Bristol-Myers offers to buy ImClone

Bristol-Myers Squibb Co. on Thursday offered $4.5 billion in cash for biotechnology company ImClone Systems Inc., saying the two, which are cancer drug partners, were "a natural fit."

The proposal offers ImClone stockholders $60 a share, a 30% premium over the company's closing price of $46.44 on Wednesday. Bristol-Myers, the world's No. 14 drug maker by revenue, already owns about 17% of ImClone.

The two companies, both based in New York, have been partners since September 2001 in developing Erbitux, which is approved for treating advanced colorectal cancer and head and neck cancers.

ImClone said it was "currently studying the situation."

Shares of ImClone surged beyond Bristol's offering price and rose $17.49, or 37.7%, to $63.93. Bristol-Myers shares fell 39 cents to $21.12.