Merck (MRK) said Tuesday that it has begun construction of $1 billion biologics facility in Wilmington, Delaware.

The laboratory component of the site, which spans 470,000 square feet at the Chestnut Run Innovation & Science Park, is anticipated to be operational by 2028, with investigational compound production beginning in 2030, the company said.

Merck said it plans to produce its immunotherapy drug Keytruda at the facility for US patients.

The company said it plans to invest $3.5 billion in biologics and small molecule manufacturing facilities in the US over the next four years.