Biotech giant Amgen says it will close its facilities in the Seattle region — including its 40-acre waterfront campus on Elliott Bay, inherited with its acquisition of Immunex more than a decade ago.

The closure of the sites in Seattle and Bothell, Wash., was announced by the company this afternoon as part of a broader plan to cut between 2,400 and 2,900 jobs across the company, or about 12 to 15 percent of its global workforce.

About 660 people work in the company’s Seattle facility, an Amgen spokeswoman said. Amgen says in a statement that it’s “actively engaging in discussions with third-parties about potential future use of the facilities.”

The cuts, which will also close Amgen facilities in Colorado, will begin later this year and last through 2015.

Amgen said in its statement, “The talented staff members in Seattle and Bothell have made enormous contributions to advancing biotechnology over the years and the surrounding communities have been very supportive, so it is with great reluctance that we acknowledge the need to leave.”

The company, based in Thousand Oaks, Calif., says in an SEC filing that the cutbacks are the “result of the efforts of a number of teams at the Company conducting an intensive review of its future structure in light of the Company’s anticipated late-stage pipeline developments and expansion into biosimilars.”

Note: Year of Immunex acquisition corrected since original post.