Pulmonary hypertension
The dual (ETA and ETB) endothelin receptor antagonist bosentan (marketed as Tracleer®) was approved in 2001. Two selective endothelin receptor antagonists (ETA only) are in the final stages of approval: sitaxsentan and ambrisentan. Sildenafil, a selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5), was approved for the treatment of PAH in 2005. It is marketed for PAH as Revatio®. Tadalafil (currently marketed as Cialis® for erectile dysfunction) is currently is Phase III trials. Vasoactive intestinal peptide by inhalation should enter clinical trials for PAH in 2007. PRX-08066 is a serotonin antagonist currently being developed for hypoxic pulmonary hypertension.