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.

Merck KGaA (Merck) has moved to strengthen its position in oncology and rare diseases with a $3.9bn agreement to acquire SpringWorks Therapeutics. Under the deal, Merck will pay $47 per share in cash,

Two months after confirming “advanced talks” for a potential merger, Stamford-based SpringWorks Therapeutics Inc. on Monday announced a definitive agreement to be acquired by Germany-based Merck KGaA in a deal valued at about $3.