SOUTH SAN FRANCISCO, Calif. ( TheStreet) -- Every biotech CEO wants to say they bought an asset for X and sold it for 10X, yet few top executives manage to create value on this mammoth scale. Onyx Pharmaceuticals' ( ONXX) CEO Tony Coles just did it. The 10X is Amgen ( AMGN) paying $10 billion in cash ($125 per share) to acquire Onyx. The deal, much discussed and analyzed since June, was finally announced Sunday night. But Amgen wouldn't be buying Onyx if Coles hadn't committed $800 million of the company's cash to buy Proteolix, a privately held maker of blood cancer drugs, in October 2009. From the Proteolix deal, Onyx gained control of the multiple myeloma drug carfilzomib. The FDA approved carfilzomib last year and the drug, now sold under the brand name Kyprolis, is expected to generate peak sales of $2 billion. There are more than a few reasons why Amgen is buying Onyx but Kyprolis is at the top of the list. That makes Coles' $800 million decision to buy Proteolix a bit less than four years ago -- the X deal -- a very, smart one. This is a chart of Onyx's market value since buying Proteolix in October 2009: ONXX Market Cap data by YCharts What strikes me about this chart is that it illustrates the distrust and apprehension many investors had about Kyprolis, even after successful clinical trials. It really took until the positive FDA advisory panel meeting in June 2012 -- two and half years after the Proteolix deal was announced -- for Wall Street to give Coles and Onyx the credit they deserved. If anyone deserves an "I told you so" moment, it's Coles! Here's the same story, told in the relative stock prices of Onyx and the Nasdaq Biotechnology Index. Again, Onyx doesn't start to outperform its peers until Kyprolis' won a recommendation for approval from an FDA advisory panel in June 2012. ONXX data by YCharts I remember when Coles was appointed Onyx's CEO in February 2008, replacing Hollings Renton. His selection was not universally applauded. Prior to joining Onyx, Coles had successfully restructured NPS Pharmaceuticals ( NPSP) as CEO, but investors gave him and the company little credit for the effort.