Onyx Pharmaceuticals has agreed to purchase private biotechnology company Proteolix for $276 million in cash, Bloomberg reports. The acquisition will provide Onyx with a late-stage, next-generation therapy to treat multiple myeloma, a form of blood cancer that affects over 180,000 people worldwide. Shares in Onyx rose 5 percent on Monday following the announcement. Under the terms of the agreement, San Francisco-based Proteolix could receive an additional $575 million for achieving certain developmental and regulatory milestones. Out of the $575 million, Proteolix could earn $170 million for accelerated approval from the U.S. Food and Drug Administration. The acquisition expands Onyx's cancer-fighting pipeline into the $16 billion blood cancer market. Onyx, based in Emeryville, Calif., is already partnered with Bayer to market Nexavar for liver and kidney cancer. Proteolix's lead drug candidate, carfilzomib, is a protease inhibitor undergoing Phase IIb clinical trials for patients with relapsed and refractory multiple myeloma. Carfilzomib is also being evaluated as a treatment for solid tumor cancers. According to Onyx, the deal is expected to close in the fourth quarter of 2009. Onyx plans a Phase III study for next year that will combine carfilzomib with dexamethasone and Celgene's Revlimid in patients with relapsed and refractory multiple myeloma. Onyx expects carfilzomib to be approved within 24 to 36 months.