Biogen Idec has headed off another potential proxy battle with Carl Icahn after accepting one of the billionaire’s nominees onto the board in return for his support for the company’s own slate of candidates.

At the beginning of last month, Icahn Partners announced its intention to nominate three people to Biogen’s board of directors at the 2010 annual meeting in June. In 2008, he had launched a similar unsuccessful bid, a year after he criticised the US biotech major’s bosses for not looking hard enough to find a buyer.

However an agreement has now been reached whereby one of Mr Icahn’s proposed nominees, Eric Rowinsky, has been accepted by Biogen. Along with Alexander Denner and Richard Mulligan, who were added to Biogen’s board after a proxy contest last year, Dr Rowinsky was a top executive at ImClone Systems which was sold to Eli Lilly in 2008 after the Icahn team took control two years earlier.

As part of the deal in getting another man on the board, Icahn Partners has agreed to vote its shares for Biogen's nominees at the AGM. The company has temporarily increased the number of seats on its board to 13 from 12 until that meeting where chief executive James Mullen and former chairman Bruce Ross will step down.

William Young, Biogen’s chairman, said that Dr Rowinsky and another nominee, Stephen Sherwin (chairman of the Biotechnology Industry Organization), will both bring “relevant skills and significant industry experience to the board”. Mr Icahn added that “I am pleased we were able to reach an agreement that is in stockholders' best interests”, saying that “the nominees who will replace Messrs Mullen and Ross are extremely qualified and I believe will add great value to Biogen”.

With Mr Mullen’s imminent departure and three seats secured on the board, despite having just a 6% stake in the firm, it looks as though Mr Icahn’s previously-stated desire to split Biogen into two, with one firm focusing on neurology and the other on cancer and autoimmune diseases, could be given more credence. A sale after such a split to big pharma would not be a surprising step.