Orenitram is an extended-release oral formulation of treprostinil that is used to treat patients with pulmonary arterial hypertension (PAH) to improve exercise ability and delay clinical worsening.

This formulation, manufactured by United Therapeutics, was approved by the U.S. Food and Drug Administration (FDA) in December 2013.

How Orenitram works

Treprostinil, the active ingredient of Orenitram, is a synthetic form of a lipid molecule called prostacyclin that binds to prostacyclin receptors present on endothelial cells (which line the inner surface of blood vessels) and platelets. This results in the effective dilation of the arteries in the lungs and other parts of the body and inhibits platelet activation and aggregation.

Orenitram in clinical trials

The FDA’s approval of Orenitram came shortly after positive results from the Phase 3 FREEDOM-M trial (NCT00325403) were released. They showed that patients treated twice-daily with Orenitram showed considerable improvements in the six-minute walk test (6MWT) compared to those who received placebo. The trial also showed that the treatment was well-tolerated in adults. 

Orenitram was then tested in a long-term, uncontrolled, open-label extension study called FREEDOM-EXT (NCT01027949) in 824 patients with PAH.

During this trial, a patient’s average time on Orenitram was two years, with a maximum exposure of six years. The results showed that in the 522 participants who completed the 12-month efficacy assessment, the mean six-minute walk distance improved by 24 meters compared to baseline. The treatment also led to an improvement in overall survival and progression-free survival.

Finally, a 24-week, multicenter, open-label Phase 2 study (NCT01588405) tested the safety and tolerability of transitioning from Remodulin (the injected version of treprostinil) to Orenitram. The trial enrolled 33 WHO Group 1 patients on stable doses of Remodulin. All patients except two transitioned to Orenitram, with 31 patients completing the transition in five days. After 24 weeks of treatment with Orenitram, patients performed well on the 6MWT with no changes in blood flow and heart function.

There are currently two open Phase 3 clinical trials testing Orenitram in patients with PAH.

The first (NCT01560637) is an open-label, long-term study to assess the long-term safety and effects on exercise capacity of the treatment. The trial is currently recruiting participants in many locations worldwide and is expected to be completed in August 2021.

The second trial (NCT01560624) is testing the combination of Orenitram with a background oral monotherapy in an estimated 850 participants compared to placebo. The study is currently recruiting participants in 156 locations worldwide and is expected to be completed in December 2018.

Other information

The most common side effects of Orenitram include headache, nausea, irritation, and diarrhea. Patients with liver or kidney diseases, or pregnant women or those planning to conceive should consult with their doctor before taking Orenitram.


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