Merck has held talks to buy Swiss biotech MoonLake Immunotherapeutics for more than $3 billion, the Financial Times reported on Monday, citing three people familiar with the matter.

MoonLake's shares rose 23.5% in premarket trading on the news.

Merck submitted a nonbinding offer for MoonLake earlier this year, according to the report, which added that the initial approach was rejected but talks could be revived.

Merck's approach for MoonLake ahead of late-stage clinical data for its flagship drug puts the biotech on a strong footing to get sold, the report said.

There was no guarantee a deal would happen and there was a possibility that other buyers would emerge, the FT reported.

Merck and MoonLake did not immediately respond to Reuters requests for comment.

Merck has relied on its best-seller Keytruda to fuel its growth for years, but the drug's patents will begin to expire in 2028. It has also been seeing declining revenue in China from its Gardasil vaccine.