Ambrisentan for pulmonary arterial hypertension.

Endothelin receptor antagonists (ERAs) are an important class of agents used for the treatment of pulmonary arterial hypertension (PAH). Ambrisentan is an oral, once-daily, endothelin type-A receptor (ETA)-selective, propanoic acid class ERA under clinical investigation for the treatment of PAH. In a Phase II study, ambrisentan improved 6-minute walk distance, Borg dyspnea index, World Health Organization Functional Class, and hemodynamics. Ambrisentan was well tolerated and adverse events were not dose related, including a low incidence and severity of liver function test abnormalities. There are no relevant interactions between ambrisentan and cytochrome P450 isoenzymes (metabolism, induction or inhibition) that might alter the activity of P450-metabolized drugs. Potential benefits of ambrisentan include oral, once-daily dosing, ET(A)-receptor selectivity, and the decreased risks of liver toxicity and adverse drug-drug interactions compared with other ERAs.