Switzerland's Actelion Ltd (ATLN.S) said on Tuesday that it was in talks with an undisclosed suitor about a "strategic transaction," even as another potential acquirer, U.S. healthcare company Johnson & Johnson (JNJ.N), ended talks.

The latest twist in Actelion's deal negotiations illustrates how its chief executive Jean-Paul Clozel is driving a hard bargain as bidders circle his company, which he founded in 1997 and turned into Europe's largest biotechnology drug marker.

Actelion did not name the company it was still in discussions with. It informed Johnson & Johnson that it was confident it could attract an offer significantly higher than the approximately 250 Swiss francs per share that the U.S. company had offered, according to a person familiar with the matter that requested anonymity because the negotiations were confidential. There were also disagreements about the structure of the deal, the person added.

Actelion shares ended trading at 208.50 Swiss francs in Zurich on Tuesday before Actelion gave the update on the talks, giving it a market capitalization of 22.5 billion Swiss francs ($22.2 billion).
Acquiring lung disease specialist Actelion would have boosted J&J's drug pipeline and given it more pricing power, at a time when its popular arthritis drug Remicade faces cheaper competition from Pfizer Inc (PFE.N).

Clozel and his wife, Chief Scientific Officer Martine Clozel, have built up a world-leading drug portfolio at Actelion to treat deadly pulmonary arterial hypertension. They aim to expand in drugs for multiple sclerosis and diarrhea-causing clostridium difficile, but regulatory approvals for those are years away.

The company is also counting on its new pulmonary arterial hypertension treatments Opsumit and Uptravi, which combined are forecast to bring in nearly 4.5 billion francs in annual sales by 2020, according to Reuters data.

Analysts have previously identified France's Sanofi (SASY.PA) as a potential buyer for Actelion, whose portfolio would supplement the French drugmaker's Genzyme rare disease unit. Sanofi did not immediately respond to requests for comment.

Ending deal negotiations without a sale would likely subject Clozel to new shareholder pressure. Five years ago, he successfully defended against an effort by activist hedge fund Elliott Management to put Actelion up for sale, questioning his strategy.