We are a biopharmaceutical company dedicated to developing innovative therapies that target the molecular mechanisms that cause cancer. Through our internal research programs and in conjunction with our collaborators, we are applying our expertise to develop and commercialize therapies designed to exploit the genetic and molecular differences between cancer cells and normal cells with the goal of Changing the Way Cancer is Treatedtm. We are focusing on this goal as we continue to maximize current commercialization opportunities for Nexavar® (sorafenib) tablets, along with our collaborator, Bayer HealthCare Pharmaceuticals Inc., or Bayer. In addition, we continue to expand our development pipeline, with several clinical and preclinical stage product candidates.
Our first commercially available product, Nexavar® (sorafenib) tablets, being developed with our collaborator, Bayer HealthCare Pharmaceuticals Inc., or Bayer, is approved by the United States Food and Drug Administration, or FDA, for the treatment of patients with advanced kidney cancer and unresectable liver cancer. Nexavar is a novel, orally available kinase inhibitor and is one of a new class of anticancer treatments that target both cancer cell proliferation and tumor growth through the inhibition of key signaling pathways. In December 2005, Nexavar became the first newly approved drug for patients with advanced kidney cancer in over a decade. In November 2007, Nexavar was approved as the first and is currently the only systemic therapy for the treatment of patients with unresectable liver cancer. Nexavar is now approved in more than 90 countries for the treatment of advanced kidney cancer and in more than 90 countries for the treatment of unresectable liver cancer. We and Bayer are also conducting clinical trials of Nexavar in several important cancer types in addition to advanced kidney cancer and unresectable liver cancer, including lung, thyroid, breast, ovarian and colon cancers.
We and Bayer are commercializing Nexavar, for the treatment of patients with unresectable liver cancer and advanced kidney cancer. Nexavar has been approved and is marketed for these indications in the United States and in the European Union and in other territories worldwide. In the United States, we co-promote Nexavar with Bayer. Outside of the United States, Bayer manages all commercialization activities. In 2009, worldwide net sales of Nexavar as recorded by Bayer were $843.5 million.
In collaboration with Bayer, we initially focused on demonstrating Nexavar’s ability to benefit patients suffering from a cancer for which there were no or few established therapies. With the approval of Nexavar for the treatment of advanced kidney cancer and unresectable liver cancer, the two companies have established the Nexavar brand and created a global commercial oncology presence. In order to benefit as many patients as possible, we and Bayer are investigating the administration of Nexavar with previously approved anticancer therapies in more common cancers, with the objective of enhancing the anti-tumor activity of existing therapies through combination with Nexavar.
We and Bayer are developing and marketing Nexavar under our collaboration and co-promotion agreements. We fund 50% of the development costs for Nexavar worldwide, excluding Japan. With Bayer, we co-promote Nexavar in the United States and share equally in any profits or losses. Outside of the United States, excluding Japan, Bayer has exclusive marketing rights and we share profits equally. In Japan, Bayer funds all product development, and we will receive a royalty on any sales. Our collaboration agreements with Bayer also provided that we receive creditable milestone-based payments totaling $40.0 million, all of which have been received. These payments are repayable by us to Bayer from a portion of our share of any quarterly collaboration profits and royalties after deducting certain contractually agreed upon expenditures. As of December 31, 2009, the entire amount of these development payments was paid back to Bayer based on the profitability of the collaboration thus far.
In November 2009, we made a significant move towards achieving our goal in becoming a multi-product portfolio company by acquiring Proteolix, Inc., or Proteolix, a privately-held biopharmaceutical company located in South San Francisco, California. Proteolix focused primarily on the discovery and development of novel therapies that target the proteasome for the treatment of hematological malignancies, solid tumors and autoimmune disorders. This acquisition, which included carfilzomib, has provided us with an opportunity to expand into the hematological malignancies market. The aggregate cash consideration to former Proteolix stockholders at closing was $276.0 million. In addition, we may be required to pay up to an additional $575.0 million in earnout payments upon the receipt of certain regulatory approvals and the satisfaction of other milestones.
We have expanded our development pipeline through the acquisition of rights to development-stage novel anticancer agents. In November 2008, we entered into an agreement to license worldwide development and commercialization rights to ONX 0801, previously known as BGC 945, from BTG International Limited, or BTG, a London-based specialty pharmaceuticals company. ONX 0801 is in preclinical development and is believed to work by combining two established approaches to improve outcomes for cancer patients, selectively targeting tumor cells through the alpha-folate receptor, which is overexpressed in a number of tumor types, and inhibiting thymidylate synthase, a key enzyme responsible for cell growth and division. In September 2009, we initiated Phase 1 studies of ONX 0801 in advanced solid tumors, triggering a $7.0 million milestone payment to BTG. In December 2008, we acquired options to license SB1518 (designated by Onyx as ONX 0803) and SB1578 (designated by Onyx as ONX 0805), which are both Janus Kinase 2, or JAK2, inhibitors, from S*BIO Pte Ltd, or S*BIO, a Singapore-based company. The activation of JAK2 stimulates blood cell production and the JAK2 pathway is known to play a critical role in the proliferation of certain types of cancer cells and in the anti-inflammatory pathway. S*BIO is conducting trials for ONX 0803 in multiple Phase 1 studies, and in February 2010, S*BIO initiated two Phase 2 trials using ONX 0803 in myelofibrosis. ONX 0805 is currently in preclinical development.
In December 2009, our collaborator, Warner-Lambert Company, now a subsidiary of Pfizer Inc., initiated a Phase 2 clinical trial administering PD 0332991, a small molecule cell cycle inhibitor resulting from our collaboration that targets a cyclin-dependent kinase 4/6, or CDK 4/6. In accordance with our collaboration agreement, we earned a $1.0 million milestone payment due from Pfizer.
With the exception of the years ended December 31, 2009 and 2008, we have incurred net losses since our inception. Our ability to achieve continued and sustainable profitability is uncertain and is dependent on a number of factors. These factors include, but are not limited to, the level of patient demand for Nexavar, the ability of Bayer’s distribution network to process and ship product on a timely basis, investments in sales and marketing efforts to support the sales of Nexavar, Bayer and our investments in the research and development of Nexavar, fluctuations in foreign exchange rates and expenditures we may incur to acquire or develop and commercialize additional products. Our operating results will likely fluctuate from quarter to quarter and from year to year, and are difficult to predict. Since inception, we have relied on public and private financings, combined with milestone payments from our collaborators, to fund our operations and may continue to do so in future periods. As of December 31, 2009, our accumulated deficit was approximately $454.5 million.
Our business is subject to significant risks, including the risks inherent in our development efforts, the results of the Nexavar clinical trials, the marketing of Nexavar as a treatment for patients in approved indications, our dependence on collaborative parties, uncertainties associated with obtaining and enforcing patents, the lengthy and expensive regulatory approval process and competition from other products. We believe our success is dependent on our ability to attract and retain qualified employees. As of December 31, 2009, we had 271 full-time employees, of whom 52 hold Ph.D., M.D. or Pharm.D. degrees. Of our employees, 99 are in research and development, 100 are in operations, sales and marketing and 72 are in finance, administration and corporate development. No employee is represented by a labor union and we believe our employee relations to be good.
We were incorporated in California in February 1992 and reincorporated in Delaware in May 1996. Our corporate headquarters are located at 2100 Powell Street, Emeryville, California 94608, and our telephone number is (510) 597-6500.