Biogen Idec’s fourth-quarter financials have revealed a slow-down in sales of the multiple sclerosis treatment Tysabri and another case of progressive multifocal leukoencephalopathy, the rare brain disease.

Net income was up 11% to $206.7 million, up 3%, while group revenues climbed 20% to $1.1 billion. These were driven once again by Avonex (interferon beta-1a) and sales of the firm’s older MS drug climbed 13% to $566 million, helped by increased demand at home and abroad.

The rheumatoid arthritis and cancer drug Rituxan (rituximab) also did well, and revenues, which come from Biogen's joint venture with Genentech, rose 20% to $303 million. As for Tysabri (natalizumab), which is partnered with Elan, sales in the quarter were up 73% to $155.6 million.

However analysts were disappointed as the figure was down from the $171 million Biogen earned from the drug in the third quarter. At the end of the year, 37,600 people were on commercial and clinical Tysabri therapy worldwide, the firm noted, adding that “the safety data continues to support a favourable benefit-risk profile” for the drug.

Nevertheless, the latest case of PML, contracted by a patient in Europe, is the fifth to be reported since July, and this is affecting sentiment towards Biogen’s stock. The shares fell 1.5% on the news and chief executive James Mullen acknowledged that it would be “difficult” for Biogen and Elan to achieve their forecast of 100,000 patients on Tysabri by the end of 2010.

Still Mr Mullen was upbeat, insisting that “Tysabri is well on its way to becoming a blockbuster”. He added that “we've transformed the pipeline over the past two years, with 22 programmes in Phase II trials and beyond this year."

Icahn pushes to get four board members
Meantime it looks as though the billionaire Carl Icahn is looking once again to increase his influence in the way Biogen is run. The company noted that Icahn Partners, which has a 6% stake in the firm, has nominated four individuals for election to the board of directors at the company's 2009 annual meeting and is asking for the size of the board to be fixed at its current number of 13 members.

Biogen said it “will review the notice and consider it in light of the best interests of all shareholders of the company”. Last June, Mr Icahn failed in an attempt to get three people onto the board, having earlier criticised the firm for not looking hard enough to find a buyer and then taking down the ‘for sale’ sign at the end of 2007 when no definitive bids came in.