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                                                                   Exhibit 10.35

                          FIFTH AMENDMENT TO AGREEMENT

      THIS FIFTH AMENDMENT TO AGREEMENT ("Fifth Amendment") is made and
effective as of this 17th day of December, 2003, by and between MDS (CANADA)
INC., MDS NORDION division, successor to MDS NORDION INC. ("Nordion"), and
Biogen Idec Inc. ("Biogen Idec") (formerly IDEC Pharmaceuticals Corporation).

WHEREAS:

      A.    Nordion and Biogen Idec are parties to that certain Agreement dated
            May 14, 1999, whereby Nordion agreed to manufacture and supply
            Isotope for use with Biogen Idec's Labelled Drug ("Original
            Agreement").

      B.    The Original Agreement was subsequently amended by a 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 22, 2001 ("Second
            Amendment"), a Third Amendment to Agreement dated November 12, 2001
            ("Third Amendment") and a Fourth Amendment to Agreement dated June
            10, 2003 ("Fourth Amendment"). The Original Agreement, as amended by
            the First Amendment, Isotope Dose Size Letter, Second Amendment,
            Third Amendment and Fourth Amendment are collectively referred to
            herein as the "Agreement."

      C.    Nordion, Biogen Idec and Union Bank of California, N.A. (the "Escrow
            Agent") are also parties to that certain Escrow Agreement dated
            November 12, 2001 ("Escrow Agreement").

      D.    Nordion and Biogen Idec desire to further amend the Agreement as set
            forth in this Fifth Amendment.

      E.    Capitalized terms used, but not otherwise defined herein, shall have
            the meanings ascribed to them in the Agreement.

NOW THEREFORE, in consideration of the mutual covenants and agreements herein
contained the sufficiency of which is hereby acknowledged, the parties agree as
follows:

1.    PAYMENT. IDEC acknowledges that Nordion has made a significant investment
      in Isotope facilities and manufacturing capabilities at both its
      facilities in Canada and Belgium in order to meet Biogen Idec's projected
      demand for Isotope. In consideration of such investment and elimination of
      Biogen Idec's minimum purchase commitments under the Agreement, Biogen
      Idec has agreed, upon execution of this agreement, to pay Nordion TWENTY
      FIVE MILLION US DOLLARS (US$25,000,000). Nordion and Biogen Idec have
      agreed that Biogen Idec shall be permitted to pay such amount out of the
      escrow account established pursuant to the Escrow Agreement. In order to
      effect such payment Nordion and Biogen Idec agree to execute a written
      request to the Escrow Agent, in substantially the form attached hereto as
      Annex "A," instructing the Escrow Agent to (i) immediately pay TWENTY FIVE
      MILLION US DOLLARS (US$25,000,000) to Nordion out of escrow and (ii)
      disburse all remaining funds in
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      escrow to Biogen Idec. Such payment of funds to Nordion shall be
      non-reimbursable and Biogen Idec shall not be permitted to file any
      objection to such disbursement with the Escrow Agent or otherwise.

2.    TERMINATION AND AMENDMENT OF AGREEMENT PROVISIONS.

      2.1   The Fourth Amendment is hereby deleted in its entirety and shall
            have no further force or effect.

      2.2   The last sentence in Section 1.4 and Sections 7.1, 7.2 and 7.4 and
            Articles 2, 3, 4, 5 and 6, of the Third Amendment are hereby deleted
            in their entirety and shall have no further force or effect.

      2.3   Articles 2, 3, 4, 5 and 6 of the Second Amendment are hereby deleted
            in their entirety and shall have no further force or effect.

      2.4   The last sentence in Section 7.1(ii), Sections 7.1(iii) and 7.2(iii)
            of the Original Agreement are hereby deleted in their entirety and
            shall have no further force or effect.

      2.5   Section 7.1(i) of the Original Agreement is hereby amended and
            restated in its entirety to read as follows:

            "(i) During the Commercial Phase Nordion shall manufacture and
            supply Isotope to Biogen Idec for use in Clinical Trials under
            Biogen Idec's IND in the United States and Biogen Idec's or its
            designee's IND or equivalents in Canada and Europe, and for
            commercial sale in Canada and the United States. Biogen Idec shall,
            beginning at the start of the Commercial Phase and ending at the end
            of the Initial Term, purchase from Nordion all of Biogen Idec's and
            its Affiliates, requirements for Isotope for use with the Monoclonal
            Antibody in the United States. In addition, for the period beginning
            at the start of the Commercial Phase and ending at the end of the
            Initial Term Biogen Idec shall cause any third party who licenses or
            otherwise acquires from Biogen Idec the rights to market or sell
            Labelled Drug ("Third Party Marketing Partner"), to purchase from
            Nordion all of its requirements for Isotope for use with the
            Monoclonal Antibody in the United States. Except as otherwise set
            out in this agreement, beginning at the start of the Commercial
            Phase and ending at the end of the Initial Term, Biogen Idec agrees
            that it shall not, nor permit its Affiliates or Third Party
            Marketing Partner to, directly or indirectly, purchase or acquire
            Isotope from any third party, for use with the Monoclonal Antibody
            in the United States. Nordion shall ship Isotope to Biogen Idec or
            as otherwise directed by Biogen Idec or its designee. Isotope shall
            meet the Specifications and shall be manufactured in accordance with
            cGMPs. During the Commercial Phase, except as provided in Section
            7.4, Nordion will manufacture and supply sufficient quantities of
            Isotope required to meet weekly demand for Isotope and will exercise
            reasonable business judgement in selecting which of its facilities
            will supply Isotope in sufficient quantities to meet demand. Nordion
            will ship Isotope at Biogen Idec's direction on Tuesdays and
            Wednesdays and such other days as agreed. Each Batch shall contain
            such amount of Isotope to meet Biogen Idec's requirements as set out
            in Section 7.4

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            below. Biogen Idec acknowledges that delivery of Isotope is handled
            by third party carriers, however, Nordion will strive to meet
            delivery by its third party carriers at or prior to 8:00 a.m. at the
            destination on the day of delivery. Notwithstanding the foregoing,
            Biogen Idec acknowledges that, as a result of carrier flight
            scheduling and/or customer location, delivery of Isotope to certain
            customers may not be achievable at or prior to 8:00 am, or if so
            achievable, may be so achieved only at carrier rates in excess of
            those carrier rates that may be reasonably acceptable to Biogen
            Idec. For such customer locations to which Biogen Idec requests
            delivery, Nordion shall advise Biogen Idec whether 8:00 am delivery
            is achievable by the carrier and Biogen Idec shall provide
            instructions to Nordion.

            In the event delivery of Isotope is delayed beyond its scheduled
            delivery time and is not used as a direct result of late delivery
            Nordion * * * * *.*

      2.6   Section 11.1 of the Original Agreement is hereby amended such that
            the reference to Section 7.1 (iii) therein, is deleted.

      2.7   Section 17.3 of the Original Agreement is hereby amended and
            restated in its entirety to read as follows:

            "17.3 Termination Without Cause

            Neither Party shall have the unilateral right to terminate this
            Agreement without cause during the Initial Term, provided further
            however, that either Party may provide written notice of termination
            in accordance with Section 17.2. In the event this Agreement is
            extended pursuant to Section 17.2 hereof, during any extension
            thereof (i) Nordion may provide written notice and terminate this
            agreement without cause or penalty upon twenty four (24) months
            prior written notice to Biogen Idec and (ii) Biogen Idec may provide
            written notice and terminate this agreement without cause upon six
            (6) months prior written notice to Nordion."

            For the purposes of certainty section 17.2 of the Original Agreement
            is reinstated.

3     BLA SUBMISSION FOR KRMF. Biogen Idec has prepared and submitted a
      supplemental BLA to the FDA in support of the KRMF Facility with respect
      to Isotope. Biogen Idec agrees to use commercially reasonable efforts to
      obtain FDA approval of such BLA submission in an expeditious manner.

4     NO FURTHER MODIFICATION. Except as set forth in this Fifth Amendment, all
      other terms and conditions of the Agreement shall remain unmodified and in
      full force and effect.





--------
* Confidential information omitted and filed separately with the Securities and
Exchange Commission.

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5     EFFECTIVE DATE. This Fifth Amendment shall be effective as of the date
      first above written.

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

MDS (CANADA) INC.,
MDS Nordion division               Biogen Idec Inc.

By  /s/ Iain Trevana               By /s/ Paul Grint
   ------------------------           ------------------------------------------

Its  Senior Vice President,        Its  Senior Vice President, Oncology
     Nuclear Medicine                   Business Unit
     ----------------------             ----------------------------------------

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                                    Annex "A"

                         Written Request to Escrow Agent

VIA FACSIMILE AND FEDERAL EXPRESS

Union Bank of California, N.A.
120 S. San Pedro Street, 4th Floor
Los Angeles, CA  90012
Attn:  Corporate Trust Department
Facsimile:  (213) 972-5694


To Whom It May Concern:

Reference is made to that certain Escrow Agreement dated as of November 12, 2001
by and among IDEC Pharmaceuticals Corporation (now Biogen Idec Inc.), MDS
(Canada) Inc., MDS Nordion division, successor to MDS Nordion Inc. and Union
Bank of California, N.A. (the "Escrow Agreement"). Pursuant to Section 1.3 and
notwithstanding the provisions of Section 1.4 of the Escrow Agreement, you are
hereby requested to disburse funds held in Account #6711676400 as follows:

      1.    Twenty Five Million U.S. Dollars ($25,000,000US) to MDS Nordion,
            SWIFT Code CIBCCATT, Field57://CC001000006, Canadian Imperial Bank
            of Commerce, 119 Sparks Street, Ottawa, Ontario, Canada, Field
            59:/02-19118, MDS Nordion; and

All funds remaining after the foregoing disbursement to Biogen Idec, Silicon
Valley Bank, Santa Clara, CA USA, ABA #121140399, Credit Account #33001-46170,
Biogen Idec Incorporated. Inasmuch as all parties to the Escrow Agreement have
consented herein to the above disbursement, you are hereby requested to effect
immediate disbursement without giving regard to the provisions of Section 1.4 of
the Escrow Agreement requiring up to a five (5) delay thereof.

Upon disbursement of the foregoing funds, pursuant to Section 1.7 of the Escrow
Agreement, the Agreement shall be terminated.

Thank you for your assistance. Please call the undersigned with any questions.

Sincerely,

MDS (CANADA) INC.,
MDS Nordion division                Biogen Idec Inc.

By__________________________        By_____________________________________

Its____________________             Its_____________________________________


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