Biogen/Elan Seek Label Update - Analyst Blog

Biogen Idec (BIIB) and partner Elan Corporation (ELN) recently announced their intention to seek approval for updating the label of their multiple sclerosis therapy, Tysabri. Biogen and Elan have submitted a supplemental Biologics License Application (sBLA) to the US Food and Drug Administration (FDA) seeking permission to include anti-JC Virus antibody status as one potential factor that could help stratify the risk of progressive multifocal leukoencephalopathy (PML) occurring in patients treated with Tysabri.

Biogen and Elan have also submitted a Type II Variation to the European Medicines Agency (EMA) regarding the label update.

Tysabri, which is available in more than 45 countries, is administered as a single intravenous infusion every four weeks. Tysabri was initially approved in 2004 but was withdrawn from US markets in 2005 due to the PML concern. The drug was reintroduced by Biogen and Elan after a year with a strict warning regarding the occurrence of PML. 

It has been observed that the overall worldwide cumulative rate of PML, a rare but serious brain infection, in patients who have received one or more infusions is 0.5 cases per 1,000 patients. This rate increases with the number of infusions received.

The prescribing information on Tysabri's label has been updated to include information regarding the increased risk of developing PML increases with longer use of the drug. The label also includes language regarding limited experience beyond 3 years of treatment.

Biogen has been conducting studies (STRATIFY 1 and STRATIFY 2) to confirm that patients who test negative on the JC virus assay could use Tysabri with lower concerns regarding the development of PML.

Despite carrying a black box warning for the risk of PML and other cautionary language, Tysabri sales crossed $1 billion in 2009. However, we remain concerned that an increase in the number of PML cases associated with the use of Tysabri could hamper new patient additions and lead to a slowdown in sales going forward.