Bristol-Myers Squibb Co. (BMY) said Tuesday that Chief Executive Peter Dolan will step down immediately, and that his post will be filled on an interim basis by board member James Cornelius, a former chairman of medical device maker Guidant.

The company said the changes followed a Monday board meeting at which a special government monitor recommended the company dismiss Dolan and General Counsel Richard Willard. Willard is also leaving, effective immediately.

Dolan's departure came after a series of missteps during his five-year tenure led to the company's stock losing more than one-half its value. Dolan has agreed to stay as an adviser to help find a new CEO, the company said.

While Dolan was CEO, the company endured an accounting scandal, was criticized for overpaying in a deal with biotech company ImClone Systems Inc. and was hit with earlier-than-expected competition for its top-selling Plavix drug.