Biogen Idec has posted its third-quarter results which reveal a decline in profits but strong sales of the multiple sclerosis treatments Tysabri and Avonex.

Net income came in at $254.1 million, a fall of 8.5%, as a result of an $85 million charge linked to licensing Knopp Neurosciences' experimental treatment for amyotrophic lateral sclerosis, dexpramipexole. Revenues were up 4.9% to $1.18 billion.

Sales were again driven by Tysabri (natalizumab), partnered with Ireland’s Elan Corp, which brought in $220.7 million, up 6.6%. Biogen noted that by the end of the quarter, around 55,100 people were on commercial and clinical Tysabri therapy worldwide.

There have been high-profile cases of Tysabri patients developing progressive multifocal leukoencephalopathy, a rare brain infection, but Biogen and Elan recently presented data which they believe "further supported the potential clinical utility of an investigational assay that detects anti-JC virus antibodies" that would assess MS patients' risk for developing PML. The companies say they have completed preliminary discussions with regulators in the USA and Europe about these data and plan to submit labellling changes to both agencies by the first quarter of 2011.

As for the company’s older MS drug Avonex (interferon beta-1a), sales climbed 11.0% to $643.6 million. The rheumatoid arthritis and cancer drug Rituxan (rituximab), partnered with Roche, brought in $258 million, down 9%.