Carl Icahn, billionaire investor in MediImmune, has revealed how he threatened to nominate a slate of opposing directors to the biotechnology company’s board unless the firm sought a buyer.

In an emailed statement, Icahn explained that he urged MedImmune “four or five weeks ago” to put the company up for sale or he would nominate directors at the 2007 annual meeting “whose intention it would be to accomplish this.” He also said he “reserves the right to launch a proxy contest in the event that Medimmune does not successfully complete the sale transacton.”

In an interview Icahn went on to say that shareholder value would be considerably enhanced if the company was sold, because of the “very lacklustre management that has pervaded the company for the last five years,” a comment thought to be directed at David M Mott, MedImmune's chief executive since 2000.

The financier’s statements shed some light on why the board authorised its management to explore a sale last week after dismissing the idea on at least two previous occasions.

Obsessive corporate raider

Icahn has a reputation as an obsessive corporate raider. In 2004, he applied his customary pressure to Mylan Laboratories, after the company announced a deal to acquire King Pharmaceuticals, by threatening a proxy fight, claiming the contract required Mylan to over-pay, that chief executive Robert J Coury was significantly over-compensated, and that Mylan’s corporate governance was otherwise badly flawed. Mylan gave up its efforts to acquire King, but management said this was a result of its ongoing monitoring of relevant facts, not because of pressure from Icahn. Similarly, in 2005, Icahn wrote a letter to the biotechnology company ImClone saying that if the chairman didn’t resign “you will have thrown down the gauntlet.” A month later Icahn was made chairman of the board.

But MedImmune has been under pressure to sell for some time. David A Katz, president of the smaller investor Matrix Asset Advisors, wrote to the board several times urging a sale before publicly pressuring for the company to seek a buyer in December. A proxy fight against MedImmune could have led to its directors and management being removed unceremoniously, Katz later explained in an interview, but selling gives the board “the opportunity to create more value and leave as heroes with a lot of money in their pockets.” Should the company be sold Mott stands to make $100 million on share and stock options.

Several major pharmaceutical companies are said to have expressed an interest in MedImmune, which has an impressive portfolio that includes the blockbuster paediatric drug Synagis (palivizumab) the nasal flu vaccine FluMist, royalties from human papillomavirus vaccine technology and a promising pipeline.

MedImmune shares rose $1.25 following Icahn’s disclosure, closing at $45.44. This follows a jump of $5.79 to $43.63 last week on news of a possible sale.