Billionaire investor Carl Icahn - the thorn in the side of fellow US biotechnology firm Mylan's proposed tie-up with King Pharmaceuticals last year - is to join the board of ImClone Systems along with two of his associates.

The news follows another jittery period for the firm, which suffered on the stock markets recently after claiming it had taken itself off the wedding market and wanted to remain independent. Instead, it said it would find a new Chief Executive and invited Icahn - who owns around 10% of the company - to join its board. This agreement has now been hashed out, with the new board of ImClone comprising nine original members, Icahn and his two compatriots, Charles Woler and Richard Mulligan. Woler is Chief Executive of biopharmaceutical company Neuro3D, while Mulligan is Professor of genetics at Harvard Medical School.

A statement from the firm said it was pleased with the new additions - "we are confident that they will make valuable contributions to the board as it focuses on continuing to grow the company” - but alluded to a proxy contest to install new management that would otherwise have “been distracting” to the company.

Joe Fischer will continue to serve as Interim Chief Executive during the search period, but Icahn is known not to want him in the post long-term and has also called for the Chairman to go. ImClone added sagely: “We look forward to Mr Icahn's further input with regard to the company's governance and hope that it will be productive and given in a manner that maximises the value of the company for all shareholders.”

Icahn's presence over Mylan has not abated either. He originally stepped in as the firm was trying to buy King Pharmaceuticals with his own offer, but the firm is not keen and recently announced a $1.25 billion share buyback in the hope it will deter predators.