TUESDAY, Jan. 15 (HealthDay News) -- Tysabri (natalizumab) has been approved by the U.S. Food and Drug Administration to treat moderate-to-severe Crohn's disease in people who haven't responded to other therapies.

Tysabri, made by the Ireland-based drugmaker Elan and Massachusetts-based Biogen Idec, was approved in 2006 to treat relapsing multiple sclerosis.

The drug has a boxed warning of increased risk of progressive multifocal leukoencephalopathy (PML), a viral infection affecting the brain that could cause severe disability or death, the FDA said in a statement. Anaphylactic reactions and liver injury also have been reported in some users.

Crohn's patients prescribed the drug will be enrolled in a restricted distribution program called Crohn's Disease-Tysabri Outreach Unified Commitment to Health (CD-TOUCH). Under the program, physicians must evaluate Crohn's patients using Tysabri after three months and should discontinue use of the drug if there is no improvement, the FDA said.

Crohn's is an incurable bowel disease with symptoms that may include diarrhea, fever, rectal bleeding, malnutrition, narrowing of the intestines, cramping, and abdominal pain. The disease, affecting more than 1 million people worldwide, can also lead to abnormal connections called fistulas from the intestines to the skin or internal organs.

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