Billionaire investor Carl Icahn wants the board of Biogen Idec Inc to consider splitting the biotechnology company into one firm focused on neurology and another focused on cancer.

Icahn, who has launched his second proxy battle for board representation at Biogen, offered the proposal in a filing with the U.S. Securities and Exchange Commission. Biogen will hold its annual shareholder meeting on June 3.

Separating Biogen assets will enhance shareholder value as management focus should improve and disparate assets appeal to different buyers, according to the slide presentation filed with the SEC.

A neurology-focused company, according to Icahn, would have had $2.93 billion in sales last year, including Biogen's multiple sclerosis drugs Avonex and Tysabri. A cancer-focused company would have had $1.17 billion in sales, and included Rituxan and Fumaderm.

Icahn also wants Biogen to examine its cost structure and improve its relationships with its partners.

Biogen is still going through Icahn's filing after receiving it last night, spokeswoman Naomi Aoki said, adding that the company is always open to input from major shareholders.

That said, this seems like an 11th-hour tactic by Mr. Icahn to win votes, Aoki said. He has had plenty of opportunity over the course of the past year to make suggestions or engage in discussions about his ideas for the business, and he has not done so until basically right in advance of the shareholder meeting.

Last year, Icahn lost a proxy fight against Biogen. He had accused the Cambridge, Massachusetts-based biotech of sabotaging its own announced attempt to find a buyer.

An associate of Icahn's said at an industry conference last month that the investor was not seeking to sell the company this time, but to fix it.

Biogen shares fell to $49.11 in trading before the market opened from Monday's close of $49.14.

(Reporting by Lewis Krauskopf; Editing by Derek Caney and Lisa Von Ahn)