Billionaire investor Carl Icahn is suing Amylin Pharmaceuticals Inc., saying he and other shareholders should get more time to nominate candidates to the diabetes drug maker’s board of directors.

Icahn says Amylin is “at a crossroads” and stockholders deserve a chance to nominate new directors. The activist investors says he wants to nominate directors who will listen to offers for the company and accused the current board of diluting the value of Amylin shares.

Last week, Bloomberg News reported that Bristol-Myers Squibb Co. offered to buy Amylin for $3.5 billion, or $22 per share. Neither company has commented on that report. Icahn said the company made a mistake by refusing to pursue a sale and asked Amylin for more time to nominate competing candidates to the board.