Amgen has about 26,700 staff worldwide following the Horizon acquisition, they said. The company made “changes where we had redundancies in roles or needed to pivot priorities,” she said.

"In Ireland, less than 2% of the combined Amgen/Horizon workforce will receive notification that their role has been identified for consultation. We are not providing numbers for individual locations," the company said.

Announced in December, the Horizon purchase is Amgen’s largest ever and was challenged by the US Federal Trade Commission in May. Amgen was permitted to move forward with the deal after agreeing not to bundle its drugs with two of Horizon’s: Tepezza for thyroid eye disease and Krystexxa for gout.

Last year, Horizon announced plans to expand its operations at its plant in Waterford. The planned facility would expand Horizon’s footprint, adding approximately 320,000 square feet to its current 44,000 square foot drug product (fill-finish) biologics facility, and would create approximately 350 jobs over time.

Asked about the future developments in Waterford, a spokesperson said: "Waterford is now an Amgen site and will become part of the network-wide evaluations that we continually carry out to consider our supply options to ensure reliable and efficient supply for patients. It will take some time to assess this in conjunction with our entire network capabilities and capacity."

Additional reporting Bloomberg