Biogen IDEC (Nasdaq: BIIB) took a big leap forward on Wednesday, announcing blowout first-quarter financial results.

The company enjoyed a healthy 19% jump in sales of lead multiple sclerosis (MS) drug Avonex, and a rapidly growing launch of MS and Crohn's-disease treatment Tysabri. Those rising sales helped Biogen post 32% higher first-quarter revenue and 23% higher income year over year.

Biogen also raised and refined its financial guidance for 2008. It expects revenue growth to top its previous 15% to 20% range, with non-GAAP earnings per share forecast in the $3.25 to $3.45 range. Both of these higher estimates should make it easier for Biogen to hit its previously stated long-term goal of 15% compound annual sales growth and 20% average non-GAAP EPS growth from 2007 through 2010.

Biogen predicts that Tysabri will be its biggest growth driver over the coming years. According to the company, the number of commercial Tysabri patients worldwide jumped a strong 25% between late December 2007 and the end of March. As Biogen stated in its conference call, that gives Tysabri a run rate of more than $600 million in annualized sales; partner Elan (NYSE: ELN) will share the profits from those sales.

While Biogen's valuation got a bit ahead of itself last year amid buoyant buyout talk, 2008 seems like smooth sailing for the company thus far. Its financials are hitting on all cylinders, and its most important drugs are producing strong clinical trial data and robust revenue. Investors could ask for little more from Biogen at this point -- except perhaps that the company refrain from making any crazy acquisitions.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has an A+ disclosure policy.