Item 8.01 Other Events.
On October 29, 2008, relevant regulatory agencies were notified of a confirmed case of progressive multifocal leukoencephalopathy (PML) in a multiple sclerosis (MS) patient treated with TYSABRI® in the commercial setting in the United States. Additional information about this case is set forth below.
• The diagnosis was made based upon the detection of JC Virus (JCV) DNA in the cerebrospinal fluid (CSF) in the setting of clinical signs, symptoms and magnetic resonance imaging (MRI) findings consistent with the diagnosis of PML.

• Background:

- Patient has a history of MS and prior disease modifying therapies, including beta-interferons and glatiramer acetate.

- Patient had also received prior therapy with methotrexate for a rheumatological condition.

- Patient received 14 infusions of TYSABRI monotherapy.

- Clinical vigilance led to early identification of signs and symptoms of possible PML and to clinical evaluation which included MRI scanning and CSF testing.

- Patient is under the care of patient's treating physician.