Onyx Pharmaceuticals
Corporate brand
UnclaimedOnyx Pharmaceuticals was a South San Francisco oncology company that developed and commercialized cancer medicines before being acquired by Amgen in 2013.
Last updated August 26, 2026
Overview
Onyx Pharmaceuticals, Inc. was a biotechnology and pharmaceutical company focused on the discovery, development, and commercialization of medicines for cancer. The company was established in California in February 1992 by venture capitalist Kevin J. Kinsella and biochemist Frank McCormick, who had previously worked on cancer research at Chiron Corporation. Its formation was backed by Chiron, which initially held a substantial equity position, together with venture investors including Avalon Ventures, Institutional Venture Partners, J. H. Whitney & Company, and Kleiner Perkins. Samuel D. Colella, an Institutional Venture Partners partner, served as acting president during the company's initial period, while McCormick led research and served as chief scientific officer until 1996 and Kinsella chaired the board. Onyx reincorporated in Delaware in March 1996 and completed an initial public offering on the NASDAQ National Market in May of that year under the symbol ONXX. Its business model combined internal oncology research with alliances and commercial partnerships. The company's most significant commercial relationship was with Bayer, with which it co-developed or co-commercialized several targeted cancer therapies. This partnership helped establish Onyx as a specialist oncology company rather than a broad-based pharmaceutical conglomerate. The company's best-known medicines included sorafenib, marketed as Nexavar; carfilzomib, marketed as Kyprolis; and regorafenib, marketed as Stivarga. Nexavar was approved in the United States in 2005 for advanced renal cell carcinoma and in 2007 for inoperable hepatocellular carcinoma. Kyprolis received U.S. approval in 2012 for certain patients with relapsed or refractory multiple myeloma after multiple prior treatments. Stivarga, a Bayer-developed multikinase inhibitor, received U.S. approvals in 2012 for previously treated metastatic colorectal cancer and in 2013 for advanced or metastatic gastrointestinal stromal tumors. Under a 2011 arrangement, Onyx obtained a royalty on future global oncology sales of regorafenib and jointly promoted Stivarga with Bayer in the United States. Onyx expanded its pipeline and technology base in 2009 by acquiring Proteolix, a privately held biotechnology company, for $276 million in cash plus potential milestone payments. The transaction brought carfilzomib into Onyx's portfolio and strengthened its position in multiple myeloma. By 2012, industry observers identified Onyx as a potential acquisition target, although chief executive N. Anthony Coles publicly emphasized the company's intention to remain independent and advance new therapies. The company ultimately became the subject of a strategic acquisition process. Amgen made an unsolicited proposal in June 2013 to acquire Onyx for $120 per share. Onyx initially rejected the offer and authorized advisers to approach other potential buyers. After efforts to obtain a higher offer did not produce a completed transaction, the board accepted Amgen's original terms. The acquisition, valued at approximately $10.4 billion, was formally announced in August 2013. Onyx subsequently ceased to operate as an independent publicly traded company, and its oncology products and development programs became part of Amgen's portfolio. The corporate brand is therefore defunct as an independent company, although products associated with its development and commercialization continued under Amgen and its commercial partners.
History
Onyx Pharmaceuticals originated in the early 1990s as an oncology-focused biotechnology venture built around the scientific work of Frank McCormick and the financing and corporate leadership of Kevin J. Kinsella. McCormick had worked on cancer treatments at Chiron Corporation before becoming vice president of research at Onyx. Chiron provided important initial backing and held a 43 percent stake in the new company, while Avalon Ventures, Institutional Venture Partners, J. H. Whitney & Company, and Kleiner Perkins also invested. Samuel D. Colella, an Institutional Venture Partners partner, served as acting president at the company's inception. The company was founded and incorporated in California in February 1992. McCormick served as chief scientific officer through 1996, directing the research program, while Kinsella chaired the board. Onyx withdrew its California corporate registration on March 26, 1996, reincorporated in Delaware, and completed its public-market debut on May 9, 1996, on NASDAQ under the National Market symbol ONXX. Its strategy centered on cancer medicines developed through internal research and collaborations with larger pharmaceutical companies. A major part of Onyx's commercial development came through its relationship with Bayer. Sorafenib, marketed as Nexavar, was approved in the United States in 2005 for advanced renal cell carcinoma and in 2007 for inoperable hepatocellular carcinoma. Regorafenib, marketed as Stivarga, was developed by Bayer and later became part of an arrangement under which Onyx received a 20 percent royalty on future global net oncology sales and jointly promoted the product in the United States. Stivarga was approved in 2012 for previously treated metastatic colorectal cancer and in 2013 for certain advanced gastrointestinal stromal tumors. Onyx strengthened its position in hematologic oncology through its 2009 acquisition of Proteolix. The transaction was valued at $276 million in cash, with additional milestone payments. Proteolix's carfilzomib program became Kyprolis, which received FDA approval on June 20, 2012, for a defined population of patients with multiple myeloma who had undergone at least two previous therapies and whose disease had progressed on or soon after their most recent treatment. The product became a central part of Onyx's multiple-myeloma franchise. By 2012, market analysts and industry observers regarded Onyx as an attractive biotechnology acquisition candidate. N. Anthony Coles, then president and chief executive officer, stated that management preferred to operate independently and concentrate on bringing new therapies to patients. That position changed during 2013, when Amgen made an unsolicited offer of $120 per share. Onyx rejected the initial approach and empowered financial advisers to contact possible alternative acquirers. When those efforts did not result in a superior transaction, Onyx's board accepted Amgen's original proposal. The deal, announced in August 2013 and valued at approximately $10.4 billion, ended Onyx's existence as an independent public company. The company continued to be discussed in connection with its products and clinical programs after the acquisition announcement. In July 2014, it reported that a Phase III trial combining sorafenib with capecitabine in advanced breast cancer had failed to improve progression-free survival. The independent Onyx corporate brand is now defunct, while products and programs developed or commercialized through the company became associated with Amgen and Bayer.
- 2013
Stivarga approved for gastrointestinal stromal tumors
[1]Regorafenib received a second U.S. indication for certain patients with advanced or metastatic gastrointestinal stromal tumors.
- 2013
Amgen acquisition announced
[1]Onyx agreed to be acquired by Amgen in a transaction valued at approximately $10.4 billion.
- 2012
Kyprolis approved for multiple myeloma
[1]The FDA approved carfilzomib for certain heavily pretreated multiple-myeloma patients.
- 2012
Stivarga approved for metastatic colorectal cancer
[1]The FDA approved regorafenib for patients with previously treated metastatic colorectal cancer.
- 2009
Proteolix acquisition
[1]Onyx acquired Proteolix, adding the carfilzomib development program and expanding its multiple-myeloma capabilities.
- 2007
Nexavar approved for hepatocellular carcinoma
[1]Nexavar received a U.S. indication for inoperable hepatocellular carcinoma.
- 2005
Nexavar approved for advanced renal cell carcinoma
[1]Sorafenib, marketed as Nexavar, received U.S. approval for advanced kidney cancer.
- 1996
Delaware reincorporation and NASDAQ listing
[1]Onyx reincorporated in Delaware and went public on NASDAQ under the ticker ONXX.
- 1992
Company founded and incorporated in California
[1]Kevin J. Kinsella and Frank McCormick founded Onyx Pharmaceuticals with backing from Chiron and venture capital investors.
Products and positioning
A specialist oncology biotechnology company focused on targeted therapies, cancer biology, and commercial partnerships for medicines addressing difficult-to-treat solid tumors and blood cancers.
Targeted oncology medicine · 2005
Nexavar
Nexavar is the trade name for sorafenib, a multikinase inhibitor developed and commercialized by Onyx in collaboration with Bayer. In the United States it was approved in 2005 for advanced renal cell carcinoma and in 2007 for inoperable hepatocellular carcinoma. The medicine was also investigated in other cancers, including thyroid and breast cancer. A later Phase III study combining sorafenib with capecitabine in advanced breast cancer did not improve progression-free survival.
Multiple-myeloma medicine · 2012
Kyprolis
Kyprolis is the trade name for carfilzomib, a proteasome inhibitor brought into Onyx through its acquisition of Proteolix. The FDA approved it on June 20, 2012, for patients with multiple myeloma who had received at least two prior therapies, including bortezomib and an immunomodulatory treatment, and whose disease had progressed on or within 60 days of the latest therapy. Reported adverse reactions included fatigue, anemia, nausea, thrombocytopenia, shortness of breath, diarrhea, and fever.
Targeted oncology medicine · 2012
Stivarga
Stivarga is the trade name for regorafenib, a Bayer-developed multikinase inhibitor. The FDA approved it in 2012 for previously treated metastatic colorectal cancer and in 2013 for locally advanced, unresectable, or metastatic gastrointestinal stromal tumors after prior imatinib and sunitinib treatment. Under the commercial arrangement with Bayer, Onyx received a royalty on future global oncology sales and jointly promoted the medicine in the United States.
Brand decisions
2013
Accept Amgen acquisition offerM&ABackground
Amgen first proposed to acquire Onyx for $120 per share. Onyx initially rejected the unsolicited offer and explored alternative buyers, but no higher offer materialized.
Action taken
Onyx's board reversed its initial position and agreed to Amgen's original terms.
Aftermath
The transaction, announced in August 2013, ended Onyx's status as an independent publicly traded company and transferred its products and programs to Amgen.
Transaction value. Approximately $10.4 billion (2013)
2011
Establish royalty and promotion arrangement for regorafenibStrategyBackground
Bayer had developed regorafenib, while Onyx sought commercial participation in additional oncology products.
Action taken
Onyx entered an arrangement with Bayer providing a royalty on future global oncology sales of regorafenib and joint U.S. promotion of Stivarga.
Aftermath
Stivarga gained U.S. approvals for metastatic colorectal cancer in 2012 and gastrointestinal stromal tumors in 2013.
2009
Acquire ProteolixM&ABackground
Onyx sought to expand its oncology pipeline and strengthen its position in multiple myeloma through the acquisition of a private biotechnology company.
Action taken
Onyx purchased Proteolix for $276 million in cash plus additional milestone payments.
Aftermath
Proteolix's carfilzomib program became Kyprolis, which received U.S. approval in 2012.
Acquisition consideration. $276 million cash plus additional milestone payments (2009)
Recent events
- 2014
Sorafenib-capecitabine breast cancer trial fails to meet its primary objective[1]
Other
Onyx announced that a Phase III study testing sorafenib with capecitabine in advanced breast cancer did not improve progression-free survival.
- 2013
Stivarga receives gastrointestinal stromal tumor indication[1]
Product generation
The FDA added an indication for regorafenib in patients with locally advanced, unresectable, or metastatic gastrointestinal stromal tumors previously treated with imatinib and sunitinib.
- 2013
Amgen makes an unsolicited acquisition proposal[1]
M&A
Amgen proposed to acquire Onyx for $120 per share. Onyx initially rejected the proposal and explored whether another buyer would offer superior terms.
- 2013
Amgen agrees to acquire Onyx Pharmaceuticals[1]
M&A
After alternative acquisition discussions failed to produce a higher offer, Onyx accepted Amgen's original terms in a transaction valued at approximately $10.4 billion.
- 2012
Kyprolis receives U.S. approval[1]
Product launch
The FDA approved carfilzomib, marketed as Kyprolis, for specified patients with multiple myeloma who had received at least two prior therapies and whose disease had progressed during or shortly after the latest treatment.
- 2012
Stivarga receives first U.S. approval[1]
Product launch
The FDA approved regorafenib, marketed as Stivarga, for previously treated metastatic colorectal cancer.
- 2011
Onyx enters regorafenib royalty and promotion arrangement with Bayer[1]
Other
Onyx and Bayer established an arrangement under which Onyx would receive a royalty on future global oncology sales of regorafenib and jointly promote Stivarga in the United States.
- 2009
Onyx acquires Proteolix[1]
M&A
Onyx acquired privately held biotechnology company Proteolix for $276 million in cash plus additional milestone payments, expanding its oncology pipeline and adding the carfilzomib program.
Sources1 sources
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