By John Revill and Ludwig Burger
ZURICH/FRANKFURT (Reuters) - Swiss biotech company Actelion <ATLN.S> has turned back to prospective bidder Johnson & Johnson <JNJ.N> for exclusive talks about a "strategic transaction", in an about-turn that appears to sideline rival suitor Sanofi <SASY.PA>.
Actelion said in a brief statement on Wednesday it was in exclusive negotiations with the U.S. healthcare giant but that there could be "no assurance any transaction will result from these discussions", declining to comment further.
J&J confirmed the talks in a separate statement.
The announcement could dash the hopes of French drugmaker Sanofi, which sources have said has been circling Actelion after J&J a little over a week ago said it had ended discussions with Actelion.
Sanofi has been trying to broaden its drug line-up as its key diabetes business comes under pressure.
The French company has signaled it remained keen to make a takeover deal after being trumped in August by Pfizer's <PFE.N> $14 billion bid for U.S. cancer drug company Medivation.
Sanofi declined to comment on Wednesday.
Actelion had a market value of 23.2 billion Swiss francs ($22.6 billion) at Wednesday's closing price of 215 Swiss francs in Switzerland.
U.S. shares in Actelion rose 11 percent after the announcement. J&J shares were down 0.3 percent at 1815 GMT.
Actelion had told J&J before initial talks collapsed last week that it was confident it could attract an offer significantly higher than the approximately 250 Swiss francs per share the U.S. company had offered, one person familiar with the matter said.
There were also disagreements about the proposed deal's structure, the person added at the time.
Actelion co-founder and Chief Executive Jean-Paul Clozel has fended off previous takeover attempts, including a reported takeover approach by Shire <SHP.L> last year and an activist campaign in 2011 by U.S. hedge fund Elliott Advisors.
Acquiring the Swiss biotech firm would boost J&J's drug pipeline and diversify its prospects. J&J's biggest product, the arthritis drug Remicade, faces cheaper competition from Pfizer <PFE.N>.
(additional reporting by Matthias Blamont in Paris)