Biogen Idec’s second-quarter financials have revealed a 30.9% decline in profits, but sales of the multiple sclerosis treatment Tysabri rose again.

Net income came in at $142.8 million, though the company noted that the figures include a payment of $110 million related to its recent licensing agreement with Acorda Therapeutics for the experimental MS drug Fampridine-SR (4-aminopyridine). Revenues climbed 10.1% to $1.01 billion.

The sales rises were driven by Tysabri (natalizumab) which brought in $187.6 million, up 27.5%. Global sales of the drug, which is partnered with Ireland’s Elan Corp, reached $254 million, and Biogen noted that by the end of the quarter, around 43,300 people were on commercial and clinical Tysabri therapy worldwide, up from 40,000 at the end of the first quarter.

As for Biogen’s older MS drug Avonex (interferon beta-1a), sales climbed 12.1% to $591.2 million, helped by a 20% increase in US revenues. The rheumatoid arthritis and cancer drug Rituxan (rituximab) also did well, and revenues, which come from Biogen's joint venture with Genentech, came in at $276 million.

Chief executive James Mullen said that during the second quarter “we drove a clear acceleration of Tysabri patient growth that puts the drug on a blockbuster run-rate”. Last month Biogen revealed there have now been 10 cases of the potentially fatal brain infection progressive multifocal leukoencephalopathy linked to natalizumab and analyst Eric Schmidt of Cowen & Co said the new PML cases has dampened enthusiasm for the company’s shares.

However, he added in a research note that “it is clear that Tysabri’s growth continues despite all the negative attention the drug receives on Wall Street”.