WASHINGTON (AP) — The Food and Drug Administration says it has approved a new diagnostic test to help identify patients who have an increased risk of developing a rare brain infection while taking Biogen Idec's multiple sclerosis drug Tysabri.
Tysabri is one of a handful of drugs used to control multiple sclerosis, a debilitating disease in which the body attacks its own nervous system. Prescribing of the drug has been tightly controlled by the FDA because of a rare side effect that causes fatal inflammation of the brain.
The newly approved Stratify JCV test is designed to detect a common virus that increases patients' chances of developing the brain infection. The virus is harmless in most patients, but can become dangerous in patients taking immune system-suppressing drugs like Tysabri.