Biogen Idec has posted a strong set of financials for the second quarter which saw sales of the multiple sclerosis treatment Tysabri soar.

Net income was up 11% to $201 million, or $0.67 per share (+30%), while revenues climbed 28% to $993 million, driven once again by Avonex (interferon beta-1a). Sales of the old MS drug climbed 14% to $527 million, helped by increased international demand.

The rheumatoid arthritis and cancer drug Rituxan (rituximab) also did well, and revenues, which come from Biogen's joint venture with Genentech, rose 21% to $279 million. However it was the performance of the new MS drug Tysabri (natalizumab), which is partnered with Elan, that got analysts talking.

Global Tysabri sales in the quarter almost tripled to $200 million, comfortably exceeding most analyst forecasts, and Biogen's share was $147 million, up 210% from the like, year-earlier period. By the end of the quarter, over 31,800 people were on commercial and clinical Tysabri therapy worldwide, the firm noted, adding that there have been no confirmed cases of progressive multifocal leukoencephalopathy since the drug was relaunched two years ago.

Chief executive James Mullen noted that the firm’s core products “continue to grow, our pipeline is overflowing and our revenues have grown more than 25% year-over-year for three consecutive quarters”. Given the “strong momentum underway”, he said that Biogen is raising its full-year guidance “and setting an aspirational goal of generating a record $4 billion in revenues this year."

Biogen said it now expects full-year earnings above $3.50 per share, excluding items, up from its prior forecast of $3.25-$3.45, which represents an increase consistent with its aim of 20% EPS annual growth through 2010.

Analysts were impressed and JPMorgan analyst Geoffrey Meacham at JPMorgan said in a research note that "Tysabri sales were significantly above expectations, beating our above-consensus estimate of $190 million". He added that "the long-term Tysabri outlook continues to improve”.

Investors were equally pleased with the performance and Biogen shares ended the day up 6.6% to $71.28.