Biogen's quarterly profit fell short of analysts' estimates on weak sales of its Avonex multiple sclerosis treatment, its biggest-selling product.

But the biotechnology company said the Avonex shortfall stemmed largely from temporary issues and it also issued an encouraging forecast for 2012.

Biogen shares have soared 80% in the past year, largely on hopes for its oral MS drug, known as BG-12, which some analysts believe could become the leading MS treatment if approved.

"I expect the Street for the most part to look past this (earnings) miss," Cowen & Co analyst Eric Schmidt said. "Biogen is definitely a high-expectation stock, and you never want to see a high-expectation stock put up anything but a real strong quarter. But despite this lackluster result they upped the guidance, so that's comforting."

Wall Street is also heavily focused on Biogen's experimental drugs for hemophilia and amyotrophic lateral sclerosis, or ALS, also known as Lou Gehrig's disease. Biogen expects late-stage data for those drugs in the second half of the year.

The company is increasing spending on sales and research and development to support these new medicines. Some analysts said spending was above their estimates, contributing to the quarterly earnings miss.

In an interview, Biogen Chief Financial Officer Paul Clancy said the company would likely seek out fewer acquisitions or collaboration deals in the short term to focus on bringing potential new products to market.

"Our first order of priority is execution of the existing really strong late-stage pipeline that we have," Clancy said.

Still, Clancy said the company remained active in seeking out potential "tuck-in" deals, especially in the company's core areas of neurology and immunology. Biogen hunts largely for products in early- and mid-stage development, as opposed to late-stage.

"In this industry, it's pretty hard to create shareholder value for the later-stage assets," Clancy said. "It's not impossible, but it's actually much harder because they get bid to a premium well past their value."

Avonex comes in shy

Net income rose to $302.7 million, or $1.25 per share, from $294.3 million, or $1.20 a share, a year ago.

Excluding one-time items, earnings were $1.40 per share, 8 cents below the average estimate of analysts, according to Thomson Reuters I/B/E/S.

Revenue rose 7% to $1.29 billion, some $200 million shy of analysts' estimates.

Avonex sales rose 3% to $662 million, about $38 million below Wall Street's consensus estimate.

"Avonex was probably the culprit," Schmidt said of the earnings miss.

Avonex sales were particularly weak in January. Biogen executives said wholesalers presumably stocked up on the drug at the end of 2011, but demand for the injected treatment remained solid.

MS is a chronic, often disabling disease that attacks the central nervous system and can lead to numbness, paralysis and loss of vision.

Sales of Biogen's other important marketed MS drug, Tysabri, were $399 million, up 14%. Biogen sells Tysabri in partnership with Irish drugmaker Elan.

BG-12 would be Biogen's first oral drug to treat MS. The company applied for approval for BG-12 earlier this year in the United States and Europe.

Biogen expects a standard-length U.S. review for BG-12, but would be prepared if the Food and Drug Administration decided the drug was worthy of a faster, priority review, Biogen Chief Executive George Scangos told analysts on a conference call.

Biogen said it now expects 2012 earnings, excluding items, "above" $6.15 per share, compared with a range of $6.10 to $6.20 previously. Analysts have been looking for $6.19.

It expects revenue growth in the mid-single digits, compared with low- to mid-single digits previously.