Biogen Idec has reported a dramatic surge in net income to in the third quarter to $157 million compared to $27 million same time last year, although the result was flattered by charges related to the merger of Biogen with Idec in 2005.

Revenues were up 18% to $703 million driven primarily by multiple sclerosis drug Avonex (interferon beta-1a) and cancer drug Rituxan (rituximab).

Avonex posted a 16% increase in sales to $445 million in the quarter, shrugging off the impact of increased competition in the MS market, while Rituxan revenues from Biogen Idec’s joint venture Genentech rose 12% to $204 million.

The company also recorded the first sales of new MS drug Tysabri (natalizumab) since its return to market after being pulled off on safety concerns last year, with $5 million in direct sales and a further $14 million from supplies to Elan, its development partner for the drug.

Sales of Tysabri were suspended after the drug was linked to a rare but potentially fatal brain disease. About three-quarters of the patients taking Tysabri were previously taking other MS treatments, including Avonex, Biogen Idec said.

The company raised its full-year 2006 earnings forecast to $2.20 a share or more, having previously forecast earnings in the $1.95-$2.10 range.

Biogen Idec’s chief executive, Jim Mullen, said the business was also more profitable than expected because it had not spent as much as it expected on licensing new drugs and other forms of business development aimed at reducing its reliance on its main product lines.

It had set aside $200 million for that purpose in the quarter, but ended up spending less than half that because competition to acquire late-stage products is intense.