Merck, the New Jersey-based drug giant, is spending $1 billion on a new Delaware factory to bring production of its best-selling cancer drug Keytruda to the U.S. and speed future drugs to market. Keytruda is currently made in Ireland and by contract manufacturers in the United States.

The Delaware facility will ensure a domestic supply of biologic drugs including the cancer drug Keytruda.

Merck is particularly exposed to the tariff threat, as much of its production of Keytruda takes place at facilities in Ireland and Singapore, in addition to its arrangements with contract manufacturers. Last year, Keytruda generated sales of $29.5 billion, accounting for 46% of the company’s revenue of $64.2 billion.