MS drug personalised with risk diagnostic

The FDA has approved a safety label change for Biogen and Elan’s multiple sclerosis drug Tysabri (natalizumab) after the company identified a diagnostic test that can help identify patients at risk of developing a serious brain infection, which has been associated with the drug.

The partnering of drugs and diagnostic tests is a growing trend in pharmaceutical development that has the potential to offer a more personalized approach to healthcare provisions. Such approaches can also make products more appealing to government-funded healthcare programmes by identifying patients who will or will not benefit from an expensive drug. Analysis from Bloomberg indicates that the Tysabri label change could raise sales of the drug to $1 billion in 2016.

According to a statement from Biogen and Elan, the label change will improve the risk-benefit assessment for patients with relapsing forms of multiple sclerosis. Patients using Tysabri can be at risk of the John Cunningham virus (JCV), which can cause a rare brain infection called progressive multifocal leukoencephalopathy (PML). The new label identifies JCV antibody status as a risk factor for developing PML.

The Stratify JCV Antibody ELISA test (Focus Diagnostics) can be used to qualitatively detect JCV antibodies. When used with other clinical data from the patient, the test can help healthcare providers determine the risk for developing PML. In a separate press release, the FDA has announced that it will permit marketing of the test.

George Scangos, CEO at Biogen Idec said, “Our development of the risk stratification algorithm and subsequent efforts to support the commercial availability of anti-JCV antibody testing reflect our commitment to providing patients and their physicians with additional guidance to help them make more personalized treatment decisions.”

The ability to quantify the level of JCV antibody completes a triangle of three known risk factors and should help physicians and patients better understand the balance risk-benefit balance. According to FDA, patients with the following combined three factors have the highest risk of developing PML (about 11/1000):

• presence of anti-JCV antibodies (evidence of JCV exposure)
• over two years of treatment with Tysabri
• treatment with medicines known to weaken the immune system (e.g. mitoxantrone, azathioprine, methotrexate, cyclophosphamide, and mycophenolate mofetil)

The US label update follows the European Commission approval of anti-JCV antibody status as an additional factor to aid in patient risk stratification in June 2011. Globally, by the end of September 2011, there had been approximately 59,000 anti-JCV antibody tests administered commercially and through clinical trials.