By Soyoung Kim
(Reuters) - Amgen Inc <AMGN.O> is close to buying Onyx Pharmaceuticals Inc <ONXX.O> for $125 per share, or more than $10 billion, in a deal that is expected to be announced as soon as Monday, two people familiar with the matter said on Saturday.
A deal, which is still being finalized and would require board approval from both companies, would represent the fifth-largest biotechnology deal in history.
The proposed takeover would value Onyx at 13 times the company's expected revenues for next year, one of the richest valuations in biotech takeovers, one of the people said.
The people asked not to be identified because the matter is not public. Representatives for Amgen and Onyx could not be immediately reached for comment.
The acquisition of Onyx would give Amgen full rights to Kyprolis, the new multiple myeloma drug that analysts expect to reach annual peak sales in excess of $2 billion.
Amgen would also gain a revenue stream from the liver and kidney cancer drug Nexavar that Onyx shares with Bayer AG, as well as royalty payments on Bayer's much newer colon cancer drug Stivarga and potential future royalties on an experimental breast cancer drug being developed by Pfizer.
A deal in the $10 billion range would be Amgen's biggest since its $16 billion acquisition of Immunex in 2001 that gave it the rheumatoid arthritis drug, Enbrel, which is one of Amgen's most important, biggest selling products.
It would be by far the biggest deal under CEO Bob Bradway, who took over the top spot in May of 2012. He has done a handful of much smaller deals, the biggest to date being a $1.16 billion acquisition of Micromet.
(Reporting by Soyoung Kim in New York; editing by Gunna Dickson)