FDA Approves First Test Assessing PML Risk With Natalizumab

Allison Shelley


January 20, 2012

January 20, 2012 — The US Food and Drug Administration (FDA) today approved the first blood test assessing risk for progressive multifocal leukoencephalopathy (PML) in patients taking natalizumab (Tysabri, Biogen Idec/Elan Pharmaceuticals).

This test will give physicians an additional means to determine whether patients with multiple sclerosis or Crohn's disease undergoing immunomodulatory therapy are at increased risk for developing the often fatal infection, Alberto Gutierrez, PhD, director of the FDA's Office of In Vitro Diagnostics said in a news release.

The Stratify JCV test was developed in collaboration with Biogen and Elan Corporation and will be marketed by Quest Diagnostics. It is designed to help stratify risk for PML in patients treated with natalizumab. However, the FDA stipulates it should not be used on its own for diagnosis.

In a separate action, the FDA also announced updates to the drug label for natalizumab. The change includes information that testing positive for anti-JC virus antibodies is a recently identified risk factor for infection.

The assay is intended for use in conjunction with other clinical data, including duration of treatment with natalizumab or other immunosuppressants. Patients, for example, who have all 3 risk factors — anti-JCV antibodies reflecting prior exposure to JCV; natalizumab treatment for longer than 2 years; and treatment with immunosuppressants, such as mitoxantrone, azathioprine, or cyclophosphamide before receiving natalizumab — have an estimated risk of about 11 per 1000 patients treated, the FDA statement notes.

However, the FDA safety announcement emphasizes that patients who test negative for anti-JCV antibodies are still at risk for the development of PML because of the potential for new JCV infection or a false-negative test result.

The new test has not been approved for use in neonates, pediatric patients, or any other immunocompromised patient populations.

The FDA reviewed data for the new blood test through the de novo reclassification process, a regulatory path for low- to moderate-risk medical devices that are novel and not similar to an already legally marketed device, the statement adds.

A total of 201 cases of PML have been reported among approximately 96,582 patients treated with natalizumab worldwide through January 4, 2012.


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