The FDA has approved macitentan (Opsumit), an oral dual endothelin-receptor blocker, to treat pulmonary arterial hypertension (PAH).

Macitentan is the first oral PAH drug approved with an indication to delay disease progression and reduce hospitalization for the disease.

The approval was based on results from the SERAPHIN trial — the first study powered for a hard clinical endpoint instead of just change in functional class or six minute walk distance. A 10-mg dose reduced the composite risk for death, atrial septostomy, lung transplantation, initiation of intravenous or subcutaneous prostanoids or worsening PAH by 45% compared with placebo. PAH hospitalization rates were 19% compared with 32% in the placebo group.

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More modest improvements were observed with a lower, 3-mg dose of macitentan, which was not approved by the FDA. Higher doses of the medication have not been studied and are not currently recommended, according to the label.

Women who are prescribed the  macitentan will need to participate in a Risk Evaluation and Mitigation Strategy (REMS) program, due to the risk for fetal harm. The drug will carry a boxed warning against use in pregnant women like other medications in it’s class, including bosentan (Tracleer) and ambrisentan (Letairis).

Common adverse events associated with macitentan include anemia, nasopharyngitis, sore throat, bronchitis, headache, flu and urinary tract infection.

The drug is expected to be available beginning in November 2013, according to manufacturer Actelion Pharmaceuticals. Earlier this month the FDA approved riociguat, another PAH drug, which belongs to a different drug class.