The company's shares fell more than 6 percent in midday trading.
Michael Chang was removed as chairman, while John Prunty, the company's chief financial officer, and Youe-Kong Shue, who served as a vice president, were both fired.
Chang remains a company director, but the board has asked him to resign, Optimer said.
The San Diego-based company's board subsequently named Hank McKinnell, who last month was appointed lead independent director, as its new chairman. The company also said that Kurt Hartman, its general counsel, chief compliance officer and senior vice president, would serve as acting CFO.
The company said that the moves aren't expected to materially affect its revenue or operations. But it also said Monday that it expects to post first-quarter revenue of about $16.5 million, well below average Wall Street predictions of $29.4 million, according to a FactSet poll.
The company said it removed Chang as chairman because of his actions as a member of the board of Taiwan-based Optimer Biotechnology, in which Optimer holds a 43 percent stake, along with his failure to manage compliance and conflict of interest issues after Optimer Biotechnology granted him 1.5 million of its shares.
Optimer said the board fired Prunty and Shue because they failed to follow proper procedures when they found out about the issues related to the shares. The company said the board also plans to remove Chang from Optimer Biotechnology's board and replace him with. McKinnell.
A call to the company seeking comment from the three executives who have been dismissed was not immediately returned.
The company said that it has informed the appropriate federal authorities and is cooperating with them in their reviews.
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