US drugmaker Merck & Co, the new parent company of Cubist Pharmaceuticals, has informed employees of plans to eliminate the company's 120-employee drug discovery department.

The job cuts will affect about 20% of Cubist's around 600 employees in the US state of Massachusetts.

New Jersey-based Merck completed the acquisition of Cubist on Jan. 22 for $9.5 billion. A spokesperson for the drugs giant told the Boston Business Journal that the "difficult decision" came as Merck was reviewing its assets, which includes a 450-employee research center in Boston and a Boston-based business development center.

The spokesperson said Merck remains committed to the development of antibiotic drugs, adding that an unspecified number of such products still in pre-clinical testing will continue development in other sites, and that all of Cubist's drugs in clinical trials will continue to be developed.