Amgen Inc. will lay off 274 workers in the Seattle area on Dec. 31 and will exit Washington state by the end of next year, the company announced Thursday. The layoffs by the Thousand Oaks pharmaceutical company are part of a major restructuring plan announced in July that will eliminate 2,400 to 2,900 jobs globally, or up to 15 percent of the company’s workforce. The company operates a small manufacturing plant in Bothell outside of Seattle and other offices in the area employing a total of 660 workers. The remainder of the workers will be laid off through the course of the year. Amgen is seeking to boost its profitability with its restructuring program, but earlier this week billionaire hedge fund manager Dan Loeb said Amgen should consider breaking up into two companies. One would be focused on legacy drugs and the other researching and developing new ones. The company, which will announce its earnings on Monday, said it will update shareholders on its strategic plans at a business review the next day. Shares closed up $3.61, or 2.5 percent, to $147.25 on the Nasdaq.