AMENDMENTS TO BYLAWS OF IDEC PHARMACEUTICALS CORPORATION -- NOVEMBER 12, 2003

1.       The first sentence of Section 2 of Article III of the Bylaws is hereby
         amended and, as so amended, restated to read as follows:

                  "Vacancies and new created directorships resulting from any
                  increase in the authorized number of directors may be filled
                  by a majority of the directors then in office, though less
                  than a quorum, or by a sole remaining director, and any
                  additional director of any class so elected to fill a vacancy
                  or new directorship shall hold office for a term that hall
                  coincide with the remaining term of that class."

2.       Section 5 of Article V of the Bylaws is hereby amended and, as so
         amended, restated to read in its entirety as follows:

                           Section 5. The officers of the corporation shall hold
                  office until their successors are chosen and qualify. Any
                  officer elected or appointed by the Board of Directors may be
                  removed at any time by the affirmative vote of a majority of
                  the Board of Directors; provided, however, that until November
                  12,2006, the affirmative vote, at a duly convened meeting of
                  the Board of Directors, of at least 80% of the entire Board of
                  Directors (excluding for this purpose directors who are then
                  serving as an officer or employee of the corporation) shall be
                  required (a) to remove William H. Rastetter, Ph.D. from the
                  office of Executive Chairman or significantly diminish his
                  position, authority, duties or responsibilities or (b) to
                  remove James C. Mullen from the office of Chief Executive
                  Officer or President or significantly diminish his position,
                  authority, duties or responsibilities.

3.       Section 1 of Article VIII of the Bylaws is hereby amended and, as so
         amended, restated to read in its entirety as follows:

                           Section 1. These bylaws may be altered, amended or
                  repealed, in whole or in part, or new bylaws may be adopted by
                  the stockholders or by the Board of Directors; provided,
                  however, that notice of such alteration, amendment, repeal or
                  adoption of new bylaws be contained in the notice of such
                  meeting of the stockholders or the Board of Directors, as the
                  case may be. Any such alteration, amendment, repeal or
                  adoption must be approved by either the vote of the holders of
                  a majority of the stock issued and outstanding and entitled to
                  vote thereon or by a majority of the entire Board of
                  Directors; provided, however, that until November 12, 2006,
                  any such alteration, amendment, repeal or adoption by the
                  Board of Directors must be approved by the affirmative vote of
                  at least 80% of the entire Board of Directors (excluding for
                  this purpose directors who are officers or employees of the
                  corporation) if it would amend or modify, or be inconsistent
                  with, the requirements specified in Section 5 of Article V of



                           these Bylaws (a) to remove William H. Rastetter,
                           Ph.D. from the office of Executive Chairman or
                           significantly diminish his position, authority,
                           duties or responsibilities or (b) to remove James C.
                           Mullen from the office of Chief Executive Officer or
                           President or significantly diminish his position,
                           authority, duties or responsibilities.