240 jobs are to go at Roche pharmaceuticals in County Clare.
The company says it will close its operations in Clarecastle on a phased basis between 2018 and 2019.
Roche had announced last November that it was attempting to transfer the plant to a global pharma services company.
However, today Roche says those negotiations have now ended unsuccessfully.
Staff are being notified of the decision this evening.
Local Fine Gael TD Pat Breen says his thoughts are with the workers and their families, saying "the news has come like a bolt out of the blue to all of us in Co Clare".
In a statement, Roche says it "is committed to acting fairly and equitably with all employees and to providing the necessary and appropriate support".
Last year, Roche said the decision to leave the site is due to “underutilisation as a result of the company’s evolving portfolio”.