SydneyAcquisitions ULC Millennium Pharmaceuticals, Inc. 40 Lansdowne Street Cambridge, Massachusetts 02139

Sydney Acquisitions ULC
Millennium Pharmaceuticals, Inc.
40 Lansdowne Street
Cambridge, Massachusetts
02139

DELIVERED AND                                                                                                                                October 17, 2006
BY FACSIMILE (212 ###-###-####)

Baker Bros. Investments, L.P.
Baker Bros. Investments II, L.P.
Baker Biotech Fund I, L.P.
14159, L.P.
Baker/Tisch Investments, L.P.
Baker Brothers Life Sciences L.P.
(each person a “Shareholder” and
collectively the “Shareholders”)
c/o Baker Brothers Investments
667 Madison Avenue, 17th Floor
New York, NY 10021

We are writing with respect to the above-captioned Shareholder Support Agreement.  Capitalized terms used but not defined in this letter have the meanings assigned to them in the Shareholder Support Agreement.

This letter is written to set out our mutual agreement pursuant to Section 5.3 of the Shareholder Support Agreement that the Shareholder Support Agreement will terminate and be of no further force or effect, effective at 12:01 a.m. (Vancouver time) today.  We acknowledge that the Shareholders will enter into a shareholder support agreement with Genzyme Corporation and Dematal Corp.

Each of the parties hereby confirm to the other the same representations and warranties as to their power and authority to enter into and the binding nature of this agreement as if the representations and warranties given under Sections 4.1(a) and (c) and Sections 4.2(a), (b) and (c) of the Shareholder Support Agreement apply to the agreement reflected in this letter.  The parties also confirm their intention that Section 6.8 (governing law), Section 6.9 (attornment) and Section 6.17 (counterpart execution) of the Shareholder Support Agreement will apply to the agreement reflected in this letter.

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We trust the foregoing adequately confirms our agreement with respect to the termination of our Shareholder Support Agreement.  Could you please sign and return a copy of this letter to confirm your agreement.

Yours truly,