(RxWiki News) Tysabri, one of the few drugs approved to treat multiple sclerosis, is getting a label makeover courtesy of the FDA. The new look shows off a newly approved safety test for patients.
The U.S. Food and Drug Administration has approved a safety test to identify patients who may be at risk of developing a severe brain disease as a result of using Tysabri. Tysabri's prescription label is being updated to inform the patients that the test is available, and which factors may put them at risk.
"Your doctor may recommend a blood test before prescribing Tysabri."
The label change is intended to help patients and their doctors evaluate the benefits and risks of taking the drug. Tysabri is known to increase the risk of progressive multifocal leukoencephalopathy (PML) when one or more of three known risk factors are present.
According to the FDA, the risk factors are:
- The presence of anti-JCV antibodies.
- Longer duration of Tysabri treatment, especially beyond 2 years.
- Prior treatment with an immunosuppressant medication (e.g., mitoxantrone, azathioprine, methotrexate, cyclophosphamide, or mycophenolate mofetil).
JCV stands for John Cunningham virus, which causes PML. Finding JCV antibodies in a patient means that he or she has been exposed to this relatively common virus, which lies dormant until activated by an immune-suppressing drug such as Tysabri.
PML causes death or severe disability, and currently, there is no treatment or cure for the infection.
In studies of PML in MS patients, all of the patients who had lab tests available previous to taking Tysabri had JCV antibodies present in their blood.
The test approved by the FDA is Stratify JCV, a blood-based test developed by Quest Diagnostics.
Patients who have tested positive for JCV antibodies but do not have the other two risk factors have a risk of PML of less than 1/1000, but those with all three risk factors have a 11/1000 chance of developing the brain infection.
Even patients who test negative for JCV may still be at risk, either by a false negative result or future exposure to the virus. The FDA advises that physicians consider periodically re-testing patients.
As of early January 2012, 201 cases of PML have been reported by over 96,000 patients who have taken the drug.