The FDA has just issued new information regarding the “last resort” drug Tysabri, that is marketed by Cambridge, Mass-based Biogen Idec and Elan Pharmaceuticals.
Tysabri is prescribed as a “last resort” drug because it is widely considered a dangerous prescription drug that carries a risk of numerous serious side effects. It is used in the treatment of Multiple Sclerosis (MS) and was also an off-label treatment of Crohn’s disease. It is often prescribed for “relapsing forms” of MS, according to the FDA.
The latest news regarding this medication is that the US Food and Drug Administration (FDA) has recently identified a new risk factor which could lead to the life-threatening brain infection known as progressive multifocal leukoencephalopathy (PML) associated with the use of the drug Tysabri. They have also approved the first test for gauging the risk of this rare brain infection.
The New Test
On Jan. 20, the FDA approved the anti-JC antibody test which helps identify a patient who has been exposed previously to the John Cunningham virus (JCV). This test named Stratify JCV Antibody ELISA can be used with other clinical information of patients to determine the risk of PML in the aforesaid group. The JCV virus itself is considered to be harmless. But, it may lead to PML in people with weak immune systems possibly due to diseases and Tysabri treatment, for which there is no known treatments or cures and typically results in death or severe disability.
If a patient tests positive during that procedure it is an indication they’ve been exposed to the virus.
Patients previously exposed to JCV puts them at risk of developing PML, especially while taking Tysabri. In its Drug Safety Communication issued recently, the FDA said there are now three known risk factors associated with PML, with JCV exposure being the latest. A patient exhibiting all three risk factors face a serious risk of developing PML, determining that risk to be 11 in 1,000 patients.
Prescribing physicians and patients are being advised to carefully consider the possible benefits of taking Tysabri.
The FDA admits there is “no certain way” to determine who will develop PML.
In addition to the presense of JCV, the FDA has identified two other risk factors which are known to increase the risk of PML: taking Tysabri for more than two years or taking other immunosuppressant drugs like mitoxantrone, azathioprine, methotrexate, cyclophosphamide and mycophenolate before taking Tysabri.
New Label Changes
At the same time the FDA announced that it is updating the safety labels of Tysabri.
The new label identifies anti-JCV antibody status as a risk factor for developing PML.
It also states that anti-JCV antibody negative status indicates that exposure to the JC virus has not been detected.
Patients who are anti-JCV antibody positive have a higher risk of developing PML.
Patients who are anti-JCV antibody positive, have received prior immunosuppressant (IS) therapy and received treatment with Tysabri for more than two years have the highest risk of developing PML.
The agency also said the JCV test should not be administered “alone” nor should it be used to test for PML.
Biogen CEO George Scangos said Tysabri has benefited thousands of patients worldwide who are living with multiple sclerosis, an often devastating disease affecting people in the prime of their lives.
“Biogen Idec and Elan’s use of novel research and scientific expertise has allowed us to gain a better understanding of the benefit-risk profile for Tysabri,” Scangos added.
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