Prosecutors said Robert Ramnarine, 45, made about $311,361 in illegal profit between August 2010 and July 2012 by buying call options in ZymoGenetics Inc and Pharmasset Inc and call and put options in Amylin Pharmaceuticals Inc, shortly before those pharmaceutical companies agreed to takeovers.

Ramnarine, who was promoted in July to assistant treasurer for capital markets, was charged with three counts of securities fraud, according to a complaint made public on Thursday in the federal court in Newark, New Jersey.

The East Brunswick, New Jersey, resident was arrested Thursday morning and is expected to appear in federal court later in the day, said a spokesman for federal prosecutor Paul Fishman. It is unclear whether Ramnarine has hired a lawyer for his defense.

Ken Dominski, a Bristol-Myers spokesman, said the New York-based company is cooperating with the government and has put Ramnarine on administrative leave. "Bristol-Myers Squibb has clear and strict policies prohibiting trading on material non-public information," he said.

According to the complaint, Ramnarine learned confidential information about potential takeovers while working as a director or executive director in Bristol-Myers' pension and savings investments office in Princeton, New Jersey.

The complaint said that before buying the Pharmasset options, Ramnarine conducted several Internet searches from his office concerning detection of insider trading, including "can stock option be traced to purchase inside trading" and "insider trading options traceillegal (sic)."

Bristol-Myers bought ZymoGenetics for $885 million in October 2010. It expects to complete its $5.3 billion purchase of Amylin this month.

Gilead Sciences Inc agreed in November to buy Pharmasset after Bristol-Myers dropped out of talks. Gilead completed the $11 billion acquisition in January.

The case is U.S. v. Ramnarine, U.S. District Court, District of New Jersey, No. 12-md-08121.

(Reporting By Jonathan Stempel and Ransdell Pierson in New York; Editing by Gerald E. McCormick, Lisa Von Ahn and John Wallace)

By Jonathan Stempel and Ransdell Pierson