New York  - The board of biotech firm ImClone Systems Inc on Monday rejected as too low a 4.3-billion-dollar take-over offer from pharmaceutical giant Bristol-Myers Squibb.

The board of director's said in a statement that the offer undervalues experimental cancer drugs that ImClone is in the process of developing.

Activist investor Carl Icahn, who chairs ImClone's board, said he was opposed to the offer.

Bristol-Myers, which already own 17 per cent of ImClone's shares, last week offered 60 dollars per share share to take over ImClone. If it were to acquire ImClone, Bristol-Myers would gain total control of cancer drug Erbitux. Profits from the drug are now split between the companies.

ImClone has also discussed spinning off its development unit. (dpa)