NEW YORK (AP) -- Shares of Onyx Pharmaceuticals surged before Monday's opening bell on news that the company received an unsolicited takeover bid from Amgen Inc.
The drug developer confirmed Sunday that it received an offer of $120 per share, but said it rejected the bid because it "significantly undervalued" the company.
In premarket trading, Onyx shares jumped $47.18, or 54.3 percent, to $134 shortly before the opening.
Onyx also said Sunday that other companies have expressed interest in a buyout, and that its board authorized its financial adviser, Centerview Partners, to contact potential suitors.
Jefferies analyst Biren Amin backed his "Buy" rating and $104 price target for Onyx shares, saying that the company could receive several bids.
Onyx's tablet medication Nexavar, which treats liver and kidney cancer, is approved in more than 100 countries. It brought in $70.3 million in revenue in the first quarter, a slight drop from a year ago.
It also received approval last year from the FDA for an injection medication called Kyprolis, which is for treatment of multiple myeloma, a cancer of plasma cells which accumulate in bone marrow. In the first quarter, sales of the drug reached $64 million.
Stivarga, a pill to treat colorectal cancer developed by Onyx and Bayer HealthCare, also got the OK from the FDA last year. Onyx received royalty revenue of $9.2 million in the first quarter for Stivarga.