Actelion already has an established relationship with CoTherix as both companies focus on therapies to treat PAH - a condition involving high blood pressure in arteries between the heart and lungs that limits physical activities and shortens life - and had previously started negotiations of a potential merger.
California-based CoTherix last year introduced Ventavis, the only US-approved inhaled prostacyclin treatment for the condition, which Actelion estimates will generate sales of more than $100m in 2007.
According to CoTherix, Ventavis represents a non-invasive treatment option that avoids the complications associated with intravenous or subcutaneous prostacyclin delivery, which makes the therapy easier to administer.
"We expect that the transaction will generate immediate substantial value, adding top line revenue and bottom-line cash earnings by leveraging our existing marketing and sales infrastructure in the United States and expanding the reach of Ventavis," said Jean-Paul Clozel, Actelion's chief executive.
"Through the acquisition of CoTherix, Actelion will further lead the drive towards improved PAH therapy, both today with the existing form of Ventavis and potentially tomorrow through improved delivery systems and dry-powder inhalation to further enhance convenience for patients."
Actelion also said that it planned to apply the abilities of its drug development team with those of CoTherix, to accelerate Ventavis' development "in order to support today's trend of combining agents from multiple drug classes to improve treatment outcomes for patients."
The Swiss company has led the drive for improved PAH therapy for quite a while and introduced Tracleer (bosentan) - an oral treatment for the condition - in 2001.
PAH affects approximately 50,000 patients in the United States, with only about 15,000 diagnosed and under treatment.
And a number of drugmakers are competing to introduce their own drug to treat the progressive condition, which severely harms the lungs and cardiovascular system and can lead to severe heart failure.