Biogen Idec has posted its second-quarter results which reveal a 2% slip in profits but continuing strong sales of its multiple sclerosis blockbuster Tysabri.

Net income came in at $288.0 million, while revenues were flat at $1.21 billion. Sales were again driven by Tysabri (natalizumab), partnered with Ireland’s Elan Corp, which brought in $281.4 million to Biogen's coffers, up 28%.

The company noted that by the end of the quarter, around 61,500 people were on commercial and clinical Tysabri therapy worldwide. Also last month, the European Commission approved the inclusion of 'anti-JC virus antibody status' as an additional risk factor on the label of the drug. The label change will provide an opportunity to identify patients at lower or higher risk for the development of progressive multifocal leukoencephalopathy, the rare but potentially fatal brain disease linked to Tysabri.

As for the company’s older MS drug Avonex (interferon beta-1a), sales climbed 5% to $659.2 million. The rheumatoid arthritis and cancer drug Rituxan (rituximab), partnered with Roche, brought in $216 million, down 29%, but Biogen noted that its share of Rituxan revenues was reduced by $50 million as a result of ongoing arbitration between the Swiss major and Hoechst.

Chief executive George Scangos said that “our commercial and financial performance has been strong, and we have made great progress on our pipeline". He noted that the latter is now focused on "high-quality projects in areas of our expertise – neurology, immunology, and haemophilia".