Thousand Oaks-based biotechnology giant Amgen said Tuesday that it plans to cut 2,400 to 2,900 staff, including at its headquarters location, and will also close facilities in both Washington and Colorado. According to Amgen, the move is part of a restructuring plan to improve its cost structure. As part of the move, Amgen said it will also consolidate staff into less buildings in the Thousand Oaks area. Amgen said the moves would result in an approximately 23 percent reduction in its facilities footprint. Amgen expects to reduce operating expenses by approximately $700M in 2016. Amgen did not say how many of its staff in Thousand Oaks would be cut.