New York

FOR almost four years, Bristol-Myers Squibb Co investors have profited handsomely thanks to the company's sharp focus on cancer. On Friday, they felt the other side of that concentrated bet.

The drop in the shares on Friday - the worst in more than 16 years - had as much to do with the failure of Bristol-Myers's drug Opdivo in a clinical trial for lung cancer as it did with investors' now-shaken confidence in the New York-based company's ability to be the breakaway leader in the field. It's also a stark reminder of the risks of drug development.