New Safety Information Regarding Liver Injury and Hypersensitivity Associated with TYSABRI (natalizumab)

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PUBLIC COMMUNICATION Health Canada Endorsed Important Safety Information on TYSABRI (natalizumab)

June 2, 2008

Subject: Reports of liver injury and allergic reactions with TYSABRI^TM (natalizumab)

Following discussions with Health Canada, Biogen Idec wishes to provide you with important new safety information regarding the risk of liver injury and allergic reactions in patients receiving TYSABRI^TM. This communication is also notifying you of updated safety information on herpes infections.

TYSABRI^TM is used to treat patients with a form of multiple sclerosis called relapsing-remitting (periods of symptoms alternating with periods without symptoms).

Liver Problems:

• There have been some reports of serious liver injury in patients receiving TYSABRI^TM. Some cases have occurred in patients who already had liver problems or were also taking drugs or other products that can cause liver problems.
• If signs and symptoms of liver problems occur, TYSABRI^TM treatment should be suspended until the cause can be identified. If an alternative cause for liver problems cannot be found, therapy should be permanently stopped.

Allergic Reactions:

• The risk of an allergic reaction to TYSABRI^TM is increased in patients who may have taken TYSABRI^TM for a short period followed by a long break in therapy and then resumed taking TYSABRI^TM.

Patients should call their doctor right away if they experience any of the following signs and symptoms:

Liver Problems:

• Unusual darkening of the urine
• Nausea and vomiting
• Feeling tired or weak
• Yellowing of the skin and eyes (jaundice)

Allergic Reactions:

• Itchy rash (hives)
• Swelling of the face, lips or tongue
• Difficulty breathing

Herpes Infections:

• Herpes infections, such as shingles, have been rarely reported in association with post-market use of TYSABRI^TM. These infections need to be successfully treated before TYSABRI^TM is continued.

This advisory is in addition to a letter issued to health care professionals concerning the same information. The letter can be found on Health Canada's website.

The Canadian prescribing information for TYSABRI^TM has been updated to include new information in the Warnings and Precautions for liver problems and allergic reactions and in the Adverse Reaction section and Consumer Information section for herpes infections. The prescribing information is available by contacting the Tysabri Care Program^TM.

Managing marketed health product-related adverse reactions depends on health care professionals and consumers reporting them. Reporting rates determined on the basis of spontaneously reported post-marketing adverse reactions are generally presumed to underestimate the risks associated with health product treatments. Any case of serious liver symptoms or other serious or unexpected adverse reactions in patients receiving TYSABRI^TM should be reported to the Tysabri Care Program^TM or Health Canada at the following addresses:

Sincerely,

original signed by

Dr. Len Walt, M.D., M.B.A.
Medical Director