Germany's Merck KGaA said on Thursday it is in late-stage talks to acquire U.S.-based SpringWorks Therapeutics for about $3.5 billion, a deal that could give it access to a recently approved rare disease drug and expand its portfolio of experimental cancer treatments.

Merck KGaA is nearing a deal to acquire SpringWorks Therapeutics Inc., people familiar with the matter said. An announcement may come as soon as Monday, the people said, asking not to be identified discussing confidential information.