The FDA has approved United Therapeutics’ twice-daily Orenitram extended-release tablets to increase exercise capacity in WHO Group 1 pulmonary arterial hypertension (PAH) patients. The nod represents the first-ever approval of an orally administered prostacyclin analogue, the drugmaker says.

Approval of the Silver Spring, Md.-based drugmaker’s PAH drug was based on the FREEDOM-M efficacy study of Orenitram (trepsotinil) monotherapy that showed that patients taking the drug were able to walk 23 meters further in six minutes than patients on placebo.

The road to approval, however, was paved with obstacles. United submitted its first NDA Dec. 24, 2011, and received its first complete response letter Oct. 23, 2012.

United resubmitted on Jan. 31, only to receive another complete response letter March 22, questioning the significance of six-minute walk test gains in the FREEDOM-M study.  A second resubmission Aug. 16, along with a large endpoint study, finally led to approval.

The company is launching the drug in the U.S. in about six months. — Lena Freund