French pharmaceutical company Sanofi is in talks with Swiss drugmaker Actelion, but a deal is not imminent, sources confirmed to CNBC on Wednesday.
U.S. shares of Actelion and Sanofi were down 9 percent and 2.5 percent, respectively, on Wednesday.
It's unclear what price Sanofi might pay or what structure is envisioned, but the deal could value Actelion as much as $30 billion, according to The Wall Street Journal, which first reported on the talks and cited people familiar with the matter.
On Tuesday, Johnson & Johnson ended its discussions with Actelion regarding a possible transaction. Actelion told J&J it was confident it could attract a higher offer than the 250 Swiss francs per share the U.S. company had offered, Reuters reported.
In August, Sanofi, eager for deals to broaden its drug lineup, was trumped by Pfizer's $14 billion bid for U.S. cancer drug company Medivation.
—CNBC's David Faber and Reuters contributed reporting to this story.