The battle for control of Amylin Pharmaceuticals has heated up again after one of the firm’s major shareholders issued a vote of no confidence in the board.

Eastbourne Capital, which holds a 12.5% stake in Amylin, had previously kept out of the ring in the last week or so as another large stockholder, the billionaire investor Carl Icahn, and the board have traded strongly-worded letters about the future direction of the company. In a proxy battle, the investment group has proposed five candidates to fill 12 of the Amylin board places, while the company is looking to get 10 of its existing directors reappointed.

Mr Icahn, who has a 9% stake, had also originally proposed five candidates but now is asking shareholders to pick three of them, plus the five proposed by Eastbourne and four from Amylin. However those four do not include the company’s chairman Joseph Cook or James Wilson, the lead independent board member who has been involved in the angry exchanges with Mr Icahn.

Now Rick Barry, Eastbourne’s founder, has said that the board is “mischaracterising our reasons for pursuing significant change to Amylin’s leadership and we urge shareholders not to be distracted” He added that “the massive loss of shareholder value” suffered recently “stems from the company’s failure to maximise the commercial value of Amylin’s assets”.

Mr Barry went on to say that the possible launch of the once-weekly version of the company’s diabetes blockbuster Byetta (exenatide), partnered with Eli Lilly, “is Amylin’s best chance for commercial success”. He added that “we have no confidence that the current board…can provide the leadership to successfully deliver on the company’s commercial capabilities at this critical juncture”.

The board is not going down without a fight, however, and its latest letter to shareholders claims that the dissident shareholders are damaging the company. It says that “over the course of our conversations with Mr Icahn and Eastbourne, it has become abundantly clear that their goal is the sale of Amylin. We strongly believe that this agenda is not in the best interests” of shareholders.

Amylin went on to say that “consistent with his history in several recent and current proxy fights, Mr Icahn wants to employ a ‘cookie-cutter' approach to slashing costs, without any regard to the specific nature of Amylin's business”. It adds that “his one-size-fits-all methodology is exemplified by his identifying insurance and logistics as potential areas for additional savings, neither of which are significant components of Amylin's cost structure. His actions would undermine our efforts to prepare for and launch exenatide once-weekly”.

The board concludes by saying that Mr Icahn and Eastbourne “show a serious lack of understanding of Amylin's business and the value-enhancing opportunities that the company has created in the marketplace”. Observers are eagerly waiting to see how the dispute pans out at the company's annual shareholders' meeting on May 27, if not before.