More Checks for Biogen's Tysabri - Analyst Blog

Last week, the European Medicines Agency (EMEA) finalized a review of Biogen Idec’s (BIIB) Tysabri (natalizumab) and the risk of progressive multifocal leukoencephalopathy (PML) associated with the prolonged use of the drug. PML is a rare brain infection caused by the JC virus.

The agency’s Committee for Medicinal Products for Human Use (CHMP) arrived at the conclusion that the risk of a patient developing PML increases after having taken the drug for two years or more, though the risk remains low. However, the benefits of the drug outweigh its risks.

Given the importance of the early detection of PML, the committee has recommended certain measures to ensure that patients and doctors are aware of the associated risks. Measures include updating product information to include the high risk of developing PML after two years of treatment and advice regarding management of patients showing symptoms of PML. In addition, the committee suggested that forms should be signed by patients at the beginning and after two years of treatment after having discussed the risks with their doctors.

The CHMP had to review the drug after 23 confirmed cases of PML were reported between July 2008 and October 2009, causing four deaths. Fourteen of these cases including one death were reported in the EU. Subsequently, the European Commission in October 2009 requested CHMP’s opinion for Tysabri.

As of January 20, 2010, the total number of PML cases has risen to 31, of which 23 were patients who had been receiving the drug for more than two years. This is equivalent to approximately one case of PML for every 1,000 patients treated with Tysabri for two years or more, consistent with the risk mentioned in the Tysabri’s label.

Tysabri, meant for the treatment of multiple sclerosis (MS) is jointly marketed with Elan Corp (ELN). The drug was withdrawn from the U.S. market in 2005 due to the PML concern, but was launched again after one year with a strict warning regarding the occurrence of PML.

Despite this, the drug continues its growth momentum. Tysabri sales came in at $207 million during the third quarter of 2009, up 21% from the prior-year period. The company estimates that as of the end of September 2009, about 46,200 patients were on commercial and clinical Tysabri therapy worldwide. This represents an increase from 43,300 patients reported by the company in the second quarter of 2009. We have a Neutral recommendation on Biogen.