Merck KGaA’s $3.9 billion deal to buy SpringWorks Therapeutics Inc. will expand the German conglomerate’s presence in the US at a time when many companies are seeking to increase investment in the country.

The deal, which has been in the works for months, hands the German pharmaceutical company two approved drugs for rare tumors.

Germany's Merck KGaA has struck a deal to buy U.S. biotech company SpringWorks Therapeutics for an equity value of $3.9 billion to add rare cancer therapies ahead of expected revenue losses linked to expiring patents.