Proxy materials have been delivered to Biogen Idec Inc by Carl Icahn, as the billionaire investor seeks greater control of the biotechnology company's board, according to a source familiar with the situation.

Last June, Icahn succeeded in placing two representatives on Biogen's board following a bitter and colorful proxy battle. A new proxy fight would represent Icahn's third assault on Biogen in as many years.

The proxy material delivered to Biogen on Wednesday contain a call for three new Icahn representatives to be nominated to the 12-member board, according to the source, who is not authorized to speak publicly about the matter.

Icahn could not immediately be reached for comment. A spokeswoman for Biogen Idec was also not immediately available.

In the seven months since Icahn's representatives took their seats at Biogen, the company's chairman has been replaced, and its chief executive, James Mullen, has announced he will retire.

But Icahn needs more influence over the board to effect the sweeping corporate changes he is known for. Biogen, which makes the multiple sclerosis drugs Avonex and Tysabri, has failed to excite investors with its performance or its pipeline of experimental new drugs.

The Cambridge, Massachusetts-based company continues to wrestle with safety concerns over Tysabri, which has been associated with a potentially deadly brain infection known as progressive multifocal leukoencephalopathy, or PML.

And there is concern increasing competition may hurt sales of its flagship multiple sclerosis drug Avonex.

Its shares, which closed up 1 percent at $53.58 on Wednesday, are trading in roughly the same range that they were in early 2004.

Four Biogen board seats are up for election this year -- those being vacated by James Mullen and former chairman Bruce Ross; as well as Brian Posner, previously CEO of ClearBridge Advisors LLC, and Nancy Leaming, the retired CEO of Tufts Health Plan.

The three seats targeted by Icahn are held by Ross, Mullen and Posner, according to the source.

(Reporting by Toni Clarke; Editing by Bernard Orr)