Thousand Oaks biopharmaceutical company Amgen Inc. is set to layoff up to 157 employees, according to documents filed with the state.

Last year, the company laid off a small number of workers in June and in 2011 laid off nearly 400 employees. Although it was not made immediately clear what divisions are affected by this round of layoffs, the company previously announced that it would be restructuring some of its R&D division, and that it would include layoffs.

“Like all companies, Amgen adjusts staffing levels to meet the needs of the business,” said Amgen spokeswoman Kristen Davis, in an email. “Approximately half of the staff members notified are based in Thousand Oaks, California, and the rest are field based.”

Davis said the employees who have been notified were offered severance packages that include cash, health insurance benefits and career training.

She did not specify what positions are being eliminated.

The company filed notice of the pending layoffs with the state, as required by Worker Adjustment and Retraining Notification requirements, on Jan. 9 and indicated that the positions will be eliminated effective April 30.

Shares of Amgen were down 84 cents, or less than one percent, to $85.75 in mid-day trading on the Nasdaq.