|Headquarters||South San Francisco California U.S.|
|Key people||N. Anthony (Tony) Coles (CEO)|
Onyx Pharmaceuticals Inc. is a biopharmaceutical company headquartered in South San Francisco, California. The company develops and markets medicines for the treatment of cancer. Onyx was founded in 1992 by Kevin J. Kinsella and Frank McCormick Ph.D., FRS. In 2009, the company acquired Proteolix, Inc., a private biotechnology company. In January 2012, the company was named "the top biotechnology takeover target in 2012" through an industry survey. Onyx CEO Tony Coles has said Onyx likes it prospects as an independent company and is focused on bringing new therapies to patients. However, at the end of August 2013, Amgen announced it was acquiring Onyx in an agreed $10.4 billion deal.
Other backers of Onyx were Avalon Ventures, IVP, J. H. Whitney & Company, and Kleiner Perkins Caufield & Byers. 
Products and development
Sorafenib (co-developed and co-marketed by Bayer and Onyx under the trade name Nexavar), is a drug approved for the treatment of advanced renal cell carcinoma, or advanced kidney cancer, and for the treatment of hepatocellular carcinoma, the most common form of liver cancer. The most common adverse reactions (≥20%), which were considered to be related to sorafenib, are fatigue, weight loss, rash/desquamation, hand-foot skin reaction, alopecia, diarrhea, anorexia, nausea and abdominal pain. Sorafenib is also being evaluated in additional types of cancer, including thyroid and breast cancers.
Carfilzomib (marketed under the trade name Kyprolis) was approved by the FDA on June 20, 2012 for use in patients with multiple myeloma who have received at least two prior therapies, including treatment with bortezomib and an immunomodulatory therapy, and have demonstrated disease progression on or within 60 days of completion of the last therapy.  Carfilzomib is also being evaluated in other stages of multiple myeloma. The most commonly reported adverse reactions (incidence ≥ 30%) are fatigue, anemia, nausea, thrombocytopenia, dyspnea, diarrhea, and pyrexia.
Regorafenib (marketed under the trade name Stivarga), is currently being studied as a potential treatment option in multiple tumor types. On 27 September, 2012, the FDA approved regorafenib for the treatment of patients with metastatic colorectal cancer (CRC) who have been previously treated with fluoropyrimidine-, oxaliplatin, and irinotecan-based chemotherapy, an anti-VEGF therapy, and, if KRAS wild-type, an anti-EGFR therapy. On February 25, 2013, the FDA approved regorafenib in a second indication to treat patients with locally advanced, unresectable or metastatic gastrointestinal stromal tumor (GIST) who have been previously treated with imatinib mesylate and sunitinib malate. Regorafenib is a compound developed by Bayer. The most common adverse reactions (>/=20%) are asthenia/fatigue, HFSR, diarrhea, decreased appetite/food intake, hypertension, mucositis, dysphonia, and infection, pain (not otherwise specified), decreased weight, gastrointestinal and abdominal pain, rash, fever, and nausea. In 2011, Bayer entered into an agreement with Onyx under which Onyx will receive a 20 percent royalty on any future global net sales of regorafenib in oncology. Bayer and Onyx jointly promote Stivarga in the United States.
In June 2013, Amgen Inc offered to buy the shares of Onyx Pharmaceuticals for $120 per share, sending the shares up by around 30% after the news was announced. Onyx announced on June 30, 2013, that it rejected the unsolicited proposal from Amgen. The Onyx board has authorized its financial adviser to contact potential suitors. The acquisition was formally announced on 25 August 2013.
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