Biogen Idec ( BIIB - Analyst Report ) and Elan Corporation, plc ( ELN - Snapshot Report ) recently announced the publishing of research from the Tysabri risk management program in the New England Journal of Medicine.

The research was based on data from Tysabri trials, post-marketing studies and an independent Swedish registry to estimate the incidence of progressive multifocal leukoencephalopathy (PML) in patients on Tysabri.

Three risk factors, the presence of anti-JC virus antibody, prior treatment with immunosuppressants and treatment duration with Tysabri, were used in the analysis.

Patients with anti-JC virus antibody, who had taken immunosuppressant therapy before Tysabri and had been on Tysabri for 25 to 48 months, demonstrated the highest risk of PML. The number of PML cases in these patients was 11.1 per 1,000 patients.

On January 20, 2012, Biogen and Elan announced that the U.S. Food and Drug Administration (FDA) approved a label change for Tysabri. As per the updated label, anti-JC virus antibody status is a risk factor for developing PML, a rare and life-threatening brain infection. This step will enable doctors to assess the patients’ risk benefit matrix better.

Tysabri is approved in the U.S. for relapsing forms of multiple sclerosis (MS) in patients who show inadequate response to or are unable to tolerate other treatments. In the E.U., Tysabri is approved for highly active relapsing-remitting MS (RRMS) in adult patients who have severe RRMS or have failed with beta interferon treatment.

In the E.U., Tysabri was approved in 2006, while in the U.S.; it was initially approved in 2004. The product was withdrawn from U.S. markets in 2005 due to the PML concern.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.

In-market net sales of Tysabri climbed 14.2% to $399 million in the first quarter of 2012. The increase was driven by higher global demand and higher price in the U.S. market. The sales of Tysabri recorded by Elan rose 17.5% to $288.2 million.

Our Recommendation

We currently have a Neutral recommendation on both Biogen and Elan. While Elan carries a Zacks #2 Rank (Buy rating) in the short run, Biogen carries a Zacks #3 Rank (short-term Hold rating).