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Friday, 20 January 2012

FDA approves test to help screen for risk of rare brain infection

Multiple sclerosis patients using Biogen Idec (NASDAQ:BIIB) drug Tysabri now have access to the first test that can help determine their risk for developing a rare but potentially fatal brain infection that affects some patients using the drug.


The U.S. Food and Drug Administration today cleared the blood test which can help doctors determine whether MS patients as well as Crohn’s disease patients, who are also prescibed the drug, could develop progressive multifocal leukoencephalopathy, or PML. PML has no cure. The risk for the infection means that Tysabri carries a black box warning.


The FDA also granted Weston, Massachusetts-based Biogen Iden a label change for Tysabri that updates the risk factors of developing PML for MS and Crohn’s disease patients. RBC Capital Markets analyst Michael Yee told Bloomberg News that the label change could push Tysabri’s global sales to $2.5 billion to $3 billion by 2016. Without the label change, sales could top out at $2 billion in 2106.
Biogen makes Tysabri at its manufacturing facility in Research Triangle Park, North Carolina. The drug is marketed with drug partner Elan (NYSE:ELN), who splits revenue with Biogen. Biogen’s share of 2011 Tysabri revenue through the third quarter was $810 million.


The new test measures the presence of antibodies for the John Cunningham virus, or JCV. The FDA said that while the virus is common and generally harmless, people who have weakened immune systems from therapies such as Tysabri have an increased risk of developing PML. Patients at greatest risk of developing PML are those who have been exposed to JCV; have been treated with Tysabri for longer than two years; and are treated with medicines that can weaken their immune systems.


“PML is a fatal infection reported in patients undergoing immunomodulatory therapy,” Alberto Gutierrez, director of the Office of In Vitro Diagnostics in the FDA’s Center for Devices and Radiological Health said in a statement. “This test gives doctors an additional means to determine if MS or CD patients undergoing Tysabri therapy are at increased risk for developing PML.


The newly approved Stratify JCV test is designed to detect a common virus that increases the likelihood of developing the brain infection. The John Cunningham virus is harmless in most people, but can become dangerous in patients taking immune system-suppressing drugs like Tysabri.


Doctors can use the results of the blood-based test, combined with facts about the patient's medical history, to determine whether they are at risk of developing the brain infection. Other factors that influence a patient's risk include how long they've been taking Tysabri and whether they've previously taken other medications that weaken the immune system.


The test was developed by Quest Diagnostics.


The FDA also updated Tysabri's label to specify that patients who test positive for the virus have a higher risk of developing PML.


"This label change marks an important advance in assisting people with MS and their physicians to make better-informed decisions concerning the challenges of balancing effectiveness with safety," said Dr. Nicholas LaRocca, vice president of the National MS Society.


Tysabri was temporarily pulled from the market shortly after its launch in 2005 after three patients taking the drug developed PML. FDA allowed the drug back on the market the following year but under a restricted distribution program. Only doctors and pharmacies registered with the company's distribution program are permitted to prescribe and dispense the drug.

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