminating his employment or consultancy with the
Company or an Affiliate.

XIII. EFFECTIVE DATE

     The Plan first became effective on March 6, 1987.

XIV. GOVERNING LAW

     The Plan shall be construed and enforced in accordance with the laws of The
Commonwealth of Massachusetts.

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                                                                   EXHIBIT 10.24

                                  BIOGEN, INC.

                  VOLUNTARY EXECUTIVE SUPPLEMENTAL SAVINGS PLAN
               (As amended and restated through December 14, 2001)

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                                TABLE OF CONTENTS

                                                                            Page

ARTICLE 1
         INTRODUCTION........................................................ 1
          1.1     Purpose and Effective Date................................. 1

ARTICLE 2
         DEFINITIONS......................................................... 1
          2.1     Base salary................................................ 1
          2.2     Biogen..................................................... 1
          2.3     Board...................................................... 1
          2.4     Bonus...................................................... 1
          2.5     Committee.................................................. 1
          2.6     Participant................................................ 1
          2.7     Plan....................................................... 1
          2.8     Savings Plan............................................... 1
          2.9     Plan Year.................................................. 1

ARTICLE 3
         PARTICIPATION....................................................... 1
          3.1     Eligibility and Participation.............................. 1
          3.2     End of Participation....................................... 2

ARTICLE 4
         SAVINGS DEPOSITS BY PARTICIPANTS; EMPLOYER CREDITS.................. 2
          4.1     Savings Deposits........................................... 2
          4.2     Employer Credits........................................... 3

ARTICLE 5
         PARTICIPANTS' ACCOUNTS.............................................. 3
          5.1     Participant Accounts....................................... 3
          5.2     Vesting.................................................... 4

ARTICLE 6
         DISTRIBUTIONS TO PARTICIPANT........................................ 4
          6.1     Distributions for Financial Hardship....................... 4
          6.1A    In-Service Distribution(s) at a Time Specified
                  by Participant............................................. 4
          6.2     Distribution Upon Participant's Retirement................. 5
          6.3     Distribution Upon Death of a Participant................... 5
          6.4     Distribution upon Participant's Other Termination
                  of Employment.............................................. 5
          6.5     Installment Distributions in Certain Cases................. 5

ARTICLE 7
         MISCELLANEOUS....................................................... 6
          7.1     Amendment or Termination of Plan........................... 6
          7.2     Benefits Not Currently Funded.............................. 6
          7.3     No Assignment.............................................. 7
          7.4     Responsibilities and Authority of Committee................ 7
          7.5     Limitation on Rights Created by Plan....................... 7
          7.6     Tax Withholding............................................ 7
          7.7     Text Controls.............................................. 7
          7.8     Applicable State Law....................................... 8

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                                    ARTICLE 1
                                  INTRODUCTION

1.1    PURPOSE AND EFFECTIVE DATE. The purpose of this plan is to provide
certain designated key executives of Biogen (or its subsidiaries) with
additional tax-deferred savings opportunities supplementing those available
under the Savings Plan. This plan allows participants whose compensation exceeds
the amount of compensation that may be taken into account by the Savings Plan
for any plan year (the Code Section 401(a)(17) limits) to make savings deposits
hereunder from such excess compensation with matching Biogen contributions on
the same basis as is provided in the Savings Plan, and allows participants to
make additional, unmatched savings deposits from base salary or bonus if elected
by a participant. The effective date of this plan is April 18, 1994.

                                   ARTICLE 2
                                  DEFINITIONS

       This section contains definitions of terms used in the plan. Where the
context so requires, the masculine includes the feminine, the singular includes
the plural, and the plural includes the singular.

2.1    BASE SALARY means the base salary established for any participant by his
employer as in effect from time to time; the entire amount of a participant's
base salary will be taken into account in accordance with the terms of this plan
without regard to any dollar limitation on applicable compensation that may be
imposed under the Savings Plan.

2.2    BIOGEN means Biogen, Inc., a Massachusetts corporation, or any successor
to all or the major portion of its assets or business which assumes the
obligations of Biogen, Inc. under this plan.

2.3    BOARD means the Board of Directors of Biogen.

2.4    BONUS means the amount of compensation paid to a participant in addition
to his base salary and designated as such participant's bonus by his employer;
the entire amount of any such bonus will be taken into account in accordance
with the terms of this plan without regard to any dollar limitation on
applicable compensation that may be imposed under the Savings Plan.

2.5    COMMITTEE means the Savings Plan Committee constituted under the Savings
Plan.

2.6    PARTICIPANT means an employee of Biogen (or a subsidiary or affiliate)
who is eligible to participate in this plan in accordance with Section 3.1
hereof and who has made a savings deposit hereunder.

2.7    PLAN means the Biogen, Inc. Voluntary Executive Supplemental Savings
Plan, as set forth in this plan instrument, and as it may be amended from time
to time.

2.8    SAVINGS PLAN means the Biogen Savings Plan, as amended from time to time.
Any term defined in the Savings Plan will have the same meaning when used in
this plan unless otherwise defined herein.

2.9    PLAN YEAR means the period commencing April 18, 1994 and ending December
31, 1994, and the 12-month periods commencing on January 1, 1995 and on each
subsequent January 1 while the plan remains in effect.

                                   ARTICLE 3
                                 PARTICIPATION

3.1    ELIGIBILITY AND PARTICIPATION. A person (a) who is an employee of Biogen
(or a subsidiary or affiliate) and (b) who is designated by the committee will
be eligible to be a participant in this plan. His eligibility will be effective
as of the date specified by the committee. An eligible employee will become a
participant hereunder when he makes a savings deposit to this plan.
Participation in this plan is voluntary and no eligible employee will be
required to participate. An individual will not be considered an employee for
purposes of this plan if the individual is classified as a consultant or
contractor under Biogen's (or a subsidiary's or affiliate's) regular personnel
classifications and practices, or he is a party to an agreement to provide
services to Biogen (or a subsidiary or affiliate) without participating in this
plan, notwithstanding that such individual may be treated as a common law
employee for payroll tax or other legal purposes.

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3.2    END OF PARTICIPATION. A participant's participation in this plan will end
upon the termination of his service as an employee of Biogen (or a subsidiary or
affiliate) because of death, retirement, or any other reason.

       In addition, a participant's participation will end upon the committee's
specifying that he is no longer eligible to participate. In such event, his
participation will end effective as of the later of the date of the committee's
action or the date specified by the committee; provided that no such action will
retroactively deprive a participant of any amount credited to his account or any
benefit he was entitled to under this plan calculated as of the effective date
of his termination of participation.

       Upon the termination of a participant's participation in this plan in
accordance with this section, the participant may make no further savings
deposits hereunder and there will be no additional employer matching credits to
such participant's account. However, the participant will be entitled to receive
any amounts in his accounts in accordance with this plan.

       Notwithstanding the preceding provisions of this section, if a
participant's service as an employee of Biogen (or a subsidiary or affiliate)
ends but he continues in the position of Chairman of the Board of Directors of
Biogen, his participation in this plan will continue and he will be eligible to
continue making savings deposits hereunder in accordance with the plan, and for
this purpose his regular remuneration as Chairman will be deemed to be his base
salary and any bonus he receives as Chairman will be deemed to be his bonus.
However, he will not be eligible to receive any matching employer credits under
Section 4.2 based upon such savings deposits. He will not be considered to have
retired or terminated employment for purposes of Section 6.2 or Section 6.4
until his termination of service as Chairman.

                                   ARTICLE 4
               SAVINGS DEPOSITS BY PARTICIPANTS; EMPLOYER CREDITS

4.1    SAVINGS DEPOSITS.

       (a)    SAVINGS DEPOSITS. Each eligible employee may make savings deposits
to the plan from his base salary in any whole percentage of his base salary from
a minimum of 1% to a maximum of 100% by agreeing to reduce his base salary by
such amount. In addition, each eligible employee may make savings deposits to
the plan from his bonus in any whole percentage of his bonus from a minimum of
1% to a maximum of 100% by agreeing to reduce his bonus by such amount.

       All amounts by which a participant reduces his base salary or his bonus
hereunder are referred to herein as the participant's SAVINGS DEPOSITS. The
amount by which a participant's savings deposits for a plan year hereunder do
not exceed 6% of his applicable compensation (as defined in the Savings Plan)
are referred to herein as his MATCHABLE SAVINGS DEPOSITS; provided, however,
that a participant's matchable savings deposits for any plan year hereunder will
not exceed the limit on elective deferrals for such year under Code Section
402(g)(1) and (4) reduced by his basic savings deposits for such year under the
Savings Plan.

       (b)    SIGN-UP PROCEDURE FOR SAVINGS DEPOSITS. An eligible employee who
wishes to reduce his base salary and/or bonus with respect to a particular plan
year in order to make savings deposits must complete an enrollment form
specifying the amount of his savings deposits (with separate percentages for his
base salary and bonus if desired), agreeing to reduce his base salary and/or
bonus by the amount(s) desired, and providing such other information as the
committee may require.

       A participant's initial enrollment form will also specify the time for
payment (or the commencement of installment payments) under Section 6.2 or
Section 6.4 and the form of payment (lump sum or installments in accordance with
Section 6.5(a) below) of his accounts hereunder. The time specified for payment
may be anytime the participant indicates, but not later than the later of the
participant's termination of employment or the participant's 55th birthday. In
addition, a participant's initial enrollment form may (but is not required to)
specify one or more in-service distributions to the participant in accordance
with Section 6.1A if desired by the participant.

       A participant's enrollment form electing savings deposits for any plan
year must be filed with the committee at least two weeks before the start of
such plan year. A participant may change the amount of his savings deposits (but
not the time for payment or the form of payment of his accounts except as
provided in subsections (c) and (d) below) with respect to any subsequent plan
year by filing a new enrollment form at least two weeks before the start of such
subsequent plan year, and the change will become effective as of the first day
of such subsequent

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plan year. Once a participant has elected to defer base salary and/or bonus, his
enrollment form will remain in effect for future plan years unless the
participant changes or terminates his prior elections by filing a new enrollment
form in accordance with the preceding sentence.

         After a plan year has begun, a participant may not change the amount of
savings deposits (if any) he had elected for such plan year. However, if a
participant has an unforeseeable financial hardship (as defined in Section 6.1)
during a year, the participant may cancel his savings deposits election for the
balance of that year.

       (c)    SPECIAL ONE-TIME ELECTION. Notwithstanding any other provisions of
this plan, each participant who has an account hereunder as of December 1, 2001
may make a special one-time election to change the time for payment (or the
commencement of installment payments) of his account balance to an earlier date
specified by him or to elect one or more in-service distributions in accordance
with Section 6.1A if desired. Such special election must be made before June 30,
2002.

         If any participant makes the election provided for in the preceding
paragraph, the amount specified by the participant for accelerated payment or
in-service distribution under Section6.1A shall be reduced by ten percent.

       (d)    Notwithstanding subsection (b) above, at anytime prior to the date
for payment originally elected by the participant, if the participant is still
an employee of Biogen (or a subsidiary or affiliate) at such time, the
participant may elect to defer the time when his account(s) would otherwise be
payable (or installment payments would otherwise begin) to a subsequent date
specified by him (not later than the latest time permitted under subsection (b))
or may elect installments (or a greater number of installments). If such
election becomes effective as provided below, then the participant's account(s)
will be payable at the time specified in his subsequent election. The
participant's election under this subsection (d) will become effective if any of
the following criteria is satisfied: (i) the participant remains an employee of
Biogen (or a subsidiary or affiliate) for at least one year after making such
election, (ii) the participant's service as an employee of Biogen (or a
subsidiary or affiliate) ends due to disability (which means the participant's
inability to perform the material duties of his position because of a physical
or mental illness or condition), or (iii) the participant's employment as an
employee of Biogen (or a subsidiary or affiliate) is involuntarily terminated
without cause.

       A participant may make only one election under this subsection (d) to
further defer payment.

4.2      EMPLOYER CREDITS.

       (a)    AMOUNT OF MATCHING EMPLOYER CREDITS. For each calendar quarter (or
a shorter period of time specified by the committee) during a plan year, each
employer will credit a matching contribution amount to the account of each
participant employed by such employer who makes matchable savings deposits
during such calendar quarter (or such shorter period of time). The employer's
matching contribution credits will be equal to 25% of the participant's
matchable savings deposits during the calendar quarter (or such shorter period
of time).

       (b)    TIME FOR MAKING EMPLOYER MATCHING CREDITS. The employer's matching
amounts under subsection (a) will be credited to participants' accounts as soon
as practicable after each calendar quarter (or such shorter period of time
specified by the committee).

                                   ARTICLE 5
                             PARTICIPANTS' ACCOUNTS

5.1    PARTICIPANT ACCOUNTS.

       (a)    SAVINGS DEPOSITS ACCOUNTS. Savings deposits by a participant from
his base salary or bonus hereunder will be credited to an account in the name of
such participant. Such account will be called his savings deposits account.

       (b)    EMPLOYER MATCHING CREDITS ACCOUNTS. Employer credits on a
participant's behalf under Section 2(a) will be credited to an account in the
name of such participant. Such account will be called his employer matching
credits account.

       (c)    PARTICIPANT'S ACCOUNT VALUE. A participant's accounts will be
credited with deemed investment results as if participant savings deposits and
employer matching credits on a participant's behalf were invested in one

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<PAGE>

or more designated investment funds and all dividends and distributions on
shares of a particular investment fund were reinvested in shares of such fund.
The investment funds available for this purpose will be those from time to time
available as investment options for participants' accounts under the Savings
Plan (other than the Biogen stock fund).

       Each participant will indicate with his initial enrollment form the
investment fund or funds (and the proportion in each fund when the participant
designates more than one) he wishes to designate for this purpose. Thereafter, a
participant may change his designation either with respect to the deemed
investment of future savings deposits and matching credits or the deemed
transfer of amounts from a previously designated investment fund to another
fund. The committee shall establish the frequency by which such a change may be
made, the method of making such a change, and the effective date of such a
change and shall prescribe such other rules and procedures as it deems
appropriate. Such designation will remain in effect until subsequently changed
by the participant in accordance with this paragraph.

       Deemed investment results under this subsection will be credited to a
participant's accounts effective as of the last day in each calendar quarter (or
such shorter time specified by the committee).

       The value of a participant's accounts at any point in time will be his
savings deposits and employer matching credits on his behalf, increased or
decreased by deemed investment results as provided in this subsection (c)
through the most recent calendar quarter (or such shorter time specified by the
committee), and reduced by any distributions from the participant's accounts.

       (d)    BOOKKEEPING ACCOUNTS. Participants' accounts and subaccounts
(including savings deposits accounts and employer matching credits accounts)
will be maintained on the books of the participant's employer for bookkeeping
purposes only; such accounts will not represent any interest in any trust or in
any segregated asset.

       In order to facilitate the administration of the plan, the committee may
arrange for a participant's savings deposits account and/or employer matching
credits account to be divided for record keeping purposes into two or more
subaccounts, in accordance with procedures established by the committee.

5.2    VESTING.

       (a)    SAVINGS DEPOSITS ACCOUNT. A participant will have a fully vested
              interest in his savings deposits account at all times.

       (b)    EMPLOYER MATCHING CREDITS ACCOUNT. A participant will have a fully
vested interest in his employer matching credits account at all times.

                                   ARTICLE 6
                          DISTRIBUTIONS TO PARTICIPANT

6.1    DISTRIBUTIONS FOR FINANCIAL HARDSHIP. If a participant has a serious
financial hardship, he may apply to the committee for a distribution from the
plan prior to his retirement, other termination of service with his employer or
other designated time for payment. If such application for a hardship
distribution is approved by the committee, the distribution will be made as soon
as practicable after the later of the date specified in the participant's
application or the date of approval by the committee. The amount of the
distribution will be the amount needed to alleviate the participant's financial
hardship, as determined by the committee, up to a maximum of the participant's
account balances. Such a distribution will be made from the participant's
accounts in a single lump-sum payment. If such a participant's account has two
or more subaccounts, the committee will determine which subaccounts will be
debited to reflect the financial hardship distribution.

       Financial hardship will be limited to the following: bankruptcy or
impending bankruptcy, unexpected and unreimbursed major expenses resulting from
illness to person or accident to person or property, and to other types of
unforeseeable and unreimbursed expenses of a major nature that normally would
not be budgetable. Financial hardship shall not include foreseeable expenses
such as down payments on a home or purchase of an auto or college or other
educational expenses.

6.1A   IN-SERVICE DISTRIBUTION(S) AT A TIME SPECIFIED BY PARTICIPANT. If, in his
initial enrollment form (or, if applicable, his one-time election under Section
4.1(c) or (d)), a participant designated payment of his account(s) (or

                                       4
<PAGE>

a specified portion thereof) at a specified time(s) and he is still an employee
of Biogen (or a subsidiary or affiliate) at such time(s), the participant will
receive payment of the amount to be distributed in accordance with such
election, payable on or as soon as practicable after the designated date(s). A
participant's election for in-service distributions under this Section 6.1A may
be for a single payment or up to five annual payments, in each case in an amount
or portion specified by the participant in his enrollment or other election
form. Each payment will be the amount specified (or the entire balance remaining
in the participant's accounts, if less).

         Any amount in a participant's accounts hereunder not distributed to the
participant under this Section 6.1A will be distributed under Section 6.2, 6.3
or 6.4, whichever may be applicable, and Section 6.5, if applicable. If a
participant is receiving multiple payments under this Section 6.1A and retires,
dies or otherwise terminates employment, payments under this subsection will
cease and subsequent payments will be governed by Section 6.2, 6.3 or 6.4, as
the case may be.

6.2    DISTRIBUTION UPON PARTICIPANT'S RETIREMENT. Following the later of a
participant's retirement from his employer or the date specified by the
participant in his payment election (but not later than his 55th birthday), the
participant will receive a single sum payment equal to his account balance,
payable on a date determined by the committee, but not later than one year after
the specified date (or after the committee's receipt of satisfactory evidence of
the occurrence of his retirement).

6.3    DISTRIBUTION UPON DEATH OF A PARTICIPANT.

       (a)    IN GENERAL. If a participant dies while still an employee of
Biogen (or a subsidiary or affiliate) or after termination of such employment,
but before the complete distribution of his accounts hereunder, his beneficiary
will receive the total amount remaining in his accounts. Distribution will be
made in a single sum payment on a date determined by the committee, but not
later than one year after the committee receives such evidence of the
participant's death and of the right of any beneficiary to receive payment as it
deems necessary.

       (b)    BENEFICIARY. The beneficiary to receive the payment described in
subsection (a) above will be the same person or persons who are to receive
benefits payable upon the participant's death under the Savings Plan. If more
than one person is a beneficiary, death benefits hereunder will be paid to them
in the same proportions as under the Savings Plan. In the event that a
participant does not participate in the Savings Plan, the participant may
designate one or more beneficiaries to receive a distribution payable under
subsection (a) above and may revoke or change such a designation at any time. If
the participant names two or more beneficiaries, distribution to them will be in
such proportions as the participant designates or, if the participant does not
so designate, in equal shares. Any designation of beneficiary will be in writing
on such form as the committee may prescribe or deem acceptable, and will be
effective upon filing with the committee.

6.4    DISTRIBUTION UPON PARTICIPANT'S OTHER TERMINATION OF EMPLOYMENT.
Following the later of a participant's termination of employment for any reason
other than retirement or death or the date specified by the participant in his
payment election (but not later than his 55th birthday), the participant will
receive a single sum payment equal to his account balance, payable on a date
determined by the committee but not later than one year after the specified date
(or after the committee's receipt of satisfactory evidence of the termination of
the participant's employment).

6.5    INSTALLMENT DISTRIBUTIONS IN CERTAIN CASES.

       (a)    PARTICIPANT. Notwithstanding the provisions of Sections 6.2 and
6.4, a participant may, at the time of filing his initial enrollment form under
Section 4.1 (or, if applicable, in a subsequent election under Section 4.1(c) or
(d)), designate that the amount payable to him hereunder will be paid in a
number (minimum of two and maximum of ten) of annual installment payments, as
specified by the participant.

       (b)    BENEFICIARY. Notwithstanding Section 6.3, a participant may
designate that, if the participant dies before receiving the entire amount
payable to him hereunder, the beneficiary will receive either:

              (i)    A number of annual installment payments equal to:

                                       5
<PAGE>

                     (A)    the number the participant elected for himself under
                            subsection (a) above (if the participant dies before
                            receiving any installment payments), or

                     (B)    the number of remaining installment payments due to
                            the participant under subsection (a) above (if the
                            participant dies after receiving one or more
                            installment payments); or

              (ii)   a single payment.

       Payment to the beneficiary will be made or begin as provided in Section
6.3(a).

       If the participant fails to designate the form of payment to the
beneficiary, the default form will be installments under (i) above. If
installment payments are payable to the beneficiary, with the consent of the
committee, a participant may subsequently change the form of payment to his
beneficiary (but not the form of payment to himself under Section 6.2 or 6.4) to
a single payment by filing a written instrument so specifying with the
committee.

       (c)    INSTALLMENT PAYMENTS. Where installment payments are due, the
first annual installment payment will be paid out on the date specified in
Section 6.2, 6.3 or 6.4 (whichever is applicable) and subsequent annual
installments will be paid approximately on succeeding anniversaries of the first
payment date. The amount of each annual installment payment will be determined
by multiplying the total amount to be paid by a fraction whose numerator is one
and whose denominator is the number of remaining annual installment payments.

       (d)    DEATH OF BENEFICIARY. If a participant's designated beneficiary is
receiving installment payments and dies before receiving payment of all the
annual installments, the designated beneficiary's estate will receive a lump-sum
payment of the amount remaining to be distributed to such deceased beneficiary.
Such payment will be made as soon as practicable after the committee's receipt
of satisfactory evidence of the death of the designated beneficiary.

                                   ARTICLE 7
                                  MISCELLANEOUS

7.1    AMENDMENT OR TERMINATION OF PLAN. Biogen, by action of the Board (or such
committee thereof or officer or officers of Biogen to whom the Board has
delegated this authority), at any time and from time to time, may amend or
modify any or all of the provisions of this plan or may terminate this plan
without the consent of any participant (or beneficiary or other person claiming
through a participant). No termination or amendment of the plan may reduce the
amounts credited to the accounts of any participant under the plan (including a
participant whose employment with the employer was terminated before such
termination or amendment). However, Biogen may change the deemed investment
options under Section 5.1(c), and Biogen may upon termination of this plan pay
participants' account balances to the participants regardless of the times
elected for payment (or the start of installment payments) elected by the
participants and may pay such amounts in single sum payments regardless of
whether participants have elected installment distributions under Section 6.5.

7.2    BENEFITS NOT CURRENTLY FUNDED.

       (a)    Nothing in this plan will be construed to create a trust or to
obligate Biogen to segregate a fund, purchase an insurance contract or other
investment, or in any other way currently to fund the future payment of any
benefits hereunder, nor will anything herein be construed to give any
participant or any other person rights to any specific assets of Biogen or any
other entity. However, in order to make provision for its obligations hereunder,
Biogen may in its discretion purchase an insurance contract or other investment;
any such contract or investment will be a general asset belonging to Biogen, and
no participant or beneficiary will have any rights to any such asset. The rights
of a participant or beneficiary hereunder will be solely those of a general,
unsecured creditor of his employer.

       (b)    Notwithstanding subsection (a) above, Biogen in its sole
discretion may establish a grantor trust of which it is treated as the owner
under Code Section 671 to provide for the payment of benefits hereunder, subject
to

                                       6
<PAGE>

such terms and conditions as Biogen may deem necessary or advisable to ensure
that benefits are not includable, by reason of the trust, in the taxable income
of trust beneficiaries before actual distribution and that the existence of the
trust does not cause the plan or any other arrangement to be considered funded
for purposes of Title I of ERISA.

7.3    NO ASSIGNMENT. No participant or beneficiary will have any power or right
to transfer, assign, anticipate or otherwise encumber any benefit or amount
payable under this plan, nor shall any such benefit or amount payable be subject
to seizure or attachment by any creditor of a participant or a beneficiary, or
to any other legal, equitable or other process, or be liable for, or subject to,
the debts, liabilities or other obligations of a participant or beneficiary
except as otherwise required by law.

7.4    RESPONSIBILITIES AND AUTHORITY OF COMMITTEE. The committee will control
and manage the operation and administration of the plan except to the extent
that such responsibilities are specifically assigned hereunder to Biogen or the
Board.

       The committee will have all powers and authority necessary or appropriate
to carry out its responsibilities for the operation and administration of the
plan. It will have discretionary authority to interpret and apply all plan
provisions and may correct any defect, supply any omission or reconcile any
inconsistency or ambiguity in such manner as it deems advisable. It will make
all final determinations concerning eligibility, benefits and rights hereunder,
and all other matters concerning plan administration and interpretation. All
determinations and actions of the committee will be conclusive and binding upon
all persons, except as otherwise provided herein or by law, and except that the
committee may revoke or modify a determination or action previously made in
error. It is intended that any action or inaction by the committee will be given
the maximum possible deference by any reviewing body (whether a court or other
reviewing body), and will be reversed by such reviewing court or other body only
if found to be arbitrary and capricious.

       Biogen will be the "plan administrator" and the "named fiduciary" for
purposes of the Employee Retirement Income Security Act of 1974, as amended.

7.5    LIMITATION ON RIGHTS CREATED BY PLAN. Nothing appearing in the plan will
be construed (a) to give any person any benefit, right or interest except as
expressly provided herein, or (b) to create a contract of employment or to give
any employee the right to continue as an employee or to affect or modify his
terms of employment in any way.

7.6    TAX WITHHOLDING. Any payment hereunder to a participant or beneficiary
will be subject to withholding of income and other taxes to the extent required
by law.

7.7    TEXT CONTROLS. Headings and titles are for convenience only, and the text
will control in all matters.

7.8    APPLICABLE STATE LAW. To the extent that state law applies, the
provisions of the plan will be construed, enforced and administered according to
the laws of the Commonwealth of Massachusetts.

                                       7

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