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Exhibit 10.10

IDEC PHARMACEUTICALS CORPORATION
1988 STOCK OPTION PLAN

(Amended and Restated Through October 21, 2002)

        I.    PURPOSES OF THE PLAN    

        (a)  This Stock Option Plan (the "Plan") is intended to promote the
interests of IDEC Pharmaceuticals Corporation, a Delaware corporation (the
"Corporation"), by providing a method whereby key employees (including officers)
of the Corporation (or its parent or subsidiary corporations) responsible for
the management, growth and financial success of the Corporation (or its parent
or subsidiary corporations) may be offered incentives and rewards which will
encourage them to acquire a proprietary interest, or otherwise increase their
proprietary interest, in the Corporation and continue to render services to the
Corporation (or its parent or subsidiary corporations).

        (b)  The following provisions shall be applicable in determining the
parent and subsidiary corporations of the Corporation:

          (i)  Any corporation (other than the Corporation) in an unbroken chain
of corporations ending with the Corporation shall be considered to be a parent
corporation of the Corporation, provided each such corporation in the unbroken
chain (other than the Corporation) owns, at the time of the determination, stock
possessing fifty percent (50%) or more of the total combined voting power of all
classes of stock in one of the other corporations in such chain.

        (ii)  Each corporation (other than the Corporation) in an unbroken chain
of corporations beginning with the Corporation shall be considered to be a
subsidiary of the Corporation, provided each such corporation (other than the
last corporation) in the unbroken chain owns, at the time of the determination,
stock possessing fifty percent (50%) or more of the total combined voting power
of all classes of stock in one of the other corporations in such chain.

        II.    ADMINISTRATION OF THE PLAN    

        (a)  The Corporation's Board of Directors (the "Board") shall appoint a
committee ("Committee") of two (2) or more non-employee Board members to assume
full responsibility for the administration of the Plan. Members of the Committee
shall serve for such period of time as the Board may determine and shall be
subject to removal by the Board at any time.

        (b)  The Committee as Plan Administrator shall have full power and
authority (subject to the express provisions of the Plan) to establish such
rules and regulations as it may deem appropriate for the proper administration
of the Plan and to make such determinations under, and issue such
interpretations of, the Plan and any outstanding option grants or stock
issuances as it may deem necessary or advisable. Decisions of the Plan
Administrator shall be final and binding on all parties who have an interest in
the Plan or any outstanding option or stock issuance thereunder.

        III.    ELIGIBILITY FOR OPTION GRANTS    

        (a)  The persons eligible to receive option grants under the Plan shall
be limited tokey employees (including officers) of the Corporation (or its
parent or subsidiary corporations) who render services which contribute to the
success and growth of the Corporation (or its parent or subsidiary corporations)
or which may reasonably be anticipated to contribute to the future success and
growth of the Corporation (or its parent or subsidiary corporations).

        (b)  The Plan Administrator shall have full authority to determine which
eligible individuals are to receive option grants under the Plan, the number of
shares to be covered by each such grant, whether the granted option is to be an
incentive stock option ("Incentive Option") which satisfies the requirements of
Section 422 of the Internal Revenue Code or a non-statutory option

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not intended to meet such requirements, the time or times at which each such
option is to become exercisable, and the maximum term for which the option is to
be outstanding.

        IV.    STOCK SUBJECT TO THE PLAN    

        (a)  The stock issuable under the Plan shall be shares of the
Corporation's authorized but unissued or reacquired Common Stock. The maximum
number of shares which may be issued under the Plan shall not exceed 58,580,000
shares.* The total number of shares issuable under the Plan shall be subject to
adjustment from time to time in accordance with Section IV.(d) of the Plan.

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*Adjusted to reflect (i) the 1 for 2.5 reverse Common Stock split effected by
the Company on August 18, 1991, a 2 for 1 stock split effected by the
Corporation on December 21, 1999 and a 3 for 1 stock split effected in the form
of a stock dividend on January 17, 2001, (ii) the 4,020,000 share increase
authorized by the Board on March 18, 1992 and approved by the stockholders at
the 1992 Annual Meeting, (iii) the 4,200,000 share increase authorized by the
Board on January 13, 1993 and approved by the stockholders at the 1993 Annual
Meeting, (iv) the 3,900,000 share increase authorized by the Board on
February 28, 1994 and approved by the stockholders at the 1994 Annual Meeting,
(v) the 3,000,000 share increase authorized by the Board on January 25, 1995,
and approved by the stockholders at the 1995 Annual Meeting, (vi) the 7,200,000
share increase authorized by the Board on January 24, 1996, and approved by the
stockholders at the 1996 Annual Meeting, (vii) the 4,800,000 share increase
authorized by the Board on February 24, 1997, and approved by the stockholders
at the 1997 Annual Meeting, (viii) the 5,130,000 share increase authorized by
the Board on February 20, 1998, approved by the stockholders at the 1998 Annual
Meeting, (ix) the 4,800,000 share increase authorized by the Board on
January 13, 1999, approved by the stockholders at the 1999 Annual Meeting,
(x) the 5,130,000 share increase authorized by the Board on January 12, 2000,
approval at the 2000 Annual Meeting, (xi) the 5,640,000 share increase
authorized by the Board on January 16, 2001, approved by the stockholders at the
2001 Annual Meeting, and (xii) the 5,000,000 share increase authorized by the
Board on January 23, 2002, subject to stockholder approval at the 2002 Annual
Meeting. In no event, however, shall more than 30,707,067 shares of Common Stock
be issued under the Plan after February 28, 2002, inclusive of the 5,000,000
share increase for which stockholder approval is sought at the 2002 Annual
Meeting, subject to adjustment under Section IV(d) in the event of changes in
the Corporation's capital structure.

        (b)  In no event may the aggregate number of shares of Common Stock for
which any one individual participating in the Plan may be granted stock options
and separately exercisable stock appreciation rights exceed 7,500,000 shares in
the aggregate over the remaining term of the Plan, subject to adjustment from
time to time in accordance with Section IV.(d) of the Plan. For purposes of such
limitation, no stock options or stock appreciation rights granted prior to
January 1, 1994 shall be taken into account.

        (c)  Should an option expire or terminate for any reason prior to
exercise in full, the shares subject to the portion of the option not so
exercised shall be available for subsequent option grants under the Plan.
Unvested shares issued under the Plan and subsequently repurchased by the
Corporation, at the option exercise price paid per share, pursuant to the
Corporation's repurchase rights under the Plan, shall be added back to the
number of shares of Common Stock reserved for issuance under the Plan and shall
accordingly be available for reissuance through one or more subsequent option
grants under the Plan. Shares subject to any option cancelled in accordance with
Section VIII of the Plan shall reduce on a share-for-share basis the number of
shares of Common Stock available for subsequent option grants under this Plan.
In addition, should the exercise price of an outstanding option under the Plan
be paid with shares of Common Stock, then the number of shares of Common Stock
available for issuance under the Plan shall be reduced by the gross

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number of shares for which the option is exercised, and not by the net number of
shares of Common Stock actually issued to the option holder.

        (d)  In the event any change is made to the Common Stock issuable under
the Plan by reason of any stock split, stock dividend, combination of shares,
exchange of shares or other change affecting the outstanding Common Stock as a
class without the Corporation's receipt of consideration, then appropriate
adjustments shall be made to (I) the maximum number and/or class of securities
issuable under the Plan, (II) the maximum number and/or class of securities for
which stock options and separately exercisable stock appreciation rights may be
granted to any one participant in the aggregate after December 31, 1993 and
(III) the number and/or class of securities and exercise price per share in
effect under each outstanding option in order to prevent the dilution or
enlargement of benefits thereunder. The adjustments determined by the Plan
Administrator shall be final, binding and conclusive.

        V.    TERMS AND CONDITIONS OF OPTIONS    Options granted pursuant to the
Plan shall be authorized by action of the Plan Administrator and may, at the
Plan Administrator's discretion, be either Incentive Options or non-statutory
options. Each granted option shall be evidenced by one or more instruments in
the form approved by the Plan Administrator; provided, however, that each such
instrument shall comply with the terms and conditions specified below. Each
instrument evidencing an Incentive Option shall, in addition, be subject to the
applicable provisions of Section VI.

        1.    Option Price.    

        A.    The option price per share shall be fixed by the Plan
Administrator, but in no event shall the option price per share be less than one
hundred percent (100%) of the fair market value of a share of Common Stock on
the date of the option grant.

        B.    The option price shall become immediately due upon exercise of the
option and shall, subject to the provisions of Section IX and the instrument
evidencing the grant, be payable in one of the alternative forms specified
below:

        (i)    full payment in cash or check payable to the Corporation; or

        (ii)  full payment in shares of Common Stock held by the optionee for
the requisite period necessary to avoid a charge to the Corporation's reported
earnings and valued at fair market value on the Exercise Date (as such term is
defined below); or

        (iii)  full payment through a combination of shares of Common Stock held
by the optionee for the requisite period necessary to avoid a charge to the
Corporation's reported earnings and valued at fair market value on the Exercise
Date and cash or check payable to the Corporation; or

        (iv)  full payment effected through a broker-dealer sale and remittance
procedure pursuant to which the optionee shall provide irrevocable instructions
(I) to a Corporation-designated brokerage firm to (A) effect the immediate sale
of a sufficient number of the purchased shares to enable such firm to remit to
the Corporation, out of the sale proceeds available on the settlement date,
sufficient funds to cover the aggregate option price payable for the purchased
shares plus all applicable Federal and State income and employment taxes
required to be withheld by the Corporation in connection with such purchase and
(B) remit those funds to the Corporation on the settlement date, and (II) to the
Corporation to deliver the certificates for the purchased shares directly to
such brokerage firm.

        For purposes of this subparagraph B, the Exercise Date shall be the date
on which written or electronic notice of the option exercise is received by the
Corporation. Except to the extent the sale and remittance procedure is utilized
in connection with the exercise of the option, payment of the option price for
the purchased shares must accompany such notice.

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        C.    The fair market value per share of Common Stock on any relevant
date under subparagraph A or B (and for all other valuation purposes under the
Plan) shall be determined in accordance with the following provisions:

          (i)  If the Common Stock is not at the time listed or admitted to
trading on any national stock exchange but is traded on The Nasdaq Stock Market,
the fair market value shall be the closing selling price per share of Common
Stock on the date in question, as reported by the National Association of
Securities Dealers on The Nasdaq Stock Market and published in The Wall Street
Journal. If there is no reported closing selling price for the Common Stock on
the date in question, then the closing selling price on the last preceding date
for which such quotation exists shall be determinative of fair market value.

        (ii)  If the Common Stock is at the time listed or admitted to trading
on any national stock exchange, then the fair market value shall be the closing
selling price per share of Common Stock on the date in question on the stock
exchange determined by the Plan Administrator to be the primary market for the
Common Stock, as such price is officially quoted in the composite tape of
transactions on such exchange and published in The Wall Street Journal. If there
is no reported sale of Common Stock on such exchange on the date in question,
then the fair market value shall be the closing selling price on the exchange on
the last preceding date for which such quotation exists.

        2.    Term and Exercise of Options.    Each option granted under the
Plan shall be exercisable at such time or times, during such period, and for
such number of shares as shall be determined by the Plan Administrator and set
forth in the instrument evidencing such option; provided, however, that no such
option shall have a term in excess of ten (10) years from the grant date.

        3.    Limited Transferability of Options.    During the lifetime of the
optionee, Incentive Options shall be exercisable only by the optionee and shall
not be assignable or transferable other than by will or by the laws of descent
and distribution following the optionee's death. However, non-statutory options
may, in connection with the optionee's estate plan, be assigned in whole or in
part during the optionee's lifetime to one or more members of the optionee's
immediate family or to a trust established exclusively for one or more such
family members. The assigned portion may only be exercised by the person or
persons who acquire a proprietary interest in the option pursuant to the
assignment. The terms applicable to the assigned portion shall be the same as
those in effect for the option immediately prior to such assignment and shall be
set forth in such documents issued to the assignee as the Plan Administrator may
deem appropriate.

        4.    Effect of Termination of Service.    

        A.    Should an optionee cease to remain in Service (as defined in
subparagraph D below) for any reason (including death or permanent disability as
defined in Section 22(e)(3) of the Internal Revenue Code) while the holder of
one or more outstanding options granted to such optionee under the Plan, then
such option or options shall not (except to the extent otherwise provided
pursuant to Section X below) remain exercisable for more than a thirty-six
(36)-month period (or such shorter period determined by the Plan Administrator
and specified in the instrument evidencing the grant) following the date of such
cessation of Service. Under no circumstances, however, shall any such option be
exercisable after the specified expiration date of the option term. Each such
option shall, during such thirty-six (36)-month or shorter period, be
exercisable only to the extent of the number of shares (if any) for which the
option is exercisable on the date of the optionee's cessation of Service. Upon
the expiration of such thirty-six (36)-month or shorter period or (if earlier)
upon the expiration of the option term, the option shall terminate and cease to
be exercisable. However, the option shall, immediately upon the optionee's
cessation of Service for any reason, terminate and cease to be outstanding for
any option shares for which the option is not otherwise at that time
exercisable.

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        B.    Any outstanding option held by the optionee and exercisable in
whole or in part on the date of his or her death may be subsequently exercised,
but only to the extent of the number of shares (if any) for which the option is
exercisable on the date of the optionee's cessation of Service (less any option
shares subsequently purchased by the optionee prior to death), by the personal
representative of the optionee's estate or by the person or persons to whom the
option is transferred pursuant to the optionee's will or in accordance with the
laws of descent and distribution. The right to exercise the option for those
shares shall terminate upon the earlier of (i) the third anniversary of the date
of the optionee's cessation of Service or (ii) the specified expiration date of
the option term.

        C.    Notwithstanding subparagraphs A and B above, the Plan
Administrator shall have complete discretion, exercisable either at the time the
option is granted or at any time while the option remains outstanding, to permit
one or more options held by the optionee under the Plan to be exercised, during
the limited period of exercisability provided under Section V.4.A above, not
only with respect to the number of shares for which each such option is
exercisable at the time of the optionee's cessation of Service but also with
respect to one or more subsequent installments for which the option would
otherwise have become exercisable had such cessation of Service not occurred.

        D.    For purposes of the foregoing provisions of this Section V.4 (and
all other provisions of the Plan), the optionee shall be deemed to remain in the
Service of the Corporation for so long as such individual renders services on a
periodic basis to the Corporation or any parent or subsidiary corporation in the
capacity of an Employee, a non-employee member of the board of directors or an
independent consultant or advisor, unless the option agreement evidencing the
option grant and/or the purchase agreement evidencing the purchased option
shares specifically provides otherwise. The optionee shall be considered to be
an Employee for so long as such individual remains in the employ of the
Corporation or one or more of its parent or subsidiary corporations, subject to
the control and direction of the employer entity as to the work to be performed
and as to the manner and method of performance.

        5.    Stockholder Rights.    An optionee shall have none of the rights
of a stockholder with respect to any shares covered by the option until such
individual shall have exercised the option and paid the option price for the
purchased shares.

        6.    Repurchase Rights.    Unvested shares of Common Stock may be
issued under the Plan which are subject to repurchase by the Corporation in
accordance with the following provisions:

        (a)  Upon the optionee's cessation of Service while holding unvested
shares under the Plan, the Corporation shall have the right to repurchase any or
all of those unvested shares at the option price paid per share. The terms and
conditions upon which such repurchase right shall be exercisable (including the
period and procedure for exercise and the appropriate vesting schedule for the
purchased shares) shall be established by the Plan Administrator and set forth
in the instrument evidencing such repurchase right.

        (b)  All of the Corporation's outstanding repurchase rights shall
automatically terminate, and all shares subject to such terminated rights shall
immediately vest in full, upon the occurrence of any Corporate Transaction under
Section VII of this Plan, except to the extent: (i) any such repurchase right is
to be assigned to the successor corporation (or parent thereof) in connection
with the Corporate Transaction or (ii) such accelerated vesting is precluded by
other limitations imposed by the Plan Administrator at the time the repurchase
right is issued.

        (c)  The Plan Administrator shall have the discretionary authority,
exercisable either before or after the optionee's cessation of Service, to
cancel the Corporation's outstanding repurchase rights

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with respect to any or all unvested shares purchased or purchasable by the
optionee under the Plan and thereby accelerate the vesting of those shares in
whole or in part at any time.

        VI.    INCENTIVE OPTIONS.    

        The terms and conditions specified below shall be applicable to all
Incentive Options granted under the Plan. Incentive Options may only be granted
to individuals who are Employees. Options which are specifically designated as
"non-statutory" options when issued under the Plan shall not be subject to such
terms and conditions.

        (a)    Dollar Limitation.    The aggregate fair market value (determined
as of the respective date or dates of grant) of the Common Stock for which one
or more options granted to any Employee under this Plan (or any other option
plan of the Corporation or its parent or subsidiary corporations) may for the
first time become exercisable as incentive stock options under the Federal tax
laws during any one calendar year shall not exceed the sum of One Hundred
Thousand Dollars ($100,000). To the extent the Employee holds two or more such
options which become exercisable for the first time in the same calendar year,
the foregoing limitation on the exercisability of such options as incentive
stock options under the Federal tax laws shall be applied on the basis of the
order in which such options are granted. Should the number of shares of Common
Stock for which an Incentive Option first becomes exercisable in any calendar
year exceed the applicable One Hundred Thousand Dollar ($100,000) limitation,
the option may nevertheless be exercised for those excess shares in such
calendar year as a non-statutory option.

        (b)    10% Stockholder.    If any individual to whom the Incentive
Option is granted is the owner of stock (as determined under Section 424(d) of
the Internal Revenue Code) possessing ten percent (10%) or more of the total
combined voting power of all classes of stock of the Corporation or any one of
its parent or subsidiary corporations, then the option price per share shall not
be less than one hundred and ten percent (110%) of the fair market value per
share of Common Stock on the grant date, and the option term shall not exceed
five (5) years, measured from such grant date.

        Except as modified by the preceding provisions of this Section VI, all
the provisions of the Plan shall be applicable to the Incentive Options granted
hereunder.

        VII.    CORPORATE TRANSACTION/CHANGE IN CONTROL    

        (a)  In the event of any of the following transactions (a "Corporate
Transaction"):

        (i)    a merger or consolidation in which the Corporation is not the
surviving entity, except for a transaction the principal purpose of which is to
change the State of the Corporation's incorporation,

        (ii)  the sale, transfer or other disposition of all or substantially
all of the assets of the Corporation in liquidation or dissolution of the
Corporation, or

        (iii)  any reverse merger in which the Corporation is the surviving
entity but in which fifty percent (50%) or more of the Corporation's outstanding
voting stock is transferred to persons different from those who held the stock
immediately prior to such merger,

        each outstanding option under the Plan shall automatically accelerate so
that each such option shall, immediately prior to the specified effective date
for the Corporate Transaction, become exercisable for the total number of shares
of Common Stock at the time subject to such option and may be exercised for all
or any portion of those shares as fully-vested shares of Common Stock. However,
an outstanding option under the Plan shall not so accelerate if and to the
extent: (i) such option is, in connection with the Corporate Transaction, either
to be assumed by the successor corporation or parent thereof or be replaced with
a comparable option to purchase shares of the capital stock of the successor
corporation or parent thereof or (ii) the acceleration of

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such option is subject to other applicable limitations imposed by the Plan
Administrator at the time of grant. The determination of comparability under
clause (i) above shall be made by the Plan Administrator and its determination
shall be final, binding and conclusive.

        (b)  Each outstanding option under the Plan which is assumed in
connection with the Corporate Transaction or is otherwise to continue in effect
shall be appropriately adjusted, immediately after such Corporate Transaction,
to apply and pertain to the number and class of securities which would have been
issued, in consummation of such Corporate Transaction, to an actual holder of
the same number of shares of Common Stock as are subject to such option
immediately prior to such Corporate Transaction. Appropriate adjustments shall
also be made to the option price payable per share, provided the aggregate
option price payable for such securities shall remain the same. In addition, the
class and number of securities available for issuance under the Plan on both an
aggregate and per participant basis shall be appropriately adjusted to reflect
the effect of the Corporate Transaction upon the Corporation's capital
structure.

        (c)  In connection with any Change in Control (as defined below), the
Plan Administrator shall have full power and authority, exercisable either at
the time the option is granted or at any time while the option remains
outstanding, to provide for the automatic acceleration of each outstanding
option under the Plan so that each such option shall, immediately prior to the
effective date of the Change in Control, become exercisable for the total number
of shares at the time subject to such option and may be exercised for all or any
portion of those shares as fully-vested shares of Common Stock. The Plan
Administrator shall also have full power and authority to condition such option
acceleration, and the termination of any of the Corporation's repurchase rights
with respect to any unvested shares purchased or purchasable under the Plan,
upon the subsequent termination of the optionee's Service within a designated
period following the Change in Control.

        A Change in Control shall be deemed to occur in the event:

        (i)    twenty-five percent (25%) or more of the Corporation's
outstanding voting stock is acquired pursuant to a tender or exchange offer
(A) which is made directly to the Corporation's stockholders by any person or
related group of persons (other than the Corporation or a person that directly
or indirectly controls, is controlled by or is under common control with, the
Corporation) and (B) which the Board does not recommend the stockholders to
accept; or

        (ii)  there is a change in the composition of the Board over a period of
twenty-four (24) consecutive months or less such that a majority of the Board
members ceases, by reason of one or more proxy contests for the election of
Board members, to be comprised of individuals who either (A) have been Board
members continuously since the beginning of such period or (B) have been elected
or nominated for election as Board members during such period by at least a
majority of the Board members described in clause (A) who were still in office
at the time such election or nomination was approved by the Board.

        (d)  Immediately following the consummation of a Corporate Transaction,
all outstanding options under the Plan shall terminate and cease to be
outstanding, except to the extent assumed by the successor corporation or its
parent company. Upon a Change in Control, each outstanding option accelerated
pursuant to subsection VII.(c) above shall remain fully exercisable until the
expiration or sooner termination of the option term specified in the agreement
evidencing such grant.

        (e)  The exercisability as incentive stock options under the Federal tax
laws of any options accelerated in connection with a Corporate Transaction or
Change in Control shall remain subject to the dollar limitation of
Section VI.(a) of the Plan. To the extent such dollar limitation is

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exceeded, the accelerated option shall be exercisable as a non-statutory option
under the Federal tax laws.

        (f)    The grant of options under this Plan shall in no way affect the
right of the Corporation to adjust, reclassify, reorganize or otherwise change
its capital or business structure or to merge, consolidate, dissolve, liquidate
or sell or transfer all or any part of its business or assets.

        VIII.    STOCK APPRECIATION RIGHTS    

        (a)  Provided and only if the Plan Administrator determines in its
discretion to implement the stock appreciation right provisions of this
Section VIII, one or more optionees may be granted the right, exercisable upon
such terms and conditions as the Plan Administrator may establish, to surrender
all or part of an unexercised option under the Plan in exchange for a
distribution from the Corporation in an amount equal to the excess of (i) the
fair market value (on the option surrender date) of the number of shares in
which the optionee is at the time vested under the surrendered option (or
surrendered portion thereof) over (ii) the aggregate option price payable for
such vested shares.

        (b)  No surrender of an option shall be effective hereunder unless it is
approved by the Plan Administrator. If the surrender is so approved, then the
distribution to which the optionee shall accordingly become entitled under this
Section VIII may be made in shares of Common Stock valued at fair market value
on the option surrender date, in cash, or partly in shares and partly in cash,
as the Plan Administrator shall in its sole discretion deem appropriate.

        (c)  If the surrender of an option is rejected by the Plan
Administrator, then the optionee shall retain whatever rights the optionee had
under the surrendered option (or surrendered portion thereof) on the option
surrender date and may exercise such rights at any time prior to the later of
(i) five (5) business days after the receipt of the rejection notice or (ii) the
last day on which the option is otherwise exercisable in accordance with the
terms of the instrument evidencing such option, but in no event may such rights
be exercised more than ten (10) years after the date of the option grant.

        (d)  One or more officers of the Corporation subject to the short-swing
profit restrictions of the Federal securities laws may, in the Plan
Administrator's sole discretion, be granted limited stock appreciation rights in
tandem with their outstanding options under the Plan. Upon the occurrence of a
Hostile Take-Over, each outstanding option with such a limited stock
appreciation right shall automatically be cancelled, to the extent such option
is at the time exercisable for fully-vested shares of Common Stock (including
any shares which may vest in connection with such Hostile Take-Over). The
optionee shall in return be entitled to a cash distribution from the Corporation
in an amount equal to the excess of (i) the Take-Over Price of the vested shares
of Common Stock at the time subject to the cancelled option (or cancelled
portion of such option) over (ii) the aggregate exercise price payable for such
shares. The cash distribution payable upon such cancellation shall be made
within five (5) days following the consummation of the Hostile Take-Over. The
Plan Administrator shall pre-approve, at the time the limited stock appreciation
right is granted, the subsequent exercise of that right in accordance with the
terms of the grant and the provisions of this Section VIII.(d). No additional
approval of the Plan Administrator or the Board shall be required at the time of
the actual option cancellation and cash distribution. The balance of the option
(if any) shall continue to remain outstanding and exercisable in accordance with
the terms and conditions of the instrument evidencing such grant.

        (e)  For purposes of Section VIII.(d), the following definitions shall
be in effect:

        A Hostile Take-Over shall be deemed to occur in the event any person or
related group of persons (other than the Corporation or a person that directly
or indirectly controls, is controlled by, or is under common control with, the
Corporation) directly or indirectly acquires beneficial

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ownership (within the meaning of Rule 13d-3 of the Securities Exchange Act of
1934) of securities possessing more than twenty-five percent (25%) of the total
combined voting power of the Corporation's outstanding securities pursuant to a
tender or exchange offer made directly to the Corporation's stockholders which
the Board does not recommend such stockholders to accept.

        The Take-Over Price per share shall be deemed to be equal to the greater
of (a) the fair market value per share on the date of cancellation, as
determined pursuant to the valuation provisions of Section II.1.C, or (b) the
highest reported price per share paid by the acquiring entity in effecting such
Hostile Take-Over. However, to the extent the cancelled option is an Incentive
Option, the Take-Over Price shall not exceed the clause (a) price per share.

        (f)    The shares of Common Stock subject to any option surrendered or
cancelled for an appreciation distribution pursuant to this Section VIII shall
not be available for subsequent option grant under the Plan.

        IX.    LOANS OR INSTALLMENT PAYMENTS    

        The Plan Administrator may, in its discretion, assist any optionee
(other than any executive officer of the Corporation or member of the Board) in
the exercise of one or more options granted to such individual under the Plan,
including the satisfaction of any Federal and State income and employment tax
obligations arising therefrom, by (i) authorizing the extension of a loan from
the Corporation to such optionee or (ii) permitting the optionee to pay the
option price for the purchased Common Stock in installments over a period of
years. The terms of any such loan or installment method of payment (including
the interest rate and terms of repayment) will be upon such terms as the Plan
Administrator specifies in the applicable option agreement or otherwise deems
appropriate under the circumstances. Loans or installment payments may be
granted with or without security or collateral (other than to individuals who
are independent consultants or advisors, in which event the loan must be
adequately secured by collateral other than the purchased shares). However, the
maximum credit available to the optionee may not exceed the option price of the
acquired shares (less the par value of those shares) plus any Federal and State
income and employment withholding taxes to which theoptionee may become
subjectin connection with the exercise of the option.

        X.    EXTENSION OF EXERCISE PERIOD    

        The Plan Administrator shall have full power and authority, to extend
the period of time for which the option is to remain exercisable following the
optionee's cessation of Service from the thirty-six (36) month or shorter period
set forth in the option agreement to such greater period of time as the Plan
Administrator shall deem appropriate. In no event, however, shall such option be
exercisable after the specified expiration date of the option term.

        XI.    AMENDMENT OF THE PLAN    

        The Board shall have complete and exclusive power and authority to amend
or modify the Plan in any or all respects whatsoever; provided, however, that no
such amendment or modification shall, without the consent of the stockholders,
adversely affect rights and obligations with respect to options at the time
outstanding under the Plan. In addition, any amendment which increases the
number of shares of Common Stock authorized for issuance under the Plan or which
materially increases the benefits accruing to individuals participating in the
Plan shall require stockholder approval.

        XII.    EFFECTIVE DATE AND TERM OF PLAN    

        (a)  The Plan was initially adopted by the Board on July 19, 1988 and
approved by the Corporation's stockholders on March 29, 1989. The Plan was
subsequently amended by the Board on July 18, 1990, and such amendment was
approved by the Corporation's stockholders in October, 1990. In January 1991,
the Plan was again amended to increase by 2,880,000 shares the number of shares
of Common Stock issuable under the Plan, and such share increase was

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approved by the Corporation's stockholders on March 20, 1991. The Board further
amended the Plan on May 22, 1991, with such amendments to become effective as of
the date the Corporation's Common Stock first became traded on The Nasdaq Stock
Market, in order to revise certain provisions previously required when the Plan
was subject to the permit requirements of the California Corporations
Department. On March 18, 1992, the Plan was amended and restated in its
entirety, including an increase of 4,020,000 shares to the number of shares of
Common Stock issuable thereunder. The 1992 restatement, including the 4,020,000
share increase, was approved by the stockholders at the 1992 Annual Meeting. On
January 13, 1993, the Board amended the Plan to increase by an additional
4,200,000 shares the number of shares of Common Stock issuable under the Plan,
and such share increase was approved by the stockholders at the 1993 Annual
Meeting. On February 28, 1994, the Board amended the Plan to increase by an
additional 3,900,000 shares the number of shares of Common Stock issuable under
the Plan, and such increase was approved by the stockholders at the 1994 Annual
Meeting. On January 25, 1995, the Board amended the Plan to increase by an
additional 3,000,000 shares the number of shares of Common Stock issuable under
the Plan, and such increase was approved by the stockholders at the 1995 Annual
Meeting. On January 24, 1996, the Board adopted an amendment which increased the
number of shares of Common Stock issuable under the Plan by an additional
7,200,000 shares, and such increase was approved by the stockholders at the 1996
Annual Meeting.

        On February 24, 1997, the Board adopted a series of amendments to the
Plan (the "1997 Amendments") which (i) increased the number of shares of Common
Stock reserved for issuance over the term of the Plan by an additional 4,800,000
shares, (ii) rendered non-employee Board members serving as Plan Administrator
eligible to receive option grants under the Plan, (iii) allowed unvested shares
issued under the Plan and subsequently repurchased by the Corporation at the
option exercise price paid per share to be reissued under the Plan, (iv) removed
certain restrictions on the eligibility of non-employee Board members to serve
as Plan Administrator, (v) extended the term of the Option Plan from July 19,
1998 to December 31, 2002 and (vi) effected a series of additional changes to
the provisions of the Plan (including the stockholder approval requirements, the
transferability of non-statutory stock options and the elimination of the six
(6)-month holding period requirement as a condition to the exercise of stock
appreciation rights) in order to take advantage of the recent amendments to
Rule 16b-3 of the 1934 Act which exempts certain officer and director
transactions under the Plan from the short-swing liability provisions of the
Federal securities laws. The 1997 Amendments were approved by the Corporation's
stockholders at the 1997 Annual Meeting.

        On February 20, 1998, the Board authorized an increase of 5,130,000
shares of Common Stock to the share reserve under the Plan, and the stockholders
approved such increase at the 1998 Annual Meeting.

        On January 13, 1999, the Board authorized an increase of 4,800,000
shares of Common Stock to the share reserve under the Plan, and the stockholders
approved such increase at the 1999 Annual Meeting.

        On January 12, 2000, the Board adopted a series of amendments to the
Plan (the "2000 Amendments") which (i) increased the number of shares of Common
Stock reserved for issuance over the term of the Plan by an additional 5,130,000
shares; (ii) extend the term of the Option Plan from December 31, 2002 to
December 31, 2005; (iii) required the option price per share of Common Stock
subject to each option granted under the Option Plan to be not less than 100% of
the fair market value per share of Common Stock on the date of grant;
(iv) removed the non-employee Board members and all independent consultants from
the class of persons eligible to receive option grants under the Option Plan;
and (v) required the Plan Administrator to be a committee comprised only of
non-employee Board members. The 2000 Amendments were approved by the
Corporation's stockholders at the 2000 Annual Meeting.

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        On May 17, 2000, the Board further amended the Plan to eliminate the
Plan Administrator's authority to effect the cancellation and regrant of options
under the Plan.

        On January 16, 2001, the Board authorized an increase of 5,640,000
shares of Common Stock to the share reserve under the Plan, and the stockholders
approved such increase at the 2001 Annual Meeting.

        On January 23, 2002, the Board authorized an increase of 5,000,000
shares of Common Stock to the share reserve under the Plan. No options granted
on the basis of the 5,000,000 share increase shall vest or become exercisable
unless and until such share increase is approved by the stockholders at the 2002
Annual Meeting.

        On October 21, 2002, the Board amended the Plan to (i) require
stockholder approval of any amendments which increase the number of shares of
Common Stock authorized for issuance under the Plan or which materially increase
the benefits accruing to individuals participating in the Plan and
(ii) eliminate the authority of the Plan Administrator to make loans under the
Plan to executive officers of the Corporation or Board members.

        (b)  The provisions of the 1992 restatement and of each subsequent
amendment to the Plan shall apply only to stock options and stock appreciation
rights granted under the Plan from and after the applicable effective date of
such restatement or amendment. All stock options and stock appreciation rights
issued and outstanding under the Plan immediately prior to each such effective
date shall continue to be governed by the terms and conditions of the Plan (and
the respective agreements evidencing each such option or stock appreciation
right) as in effect on the date each such option or stock appreciation right was
previously granted, and nothing in the 1992 restatement or in any subsequent
amendment shall be deemed to affect or otherwise modify the rights or
obligations of the holders of such prior options or stock appreciation rights
with respect to their acquisition of shares of Common Stock under such options
or their exercise of such stock appreciation rights. However, the Plan
Administrator may, in its discretion, modify stock option or stock appreciation
right issued and outstanding immediately prior to the effective date of the 1992
restatement or any subsequent amendment to include one or more provisions to the
Plan added by such restatement or amendment.

        (c)  Unless sooner terminated in accordance with Section VII, the Plan
shall terminate upon the earlier of (i) December 31, 2005 or (ii) the date on
which all shares available for issuance under the Plan shall have been issued or
cancelled pursuant to the exercise, surrender of cash-out of the stock options
and stock appreciation rights granted hereunder. If the date of termination is
determined under clause (i) above, then each stock option or stock appreciation
right outstanding on such date shall thereafter continue to have force and
effect in accordance with the provisions of the instruments evidencing such
grant.

        (d)  Options may be granted under this Plan to purchase shares of Common
Stock in excess of the number of shares then available for issuance under the
Plan, provided any excess shares actually issued under the Plan are held in
escrow until stockholder approval is obtained for a sufficient increase in the
number of shares available for issuance under the Plan. If such stockholder
approval is not obtained within twelve (12) months after the date the first such
excess option grants are made, then (I) any unexercised excess options shall
terminate and cease to be exercisable and (II) the Corporation shall promptly
refund the purchase price paid for any excess shares actually issued under the
Plan and held in escrow, together with interest (at the applicable Short Term
Federal Rate) for the period the shares were held in escrow.

        XIII.    USE OF PROCEEDS    

        Any cash proceeds received by the Corporation from the sale of shares
pursuant to options granted under the Plan shall be used for general corporate
purposes.

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        XIV.    REGULATORY APPROVALS    

        The implementation of the Plan, the granting of any stock option or
stock appreciation right hereunder, and the issuance of stock upon the exercise
of any such option or stock appreciation right shall be subject to the
procurement by the Corporation of all approvals and permits required by
regulatory authorities having jurisdiction over the Plan, the options and stock
appreciation rights granted under it and the stock issued pursuant to it.

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QuickLinks

Exhibit 10.10

IDEC PHARMACEUTICALS CORPORATION 1988 STOCK OPTION PLAN (Amended and Restated
Through October 21, 2002)