The European Medicines Agency is insisting on an update to the label on Biogen Idec and Elan Corp's multiple sclerosis drug Tysabri highlighting the risk of a rare brain infection.

The EMEA's Committee for Medicinal Products for Human Use has recommended that the product information for Tysabri (natalizumab) be updated "to further increase awareness about the risk of progressive multifocal leukoencephalopathy" in patients with relapsing-remitting MS who have been treated with the drug. The CHMP's recommendation follows the reporting in July of two new cases of PML in patients who had been treated for MS with Tysabri alone for more than 12 months.

However, the Committee concluded that the benefits of Tysabri continue to outweigh its risks in the treatment of relapsing-remitting MS, but that the existing warning on the risk of PML "should be strengthened to heighten patients' and prescribers' awareness about this rare but serious side effect".

Tysabri has been under intense scrutiny since it was reintroduced in the USA and approved in Europe two years ago. It was originally withdrawn from the market in 2005 after three patients developed PML, but following its reintroduction has gone on to be a big earner – pulling in some $200 million in the second quarter of this year alone.

Biogen upgraded
Meantime, Biogen has been boosted by an upgrade from analysts at Lazard Capital Markets. The stock has gone up from 'hold' to 'buy' with Lazard's Joel Sendek saying that Tysabri sales will likely continue rising, as will the firm's other MS drug Avonex (interferon beta-1a).

The stock's current value is a good entry point for investors, he adds.