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                                                                        EX-10.34

                          FOURTH AMENDMENT TO AGREEMENT

This Fourth Amendment to Agreement ("Fourth Amendment") is made and entered into
by and between MDS (Canada) Inc., MDS Nordion division ("Nordion") and IDEC
Pharmaceuticals Corporation ("IDEC"), effective as of June 10, 2003.

WHEREAS:

A.       Nordion and IDEC are parties to that certain Agreement dated May 14,
         1999 (the "Isotope Agreement").

B.       The Isotope Agreement was subsequently amended by letter agreement
         between the parties dated January 25, 2000 ("First Amendment"), a
         letter agreement between the parties dated March 21, 2000 relating to
         Isotope dose size ("Isotope Dose Size Letter"), a letter Agreement
         between the parties dated March 27, 2001 ("Second Amendment"), and an
         agreement between the parties dated November 12, 2001 ("Third
         Amendment"). The Isotope Agreement, as amended by the First Amendment,
         Isotope Dose Size Letter, Second Amendment and Third Amendment are
         collectively referred to herein as the "Agreement."

C.       Nordion and IDEC desire to further amend the Agreement as set forth in
         this Fourth Amendment.

D.       Unless otherwise defined herein capitalized items as used herein shall
         have the meanings as given thereto in the Agreement.

NOW THEREFORE in consideration of covenants and agreements herein contained, and
subject to the terms and conditions hereinafter set out the parties agree as
follows:

1.       Section 3.3 of the Third Amendment shall be amended and restated in its
         entirety as follows:

         "In the event Nordion has not submitted an updated DMF for the KRMF
         Facility to the FDA on or before January 12, 2004, IDEC's $55,000,000
         US cumulative Commercial Phase minimum purchase commitment set forth in
         Section 3.1 above and the $55,000,000 US amount associated with the
         Cumulative Revenue Date shall each be reduced by $5,000,000 US and
         shall continue to be reduced by $5,000,000 US on the 12th day each
         month following January 12, 2004 until the updated DMF is submitted,
         provided, however, in no event shall such reductions cause the
         cumulative Commercial Phase minimum purchase requirement and amount
         associated with the Cumulative Revenue Date to fall below $25,000,000
         US. Attachment 1, incorporated herein by reference, sets forth the
         Commercial Phase minimum purchase commitment schedules as so reduced by
         $5,000,000 increments.

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2.       Section 3.4 of the Third Amendment shall be amended and restated in its
         entirety as follows:

         "In the event Nordion has not established the capability to commence
         commercial supply of Isotope from the KRMF Facility by October 12,
         2004, provided and to the extent such delay is not the result of the
         failure by IDEC to submit a supplemental BLA to the FDA for the purpose
         of FDA KRMF Facility regulatory approval as provided in Section 3.3,
         IDEC's $55,000,000 US cumulative Commercial Phase minimum purchase
         commitment and the $55,000,000 US amount associated with the Cumulative
         Revenue Date, as the same may have been reduced pursuant to Section 3.3
         above, shall each be further reduced by $5,000,000 US on the 12th day
         of each month following October 12, 2004 until the date by which
         Nordion is capable of commercially supplying Isotope from the KRMF
         Facility. In any event, IDEC will use its good faith efforts to prepare
         and submit a supplemental BLA to the FDA within ten (10) business days
         after Nordion's submission of its DMF, unless IDEC reasonably
         determines that would not be in its best interest to do so for
         regulatory reasons, in which case IDEC shall submit such supplemental
         BLA as soon as reasonably practicable thereafter. In no event shall
         such reductions cause the cumulative Commercial Phase minimum purchase
         commitment and the amount associated with the Cumulative Revenue Date
         to fall below $25,000,000 US. Attachment 1, incorporated herein by
         reference, sets forth the Commercial Phase minimum purchase commitment
         schedules as so reduced by $5,000,000 increments."

3.       All other terms and conditions in the Third Amendment and the Agreement
         shall remain in full force and effect.

IN WITNESS WHEREOF, the parties hereto have executed this Fourth Amendment
effective as of the date first above written.

MDS (CANADA) INC.,                      IDEC PHARMACEUTICALS CORPORATION
MDS Nordion division

By: /s/ [ILLEGIBLE]                     By: /s/ Mark Wiggins
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