The prospect of a bidding war for Onyx Pharmaceuticals Inc. in South San Francisco is sending biotechnology shares sharply higher, helping propel an advance in the broader stock market.
Onyx, a developer of anti-cancer drugs, said Sunday it had rejected a “significantly undervalued” takeover bid of $120 a share from Amgen Inc., the Thousand Oaks biotech giant.
But it added that it was “actively exploring” the possibility of selling itself to another bidder. That was all investors needed to hear, sending Onyx shares soaring by $43.74, a gain of more than 50%, in midday trading Monday.
The biotech segment of the market jumped more than 3%, Zachs analysts said, compared to a gain of about 1% for the Nasdaq exchange, where Onyx is traded.