Onyx Pharmaceuticals has rejected a takeover bid by biotechnology company Amgen.
Onyx (, which develops cancer drugs and treatments, said Monday that Amgen's takeover bid of $120 a share undervalued the company. Onyx stock closed Friday at $86.82. )
"We are actively exploring the potential to combine Onyx with another company as an option to create additional value for Onyx shareholders," said Onyx CEO N. Anthony Coles.
Shares of Onyx rose more than 6% last week on news of Amgen's offer. Overall, the stock has increased nearly 36% since last year.